Food Hydrocolloids, 3-Volume Set 9780367258757, 9780429290329

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Food Hydrocolloids Volume I Editor

Martin Glicksman General Foods Corporation Tarrytown, New York

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DOI: 10.1201/9780429290329

PREFACE To the readers of this book the importance of hydrocolloids to the food industry is self-evident. Most prepared and processed foods depend upon the unique functional properties of these ingredients in order to produce good quality, organoleptically acceptable products. So called natural and many unprocessed foods likewise depend upon naturally occurring hydrocolloid constituents of these foods for their textural and processing attributes. The growth of the food industry and the increasing technological basis upon which this growth is based have led to a tremendous expansion in the field of hydrocolloid technology. Every day new products, new patents, and new developments utilizing gums become available as does the need for current up-to-date knowledge in this field. This book is written from the viewpoint of the scientist and technologist who use these materials and who need a current, comparative, and pragmatic knowledge of the state-of-the-art in this field. It is my hope that this book will meet that need. I’d like to thank each of the contributing authors for their contributions and assistance in this venture and I’d like to thank my many friends in the food industry and at General Foods Corporation for their advice, assistance, and encouragement. My special thanks to Ms. Elly Cohen for her generous help and assistance in proofreading and polishing the chapters written by me and thanks also to Ms. Kathy Kastendieck and Mrs. Margaret Paino for typing sections of this manuscript. Martin Glicksman Valley Cottage, New York September 28, 1980

THE EDITOR Martin Glicksman is a Principal Scientist in the Central Research Department of General Foods Corporation, Tarrytown, New York. For the past 27 years he has been actively involved in applied research and in the development of many new food products. Before joining General Foods he worked for seven years in the pharmaceutical and fine chemical industry as an organic chemist. Mr. Glicksman has acquired an international reputation in the field of hydrocolloid technology, has published many papers, and holds 19 patents in the field. His best known publication is the book Gum Technology in the Food Industry, which is a basic reference book on hydrocolloids in the food processing industry. Mr. Glicksman holds a B.S. degree from City College of New York and M.S. and M.A. degrees from New York University. He is a Fellow of the Institute of Food Technologists and is currently a Counselor of the New York Section of the I.F.T. which has a membership of about 1100 food industry members. He is also editor of the newsletter of the Carbohydrate Division of the national I.F.T.

CONTRIBUTORS Rida A. Ali, Ph.D. Director of Nutritional Research and Development Bristol Myers Company International Division New York, New York Martin Glicksman Principal Scientist General Foods Corporation Tarrytown, New York

David J. Pettitt Executive Director Research and Development KELCO Division of Merck & Co., Inc. San Diego, California

Ralph E. Sand Senior Research Chemist Anderson Clayton Foods Richardson, Texas Paul A. Sandford, Ph.D. Research Fellow KELCO Division of Merck & Co., Inc San Diego, California

Herbert W. Staub, Ph.D. Principal Scientist Nutrition General Foods Corporation Cranbury, New Jersey

Dedicated to the memory of my parents, Morris and Leah Glicksman

TABLE OF CONTENTS I. COMPARATIVE PROPERTIES OF HYDROCOLLOIDS Chapter 1 Background and Classification......................................................................................... 3 M. Glicksman

Chapter 2 Structure and Conformation of Hydrocolloids............................................................... 19 R. Sand Chapter 3 Functional Properties......................................................................................................... 47 M. Glicksman Chapter 4 Gums and Nutrition..........................................................................................................101 R. Ali and H. Staub II. FERMENTATION (BIOSYNTHETIC) GUMS Introduction......................................................................................................................125 M. Glicksman Chapter 5 Xanthan............................................................................................................................127 D. Pettitt

Chapter 6 Curdlan..............................................................................................................................151 M. Glicksman Chapter 7 Dextran.............................................................................................................................. 157 M. Glicksman

Chapter 8 Potentially Important Fermentation Gums..................................................................167 P. Sandford INDEX.............................................................................................................................. 203

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Comparative Properties of Hydrocolloids

DOI: 10.1201/9780429290329-1

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3 Chapter 1

ORIGINS AND CLASSIFICATION OF HYDROCOLLOIDS Martin Glicksman

TABLE OF CONTENTS I.

Background and Terminology................................................................................ 4

II.

Functional Properties.............................................................................................. 6

III.

Structure and Functionality.................................................................................... 6 A. Hydration and Solubilization....................................................................... 7 B. Types of Structures.......................................................................................8 1. Linear Polysaccharides................................................................... 8 2. Branched Polysaccharides............................................................. 10

IV.

Origins of Hydrocolloids........................................................................................ 11 A. Exudates...................................................................................................... 11 B. Extracts........................................................................................................ 11 C. Flours............................................................................................................ 11 D. Fermentation or Biosynthesis.................................................................... 12 E. Chemical Modification.............................................................................. 12 F. Chemical Synthesis...................................................................................... 12

V.

Consumption and Availability.............................................................................. 13

VI.

Food Additive Regulations.................................................................................... 13

References

16

DOI: 10.1201/9780429290329-2

4

Food Hydrocolloids

I. BACKGROUND AND TERMINOLOGY Gums, hydrophilic colloids, hydrocolloids, mucilages, and water-soluble polymers are but a few designations for materials that have the ability to thicken or gel aqueous systems.1'50 These materials were first found in exudates from trees or bushes, extracts from plants or seaweeds, flours from seeds or grains, gummy slimes from fermentation processes, and many other natural products. In more recent times, new and modified gums have been made by the chemical modification and derivatization of many of the natural gums. In addition, some very new gums were developed by complete chemical synthesis to yield new polymers having completely new and novel hydrophilic properties. A contemporary classification of edible gums or hydrocolloids based on origin and derivation is shown in Table 1. The word “gum” itself means, a sticky substance, and is derived from the Egyptian term qemai or kami referring to the exudation of the Acanthus plant.69 The adhesive qualities of these natural materials were known for thousands of years and the use of gums can be traced back to the dawn of history to the time of the caveman. The early caveman expressed his artistic abilities by daubing colored mud on the walls of his cave. To improve the adhesion of the “paint”, natural gum-like materials, such as crushed berries, milkweed sap, blood, eggs, milk, and dandelions were added. Subsequently the term “distemper” was used to refer to the mixture of pigment or color with glue or egg white instead of oil. The Egyptians in the period of 3000 to 2000 B.C. decorated the walls of their homes and temples with paintings executed in distemper. The use of vegetable gums such as gum arabic has continued to the present day in artists’ water colors.68 The ancient Egyptians also used gums as adhesives for the wrappings employed in the ritual embalming of their mummies. In addition to “stickiness” or “adhesiveness”, gums also were known for their thickening and gelling properties as well as for nutritional properties in specific cases. In the Orient, records dating back to the times of Confucius (about 800 to 600 B.C.) show the use of seaweeds and seaweed gums as components of various indigenous food preparations. In the Near East during Biblical times, locust beans (source of locust bean gum) were used for a minimal subsistence diet. St. John, during his wanderings in the wilderness, was reported to have survived on locust beans and to this day it is called St. John’s Bread in many parts of the world. Over the centuries many natural plant exudates were discovered and the word “gum” was applied indiscriminately to all types of exudates; including such materials as chicle, rubber latex, rosin, benzoin, damar, copal, and a host of others. With time, the nomenclature and terminology of these natural products became more and more confusing and it was only in the post World War II period that a serious effort was made by scientists in this field to clarify and adopt a uniform terminology for these materials. Today, based on the works of Smith,40 Montgomery,40 Whistler,19 32 Glicksman,31 38-39 and others, a semblance of uniformity of terminology has been achieved and the current technical literature appears to be following the accepted guidelines. Today, for practical purposes “gums” have been divided into two categories — water soluble and water insoluble. The water-insoluble exudates and polymers include chicle, rubber, rosin, etc., and are now referred to by the overall classification of “resins”. The water-soluble materials are still referred to as “gums”, but this is gradually being replaced by the more scientific designation of “hydrophilic colloid”, preferably contracted to “hydrocolloid”. Gums are not true colloids, but are rather polymers of colloid size (10A to 1000A) which exhibit the colloidal properties of remaining suspended under the influence of gravity, and of not being visible under microscopic examination. In fact, gums or hydrocolloids actually form molecular solutions in most instances.

Table I CLASSIFICATION OF EDIBLE HYDROCOLLOIDS Exudates Arabic Tragacanth Karaya Ghatti

Extracts Seaweed: Agar Alginates Carrageenans Furcellaran Land Plant: Pectin Arabinoglactan Animal: Gelatin

Flours Seed: Guar Locust bean Cereal: Starches Microcrystalline cellulose

Biosynthetic or fermentation Dextran Xanthan Curdlan

Chemical modification

Synthetic

Cellulose Derivatives: Carboxymethylcellulose Methylcellulose Hydroxypropylcellulose Hydroxypropylmethylcel lulose Other Derivatives: Modified starches Low methoxyl pectin Propylene glycol alginate

Polyvinylpyrrolidone (PVP®) Carboxyvinyl polymers (Carbopol®) Polyethylene oxide polymers (Polyox®)

VI

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Food Hydrocolloids

Since most hydrocolloids are polysaccharides, progress towards a systematic nomenclature has produced the significant ending “-an” to designate a substance as a polysaccharide. Thus the generic name for a glucose-derived polysaccharide is “glycan”, for an arabinose polysaccharide, “araban”, and so forth. Common names have also been changed to conform, thus “carrageenin” in the older literature now appears as “carrageenan” in the contemporary literature. Other names, however, which are well established such as “pectin”, “amylopectin”, etc., cannot be changed and will persist in modern terminology.19 32

II. FUNCTIONAL PROPERTIES The utility and importance of hydrocolloids is based upon their functional properties. Hydrocolloids are long-chain polymers that dissolve or disperse in water to give a thickening or viscosity-producing effect. This water-thickening property is common to all gums and is the basic reason for their overall use. The degree of thickening varies between gums, with a few gums giving low viscosities at fairly high concentrations, but most gums giving high viscosities at very low concentrations, usually well below lO Yield stress C>O

French dressing, tomato catsup, fudge sauce Sandwich spread, jelly, marmalade

Proportionality constant b>O

I< S< oo

C=O

Sausage slurry, homogenized peanut butter

Dilatant

Thick solution with suspended particles of irregular shape Nearly saturated or supersaturated suspensions

O< S< I

VI w

54

Food Hydrocolloids

Table 3 COMPARATIVE PROPERTIES OF RHEOLOGICAL FOOD SYSTEMS Time effect

Shear effect

System

Where found

bl) bl) ·=

C 11) C

._.

C ..lo:

....

.S

u

C

·- ·- C

.c .c 1I- ·..J

Newtonian

X

X

Bingham plastic (has yield value) Pseudopl a stic

X

X

Thixotropic Dila1an1 Rheopectic

X

X X

X X X

X

X

Maple syrup, corn syrup, broth and bouillon soups, homogenized and skim milk, carbonated beverages. Chocolate, butter, cheese, icings, spreads. Work-hardened butter, gelled desserts and puddings. Mayonnaise, catsup, sauces. Honey containing dextran impurities. Beating egg white, whipping cream .

major significance, and the relevant colloid properties of the particles that determine their rheological behavior are (1) particle shape, (2) particle size, (3) particle flexibility and ease of deformation, (4) salvation of the particles by the continuous phase, and (5) presence and magnitude of electrical charges on the particles . Non-Newtonian behavior is most frequently pronounced at intermediate shear rates. At extraordinarily high or low shear rates, many non-Newtonian systems approach Newtonian behavior. It has been shown that non-Newtonian flow behavior occurs only when the polymer chains are long enough to entangle. In order for this entanglement to take place, the molecular weight of the polymer must be of a critical value which is not dependent upon shear rate. The effectiveness of entanglement decreases with increasing shear rate. 13 Only five types of non-Newtonian behavior are important to the food industry pseudoplastic, Bingham plastic, dilatant, thixotropic, and rheopectic and are described in Table 3. 1. Bingham Plastic

This system is characterized by an offset, straight-line relationship between shear stress and shear rate, and shows a constant viscosity with a changing rate of shear after the yield value has been exceeded (Figure 2) . An initial resistance must be overcome by a minimum shearing force (yield value) in order to start the flow. Once this yield value is reached, movement is started and the substances act in the same way as Newtonian liquids. As illustrated in Figure 3 the yield value can be pictured as the force required to lift the stationary particles out of their resting formation after which they will flow like Newtonian fluids. At rest, the particles arc held together in a network of agglomerates which break down during the shearing process. Ouring the shearing process the particles arc displaced with respect to one another, and the material starts to flow. Tomato catsup is the best example of a Bingham plastic. It will not flow until the yield value is exceeded as happens when the bottle is tapped.

55

Lifted off

At rest FIGURE 3.

At rest

Structural changes in Bingham plastic system.

Low shear FIGURE 4.

Medium shear

Turbulent flow

Structural changes of pseudoplastic materials.

Shear

FIGURE 5. Pseudoplastic flow. At rest (left), the molecules lie in random arrangement, intertwined and bound to the solvent molecules. Under shear (right), the molecules align and squeeze out the bound water molecules. The viscosity of the system consequently decreases proportional to the increase in rate of shear.

2. Pseudop/astic (Shear-thinning)

A pseudoplastic material flows more readily as it is stirred or sheared (shear-thin­ ning). The viscosity decreases with increasing shear rate, but is not directly propor­ tional. This type of flow indicates that an inner, structural change is taking place. The decrease of viscosity which occurs is the result of the molecular alignment that takes place within the system. There is a close, but not directly proportional, relationship between the shear rate and the shear force, and a change in the former always results in a change of the latter. At a low shear rate, the molecules are disarranged and only partially aligned, resulting in a higher viscosity. As the shear rate is increased, the molecules become oriented and aligned, thus resulting in a decrease of inner friction and indicated as a lower viscosity. This process is reversible inasmuch as the molecules disorient themselves after the shearing force is stopped, and the system returns to its original consistency or viscosity (Figures 4 and 5). Pscudoplastic measurements are reproducible and are dependent only upon rate of shear and temperatures, differing from thixotropic measurements which are dependent upon rate of shear, temperature, and also time. Time does not inflence the measure­ ment of pseudoplastic substances and the process is reversible, since the molecules disorient themselves when the shearing force ceases. Pseudoplastic behavior is very common in many emulsions, and most gum solutions fall into this category.

56

Food Hydrocolloids

SHEAR

FIGURE 6 . Structural changes of dilatant material s. At rest (left), defl occulated material is close-packed. Under shear (right), material expand s resulting in increased resistance to flow .

3. Dilatancy (Shear-Thickening) Dilatant materials show an increasing viscosity - with an increasing rate of shear - and often reach the point where the fluid becomes solid . When at rest, the dilatant system is in a condition where the constituent particles are most closely packed. As shear force is applied and flow commences, the particles in the system separate. The voids between them are enlarged, and immediately filled with the continuous liquid phase. Since this is insufficient to saturate the system, fill the voids, and cover the particles, the viscosity increases rapidly and the system appears to dry out and solidify . Dilatancy can be observed in the behavior of sand at the seashore. If there is just enough water present to cover all the sand particles - and the spaces between them - with water, then the system will flow. However, if the shearing force is suddenly increased by someone stepping on the wet sand, the spaces between the particles of the dispersed phase are enlarged, creating voids which drain the water from adjacent particles. Friction increases because the dispersing medium (water) is not sufficient to cover all the sand particles and fill the voids, and thus the system solidifies . The process is reversible by either removing the force, or adding enough medium of dispersion to fill the voids (Figure 6). Dilatant flow is exhibited by suspensions containing high concentrations of very fine particles that are closely packed by agglomeration or flocculation. 4. Thixotropic Flow Thixotropy , meaning "to change by touch", is formally defined as a "reversible gel-sol-gel transition" and is caused by the building up of a definite structure within the system. The gelled structure - upon shaking or stirring - becomes a sol. When allowed to remain undisturbed , it becomes gelled again . This phenomenon is based on the breaking down of forces that are active between the particles of such a system, and which will reform upon standing. Thioxotropy is characterized by the fact that agitation produces a decrease in viscosity and the original viscosity is only restored after a period of rest. This type of system shows a hysteresis effect in its flow curve (Figure 7) which is obtained by increasing the rate of shear and then, without stopping, decreasing the rate. Thus it can be seen that the viscosity at any particular rate of shear will depend upon the amount of previous shearing it has undergone. The drop in viscosity as the material is subjected to constant shearing is a function of time. Some thixotropic substances show this decrease over a period of days, while others may take only a few seconds, or less, to reach their final value. Thixotrophy, in general, is characterized by the following properties: (I) it accompanies structural change brought about by applying mechanical disturbance to a system; (2) the system recovers its original structure when the disturbance is removed; and (3) the flow curve (shear rate vs. shear stress) of the system shows a hysteresis loop.

57

THIXOTROPIC

FLOW CURVE SHOWING

HYSTERESIS LOOP

/

/

/

w

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DOI: 10.1201/9780429290374

PREFACE This volume of the projected series of the book on food gums and hydrocolloids continues in the same vein as Volume I, i.e., a pragmatic book written to assist the scientist and technologist who need a practical, current reference book on the state-of-the-art in this field. Volume I covered the general background and comparative properties of hydrocolloids and the very important area of fermentation or biosynthetic gums. Volume II continues with coverage of three important categories of gums - the natural plant exudates, the seaweed extracts and the family of cellulose gums. Volume III will cover the plant seed gums, gelatin, pectin, starch, and other pertinent materials. Again I would like to thank each of the contributing authors for their efforts and assistance in this undertaking and I'd like to thank my many friends and associates in the food industry and at General Foods Corporation for their advice, counsel, and encouragement. Thanks to Ms. Elly Cohen for her assistance in proofreading and correcting the rough manuscript and special thanks for Mrs. Margaret Paino and Ms. Kathy Kastendieck for the typing assistance that made this book possible. Valley Cottage, New York June 15, 1982

THE EDITOR Martin Glicksman is a Principal Scientist in the Central Research Department of General Foods Corporation, Tarrytown, New York. For the past 27 years he has been actively involved in applied research and in the development of many new food products. Before joining General Foods he worked for seven years in the pharmaceutical and fine chemical industry as an organic chemist. Mr. Glicksman has acquired an international reputation in the field of hydrocolloid technology, has published many papers, and holds 19 patents in the field. His best known publication is the book Gum Technology in the Food Industry, which is a basic reference book on hydrocolloids in the food processing industry. Mr. Glickman holds a B.S. degree from City College of New York and M.S. and M.A. degrees from New York University. He is a Fellow of the Institute of Food Technologists and is currently a Counselor of the New York Section of the 1.F.T. which has a membership of about 1100 food industry members. He is also editor of the newsletter of the Carbohydrate Division of the national 1.F. T.

CONTRIBUTORS Alan H. King Senior Technical Representative

KELCO

Division of Merck & Co. , Inc . Clark, New Jersey

Martin Glicksman Research Scientist General Foods Corporation Tarrytown, New York

Dedicate d to my grandchil dren, Scott Loren and Eric Warren

FOOD HYDROCOLLOIDS Volume I Section I: Comparative Properties of Hydrocolloids Background and Classification Structure and conformation of Hydrocolloids Functional Properties Gums and Nutrition Section II: Fermentation (Biosynthetic) Gums Introduction Xanthan Curdlan Dextran Potentially Important Fennentation Gums Volume II Section I: Natural Food Exudates Introduction Gum Arabic (Gum Acacia) Gum Ghatti Gum Karaya (Sterculia Gum) Gum Tragacanth Section II: Seaweed Extracts Introduction Red Seaweed Extracts (Agar, Carrageenan, Furcellaran) Brown Seaweed Extracts (Alginates)

TABLE OF CONTENTS I. NATURAL PLANT EXUDATES Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Martin Glicksman Chapter I Gum Arabic (Gum Acacia) . . .... . .. . .. . . ... . . ... . . ... .. . .. . . ... . ... ..... .. .. . . .. . . .... ... 7 Martin Glicksman Chapter 2 Gum Ghatti ... .. .. ... .... . ...... . . ... . . .. . .. . .. . . . . . ........ .. ... .. . ... .... ... . . . .. .... .. 31 Martin Glicksman Chapter 3 Gum Karaya (Sterculia Gum) ...... . .......... . . . ....... .. ........ . .. . ..... ... .. . ..... .. 39 Martin Glicksman Chapter 4 Gum Tragacanth . . . ......... . ........ .. ................ . . . ................... . ........... 49 Martin Glicksman II. SEAWEED EXTRACTS Introduction .. . .. .... .. ... . . . . . .... . . . . ..... .. .. .... . ... . .. . .... . . ...... .... .. ... . ..... .. 63 Martin Glicksman Chapter 5 Red Seaweed Extracts (Agar, Carrageenan, Furcellaran) . ....... . . . . ... . .. . . .. ..... . .. .. 73 Martin Glicksman Chapter 6 Brown Seaweed Extracts (Algmates) . .......... . ....... .. .. . ..... . . .. ........... . ..... . l 15 Alan H. King Index .. . ..... . . . . . .. . .. . ... . ......... ... . . ... . .. . . . ..... . . .. ....... . . . ...... . ... .. ..... . 191

Natural Plant Exudates

DOI: 10.1201/9780429290374-1

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INTRODUCTION Martin Glicksman TABLE OF CONTENTS I

Genesis of Gums .. . .............................. . ............................... 4

II.

Physical Properties .. .............. .. .......... . ............................... ... 4

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

DOI: 10.1201/9780429290374-2

4

Food Hydrocolloids

I. GENESIS OF GUMS Historically, the earliest known gums or hydrocolloids were the natural exudates or secretions from trees and bushes. Knowledge of these materials has surfaced in many of the surviving records dating from the ancient Egyptian dynasties through the biblical era and up to modern times. Today several of these natural gums are still common articles of commerce. A great many plants exude viscous, gummy liquids, which when exposed to air and allowed to dry, form hard, glassy masses. The shapes of these masses vary from spherical, tear-drop balls typical of gum arabic-producing Acacia trees to curved, ribbon-like strands of tragacanth from Astragalus bushes. The colors of these exudates also vary widely from almost clear white to dark brown, depending on the species, climate, soil, and adsorbed impurities. The basis and reason for the formation and exudation of gums by plants is still not understood, and many theories have been formulated to explain these phenomena. One hypothesis suggesting that gum formation is a protective mechanism resulting from a pathological condition is supported by evidence concerning the production of gum arabic. Healthy Acacia trees, grown under favorable conditions of soil and climate, produce little or no gum, while trees grown under adverse conditions of high elevation, excessive heat, and scarcity of moisture produce sizeable quantities of gum arabic. In addition, the yield of gum can be further increased by deliberately injuring the tree by stripping away the bark. Other investigators believe that gum formation is part of the normal physiological metabolism of the plant as in the case of the gums in sugar beets and yeasts. 1 Still others consider gums to be synthesized as a result of an infected section of the plant to prevent further invasion of the tissue. This can be considered similar to the formation of a scab on a human wound. 2 The formation of gum has also been attributed to fungi attacking the plant and releasing enzymes that penetrate the tissues and transform the constituent cellulose materials of the cell wall into gum. This has been suggested to be the mechanism of formation of the gum found in the gummosis disease of various deciduous trees. Yet another theory, particularly with respect to Acacia species, claims the formation of gums to be caused by bacterial action and suggests that specific bacteria are capable of producing different kinds of gum. 1 However, the current theory of gum formation is that it is not a pathological occurrence, but is a result of normal enzymatic behavior of the plant. Recent morphological studies have shown the presence of gum arabic in various cells throughout the Acacia plant as part of the plant's normal growth and development. 3

II. PHYSICAL PROPERTIES The physical appearance and properties of the natural gums are of utmost importance in determining their commercial value and their end use. These vary considerably with gums of different botanical sources, and there are even substantial differences in gum from the same species when collected from plants growing under different climatic conditions or even collected from the same plant at different seasons of the year. The physical properties may also be affected by the age of the exudate, treatment of the gum after collection, such as washing, drying, sun-bleaching, and storage temperatures. Natural gums are exuded in a variety of shapes and forms, the best known being the teardrop or globular shape of various grades of gum arabic. Other characteristic shapes are flakes or thread-like ribbons as with gum tragacanth. Still others resemble stalactites, and after collection and fracturing yield irregular rod-shaped fragments. The surface of most gums is perfectly smooth when fresh but may become rough or covered with small cracks or striations upon weathering, resulting in an opaque appearance.

5

These fissures or striations are often restricted to the surface, but may be deep in some gums, causing the '"tear-drops" to break up into smaller fragments during handling and shipping. The color of gums in their natural exudate shape varies from almost water-white (colorless) through shades of yellow, amber, and orange to dark brown. The best grades of gum arabic are almost colorless with slight traces of yellow. Some gums possess pink, red, or green lines; and some black or brownish gums are also found. Many gums when first secreted appear to be colorless, and it is believed that color is due mainly to the presence of various types of impurities. Color often appears as the gums age upon the tree and may be due to extraneous substances that are washed onto the gum. Bush or grass fires can cause discoloration by scorching. Tannins from the sap or tissues of the parent tree are frequently the cause of discoloration and are believed to account for some of the very dark gums yielded by certain trees. The water-soluble plant gums are usually odorless and in this respect differ markedly from the oil-soluble resinous exudates which have distinctive smells. The gums are usually tasteless and bland, except for some species which have a sweet, carbohydrate taste and some types that have been contaminated. Gums contaminated with tannins usually have a harsh, bitter flavor that is a serious detriment in food applications. Gums vary in hardness, but since this is usually dependent upon the amount of moisture present (12 to 16%), it cannot be used as a means of classification as with minerals. Density is also variable and depends upon the amount of air entrapped when the gum was formed. There are many plant gum exudates known all over the world, but only four are of real importance to the food industry. These are arabic, ghatti, karaya, and tragacanth. Many of the other gums are known and used in local areas where they are available, but only to a very limited extent. These gums have similar properties and can be used for similar applications where necessary. Some of the more common ones are damson, plum, cherry, peach, prune, lemon, almond, cashew, brea, chagual, mesquite, shiraz, cactus, neem, sapote, cholla, khaya, jeol, and others too numerous to mention. For detailed information on these less important gums, the reader is referred to the publications of Whistler,4 Smith and Montgomery, 5 Whistler and Smart, 6 and Howes 1 • In this section only the four important commercial gums will be discussed - arabic, ghatti, karaya, and tragacanth.

REFERENCES I. Howes, F. N., Vegetable Gums and Resins. Chronica Botanica, Waltham, Mass., 1949. 2. Jones, J. K. N. and Smith, F., Plant gums and mucilages. Adv. Carb. Chem., 4, 243, 1949. 3. Vassal, M. J., Gum-bearing Acacias and gummosis, in Gums and Hydrosoluble Natural Vegetal Colloids. 4th Intl. Symposium, lranex S.A., Paris, France, 1976, 61. 4. Whistler, R. L., Industrial Gums, 2nd ed., Academic Press, New York, N.Y., 1973. 5. Smith, F. and Montgomery, R., The Chemistry of Plant Gums and Mucilages, Reinhold, New York, N.Y., 1959. 6. Whistler, R. L. and Smart, C. L.,PolysaccharideChemistry, Academic Press, New York, N.Y., 1953.

Taylor & Francis Taylor & Francis Group

http://taylorandfrancis.com

7

Chapter 1

GUM ARABIC (GUM ACACIA) Martin Glicksman

TABLE OF CONTENTS I.

Background ...... .. ...... . ...... . .. .... ............ ... ..... . .. . ............. . .. .. 8

II.

Manufacture ................... . .................. . ...................... ......... 8 Source ..... . ................... ..... ...................... .. . .. . ......... . 8 A. Collection..... . ................ .... ................... . ....... .. . . ........ 9 B. Availability ...................... ...................... .................. 13 C.

III.

Specifications ..... .. ... . ..... . . .... .... . ....... . . .. ........ . ................. ... 13

IV.

Regulatory Status ...................... ...................... .................... 13

V.

Structure ...................... ...................... ...................... ...... 15

VI.

Properties ................... . ......... .. ...................... .................. 17 Solubility .. . .... .. ............. ... ...................... ................. 17 A. Viscosity ...................... ...................... .................... 17 B. Effect of pH ................... .. ...................... .................. 19 C. Effect of Electrolytes . ..................... .... ............ .. . . .......... 19 D. Emulsifying Properties ...................... ........ . .................... 19 E. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 F.

VII.

Food A. B. C. D. E. F. G.

Applications ......... . ...................... ..................... .. . . ...... 20 Flavor Fixation ...................... ...................... .............. 21 Confectionery .................. . ...................... ................... 22 Beverages............ ..................... . ...................... ........ 23 Bakery Products ...................... ...................... ............. 24 Protective Coatings ...................... ...................... ......... . 24 Dietetic Foods . ...... .. ...................... ...................... ... .. . 25 Miscellaneous .................. . ......... .. .................. ... ........ 25

References ...................... ...................... ...................... ... . ......... 26

DOI: 10.1201/9780429290374-3

8

Food Hydrocolloids

I. BACKGROUND Gum arabic or gum Acacia is the oldest and best known of the natural gums and its use goes back about 5,000 years to the time of the ancient Egyptians. Gum acacia was widely used in the old and traditional Egyptian practice of embalming the dead which began in the Third Dynasty about 2650 B.C. and reached its perfection about 2400 B.C. Herodotus, the Greek historian, on a journey to Egypt in the Fifth Century B.C., was the first to describe the essential procedure: •~There are persons who are appointed as professional embalmers. First they draw out the brains through the nostrils with an iron hook, taking part of it out in this manner, the rest by the infusion of drugs. Then with a sharp Ethiopian stone they make an incision in the side, and take out all the bowels; and having cleansed the abdomen and rinsed it with palm wine, they next sprinkle it with pounded perfumes. Then having filled the belly with pure myrrh pounded, and Cassia, and other perfumes, frankincense excepted, they sew it up again; and when they have done this, they steep it in natron, leaving it under for seventy days; for a longer time than this it is not lawful to steep it. At the expiration of seventy days they wash the corpse, and wrap the whole body in bandages of flaxen cloth, smearing it with gum, which the Egyptians commonly use instead of glue. After this the body is returned to the relations who enclose it in a wooden case in the shape of a man and store it in a sepulchral chamber,.. 111 In modem times gum arabic has found much use in more mundane food and industrial applications where it is used for such things as stabilizing beverage emulsions, encapsulating flavor and perfume oils, forming gum drop confections, etc.

II. MANUFACTURE A. Source Gum arabic is the natural exudate produced by various species of the thorny Acacia trees and is officially defined as '"a dried gummy exudation obtained from the stems and branches of Acacia senegal (L.) Willd. or of related species of Acacia (Fam. Leguminosae). " 2 Over 900 species of Acacia have been botanically identified all over the world. About 500 species are known to grow naturally throughout the Sahelian regions of Africa, forming the '"gum belt'~ extending from east to west continuously from Somalia through Ethiopia, Sudan, Chad, Northern Cameroun, Nigeria, Niger, Upper Volta, Mali, Senegal, and Mauritania (Figure l). Almost all of the world's supply of gum arabic comes from three main production areas in this part of Africa. These are the Republic of the Sudan; the French-speaking west African countries comprising Senegal, Mali, Mauritania, Niger, and Chad; and Nigeria. About 75% of the world's supply is produced by Sudan, most of the rest from Senegal, Mauritania, and Nigeria, and smaller amounts from the remaining countries. 3 A Of the many species of Acacia found, however, only three have been exploited commercially, and form the major sources of gum arabic exudates. These species are Acacia senegal (Acacia verek), Acacia seyal, and Acacia laeta. Anderson' reports that about 80% of commercial gum arabic is derived from Acacia senegal, about 10% from Acacia seyal, and the remaining 10% from Acacia laeta, campylacantha, drepanolobium, plus a few others. About 600 species of Acacia are found in Australia, and many species are also found in India, Central America, and southwest North America. In Australia, four or five species out of the 600 found give better quality gums than the African species; gums that are whiter and cleaner in appearance. In addition, these species of Acacia trees are much less thorny - thus allowing easier, quicker, and less expensive collection of the exudates. The Australian government is interested in the development of Acacia plantations as a potential solution to the social and economic problem of providing suitable employment for their indigenous

9

FIGURE I. · Sahel "gum belt", area of Africa. (Courtesy of Iranex SIA.)

Aborigine population, and are supporting programs to help this industry. Plantations of Acacia trees_are now being started in Australia, but it will be years before the effect of this development will be felt on the gum arabic market.

B. Collection Gum arabic is exuded from the Acacia trees in the form of round spherical balls resembling tear drops (Figure 2) . Damaged trees give larger yields of gum, so it is commonplace for the natives to cut and strip the bark from the trees and then return some days later to remove the tears of gum that form in the scars or wounds. This is extensively a tedious manual operation, and the natives collect the gum by hand (Figure 3)- storing it locally until there is enough to take to market. The crude gum is then taken or sent to the major central market, the city of El Obeid in the Sudan. Here the gum tears are cleaned and sorted by hand (Figure 4), usually into two grades - '"cleaned amber sorts" and '"hand-picked selected". The gum is then packed into 100 kg burlap bags and then exported to distributors and suppliers in all parts of the world, where it is further processed into the form desired for final application. These processes usually comprise further grading or sorting, cleaning, grinding, blending and sometimes spray-drying. For food and pharmaceutical applications, spray-dried gum is preferred. In such cases the gum is dissolved in water, clarified by centrifugation or filtration, heat-treated or pasteurized to kill bacteria, and then spray-dried to a fine, clean powder.

10

Food Hydrocolloids

AGURE 2. Gum arabic exudate on Acacia senegal tree (Courtesy of lrancx SIA).

For centuries the hand collection of wild crops was the traditional method for producing gum arabic. The industry was concentrated in what is now the Republic of the Sudan. The largest central market for gum arabic was in the city of El Obeid, where about 80% of the world's supply was sorted, graded, !l}arketed, and shipped. Most of the rest came from the other west African nations in the same sub-equatorial geographical belt. From 1970 to 1973 a severe drought affected this Sahel region and the production of gum arabic fell drastically. In order to counteract the effects of the drought and to combat the encroachment of the

11

AGURE 3.

Hand collection of gum arabic. (Counesy of Iranex S/A.)

desert on arable land, many development programs were started in all of the African countries in the Sahel belt with the help of the western world and the United Nations. It was found that one of the best ways to stabilize sand dunes and to develop a ground-carpet of vegetation that will retain moisture, fix nitrogen, and improve the soil was by the planting of Acacia trees . Acacias have fibrous root systems that do this most effectively, and many Acacia plantations were started. Programs were started and financed by the RNUD (Program of the United Nations for Development), FAQ, IRDA (Canadian International Research and Development Corp.), European Development Fund, World Bank, and others. Most of the new Acacia plantations were started in the early and mid- l 970s and since it takes 5 to 6 years to establish gum producing trees , it is believed that the 1980s will see a large increase in the amount of gum arabic available from these new plantations. In addition, 1975 and 1976 were good rain years, thus breaking the drought in this area. Normal gum arabic production in the Sudan, not counting the new plantations has been stabilized at the old production figure of about 50,000 ton/year. Also, in the Sudan alone the government development programs sponsored in part by the UNEF (United Nations Emergency Fund) is aimed at doubling this production figure to 100,000 metric tons per year by 1990. At this time a major transition is taking place in the gum arabic industry. It is being transformed from a hunting-type, catch-as-catch-can operation, to a scientifically based farming operation that will result in better, higher quality products as well as a more stable

12 Food Hydrocolloids

C

"' =

-0 C/l

·.;= "' E

~

-0

]

0

u

G:i ;;

~ "'E = 00 00

'o

C

-~ V)

C

-0

"' ::t:

13

and dependable raw material supply. In addition, many other geographic areas are being opened to gum arabic operation, and the Sudanese monopoly will probably be broken within the next few years - creating a freer market and more competitive prices. The quality and yield of this cultivated crop in the Sudan and in Senegal has been continuously improving over the past few years and in 198 l was reported to be approaching a yield of I ton/ha and supplying up to 114 of the commercial gum arabic of the region (Figure 5). C. Availability Total world production of gum arabic averages about 50,000 to 55,000 tons, with a record high of 75,000 tons reached in the peak ye2r of 1963 and a record low of 30,000 tons in the disastrous drought year of I 973. 5 •6 Imports of gum arabic into the U.S. over the past few years have been reported by Phillips et al. 5 and current! y appear to be in the area of 25,000,000 lb/year: 1971 1972 1973 1974 1975 1976 1977 1978

30,000,000 lb 32,000,000 lb 17,000,000 lb 25,000,000 lb 6,000,000 lb 14,000,000 lb 19,000,000 lb 22,000,000 lb (estimated)

III. SPECIFICATIONS Minimum standards for good quality gum arabic have been defined in the U.S. Pharmacopeia XX 8 as follows: 4% total ash (maximum), 0.5% acid-insoluble ash (maximum), and I% water-insoluble residue (maximum). In line with recent efforts to define standards for food grade additives, more rigid specifications have been established for arabic, karaya, and tragacanth, as published in the Food Chemicals Codex III. 2 The FCC specifications for gum arabic are: Arsenic (as As) Ash (total) Ash (acid insoluble) Heavy metals (as Pb) Lead Insoluble matter Loss on drying

Not Not Not Not Not Not Not

more more more more more more more

than than than than than than than

3 ppm (0.0003%) 4%

0.5%

40 ppm (0.004%)

IO ppm (0.001 %) 1% 15%

No presence of starch, dextrin. or tannin by standard tests.

IV. REGULATORY STATUS In line with the overall review of all GRAS food additives, the FDA collected and reviewed the scientific literature9 on Acacia, the data on the teratology, 10 the data on mutagenic tests, 11 and the report of the Select Committee on GRAS substances on the health aspects 12 of gum arabic as a food ingredient. Based on all of this information, gum arabic or Acacia was affirmed to be GRAS as a direct human food ingredient with specific limitations to present levels of use to ensure its continued safe use in foods. 13 Maximum permitted use levels are shown in Table l. 104 In Europe, efforts by the European Economic Community (EEC) to harmonize regulations pertaining to the use of food additives in the various member countries, has spurred con-

14 Food Hydrocolloids

15

Table 1 MAXIMUM USAGE LEVELS PERMITTED FOR GUM ARABIC Food (as served)

Percent

Beverages and beverage bases

2.0

Chewing gum

5.6

Confections and frostings Dairy product analogs Fats and oils Gelatins, puddings, and fillings Hard candy and cough drops Nuts and nut products Snack foods Soft candy

All other food categories

12.4 1.3

1.5 2.5

46.5 8.3 4.0 85.0

1.0

Function Emulsifier and emulsifier salt, flavoring agent and adjuvant, formulation aid, stabilizer and thickener Flavoring agent and adjuvant, formulation aid, humectant, surface-finishing agent Formulation aid, stabilizer and thickener, surfacefinishing agent Formulation aid, stabilizer, and thickener Formulation aid, stabilizer, and thickener Emulsifier and emulsifier salt, formulation aid, stabilizer and thickener Flavoring agent, and adjuvant, formulation aid Formulation aid, surface-finishing agent Emulsifier and emulsifier salt, formulation aid Emulsifier and emulsifier salt, firming agent, flavoring agent and adjuvant, formulation aid, humectant, stabilizer & thickener, surface-finishing agent. Emulsifier & emulsifier salt, flavoring agent and adjuvant, formulation aid, processing aid, stabilizer and thickener, surface-finishing agent, texturizer

(From Food Drug Cosmetic Law Reports, Acacia (gum arabic), #57,914.3, 21CFR 184. 1330, 1980. With permission.)

temporary toxicological retesting of several exudate gums. 94 A long-term study of gum arabic fed to rats at dietary levels up to 20% showed the top dietary dose level of 10% to be a no effect level. Ninety-day studies involving much higher dose-levels in which the rats were fed at a constant daily dietary intake of gum arabic per kg body weight, i.e. the dose level was increased as the young animals gained weight, showed no toxicological effects due to gum arabic.

V. STRUCTURE Since the early I 960s, Anderson and his colleagues at the University of Edinburgh conducted a thorough, systematic, and continuing study of the chemical structure and properties of the various available and important Acacia gums. Many technical papers have been and are being published as these studies progress and detailed analytical data has been published by Anderson et al. on the three major gum arabic producing Acacia species: Acacia senegal, 14~18 Acacia seyal, 19 •20 and Acacia laeta. 21 •22 The differences of chemical composition and physical properties of the various Acacia species gums are quite extensive. 110 The essential analytical parameters which allow good identification and differentiation are: ash content, nitrogen content, methoxyl content, specific rotation, intrinsic viscosity, molecular weight, equivalent weight (uronic acid content), and the balance of the different single sugars constituting the gum. Differences can be quite large depending upon the gum. For example, nitrogen may vary from 0.02 to 1.66%, uronic acid content from 4 to 37%, optical rotation from =-669 to 108°, molecular weight from 47,000 to 3,000,000 and so forth. 23 Comparative data for the important Acacia species was tabulated by Anderson 7 • 110 as shown in Table 2. Gum arabic as found in nature is a mixed calcium, magnesium and potassium salt of a polysaccharidic acid (arabic acid). It is composed of six carbohydrate moieties - galactose, arabinopyranose, arabinofuranose, rhamnose, glucuronic acid, and 4-0-methylglucuronic acid. The presence of any other carbohydrate material indicates that the gum is not pure gum arabic or that it is admixed with other material.

16

Food Hydrocolloids

Table 2 COMPARATIVE ANALYTICAL DATA OF IMPORTANT Acacia SPECIES

Ash,% Nitrogen,% Methoxyl, % Specific rotation, degrees Intrinsic viscosity, melg Molecular weight, Mw x 103 Equivalent weight Uronic acid, %

Acacia senegal

Acacia seyal

Acacia

/aeta

Acacia compylacantha

3.93 0.29 0.25 ~30 13.4 384

2.87 0.14 0.94 +51 12.1 850

3.30 0.65 0.35 ~42 20.7 725

2.92 0.37 0.29 -12 15.8 312

0.43 +78 17.8 950

1100 16

1470 12

1250 14

1900 9

1980 9

Sugar composition after hydrolysis: 4-O-Methylglucuronic acid 1.5 Glucuronic acid 14.5 Galactose 44 Arabinose 27 Rhamnose 13

5.5 6.5 38 46

4

3.5 10.5 44 29 13

Acacia drepanolobium

2.52 I.II

2.5 6.5 38 52

2 7 54 29 8

From Anderson, D. W., Proc. Biochem., 12 (10), 24-25, 29, 1977. With permission.

x

' /3-D-yat6~x

•

+

6 f3-D-Galp3 .. X

3 f3-0-Galp6+-1(3-0-Galp

...1

1 ~

13-D-?alp

6

...

~

~

.

3 1 ,t3 -D-yatp I.-OMe-/3-D-GpA

J

6

6

.

3 /3 -0-ic:f1 ➔ 3!3- 0- Galf1 ➔ 3!3-D-ia lp1 .. 3(3-D-Galp1 ➔ 3j3-D-Gal p1-+3/3-D-~olp- ~

1

/l-J-rip

~

1

X , .. 3fo- D -ia:p ~ (3-0-GpA I.

1

/3 -0-GpA

4

1

1

?1-.-L-Rhaf

o 1.0

-

(1000)

a' 0

2

0

l.-o"'"

3

.,,rf

4

~

5

6

pH

7

8

~

9

i'

10

11

FIGURE 4. Effect of pH on gum tragacanth solutions (upper curve-ribbon; lower curve-flake).

80r------,------,------,-----

72

-------

Surface h!nsion of water ----- -------

-----

... 65t-t------+------t-----+------I E

~ C

0

50 .__ _ _ __._ _ _ _ _.__ _ _ __.__ _ _ __, 0

0.25

0.50

0.75

1.0

Concentration, o/o

FIGURE 5. 0-flake).

Effect of gum tragacanth on surface tension of water (ll.-ribbon;

56

Food Hydrocolloids 55

50

45

40

.... E

~

35

C

0

'

30

~ ~

25

20

15

.........

0.25

0

AGURE 6.

I

0.50 Concentration , "lo

I

0.75

1.0

Effect of gum tragacanth on interfacial tension of O/W mixture

(l>-ribbon; 0-flake).

in oil/water mixtures lowers the interfacial tension between the oil and water surfaces and accounts for its effective functioning as an emulsifying agent (Figure 6). Together with its viscous nature and acid stability gum tragacanth promotes stable emulsions and is known as a very effective emulsifying agent. In general, the flake form (lower viscosity) of tragacanth shows superior results to the ribbon type (higher viscosity). As seen in Figure 6, ribbon tragacanth shows over a 60% reduction of interfacial tension at 0.25% concentration and over a 50% reduction at 1% concentration. Flake tragacanth shows somewhat superior results with over a 66% reduction of interfacial tension at 0.25% concentration and even higher reductions at higher concentrations. 18 This ability of gum tragacanth to reduce interfacial surface tension together with its aqueous thickening properties makes gum tragacanth a very effective, bifunctional emulsifying agent. E. Compatibility Gum tragacanth is compatible with most gum systems and viscosities are usually additive when it is used in mixed gum systems. No known incompatibilities or reactivities are known to exist between gum tragacanth and guar gum, locust bean gum, carboxymethylcellulose, propylene glycol alginate, xanthan, and starch. However, there is an interesting interaction between gum tragacanth and gum arabic. Gum arabic when added to gum tragacanth lowers the viscosity of gum tragacanth and produces emulsions with superior, smooth quality from citrus oil, cod liver oil, linseed oil, and mineral oil. 16

57

Gum tragacanth exhibits some recognized synergistic reactions with other gums. When combined with xanthan or propylene glycol alginate to produce pourable salad dressings, gum tragacanth imparts improved flow and cling characteristics to the emulsions. F. Preservation As with all natural gums, preservatives are necessary in order to maintain long-term shelf stability of gum tragacanth containing solutions and the choice will depend on the finished product and formulation. Glycerol or propylene glycol is an excellent preservative for many emulsions at concentrations of 12 oz/gal. 5 Other effective preservatives are benzoic acid, chlorobutanol, methyl and propyl esters of p-hydroxybenzoic acid. 8

VI. FOOD APPLICATIONS Gum tragacanth has been used in a broad range of applications in foods, pharmaceuticals, cosmetics, and diverse industrial uses. In foods, Stauffer8 has compiled a comprehensive table of tragacanth applications. This table, as shown in Table 2, lists the important food applications and the specific functional attributes of tragacanth utilized in each of these applications. A. Salad Dressings and Sauces Because of its well established properties of relative stability to acidity and heat and its effective emulsifying properties, gum tragacanth is used widely in the preparation of salad dressings, relish sauces, condiments, mayonnaise, and other low pH products. However, in recent years tragacanth has been replaced to a large extent by other acid resistant gums, particularly propylene glycol alginate, cellulose derivatives, and xanthan gum. 19' 22 In such applications, gum tragacanth achieves its stabilizing effect by increasing viscosity and thereby retarding or preventing the movement of solid particles or liquids of differing density. 38 It is only relatively stable however, being adversely affected by heat and acidity, and this factor must be taken into consideration and compensated for when tragacanth is used in the manufacture of these low pH sauce and dressing products. Werbin 23 described the use of gum stabilizers in the preparation of typical French salad dressings which are essentially stabilized oil-in-water emulsions. In recent years low calorie salad dressings have become an important part of the pourable dressings market. These products have low oil contents, usually about I to 5%, and require higher levels of gum (0.5 to 1.2%) to thicken the larger aqueous phase and thus stabilize the emulsion. 5 In some dressings, oil is not used at all, and the mouthfeel and body of oil is simulated by the use of gum tragacanth and other gums. B. Ice Cream Stabilization Gum tragacanth has been effectively used in the past as an ice cream stabilizer giving good body and texture by holding huge quantities of water uniformly distributed as water of hydration. 24 ·25 Potter and Williams 26 in a review of ice cream stabilizers recommended its use at a level of 0.2 to 0.35%. Wegener27 reported that tragacanth is very effective in reaching and maintaining a constant maximum viscosity during ice cream processing. It has also performed satisfactorily as a stabilizer for water ices, ice pops, and sherbets at concentrations of about 0.5%. 28 In ice pops, tragacanth prevents the migration of syrup in the ice matrix during storage. C. Bakery Emulsions, Toppings, and Fillings Gum tragacanth has been used to stabilize bakery emulsions, and fillings containing fruit, fruit purees, and natural fruit flavor extracts because the gum gives a creamy filling with a

58

Food Hydrocolloids

Table 2 FOOD APPLICATIONS OF GUM TRAGACANTH Dairy products Ice cream stabilizer Ice milk Milkshake Sherbert Ice pops and water ices Chocolate milk drinks Aavored milk drinks Puddings Neiifchatel-type process cheese Cheese spread Bakery products Meringues Bakers' citrus oil emulsions Frozen pie fillings Dressings and sauces French dressing Salad dressing Syrups and toppings Relish White sauces and gravies Cocktail, barbecue, and spaghetti sauces Catsup

Beverages Soft drink with fruit pulp Fruit juices and nectars Dry beverage mixes Confections Candy gels and jellies Caramels, nougats, taffy Candy glaze Cough drops and lozenges Gum drops, jujubes, pastilles Dietetic foods French and salad dressings Syrups Puddings Sauces Beverages Spreads (high polyunsaturated) Miscellaneous Whipped toppings Quick cooking cereal

(Adapted from Stauffer, K. R., in Handbook of Water-Soluble Gums and Resins, Davidson, R. L., F.d., McGraw-Hill, New York, 1980, chap. I l.)

good shine and transparency as well as a long shelf life in conjunction with the fruit acids in the product. It has been used to suspend whole fruit in a fruit topping for frozen cheesecake because of its clarity, brilliance, and improved texture in this application. 5 It is effective as a cold process meringue stabilizer where it improved the stability of the topping and increased the shelf life by several hours. 29 In frozen pie fillings, tragacanth in conjunction with starch, thickens well and provides clarity and brilliance. 29 Good quality bakery flavor emulsions were stabilized with tragacanth but superior results were achieved with combinations of tragacanth and arabic. 30: 32 D. Confectionery Because of its effective resistance to hydrolysis by food acids, gum tragacanth has been used in various confectionery applications.33 It has been used as a thickener in candy cream centers containing natural fruit and acid. It has been used as a binder in candy cigarettes and lozenges. When these are prepared by the cold-press process, a small amount of powdered gum binds the powdered sugar together because of the effects of pressing and the slight heat generated by the pressing action. Where an extrusion process is used, it is common practice to mix a thick gum solution with a mass of powdered sugar and then extrude it into wafer sheets. After stamping and drying, the gum remains as a binder. In this application, the gum often requires a plasticizer to prevent extreme brittleness under very low humidity conditions.

59 E. Miscellaneous Ali et al. 34 found gum tragacanth and other colloidal substances to be relatively superior to many commercially used chemicals for the stabilization of vitamin C in aqueous solutions. Perrin 35 patented the use of tragacanth for preserving milk, by dissolving 0.2 to I0g in 1 f of milk, preferably at 60 to 70°C. Frozen fruits, which are often used in ice cream, can be treated with gum tragacanth to improve their texture. Barton 37 reported that the quality of frozen raspberries was improved by adding 0.3 to 4% gum tragacanth to give higher drained weights of the syrup and improved color retention in red and purple raspberries.

REFERENCES I. Food Chemicals Codex III, Tragacanth, National Academy Press, Washington, D. C., 337, 1981. 2. Gentry, H. S., Gum Tragacanth in Iran, Econ. Bot., II, 40-63, 1957. 3. Beach, D. C., History, production and uses of tragacanth, in Natural Plant Hydrocolloids, American Chemical Society, Washington, D. C., 1954, 38-44. 4. Barber, L. A., Gum tragacanth from Iran, Am. Perfumer Essent. Oil Rev., 58, 433, 1951. 5. Meer, G., Meer, W. A., and Gerard, T., Gum tragacanth, in Industrial Gums, 2nd ed., Whistler, R. L., Ed., Academic Press, New York, 1973, 289-299. 6. FDA, GRAS Food Ingredients: Gum Tragacanth, PB 221204, NTIS, U.S. Department of Commerce, Washington, D.C., 1972 7. FDC Law Reports, 21 CFR 184.1351 #57,914.51, 1980. 8. Stauffer, K. R., 1980 Gum tragacanth, in Handbook of Water-Soluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill, New York, 1980, chap. 11. 9. Aspinall G. 0., Gums and mucilages, Adv. Carbohydr. Chem., 24, 333-379, 1969. IO. Aspinall, G. O. and Baillie, J., Gum tragacanth. Part I. Fractionation of the gum and the structure of tragacanthic acid, J. Chem. Soc., 1963, 1702-1714, 1963. II. Aspinall, G. 0. and Baillie, J., Gum trangacanth. Part II. The arabinogalactan, J. Chem. Soc., 1963, 1714-1721, 1963. 12. Gralen, N. and Karrholm, M., The physicochemical properties of solutions of gum tragacanth, J. Colloid Sci., 5(1), 21-36, 1950. 13. Schwarz, T. W., Levy, G., and Kawagoe, H. H., Tragacanth solutions. III. The effect of pH on stability, J. Am. Pharm. Assoc. Sci. Ed., 47, 695-696, 1958. 14. Levy, G. and Schwarz, T. W., Tragacanth solutions. I. The relation of method of preparation to the viscosity and stability, J. Am. Pharm. Assoc. Sci. Ed., 47, 451-454, 1958. 15. Levy, G. and Schwarz, T. W., Tragacanth solutions. II. The determination of thickening capacity and stability, Drug Standards, 26, 153, 1958. 16. Schuppner, H. R., Canadian Patent 797,202,1968. 17. Phillips, G. 0., Pass, G., Jeffries, M., and Morley, R. G., Use and technology of exudate gums from tropical sources, in Gelling and Thickening Agents in Foods, Neukom, H. and Pilnik, W., Eds., ForsterVerlag, Zurich, 1980, 135-161. 18. Stauffer, K. R. and Andon, S. A., Comparison of the functional characteristics of two grades oftragacanth, Food Technol., 4(46), 1975. 19. Burrell, J. R., Pickles and sauces, Food Manuf., 32, 115-118, 1957. 20. Burrell, J. R., Pickles and sauces, Food Manuf., 33, 10-13, 17, 1958. 21. Burrell, J. R., Pickles and sauces, FoodManuf., 35. 14-17, 1960. 22. Tanaka, M. and Fukuda, H., Studies on the texture of salad dressings containing xanthan gum, Can. Inst. Food Sci. Technol. J., 9(3), 130-134, 1976. 23. Werbin, S. J., Practical aspects of viscosities of natural gums, in Physical Functions of Hydrocolloids, American Chemical Society, Washington, D. C., 1960, 5-10.

60

Food Hydrocolloids

24. Josephson, D. V., Dahle, C. D., and Patton, S., A comparison of some ice cream stabilizers, South. Dairy Prod. J., 33(4), 34, 1943. 25. Mack, M. J., Sodium alginate as a stabilizer in manufacturing ice cream, Ice Cream Trade J., 32(11), 3334, 1936. 26. Potter, F. E. and Williams, D. H., Stabilizers and emulsifiers in ice cream, Milk Plant Mon., 39(4), 7678, 1950. 27. Wegener, H., Dependence of viscosity of ice cream mixes containing various stabilizers on heating time, Milchwissenschaft, 9, 123-125, 1954. 28. Sommer, H. H., The Theory and Practice of Ice Cream Making, 5th ed., H. H. Sommer Co., Madison, Wis., 1946. 29. Carlin, G. T., Allsen, L.A., Becker, J. A., Logan, P. P., and Ruffley, J., Jr., Pies- How to make, bake, fill, freeze and serve, Tech. Bull., #121, National Restaurant Assoc., Food and Equipment Research Dept., Chicago, Ill., 1954. 30. Cook, M. and Peterson, H., Natural gums, Drug & Cosmetic Ind., 82, 446, 1958. 31. Werbin, S. J., Recent advances in the field of stabilizers and emulsifiers, South. Dairy Prod. J. 53, 38, 1953. 32. Werbin, S. J., Vegetable gums, Bakers Digest, 24(4), 21-23, 1953. 33. Ferri, C. M., Factors in selecting water-soluble gums, Manuf Confect., 39, 37, 1959. 34. Ali, A., Khan, B., and Ahmad, B., Study of substances inhibiting the aerobic oxidation of ascorbic acid solutions, Pakistan J. Sci. Res .. 6, 58, 1954, (C. A., 49, 3425i.) 35. Perrin, P.H., Preserving milk, French Patent 860,210, 1941. 36. Boyd, E. M., Ed., Gum tragacanth, in Toxicity of Pure Foods, CRC Press, Boca Raton, A., 1973, 4556. 37. Barton R. R., Colloids help improve the quality of frozen raspberries, Food Packer, 34(2), 50, 92, 1953. 38. Schaub, K., Rheological standardization of tragacanth and the evaluation of the emulsifying powers of Acacia, Pharm. ActaHelv., 33, 797-851, 1958.

Seaweed Extracts

DOI: 10.1201/9780429290374-7

Taylor & Francis Taylor & Francis Group

http://taylorandfrancis.com

63 INTRODUCTION Martin Glicksman

TABLE OF CONTENTS I.

Background ..................................................................... 64

II.

Seaweed Cultivation ............................................................ 64

ill.

Business Developments ......................................................... 66

IV.

Chemical Structure .............................................................. 69 A. Common Basic Composition ............................................ 69 B. Sulfate Content .......................................................... 70

References ............................................................................... 71

DOI: 10.1201/9780429290374-8

64

Food Hydrocolloids

I. BACKGROUND Although 15,000 varieties of seaweeds are found along most coastlines of the world in waters of widely varying temperatures and salinity, only 25 species are considered commerci~ly valuable. More than 800,000 tons of dried seaweeds are harvested annually, mostly for food purposes. Seaweeds or algae fall into four major categories, classified according to the predominant color pigments viz. red, brown, blue, and blue-green. Only the red and brown species are important sources of hydrocolloids (Figure 1). The red algae (Rhodophyceae) are the source of several important hydrocolloids - agar, carrageenan, and furcellaran - all polymers of galactose (Figure 2). The brown algae (Phaeophyceae) are the source of alginates - polymers of mannuronic and guluronic acids. The largest and most impressive of the brown algae are commonly referred to by the inclusive term ••kelp'~, a massive plant growing in large masses on the Pacific coast of the United States. The conventional red algae seaweeds used for carrageenan manufacture are found in various parts of the world. Prime growing areas are on the shores of New England through the Maritime provinces of Canada, the Philippine Islands, the coast of Chile, the coasts of Ireland, Norway, and France as well as off-shore areas in Indonesia, Korea, and Mexico. During previous years, difficulties in obtaining supplies of red algae from many of these areas occurred at sporadic intervals. In the early 1970s, the floating seaweed Furcellaria fastigiata disappeared from the sea off Denmark for no known reason. This put a crimp on the production of furcellaran, but since normal kappa-carrageenan was available to take its place effectively, there was no noticeable effect in the marketplace. Off the coast of California, the giant kelp, Macrocystis pyrifera, is harvested regularly as a source for alginates manufactured in two plants on the coast itself. In 1977 long spells of unusually hot weather raised the water temperatures above 72°F damaging large portions of the Southern California kelp beds. This resulted in a poor harvest of less than 134,000 tons of kelp in 1977 as compared to a more typical, but still poor, harvest of 170,000 tons in 1979.

II. SEAWEED CULTIVATION These unpredictable and critical raw material shortages have led to major evolutionary changes in the seaweed industry, which has been exceedingly vulnerable to supply shortages of seaweed. To counter problems of limited, undependable, and expensive sources of supply, a new concept has been introduced into the industry. This is the transformation of the industry from strictly hunting and fishing operations for raw materials to controlled farming operations through aquaculture, both in off-shore ocean waters and in large tanks, and ponds on land. Significant quantities of some red seaweed species are now being grown and used in current commercial operations for the production of carrageenan. 10- 11 Extensive aquaculture projects are underway in Nova Scotia, Canada by both Marine Colloids and Hercules to cultivate the carrageenan-bearing Chondrus crispus seaweed, while in France, CECA (subsidiary of Pierrefitte-Auby S.A.) is conducting controlled cultivation research on the same seaweed species on the coast of Brittany. In the U.S., Kelco is conducting kelp growing studies on the west coast. 12 In Argentina, Soriano S.A. (Buenos Aires) is raising agaryielding red seaweeds. Extensive ventures are also reported to be underway in Japan and in Russia. 9 Two types of farming technology are being developed to expand the supply of seaweed - tank aquaculture and seaweed cultivation farms - both of which have been successfully applied to production of commercial quantities of red seaweed species suitable for the manufacture of carrageenan hydrocolloids.

-----------•"••-,«=

Chlorophyceae

!Omo ,c,..

cyanophyceae

~

... ....-------/ '"l """' /

., ,,,,

-----------.,,,,,,,

[G:~:~~:;Ja

1

~E~~~=:~~=

l

l

Gacrocyst1~

ALGINATES

~igart1na

AGAR

FIGURE I.

Furcellariaceae

Rhodophyceae (Red Algae)

H

--o

~ Z 0

0

/

-o,sr ~o~~-~ OH

2 CH 0H

OH

Mu

OH

/ OH

Kaooa

0

~

~o/

OH

OSo,loto

Nu

HrO~O~ro,, lantbda

~

oso.-

Theta

~0/

x;

FIGURE 2.

oso,-

Structures of basic carrageenan repeating units.

(precursor of kappa), nu (precursor of iota), theta (derivative oflarnbda), and xi. All fractions are composed of galactose residues, sulfated to different degrees and alternately linked 1-3 and 1-4 as shown in Figure 2. Furcellaran production started in Denmark during World War II as a substitute for agar which was not available at the time. The native seaweed, Furcellariafastigiata, is a freefloating plant found in the waters surrounding Denmark and is collected with trawling nets. The extract, furcellaran, is similar to kappa-carrageenan in functional properties and has found substantial use in food applications.

B. Regulatory Status 1. Standards a. Carrageenan Carrageenan is officially defined in Food Chemicals Codex III, 76 as the product '"obtained by extraction with water or aqueous alkali from certain members of the class Rhodophyceae (red seaweeds). It is a hydrocolloid consisting mainly of the potassium, sodium, magnesium, calcium, and ammonium sulfate esters of galactose and 3,6-anhydrogalactose copolymers. These hexoses are alternately linked a:-1,3 and 13-1,4 in the polymer. The relative proportion of cations existing in carrageenan may be changed during processing to the extent that one may become predominant. The prevalent copolymers in the hydrocolloid are designated kappa-, iota-, and lambdacarrageenan. Kappa-carrageenan is mostly the alternating polymer of o-galactose-4-sulfate and 3,6-anhydro-o-galactose; iota-carrageenan is similar, except that the 3,6-anhydrogalactose is sulfated at carbon 2. Between kappa-carrageenan and iota-carrageenan there is a continuum of intermediate compositions differing in degree of sulfation at carbon 2. In lambda-carrageenan, the alternating monomeric units are mostly D-galactose-2-sulfate (1,3linked) and D-galactose-2,6-disulfate (1 ,4-linked).

85 Table 2 COMMERCIAL SEAWEED SOURCES OF CARRAGEENAN U.S. (Maine), Canada (Nova Scotia and Prince Edward Island) Korea U.S. (Washington), Chile Mexico Chile France, Spain Morocco Morocco Indonesia, Philippines Philippines Philippines U.S. (Florida) Senegal, Brazil

Chondrus crispus Chondrus oscellatus Gigartina radula Gigartina canaliculata Gigartina chamissoi Gigartina stellata Gigartina acicularis Gigartina pistillata Eucheuma spinosum Eucheuma gelatinae Eucheuma cottonii Eucheuma isiforme Hypnea musciformis

The ester sulfate content of carrageenan ranges from 18% to 40%. In addition, it contains inorganic salts that originates from the seaweed and the process of recovery from the extract. Carrageenan is recovered by alcohol precipitation, by drum drying, or by freezing. The alcohols used during recovery and purification are restricted to methanol, ethanol, and isopropanol. When carrageenan is recovered by drum or roll drying, it may contain monoand di-glycerides or up to 5% polysorbate 80 used as roll-stripping agents. 76 The seaweeds used for carrageenan production belong to the Gigartinaceae and Solieriaceae families of the Rhodophyceae (red seaweed) class. Seaweed species used for this purpose are C. crispus, C. ocellatus, E. cottonii, E. spinosum, Gigartina acicularis, G. pistillata, G. radula and G. stellata. 76 The types and location of carrageenan-bearing seaweeds used world-wide are listed in Table 2. Physical specifications for carrageenan are defined in FCC III as follows: 76 Arsenic (as As) Ash (acid-Insoluble) Ash (total) Heavy metals (as Pb) Lead Loss on drying Sulfate Viscosity of a 1.5% solution

Not more than 3 ppm (0.0003%) Not more than 1.0% Not more than 35.0% Not more than 40 ppm (0.004%) Not more than 10 ppm (0.001%) Not more than 12% Between 18% and 40% on the dry weight basis Not less than 5 centipoises at 75°

Infrared absorption spectra can be obtained on the gelling and non-gelling fractions of carrageenan following the procedure described in FCC III76 and used to identify or characterize carrageenan. Carrageenan has strong, broad absorption bands, typical of all polysaccharides, in the 1000 to I 100 cm"" 1 region. Absorption maxima are 1065 and 1020 cm"" 1 for gelling and non-gelling types, respectively. Other characteristic absorption bands and their intensities relative to the absorbance at I 050 cm=- 1 are as follows: Wave number (cm=- 1)

1220-1260 928-933 840-850 82~30 810-820 800-805

Absorbance relative to 1050 cm~' Molecular assignment

Ester sulfate 3,6-Anhydrogalactose Galactose-4-sulfate Galactose-2-sulfate Galactose-6-sulfate 3 ,6-Anhydrogalactose-2sulfate

Kappa

Iota

0.7-1.2 0.3--0.6 0.3--0.5

1.2-1.6 0.2--0.4 0.2--0.4

0-0.2

0.2--0.4

Lambda 1.4-2.0 0-0.2 0.2--0.4 0.1--0.3

86

Food Hydrocolloids

b. Furcellaran Furcellaran is defined as the refined hydrocolloid prepared by aqueous extraction of Furcellariafastigiata of the Rhodophyceae (red seaweed) class. It is a sulfated polysaccharide, the dominant hexose units of which are galactose and anhydrogalactose. It has a sulfate content of 8 to 19% on a dry weight basis and is associated with ammonium, calcium, potassium, or sodium cations or mixtures thereof. 87 Furcellaran is currently considered to be a type of kappa-carrageenan. 2. FDA Status In line with the overall review of all GRAS food additives, the FDA collected and reviewed the available scientific literature on carrageenan as a food ingredient88 · 186 and sponsored teratologic tests on sodium carrageenan89 and calcium carrageenan. 90 Other feeding tests are still underway. To date no adverse results have been reported and carrageenan has been approved as a regulated additive. 84 ·91 The FDA has proposed a food additive regulation for carrageenan requiring a minimum viscosity specification to represent an average molecular weight exceeding 100,000,92 but since all food grade carrageenans exceed this value, it would not be very meaningful. Typical food grade carrageenans have molecular weights in the 100,000 to 500,000 range. 1 Carrageenan, 97 ·98 furcellaran, 87 and the salts thereof, are classified GRAS to be used at GMP levels (Good Manufacturing Practice) the quantity of a substance added to food not to exceed the amount reasonably required to accomplish its intended effect. These carrageenan97 ·98 and furcellaran 87 additives may be used in the amount necessary for an emulsifier, stabilizer, or thickener in foods, except for those standardized foods that do not provide for such use.

C. Production 1. Availability

The total world production of carrageenan is estimated to be in the neighborhtod of 20,000,000 lb with about one-half being produced in the U.S. The largest and sole American producer, Marine Colloids (Division of FMC Corp.), manufactures an estimated 8 to 9 million lb at its processing plant in Rockland, Maine. In Europe, the second and third largest processors, C .E. C. A. SI A (subsidiary of PierrefitteAuby) in France and Copenhagen Pectin Factory (Hercules subsidiary) in Denmark each manufacture about 4,000,000 lb of carrageenan annually. Some smaller quantities are produced by other independent enterprises in Spain, Portugal, Japan, Korea, Argentina, and North Africa. Japan is reported to produce about 600,000 lb of carageenan annually. Furcellaran is manufactured solely in Denmark by one major manufacturer, Litex Co. (Marine Colloids), which operates three small plants. The amount produced in 1976 has been estimated to be about 3.5 to 4.0 million lb, some of it probably being carrageenan. The raw material, F. fastigiata, was in short supply during the early 1970s and much of the commercial furcellaran in world commerce was, and probably still is, blends of furcellaran and carrageenan. For most applications this is not a problem since their properties are so similar. 2. Harvesting and Manufacture The harvesting of carrageenan-bearing seaweeds still uses a traditional, manual type of operation. Much of the raw material is harvested by workers in boats using special rakes to scrape the seaweeds from their attachments to rocks, ocean floor, etc. Considerable amounts are also obtained as drift weed cast upon the beaches following storms and other violent weather changes. Today tank cultivation and ocean farming are also beginning to contribute

87

FIGURE 3.

Harvesting Chondrus crispus for carrageenan production.

FIGURE 4.

Weighing dried seaweed for baling and shipping.

commercial quantities of seaweeds for processing. 10• 14 In Canada, the cultivation and development of improved seaweed sources for carrageenan manufacture has been extensively supported by the Canadian government 106 (Figures 3 and 4). After harvesting, the seaweeds are either sun-dried or mechanically dried, then baled and shipped to the processing plant. After washing to remove sand, dirt, and extraneous material, the seaweed is macerated and extracted in a hot alkaline solution. The amount of alkali, the temperature, and the time of cooking controls the amount of 3,6-anhydro-o-galactose that will be produced. After this alkaline cook the seaweed can be processed in any of the three ways shown in Figure 5. The best quality carrageenans are obtained via the alcohol precipitation method. Pretreatment of the seaweed with inorganic acid, prior to extraction with hot alkali , gives improved yields of higher gel strength material. 93 The hot extract is then filtered using diatomaceous earth, and sometimes with activated charcoal for decolorization, through a filter-press . The filtrate may be cooked with acid to produce degraded, low viscosity carrageenans specifically suited for certain suspending or stabilizing applications. 101 Reduced viscosity carrageenan and furcellaran made by hydrolytic degradation of the seaweed extracts provides more suitable suspending and stabilizing properties for use in chocolate milk and with preferred gelling properties for low-calorie jellies. 101 Conventionally, however, a 1.5% filtrate is then usually evaporated to a 2.5 to 3.0% carrageenan concentration and the product

88

Food Hydrocolloids

-

Washing

WeedWaah

-

l

Sun or Oven Drying

-

Grinding Blending Standardization

Method 1

Alkaline Cook

-

Filtration

I Concentration

l Alcohol Precipitation

FIGURE 5.

Method 2

Method 3

Orum Drying

Vacuum Drying

-

Grinding Blending Standardization

-

Grinding Blending Standardization

l

Processes for commercial production of carrageenan.

is recovered either by alcohol precipitation or by drum-drying. The resultant product is then ground to a fine mesh powder. Furcellaran is processed in a similar fashion up to filtration and vacuum concentration of the clear extract. At this point, the extract is sprayed into a cold 1.0 to 1.5% potassium chloride solution and precipitated as gelled threads. These threads are then frozen and thawed (similar to agar processing), then pressed to a fibrous mass, dried and ground to form commercial furcellaran. It is primarily potassium furcellaran. 94 D. Structure The carrageenans differ from one another in their content of 3,6-anhydro-o-galactose and the number and position of ester sulfate groups. The three major carrageenans are the kappa-, lambda-, and iota--carrageenans. The kappa- and iota-carrageenans have inferred precursors, mu-carrageenan and nu-carrageenan respectively, while lambda-carrageenan is itself a precursor of theta-carrageenan. Xi-carrageenan is sometimes found instead of thetacarrageenan but its structure has not yet been fully elucidated (See Figure 2). All carrageenans have the common structural feature of a linear polysaccharide built up of alternating 1,3-linked f3-o-galactopyranosyl and I ,4-linked a---o-galactopyranosyl units as shown in Figure 5 in the Introduction. The 1,3-linked segments occur as the 2-sulfate and 4-sulfate or occasonally non-sulfated. The I ,4-linked segments occur as the 2-sulfate and 6-sulfate, the 2,6-disulfate, the 3,6-anhydride, and the 3,6-anhydride-2-sulfate. 85 Sulfation at C3 never appears to occur. Although the number of theoretical structural variations is enormous, only a small number of these permutations are found in nature, (only three of which are commercially important. In summary, it can be said that the various types of carrageenan differ chemically in the following ways: I. 2. 3. 4.

Degree and manner of sulfation Presence of a proportion of 3,6-anhydrogalactose residues linked 1-4 Differing pyranose ring conformations (Reeves Cl or lC) Different cations associated with the sulfate groups.

89 Physically, hydrodynamic and light-scattering measurements suggest that kappa-carrageenan and iota-carrageenan can be best described as an expanded coil composed of multistranded fiber-like threads, each thread having a thickness of about 2nm. 95 •96 Lambda-carrageenan does not have this type of structure. In reactions with milk components such as kappa-casein this type of structure allows the kappa-casein to become adsorbed on the carrageenan chain and thus stabilizes the colloidal milk system. 95 I. Kappa-Carrageenan Kappa-carrageenan is composed of alternating 1,3-linked galactose-4-sulfate and 1,4linked 3,6-anhydro-o-galactose units. This is formed in the seaweed by the enzymatic action of dekinkase 86 upon the precursor mu-carrageenan which removes the sulfate at C6 in the 1,4-linked galactose-6-slllfate with concomitant ring closure to form the 3,6-anhydride. Commercially this can be done during the extraction process using a borohydride treatment under alkaline conditions. 99- 100 The theoretical maximum content of 3,6-anhydro-o-galactose is 35%, but this is never found in nature. Amounts up to 28% are present in kappa-carrageenan from C. crispus but this can be increased by appropriate processing conditions to the near theoretical limit. 101 Functionally, an increase in anhydride content increases the potassium sensitivity and gelling capacity. Kappa types of carrageenan exhibit greater potassium than calcium sensitivity. Typical food grade kappa-carrageenans have an ester sulfate content of about 25% and a 3,6-anhydro-o-galactose content close to the theoretical maximum of 35%.

2. lota-Carrageenan Jota--carrageenan polymer is composed of alternating 1,3-linked o-galactose-4-sulfate and 1,4-linked 3,6-anhydro-o-galactose-2-slllfate units theoretically formed from the precursor nu-carrageenan which contains no anhydride but 6-sulfate in the 1,4-linked galactoside. By eliminating sulfate at the C6 position, the ring is closed to form the 3,6-anhydrogalactose ring and forms iota-carrageenan. 25 ·83 The major difference between kappa- and iota-carrageenan is the amount of 2-sulfate on the 1,4-linked 3,6-anhydro-o-galactose. This effects the potassium sensitivity. As the amount of 2-sulfate increases to as high as 25 to 50%, the potassium sensitivity decreases, as shown by noticeable weakening of the gelling properties. When 80% of the C2 positions are sulfated, calcium sensitivity becomes predominant and the properties become typical of the iotacarrageenan and it is appropriate to consider it an iota-carrageenan in functional performance. 1 3. Lambda-Carrageenan Lambda-carrageenan, the non-gelling carrageenan, is mainly composed of alternating units of 1,3-linked galactose and 1,4 -linked galactose-6-sulfate. The 1,3-linked galactose units differ from kappa and iota in not being sulfated at C4 but are about 70% sulfated at C2 • 102 Under strong alkaline conditions of extraction, the 1,4-linked galactose-6-sulfate gives up the 6-sulfate to form the 3,6-anhydro-o-galactose. Loss of all the 6-sulfate yields thetacarrageenan, which has essentially the same properties as lambda-carrageenan and is therefore not isolated as a separate entity commercially. Xi-carrageenan, which is present instead of lambda-carrageenan, in some species of Gigartina (G. chamissoi and G. canaliculata) has not been completely characterized but appears to differ from lambda-carrageenan in that the 1,3-linked units are completely sulfated at C2 while at least some of the 1,4-linked units are unsubstituted at C 6 • 84 4. Furcellaran Furcellaran in early studies was found to be composed of about 46 to 53% o-galactose, 30 to 33% 3,6-anhydro-o-galactose, 16 to 20% ester sulfate, and a trace of xylose in an approximate molar ratio of 1.5: I. 0:0. 7. 94 · 103 · 104 Also identified as components of furcellaran

90

Food Hydrocolloids

are o--galactose-2-sulfate, o--galactose-4-sulfate, o-galactose-6-sulfate, and 3,6-anhydro-ogalactose-2-sulfate. 105 It is believed that some branching may be present with some substitution at both C3 and C6 in the chain. 103 The distribution of sulfate along the molecular chain is not yet known. Furcellaran differs from kappa-carrageenan mainly in the amount of ester sulfate present. Furcellaran contains one sulfate group per three to four monomer units, whereas kappacarrageenan contains about one sulfate per two monomer units. Furcellaran also has less 4sulfate on the 1,3-linked galactose-4-sulfate than kappa-carrageenan. Although there is only a minor structural difference between kappa-carrageenan and furcellaran, there is a distinct difference in some of the chemical and physical properties. Precipitation of furcellaran with potassium chloride occurs at much lower concentrations than precipitation of carrageenan. Also the texture of milk gels using furcellaran is somewhat Jess brittle and smoother than similar carrageenan gels.

E. Properties J. Solubility

a. Water All of the carrageenans and furcellaran are soluble in hot water, typically at temperatures above 70°C. In cold water only lambda-carrageenan and the sodium salts of kappa- and iota-carrageenan are soluble. The salts of potassium and calcium exhibit various degrees of swelling on hydration. b. Milk All carrageenans and furcellaran are soluble in hot milk but some are strongly affected by the calcium ions present. On cooling all of these solutions tend to gel, the strength and consistency depending on the concentration and sensitivity of the material to calcium ions. Lambda-carrageenan, which is insensitive to potassium and calcium ions, is soluble in hot or cold milk, producing an effective degree of thickening. Kappa- and iota-carrageenan, as well as furcellaran, are insoluble in cold milk, but can be used to thicken and gel cold milk if used together with a phosphate such as tetrasodium pyrophosphate. This is the basis for many cold preparation milk puddings.

c. Effect of Sugar Kappa- and lambda-carrageenan are readily soluble in a hot, aqueous 65% sucrose solution, while iota-carrageenan is only sparingly soluble. d. Effect of Salts Iota- and lambda-carrageenan are soluble in high salt solutions (20 to 25% sodium chloride) while kappa-carrageenan is precipitated by them. The gel strength and gelling temperature of kappa-carrageenan is affected by the type of cations present. 108 Comparative properties of the three major types of carrageenan are shown in Table 3.

2. Gelation Kappa- and iota-carrageenans and furcellaran form thermally-reversible gels upon heating and cooling of aqueous solutions. The theoretical basis for this phenomenon has been explained by Rees 25 as being due to the formation of a double helix structure by the carrageenan polymers (Figure 6). At temperatures above the melting point of the gel, carrageenan polymers exist in solution as random coils. On cooling, a three-dimensional polymer network builds up in which double helices form the junction points of the polymer chains (Gel I). Further cooling leads to aggregation of these junction points to build a three-dimensional gel structure (Gel II). 25

91 Table 3

COMPARATIVE PROPERTIES OF CARRAGEENANS Kappa

Ester sulfate (ca) 3,6-Anhydro-D-galactose Solubility Hot water Cold water

Iota

Lambda

25-30% 28-35%

28-35% 0%

32-39% 30%

Soluble above 70°C Na • salt soluble. Low to high swelling of K Ca • +, and NH; salt

Soluble All salt soluble

Hot milk Cold milk

Soluble Insoluble

Soluble above 70'C Na + salt soluble Ca+ + salt gives thixotropic dispersions Soluble Insoluble

Cold milk (plus TSPP)

Thickens or gels

Thickens or gels

Soluble hot

Difficulty soluble

Soluble Disperses with thickening Increased thickening or gelling Soluble hot

Insoluble cold & hot

Soluble hot

Soluble hot

Insoluble

Insoluble

Insoluble

Gels most strongly with K + Brittle with syneresis

Gels most strongly with ca ++ Elastic with no syneresis None

Non-gelling

None

Stable Accelerated by heat

Stable Hydrolyzes

+ ,

Concentrated sugar solutions Concentrated salt solutions Organic solvents Gelation Effect of cations Type of gel Locust bean gum effect Stability Neutral and alkaline pH Acid (pH 3.5)

Synergistic Stable Solution hydrolyzes Gelled state stable

Non-gelling

Gel.I

FIGURE 6. Proposed gelation mechanism for carrageenans. (From Rees, D. A., Adv. Carbohydr. Chem. Biochem. , 24, 267-332, 1969. With permission .)

92

Food Hydrocolloids

The presence of kinks in the chain, as well as the number, type, and position of sulfate groups have important effects on the gelling properties. Kinks in the chain have an inhibiting effect on the formation and aggregation of double helices and thus a lowering of gel strength. Sulfation effects the gelling properties due to the stereochemical positioning of the sulfate units. Sulfate on C2 of the 1,3-linked galactose units in lambda-carrageenan acts as a wedge to prevent formation of the double helix and thus no gelation results. Sulfate on C2 of the 3,6-anhydro-o-galacose units in iota-carrageenan as well as sulfate on C4 of the 1,3-linked galactose in kappa- and iota-carrageenan all project outward and thus do not interfere with double helix formation (and gelation). Sulfation on C6 of the I ,4-linked 3,6-anhydro-o-galactose forms kinks in the chains which inhibit double helix formation. Elimination of this sulfate by closure of the ring to form the 3,6-anhydride straightens out the polymer chain resulting in enhanced gel potential due to increased ability to form a double helix. Kappa-carrageenan and iota-carrageenan will only gel in the presence of certain cations, the reasons for which are still not understood. Kappa-earrageenan is potassium ion sensitive and produces strong gels with potassium salts. Pure potassium kappa-carrageenan produces a somewhat elastic gel, but in practice, some calcium is always present in the commercial product resulting in a brittle gel subject to syneresis caused by a typical shrinkage of the gel. Furcellaran behaves like kappacarrageenan and forms similar type gels in the presence of potassium cations. Kappa-carrageenan also shows an unusual synergism with locust bean gum in aqueous gel systems which is marked by an enhancement of the gel strength, a change in gel texture from brittle to elastic, and a reduction in the degree of syneresis. This synergistic effect is most noticeable with kappa-carrageenans of high 3,6-anhydro-o-galactose content and with an ester sulfate content of 20 to 25%. This phenomenon may be caused by a carrageenanlocust bean gum polymer interaction similar to that of xanthan-locust bean gum (see Chapter 5). None of the other carrageenans or furcellaran exhibit this synergism. /ota-carrageenan reacts strongly in the presence of calcium cations to form tender, elastic gels not subject to syneresis. These are similar to gelatin gels but have higher gelling and melting temperatures and do not require refrigeration to gel or to remain gelled. /otacarrageenan will also form gels with potassium or ammonium ions but these are much weaker than those made with calcium ions. 3. Effect ofpH The carrageenans are quite stable at pHs of seven or higher, but at lower pHs their stability decreases, especially at elevated temperatures. As the pH is lowered hydrolysis of the carrageenan polymer occurs with a resultant loss of viscosity and gelling capability. However, in practical applications, once the gel is formed, even at low pH, hydrolysis no longer occurs so that the gel is then stable. 4. Protein Reactivity Protein reactivity is exhibited by all sulfated polysaccharides. Inasmuch as a sulfated polysaccharide is a negatively charged polymer over a wide range of pH, it is capable of forming complexes with a positively charged polymer such as a protein molecule. The mechanism by which this interaction takes place is illustrated in Figure 7 . 1· 122 Above the isoelectric point of the protein, any polyvalent metal ions present act as bridges between the negatively charged carboxyl groups on the protein and the negatively charged ester sulfates of the polysaccharide. At a pH below the isoelectric point of the protein, similar electrostatic interactions take place between the ester sulfate of the polysaccharide and the positively charged amino groups on the protein. Intermediate or transitional degrees of association are also found at pH values between these two points.

93

I

NHz

Protein

I

~Oi'

I

NHa

I

~Oi

I

NH1

I I I I I coNH1 coNH1 co. I . I . I

ca2+

ca 2 +

ca 2 +

Ca 2 +

so;

so.;

so-

ca

so.;

so;

I

I

.

l •

.

I

Corrogeenon

2•

I

I Protein

COi

so; I

so-

l

4

so-

l

so-

l

4

4

so-

l

4

Corrogeenon

lI

Protein

~coNH.t ' • •

-,.-..--..--..--...---1 I I I I I co; ~Hl COatf t_Ot; CO.H Ntlt . sososol • l • l •

so· I •

Corrooeenon Protein

.

so; a

.m

so.;

I

Corrooeenon

.Dt FIGURE 7. Ionic interactions of carrageenan and protein. (From Moirano, A. L., Marine Colloids Division (FMC Corporation), Carrageenan , Monograph 2, Springfield, New Jersey, 1981. With permission.)

94

Food Hydrocolloids

Carrageenan has been found to react with the casein fraction, both at the pH of normal milk (pH 6.7) and at the isoelectric point of casein (pH 4.6). It is thus very effective in stabilizing milk-based products. 8 · 109 In milk itself, the calcium-sensitive a-casein and !3-casein protein fractions are stabilized by a third casein fraction, kappa-casein. If the latter is removed or inactivated, the calciumsensitive casein components will react with the calcium ions in the milk and coagulate or precipitate. 110 - 111 Carrageenan, specifically kappa-carrageenan, by reacting with casein is as effective as kappa-casein in stabilizing calcium-sensitive casein fractions. This interraction with protein is further supported by the fact that lambda-carrageenan, which does not gel in water under any circumstances, forms gels with milk at concentrations of about 0.2%. This protein reactivity of carrageenan with milk casein is also related to its solubility in cold milk as demonstrated by a light scattering technique which confirmed the formation of gellike structures. 112 With kappa- and iota-carrageenan there is also a water-gelling effect and a gel strength enhancement due to the cations present in the carrageenan as well as the cations (calcium and potassium) present in the milk. In addition to stabilizing a-casein, carrageenan has also been used to stabilize !3-casein, 111 para-casein, 113 as well as soy, peanut, cottonseed, and coconut proteins 114 against precipitation with calcium. The mechanism involved in stabilizing these proteins is presumably the same as that of the carrageenan/a-casein system just described. This phenomenon of casein stabilization is believed to account for the effectiveness of carrageenans as stabilizers for evaporated milk and infant milk formulas and probably also for the cocoa-suspending property of carrageenan in chocolate milk. 109 F. Applications Carrageenan applications are generally divided into two major groups; for water-based systems and for milk-based systems. Although milk is an aqueous system, the unique interaction of carrageenan with the casein micelle in milk has led to the development of many specific applications in the dairy industry that makes them different from water-based systems where carrageenans are not complexed with protein. Tables 4 and 5 list the major uses of carrageenan in water-based and in milk-based systems, most of which will be discussed in more detail in the following section. Furcellaran, being like kappa-carrageenan, has similar, but more limited uses. Furcellaran is used in the following types of products, primarily in Europe, where it is produced and marketed: flan jelly, Tortenguss, and other cake-covering jellies, piping jelly and decorating jelly, jams and other fruit preserves, fruit juices, confectionery products, meat products (jellied veal, minced meat, meat pie fillings), milk puddings and custards, chocolate milk, and beer (clarification). 94 Detailed reviews of the food applications of carrageenan and furcellaran have been written by Glicksman, 116 Towle, 117 Moirano, 6 Pedersen, 118 and Guiseley et al. 84 1. Milk-Based Product Applications a. General The stabilization with carrageenan of evaporated milk, chocolate milk, ice cream, nondairy toppings, and coffee whiteners has been shown to be responsible, at least to an important degree, to the reaction and complex formation between sodium caseinate and carrageenan at specific pH levels. 119 Dairy and related product emulsions having an aqueous phase in the pH range 3.0 to 5.5, such as mayonnaise, cream, yogurt, butter, and margarine, can be stabilized and protected during pasteurization, by adding a carrageenan-protein complex made by reacting carrageenan with whey, blood serum proteins, soy proteins or similar materials. 173 The use of carrageenans in a wide range of milk products has been reviewed by Dobers 120

95 Table 4

CARRAGEENAN APPLICATIONS IN MILK SYSTEMS Use Frozen desserts Ice cream, ice milk Pasteurized milk products Chocolate, egg-nog, fruit-flavored Fluid skimmilk Filled milk Creaming mixture for cottage cheese Sterilized milk products Chocolate, etc. Controlled calorie Evaporated Infant formulations Milk gels Cooked flans or custards Cold prepared custards (plus TSPP) Pudding and pie fillings (starch base) Dry mix cooked with milk Ready-to-eat

Whipped products Whipped cream Aerosol whipped cream Cold prepared milks Instant breakfast Shakes Acidified milks Yogurt

Function

Approximate use level

Type

(%)

Whey prevention Control meltdown

Kappa

0. 0 I 0--0.030

Suspension, bodying

Kappa

0.025--0.035

Bodying Emulsion stabilization, bodying Cling

Kappa , iota Kappa, iota

0.025--0.035 0 .025--0.035

Kappa

0.020--0.035

Suspension, bodying Suspension, bodying Emulsion stabilization Fat and protein stabilization

Kappa Kappa Kappa Kappa

0.010--0.035 0.010--0.035 0.005--0.015 0 .020--0.040

Gelation

Kappa , kappa

Thickening, gelation

Kappa , iota , Lambda

0.20--0.50

Kappa

0.10--0.20

Syneresis control, bodying

Iota

0.10--0.20

Stabilize overrun Stabilize overrun, stabilize emulsion

Lambda

Kappa

0 .50--0. 15 0.02--0.05

Suspension, bodying Suspension , bodying, stabilize overrun

Lambda Lambda

0.10--0.20 0.10--0.20

Bodying, fruit suspension

Kappa gum

+

iota

0.20--0.30

Level starch gelatinization

+ locust bean

0.20--0.50

From Carrageenan, Monograph 1, Marine Colloids Division (FMC Corporation), Springfield, N .J., 1977. With permission.)

and Anon., 121 and practical use levels have been reported by Guiseley et al., 84 and Moirano, 1 and others 122 as shown in Table 4.

b. Ice Cream Products Ice cream is a complex system that can be defined as a partly frozen foam consisting of a gas (air) dispersed as small air cells in a partially frozen continuous aqueous phase . This continuous aqueous phase contains fat dispersed as the inner phase in an oil-in-water emulsion, non-fat milk solids and stabilizers in colloidal solution, and sugar and salt in true solution. ' 23 • 125 The primary function of stabilizers in ice cream is to influence the rheological

96

Food Hydrocolloids

Table 5 CARRAGEENAN APPLICATIONS IN WATER SYSTEMS· Use

Function

Carrageenan type

Dessert gels

Gelation

Low-sugar jellies, jams, preserves, etc.

Gelation

Pet-foods (canned)

Fat stabilization thickening, suspending, gelation Gelation

Fish gels Syrups Fruit drink powders and frozen concentrates Relishes, pizza, barbecue sauces Pimiento olive stuffing

Gelation

Fruit analogs

Gelation, texturizing

Lemon pie filling Chiffon (whipped) pie fillings Salad dressing Gelled condiments

Gelation Gelation, overrun stabilization Emulsion stabilization Gelation

Tomato aspics Meat binding

Gelation Gelation, water-binding

Gelled bakery glazes Dairy analogs (nondairy) Imitation milk whitener Imitation coffee Whipped toppings

Gelation

Puddings (non-dairy)

Suspension, bodying Bodying Pulping effects Bodying

Bodying, fat stabilization Emulsion stabilization Emulsion and overrun stabilization Gel stabilization

Approximate use level, (%)

Kappa + iota Kappa + iota + locust bean gum Kappa+ iota Kappa+ galactomannans Kappa + locust bean gum

0.5-1.0

Kappa + locust bean gum Kappa + iota Kappa, lambda Sodium kappa, lambda Potassium/calcium kappa Kappa

0.5-1.0

Kappa + locust bean gum Kappa + locust bean gum + alginate Kappa Kappa + locust bean gum Iota Kappa + locust bean gum Kappa + iota Kappa + locust bean gum Kappa

2.0

0.5-1.0 0.2-1.0

0.3-0.5 0.1--0.2 0.1--0.2 0.2--0.5

0.5-1.0 0.3-0.5 0.5-1.0 0.4--0.6 0.5-1.0 0.5-1.0 0.3-0.5 0.3-0.7

Iota, lambda Lambda Kappa, iota

0.03-0.06 0.1--0.2 0.1--0.3

Kappa

0.1--0.3

(Taken from Moirano, A. L., in Food Colloids, Graham, H. D., Ed., Avi Publishing, Westport, Conn., 1977, chap. 8; and Guiseley, K. B., Stanley, N. F., and Whitehouse, P.A., in Handbook of Water Soluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill, N.Y., 1980, chap. 5.)

conditions of the water phase by means of their water-binding effect. Secondarily they may have other beneficial functional properties such as reacting with milk protein or emulsifying oil-in-water mixtures. In general an ice cream stabilizer is used to prevent the separation or uneven distribution of fat and other solids, to prevent the growth of large, grainy ice and/or lactose crystals, and to impart proper body, smoothness, bite, meltdown, and other desirable textural features. At one time or another, almost every gum has been used for this purpose, and even today many different hydrocolloids and mixtures of gums are used. Although none of the current ice cream stabilizers is completely satisfactory in all applications, carrageenan has proved to be one of the most effective stabilizers when used in combination with other gums.

97

Carrageenan alone is not a satisfactory stabilizing material for ice cream, because it greatly increases viscosity, making difficult or impossible the introduction of a sufficiently large quantity of the gum for adequate stabilization. 126 • 127 However, it is extremely useful as a secondary stabilizer when used with primary stabilizers such as locust bean gum, guar, carboxymethylcellulose, or combinations of these. The primary stabilizers in many ice cream mixes are locust bean gum and sodium carboxymethylcellulose 128 · 129 each of which has excellent water-holding properties. However, each has the unfortunate tendency of sometimes causing whey separation in the ice cream mix. This ••wheying-off'" tendency can be eliminated or reduced by including a balancing colloid such as carrageenan. A great many of the commercial ice cream stabilizers are therefore tailored blends of locust bean gum-carrageenan, carboxymethylcellulose-carrageenan, guar-carrageenan, and other similar combinations. 183 This effective combination of carrageenan with other gums has been reported many times in the literature; carrageenan and guar by Werbin 130 • 131 and by Julien; 132 carrageenan and CMC by Blihovde; 133 carrageenan and locust bean gum by Moss, 128 - 139 etc. The use of kappa-carrageenan as a secondary stabilizer at a concentration of 0.01 to 0.5% in combination with a primary stabilizer such as locust bean gum, guar, or carboxymethylcellulose, adds creaminess, controls ice crystal formation, and prevents syneresis under freeze-thaw conditions; also the combination eliminates whey separation in the ice cream mix. 128.130.134.136 Combinations of carrageenan with xanthan and guar gums have been effectively employed in stabilizing aerated frozen dessert products. 222 Carrageenan has been used in preparing frozen ice cream-like products to reduce the tendency to melt and drip when thawing. 137 A spray-dried non-dairy mix for making ices in soft ice cream freezers utilizes carrageenan as the stabilizer. 138 Special blended stabilizers have been reported to give preferred properties, such as the use of locust bean gum and carrageenan to avoid an increase in viscosity during storage of the finished ice cream. 139 A similar stabilizer system was used to prepare ice cream that is easily spoonable at freezer temperatures. 184 Comparative evaluations of individual stabilizers and stabilizer blends have been reviewed by Rothwell and Palmer, 140 Boyer, 141 and Redfern and Arbuckle. 142 Chocolate syrups for making chocolate milk or for producing variegated ice cream products also utilize carrageenan. These syrups are composed primarily of water, sugar, and cocoa plus carrageenan and emulsifier to keep it uniform, homogeneous, and easy to handle. The function of carrageenan in such products is to maintain the cocoa in suspension and in ice cream to prevent ••feathering" when the syrup is added to the ice cream. Fruit flavored syrups are also used for variegating ice cream and here carrageenan functions in a similar manner. In fountain toppings, sauces, and fudges, carrageenan is used together with other gums and starches to impart desirable texture and flow properties. In applications involving maple syrup and pancake syrups, carrageenans, particularly the non-gelling lambda-carrageenan types, have been employed to impart mouthfeel and body. In low calorie sugarless syrups the addition of carrageenan is extremely important since the body and mouthfeel contributed by sugar is missing and carrageenan or other gums are needed to provide it. c. Milk Beverages All of the non-gelling milk applications, wherein carrageenan is used to suspend cocoa in chocolate milk, prevent whey separation in ice cream, prevent fat separation in evaporated milk, or stabilize protein in baby formulations, require the use of kappa-carrageenans having

98

Food Hydrocolloids

at least a 25% ester sulfate content. Carrageenans with lower ester sulfate levels at about 20% or, furcellaran which has even lower ester sulfate content (approximately 12 to 15%), do not function in such systems. For the preparation of milk gels, the high ester sulfate requirement is not so critical and good products can be made with low level ester sulfate carrageenans. There are several types of milk beverage products, each requiring special attention and consideration, e.g., pasteurized milk beverages, sterilized milk beverage, dry mix milk beverages, and acidified milk products. i. Pasteurized Milks

Pasteurized milk products were formerly prepared by batch pasteurization techniques but today they are manufactured by use of high-temperature, short-time (HTST) techniques. Chocolate milk commonly contains about 6% sugar and about l % cocoa. It is usually pasteurized at about 82°C and then cooled with agitation to about 4°C prior to filling. Kappacarrageenan is typically used at levels of about 0.025% to 0.35% to keep the cocoa in suspension and at the same time provide a good mouthfeel simulating the fatty mouthfeel of full-fat milk. 143 • 144 In filled milk and skimmed milk, carrageenan functions as an emulsion stabilizer as well as a bodying agent to contribute mouthfeel and texture to the product especially those that contain little or not fat. 145 Moirano 1 claims that a 3.5% butterfat milk can be simulated by using only I% butterfat together with a carrageenan at a low concentration. Many other milk applications employ the protein reactivity and stabilizing properties of carrageenan. Berndt and Klein 146 developed a method for making a carrageenan from acid treated C. crispus for use in blending with chocolate syrup, to be used with milk to give a stable chocolate beverage. Stoloff 147 stabilized chocolate milk products by heating with 0.01 % carrageenan and adding the finely ground flavor component after cooling. Hotelling 148 improved the stabilizing properties of carrageenan for chocolate beverages from non-fat dry milk by using a combination of carrageenan and dioctyl sodium sulfosuccinate. Wilcox 149 showed the effectiveness of very small quantities of carrageenan ( .0075 to .020%) in making homogenized liquid milk products by the high-temperature, short-time method. These products are stable, have a normal viscosity and do not thicken upon cooling. Willard and Thomas 150 developed pilot plant methods for determining the minimum amount of stabilizer necessary to prevent settling in chocolate milk beverages. By these means they were able to distinguish between the various commercial stabilizers and to select the best stabilizer and the ideal concentration required for optimum effectiveness. ii. Sterilized Milks

Sterilized milk products differ from pasteurized ones in that they are subjected to much higher heating temperatures. Older procedures employed stationary autoclaves in which bottled or canned products were brought to temperatures of about 116~ and held for varying lengths of time. Many problems were encountered, including off-flavor, settling of cocoa, and general deterioration of quality. Modern systems use either rotary-type autoclaves in which the contents are under agitation during heat-processing or employ high-temperature, short-time systems wherein the fluids are rapidly brought to sterilization temperatures of about 143@C and held for very short periods of time (about 10 sec). The processed liquids are then cooled and filled aseptically at ambient temperatures into previously sterilized containers. These procedures give much better flavor and more stable products. Carrageenan is employed in all of these processes and, depending upon operating conditions, varying but small levels of carrageenan prevent settling of the cocoa and improve the body and texture of the final product. Metered calorie dietary products usually contain high amounts of solids particularly milk

99 protein and soy protein. The products are normally manufactured by using rotary autoclaving or aseptic packaging techniques. Carrageenan is incorporated to prevent the insoluble materials from settling out, to prevent fat separation, to emulsify the components, and to impart good body and mouthfeel. Levels of about 0.02% to 0.03% of carrageenan are typically employed. Evaporated milk normally contains about 10% fat which, during processing and storage, tends to separate out causing a rather undesirable layering in the product. This problem has been eliminated by including as little as 0.005% kappa-carrageenan. It is now included in the FDA Standards of Identity for evaporated milk. Wilcox 149 showed that as little as 0.01 % kappa-carrageenan prevents fat separation and imparts smoothness to such concentrated milk products. Moirano 6 believes that the effectiveness of carrageenan in these products is due not only to its ability to complex with a casein molecule in a milk product but also with the ability of the carrageenan to react with the basic amino groups of the lecithin present in the fat globules to form a carrageenan/phospholipid bond. Baby food formulations have shown great growth during the last two or three decades. Usually two types of products, packaged in cans or bottles, are sold. One is the concentrate which is diluted with water prior to use, and the other is the single-strength type which is ready for consumption. Most of these products contain milk and/or soy protein and varying levels of vegetable oil or butterfat. They are usually processed by rotary autoclaving methods. Carrageenan at low levels is essential in almost all of these products in order to stabilize the fat and protein components. Bauer et al. 151 employed carrageenan to prepare calcium-enriched milk products for infant feeding. By selection of appropriate processing conditions a product with sufficient body and texture was obtained and the calcium components were kept in suspension during storage by the gum. iii. Dry Mix Beverage Products

Dry mix, instant breakfast beverages have achieved noteworthy popularity in recent years. These mixes contain a blend of nutritionally-balanced ingredients. They are reconstituted with cold milk before use. The incorporation of carrageenan gives products in which the protein and cocoa (if used) remain suspended, and yields a beverage with a rich body, mouthfeel and texture. Similarly milk-shake dry mixes prepared for use by mixing with cold milk contain carrageenan to improve the foam stability as well as the mouthfeel of the finished beverage. In such products, carrageenan has been used in combination with other gums such as CMC and methylcellulose to provide good body, mouthfeel, and a stable foam. In many cases, combinations of gums give improved functional properties due to the synergistic effects or offer economic advantages of lower cost without loss of quality. Chocolate milk powder having extended shelflife has been made by spray-drying a peroxide- and enzyme-treated cocoa syrup containing carrageenan as the preferred stabilizer. 152 Carrageenan is used in many of the dietetic beverage preparations that are currently on the market. This includes both the dry powder mixes which are to be reconstituted with milk before use as well as the canned ready-to-use liquid preparations. Carrageenan stabilizes the suspension of the insoluble ingredients and gives good body and texture as well as creamy mouthfeel to the reconstituted products.

d. Milk Puddings Carrageenan and furcellaran form gels with milk that have a smooth, tender but firm texture best described as custard, flan, or '"blanc mange" pudding. Traditionally, flans and custards have been made with combinations of sugar, eggs, milk, and flavoring ingredients. The products, after being blended are baked which coagulates the egg proteins and forms

100

Food Hydrocolloids

the gel. The use of carrageenans eliminates the need for eggs and very good custard or flanlike products are now made without the use of egg. Carrageenan has been used alone to give a light-bodied, eggless "'custard" or '"blanc mange" dessert. Or combined with cornstarch, tapioca starch, and other starch blends it yields the more common starch-type puddings and pie fillings. These custards or flans are preferred desserts in Europe, Japan, and South America whereas in the U.S., starchbased puddings are still preferred. Furcellaran finds its major application in such puddings where it appears to give a subtle, somewhat different, but preferred texture to carrageenan, best described as smoother and creamier. It is exceptionally effective in stabilizing high-fat milk puddings such as flan. Carrageenan is not as effective in such applications. Furcellaran is used in flan or milk pudding mixes and in ready-to-eat prepared puddings at levels of about 0.5%. It gives the best texture and appearance in the pH range of 6.6 to 6.7. 94 In recent years, due to a shortage offurcellaran, many such products have been made with mixtures of furcellaran and carrageenan or of carrageenan alone. Both carrageenan and furcellaran have been used to prepare low calorie and/or sugarless versions of such custard and flan-like puddings. i. Cooked Milk Preparations

Many dry mix products for use with hot milk have been developed using various carrageenan bases. Thus, custard or "'blanc mange" desserts have been prepared by incorporation of O. l to 0.3% kappa-carrageenan, sometimes in combination with furcellaran, locust bean gum, or phosphate salts in a suitable milk base formulation. 153- 155 By incorporation of starch and smaller amounts of carrageenan (0.05 to 0.1 %), heavier-type puddings can be produced. Polya and Green 153 developed an egg-base custard mix based on carrageenan that is reconstituted with milk to give a good quality, simulated egg custard dessert. Moirano 156 utilized carrageenan in developing a flan-type milk pudding dessert mix. In cooked starch pudding dry mix products, carrageenan has been used to increase recipe tolerance and improve textural firmness. 157 ii. Cold Milk Puddings

Cold-set, quick preparation, milk puddings have been developed based upon non-gelling

lambda-carrageenan. 158 These were substantially improved by using blends of fine mesh lambda-carrageenan and a phosphate salt such as tetrasodium pyrophosphate. Carrageenan

concentrations of 0.2 to 0.1 % reportedly give instant gels in cold milk systems. They have good flavor, texture, and show freedom from syneresis. 158 iii. Frozen Milk Puddings

Glicksman 159 employed the novel properties of iota-carrageenan in the preparation of freeze-thaw stable milk puddings and water-gel desserts. Carasso 160 used carrageenan to stabilize a frozen, expanded, milk pudding-type of dessert.

iv. Canned, Ready-To-Eat Puddings

Ready-to-eat, aseptically canned milk pudding desserts and baby food puddings have also been made using carrageenans, although starches are more commonly employed. Sterilized milk products such as custard and ice mixes may be stabilized by the addition of O. l to 0.5% carrageenan prior to sterilization. 166 v. Acidified Milk Gels

The widespread and growing popularity of yogurt has created new uses for carrageenan. Yogurt is normally prepared by pasteurizing milk, cooling to incubation temperature, adding a culture, then allowing the acidity to develop. The latter causes a coagulation of the milk

101

casein and gives the typical yogurt-type gel. Since the more popular products contain fruit, various methods have been developed whereby the fruit is added before or after fermentation. The final product is a ..Swiss Style" product wherein the fruit is suspended evenly throughout the yogurt. Gelatin is used widely for this purpose but carrageenan also functions effectively. Low-fat yogurt and other acidified milk products may be stabilized without loss of texture by use of locust bean gum in combination with kappa-carrageenan or furcellaran or agar in a 6: 1 to 1: 1 ratio. 161 Moirano 1 recommends a combination of carrageenan and locust bean gum to form smooth-texture yogurts having pHs of 3.8 to 4.4 Soft fruits e.g. strawberries and raspberries, added to yogurt, may be protected from damage by heating to pasteurization temperatures in a container with sugar syrup containing carrageenan or low methoxyl pectin. Upon cooling, a gel forms which enrobes and thus protects the fruit until they are needed for adding to the yogurt. Yogurt has also been made from formulated filled milk preparations. 163

e. Cheese Products Creaming mixtures used in cottage cheese production perform two functions: 1. they stabilize the mixture (prevent fat and whey separation); and 2. impart sufficient body to provide ••cling" to the cottage cheese curd. Carrageenan is often used in combination with locust bean gum for this application. In cottage cheese manufacture, carrageenan is used to induce small curd formation under low pH conditions. Usually about 0.4% carrageenan by weight of milk is used. Kappa-carrageenan at a concentration of 0.01 to 0.05%, usually in combination with locust bean gum is used to induce curd formation, impart shape retention, and prevent syneresis in cottage and creamed cheese products. 164 f. Whipped Cream Products Whipped cream can be stabilized and improved in texture by small amounts ofcarrageenan. In canned, aerosol-type products, incorporation of carrageenan stabilizes the fat emulsion without developing excessive viscosity. In addition, carrageenan contributes to foam stability when the product is used. Carrageenan is frequently used in combination with locust bean gum in these applications. 1 In frozen, whipped-cream products, carrageenan gives products with good texture and much longer storage life than untreated whipped cream. 165

2. Water System Applications Typical carrageenan applications in water systems are shown in Table 5, which shows the recommended types and quantities of carrageenans used. a. Dessert Gels Dessert gel products may be conveniently divided into three major categories: 1. 2. 3.

Dry mixes for hot water preparation Dry mixes for cold water, instant-type preparation Prepared, ready-to-eat gels

i. Hot Water Preparations

Among hot-water preparation products, gelatin desserts are by far the most popular currently in use. These foods such as .. Jell-O"® gelatin desserts are sparkling clear, visually attractive, smooth textured, and very palatable products. Gelatin melts at mouth temperature and the organoleptic textural effects thus achieved at this eating temperature includes a quick, highly apparent flavor release and a smooth eating texture that is the most popular to the

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Food Hydrocolloids

consumer. Carrageenans, especially the iota-carrageenan, have somewhat similar properties to gelatin but melting temperatures are higher and therefore the mouthfeel and melting characteristics are not so good. However, carrageenans have the advantage that they do not melt at room temperature nor require refrigeration in order to form a gel. Dry mix desserts based on carrageenans come in a variety of combinations permitting the production of high quality products, especially by using kappa-carrageenan in combination with either locust bean gum or iota-carrageenan, or even by using low-molecular-weight kappa-carrageenan alone. Usually, the economics and the individual requirements of the manufacturer are the overriding considerations in deciding on particular formulations. In the mid- l 940s it was discovered that the brittle, non-elastic texture of kappa-carrageenan in water desserts gels could be modified by the incorporation of locust bean gum and also agar to give improved and acceptable elastic gel textures. 167 ' 170 As a result, dry mix products based on modified kappa-carrageenan systems were developed for commercial use. 171 As the science and art advanced, improved dessert gels of this type were made by using appropriate combinations of kappa-carrageenan (to provide rigidity and firmness) and iotacarrageenan (to provide elasticity and tenderness.) 172 Essentially these findings may be summarized by noting that kappa- and iota-carrageenan at a concentration of 0.1 to 0.5% in combination with a refined galactomannan and potassium salts, dissolved by heating, forms a clear, resilient gel that is stable at room temperature. Such gels are ideally suited for use as dessert gels and in the preparation of gelled-fruit baby foods. Gels prepared with iota-carrageenan are stable under freeze-thaw conditions. 159 Although higher meling then gelatin, these gels approached the smooth, ideal mouthfeel of gelatin gels. The clarity and resistance to syneresis of water dessert gels may be improved by the use of locust bean gum and potassium citrate in combination with kappa- and iota-carrageenans. 174 Novel heat-stable gels have been made by combining the thermosetting properties of carrageenan with the calcium-induced gelling properties of carrageenan with the calciuminduced gelling properties of sodium alginate. Mixtures of carrageenan and sodium alginate in water are heated to form a clear solution, and then cooled to form a gel. This is then placed in a calcium salt solution. By diffusion, the calcium replaces the sodium in the gel to form a calcium alginate network. The modified gel can then be flavored by immersing in a flavoring solution to give an unusual dessert gel product . 175 ii. Cold Water Preparations

Since the gelling carrageenans are not soluble in cold water, they cannot be normally employed in cold water dessert systems. However, modifications to overcome this problem have been reported in the patent literature. Glicksman et al. 176 developed cold-preparation, instant desserts products by converting iota-carrageenan into the cold-water-soluble sodium salt of iota-carrageenan. Sodium iota-carrageenan at a concentration of 0.6 to 1.2% in combination with an acid and a calcium or potassium salt dissolves in cold water and forms a gel. Powdered formulations that can be added to cold water to give instant desserts gels have been described. iii. Ready-to-Eat Desserts

Ready-to-eat, single serving dessert gels marketed in small metal cans or plastic cups have become popular food items. These products do not require refrigeration and have excellent shelf-life. They are usually heat-processed by the use of a high-temperature, shorttime system which involve rapid heating, holding at sterilization temperatures for a short time, and then rapid cooling, followed by filling into pre-sterilized containers. Since these gels have a pH between 3.5 and 4.0 they require such rapid processing in order to avoid

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hydrolysis when carrageenan is the gelling agent. Some batch methods have also been developed; in such cases, the acid is usually added directly to the containers at the end of the production cycle. These products have been developed to a high state of the art using specific combinations of gums. A common gelling system employed is a mixture of kappaand iota-carrageenans. Another effective combination uses kappa- and iota-carrageenan plus clarified locust bean gum. 1 In addition to conventional desserts, other similar ready-to-eat products have been developed such as baby foods, canned snacks, and dietetic desserts. Such products do not melt at ambient temperatures, have good flavor and texture and do not show syneresis or harden on storage. Other interesting modifications have been made by the inclusion of fruit to make canned, ready-to-eat citrus fruit salad gels. 111 · 118 Woods 179 used carrageenan plus locust bean gum and sometimes low methoxyl pectin to make citrus salad gels from broken, crushed or whole grapefruit and orange sections. And, grapefruit and orange pulp were used to make jellied sauces. The fruit components are gelled in a citrus-flavored gel base to give canned salads that remain stable without refrigeration. Moore et al. 180 found that a three component system of carrageenan, low methoxyl pectin, and locust bean gum gives the best results with canned grapefruit salad and jellied orange sauce. This gel system was further improved by Rouse et al. 181 to produce an exotic gelled product consisting of diced mango in orange juice. The freeze-thaw stability property of iota-carrageenan has been used for preparing canned dessert gels and milk puddings which withstand freezing and thawing without textural breakdown. 159 b. Dietetic Gels and Jellies Conventional fruit jelly contains 65% sucrose and is gelled by the use of high methoxyl pectin. High methoxyl pectin requires both high levels of sugar and the presence of acid for gelation. In low calorie jelly, the gel system has to be able to gel without sugar. Carrageenan is very effective in this application and the typical combinations used are mixtures of kappa- and iota-carrageenans as well as blends of kappa-carrageenan and locust bean gum at levels of about 0.5 to 1.0%. Low methoxyl pectin can also be used for such applications but tends to be unreliable due to batch-to-batch variations of the raw material which sometimes causes syneresis in the finished product. Low protein, low sodium, dietetic jellies have been made using carrageenan. 182 Furcellaran, which does not require acid or sugar to gel, has also been used to make conventional as well as sugarless, low calorie jams and jellies, using concentrations of 0.2 to 0.5%. 94 Towle 117 suggested the use of kappa- and iota-carrageenans at a concentration of 0.5 to 1.2% in combinations with a potassium salt and sodium citrate to give gels that are not sugar or calcium dependent. Locust bean gum or low methoxyl pectin may be added to modify the gel properties when these carrageenans are used. 3. Dairy Analogs a. Imitation Milk Beverages

In imitation milk products, sodium caseinate and soy protein are used in place of non-fat milk solids and the butterfat is replaced with a vegetable fat. Iota- and kappa-carrageenans at levels of about 0.02 to 0.4% are effectively used to stabilize the fat emulsion and to provide body and texture for these products. Milk analog beverages made of sweet whey and coconut fat are effectively stabilized with carrageenan. 185

b. Non-Dairy Puddings Non-dairy puddings or imitation milk puddings are based upon vegetable fat, milk or soy

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Food Hydrocolloids

protein, emulsifiers, and an appropriate gelling system. The most popular of these products are ready-to-eat canned puddings and frozen puddings. Carrageenan is one of the major gelling and stabilizing systems for such products and has been very effectively used in many such applications. 1• 122

c. Non-Dairy Whipped Toppings

Many non-dairy whipped topping products have been developed over the last 20 years. Originally these were developed as spray dried emulsions for reconstitution by addition to milk and water. Subsequently, these were followed by the development of ready-to-use, frozen whipped toppings which are currently the most popular types. These products are distributed and stored frozen but are thawed out and used or may be kept in the refrigerator for up to two weeks before use. Most of these products are based upon sugar, vegetable fat, sodium caseinate or soy protein, emulsifiers and stabilizers. Carrageenan is one of the basic stabilizers used in such systems and in addition to providing for emulsion stabilization and maintaining high overruns, carrageenan also imparts excellent freeze-thaw stability. Kappa-Garrageenan at concentrations of 0.15 to 0.5% has been shown to give whipped topping mix products of improved stability. 187' 189 In frozen whipped toppings incorporation of mixed kappa!Lambda-carrageenan at a concentration of 0.03 to 0.05% results in products having improved body and showing reduced syneresis under freeze-thaw conditions. 165 • 190 Reconstituted whipping cream made by blending butterfat, non-fat milk solids and an emulsifier may be stabilized with carrageenan. 191 d. Non-Dairy Coffee Whiteners Non-dairy coffee creamers and other imitation creams based on vegetable fats, soy, milk proteins, emulsifiers, and other additives have been developed to the point where they are used widely in place of milk or cream. They have excellent shelf-life and can be purchased in several convenient forms such as dry powders, refrigerated liquids, and frozen liquids products. In almost all, carrageenan223 is used to stabilize the emulsion and to impart freezethaw stability in the case of frozen products. When added to coffee, carrageenan prevents feathering and the unsightly floculation and precipitation of protein. These products are preferred to milk or cream by many consumers because of low cost, improved shelf-life, as well as for such nutritional features such as unsaturated fat and low cholesterol levels. Regardless of type, they are essentially a stable, emulsified fat system either in liquid or dry form. Carrageenan at levels as low as 0.1 to 0.2% have been found to be very effective in stabilizing these products and in providing sufficient body to give a desirable texture and mouthfeel. In liquid coffee whiteners, the addition of mixed Lambda!kappa-carrageenan at a concentratitn of 0.3% in combination with carboxymethylcellulose, sodium alginate or refined galactomannan improves the colloidal dispersion of protein resulting in a better shelf-life. 192 Liquid and dry coffee whiteners made with whey solids (in place of sodium caseinates) and phosphate salts may also use carrageenan for stability and to insure good product performance. 193.194

4. Meat Products a. Canned Meat and Fish Products Carrageenan has been used ~s a gelling agent for canned meat and fish products where a firm, protective gel is needed. It has also been used as a gel binder in ground meat products such as pet foods as well as in caviar. Advantages of carrageenan are its ability to modify the strength and melting point of the gel. This is done by the selection of appropriate carrageenan-potassium chloride ratios. In addition to modification of texture, the moist and

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non-tacky properties of the gels allow very easy release from the metal can used to package these products. Kappa- and iota-carrageenans at a concentration of 0.2 to 0.5% along with potassium salts and sometimes in combination with locust bean gum are effective as binders in ground meat products, such as pet foods, or as a coating for whole-piece meat packs. 117 • 186 • 195 Furcellaran is also used as a stabilizing and gelling agent in products such as minced meat, meat paste, and pie fillings. Furcellaran should not, however, be used in meat products unless its compatibility with the proteins of the product has been established. 94 In specialized canned fish applications such as gefilte fish, carrageenan is used to gel the broth surrounding the product. The purpose here is to preserve the flavor, to maintain the uniform suspension of the seasonings and condiments, and to improve the palatability of the broth component of the product. In canned pet food applications carrageenans are used primarily in retorted products. Carrageenan, either alone or in combination with locust bean gum, is employed to prevent fat separation during heat-processing and to impart body and/or a rich appearance to the gravy. In some cases, the level of carrageenan is increased in order to develop gelled particles in the product. In Europe, many pet foods are prepared using carrageenan as the gelling component. In a related novel application, carrageenan is used in the preparation of fabricated feed for silkworms in the silk industry in the Orient; Japan and Korea. In this industry, sufficient mulberry leaves are not available to feed the large numbers of silkworms that are bred to produce silk. Therefore, food or feed is fabricated by blending a mixture of ground mulberry leaves, soy flour, soybean oil, vitamins, minerals, etc. and gelling it into food blocks (like pet foods) with carrageenan. These blocks are sold to silkworm growers who slice the block and shred the slices for use in feeding the silkworms. The consistency and composition of the gel block is a critical factor since the presence of too much water will cause the silkworms to drown. Sodium carrageenate has also been used to stabilize beef plasma emulsions prior to spraydrying. The spray-dried beef plasma was used to improve the texture and protein nutritional value of some sausage products. ' 96 b. Meat Analogs Carrageenan has been used in the preparation of fabricated protein fibers from soy, peanut, casein, and other proteinaceous materials. Carrageenan is incorporated in the individual fibers and also used as a binder for the fiber masses. Incorporation of 1% carrageenan in the protein solutions prior to extrusion and spinning gives fibers of improved quality. The addition of carrageenan to alkaline protein solutions prior to spinning, yields spun protein fibers with improved tenderness and texture. 199 Carrageenan can also be used as a component of the liquor used in binding the fibers into chunks. It is believed that the interaction of carrageenan and the protein gives improved product functionality and texture. 197 • 198 Fibrous proteinaceous materials have been made by complexing carrageenan with soybean whey at pH 3.8 to 4.4. 200 And carrageenan has been used as a protective coating for spun vegetable fiber meat analogs to make the product stable to cooking. 201 Fibrous, meat-like products are obtained without spinning by pretreatment of wheat gluten with alkali and a reducing agent, followed by heat treatment with small amounts of carrageenan. The resultant fibrous flake gluten has satisfactory meat analog properties. 202 5. Fruit Beverages Dry beverage mixes, especially orange flavored types, are very popular. Such beverages may employ gums to produce a mouthfeel and textural property that would be lacking in plain water formulations. Carrageenan has been employed also to produce a pulpy character in some citrus fruit beverage mixes. 203

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Food Hydrocolloids

In frozen beverage concentrates, carrageenan is employed for this same purpose. In spite of the low pHs encountered, carrageenan is stable where the product is either dry or frozen. In heat-processed, liquid products carrageenan is not suitable, however. Cloud agents for non-alcoholic beverages, made by reacting carrageenan with insoluble protein, preferably from whey, at pH of 3.2, are stable even after pastuerization treatment at 75°C. Fruit juices have been stabilized with 0.05 to 0.1 % of furcellaran to maintain an even suspension of the fine pulp particles. 94 6. Salad Dressings, Sauces, and Relishes Carrageenan is used in various salad dressing preparations but is particularly well suited for dry mixes that are to be reconstituted with water and with oil. In bottled pourable salad dressings carrageenan will hydrolyze at the low pHs during storage and so other hydrocolloids are used, but in dry mixes carrageenan performs well. Carrageenan has been used effectively to stabilize mustard and cocktail sauces, spaghetti sauces, white sauces, pickle relishes, gravies, etc. It is particularly effective in preventing separation of the various components, in providing desirable body and texture, and also in improving the adhesion and general flow properties of the product. Improved flavor appearance and body in pickle relishes as well as longer shelf-life has been reported by Anderson, et al. 204 Although most barbecue sauces, relishes, and related products have a low pH, carrageenans can be safely used if a certain amount of gelation is produced in the finished product. For some unknown reason, the presence of tomato seems to enhance the stability of carrageenan in these products. 1 7. Dough Products Carrageenan has been used as an additive in various dough products because of its influence on texture. Glabe et al. 205 reported that 0.1 % of carrageenans in dough and bread, function as a flour conditioner during baking to give improved textures to the finished product. In continuous bread baking processes, the addition of carrageenan in combination with hydroxylated lecithin has been shown to produce a synergistic effect on the flour proteins in doughs containing milk solids, resulting in doughs having improved strength and breads improved in loaf volume, loaf shape, and texture. 206 -201 In sweet dough products such as plain cake, fruit cake, and yeast-raised doughnuts, carrageenan at levels of about 0.1 % gives a moister texture and allows for a more uniform distribution of fruit and other ingredients. 208 In breading and batter mixes, carrageenan has been used to strengthen and extend the protein ingredients. In such applications, it improves control of body and flow properties and permits uniform coverage and improved adhesion of the batter to chicken, shrimp, fish sticks, and other food products. 116 In pasta products, carrageenan at levels of 0.05 to 0.30% improves the resistance of spaghetti to break down and deterioration during cooking. 205 The addition of 0.1 to 0.2% of lambda-carrageenan in macaroni allows the incorporation of up to 25% non-fat milk solids in the product for added nutritional value and enhanced flavor. 209 8. Confectionery Although not much used in confectionery products, Cakebread210 has suggested taking advantage of the gelling properties of carrageenan for making dietetic jellied confections. In frozen confectionery products, syneresis can be reduced by the incorporation of carrageenan. 211 In caramels, toffees, and similar confections carrageenan has been added to retain smooth attractive textures by preventing '"oiling off" of the products in hot weather.

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A novel confectionery application for carrageenan is its use in making edible molded toys. Carrageenan in combination with glycerol and/or propylene glycol, together with some starch plus flavor and color, gives a liquid composition that can be poured into a mold, heated to a predetermined temperature (at which the liquid will solidify) and on cooling, can be unmolded to give an edible, shaped object (animal, star, etc.) or a conventional jelly confection. 212 ·213 9. Miscellaneous Products Fabricated, imitation fruit pieces having a texture similar to real fruit were prepared by extruding a carrageenan-Iocust bean gum gelled mixture of sugar, flavor, and color through a cooling tube, and then slicing into small pieces. 214 Fruit preserves such as orange, strawberry, raspberry, and plum have been made using carrageenan. 215 Carrageenan has been used in preparing frozen fruits such as strawberries, peaches, etc. where small amounts of gum gives better gloss, improved appearance, firmer texture, and overall better quality. 216 ·217 Protective coatings of carrageenan have been utilized for dried fruits and nuts as protection against mold growth on materials which are used as ingredients of cake mixes. 218 Carrageenan has been added to beer as an auxiliary fining agent to accelerate and improve clarification and stabilization. 219 J 20 Furcellaran has also found application in beer manufacture as a fining agent added during hop boiling to assist coagulation and precipitation of proteins from the wort and as an auxiliary fining ingredient when added at the end of fermentation to promote flocculation. The final filtration step is facilitated, and the beer can be stored with less risk of cloudiness developing. 94 Carrageenan has been used in the preparation of a stable powdered dehydrated sauerkraut juice. 221

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167. Baker, G. L., Edible gelling composition containing Irish Moss extract. locust bean gum and an edible salt, U.S. Patent 2.466,146, 1949. 168. Baker, G. L. Gelling compositions, U. S. Patent 2,669,519, 1954. 169. Baker, G. L., Carrow, J. W., and Woodmansee, C. W.,Foodlnd., 21,617, 1949. 170. Frieden, A. and Webin, S., Irish Moss gelling agent, U.S. Patent 2,427,594, 1947. 171. Standard Brands Inc., Irish Moss food product, British Patent 841, 973, 1960. 172. Foster, S. E. and Moirano, A. L., Dessert gel, U.S. Patent 3,342,612, 1967. 173. Unilever N. V., Food buffering agents of globular protein/anionic polysaccharide complexes, West German Patent 2,325,131, 1974. 174. Moirano, A. L., Dessert gel, U. S. Patent 3,445,243, 1969. 175. Aoba Kasei Co., Heat stable gel dessert, Japanese Patent J7 4034-823, 1974. 176. Glicksman, M., Farkas, E., and Klose, R. E., Cold water soluble Eucheuma gel mixtures, U. S. Patent 3,502,483, 1970. 177. Rouse, A.H., Moore, E. L., Atlins, C. D., and Grierson, W. Bryan, D.S., Gel-coated ready-to-serve grapefruit halves, Proc. Fla. State Hort. Soc., 82, 227-229, 1969. 178. Rouse, A.H., Moore, E. L., Atlins, C. D., and Grierson, W., Proc. Fla. State Hort. Soc., 82, 224-227, 1969. 179. Woods, C., Tasty new citrus products unveiled at citrus station, Sunshine State Agric. Res. Rep., 14(4), 3-6, 1969. 180. Moore, E. L., Rouse, A. H., Atlins, C. D., and Hill, E. C., Multipurpose gel used in preparing new citrus products, Citrus Ind., 52(5), 6-8, 1971. 181. Rouse, A.H., Barmore, C.R., and Moore, E. L., Salad gels with low sugar content, Citrus Ind., 55(6), 18-21, 1974. 182. Anon., Non-refrigerated gels save time and labor, Food Eng., 41(5), 38, 1971. 183. Osborne, J. T., Stabilizer blend, U. S. Patent 3,996,389, 1976. 184. Dea, I. C. M. and Finney, D. J., Stabilized spoonable ice cream, U. S. Patent 4,145,454, 1979. 185. Kraftco Corp., Compositions containing whey and a method for making beverages, British Patent 1,277,772, 1972. 186. Collins, T. F. X. and Collins, E. V., Biological effects of carrageenan: a bibliography, FDA By-Lines, 8(5), 221-280 1978. 187. Berndt, L. H. and Krett, O. J., Fatty food composition, U. S. Patent 3,010,830, 1961. 188. Rodgers, E. B., Stabilized topping, U.S. Patent 3,350,209, 1967. 189. Lenderink en Cie N. V., Netherlands Patent 69,07,938, 1969; (C.A.) 72, 99 390y. 190. Lorant, G. J., British Patent 1,173,827, 1969. 191. Zadow, J. G. and Kieseker, F. G., Manufacture of recombined whipping cream, Aust. J. Dairy Tech., 30(3), 114--117, 1975. 192. Knightly, W. H.,FoodTechnol., 23, I, 1969. 193. Ellinger, R.H. and Schwartz, M. G., Compositions for replacing sodium caseinate in non-butterfat dairy products, U. S. Patent 3,615,661, 1971. 194. Ellinger, R.H. and Schwartz, M. G., Compositions for replacing sodium caseinate in non-butterfat dairy products, U.S. Patent 3,615,662, 1971. 195. Wirth, F., 1970 Canned meats, Fleischwirtschaft, 6, 848, 1970. 196. Lipner, S., Protein-enriched comminuted meat products, U. S. Patent 3,644,128, 1972. 197. Giddey, C., Artificial protein fibers, U.S. Patent 2,947,644, 1960. 198. Giddey, C., Protein meat-like food compositions, U.S. Patent 2,952,542, 1960. 199. Takeda Chem. Ind., Ltd., Fibrous protein foodstuff production, Japanese Patent J7 6,005,049, 1976. 200. Schmitt, E. E., Fibrillar soy-whey protein complex, U.S. Patent 3,792,175, 1974. 201. Horrocks, D., Buckley, K., and Booth, P., Meat-like protein food, German Patent 2,201,160, 1972. 202. Nisshin Flour Milling Co., Synthetic meat production from wheat gluten, Japanese Patent J7 5,002,023, 1975. 203. Glicksman, M. and Farkas, E. H., Beverage powder producing pulpy mouthfeel when dissolved, U.S. Patent 3,395,021, 1968. 204. Anderson, E. E., Plank, A. P., and Esselen, W. B., Quell separation in pickle relish, Food, 26(4), 131, 200-203, 1954. 205. Glabe, E. F., Goldman, P. F., and Anderson, P. W., Effects of Irish Moss extract on wheat flour products, Cereal Sci. Today, 2, 159--161, 1957. 206. Glabe, E. F., Carrageenan and hydroxylated lecithin. A stabilizer for continuous process bread, Baker"s Digest, 38(3), 42-44, 1964. 207. Glabe, E. F., Anderson, P. W., and Jertson, E. C., Carrageenan and hydroxylated lecithin applied to continuous mix bread, Cereal Sci. Today, 9(7), 1964. 208. Stoloff, L., Carrageenan, in Industrial Gums, Whistler, R. L., Ed., Academic Press, New York, 1959, 83-115.

113 209. Glabe, E. F., Anderson, P. W., and Goldman, P. F., Cereal Sci. Today, 12, 510, 1967. 210. Cakebread, S. H., Gelling agents: practical consideration and application of the alginates and carrageenan, Confect. Prod., 36(4), 220--222, 1970. 21 I. Creswick, A., Frozen confection, British Patent 1,233,258, 1971. 212. Ryan, J. W., Stastny, E. 0., and Burns, E., Method of producing a molded edible product, U.S. Patent 3,493,382, 1970. 213. Ryan, J. W., Stone, A. L., and Martin, E. T. III, Liquid heat-setting edible products, U.S Patent 3,493,383, 1970. 214. Miles Labs., Inc., Synthetic fruit, French Patent 2,157,819, 1972. 215. Ronold, O. A. Comparative experiments on gelatinizing agents for fruit preserves, Tidsskr. Hermetikind., 38, 249, 1952; (C. A.), 46, 7673a. 216. Wegener, J. B., Baer, B. H., and Rodgers, P. D., Improving quality of frozen strawberries with added colloids, Food Tech., 5, 7fr--78, 1951. 217. Knechtges, J. W., Preparing whole fruit for freezing, U. S. Patent 2,550,056, 1951. 218. Forkner, J. H., Jelled material in food preservation, U. S. Patent 2,821,477, 1958. 219. Griffiths, W., British Patent 912,492, 1962. 220. MacDonough, J. V., Clarifying and stabilizing beer, U. S. Patent 2,658,825, 1953. 221. Thackery, R.H., 1970 Diss. Abstr. B., 30(7), 3230, 1970. 222. Blake, J. R., Dairy based mixes for frozen desserts and method of preparation, U. S. Patent 4,282,262, 1981. 223. Bassett, H. J., Shelley, D. S., and Anderson, M. E,, Processing coffee whiteners, Am. Dairy Rev., 40(2), 35-37, 1978.

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115

Chapter 6

BROWN SEA WEED EXTRACTS (ALGINATES) Alan H. King

TABLE OF CONTENTS I.

Background ............... . ............ . ... . ........... . . ... ........... . ... . ... 116

II .

Description .. .... ... .. .. .. ........ . . .... .. ..... . . .. . . . ... ... .. .. . .... .. ... . .. . .. 117

III.

Regulatory Status ..... . .... .. ... . ....... .. . .... ..... .. . . . ... .... . .... .. . . ...... 117

IV.

Manufacture ... ........ . . ... . .. ......... .... ............ ... ... .. ........ . ....... 118

V.

Structure . ...... .. . ... . .. . ... ...... .... ..... ... .... . . .. . .. . . . . . ........ . .. .. .... 125

VI.

Properties .. . .. . ......... . .... . .......... .. .............. .. ................ .. ... 127 Physical Properties . .......... ...... . . .......... .. . . .. . ........ . .. . . . ... 127 A. Typical Physical Properties.. .. . .. ........ ... .. ... .. . .. .. . ... . . .. 127 I. Dry Powder Stability . . .. ... .. . .... .. .... .. . . ... ... . . ... .. ... . .. . 127 2. Types of Algin ... . ... .. . ..... .. ... .... ... . .. .. ... . . .. . . . ... .. ... 128 3. Solution Properties ... .......... .... .............. . ............ .. .. . .... 128 B. General Properties ........ . . . ............ ... ............ .. ....... 128 l. Solubility in Water (Optimal Conditions) . .... .. ........ .. . . .... 129 2. Solubility in Non-Optimal Aqueous Systems Which Contain Milk 3. Solids, Salt, Multivalent Cations, and Acids .. .. . . ... . . . . . . . ... . 131 Incomplete Hydration .... . .. . ............. ... ............ . . . .... 132 4. Preservation of Solutions .. .. ............. . ................. . .... 132 5. Viscosity . . ...... .. . . . . ......... . .. .. .. . .......... . ... . ... . . . . .. . .... . . . 132 C. Concentration . . . .. .. ..... . . .. .. ... . . ... . . .. .... . . . .... .. .. ...... 132 1. Molecular Weight and Calcium Ion Content .... ......... . . . . . . . 132 2. Rheology .. .. . ........... . . .. ............ .. . . . . ........... .. . . ... 132 3. Effects of pH. ............ .. ............... .. ........... ..... .. . . 133 4. Effects of Temperature . . .... .. . ........ . .. .... ........ . ... .. .. . . 140 5. Effect of Salt. .. ....... .. .. . .. ... . . ... ..... . .. .. .. .. ... .... .. .. .. 141 6. Interaction with Polyvalent Metal Cations (Particularly Calcium) . . . .... 141 D. Theory and Mechanism of Calcium/Algin Interaction ... . . ... ... 141 l. Properties of Calcium Reacted Alginate Systems ........... . .... 144 2. Ingredients Used to Control Calcium/Algin Interaction . ...... . .. 146 3. Calcium Retarding Agents and Methods . . .. .. .. . . . . ... . . 146 a. Calcium Salts . . ........ . .. .... .. . .. . .. .. .. ....... .. ...... 148 b. Acidulants ...... ... .. . .... . . . .... ... .. .. .......... . .. . . .. 148 c. Commercially Available Types of Algin ................. 148 d. Compositional Variations . ...... ... . . ........ .... . . ...... 152 e. Differences in Physical Form ..... .. .. . .. ... .. .. . . . .. . . . . 153 f. Reactions with Metal Ions ... .. . .. .... . ... .. .. . ......... . . .. .. . . 154 4. Compatibilities....... . ......... . ... . . . . . .............. . ........ . ... .. . . . 154 E.

DOI: 10.1201/9780429290374-10

116

Food Hydrocolloids

VII.

Use of Alginates in Food Systems (Applications) .............................. 154 A. Application of Calcium/Algin Interaction ............................... 154 1. Increased Viscosity.............................................. 154 2. Gels ............................................................. 157 a. Factors Which Influence Gel Formation and Properties ................................................ 157 b. Classification of Algin/Calcium Gels .................... 159 c. Diffusion Setting ........................................ 159 d. Internal Setting .......................................... 162 e. Temperature Influenced: Internally Set Gels ............. 168 3. Insoluble Polymers .............................................. 168 B. Other Alginate Salt Applications ............................ . .......... 173 l. Viscosity Building .............................................. 173 2. Film Forming ................................................... 174 3. Interactions with Other Molecules ............................... 175 4. General Colloidal Properties .................................... 175 C. Propylene Glycol Alginate Applications ................................ 176 l. Tolerance to Acidic Environments .............................. 176 2. Lipophilic Characteristics ....................................... 178 3. Other Uses for PGAs ........................................... 180 D. Alginates in Product Development. ..................................... 180 l. Information Gathering ........................................... 181 2. Evaluation and Modification .................................... 181 3. Designing Original Formulations ................................ 181

Acknowledgment ....................................................................... 182 References .............................................................................. 183

I. BACKGROUND Alginates, or algin, is a generic term for the salts and derivatives of alginic acid. This acidic polysaccharide or gum occurs as the insoluble mixed calcium, sodium, potassium, and magnesium salt in the Phaeophyceae, brown seaweeds. Alginic acid is a high molecular weight polysaccharide consisting of varying proportions of o-rnannuronic acid and L-guluronic acid; the variation being dependent principally upon the seaweed species from which the alginic acid was isolated. Brown seaweed has been used as a food for centuries but the discovery of algin did not occur until about 1880. This discovery was made in the U.K. by E. C. C. Stanford. 1•2 •3 Shortly thereafter, Krefting4 isolated pure alginic acid. Sustained commercial production first occurred in California, U.S., in 1929, and since that time, the uses of alginates have increased significantly. With the development of propylene glycol alginate in 1944, this derivative became an important water soluble gum for use in food applications. Commercially available alginates include sodium alginate, potassium alginate, ammonium alginate, and propylene glycol alginate. These products are produced in a range of mesh sizes, viscosity grades, and calcium levels to provide specific functionalities in food and industrial systems. Alginates are used by the food industry because of their unique colloidal properties which include thickening, stabilizing, suspending, film forming, gel producing, and emulsion

117 stabilizing. In the past few years, many review articles describing the chemistry and properties of alginates have been published, 5 ' 10

II. DESCRIPTION Algin is described quite simply in the Merck Index as, '"a gelling polysaccharide extracted from giant brown seaweed or from horsetail kelp or from sugar kelp. " 11 The National Forrnulary (NF) has descriptions for alginic acid and sodium alginate. They are listed in Official Monographs for NF XV. 12 Alginic acid is described as a '"hydrophilic colloidal carbohydrate extracted with dilute alkali from various species of brown seaweeds (Phaeophyceae).,. And sodium alginate is described as '"the purified carbohydrate product extracted from brown seaweeds by the use of dilute alkali. It consists chiefly of the sodium salt of alginic acid, a polyuronic acid composed of !3-0-mannuronic acid residues linked so that the carboxyl group of each unit is free while the aldehyde group is shielded by a glycosidic linkage. It contains not less than 90.8% and not more than 106.0 % of sodium alginate of average equivalent weight 222.00, calculated on the dried basis. " 12 The Food Chemical Codex (FCC) lists monographs for alginic acid, ammonium alginate, calcium alginate, potassium alginate, propylene glycol alginate, and sodium alginate. 13 It describes alginic acid as '"a hydrophilic colloidal carbohydrate extracted by the use of dilute alkali from various species of brown seaweeds (Phaeophyceae). It may be described chemically as a linear glycuronoglycan consisting mainly of 13-(1-+4) linked o-mannuronic and L-guluronic acid units in the pyranose ring form. It occurs as a white to yellowish white, fibrous powder. It is odorless and tasteless. '~ 13 To be strictly accurate, when L-guluronic acid is involved in a glycosidic linkage (1-+4) with either another L-guluronic acid unit or a D-mannuronic acid unit, (the number 1 carbon belonging to L-guluronic acid), the linkage is called a-(1-+4) instead of 13-(1-4). This is due to a convention of nomenclature. 14 Specifications for algin are similar in Food Chemical Codex and National Forrnulary monographs. However additional requirements are listed in the National Forrnulary: pH and acid value, only for alginic acid; starch, water insoluble substances and microbial limits, for both sodium alginate and alginic acid. The second supplement of the National Forrnulary, 15th Edition, increased both sodium alginate and alginic acid total bacterial count limits from 100 to 200 colonies/gram, effective 5/1/81. See Table 1 for actual specifications. The various algin products have been assigned Chemical Abstract Service (CAS) Registry Numbers, as indicated in Table 2. These registry numbers are unique numerical identifiers which may be used to search Chemical Abstracts (CA) for information on the substances they identify. 11 Since the system began operation in 1965, all documents referring to a substance are indexed by the appropriate CAS registry number and may be retrieved using it in a computerized literature search.

III. REGULATORY STATUS Ammonium, calcium, potassium, and sodium alginates are generally recognized as safe (GRAS) when used in accordance with good manufacturing practice, under 21 CFR 182.7133, 182.7187, 182.7610, and 182.7724, respectively. Propylene glycol alginate is approved as a food additive under 21 CFR 172.858 for use as an emulsifier, stabilizer, or thickener in foods in accordance with good manufacturing practice. 21 CFR 172.858 also requires that containers of the food additive be labeled ..propylene glycol alginate" or '"propylene glycol ester of alginic acid," and provide adequate directions for use. 15 Propylene glycol alginate is also approved in food processing as a defoarning agent, 21 CFR 173.340, as a defoarning, dispensing adjunct in coatings of fresh fruit, 21 CFR 172.210 and as a component in paper and paper board food packaging, 21 CFR 176.170 and 21 CFR 176.180.

118

Food Hydrocolloids

Table 1

ALGIN SPECIFICATIONS FCC Alginic acid Assay (dried basis)• Arsenic (as As) Ash (after drying) Heavy metals (as Pb) Lead Loss on drying •

NF

Sodium alginate

Alginic acid

Sodium alginate

91-104.5% 3 ppm, max. 4%, max. 0.004%, max.

90.S-106% 3 ppm, max. JS-27% 0.004%, max.

Absent 3 ppm, max. 4%, max. 0.004%, max.

90.S-106% 1.5 ppm, max. JS-24% (as is) 0.004%, max.

IO ppm, max. 15%, max.

IO ppm, max. 15%, max.

IO ppm, max. 15%, max.

JO ppm, max. 15%, max.

Based on an equivalent weight of 200 for alginic acid and 222 for sodium alginate. These "actual" equivalent weights are higher than the "theoretical" or calculated equivalent weights due to bound water.

(From Haug, A., Report 30, Norweigan Institute Seaweed Research, Trondheim, Norway, 1964.)

Table 2

CAS REGISTRY NUMBERS AND EEC DESIGNATIONS FOR ALGIN COMPOUNDS Algin Alginic acid Calcium alginate Calcium sodium alginate Potassium alginate Propylene glycol alginate Sodium alginate

CAS Registry No.

EEC No.

9005--32-7 9005--35--0 12698--40--7 9005--3C-l 9005--37-2 9005--3S-3

E-400 E-404 E-402 E-405 E-401

Algin is approved by the U.S. Department of Agriculture for use in the preparation of meat breading mixes and sauces, and poultry products under 9 CFR 318.7 and 9 CFR 381.147, respectively. It may be used in sufficient amounts for the purpose of stabilizing these products. The Environmental Protection Agency (EPA) has exempted both sodium alginate and propylene glycol alginate from the requirement of a tolerance, under 40 CFR 180.1001, relating to pesticide formulations, because of EPA's finding that these two alginate products involve no hazard to public health under currently prevailing conditions of use. The edible salts of alginic acid, as well as propylene glycol alginate, may be used in many standardized foods, if regulations contain provisions for alginates by name, or permit •~safe and suitable'~ ingredients as stabilizers. The joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Expert Committee on food additives has issued specifications for the identity and purity of alginates. They have also issued Acceptable Daily Intakes (ADI) for alginic acid salts (50 mg/kg of body weight/day) and for propylene glycol alginate (25 mg/kg/day). Algin compounds appear on the European Economic Community's (EEC) stabilizer/emulsifier list, Annex I. 15 The •~E" numbers are listed in Table 2. Table 3 gives a summary of the countries permitting the use of alginates as of January 1982. Since regulations vary greatly between countries, individual regulations must be consulted to determine the details and limitations of each approval. 16

IV. MANUFACTURE As mentioned earlier, algin occurs in all of the species of Phaeophyceae, (brown seaweeds)

119 Table 3

COUNTRIES PERMITTING THE USE OF ALGINATES Country Argentina Australia Austria Belgium Brazil Canada Chile Colombia Denmark Finland France West Germany Greece Hong Kong Ireland Italy Iraq Japan Jordan Luxembourg Malaysia Mexico Netherlands New Zealand Norway Oman Phillippines Singapore South Africa Spain Sweden Switzerland Taiwan Turkey Yugoslavia United Kingdom United Arab Emirates United States Venezuela

Note: X

Alginates

PGA

X X X X X X X X X X X X X X X

X X X X X X X X X

X

X X X X X X X X

X X X X X X

X

X X X X X

X X X

p R

X X X X X X X

X X X X X

X X X

X X X X X X

X X X X

= Approved

= Not approved R = Approval very restrictive P = Petition pending

-

that have been investigated. However, only a few species of brown algae are used for the commercial production of algin. These species are Macrocystis pyrifera, Ascophyllum nodosum, Laminaria hyperborea, and L. digitata. Several other species, e.g., Ecklonia and Eisenia, have been used but they are of minor importance commercially. The map in Figure 1 shows the areas which support the growth of brown seaweeds. M. pyrifera is a giant kelp which grows in the offshore waters of the coast of California, and Baja, California, and Mexico. Other stands occur around the coastline of Tasmania, Australia, and off the coast of southern Argentina. However commercial harvesting occurs only off the coast of the North American continent. A schematic of M. pyrifera is shown

..

~

·,c

o~t::,;o~

d~~~

~~~~ - .. -..' ._

~ ~='

~-

1'"'/ n>

~

~

.

j

~ ~

i

a:

La .. ---;_ La

--

ff

_a

'

t~~-

~

~

M

:\9 in 1963 and 1964 by partial acid hydrolysis of the neutral reduced alginic acid and isolation of crystalline mannosylgulose. Therefore, the state of the art in 1964 indicated that alginic acid was a polyglycuronan containing D-mannuronic acid and L-guluronic acid with both uronic acids occurring in the same molecule and being linked through carbons 1 and 4. Haug et al., 40 .-4 1 showed the presence of three types of polymer segments in alginic acid using mild acid hydrolysis. The principal component of one segment is o-mannuronic acid, the principal component of the second segment is L-guluronic acid, and the third segment contains alternating D-mannuronic acid and L-guluronic acid residues. The structure and conformation of o-mannuronic acid and L-guluronic acid, together with a schematic representation of the polymer segments, are shown in Figure 6. Haug and Larsen 42 have used improved techniques for acid hydrolysis separation, and analysis of alginic acid components to determine the accurate composition of alginic acid from different species of brown seaweeds. The composition of alginic acid obtained from the brown algae used commercially is shown in Table 4. 5 ~42 Alginic acid from the stipes (stems) of L. hyperborea contains a high proportion of guluronic acid, whereas the alginic acids from the other species contain approximately the

126

Food Hydrocolloids

HO OH

13-0-MANNURONIC ACID

a

-L-GULURONIC ACID

...-M-M-M-M-M-M-M-M-...

...-G-G-G-G-G-G-G-G-...

POL YMANNURONIC ACID SEGMENT (polymannuronan)

POL YGULURONIC ACID SEGMENT (polyguluronan)

...-M-G-M-G-M-G-M-G-... ALTERNATING SEGMENT FIGURE 6. The structure and conformation of o-mannuronic acid and L-guluronic acid, together with a schematic representation of the polymer segments.

Table 4 MANNURONIC ACID (M) AND GULURONIC ACID (G) COMPOSITION OF ALGINIC ACID OBTAINED FROM COMMERCIAL ALGAE Species Macrocystis pyrifera Ascophyllum nodosum Laminaria digitata Laminaria hyperborea (stipes) Ecklonia cava and Eisenia bicyclis

Mannuronic acid

Guluronic acid

(%)

(%)

M:G ratio

M:G ratio range

61

39

1.56

65

35

1.85

1.40-1.95

59 31

41 69

1.45 0.45

1.40-1.60 0.40- 1.00

62

38

1.60

same proportions of mannuronic acid and guluronic acid with mannuronic acid predominating. The variation in the mannuronic acid to guluronic acid ratio is also shown. This variation depends upon the season, place of collection, and part of the alga from which the alginic acid was isolated. Table 5 shows the proportions of the three polymer segments in alginic acid samples extracted from Macrocystic pyrifera, Ascophyllum nodosum, and Laminaria hyperborea, respectively. These data were obtained by Penman and Sanderson43 using the partial acid hydrolysis and fractionation technique developed by Haug and co-workers, 40.4 1 followed by proton magnetic resonance spectroscopy. The alginic acid from Laminaria hyperborea contains a high proportion of polyguluronan, an intermediate amount of alternating segments, and a small proportion of polymannuronan segments, whereas the alginic acids from Macrocystis pyrifera and Ascophyllum nodosum are essentially identical in containing approximately the same amount of polymannuronan segments and alternating segments, and small amounts of polyguluronan segments. The

127 Table 5 PROPORTIONS OF POLYMANNURONAN, POLYGULURONAN, AND ALTERNATING SEGMENTS IN ALGINIC ACID FROM DIFFERENT SOURCES Source

Macrocystis pyrifera Ascophyllum nodosum Laminaria hyperborea

Polymannuronan

Polyguluronan

Alternating

40.6 38.4 12.7

17 .7 20.7 60.5

41.7 41.0 26.8

Table 6 TYPICAL PHYSICAL PROPERTIES Alginic acid

Moisture content Ash Powder color Sp. gravity Bulk density (lb/ft') Browning temp . (°C) Charring temp . (°C) Ashing temp. (9 C) Heat of combustion (cal/g)

7% 2% White

160 250 450 2.8

Refined sodium alginate

Propylene glycol alginate

13% 23 % Ivory 1.59 54.62 150.0

340, 460

480.0 2.5

13% max . 10% max. Cream 1.46 33 .71 155 220 400 4 .44

(From Anon., Kelco algin. Kelco, Division of Merck & Co., San Diego, 1976, 11.)

difference in structure between the alginic acid isolated from L. hyperborea and from M . pyrifera and A. nososum, respectively, accounts for the differences in functionality.

VI. PROPERTIES A. Physical Properties 1. Typical Physical Properties The typical physical properties of alginic acid, a refined food-grade sodium alginate and a propylene glycol alginate are listed in Table 6. The moisture content of these three types of algin varies , depending on the relative humidity of the environment. Figure 7 illustrates this fact by showing equilibrium moisture curves for four alginates. 45

2. Dry Powder Stability Alginic acid , like other ''' free acid ''' forms of polysaccharides, has limited stability, as measured by viscosity of the neutralized material, and degrades at rates proportional to the ambient temperature. If stored at 40°F (4.4°C), or cooler, the material will change less than 20% to 30% over 12 months. If frozen, alginic acid remains essentially unchanged after one year. It should be mentioned that this loss of viscosity is not a disadvantage for its major application as a tablet disintegrant, since there seems to be no relation between disintegrant activity of the alginic acid and viscosity of the neutralized material. Alginates have excellent dry-storage stability at moderate temperatures [75°F (24°C) , or lower] . At higher temperatures , after one year, the dry-storage stability decreases for alginate salts and propylene glycol alginates tend to become less soluble. In view of this , alginates should be stored in a cool, dry place (Table 7) .

128

Food Hydrocolloids

2s----...--------.------,,------,-----, ,-----,,-----,

0

m;---"-----"-----i----....,j---------....,j-----~~--~

0

10

30

20

50

40

60

70

80

Percent relative humidity

FIGURE 7. Equilibrium moisture curves for three typical kinds of alginates. (From Cottrell, I. W. and Kovacs, P., in Handbook of Water-Solule Gums and Resins, Davidson, R. L. , Ed., McGraw-Hill, New York, I980, Chapt. 2. With permission.)

Table 7 EFFECTS OF STORAGE TEMPERATURE ON VISCOSITY AFfER ONE YEAR

Medium viscosity alginate Low viscosity alginate High viscosity propylene glycol alginate Low viscosity propylene glycol alginate

Initial

3S8F (1.~C)

7S8F (24°C)

420 cP

410 cP

380 cP

27

26

400

26 236

115

67

(From Anon., Kelco algin, Kelco Division of Merck & Co., San Diego, 1976, 19.)

3. Types ofA/gin Alginates are produced in many forms, varying in molecular weight, calcium content, particle form (i.e., granular or fibrous), particle size, and mannuronic acid to guluronic acid ratio. The propylene glycol alginates can also vary in the degree of esterification. B. Solution Properties 1. General Propenies Physical properties of a 1% distilled water solution of a typical refined food-grade sodium alginate, a propylene glycol alginate, and alginic acid, are compared in Table 8. Alginate salts bind water very strongly, due to the large number of carboxylate anions they contain. When the number of carboxylate anions decreases, which occurs in the case of propylene glycol alginates, water binding power also decreases. Temperature plays a role as well and water binding power is greatest at moderate to cool temperatures (below 90°F or 32°C). At these temperatures alginates bind water very efficiently, even under extremely high shear conditions.

129 Table 8 ALGIN SOLUTION PROPERTIES Sodium alginate

As a I% solution (distilled water) Heat of solution (cal/g) Refractive index (20°C) pH Surface tension (Dynes/cm) Freezing point depression (°C) Zsigmondy gold no.• • •

0.080 1.3343 7.5 62.0 0.035 75

Propylene glycol alginate

0.090 1.3343 4.3 58 0.030 40

Alginic" acid

0.090 2.9 53 0.010

A true dispersion, not a colloidal dispersion The Zsigmondy gold number is a measure of the efficiency of a gum as a protective colloid. The Zsigmondy gold No. = milligrams of protecting colloid which is barely insufficient to prevent a color change (due to flocculation) of JO me of a red• gold solution to violet, when I me of a 10% NaCl solution is added. 48

(From Anon., Kelco algin, Kelco Division of Merck & Co., San Diego, 1976, 11. With permission.)

2. Solubility in Water (Optimal Conditions) Alginic acid is essentially insoluble in cold or hot water, but it does swell quite strongly. This is the basis of its use as a powerful tablet disintegrant. Alginic acid salts (K, Na, NH4 +- Ca, and Na + Ca), and propylene glycol alginates are soluble in cold or hot water and form stable solutions, due to repulsion from carboxylate anions. There is no true solubility limit but at high concentrations solutions are pastes rather than liquids. Magnesium salts are also soluble, but calcium alginate is insoluble in water under neutral pH conditions, as are most other metal salts. Since the alginates are water soluble with the exception of alginic acid and calcium alginate, they will tend to clump when added to water unless suitable precautions are taken. This is generally true of all hydrocolloids, especially those which will hydrate in cold water. An extremely high percentage of all hydrocolloid technical problems, can be traced to improper dispersion, which almost inevitably leads to incomplete hydration and inefficient functionality. This becomes particularly critical with alginates, which often are used in carefully balanced systems depending on sequential interactions, which in turn depend on different solubility rates. This effect will be illustrated in a later section. There are basically four methods of obtaining proper dispersion for any hydrocolloid: physical methods, liquid dispersion methods, dry material dispersion methods, and particle size control. Physical methods depend simply on force to physically separate each gum particle so it may individually hydrate. In a dispersion funnel, such as that shown in Figure 8, particles are separated as they are drawn into the violently mixed water (Venturi effect), which exists inside the educator valve to which the funnel is attached. Once the dispersed gum enters the mixing tank it still must be efficiently agitated with a high speed mixer until the polymer has hydrated. If higher shear, efficient mixing is available, the dry alginate powder may be slowly added to the mixing water, relying on the high shear to break up any clumps which might initially form. Liquid dispersion methods are very effective and efficient, particularly when a '"nonsolvent'~ is available as part of the food formulation (e.g., vegetable oil in salad dressings). These methods depend upon using enough of the liquid to make a pourable slurry. Generally 3 to 5 parts of liquid '"non-solvent" per part of dry alginate are needed. Some of the more common liquids used are: vegetable oils, propylene glycol, glycerol, alcohol, flavor oils, melted fats, com syrup, and liquid sugars. Whenever using materials which contain sub-

130

Food Hydrocolloids

FUNNEL

HIGH-SPEED MIXER 1700 R.P.M.

MAKEUP WATER INLET FINAL WATER LEVEL

WATER LEVEL --,,,,. ______ -INITIAL

FIGURE 8.

DRAIN

Typical installation of a dispersion eductor and funnel.

stantial amounts of water, such as liquid sugar, the alginate must be quickly dispersed and immediately added to the mixing water, it must not remain in the syrup for too long or it will substantially thicken and be difficult to pour. Good mixing is still necessary to efficiently solubilize the alginate. Time may be substituted for good mixing, as long as proper dispersion of the alginate particles is achieved. For example, if alginate particles are well dispersed in water (by adding a propylene glycol/alginate slurry to water), after sitting in the water for several hours without mixing, only gentle agitation is necessary to produce a homogeneous solution. Dry material dispersion methods depend on physical separation of hydrocolloid particles due to dilution with other dry ingredients such as sugars, flour, milk solids, etc. (Note: It is generally not advisable to blend hydrocolloids with salt (NaCl), since it will hinder solubility). Slow, gradual addition of the dry blend, 5 to 10 parts of dry ingredients per part of hydrocolloid, for example, to well-agitated water at the point of maximum mixing, is still required to obtain optimum dispersion and hydration. The care taken blending the hydrocolloid thoroughly with the dry ingredient (e.g., sucrose) and adding the blend to liquid will determine the degree of success with this method.

131

The particle size control method is based on the following relationships: The tendency of water soluble materials to clump is directly related to particle size - i.e., the smaller the hydrocolloid particle size, the greater its tendency to clump and the larger the particle size, the Jess they tend to clump. Therefore, through various processes of agglomeration or other means of mesh size control, coarse mesh products can be produced which may be added directly to water without clumping, even under relatively low-shear mixing conditions. However, along with this relationship of particle size to dispersibility is the corresponding relationship to solubility rate: The smaller the particle size, the more rapidly it will hydrate (assuming good dispersion) and the larger the particle size, the more slowly it will hydrate. Therefore, in choosing an alginate for a particular application, one must determine all the important requirements. If rapid solubility under minimal agitation is the main requirment (as in a dry mix breakfast drink to be stirred with a spoon, e.g.), the smallest particle size product should be used and particular care should be taken to insure that a uniform dry mix blend is produced to achieve maximum dispersibility. 3. Solubility in Non-Optimal Aqueous Systems Which Contain Milk Solids, Salt, Multivalent Cations. and Acid Generally speaking, cations, solvents, or other polymers, which often react with dissolved hydrocolloids in very useful ways (e.g., to form gels or precipitates), if present while the hydrocolloids are hydrating, can compete for available water and reduce the hydration rate or strongly inhibit the solubility of the hydrocolloids. Calcium ions will react with dissolved alginates to form gels or completely insoluble calcium alginate. The presence of sufficient Ca++ ions in the aqueous environment can prevent hydration of an alginate, however. Consequently, nearly all of the free Ca++ ions in cold milk must be sequestered before sodium alginate will dissolve in that environment. Sodium alginate added to unsequestered cold milk will not hydrate even though the milk is subsequently heated. It can be hydrated, however, if added directly to boiling milk. Propylene glycol alginates can be added to unsequestered cold milk and will hydrate when heated. Low levels ( < 0.5%) of monovalent salts, such as sodium chloride, have little effect on the solubility of alginates The hydration of propylene glycol alginates can be inhibited by high salt concentrations. If possible, salt should not be added to the system until after the algin is hydrated. It is possible to hydrate alginates in quite acidic environments if propylene glycol alginates or ••Jow residual calcium" alginates are used and the concentration of metal ions is low. Hydrogen ions (low pH systems) will slow the alginate's hydration and propylene glycol alginates will usually be required if the pH is below 4.0. Non-solvents, such as ethanol (as much as 40%) can be tolerated when added slowly to alginate solutions. The presence of these non-solvents while dissolving alginates can significantly inhibit their hydration, however. Other substances which compete with alginates for available water (e.g., sugar, dextrins, com syrup solids, starches, gums, proteins) generally necessitate increased mixing time and efficiency in order to achieve complete hydration of the alginates. Alternatively, concentrated presolutions of the alginate may be prepared in water to circumvent potential hydration problems. It is particularly important to recognize the effect caused by some ingredients because many alginate applications are based on sequential reactivity, which, in tum, is based on sequential hydration of the formula ingredients. Quite often other important ingredients (such as calcium salts, sequestrants, or acidulants) may also be affected by a non-solvent (e.g., alcohol). Because of these variables, it is often difficult to put forth specific recommendations, and many times a certain amount of trial and error is necessary to achieve desired results. The

132

Food Hydrocolloids

more one understands the various components, however, the better chance for success with a fewer number of trials. For this reason, we will discuss not only the alginates and their properties but also calcium salts, acidulants, and sequestering agents commonly used for algin systems. 4. Incomplete Hydration Usually complete hydration (solubility) of an alginate is desirable, but there are occasions when something less than complete hydration is beneficial. One example is the use of algin with borate salts in a dental adhesive compound. In this instance the borate inhibits complete alginate hydration. The partially hydrated alginate is very sticky, producing a desirable adhesive effect. Another example is encountered in a fabricated food product. By incorptrating another hydrocolloid, which competes with the alginate for water, significantly stronger gels are obtained. 49 Due to this competition for water, the alginate probably can not fully hydrate and still has some residual hydrogen bonding of polymer chains from the dry state. When it is reacted with Ca++ ions under these conditions, the effect is that of a '"higher molecular weight" alginate (i.e., a stronger gel forms). A plot of viscosity vs. elapsed time (Figure 9) shows that alginates, as well as most other hydrocolloids, go through a maximum viscosity area during hydration, then decrease and level off. This phenomenon is explained quite well by Whistler. At complete hydration each molecule is entirely enveloped by water molecules. Before this state is reached some of the molecules still have points of attachment to other molecules, which produces greater internal '"solution friction" (i.e., viscosity) than does the '"completely'~ hydrated state. 50 5. Preservation of Solutions Alginate and other hydrocolloid solutions are subject to bacterial action and do require suitable preservatives if they are stored for prolonged periods. Following is a list of food preservatives that are used successfully: benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, methylparaben, and propylparaben.

C. Viscosity I. Concentration The relationship of viscosity to concentration is as shown in Figure 10. 2. Molecular Weight and Calcium Ion Content Both molecular weight and calcium ion content will affect the viscosity observed. In order to compare alginates using viscosity measurements, sequestered viscosities should be used, otherwise misleading conclusions could be drawn. The higher the sequestered viscosity (e.g., I% alginate plus I% sodium hexametaphosphate) the higher the molecular weight of that alginate. Viscosity for a 1% alginate solution may range from 10 cP to several thousand cP (even a soft gel for sodium-calcium alginate) Figure 11 . 3. Rheology Aow properties of sodium alginate solutions and propylene glycol alginate solutions are concentration dependent. The higher the concentration, (2% and higher) the more shear thinning these solutions exhibit, while at low concentrations (less than 1%) the same alginate in solutions are more Newtonian as seen in Figures 12, 13, and 14. At very high shear rates (in excess of 100.000 sec=- 1) alginate solutions tend to be Newtonian. The presence of calcium ions tends to increase shear-thinning characteristics and reduce Newtonian character. Low molecular weight alginates are more Newtonian in flow, and conversely, high molecular weight alginates are more thixotropic and shear thinning. Pro-

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pylene glycol alginate solutions, especially in concentrations above l %, tend to be quite thixotropic. Consequently, by choosing various types of alginates (high calcium, low calcium, high molecular weight , low molecular weight , or propylene glycol alginate) at specific concentrations, quite a wide range of rheological effects can be achieved.

4 . Effects of pH Viscosity is affected by pH because the ready interconversion of carboxylate anions (e .g., sodium alginate) to free carboxyl groups (i.e., alginic acid) occurs as the hydrogen ion concentration increases (see Figure 15). The pKa values for alginic acid may range from

134

Food Hydrocolloids

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3.4 to 4.4 depending on the type of alginate and the salts present in the mixture .7 As a rough approximation, 50% of the carboxyl groups will be protonated at pH 4.0. When the carboxyl groups are fully ionized, generally at pH values near 5, the alginate chains repel each other and provide stable solutions, which do not change much in viscosity between pH values of 5.5 to I 1. When the pH drops sufficiently to make residual calcium more available to react with the alginate , and/or to start protonating the carboxyl groups, viscosity will rise and gelation may occur.

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Concentration% 25°C, Brookfield LVF Viscometer@ 60 r.p.m. FIGURE 11. Effect of sequestrant (sodium hexametaphosphate) on the viscosity of a sodium-calcium alginate solution. (From Cottrell, I. W. and Kovacs, P., in Handbook of Water-Soluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill, New York, 1980, Chapt. 2. With permission.)

Protonation of the carboxyl groups also reduces electrostatic repulsion from carboxylate anions, allowing the alginate molecules to interact more easily through hydrogen bonding. Hence the internal friction of molecules colliding and '"sticking" to each other via hydrogen bonding produces higher viscosity. Under proper conditions a gel can be formed. This is called an "acid gel", to distinguish it from the calcium/alginate gel. The pH at which viscosity increases or gelation begins depends on the amount of calcium available to the

136

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system. Figure 15 demonstrates that sodium alginates with significant (approximately I%) residual calcium content (medium-viscosity sodium alginate) exhibit gelation characteristics near pH 5 while those alginates with minimal calcium content do not exhibit this characteristic until the pH drops below 4. Several conditions are necessary in order to form '"acid gels" : 1. 2. 3.

Small amounts of calcium (less than 100 ppm) must be present in the system. Usually indigenous calcium, from the alginate and/or other ingredients, is sufficient. The higher the calcium concentration, the more rapidly acid gels will form. The alginate concentration should be a minimum of 0.5% (on the water basis). Gel strength increases with increasing algin concentration, other conditions being equal. Gels have been successfully produced at pH values between 2.8 and 4.0. When only the pH is varied, the highest gel strength generally is obtained at pH 3.6

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Various characteristics of alginate acid gels are listed below: 1. 2.

These gels are perceptibly weaker than algin/calcium gels (approximately one-half the gel strength, at equal levels, when measured on a Bloom Gelometer). Acid gels are unstable to heat and will gradually lose gel strength with time, even at

139

3. 4. 5. 6.

room temperature. At refrigerated temperatures (4 0. 7%, based on the water phase). Propylene glycol alginates do not form acid gels.

The reset characteristics of acid gels can be demonstrated by preparing the following grape juice spread formulation (a product similar to grape jelly). After setting into an acid gel, the spread may be extruded through a jelly pump into yeast raised donuts. The disrupted gel will reset into a delicate gel upon cooling (freezing or refrigeration).

GRAPE JUICE SPREAD WITH ALGIN 56 Composition

Sugar Water Grape juice solids Citric acid (anhydrous) Sodium citrate dihydrate Refined sodium alginate (KELCOGEL ® HV - Kelco Division of Merck & Co., Inc.) Formulation

Sugar Grape juice (16.5% solids) Water (adjust to 658 brix) 50% citric acid solution Sodium citrate dihydrate Refined sodium alginate (KELCO-GEL® HV)

Percent of finished jelly

57.47

33.86 7. 19

ca. 0.63 0.43 0.42 100.00 Percent (ca.)

54.60 41.37 ca. 2.42 ca. 0.80 0.41 0.40 100.00

Procedure - add sodium citrate to grape juice and heat to 150~F (65.5°C). Blend alginate with 10 parts of dry sugar and add slowly to the stirred juice. Heat to 180°F (82°C) and tum off heat source. Add dry sugar and mix to dissolve. This should reduce the temperature to about 150@F (65.5@C)_ Adjust brix to 65° with water and add 50% citric acid solution to pH 3.6. Pack and cool immediately.

The acid gel system may also be used to produce a cold processed pie filling which is freeze-thaw stable. Freeze-thaw stable lemon pie tilling (cold preparation)57 -A refined sodium alginate (gelled by acid addition), with xanthan gum and instant starch, produces a pie filling which requires no heat processing. This filling can be mixed for an hour or more without damaging the final texture and it is freeze-thaw stable. Final textural characteristics can be easily modified by adjusting the levels of starch and/or dextrins to produce desired '"light" or '"heavy'~ body.

140

Food Hydrocolloids Ingredients Water Sugar, refined granular Malto dextrin, 10 dextrose equivalent (DE) Instant pregelatinized starch Com syrup solids, 42 dextrose equivalent Dried egg yolk Lemon juice power # 10 Refined sodium alginate (KELCO-GEL® HVKelco Division of Merck & Co. Inc.) Sodium hexarnetaphosphate Titanium dioxide Xanthan gum (KELTROL® - Kelco Division of Merck & Co., Inc.) Salt FD&C yellow #5

Percent 63.7 17.9 7.9

3.5 3.0 2.0 1.0 0.6

0.12 0.1 0.1 0.0793 0.0007 100.00

Note: 50% citric acid solution to pH 3.6 (use approximately . 78g/100g filling).

Procedure - dry blend alginate and xanthan gum with IO parts sugar. (Note: titanium dioxide and sodium hexametaphosphate also may be dry blended with sugar at this point.) Slowly add dry blend to well agitated water. Mix for 5 to IO min to hydrate the gums. Blend remaining dry ingredients and add to agitated mixture; take care to prevent lumping of instant starch. Mix for an additional IO min or until mixture is homogeneous. Adjust pH to precisely 3.6 with 50% citric acid solution. Pour into prebaked pie shells while continuing gentle mixing of the pie filling. (Note: if filling of pie shells must be delayed, continue gentle agitation of the filling to prevent gelation in the batching tank.)

Propylene glycol alginates have good stability in acidic systems of pH 3.0 or higher, but should not be used in alkaline environments, since they will undergo saponification at pH values above 6.7. 5. Effects of Temperature As with most polysaccharides solutions, the viscosity of alginate solutions decreases with increased temperature. Over a limited range, the viscosity of an algin solution decreases approximately 12% for each JQ@F (5.611C) increase in temperature. 58 Propylene glycol alginates can exhibit marked viscosity increases in certain food products at temperatures below 50°F (10°C) and at concentrations greater than 0.2%. This effect is probably due to a combination of factors, such as soluble solids, pH, and calcium content of the food product, as well as the thixotropic nature of propylene glycol alginates. An alginate containing very low levels of residual calcium (i.e. 0.5%, or less) may be frozen and then thawed without change in its appearance or viscosity. Solutions of alginates with sufficient residual calcium (I% or more calcium, on the basis of the dry alginate), however, may show considerable -viscosity increase or even gelation upon refrigeration or freezing. Once this viscosity increase or gelation has occurred, it is stable to subsequent heat, i.e., it is essentially irreversible. 59

141

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Algin/calcium interaction (simplified concept).

6. Effect of Salt The short term effect of monovalent salts on the viscosity of alginate solutions is minimal with the exception of high calcium alginates, which can lose a considerable amount of their viscosity as the salt concentration increases. Viscosity of alginate solutions may increase as the salt concentration increases. Viscosity increases are common during prolonged storage in high salt systems. '"The salt effects vary with the source of the alginate, the degree of polymerization, the concentration in solution, and the type of monovalent salt used. " 60 In highly concentrated salt solutions ion exchange would be expected, which could have a profound effect on viscosity, if calcium ions and sodium ions were exchanged. The effect of calcium ions will be considered later. Most polyvalent cations will react with and, in some cases, gel algin polymers. As the polyvalent ion content in solution is increased, thickening, gelation, and finally precipitation will occur. Magnesium is atypical because it does not gel algin polymers, despite its close relationship to calcium. D. Interaction with Polyvalent Metal Cations (Particularly Calcium) The most useful and unique property of alginates is their ability to react with polyvalent metal cations, specifically calcium ions, to produce; (I) higher viscosity than from the algin solution itself; (2) gels; or (3) insoluble polymers.

1. Theory and Mechanism of Calcium/A/gin Interaction Calcium ions interact strongly with algin. Whether the effect is increased viscosity, gelation, or insoluble polymers, the mechanism is the same. Figure 16 shows a simplistic way to view alginate association as a function of calcium divalent cations interacting with monovalent carboxylate anions. The interaction is now known to be considerably more complex than this, 6 1t66 but to discuss the pragmatic technology involved in utilizing this reaction, the Figure 16 simplification will be sufficient. As calcium continues to react with algin molecules, a threedimensional gel network is formed, as shown in Figure 17. Rees suggested that the formation of this three-dimensional gel network involves a cooperative association of polyguluronic acid segments (poly G blocks) and possibly poly= mannuronic acid segments (poly M blocks) with calcium ions bound between associated segments of the polymer chains.

142

Food Hydrocolloids

FIGURE 17. Structure of calcium alginate gel (proposed). (From Cottrell, I. W. and Kovacs, P., in Handbook of Water-Soluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill, New York, 1980, Chapt. 2. With permission.)

In later work, utilizing circular dichroism, Morris et. al. showed that calcium ions react preferentially with poly G blocks before reacting with poly M blocks. 65 Probably the alternating segments of an alginate polymer chain do not participate directly in the gelation with calcium but serve to join the associated segments and hence provide a three-dimensional network of chains within the gel. Hydrogen bonding is undoubtedly involved in this reaction also, but heat does not reverse the reaction as with more purely-hydrogen bonded systems. Probably calcium ions pull the alginate molecules together by ionic attractions, then hydrogen bonding also occurs, in a zipper-like fashion, causing the interaction to be stronger than either ionic or hydrogen bonding alone. As algin molecules associate, the resultant "higher molecular weight" causes an increase in solution viscosity (at low levels of available calcium ions), gelation (at higher levels of calcium ions), and can finally produce insoluble calcium alginate polymers (Figure 18) as the stoichiometric calcium level (at 7.2% of the weight of sodium alginate) is approached. It only requires 30% of this calcium level, or 2.2% of the sodium alginate weight, to produce gels, and less than 15% (I. 1% of sodium alginate weight) of the stoichiometric calcium level to produce thickened, flowable solutions. 60 Even propylene glycol alginates, with relatively low degrees of esterification, can be reacted with calcium ions (Figure 19) to produce higher viscosity, weak gels, and insoluble polymers. Generally a degree of substitution of 0.5 or less would be necessary to observe these effects.

143

Gelation

/

Precipitation

[cross-Linking Agent]--• FIGURE 18.

Effect of calcium or hydrogen ions on viscosity of a sodium alginate solution.

Alginate gels produced by interaction with calcium ions are dynamic systems; i.e., gel strength usually increases with time (over several hours). There are several reasons for this phenomenon: l. 2. 3.

When solutions of alginate and ionized calcium contact each other an immediate gel is formed at the interface. Further gelation depends on diffusion of calcium ions through the gel membrane, which requires time. When slowly soluble calcium salts are used to form alginate gels, the gradual release of calcium results in gradual strengthening of the gel. As algin molecules are drawn closer to each other through interactions with calcium ions, hydrogen bonding is made easier and probably becomes a greater factor in consolidation of the gel.

Consequently, it is essentially impossible to stop the interaction in time, once an alginate solution and soluble calcium ions have been mixed. The reaction will continue until equilibrium is reached. Even then, if the temperature is reduced significantly, additional, irreversible interaction will occur. 59

144

Food Hydrocolloids

0

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Propylene glycol alginate/calcium interaction (simplified concept).

2. Properties of Calcium Reacted Alginate Systems Because of the high degree of interaction involved in the calcium algin reaction, these systems have excellent heat stability. The degree of heat stability is greatest for the most highly reacted materials. When this interaction is used to produce high viscosity, that viscosity will not decrease nearly as much upon heating as one would expect from an algin system not reacted with calcium or other hydrocolloid solutions. Gels are also non-melting and can be made very stable and free of syneresis. Like other gels, algin gels have both properties of liquids and solids. For example, alginate gels can be as much as 99% water and as little as 0.5% algin, yet exhibit solid characteristics of shape retention and resistance to stress. A gel can be viewed as physically immobilized water, but should not be considered an absolute moisture barrier. Rather, it is more like a semipermeable membrane, through which low molecular weight, water soluble molecules can diffuse. Hence water can move in or out of the gel, depending on the environment and existing equilibrium conditions. Gels also possess a vapor pressure, like liquids, and will conduct an electric current. Generally, once a gel has been produced by the calcium/algin interaction, subsequent mechanical disruption will physically break down the gel, causing it to lose structural integrity. Usually this process is irreversible and a gel will not reform. When the calcium/ algin interaction is used to produce high viscosity, extremely high shear (e.g., homogenization, Waring blender, etc.) may also cause an irreversible loss in viscosity. It is possible, however, to formulate a system so that the algin concentration and calcium ion concentration are balanced to produce reversible gels - gels which can be pumped and will then reset when shear stress is removed. These gels would be in the region referred to as thixotropic gels on Figure 20. McDowell explains this phenomenon as a homeostasis between the calcium stabilization of G blocks from different molecules and repulsion of those parts which are still neutralized by sodium (therefore highly ionized). ••we can thus visualize a balance between aggregation and repulsion which at low levels of calcium allows relative movement of the molecules as a result of thermal agitation or very small shearing forces, and at intermediate levels allows the development of enough aggregation to resist separation of the molecules by small shearing

145

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w Wu,

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6

oa: WO.. U>z :::E :::, C

-z 0 :::,

4 Tetrasodium Pyrophosphate

...lo c( 0.. 0 :::E

u,o

:::E 0 c(

2

a:

C,

6

7

8

9

pH

10

11 12

AGURE 21. The sequestration of calcium by sodium polyphosphates using the oxalate ion as the calcium precipitant. (From Van Waz.er, J. R., in Symposium: Phosphates in Food Processing, Deman, J.M. and Melnychyni. P., Eds., AVI Publishing, Westport, Conn., 1971, 10. With Permission.)

Table l O also shows that some salts are available in different degrees of hydration.

c. Acidulants

Table 11 lists acids and acid precursors commonly used in alginate food systems. These acids have been arranged in order of decreasing absolute solubility within the various groups, namely, liquids, solids, slowly soluble acids, and acid precursors. A few comments pertaining to uses with alginate systems are also included to aid in deciding which acid to use. Most of the data was obtained from technical references_u.72

d. Commercially Available Types of Algin Alginic acid derivatives are available in various forms. The variations can be categorized as differences in composition or physical form.

Table 10 CALCIUM SALTS USED TO GEL ALGINATE FOOD SYSTEMS Solubility In water Calcium salt Calcium chloride Calcium acetate (monohydrate) Monucalcium phosphate monohydrate, calcium phosphate monobasic, calcium biphosphate, acid calcium phosphate, primary calcium phosphate, ti calcium superphosphate 11 , regent I2XX' Monocalcium phosphate (anhydrous) V-90'

Formula

M.W.•

% Ca.

Cold

Hot

Cost as of 4/80

Common uses

Low High

Calcium bath or spray Calcium bath or spray

CaCI, Ca(CH 3COO),·H,O

110.99 176.18

36. 11 22.75

40% 27%

CaH 4(PO4 ) 2·H,O

252 .09

15 .90

Very soluble with decomposition to free H,PO, and di- or tri-basic salts

Low

Very rare; used mainly in baking as a leavening agent

CaH.(PO,) 2

234

17 . I

Low

Very rare; used mainly in baking as a leavening agent

Calcium lactate Calcium gluconate

C,H, 0O 4Ca,5H,O c ,,H,,O,,Ca·H,O

308 .30 448.39

13.0 8.94

Very soluble with decomposition to free H3PO4 and di- or tri-basic salts 5% 3.2%

5% + 16.6%

Med. Med.

Calcium sulfate dihydrate (pure precipitated), gypsum, terra alba" Calcium sulfate anhydrous (snow white filler")

CaSO,2H 2O

172.18

23 .28

0.27%

0.20%

V. low

Calcium baths Puddings and pie fillings Puddings, pie fillings flans, custards

CaSO,

136. 15

29.44

0.20%

0. 16%

V. low

59% 23%

In slightly acidic puddings, etc. , where slower release of Ca ions is desired and neutral gels

... ~

...

Table 10 (continued) . CALCIUM SALTS USED TO GEL ALGINATE FOOD SYSTEMS

"'1

Solubility In water Calcium salt

Formula

M,W,•

% Ca.

Cold

(II ~

Hot

Cost as or 4/80

Calcium citrate

Ca,(C 0H,O,)2·4H2O

570 .50

21.08

0.09%

0.09%+

Med.

Calcium tartrate

C,H,O6Ca·4H2O

260.22

15.4

0.03%

0.07%

High

Dicalcium phosphate dihydrate, secondary calcium phosphate, calcium phosphate dibasic, dicalcium orthophosphate Dicalcium phosphate anhydrous

CaHPO4 2H 2O

172.IO

23.29

0.02%

0.075%

Low

CaHPO4

136.10

29

Less soluble than the dihydrale

Ca,(P04 },

310.20

38.76

0.002-0.003%

Decomposes

Low

CaCO,

100.09

40.04

0.0015%

0.0019%

V. low

Tricalcium phosphate, tertiary calcium phosphate, calcium phosphate tribasic, calcium orthophosphate, tricalcium orthophosphate, precipitated calcium phosphate Calcium carbonate, precipitated

Low

g

~

Common uses In acidic systems releases calcium ions fairly rapidly Some puddings, especially, slightly acidic ones Canning, acid dessert gels, acid systems in general Same as the dihydrate but where slower release of Ca is desired Acidic dessert gels, fabricated fruit, acid system in general somewhat slower than Dical in releasing calcium ions for reaction Canning, acid systems where CO2 evolution is not a problem dessert gels

$

!} ~ ~ ::::: ~

~

Note: Approximate cost is listed only as a general guide. The cost ranges, as of 4/80, are: Very low (V. low)- less than 50c/lb Low - less than $1 /lb Medium (Med.) - $1 to 3/lb High - greater than $3/lb Solubility is expressed as the maximum concentration of salt obtainable in either hot or cold water at pH 7 .0. No figures on milk solubility are available at the present. It should be realized that rate of solubility, often more important than absolute solubility, cannot always be reflected in these figures.

•
I% of a highly purified alginate may be required). Gel strength increases with time, as ions diffuse into the gel and gelation proceeds toward equilibrium. The reaction is essentially impossible to stop once it has started, although the claim has been made that heat (160 to 2l2°F or 70 to lOO@C) is effective at stopping the algin/calcium interaction. 90 Methods used to control diffusion setting essentially consist of various contrivances designed to keep alginate and setting solutions (usually a soluble calcium salt) separate until seconds before the final food shape is formed. The production of onion rings from diced onions is one application example of the diffusion setting mechanism. Smadar patented an extrusion process which utilizes this algin system for manufacturing food products in any shape or size. 91 A matrix mix is prepared containing

160

Food Hydrocolloids

40% each of wheat flour and corn meal, 15% sugar, and 5% sodium alginate, (preferred ingredient levels). This matrix mix, comprising 10 to 15% weight of the slurry, is then blended with a comminuted food product (e.g., chopped onions), and extruded in ring form. As each ring is formed and cut at the extrusion nozzle, the outer surface is washed with CaC1 2 solution. The ring then drops to a conveyor belt and is carried under a batter solution and breading material. The ring is subsequently fried, frozen, and packaged. The instantaneous calcium/algin reaction provides necessary structural rigidity to the extruded onion rings so they can traverse several transfers from one moving belt to another without losing the ring shape. Under high speed production conditions this strength must develop within 4 sec. If insufficient gel strength is attained, rings will squeeze together at the transfer points, making them unacceptable for sale. Another type of apparatus which also may be used for producing onion rings and other extruded foods has been patented by Modern Maid Food Products. ® 93 This apparatus has the ability to continuously prepare a mixture of two components, which are fed through two separate conduits from individual containers into a common container where they are combined and extruded. The ability to keep two parts of the finished extrusion ••slurry" separate until just moments before extrusion should make possible the production of further refinements for extruded products that are not possible with single conduit extrusion equipment. Considerable work has been done to produce fabricated fruit products. One method involves surrounding fruit pulp or juice, which contains calcium or aluminum ions, with an alginate solution. This immediately forms an '"inside skin" around the fruit product due to the diffusion of calcium or aluminum ions. The resultant product is further strengthened by external treatment with these reactive ions, simulating the non-uniform structure of soft fruit such as black and red currants (i.e., with soft cores and tough skins). 94 A similar process for encapsulating drops of aqueous fruit material with an aqueous alginate was recently patented by Unilever. 95 An additional refinement of simulated fruit preparation was attained by extruding the alginate encapsulated aqueous fruit material into a calcium setting bath through which gas was bubbled. The bubbling gas created surface foam and served to minimize distortion of the drops, producing more spherically shaped pieces. 96 A novel use of diffusion setting has enabled pimiento puree to be used for production of pimiento .. strips", which are used in olive stuffing machines. Thus the laborious hand stuffing of olives is obviated and production can be greatly increased at lower cost. Several variations for this purpose have been described. 9 M 9 Another method designed to produce uniformly spherical shaped units utilizes a two-layer ••setting bath". By extruding the aqueous food material, containing a soluble alginate salt, into the top layer (a water immiscible liquid), very even spherical particles are formed. Consequently, upon contact with the calcium chloride solution (bottom layer), more perfectly spherical shapes were obtained. 100 Extruded meat and fish products have been claimed in both Australia 101 and Britain. 102 All of the proceding examples of diffusion setting involve extrusion applications. There are many other examples which can be classified under the category of coating applications. Probably one of the earliest commercial uses of this type was the coating of frozen fish to reduce '"freezer burn", or dehydration during freezer storage. Various other advantages were also realized, such as prevention of oxidative rancidity, easier separation of individual frozen fish pieces, and even reduction of freezing time. Glicksman has given a good review of this application. 103 Earle' 04 has obtained several patents using the coating technique. Fresh meat, seafood, or poultry is coated with an alginate solution (which also contains sugar). This coating, gelled with calcium chloride, protects the food material from bacterial contamination, dehydration, and handling damage. 104 He also claims a method for gentle removal of these coatings, which involves washing with polyphosphate solutions, so the meat product is not

161

damaged. 105 Several years later Earle and McKee 106 applied this coating technique to freshly slaughtered carcasses (beef, lamb, pork, e.g.,) for the purpose of controlling the growth of surface bacteria. The process involves spraying meat with an alginate solution followed by a CaC1 2 solution, which produces a continuous film around the meat part. Not only does this process achieve surface bacteria control, it also significantly lessens moisture loss from the meat and reduces surface oxidation. The process shows real promise as an alternative to the costly shrouding methods now used in the U.S. McKee 107 applies this same coating process to pizza crust, to retard or completely prevent soaking of pizza sauce into the crust, and to the finished pizza just before freeeing. Coating application to the finished pizza provides mechanical strength, prevents particulate matter from moving, retards oxidation of ingredients and helps to prevent freezer bum for frozen pizzas. Earle also utilizes this technique to coat raw onion rings with an algin film. 108 Since algin films are good fat barriers, this process produces improved fried onion rings by protecting the natural onion texture. A similar technique is used to coat sausages and other pre-shaped pieces of meat. 109 An individual casing is formed on each meat piece. Algin/calcium films have quite a long history as sausage casings but have several disadvantages over the more traditional cellulose and regenerated collagen products. Alginate films are susceptible to weakening from sodium salts and phosphates, which are commonly present in sausage meat, and they do not shrink with the meat upon cooking, so an unattractive wrinkled appearance results. 110 In another meat application, meat blocks composed of salted or boiled meat are held together with an alginate coating film, providing enough structural strength to withstand both handling and cooking. 111 Two Japanese patents describe the use of calcium alginate coatings to impart heat stability to foods originally gelled with other hydrocolloids - gelatin in one case 112 and carrageenan in the other. 113 Thermally reversible gels are first formed with either gelatin or carrageenan, then coated with a calcium alginate film, and finally subjected to pasteurization conditions. A similar way of using diffusion setting is encapsulation. The main difference here is the substrate size. Coating would normally refer to large and often irregular shaped objects while encapsulation would more typically refer to very small and usually spherical droplets. Encapsulation simply involves allowing drops of alginate solution (usually I to 2%), which contain the material to be encapsulated, to fall into a stirred calcium chloride bath (usually 5 to 10%), followed by removal of the gelled beads. These gelled beads may then be used in a column or bed. The algin/calcium reaction offers a useful tool to immobilize enzymes, or even live cells which can produce biologically active molecules. This application clearly illustrates the senipermiable nature of the alginate gel, holding the large protein molecules within the gel matrix and allowing smaller molecules to diffuse through the gel. Shorewood and Sandine• 14 claim a process for the enzymic removal of diacetyl from beer and ale which involves microencapsulation of enzymes (diacetyl reductase and reduced nicotinamide adenine dinucleotide), or combinations of enzymes and yeast, with calcium alginate. The enzymes or yeast cells are retained inside the alginate capsules and are easily separated from the treated beer or ale after they have performed their desired functions. 114 Glass and Glogowski 115 used encapsulation with an alginate gel to immobilize an enzyme system contained in subcellular particulates of vegetable material. The alginate matrix was found to be permeable to carbohydrate substrates. These immobilized enzymes were able to catalyze their respective reactions while maintaining activity for greatly extended periods, compared to non-encapsulated enzymes. In addition to lengthening the active lives of these enzymes, alginate encapsulation also eliminated •~end-product inhibition'" (inhibitory effects by high concentrations of end products from an enzyme reaction). Bananas were one of the materials used as an enzyme system source. Browning reactions, both enzymatic and nonenzymatic, are commonly observed with such materials. Very probably these reactions also produce enzyme inhibitors. When bananas were reduced to subcellular particulates and encapsulated with alginate, however, all of these inhibitory effects were strongly suppressed.

162

Food Hydrocolloids

Another exciting use of this technology has recently been developed by Lim and Sun. 116 They use the alginate gel to encapsulate viable, insulin producing cells (islets). Injection of these encapsulated cells into rats with streptozotocin-induced diabetes corrects the diabetic state for two to three weeks. Again this illustrates the semipermeable nature of the algin gel. Cells are retained but insulin produced by the islets diffuses out of the gel to react as required. At the same time, the cells are protected from large molecular weight antibodies which could cause rejection of the foreign tissue. This research shows promise as a future method of islet transplantation for the treatment of human diabetes. Kierstan and Bucke 117 quantified the permeability of an alginate gel which was used to encapsulate Saccharomyces cerevisiae cells or several individual enzymes. Their particular system provided little barrier to diffusion of neutral substrates up to a molecular weight of 5000. Only a single type of sodium alginate was utilized, however. Thermally reversible gelatin gels have been encapsulated with thermally stable alginate gels which contain the liquid centers that are produced upon heat processing. 118 An alternative to liquification of the centers by heating is the use of a proteolytic enzyme in the gelatin portion. Over a period of time the interior becomes liquid due to enzyme action. Encapsulation of certain microorganisms has been proposed as a means of monitoring the effectiveness of sterilization or pasteurization of foodstuffs. 119 The microbes are encapsulated, as described earlier, and added to liquids which are subjected to UHT sterilization. After UHT treatment the microbe-containing capsules are easily removed and can be checked for viability (i.e., ability of the microbes to grow). In canning applications the capsules are located in the center of the can by means of a special holder. Spores or cells can be recovered by dissolving the alginate capsules in an aqueous citrate solution. d. Internal Setting The '" internal setting" method of forming gels relies upon calcium release under controlled conditions from within the system. Compared to gels formed by the diffusion of calcium ions into an alginate solution, which produces the highest gel strength at the calcium/alginate solution interface, internally set gels produce a uniform gel texture, gelling the entire mass. Since both algin and calcium salts must be thoroughly mixed before reaction occurs, calcium salts which are initially insoluble or only slowly soluble are utilized. Once the algin and calcium salt have been intimately mixed, calcium ion release is achieved in one or more of the following ways: by allowing time for a slowly soluble calcium salt to hydrate; by lowering the pH (e.g., with a slowly soluble acid); or by temperature changes. Usually sequestrants are also needed to control the reaction. This gelation method is particularly well suited for applications which require gels of specific shapes (i.e., molded gels such as aspics and dental impression gels) and for products that are prepared from dry mixes (which contain all ingredients required to develop the gel system). Dry mixes are very convenient for consumer use since they are simply added to water or milk and mixed to produce the desired item. Dry mixes have been prepared to make such products as bakery jellies and fillings, dessert gels, aspics, facial masques, dental, and other impression materials, puddings, pie fillings, flans, and various aerated desserts. Dry mix internal setting systems are considerably more complex than those obtained by diffusion setting. Since the gel system components interact with one another once they are dissolved, the sequence of hydration is critical. For example, the alginate must be hydrated before the pH drops much below 5.0. Consequently the solubility rate of each gel system ingredient is critical. Probably the best way to illustrate this fact is to examine some formulations and analyze how the ingredients function. These applications may be divided into those which depend on the solubility rate of a calcium salt and those which depend on the solubility rate of an acid (so called, acid triggered systems). The following formula for a Chocolate Chiffon (or Mousse) is a good example of an algin gel prepared by correct use of the solubility properties of calcium gluconate.

163

CHOCOLATE CHIFFON (WHOLE-MILK TYPE) 120 Ingredients Sugar, fine granular Spray dried fat Cocoa powder Phosphated sodium alginate (DARILOID® QH - Kelco Division of Merck & Co., Inc.) Calcium gluconate, USP powder Tetrasodium pyrophosphate, pudding grade Salt Vanilla flavor

Percent 60.17 27.13 8.14 2.17 1.63 0.38

0.27 0.11

ioo.oo

me

Mixing instructions - add dry ingredients (184.3 g) to 236 (1 cup) cold milk in a small mixing bowl. Blend at lowest speed, then beat at high speed 4 min. Yields filling for one 8 in. pie shell. The critical ingredients in this dry mix are sequestrant (TSPP), alginate, and calcium gluconate. Upon addition of this dry mix to milk, the TSPP hydrates first and ties up free calcium in the milk, permitting the alginate to hydrate in a nearly calcium-free environment. Once the milk calcium has been tied up by sequestrant, however, it is no longer available to react with the dissolved alginate and no gel can form unless more calcium is available. Calcium gluconate provides this calcium by slowly dissolving to release sufficient calcium ions to react with the alginate. Patterson 121 patented a heat stable and freeze-thaw stable dry mix whipped topping which utilizes a '"milk soluble" sodium alginate plus calcium gluconate. Probably the most unusual application of this system was to make an impression of a sleeping bull elephant. This was accomplished by painting an alginate paste, prepared from a dry mix very similar to the facial masque formulation listed below, onto an anesthetized elephant.

FACIAL MASQUE 122 Ingredients

Amount

Potassium or sodium alginate (KELTONE® = Kelco Division of Merck & Co., Inc.) Magnesium carbonate or diatomaceous earth, powdered Calcium sulfate, dihydrate Tetrasodium pyrophosphate, anhydrous, powdered

2.5

(g)

10.0 2.5 0.9 15.9

Procedure - thoroughly blend all dry ingredients with mortar and pestle. To 60 mt' of room temperature water in a rubber mixing bowl, add 15.9 g of the above dry material and mix rapidly with a spatula for 1 min. Apply the ••plastic''' material immediately and allow it to set to an elastic masque (about 4 min). Similar formulations are used as dental impression materials and to make impressions for various types of art work. Earlier we referred to a gelled toy product89 which is another application example of this same internal setting mechanism. All of these formulations function in the same way. TSPP dissolves first, sequestering free calcium and initial calcium

164

Food Hydrocolloids

released by the added calcium salt, allowing time for the alginate to hydrate. After sufficient alginate hydration has been achieved, additional calcium from calcium sulfate dihydrate sets the gel. Earlier, solubility rate of the gel system components was cited as a critical consideration. In some instances ingredients not involved in the gelling reaction may affect the solubility rate of the gel system components and thereby force formula changes. A good example of this effect is shown by the following formula.

GOURMET DESSERT (LIQUEUR MOUSSE) 123 Ingredients

Amount (g)

Dextrose Spray dried fat Calcium gluconate "Low residual calcium" sodium alginate, fine mesh (KELTONE® = Kelco Division of Merck & Co., Inc.) Tetrasodium pyrophosphate, anhydrous Xanthan gum, fine mesh (KELTROL® F; Kelco Division of Merck & Co., Inc.) Total dry ingredients Half & half cream (or milk) Liqueur (non-acidic flavors, 60 proof)

18.47 5.00 0.57 0.50

0.26 0.20 25.00 60me 60 me

Procedure - using a kitchen-type mixer (with egg beater blades), add the dry mix to liqueur and milk product while mixing at lowest speed. After thoroughly wetting the mix, gradually increase mixing speed to ••high" and mix until the product thickens and air is incorporated (approximately 5 min). Chill 15 to 30 min before serving.

As with the chocolate chiffon mentioned earlier, TSPP sequesters free calcium to allow the alginate to hydrate. However, alcohol not only adversely affects the hydration of algin, but also affects the hydration of some calcium salts. In many dry mix applications either calcium sulfate dihydrate or calcium gluconate may be used as the calcium source. In the alcoholic environment, however, the hydration of calcium sulfate is apparently strongly inhibited, while calcium gluconate does provide calcium ions to set the gel. Acid triggered gels produced from dry mixes are somewhat more complex than those depending only on calcium salt solubility. There are four essential ingredients for this gel system: a sequestrant which is able to bind calcium ions under acidic conditions, a ,slow residual calcium" alginate, an ••insoluble" (under neutral conditions) calcium source, and a slowly soluble acidulant. The sequestrant (often sodium hexametaphosphate) binds any available calcium to allow the alginate to hydrate. As the slowly soluble acid dissolves (adipic or fumaric are commonly used), it gradually supplies hydrogen ions which subsequently release calcium ions from the ••insoluble" calcium salt (often dicalcium phosphate dihydrate, or CaCO3). Here the acidulant is the key ingredient. Rapid solubility of an acidulant would release calcium too quickly and cause a lowering of pH, both conditions being detrimental to alginate hydration. The following examples illustrate acid triggered gels.

165

INSTANT IMITATION BAKERY JELLY 120, 124 Ingredients

Percent

Sugar, refined, fine granular Instant starch Adipic acid, fine granular "Low residual calcium" sodium alginate, fine mesh (KELTONE®- Kelco, Division of Merck & Co., Inc.) Sodium hexametaphosphate, unadjusted powder Guar gum, 200 mesh Dicalcium phosphate dihydrate Aavor Potassium sorbate Sodium benzoate Color

58.80 14.89 8. 13 6.30 3.52 2.96 2.22 1.41 0.67 0.67 0.42

ioo.oo

Procedure - mix dry ingredients (28.4 g) with 113.5 g (114 lb) sugar. Add dry mix to 236 mf (I cup) tap water and mix vigorously with a wire whip for one minute. Jelly will be ready for use in 30 to 50 min. This particular formulation produces a fast-setting, firm gel with good heat stability. Guar and '"instant starch" provide a plastic consistency upon mechanical breakage of the gel (via pumping, mixing, etc.) The four gel system components are sodium hexametaphosphate (sequestrant), sodium alginate, dicalcium phosphate dihydrate ('"insoluble" calcium salt), and adipic acid (slowly soluble acid). Adipic acid is usually the acid of choice for these dry mix, acid-triggered gels because of its slow solubility rate, its buffering action, and the fact that it is not hydroscopic. 125 For concentrations from 0.5-2.4 g/100 mf, in an aqueous solution, the pH varies less than half a unit. 126 Consequently, good acid flavors can be achieved at considerably higher pH values (3.8 to 4.5, e.g.) than with other acidulants, which is ideal for the algin gel system. The resultant higher pH helps the alginate hydrate and confers greater stability to the final gel because less alginic acid is formed than at lower pH values. For many years an area of particular interest has been that of algin cold water dessert gels. Gelatin dessert gels require heating to solubilize the gelatin and refrigeration to set the gel. Algin dessert gels, being '"chemically" set in the cold by calcium ions, require neither heat nor refrigeration. The two main problems limiting this application are texture and tolerance to variations in water hardness. Alginate-calcium gels, being thermally stable, do not ..melt in the mouth,. like gelatin gels. Consequently, to design an acid-triggered, cold water dessert gel (like the example below), one must very carefully balance the gel system ingredients and produce a somewhat more delicate gel (lower gel strength) so it can more easily be broken down in the mouth. Changes in water hardness can result in weak gels, when ••soft" water is used, or grainy gels, when very '"hard" water is used. These ••weak'~ or ••grainy" gels may be obtained at water hardness levels ± 50 to 100 ppm of the optimum conditions. Optimum conditions are defined as the water hardness levels which will produce acceptable products for a given dessert gel formulation.

COLD WATER DESSERT GEL 120 Ingredients Sugar, refined, fine granular "Low residual calcium" sodium alginate (fine mesh) (KELTONE® - Kelco Division of Merck & Co. Inc.)

Percent 89.95 3.42

166

Food Hydrocolloids Adipic acid, food-grade powder (Monsanto) Sodium citrate, U.S.P. powder (Pfizer) Dicalcium phosphate, anhydrous powder (Stauffer Chemical) Flavor Color

3.23 2.82 0.35 .20 .03

ioo.oo%

me

Mixing Instructions - add dry ingredients (85 g) to 472 (2 cups) of cold water (or boiling water) and stir briskly for one minute. Pour into molds or dessert dishes. Gel will set at room temperature or in a refrigerator within 20 to 30 min. In this formulation sodium citrate has been used because it elevates the pH, providing a little more time for the alginate to hydrate and helping to improve the system's tolerance to variations in water hardness. Anhydrous dicalcium phosphate (DCP) is less soluble than dicalcium phosphate ·dihydrate (DCPD) (see Table l 0) and also helps to improve the tolerance to hard water. Miller and Rocks 127 claim a dessert gel composition containing water soluble alginates, CaCO 3 , sodium tripolyphosphate, and sufficient edible acid to liberate calcium ions to form a water-insoluble calcium alginate gel. The internal setting mechanism is also used for applications other than dry mixes. Usually these products are produced by hydrating the alginate and then adding the calcium salt immediately prior to deposition, extrusion, molding, etc. Products such as food for feeding fish and crustacea, high soluble solids items, and fabricated meat, fish or vegetable products are examples. Once the slowly soluble calcium salt or acid is added to an alginate mix, there is a finite time limit, or ••open time", prior to gelation. By using sequestrants this "open time can be extended to 30 min quite easily. It is very difficult to achieve '''open times" of an hour or more, however, for after a certain point the addition of more sequestrant to lengthen the '"open time" becomes counter productive, taking up calcium needed to set the gel. The following formula for binding various kinds of seafood scraps illustrates the use of this method. 128 Ingredients

Percent

Seafood scraps (cooked) Water Tetrasodium pyrophosphate Sodium alginate (KELCO-GEL® HV - Kelco, Division of Merck & Co., Inc.) Vegetable oil Calcium sulfate dihydrate Vegetable oil

75.35 18.83 0.09 0.75 2.35 0.75

~ 100.00

Procedure - add water and phosphate to seafood and mix (in a Hobart-type mixer equipped with a paddle blade, for example). Slurry the alginate in about 3 parts vegetableoil and mix this slurry into the seafood. Continue mixing for 5 to 10 min. to hydrate the algin. Then slurry the calcium sulfate in vegetable oil and mix this slurry into the seafood blend, mixing only until uniform (2 to 3 min). Place the mix into molds to set. After an hour or more, these gels may be sliced, battered, and fried to produce tasty, hot seafood snacks. Any drainage which results from cooking the seafood may be used as part of the formulation water if more flavor is needed.

167

Heinen used this internal setting mechanism as an effective binding agent for crustacea diets. 129 He obtained the best results by mixing a trout feed, which contained fish meal and fish solubles (the source of calcium), with a solution of sodium alginate and sequestrant. Using 1% alginate and as little as 0.5% sodium hexametaphosphate, he was able to obtain more than 24 hour of water-stability with the algin bound pellets. Chimirov et al., 130 claimed an improvement in pasta was obtained by the inclusion of sodium alginate (0.3 to 2.5%), calcium gluconate or lactate (0.2 to 1.2%), potash (0.2 to 0.8%), and flour. In this case the K 2CO 3 (potash) probably acts as a sequestrant, due to its elevation of the pH and competition for calcium ions, thus providing "open time" so the pasta may be extruded before the onset of alginate gelation. Hawley 131 used the internal setting method to produce a novel product described as '"artificial adipose tissue". A gel was made by adding a calcium salt to an emulsion of water, sodium alginate, sequestrant, and fat. The fat, trapped as discrete droplets within the gel matrix, was released during cooking as it caused rupture points in the matrix walls, effecting slow basting of a simulated meat product, probably similar to bacon. Shalunova et. al., ' 32 used comminuted meat or fish, sodium alginate, calcium gluconate, dried milk, salt, and spices to produce various sausage products. After filling into cellulose casings, the mix set to a gel. With fish protein paste as the raw material, the sausage mass was kept for a period of time in a I% citric acid bath (after being filled into the casing). This treatment produced a '"resilient and compact consistency.,. 132 The internal setting mechanism has been used to produce certain medical aids. Wise' 33 developed a process for making water-absorbent and water-disintegrative algin sponges, suitable for use as medical receptors for biological fluids. Examples of such medical receptors include lacteal, fecal, catamenial, diaper, obstetric and surgical, sudatory and urethrorrheal receptors. They also may be used in the treatment of bums and as dental or oral sponges. The sponges are preferably produced by dispersing I to 2% by weight of a calcium-sodium alginate composition in water followed by freeze drying the aqueous dispersion or gel. The sodium alginate composition consists of from 50 to 20% of finely ground calcium alginate and 50 to 80% of a finely ground sodium alginate. The resultant freeze dried alginate sponge can absorb up to 50 times its own weight of liquid while retaining structural integrity. Hydration beyond its maximum absorbtive capacity results in disintegration or dissolution of the algin sponge structure, which facilitates disposal. 133 Gelled products having a heterogenous structure (e.g., simulated orange pieces) are described in a patent application submitted by Unilever. 134 An alginate gel is produced with particles of a second gel within it. Agar-agar gel particles (0.5 to 2% by weight), with a higher sugar concentration than the algin solution, are dispersed in the alginate solution (e.g., 1.5 to 5% by weight of sodium alginate). Calcium ions are included in the agar-agar gel, and diffuse into the alginate solution initiating gelation. Alternatively, a calcium salt is mixed into the algin solution after dispersion of the agar-agar gel particles. Fruit flavorings or fruit pulp are added to the alginate solution as well as an agent which stabilizes the solution against freezing and thawing. Unilever Ltd. has patented a fruit-like food product which is obtained by combining an alginate solution (containing sequestrant and an "insoluble'~ calcium salt) with various fruit purees (which may also contain acidulants and additional materials to impart freeze-thaw stability) in a high-shear, low residence time in-line mixer such as an Oakes 4M. The time between mixing of the alginate solution with the fruit puree mix and the emergence of the mixture from the distributor is less than 30 sec, and practically no gelation of the mixture occurs. This is one example where an alginate with a high guluronic acid content was shown to be necessary (i.e., the ratio of mannuronic acid residues to guluronic acid residues was less than 1:1). 135 These products are designed to simulate natural fruit and be incorporated in such items as fruit pies or flans and yogurt, and can be formulated to withstand canning

168

Food Hydrocolloids

and baking, or freezing and thawing. A related patent 136 discloses a preferred process for preparing simulated fruit products. e. Temperature Influenced: Internally Set Gels Until now systems which are mainly prepared at ambient temperature have been discussed. Quite often temperature can be effectively used to control the calcium/algin gelation reaction. As mentioned earlier, elevated temperatures [usually 160°F (71 °C), or higher] can prevent the calcium/algin reaction. Under these conditions, thermal energy imparted to the algin molecules does not allow them to align and gel in the presence of small amounts of calcium ions. Good hydration is obtained at these elevated temperatures, and a gel forms on cooling. Heat may also be used to '"trigger" an acid (see Table 11) which in turn releases calcium by lowering the pH. Finally, by carefully balancing alginate and available calcium levels, a system can be formulated to flow at room temperature and set to an irreversible gel upon further cooling or freezing. The following formulation illustrates how heat can be used to sequester available calcium ions, allowing the alginate to completely hydrate and produce upon cooling, a clean-cutting gel with texture very much like that of egg custard. The ingredients must be added to boiling milk and not cold milk or cold milk which is subsequently heated to a boil. VANILLA FLAN 137 Ingredients

Percent

Sugar, fine granular Phosphated sodium alginate (DARILOID® QH - Kelco Division of Merck & Co., Inc.) Salt, fine granular Vanilla flavor Colors

93.568 5. 131

me

0.641 0.641 0.019 ioo]oo

Procedure - bring 472 (2 cups) of milk to a boil in a one qt saucepan. Remove from heat and add dry ingredients (77.965 g or 2 3/4 oz). Stir well for one min and pour into serving dishes.

In this product, all of the calcium required to set the gel comes from milk and is temporarily inactivated via boiling. A low level of sequestrant is utilized to control the gelling reaction and normally is included as a part of the alginate product. Muynck et. al., 138 claim a method for preparing sterilized custards, one with an amylosecontaining starch, and one with only algin as the setting agent. 139 Sodium alginate and calcium gluconate are added to a hot mixture of milk, sugar, colorings, and flavorings. This mixture is then sterilized by heating to 130 to 155°C for 3 min, cooled and aseptically packaged. This process produces products with good storage qualities. An interesting example of using sub-ambient temperatures to set an algin gel is given in a Unilever patent application. 140 A protective coating for frozen desserts (e.g., ice cream, sorbet, frozen custard, or frozen mousse), which acts as a carrier for water-soluble flavorings and colorings, is claimed. The coating is produced by dipping the frozen dessert into an aqueous thixotropic gel produced from 0.2 to 0.8% (by weight) alginate and 4.5 to 2.5 mg calcium ions/g of alginate. 3. Insoluble Polymers Production of insoluble polymers is the third major way to utilize the calcium/algin interaction. The starting point for these polymers is an alginate sol (or '"solution'~), rather than a dry powder. Alginate molecules are in the fully hydrated state before formation of insoluble polymers. Insoluble polymers result from extensive interaction with calcium ions, beyond that required to achieve increased viscosity or gelation.

169

ALGIN/CALCIUM REACTION H

coo-

H

-o

---0

0

COO-

H

Segment of Linear Chain

~

Low/~h ea,

Alginate Solution

FIGURE 22. formation.

Schematic representation of algin/calcium gel formation and algin/calcium insoluble polymer

Figure 18 graphically depicts the relationship between calcium ion concentration and alginate viscosity. Between points A and B, at relatively low calcium ion levels. viscosity increases are observed. At point B gelation starts to occur, and at point C the calcium ion concentration is high enough to produce insoluble, calcium alginate precipitates. Figure 22 schematically illustrates that the insoluble calcium alginate ( ••fibrous precipitate'~) is more extensively interacted with calcium ions than the gel. Since there is an immediate, radical viscosity increase when alginate and soluble calcium salt solutions (e.g .. CaCU are mixed. efficient high shear mixing is required to rapidly traverse the gel stage (see Figure 18. Point B) and obtain an insoluble precipitate (see Figure 18. Point C). 141 Because the alginate has been precipitated as an insoluble polymer. it is no longer primarily effective as a thickening agent but rather imparts texture, or ••pulp". to a food system. For this reason these insoluble alginate polymers have been referred to as Algin-Tex. 141 They can simulate fruit or vegetable solids in a food product. These materials may be formed by two basic procedures: ( 1) by adding an alginate solution to a well-mixed calcium solution (CaC1 2 , e.g.) or; (2) by adding a measured amount of CaCl 2 (just enough to completely precipitate the alginate) to a well-mixed solution of alginate. The second method is much more versatile and the one of choice whenever it is desirable to entrap other components within the insoluble polymer matrix. Whatever is added to the alginate solution. prior to precipitation with CaCl 2 • will subsequently become entrapped in the matrix (fats, proteins, carbohydrates, colors. fruit, and vegetable solids, e.g.). Entrapment of various substances in the algin-Tex will modify its

170

Food Hydrocolloids

texture and can change or modify the characteristics of the entrapped substance. For example, the addition of high molecular weight materials (starches, gums, etc.) to an alginate solution prior to precipitation will produce a softer texture than would otherwise result without their presence, and the entrapmemt of citrus flavor oils inside very small Algin-Tex particles shows promise as a physical method to add weight to the oil droplets and prevent floating (i.e. ringing). Size and to some extent shape, of these particles is a function of the type of mixing during the precipitation stage. As a general rule, the higher the shear applied during precipitation (i.e., addition of CaC1 2) the smaller the resulting particle size, and vice versa. There are several factors which affect the formation of these polymers and consequently influence final particle texture and size. Among these factors are mixing conditions (i.e., depending on the type of equipment), ingredients, pH, temperature, and rate of algin/calcium ion mixing. Mixing conditions must be thorough, and efficient enough to break up any gel formation and pernit maximum contact between algin molecules and calcium ions. In the laboratory a Hobart mixer equipped with a wire whip works quite well. The most important factor to consider with various types of mixers is the efficiency of mixing as viscosity increases and the volume varies with different batch sizes. If the efficiency of mixing varies, so will the insoluble polymer characteristics. As mixing efficiency decreases, gel formation becomes more predominant and less and less of the extensively calcium reacted alginate is obtained. This material should be produced at room temperature. Heat above l00°F (37 .59 C), results in decreased reactivity and inferior products. The pH of a system, just prior to reaction with calcium ions, should always be 4.3 or higher. Below this pH, a significant proportion of the carboxylate anions are converted to the free acid form and to achieve optimum results the carboxyl groups should be in the anion form. When reaction of the alginate with calcium is complete, however, the pH may be adjusted to any desired value. In general, slow addition of calcium ions, under given shear conditions, favors small, fine pieces, while rapid addition favors larger insoluble polymer pieces. Ingredients are also of great importance in determining the final texture of these precipitated alginate products. Many types of alginates may be used, but low viscosity alginates are preferred for ease of mixing. High viscosity algins and PGAs (of 50% esterification or less) may be useful to achieve specific properties, such as tougher, more stringy texture, with the former, or small, delicate particles, with the latter. The concentration of alginates utilized will normally be less than 1% in a finished food product. Superior insoluble polymer formation will result if small amounts (approximately 0.1 %) of a sequestrant are used to sequester calcium ions from water and the alginate. Calcium ions may come from various sources, but CaCl2 is preferred. The characteristics of these products are what make them useful as texturizing tools. The degree of stability may depend on the actual formulation, but in general, once these insoluble polymers are formed and allowed to cure for a few minutes, they are highly: 1. 2. 3. 4.

Heat stable - and will withstand deep fat frying, oven baking or retorting, without losing their structural integrity. pH stable - over the entire pH range encountered in foods. Shear stable- additional mixing or processing does not significantly alter the structural integrity of these polymers. Stable in many other environments - freeze-thaw stable, salt stable, and alcohol stable. Since stability results from extensive interaction of the alginate molecules with calcium

171

ions (achieved primarily during the precipitation step), the greater the extent of this interaction, the more stable the insoluble polymers will be, and vice versa. Some of the benefits which can potentially be provided to food systems by these insoluble alginate polymers are 1. 2.

3. 4.

To provide a ••pulpy"" texture to a food system - other solids may be included inside the alginate matrix or a completely imitation product may be produced To preserve a '"pulpy" texture in a food product- for example, the texture of delicate fruits such as bananas, strawberries and raspberries, may be '°fortified" by mixing the pureed fruit with an alginate solution and treating the mixture with calcium chloride solution To entrap materials such as oils and fats - this is especially useful for the production of meat-like texture To produce pulping and clouding agents (propylene glycol alginates are particularly useful here). and as color and flavor carriers for various beverages or flavor concentrates and emulsions

The following formulations will illustrate two specific applications of the insoluble alginate polymers.

SIMULATED FRUIT (ORANGE) PUREE 142 Ingredients Water Sugar CaCl 2 (5% solution) Instant starch Sodium alginate (KELGIN® LV Kelco, Division of Merck & Co., Inc.) Sodium hexametaphosphate Sodium citrate Yellow color Orange oil (single fold) Sodium benzoate Potassium sorbate

Grams

607.94 255.8 39.6 24.4 9.14 0.19 0.31 to suit 60.90 0.50 0.50

i1ioo.oo

Procedure - blend all dry ingredients. Add dry blended ingredients slowly to Hobart mixer, equipped with a wire whip (Speed #1), and containing the formula water; mix for approximately 30 sec until the dry ingredients become thoroughly wet. Increase speed to #3, mix for 5 to 7 min. (Scrape down sides of the bowl after 2 min mixing.) Add orange oil very slowly, to form a fine emulsion, while mixing at high speed (#3). Check pH, (should be above pH 4.3), adjust if necessary (add more sodium citrate). Add CaC1 2 solution (5%) relatively fast, while mixing at medium (#2) or high speed (#3), depending on the size of pulp desired. (Medium speed will produce larger and longer pulp than high speed,) Only 15 to 25 sec of mixing, after CaCl 2 addition is complete, is necessary. Approximately 5 min after precipitation, adjust pH to the desired level with citric acid solution (50%).

In this formula the instant starch helps to produce an orange-like texture by preventing the Algin-Tex from becoming too tough, as well as helping to prevent syneresis and provide long term stability and opacity. Sodium citrate is needed to buffer the pH above 4.3 and sodium hexametaphosphate is used to bind any free calcium ions in the system before addition of CaCl 2 . Benzoate and sorbate are added for preservation purposes. The final simulated fruit puree is suitable for use in fruit flavored fillings or in fruit flavored drinks when the particle size of the Algin-Tex material is small.

172

Food Hydrocolloids

SIMULATED CRABMEAT PRODUCT 143 Ingredients

Grams

Water Calcium chloride, 5% solution Vegetable oil, soybean Maltodextrin Instant modified starch Sodium alginate (KELGIN® LV Kelco, Division of Merck & Co., Inc.) Soy protein isolate Taste of crab, natural flavor comp., Sodium hexametaphosphate

726.6 88.0 73.0

37.0 29.0 22.0

15.0 6.8 2.6 1000.0

Procedure - mix sodium hexametaphosphate in water (LIGHTNIN'® mixer, paddle blade, set on medium speed). Thoroughly blend remaining dry ingredients. Slowly add dry ingredients to well-agitated water using LIGHTNIN'® mixer. Mix for IO to 15 min on medium speed. Place mixture into table-top Hobart mixer with whip attachment. Slowly add vegetable oil to mixture agitated at medium speed until a homogeneous mixture is obtained. Add all of the calcium chloride solution at once under medium speed agitation. Immediately after texture is formed, stop mixer and scrape bowl sides and whip with spatula to break up larger chunks. Turn on mixer at low speed for a few seconds, long enough to break apart large chunks of simulated crabmeat.

A method of preparing a clouding agent for juice drinks is claimed by Niwano. 144 The procedure used is similar to that used to produce Algin-Tex. A suspension of alginate, crystalline cellulose, and water is vigorously mixed with calcium chloride, and/or alum, to produce short, insoluble calcium alginate fibers with the cellulose trapped inside. The resulting fibers are stable to pasteurization. In a specific example, fibers produced from I0 parts of crystalline cellulose, 250 parts of 1% sodium alginate solution and 250 parts of a 2% CaC1 2 solution produce a cloud which exhibits good stability for 48 hr. The clouding agent can also be dehydrated and then freely dispersed in fruit juice. Alginate fibers can be produced by procedures similiar to those used to obtain other fibers or filaments. An alginate solution is spun into a CaC1 2 bath and pulled out as calcium alginate fibers or filaments. These fibers have been used in the past to make absorbent swabs 145 and surgical gauze. 146 · 147 They are classified as '"fugitive" because of their ability to dissolve in saline or alkaline solutions. The earliest description of spinning fibers from sodium alginate was in 1912. 148 Most recent work utilizing alginates to produce calcium alginate fibers has involved the inclusion of proteins. Spun protein fibers can be modified with algin, or the alginate fiber may act as the main binder system to produce fibers from protein sources which cannot form fibers by normal procedures (e.g. denatured proteins, flours, protein byproducts or wastes, etc.). By incorporating denatured, inactive, or non-functional protein materials into an alginate solution before spinning it into a CaC1 2 solution, protein fibers can be formed. A patent assigned to General Foods® 149 describes the successful use of this technique and further modifications are described in patents issued to Atkinson. 150 - 151 A typical protein fiber spinning process involves the following: 1.

Dissolving protein isolate (90% protein, obtained from defatted oilseed meal) in NaOH solution (pH 10.5-12.5) to give a solids concentration of 10 to 30%. This solution is called '"dope,. .

173 2. 3. 4. 5.

The dope solution is aged for a few minutes (until viscosity increases from 25 to 300 P), then forced through a spinnerette (3 in. diameter, 1000 to 1600 orifices of 0.002 to 0.006 in. diameter) into an acid/salt bath. Coagulated fibers are stretched 50 to 400% on pickup reels and collected in bundles (114 in. diameter) which are then assembled in tows (3 to 4 in. thick). Fiber tows are squeezed between rollers to remove excess moisture and then passed through a neutralizing bath. Fiber tows are then processed further depending on end use, or cut and stored for subsequent treatment. 148

For several years researchers at the University of Laval, Quebec City, Quebec, Canada have been investigating the use of alginates to modify spun protein properties. 152 According to their studies, some of the advantages alginates provide are I. 2. 3.

Spinning can be done at near neutral pH, instead of pH 12. Very alkaline conditions tend to degrade proteins but proteins alone do not spin well below pH 12. pH 9 seems to be optimum with alginates. Nearly any protein can be used with algin to obtain fibers, by spinning into a CaCl 2 and acid bath. Compared to protein fibers without algin, fibers formed with algin have longer dry storage shelf-life, but do not rehydrate or bind water as well. 153 • 154 Subsequent work showed that by including pregelatinized starch in the dope the rate of fiber dehydration was increased and the rehydration maximum could be controlled. 155

Rusig 156 evaluated the use of plasma protein and plasma protein-alginate fibers for replacing up to 40% of the meat in sausages. The texture of products produced with plasma proteinalginate fibers (extruded) was preferred both before and after frying when compared to products not containing the alginate fibers. Imeson et al. 157 studied the rheological properties of spinning dopes and spun fibers produced from plasma-alginate mixtures. Fibers produced from a mixture of 2% sodium alginate and 6% blood plasma, spun into a CaCl 2 bath (at pH 4.0), were evaluated for tensile and shear strength. These properties were found to vary depending on the guluronic acid block content and molecular weight (viscosity) of the alginates. Casein fibers have also been produced with the aid of alginates. Downey and Burgess prepared casein/alginate fibers at neutral pH and were able to alter the textural parameters by various changes in the conditions of spinning. 158 To avoid the difficult and expensive spinning procedure, Arima and Harada 159 produced simulated spun fibers by using the algin-calcium reaction to produce fibers by high shear mixing. A large excess of CaCl 2 was also used (55.5 kg of CaCl/3 kg of sodium alginate), probably to effect protein coagulation as well as alginate precipitation. This technique, followed by an acid treatment and extensive washing, produced (from protein starting material of a non-fibrous nature) relatively hard and chewy protein fibers, having a meat-like resistance to biting. B. Other Alginate Salt Applications Applications which utilize alginate properties other than the interaction with calcium can be categorized under the following headings: viscosity building (suspension, etc.), film forming, interactions with other molecules, and general colloidal properties.

I. Viscosity Building Usually alginates are not used in food, cosmetic or pharmaceutical systems for the sole purpose of providing viscosity, which can often be attained with lower cost materials. However, examples of where the viscosity properties of algin are those of choice include:

174 I. 2. 3. 4.

Food Hydrocolloids

Syrups - low calorie, dry mix-types, and marshmallow variegated syrup (used in the production of certain types of ice cream) Cake mixes - to provide proper batter viscosity Lubricating jellies for medical use Piping jellies for decorating cakes, etc.

The following formula illustrates the use of sodium alginate to produce a clear piping jelly using considerably less rigorous processing than with agar-stabilized formulations.

PIPING JELLY WITH SODIUM ALGINATE 160 Ingredients

Water Sugar, fine granular Com syrup, 62 D.E. Sodium alginate (KELGIN® MY Kelco , DivisionofMerck&Co., Inc.) Citric acid , anhydrous Sodium benzoate Sodium citrate, hydrous Color

Percent

38 .065 33 .000 27.000 1.500 0.280 0.100 0.050 0.005

ioo]'oo

Procedure - blend the alginate with five parts of sugar and solubilize in well-agitated water. Add remaining ingredients, except for acid and color, and heat to about l 60°F (71 °C) to dissolve all sugars. Add color and citric acid, package and cool.

2. Film Forming Alginates possess good film forming properties which make them particularly useful in certain paper manufacturing applications. Films produced by evaporation of water from a thin layer of alginate solution are impervious to oils and greases but will transmit water vapor and redissolve when exposed to aqueous systems . Alginate films tend to be quite brittle when dry but may be •~plasticized " somewhat by the inclusion of glycerol. Generally speaking, a low molecular weight, ••1ow residual calcium" alginate is desirable to form the best films. These films have excellent ••non-stick'~ properties and consequently are often used as mold release agents. 161 A dental parting or separating compound is an example of such an application. These .. compounds" are simply alginate solutions. Usually a '"low residual calcium'" alginate of low viscosity is used, and a solution of 400 to 500 cP is prepared. The alginate solution is painted onto the plaster (gypsum) mold, and interacts with calcium ions from the gypsum, producing an insoluble film . This alginate film serves as an effective separator for both denture and crown and bridge molds because it bonds to the gypsum mold but not to the denture base resin , which is subsequently processed in the gypsum mold. Consequently, after the resin is cured, it may be separated from the gypsum mold without damage. Attempts to produce water soluble alginate films which can be used as packaging materials for detergents, enzymes, or various food components, have generally not been successful because of the brittle nature of such films. A British patent describes the use of algin's film-forming properties to coat the surface of compressed concentrate particles, such as freeze dried coffee concentrate. 162 The resulting thin skin, formed by spraying compressed concentrate particles with a 5% sodium alginate solution containing as much as 30% alcohol , serves as a barrier layer and helps to maintain particle integrity while still allowing dissolution upon the addition of hot water.

175

3. Interactions with Other Molecules Interactions between proteins and hydrocolloids are well known. For example food technologists are familiar with the interaction of milk proteins and carrageenan 163 as well as that of carboxymethyl cellulose (CMC) with whey or soy proteins. 164 Electrostatic attraction between charged polysaccharide and protein molecules is generally thought to be the major driving force for these interactions. 165 · 166 Imeson et al. 167 studied the interactions between alginate and the proteins myoglobin and bovine serum albumin. Both native and heat denatured forms of these proteins were evaluated at pH 6.0. The denatured forms were found to be more strongly reactive, giving rise to stable high molecular weight complexes which inhibited protein-protein aggregation and hence precipitation. Results of this research also suggested that the interactions are primarily electrostatic in nature and increase as the net positive charge on the protein increases. Use of this interaction was suggested as a potential method for protein recovery from dilute solution, by adjustment of pH and/or ionic strength. At low pH (4.0) the protein/alginate complex precipitates and can then be redissolved by neutralization (pH 7.0). Although other interactions are also involved, alginate/protein interactions seem to play a role in clarification of wine, 168 which has been extensively investigated in Russia. After treatment with sodium alginate, there was a decrease in the total nitrogen observed in the wine. A method for producing non-denatured protein concentrates utilizes this algin/protein interaction. Lowering the pH of an aqueous alginate/protein solution, at temperatures below 50@C (148°F), produces the precipitated concentrate which is subsequently freeze-dried. 169 An earlier U.S. patent claims a method for making soy protein concentrates with alginate (or other hydrocolloids), using the same technique. At pH 4.2 to 4.6 the resultant insoluble protein fraction is recovered. 170 Several patents claim alginates incorporated in the collagen suspension before extrusion modify the characteristics of collagen sausage casings. 171 • 172 Recently an alkali metal calcium alginate was found to improve the quality of soft and/ or clear wheat flours enabling these lower quality flours to perform in yeast-raised dough products. The addition of about 0.2 to 1.0 parts of alginate to 100 parts of soft flour and/ or clear flour, which was treated to reduce the pH to 4.5 to 5.8, imparted gas-retention and structure-forming properties to the dough product comparable to yeast-raised dough compositions made entirely with high quality, hard-wheat flour. 173 Interactions with other molecules which are not exclusively proteinaceous often fall into the classification of medical applications, rather than food. Therefore this area is only briefly discussed. One exception, however, is a patent which claims that sodium alginate increases the flavor enhancing properties of acetaldehyde and dimethyl sulfide in foods. 174 The hemostatic action of alginates is well known. Since alginates are gradually absorbed by vascular tissues without ill effect, they have been used in surgery for many years. Blaine has written a review of the various uses for alginates in surgical practice, 175 and earlier a patent describing the use of alginate sponges to absorb various biological fluids was mentioned. 133 A recent Russian patent claims a composition for the treatment of large wounds and burns which contain 30 to 50% by weight of calcium or sodium alginate, along with tetracycline, methyluracil, glycerol, and collagen. 176 The composition is claimed to accelerate the regeneration of damaged tissues, prevent growth of microorganisms and reduce the amounts of wound dressing material used during treatments. The composition apparently is particularly well suited for treatment of deep and extensive burns before plastic surgery. 4. General Colloidal Properties The last area of alginate salt applications to be considered depends on their general colloidal

176

Food Hydrocolloids

properties, such as the ability to physically bind water. McDowell succinctly rationalized the use of alginates for such areas when he said, '"In these applications where it can be said that colloidal properties are important, alginates have generally been chosen on an empirical basis. In many cases the system as a whole is so complex that little can be predicted about the effect of changing one ingredient and results are best obtained by making tests with different formulations and under different conditions. •m7 Some application areas which utilize algin 's general colloidal properties are ice crystal control in frozen foods and desserts, suspension of solids, prevention of liquid separation (syneresis), and modification of flow properties. In a medical application, sodium alginate was found to be the best hydrocolloid for increasing the rate of morphine sulfate release from silicone polymer pellets. The researchers theorized that the sodium alginate in the silastic pellet caused it to swell, when brought in contact with moisture, probably producing channels through which the drug could diffuse more rapidly. This was found to be a very helpful phenomenon in their particular research. 178 Aside from having a great ability to absorb free water, alginate solutions can be useful to "dewater" other materials. In 1978 Union Carbide patented the use of alginate solutions to dewater collagen casings. 179 Solutions of about l % sodium alginate were used to reduce the moisture content of regenerated collagen sausage casings prior to heat drying of the casings. Dewatering is accomplished simply by passing freshly regenerated casing through the alginate solution. Diluted alginate solutions can subsequently be concentrated and reused. Suzuki 180 used a sodium alginate solution (0.1 %) to suspend lactic acid bacteria, which were subsequently freeze dried. He claimed cultures prepared in this way remained viable over 6 months and were as suitable for assays of amino acids or vitamins as those preserved by conventional time-consuming and sophisticated methods. The alginate is possibly acting as a protective colloid, preventing large ice crystal damage to the bacteria during freezing. lgoe 181 utilized the colloidal properties of sodium alginate, propylene glycol alginate, guar gum, and carrageenan to produce a composition suitable for stabilizing both soft serve and hard frozen yogurt, at a concentration of 0.2 to 0.3% (by weight).

C. Propylene Glycol Alginate Applications These organic derivatives have significantly extended the application areas for algin. By blocking a large fraction of the carboxyl groups (50 to 85%) with propylene glycol ester groups, PGAs are rendered soluble in acid solutions which would precipitate unesterified sodium alginate as alginic acid. Reactivity based on electrostatic interactions (e.g., with ions such as Ca+ 2 or with ionic polymers), is also reduced as a result of this carboxy group blocking. The propylene glycol groups are considerably more lipophilic than carboxyl groups, so this derivatization produces a molecule having both lipophilic and hydrophilic portions, resulting in enhanced emulsifying and foam stabilizing characteristics. 1. Tolerance to Acidic Environments Tolerance to acidic environments (low pH) is one of the unique properties that makes PGAs useful for such applications as salad dressings, fruit juice drinks, and other acidic foods that need stabilization. Salad dressing is probably the best known application for these algin derivatives. Pourable salad dressings (French, Russian, Italian, etc.), which contain approximately 35 to 40% oil, normally utilize about 0.5% of a medium to low viscosity propylene glycol alginate to produce a smooth, creamy dressing with flow properties nearly identical to those obtained with the older standard dressing stabilizer, gum tragacanth. A typical PGA-stabilized French dressing formulation is given below.

177

FRENCH DRESSING' 82 Typical 35% oil formulation

Percent

Vegetable oil Water Tomato puree Vinegar. 100 grain Cider vinegar Sugar Salt Paprika Propylene glycol alginate (KELCOLOID® LVF - Kelco Division of Merck & Co., Inc.)

35.00 32.35 9.00 8.35 5.50 5.50 2.00 I. 50 0.50

100.00

Procedure - place water in the mixing tank and add tomato puree or juice. Dry blend the PGA with dry spices (except salt) or slurry in three parts of oil and add to liquid in tank under vigorous agitation. Continue agitation about 2 min for 25 gal batch; 8 min for 100 gal batch. Add vinegar, sugar, salt, and liquid spices, if used. Continue agitation for 2 to 4 min until dissolved. Add oil, while mixing. After mixing thoroughly, pump the mixture through a colloid mill, then to the filling machine.

Steiner and McNeely stated that ••the propylene glycol alginates combine in the same molecule the action of a true emulsifier with the thickening and protective colloidal properties of the gums". 183 The work of Weber indicated that the PGAs were more effective at stabilizing emulsions than gum tragacanth. 75 For this reason, as well as lower cost, better availability and greater ease of use, these organic derivatives of algin gradually have replaced gum tragacanth in most dressings. Today, propylene glycol alginates are most frequently used in combination with xanthan gum, rather than alone. Xanthan gum can be used at about 1/2 the level of low viscosity PGA to give superior long term stability. Hence it has become the gum of choice for pourable dressings. PGA is very useful for modifying the rheology of xanthan gum stabilized dressings as it helps to produce a ··1onger" flow than the typical ••shorter" flow obtained with xanthan gum alone. Usually low viscosity PGA is used for bottled pourable dressings, instead of high viscosity PGA, because of its greater viscosity stability. The emulsifying characteristics of PGAs are also used in dressings which need additional emulsification because they lack natural emulsifiers. High viscosity PGAs are often used in spoonable dressings, at levels of 0.05 to 0.15%, to give a ••set" similar to that obtained with starch. The use of a PGA can also increase stability against shock and other adverse conditions to which the dressing may be exposed during shipping. Preparation of PGA-stabilized dressings is quite simple. Usually it is most convenient to disperse the PGA in 3 to 5 parts of oil and add this to well mixed water or water/vinegar. Salt, which inhibits hydration, should not be added to the system until PGA hydration is complete. Generally speaking, the more efficiently emulsified the dressing, the better will be its long-term stability. Care should also be taken to ensure that pH does not fall below 3.2, otherwise gradual viscosity loss will be experienced over a period of months. A 6 to 9 months shelf-life is easily attainable with PGA-stabilized pourable dressings. Fruit-flavored juice drinks are another application area where these algin derivatives have been very useful. In these products the high viscosity PGAs are normally used to impart body (mouthfeel), to provide suspension of pulp, and in some cases to impart emulsion

178

Food Hydrocolloids

stability (i.e., prevent separation of citrus oils). They have also been used for the purpose of preventing •~ leakers,. when juice drinks are packed in Pure Pak containers (coated paper). Typical usage levels for the high viscosity PGAs are 0.1-0.2%. Although juice drinks and dressings are the most common application areas which depend on the acid stability of PGAs, there are other acidic products which also can utilize these algin derivatives. High viscosity PGA is the best stabilizer to use in ice cream fruit toppings, for example. In a concentrated topping formulation, as shown below, 0. 70% PGA functions to provide a clear, high viscosity topping which clings well to ice cream sundaes. Of equal importance is its function during processing, where it prevents the fruit from floating so that uniform container filling can occur.

CONCENTRATED STRAWBERRY TOPPING 184 Ingredients

Percent

Frozen strawberries (20° Brix) Sugar Dextrose High viscosity PGA (KELCOLOID® HVF - Kelco, Division of Merck & Co., Inc.) Citric acid (anhydrous) Sodium benzoate Flavor & color

62.50 26.41

10.00 0.70

0.27 0.12 to suit

ioo.oo

Procedure ~ carefully dry blend the PGA with 10 parts of granulated sugar. Heat fruit and remaining sugar and dextrose to about 120°F (49°C) while mixing gently. Add PGA/ sugar blend slowly while gentle mixing is continued. Heat to 150°F (66°C). Add sodium benzoate and citric acid along with color and flavor. Check the brix and adjust with water 52° to 55°, if necessary. Note: This topping may be diluted with I to 3 parts of simple syrup (65% sucrose in water).

When using high viscosity PGAs, it is important to apply heat carefully, since they are degraded under extended heat processing conditions. This is the reason for heating only to 150°F (66°C) and adding the PGA after the batch reaches 120°F (49°C). Fruit flavored table syrups are typically low in viscosity unless an acid stable gum, such as propylene glycol alginate, is added. The PGAs also serve as excellent stabilizers for sherbet and water ice formulations. 2. Lipophilic Characteristics The lipophilic characteristics of PGAs make them extremely useful as stabilizers for buttered syrup, beer, certain types of drinks, milk shakes, and also salad dressings. When PGAs are used primarily for these lipophilic properties, the highly esterified products are normally chosen since the higher the degree of esterification the more lipophilic and surface active the PGAs are. An additional factor to consider is viscosity. Quite often a low contribution to viscosity from a PGA is desirable (in beer, for example), and the highly esterified derivatives fit this requirement (1 % solutions are usually less than 100 cP). Beer is a significant application area for the highly esterified PGAs. PGAs have been used for many years, at 40 to 100 ppm, to stabilize beer foam, especially against adverse conditions. Such stabilized beer foam resists breakdown in the presence of soap and other sanitizing agents used in washing glassware, and various fatty materials derived from peanuts, popcorn, potato chips, lipstick, etc.

179

In the brewery, a stock solution of PGA is prepared and added during the final stages of processing. This is best accomplished by proportioning the solution into the beer line: (I) after primary filtration; (2) after the finishing stage but before final filtration; or (3) after final filtration. For best results the PGA solution should be uniformly proportioned by metering against the beer flow. " 5 PGA is particularly useful for stabilizing many of the lower calorie beers that have become popular. Since these beers typically contain lower protein levels than regular beers, sufficient foaming or heading qualities can be very difficult to achieve. Preservatives used in beers also adversely affect heading qualities. For example, heptylp-hydroxybenzoate, which may be added as a preservative to allow beer production without pasteurization, has a detrimental effect on beer foam stability. According to Strandskov, these adverse effects can be overcome by inclusion of PGA. 186 Buttered syrup is another application area for highly esterified propylene glycol alginate. This syrup product was developed by Lever Brothers Company and patented in 1962. 187 Buttered syrup is a table syrup (67° brix, and usually maple-flavored) with approximately 2% butter added. About 0.5% PGA is added so that when the syrup is homogenized, the resulting '"fine'~ emulsion is stabilized to prevent butter separation. Buttered syrup formulated using PGA will normally be limited in shelf-life due to flavor degradation rather than phase separation. Since PGAs are more sensitive to prolonged heating than alginate salts, steps should be taken during processing to limit high temperature exposure [temperatures greater than 15011F (66°C)] of the PGA, and salt should be held out of the batch until hydration of the gum is complete. As mentioned earlier, salt inhibits PGA hydration. Various other food systems which need foam stability or emulsification without the accompanying high viscosity normally associated with gums, can often benefit by the use of highly esterified PGAs. The following formula for an orange-flavored drink with a foamy '"head" is an example. The PGA acts as the foam stabilizer while xanthan gum provides viscosity ('"body") for the drink. 188

WHIPPED ORANGE DRINK Ingredients

Percent

Sugar, fine granular Citric acid, hydrous Natural and artificial orange flavor Propylene glycol alginate (KELCOLOID® S Kelco, Division of Merck & Co., Inc.) Xanthan gum (KELTROL® - Kelco, Division of Merck & Co., Inc.) Sodium citrate, hydrous Artificial cream flavor # 13527058 (!FF) VAN-O-PLUS # I 0293 artificial vanilla flavor Titanium dioxide FD&C yellow #5 FD&C yellow #6

95.328 2.200 0.800 0.500 0.500 0.300 0.200 0.080 0.080 0.006 0.006

ioo.ooo

Procedure - weigh and pre-mix all the ingredients. To 246 mt' (1 cup) of ice water in a blender, add 29 g (1 oz) of dry mix. Whip for l min.

Separating salad dressings, especially those prepared from dry mixes (Italian-type), can

180

Food Hydrocolloids

also be stabilized with the highly esterified PGAs. Use of PGAs of higher viscosity and lower degree of esterification would tend to produce dressings which do not separate cleanly after shaking. For these dressings only temporary emulsification is desired followed by clean phase separation. 3. Other Uses for PGAs Proteins can also react with PGAs, as well as alginate salts, under certain conditions. Generally speaking, however, PGAs are less reactive than unesterified alginates because they contain fewer reactive sites, namely carboxylate anions. Consequently, if protein reactivity is not desired, PGAs are preferred over sodium alginate. At pH values below the isoelectric point of a protein, alginate reactivity with the protein decreases in the following order: alginate salt > medium substituted PGA > highly substituted PGA. Reactivity with proteins can be desirable, however. McDowell claims that this protein reactivity is one reason why PGAs function well to prevent phase separation in salad dressings, where the interaction leads to thixotropic gel formation. He also states that, '"in a similar way to the reaction with calcium, the viscosity increase with the protein diminishes with an increase in the degree of esterification of the alginate. The type of alginate ester can, therefore, be chosen to give the flow properties required,. .68 McDowell also discovered that under mildly alkaline conditions propylene glycol alginates can react with proteins and other polymeric molecules, such as starch, in a way which suggests that some type of cross-linking takes place. 189 Rheological changes (i.e., viscosity increases) were observed when the pH was raised to 8 to 9, when temperatures are kept low (20°C or 68°F, for example). PGA can be made to react with gelatin (at 40 to 50°C or 104 to 122°F), giving a quick setting gel (by raising the pH above IO with sodium carbonate) that will not melt even at boiling. Use of PGA under alkaline conditions to form a thermostable gel is patented by Carpenter et al. 190• 191 The process is claimed to be especially useful for reconstitution of denatured fish protein (e.g. , protein denatured by heating or by protein concentration during extraction processes). In a preferred example, a mixture of 17 to 25 weight % of dry powdered fish protein concentrate, 0.6 to 2.0 weight% of PGA (at least 50% esterified), and the remainder water, are mixed and the pH adjusted to 7.9 to 9.5 to form the gel. Preferably the mixture is extruded (e.g., as fibers, ribbons, rods, etc.) into an alkaline bath to form the solid gel. The extruded products may then be chopped and incorporated with normal filleted fish, e,g., in the production of fish sticks. The process allows denatured protein and fish scraps to be converted into foodstuffs suitable for human consumption. 190 • 191 Stabilization of a flavoring agent (acetaldehyde) by the use of a highly esterified PGA is patented by Knapp. 192 The process involves preparing an aqueous solution containing 45 to 60 weight % of a mixture of lactose, PGA, starch hydrolyzate, and the flavoring agent, acetaldehyde. The amount of acetaldehyde utilized in the aqueous solution is 10% by weight of the total added solids, giving a 6% level of stabilized acetaldehyde in the resulting compositions. The solution is then spray dried, preferably to a moisture content of 5% or less, to produce the stabilized acetaldehyde compositions. Accelerated stability tests (I00°F or 38°C and 10% RH in open containers for 4 weeks) showed that the acetaldehyde content did not drop below 4% (it was 6.2% initially) and samples of the spray-dried material stored in a sealed glass jar for I year still contained 5.5% acetaldehyde. The stabilized acetaldehyde composition was utilized as a flavor enhancer in dry fruit flavored beverage mixes and provided superior flavor in the resulting beverages immediately after preparation and also after the above storage periods. 193 D. Alginates in Product Development Since alginates are commonly used because of their unique functionality, such as gelation with calcium ions, the technical information in this chapter is organized around their special

181

properties and functionality. Examples of food systems based on the property under discussion are presented in each respective section to illustrate how that unique property can be used to design new products. In this section general guidelines and suggestions, designed to aid in the use of alginates for development of new or improved products, are presented. I. Information Gathering Information gathering is the logical starting point. This chapter and other sources of technical information should be reviewed to gain familiarity with the special characteristics of algin. Technical objectives should be clearly defined. A few of the possibilities are listed below: l. 2. 3.

The final product requirements (e.g., storage conditions, clarity, shelf-life, packaging, etc.) The function algin is expected to perform (e.g., provide viscosity, gel, provide emulsion stability, etc.) The processing conditions required to make the product (e.g., dry blending, HTST pasteurization, sterilization by canning, freezing, etc.)

The type of alginate needed should be determined, based on the function it must perform and constraints imposed by product and processing requirements. Consultation with other individuals experienced in the use of alginates can often be beneficial. Both intercompany and supplier technical resources should be considered. Fresh samples of alginates should be obtained from suppliers along with technical literature on the alginates. Application literature may also be available from suppliers, e.g., balanced formulations which may serve as prototypes or at least starting points for product development. In certain cases actual samples of these application formulations are also available, especially if the product is a dry mix for addition to water or milk. 2. Evaluation and Modification Evaluation and modification of the gathered information is the next step. If prototype or starting formulations are available, they should be evaluated. It is nearly always easier to start with a balanced formulation, especially in the case of algin gels prepared from dry mixes, than to begin building a completely new formulation. Make minor modifications (one at a time) in the prototype formulation. Develop a project plan of action, based on all above inputs. Consult the suppliers' technical representatives in your product development process to take advantage of their expertise. 3. Designing Original Formulations When no suitable prototype formulation is available and designing a '"uniquely new" system with the algin/calcium reaction is required, the following suggestions are offered as a general guide. Choose a suitable alginate and starting concentration. When the algin/calcium reaction is being used: to produce increased viscosity, use 0. l to 0.4% alginate (based on the aqueous phase); to make firm gels (i.e., dessert gels and gels for binding particulate material), use 0. 75 to 2% alginate (based on the aqueous phase); and to form insoluble, extensively reacted calcium alginate polymers (i.e., Algin-Tex), use 0. 75 to 2% alginate (based on the water phase at the point of CaC1 2 precipitation). The use of high molecular weight (M. W.) alginates only requires low concentrations while the highest concentrations are required when low M.W. alginates are employed. Very firm gels generally require the highest levels of algin.

182

Food Hydrocolloids

Proper hydration of the alginate must be achieved to obtain the desired effect. Incomplete hydration will normally be evidenced by .. fish eyes" - small, irregularly shaped particles which can be seen if a thin film of the algin solution is spread on the side of a transparent container (e.g., a glass beaker). If '"fish eyes" persist, one or more of the following may be necessary: l. 2. 3. 4.

Improve dispersion techniques to prevent clumping of the algin when it contacts water Change processing conditions (heating, homogenization, mixing equipment, etc.) Sequester available calcium (add sequestrant until '"fish eyes" disappear) Adjust an acidic environment to a pH level that will allow the alginate to dissolve

Select the appropriate calcium salt (see Table 10). Determine the amount of the calcium salt needed to achieve product requirenents. With the addition of a partially soluble calcium salt (e.g., calcium sulfate) sequestrant adjustment may be necessary to obtain proper algin solubility and to control the calcium/algin reaction '"set" time. In the case of calcium salts of very limited solubility at neutral pH (e.g., CaC0 3), an acid will probably be needed to release calcium ions to react with the algin. Consequently, a proper acidulant must be chosen and its optimum concentration determined (see Table 11 ).

Optimization of all critical ingredients (i.e., alginate, calcium salt, sequestrant, and acidulant) is the last step in designing the calcium/algin system. It is important that only one ingredient be varied while all others are held constant. Whenever the algin level is changed, the other critical ingredients will usually. require slight adjustments (i.e., reoptimization).

ACKNOWLEDGMENT Many individuals within the KELCO Division of Merck & Company, Inc. have contributed significantly to making this chapter possible. Dr. Ian Cottrell wrote several chapter sections and information for various tables was supplied by J. K. Baker, Alec N. Bennett, and A. A. Jenkins. S. J. Shepherd provided valuable assistance by way of literature searches. Many thanks are due these individuals, as well as those who spent considerable time editing and reviewing the manuscript. Especially notable among the latter group was Dr. G. R. Sanderson, who was an invaluable resource. W. C. MacLeod, Dr. D. J. Pettitt, W. J. Sander, Dr. Ken Clarke, and W. Bryden were also instrumental in the reviewing process. I wish to express my deep appreciation for the support and contributions of each person that had a part in producing this chapter.

183 Table 13

APPLICATION REFERENCES Application Bakery/bakery supply products Baked goods Bakery jellies and fillings "Jellies" or spreads Beverages Alcoholic Non-alcoholic Dairy and dairy-type products Non-frozen Frozen Desserts (puddings, pie fillings. etc.) Puddings Pie fillings Others Films Gels Dessert Other Medical and pharmaceutical Dental Pharmaceutical Medical Pasta Protein products Restructured products General Fruit-like Fish/meat-like Vegetables Salad dressings Sauces Syrups and toppings

Page(s) 174, 175 145F, 154, 162, 165F, 174F l39F, l74F 161, 175, 178 172, 174, 172-t-78, 179F 131 , 153-154, 155, 156F-157 156, 157, 163F, 168, 176 162, 139, 162, 161,

163F, 164F, l68F 140F 168F 174, 176

162, 165F-166 135-136, 138-140, 144-145, 158, 161-163, 167, 180 132, 162, 162, 167 161,

162, 174 163F, 174, 176 167, 172, 174, 175-176 172-173, 175, 176, 180

159, 162, 167, 169-175 159-162, 167, 169-170, l71F 159-161, 166F, 167, 169-171, 172F, 176, 180 132, 159-161, 169-173 153, 176, 177F 154F, 155 156, 174, 178F, 179

Note: When "(F)" follows a page(s) number, it indicates that there is a formulation on that page.

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Food Hydrocolloids

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186

Food Hydrocolloids

102. Carpenter, R. P., Cowie, W. P., Heyes, A., and Sutton, A.H., British Patent 1,414,131, 1975; U.S. Patent 3,891,776, 1975. 103, Glicksman, M., Gum Technology in the Food Industry, Academic Press, New York, 1969, 255-256. 104. Earle, R., U.S. Patent 3,395.024, 1968. 105. Earle, R., U.S. Patent 3,493,398, 1970. 106. Earle, R. D, and McKee, D. H., U.S. Patent 3,991,218, 1976. 107. McKee, D. A., U.S. Patent 4,066,796, 1978. 108. Earle, R. D., U.S. Patent 3,865,962, 1975. 109. Distillers Co. (Yeast) Ltd., British Patent 1,198,498, 1970. 110. Glicksman, M., Gum Technology in the Food Industry, Academic Press, New York, 1969, 257-259. 111. Suminoe, K., Japanese Patent 20,378, 1972. 112. Meiji Seika Kaisha Ltd., Japanese Patent 27,780, 1970. 113. Meiji Seika Kaisha Ltd., Japanese Patent 17,941, 1971. 114. Shorewood, J. S. and Sandine, W. E,, U.S. Patent 3,733,205, 1973, 115. Glass, R. W. and Glogowski, J., U.S. Patent 4,259,445, 1981. 116. Lim, F. and Sun, A. M., Microencapsulated islets as bioartificial endocrine pancreas, Science, 210, 908190, 1980. 117. Kierstan, M. and Bucke, C., The immobilization of microbial cells, subcellular organelles, and enzymes in calcium alginate gels, Biotechnol. Bioeng., 19, 387-397, 1977. 118. Morishita, J. K. K., Japanese Patent 56,049,153, 1979. 119. Metal Box Co., Ltd., Capsules containing microorganisms immobilized in alginate gel without impairing heat resistance, British Patent 1,595,054, 1981. 120. Anon., Kelco Algin Food Gels, Technical Bulletin F#41, Kelco Division of Merck & Co., Inc., San Diego. 1978. 121. Patterson, B. A., U.S. Patent 3,806,605, 1974. 122. Anon., Kelco Algin for Impression Materials, Technical Bulletin PH #5, Kelco Division of Merck & Co., Inc., San Diego, 1970. 123. Anon., Food Formulation SS-4389, Kelco Division of Merck & Co., Inc., San Diego, 1976. 124. Messina, B. T., Canadian Patent 788,940, 1968. 125. Gardner, W. H., Choosing an acidulant, Food Acidulants, Allied Chemical Corp., New York, 1966, 1315. 126. Gardner, W. H., Acidulants in food processing, in Handbook of Food Additives, Furia, T. E., Ed., CRC Press, Inc., Cleveland, 1968, 255. 127. Miller, A. and Rocks, J. K., Canadian Patent 811,682, 1969. 128. Anon., Food Formulation SS-4400, Kelco Division of Merck & Co., Inc., San Diego, 1978. 129. Heinen, J. M., Evaluation of some binding agents for crustacean diets, Prog. Fish-Cult., 43(3), 142145, 1981. 130. Chimirov, Yu. I., Braudo, E. E., and Tolstoguzov, V. B., U.S.S.R. Patent 615,913, 1978. 131. Hawley, R. L., U.S. Patent 3,658,550, 1972. 132. Shalunova, G. I., Baranov, V. S., Trofimovia, V. I., and Brunnek, N. I., U.S.S.R. Patent 282,915, 1970. 133, Wise, Raymond, G., Algin Sponge and Process Therefore, U.S. Patent 3,653,383, 1972. 134. Unilever, N. V., Netherlands Patent Application 7,306,441, 1973; Wood, F. W., U.S. Patent 3,892,870, 1975. 135. Unilever Ltd., British Patent 1,369,199, 1974. 136. Unilever Ltd., British Patent 1,369,198, 1974. 137. Anon., Kelco Desserts and Bakery Fillings, Technical Bulletin F #56, Kelco Division of Merck & Co., Inc., San Diego, 1978. 138. De Muynck, E. P. L., and van Brantegbem, A. E., Netherlands Patent Application 6,801,430, 1969. 139. De Muynck, E. P. L., and van Brantegbem, A. E., Netherlands Patent Application 6,801,431, 1969. 140. Unilever, N. V., Netherlands Patent Application 7,105,266, 1971. 141. Anon., The Algin-Tex System, Technical Bulletin F-82, Kelco Division of Merck & Co., Inc., San Diego, 1981. 142. Anon., Food Formulation SS-4715, Kelco Division of Merck & Co., Inc., San Diego, 1981. 143. Anon., Food Formulation SS-4578, Kelco Division of Merck & Co., Inc., San Diego, 1981. 144. Niwano, S., Japanese Patent 14709, 1971. 145. Cain, R. M. and Steele, J. H., The use of calcium alginate soluble wool for the examination of cleansed eating utensils, Can. J. Pub. Health, 1953. 146. Posse, E. R. G. and Blaine G., Alginates in endural wound dressing, Lancet, 2, 651, 1948. 147. Oliver, L. D. and Blaine, G., Haemostasis with absorbable alginates in neurosurgical practice, Brit. J. Surgery, 31, 1-4, 1950.

187 148. Glicksman, M., Cardohydrates for fabricated foods, in Fabricated Foods, Inglett, G. E., Ed., AVI Publishing, Westport, Conn., 1975, chap. 8. 149. Ishler, N. H., Macallister, R. V., Szczesniak, A. S., and Engel, E., U.S. Patent 3,093,483, 1963. ISO. Atkinson, W. T., U.S. Patent 3,455,697, 1969. 151. Atkinson, W. T., U.S. Patent 3,645,746, 1972. 152. Castaigne F., Reil, R. R., and Boulet, M., Process for the production of textured products, Brevet Canadien, No. 1,000,995, 1976. 153. Castaigne, F., Riel, R. R., and Boulet, M., Rheological properties of soy proteins containing alginates, (French) Can. Inst. Food Sci. Technol. J., 8, 129, 1975. 154. Castaigne, F., Riel, R. R., and Boulet, M., Diffusion of water and soluble solids during the coagulation of protein fibers, Can. Inst. Food Sci. Technol. J., 8, 133, 1975. 155. Pommier, S., Castaigne, F., Simard, C., and Boulet, M., Study of the rehydration of dried protein fibers containing sodium alginate as the texturizing agent, (French), Can. Inst. Food Sci. Technol. J., 12, 117-122, 1979. 156. Rusig, 0., Evaluation of plasma and plasma-alginate fibres for use in sausages, Meat Science, 3, 295307, 1979. 157. Imeson, A. P., Mitchell, J. R., and Ledward, D. A., Rheological properties of spinning dopes and spun fibres produced from plasma-alginate mixtures,]. ofFoodTechnol., 15, 319--327, 1980. 158. Downey, G. and Burgess, K. J., Texture studies on edible protein fibres produced by a wet spinning technique, J. Food Technol., 14, 33-40, 1979. 159. Arima, T. and Harada, Y., Method of producing protein-aceous fibers, U.S. Patent 3,627,536, 1971. 160. Anon., Food Formulation SS-4515, Kelco, Division of Merck & Co., Inc., San Diego, 1980. 161. McDowell, R.H., Properties ofAlginates, Alginate Industries, Ltd., London, 44, 1977. 162. Cross Paperware Ltd., British Patent 2,055,737, 1981. 163. Moirano, A. L., Sulfated seaweed polysaccharides, in Food Colloids, Graham, H. D., AYI Publishing Co., Westport, Conn., 1977, chap. 8. 164. Ganz, A. J., Cellulose hydrocolloids, in Food Colloids, Graham, H. D., AVI Publishing Co., Westport, Conn., 1977, chap. 9. 165. Snoeren, Th. H. M., Payens, T. A. J., Jeunink, J., and Both, P., Milchwissenschaft, 30, 393, 1975. 166. Gurov, A. N., Vainerman, E. S., and Tolstoguzov, V. 8., Starke, 26, 172, 1974. 167. Imeson, A. P., Ledward, D. A., and Mitchell, J. Q.., On the nature of the interaction between some anionic polysaccharides and proteins, J. Sci. Food Agric., 28, 661-668, 1977. 168. Shelomkova, I., Ya. and Vlodavets, I. N., U.S.S.R. Patent 459,207, 1975. 169. Delapp, D. F., U.S. Patent 3,762,929, 1973. 170. Courts, A. and Bradshaw, N. J.,. U.S. Patent 3,494,773, 1970; &nadian Patent 788,938, 1968. 171. Glicksman, M., Gum Technology in the Food Industry, Academic Press, New York, 261, 1961. 172. Nitta Zerachin Co., Ltd., Japanese Patent 23,384172, 1972. 173. Fischer, L. G., Russell, A. W., Vey, J.E., and Kovacs, P., British Patent 1,570,166, 1980. 174. Szczesniak, A. S., U.S. Patent 4,015,025, 1977. 175. Blaine, G., Nursing Times, XIVII, No. 24 (J. of the Royal College of Nursing, Lesquare, London), June 16, 1951. 176. Russian Patent 740,251, 1980. 177. McDowell, R.H., Applications of alginates, Rev. Pure Appli. Chem., IO, (I), 1-19, 1960. 178. McGinity, J. W. and Mehta, C. S., Preparation and evaluation of a sustained morphine delivery system in rats, Pharm. Biochem. Behav., 9(5), 705-708, 1978. 179. Higgins, T. E., Method of preparing collagen structures, U.S. Patent 4,110,479, 1978. 180. Suzuki, T., Improvements in or relating to lactic acid bacteria, British Patent 1,543,098, 1979. 181. Igoe, R. S., Compositions for stabilizing soft serve and hard frozen yogurt, U.S. Patent 4,178,390, 1979. 182. Anon., KELCOLOID ® LVF in French Dressings and other Dressings, Technical Bulletin F#30, Kelco Division of Merck & Co., Inc., San Diego, 1977. 183. Steiner, A. 8. and McNeely, W. H., Organic derivatives of alginic acid, Ind. Eng. Chem., 43, 2073, 1951. 184. Anon., Concentrated fruit toppings with KELCOLOID® HVF, Food Formulation SS-4364, Kelco Division of Merck & Co., Inc., San Diego, 1973. 185. Anon., KELCOLOID® 0 gives beer a more stable, longer lived, creamier foam, Technical Bulletin F#20, Kelco Division of Merck & Co., Inc., San Diego, 1968. 186. Strandskov, F. B. and Zillotto, H. L., Beer chill stability, U.S. Patent 3,469,992, 1969; West German Patent 1,442,343, 1968. 187. Pader, M., Process for making table syrup and product thereof, U.S. Patent 3,057,734, 1972. 188. Anon., Product Formulation SS-4724, Kelco Division of Merck & Co., Inc., San Diego, 1981.

188

Food Hydrocolloids

189. McDowell, R. H., New reactions of propylene glycol alginate, J. Soc. Cosme1. Chem. , 21, 441-457, 1970. 190. Unilever, N. V., Regeneration of denatured protein material by fanning a thermo stable gel, Japanese Patent 81,001,056, 1981. 191. Carpenter, R. P., Weddle, R. B., and Wood, F. W., British Patent 1,433,513, 1976; U.S. Patent 3,873,749, 1975. 192. Knapp, W. A., Stabilized flavoring agent, U.S. Patent 3,736,149, 1973. 193. Lawrence, A. A., Edible Gums and Related Substances, Food Technology Review No. 9, Noyes Data Corp., Park Ridge, New Jersey, 1973, 151-153.

Index

Taylor & Francis Taylor & Francis Group

http://taylorandfrancis.com

191

INDEX A Absorption, of carrageenan, 85-86 Acacia campylacantha. 8 drepanolobium, 8 laeta, 8, 15 senegal, 8, 15 gums from, 17 seyal, 8, 15 verek, see Acacia senegal Acacia tree, 8, 9, 11 gums produced by. 4 Acceptable daily intakes (ADI), for alginic acid salts, 118 Acetaldehyde, stabilization, by propylene glycol alginate, 180 Acetyl groups, in gum karaya, 41 Acid(s) solubility of alginates in, 131-132 use in alginate food systems, 148, 152 "Acid gel", 135, 164-167 alginate. 138--140 formation, 136 Acid hydrolysis, 125 Acidic environments, tolerance of propylene glycol alginate to, 176-180 Acidified milk gels, use of carrageenan and furcellaran in, 100-101 Acid precursors, use in alginate food systems, 148, 152 Acid stability. of gum tragacanth, 53, 54, 55 Acidulants. use in alginate food systems, 148, 152 Acid value, of alginates, 117 Adhesive properties, of gum karaya, 44 Adipic acid(s), 157, 165 Agar. 64 applications. 8-83 background, 74--75 producion. 76-77 properties, 79-80 regulatory status, 75-76 structure, 78--79 chemical, 69, 70 Agar-agar, see Agar Agaran, see Agarose Agaropectin, in agar, 78, 79 Agarose, in agar, 70, 78 Air flotation, of gum karaya, 41 Algae, see Seaweed "Algic acid,,., 125 Algin, see Alginate Alginate(s), 46, 64 application in food sytems, 183 alginate salt application, 173-176 calcium/algin interaction, 154--173 product development and, 18~182 propylene glycol alginate application, 176180

backgrgund, I 16-117 business developments, 69 commercially available types, 148 concentrations, gel strength and, 158 description, 177 high molecular weight, 18 I interaction with other molecules, 175 manufacture, 66, 118--125 properties, 116-117 compatibilities, 154 interaction with polyvalent metal cations, 141=154 physical, 127-128 solution, 128--132 viscosity, 132-141 regulatory status, 117-119 structure, 125-127 Alginate acid gels, characteristics, 138--139 reset, 139-140 Alginate/calcium gels, 138 classification, 159 Alginate fibers, production, 172-173 Alginate gel(s), 144, 157 algin concentration and, 158 diffusion setting, 159-160 formation and properties, 144 calcium salts and, 147-151 factors influencing, 157, I58 internally set, temperature influenced, 168 internal setting, 162-168 reaction with calcium ions, 143 Alginate salt(s), 153 Alginic acid derivatives, 148 description, 117 production, 123 properties, 127 solubility in water, 129 propylene glycol esters of, 153 structure, I 16, 125-127 Alkali, in carrageenan, 87 "Amas", 76-77 Ammonium, 86 gel formation and, 157 Ammonium alginate, 116, 117 Ammonium salt procedure, 78 Anhydrogalactose, 86 3 ,6-Anhydro-o-galactose, 84 in carrageenan, 87, 88 in iota carrageenan, 89, 92 in kappa carrageenan, 89 in furcellaran, 89 polysaccharides of, 83 3,6,Anhydrogalactose copolymers, 84 3,6,Anhydro-o-galactose-2-sulfate, in iota carrageenan, 89 Angogeissus latifolia tree, 32 Antibiotics

192

Food Hydrocolloids

manufacture, 66 use of agar in, 83 Anti-staling agent, 81 Anti-tackiness agent, 81 Applications, table of, 183 Aquaculture, for seaweed production, 64, 66, 67 Aqueous systems, solubility of alginates in, 131132 Arabic, see Gum arabic Arabic acid, 15 L-Arabinofuranose in arabinogalactin, 54 in gum arabic, I5 in gum tragacanth, 52 L-Arabinofuranose residues in gum ghatti, 33 in tragacanth, 52 Arabinogalactan, 52 properties, 54 Arabinopyrasone, in gum arabic, 15 Arabinose, in gum arabic, 17 L-Arabinose, in gum ghatti, 33 Ascophyllum nodosum, I 19 alginic acid from, 127 production, I 23 Ash, in gum arabic, 13, 15 Astralagus plants, 50 gum produced by, 4

B Bakery filling, eggless-milkless, 145-146 Bakery jelly, instant imitation, 165 Bakery products, 183 agar and, 80-8 I gum arabic and, 24 gum karaya and, 46 gum tragacanth and, 57, 58 Bassorin, see Tragacanthic acid Beer use of furcellaran in, I 07 use of propylene glycol alginate in, 179-180 Benzoate, 171 Benzoic acid, 132 Beverage(s), see also Applications, Table of agar in, 83 fruit, use of carrageenan in, I 05-106 gum arabic in, 23-24 SHA, see Butylated hydroxyanisole Bixaecae, see Cochlospermum Kunth Blue-green seaweed, 64 Blue seaweed, 64 Breakfast beverages, use of carrageenans in, 99 Branching, 42 Brewery, use of propylene glycol alginate in, 179180 Brown, seaweed, see also Phaeophyceae, 64, 75, 115-183 extracts, see Alginate Bulking agent, gum karaya as, 45

Bums, treatment of, use of alginates for, 175 Bushes, gum exudates from, 4 Buttered syrup, use of propylene glycol alginate in, 179 Butylated hydroxyanisole (SHA), composition, 26

C Cake mixes, use of algin in, 174 Calcium, 84, 86 in alginates, I 16, 123, 152, 153 in gum arabic, 15 Calcium alginate, I 17 production, 123 properties, 129 Calcium/alginate gel, 135 classification, I59 Calcium/algin interactions control, ingredients used, 146 food applications of, 154-173 insoluble polymer production and, 168-173 properties, 144-146 theory and mechanism, 141-144 Calcium carbonate (CaCO 3), 147 Calcium cations, in tragacanthic acid, 51 Calcium chelating agents, 146 Calcium chloride (CaCI,), 171 for alginate manufacture, 123 Calcium glutonate, 163, 167 Calcium ion(s), see also Calcium cations alginate gels and, 157, 158 alginate hydration and, 132 in alginates, 132 gum ghatti viscosity and, 35 in gum karaya, 41 reaction with alginates, 131 sequestrants, 146, 147 Calcium lactate, 167 Calcium retarding agents, 146-147 Calcium salt(s) blend with alginates, 153 in gum ghatti, 32 in karaya gum, 42 selection, 182 use in formation of alginate gels, 147-151 Calcium sequestrating agents, 146 Calcium sulfate dihydrates, 158 Candy, see Confection Canned meat and fish products, use of carrageenan and furcellaran in, 104-105 Carboxylate anions, 133 Carboxyl groups, protonation of, 135 Carrageenan, 46, 64, 75 applications, 83, 94-107 background, 83-84 business developments, 69 production, 64, 66, 86-88 properties, 90-94 regulatory status, 84-86 structure, 88-90

193 chemical , 69. 70 iora-Carrageenan, 83. 84, 88, 89 application , 102-105 propenies, 90, 92. 94 structure, 89 kappa-Carrageenan. 64. 83, 84. 86. 88, 89, 94 applications. 97-105 properties. 90, 92. 94 structure, 89, 90 lambda-Carrageenan, 83. 84. 88. 89 applications, 97. 100. 106 properties, 90. 92 structure, 89 mu-Carrageenan, 83, 84, 89 nu-Carrageenan. 84 theta Carrageenan , 84, 88 xi-Carrageenan. 84 . 88 structure, 89 Casein fibers, production , 173 Casein fraction. reaction of carrageenan to , 94 kappa-Casein, 94 Cation(s) in alginates. 152-153 calcium . 51 effect on gum ghatti viscosity, 35 multivalent, solubility of alginates in, 131-132 potassium, 51 sodium. 86 Cellulose gum , use in bakery products. 81 Cereals. use of gum karaya in. 46 Cheese products. use of carrageenan in, 101 Chemical Abstract Service (CAS) Registry Numbers . of algin products. I 17 , 118 Chewing gum. 23 Chocolate chiffon. use of alginate for. 162-163 Chocolate milk products . use of carrageenans in . 98 . 99 Chocolate syrups. use of carrageenans in. 97 Chondrus crispus. see Irish Moss ocellatus, 85 "Cleaned amber sons" . 9 Cloud agents. 106 gum arabic as. 23 . 24 preparation, 172 Cochlospermum. 40 Coffee whiteners. non-dairy. use of carageenans in. 104 "Coldsnap" . 45 Cold water dessert gel. alginate for . 165-167 Colloidal properties. of alginates. 175----176 Color of gums. 5 Combretaceae family , 32 Compatibility gum arabic. 19. 20 gum tragacanth. 5(r.-.57 Confection(s) agar and. 81-82 carrageenan and, I0(r.-. I07 gum arabic and, 22-23. 26 gum tragacanth and, 58

Cough drops . 23 Crabmeat products, simulated. alginate polymers and , 172 Crystallization, elimination of, 45 Custards, see Puddings

D Dairy analogs, use of carrageenan in . I 03 Dairy products. applications, 183 use of agar in. 83 use of gum karaya in. 45 Dental materials , use of alginates in , 174 of alginate gels , 163-164 Dessert(s) use of agar in. 82 use of carrageenans in, 101-102, 183 Diatomaceous earth, 158 Dicalcium phosphate dihydrate, 147 Dichroism. 142 Dietary products. use of carrageenan in, 98--99 Dietetic beverages . use of carrageenans in, 99 Dietetic foods. use of gum arabic in. 23, 25 Dietetic gels and jellies, use of carrageenan and furcellaran in. 103 Diffusion setting. of alginate gel. 15~160 Diglycerides, 85 Dip base, instant, use of alginates in, 157 Dough products. use of carrageenan in, 106 Dry material dispersion methods . alginate solubility and , 130 Dry mixes. alginate gels and. 162 Dry mix products. see also Applications, Table of use of carrageenans in. 99 use of gum arabic in. 24 Dry powder stability. of alginic acid , 127-128

E Egg(s). elimination of. 100 Egg-base custard mix. use of carrageenan in, 100 Eggnog. algin stabilized, 156 Electrolytes, effect on gum arabic viscosity, 19 Electrostatic attraction, 175 Emulsifier(s) blend of alginates with , 153 gum ghatti as. 36 Emulsifying properties. of gum arabic, 19 Emulsion stabilizer gum arabic as. 24 gum karaya as, 46 Emulsion stabilizing properties. I 16-117 "Encapsulated" flavor . use of gum arabic for , 21 Environmental Protection Agency (EPA), alginates and, 118 Equilibrium moisture curves. for alginates, 127, 128 Ester sulfate. in furcellaran, 90 Ethanol. alginate hydration and , 13 I

194

Food Hydrocolloids

Eucheuma sp., 68 spinosum, 83, 85 European Economic Community (EEC), designation for algin compounds, 118 gum arabic and, 13, 15 Evaporated milk, use of carrageenan in, 99

F Facial masque, alginate gel and, 163-164 FAO, II Farming technology, for seaweed, 64 Fat containing confections, use of gum arabic in,23 FOE, see Federal Drug Administration Federal Drug Administration (FDA) agar and, 76 furcellaran and carrageenan and, 86 gum arabic and, 13, 15 gum tragacanth and, 51 review of food additives, 20 Feeding tests, on furacellaran and carrageenan, 86 Fiber(s) alginate, 172-173 spun, properties, 173 Filaments, alginate, I 72-173 Film forming propenies, I 16 of alginates, 174 of gum karaya, 44 Films, 161, 174, 176 Fish products, see also Applications, Table of use of agar in, 82-83 use of carrageenans and furcellaran in, 104-105 "Fixed" flavor, use of gum arabic for, 21, 22 Aake(s) agar, 75 of gum tragacanth, 50, 52, 56 Flan, alginate gel for, 168 Flavor fixation gum arabic for, 21-22 gum ghatti for, 36 Flour, 167 Foam stabilization propenies, of gum karaya, 45 Food additives, FDA review, 20 Food and Agriculture Organization/World Health Organization (FAO/WHO), alginates and, 118 Food applications, see also Applications, Table of gum arabic, 2~26 gum karaya, 45-46 gum tragacanth, 57-59 Food Chemical Code (FCC), 117 gum karaya and, 40 Food coloring, use of gum arabic in, 26 Food industry use of alginates in, l lC--117 Food systems, use of alginates in, 154-183 French dressing, use of propylene glycol alginate for, 177 Frozen beverages, use of carrageenan in, 106 Frozen dessens, use of gum karaya in, 45

Fruit frozen, use of gum tragacanth in, 59 use of agar in, 83 use of carrageenans in, 101, 107 dessens, 103 imitation fruit, 107, 183 Fruit beverages use of carrageenan in, 105--106 use of gum arabic in, 24 Fruit gums, use of gum arabic in, 23 Fruit juice drinks, use of propylene glycol alginate in, 17C--178 Fruit puree, simulated, alginate polymers and, 171 L-Fucopyranose, in gum tragacanth acid, 53, 54 L-Fucose, in tragacanthic acid, 51 Fungi, gum formation and, 4 Furcellaran, 64 applications, 94, 10, 103, 105, 107 background, 84 production, 86, 88 propenies, ~94 regulatory status, 86 strucutre, 89--90 chemical 69, 70 Furcellariafastigiata, 64, 84, 86

G Galactopyranose units, in gum arabic, 17 o-Galactopyranose in arabinogalactin, 54 in gum tragacanth, 52 13-D-Galactopyranose units, in gum ghatti, 33 a-o-Galactopyranosyl, in carrageenan, 88 !3-0-Galactopyranosyl, in carrageenan, 88 o-Galactopyranosyl-3,6-anhydro-L-galactopyranose, 78, 79 D-Galacto-pyrano-uronic acid groups, of tragacanthic acid, 53 Galactose, 86 ammonium sulfate esters of, 84 in gum arabic, 15, 17 polymers of, 69 o-Galactose in furcellaran, 89, 90 in gum ghatti, 33 in gum karaya, 41, 42 polysaccharides of, 83 in seaweed, 69 in tragacanthic acid, 5 I L-Galactose, in seaweed, 70 o-Galactose residues, in gum tragacanth, 52 o-Galactose-4-sulfate, 84 in iora-carrageenan, 89 Galactose-6-sulfate, in /ambda-carrageenan, 89 13-Galactose units, in gum arabic, IC--17 o-Galacturonic acid in gum karaya, 41, 42 in tragacanthic acid, 51, 52 Galacturonorhamnan chains, in gum karaya, 42

195 Gel(s) , see also Applications , Table of acid , 135 , 136. 164-169 alginate, 138-139 agar. 75 alginate, see Alginate gels calcium/alginate, I35 dessert, use of carrageenans in , 101-102 dietetic , use of carrageenan and furcellaran in.

103

milk, use of carrageenan and furcellaran in,

100---101

Gelation of agar, 79-80 characteristics of alginates, 116, 136. 138 of carrageenan and furcellaran, 90, 91 prevention of, 25, 26 Gel fraction. of gum ghatti. 33

Gelidium amansii, 78 cartiliaineum, 75 sp., 74, 78

Gelling mechanism. of agar. 80 Gharri , 5 " Ghats", 32

Gigartina acicularis, 85 canaliculata, 89 chamissoi, 89 pasrillata, 85 radulla, 85 Sp., 89 stellata. 85 Gigartinaceae. 85 Glucuronic acid, 78 in gum arabic, 15, 17

D-Glucuronic acid , in gum ghatti, 33 Glycerol , 57, 70 Good Manufacturing Practice (GMP) levels, on furcellaran and carrageenan, 86

Graci/aria confervoides, 75 sp.. 74, 78 GRAS agar and, 76

carrageenan and furcellaran and , 86 gum arabic and . 13 gum ghatti and, 32 gum karaya and, 40, 46 Guar gum applications, 45, 97 commercial developments, 66 Guluronic acid, see also Mannuronic/guluronic ratio, 64 L-Guluronic acid in alginates, 117, 125, 126 in alginic acid, I 16 Gum(s), see also gums by name , 4-5 Gum acacia , see Gum arabic Gum arabic (gum acacia) , 4 , 33

background, 8 business developments, 66 compatibility, to gum tragacanth. 56 food applications , 20-21 , 25-26 baking products, 24 beverages, 23-24 confectionary 22-23 dietetic foods, 25 navor fixation, 21-22 protective coating, 24-25 manufacture availability, I 3 collection, 9-14 source, 8-9 properties compatibility, 19, 20 effect of electrolytes, 19 effect of pH. 19, 21 emulsifying, 19 solubility. 17 viscosity, 17-19 regulatory status. 13, 15 replacement of, 22, 36 specifications, I 3 structure, 15-17 Gum drops , use of gum arabic in , 23 Gum exudate(s), 5 business developments, 66 Gum ghatti (Indian gum) background, 32 business developments, 66 properties, 36 effect of cations on , 35, 36 effect of pH , 34, 35 viscosity. 33-35 regulatory status, 32, 33 specifications, 32 structure, 32, 33 Gum karaya (sterculia gum). 32 applications, 44-46 background, 40 business developments, 66 manufacture, 41, 41 properties , 42-44 regulatory status , 40, 41 specifications, 40 structure , 41--42 Gum tragacanth , 4, 5 applications, 83 food , 57-59 background, 50 business developments, 66 properties acid stability, 53-55 compatibility, 56-57 preservation, 57 rheology, 53, 54 surface activity , 54-56 viscosity , 52-53 regulatory status. 51 structure, 51-52

196

Food Hydrocolloids

H "Hand-picked selected, " 9 Harvesting, of carrageenan and furcellaran , 86-87 Health food products, use of agar in, 83 Heat, for sequestration, 147 Hemostatic action, of alginates, 175 Heptyl-p-hydroxybenzoate, 179 High-temperature, short-time (HTST) techniques, 98 Hydration of alginates, 131, 132, 153, 181-182 of gum karaya, 42, 43 of tragacanth. 52-53 Hydrocolloids, see also Gum blends of alginates with , 153 business developments , 69 use, in bakery products, 8 I Hydrogen bonding, 142 Hydrogen ions, alginate hydration and , 131 Hydrolysis of gum karaya , 42 of tragacanthic aicd, 51 Hysteresis. 80

I Ice cream application of carrageenans to, 95--97 stabilization, use of gum tragacanth in, 57 Icings, use of agar in, 8~1 Indian gum, see Gum ghatti; Gum karaya Indian tragacanth, sec Gum karaya Infrared absorption spectra, of carrageenans, 85 Insulin producing cells (islets), encapsulation. 162 IRDA, 11 Irish moss (Chondrus crispus) , 64, 66, 83 , 85 carrageenans from . 98 production, 67

J Japanese desserts and confections, use of agar in, 82 Japanese gelatin, see Agar Japanese isinglass, see Agar Jelly(ies) , 183 dietetic, use of carrageen and furcellaran in, 103 imitation, bakery, 165 use of agar in, 75 Jelly candies, use of gum arabic in, 23

K Kadayo gum, see Gum karaya Kanten , see Agar Karaya , 5, 33 Katilo gum, see Gum karaya

Kelp , 64 Khaya, grandifoliola, 42 sp., 42 Kullo , see Gum karaya Kuteera, see Gum karaya

L Laminaria alginic acid from, 126 digitata, 119, 123 hyperborea, l 19 , 125 production, 123 Lecithin, 36 Leguminosae, see Astra/agus plants Lipophilic characteristics, of propylene glycol alginate, 178 Liqueur mousse, alginate gel and, 164 Liquid dispersion methods. alginate solubility and, 129, 130 Locust bean gum , 97 applications, 100, 103 business developments , 66 Lozenges, use of gum arabic in, 23 Lubricating jellies, use of algin in, 174

M Macrocystis pyrefera, 64 alginic acid from , 126 production, 119-122 Magnesium, 84 in alginates, 123 Magnesium ions, in gum karaya, 41 Magnesium salt in alginates, I 16, 129 in gum arabic , 15 in gum ghatti, 32 in karaya gum, 42 a-o-Mannopyranose, in gum ghatti, 33 o-Mannose, in gum ghani, 33 Mannuronic acid , 64 o-Mannuronic acid, in alginates, 117 in alginic acid, I 16, 125 , 126 Mannuronic/guluronic (MIG) ratio, in alginates, 152-153 Manufacture, of carrageenan and furcellaran , 8687 Mariculture, for seaweed production, 68 Meat, use of agarin in, 82-83 Meat analogs, use of carrageenan in, 105 Meat products use of carrageenan and furcellaran in , I00-105 use of gum karaya in, 46 Medical applications, see also Applications, table of alginate gels, 167 gum karaya, 44--45

197 Metal cations, polyvalent, interaction of alginates with, 141-154 Metal ions, reaction of alginates to, I 54 Methylation, of sugar residues, 70 4-O-Methylglucuronic acid, in gum arabic, 15, 17 Methylparaben, 132

Milk

preservation, 59 solubility of furcellaran and carrageenan in, 90 Milk-based products, 183 alginates in, 156 carrageenans in, 94--104 Milk beverages, use of carrageenans in, 97-99 in imitation beverages, 103 Milk solids, solubility cf alginates in, 131-132 Mirsumame, 82 Moisture curves, for alginates, 127, 128 Monoglycerides, 85 Morphine sulfate, release, sodium alginate and, 176 Mous.se, liqueur. alginate gel and, 164 Mucara gum, see Gum karaya

N National Forrnulary (NF), description of alginates, 117 Newtonian character in alginates, 132, 133 non-Newtonian behavior, of gum ghatti, 33, 34 Noodle products, use of agar in, 83

0 Oblate, 82 Orange drink. whipped, use of propylene glycol alginate in, 180

p Pasteurized milk, use of carrageenans in, 98 Pectin, low methoxyl, application, 103 Pet foods, use of carrageenan in, 105 pH of alginates, 1I 7 effects on agar gelation, 80 in alginates, 133, 134, 138, 158 on calcium/alginate interaction, 170 on carrageenans, 92 on gum arabic viscosity, 19 in gum ghatti viscosity, 34, 35 on gum karaya viscosity, 43, 44 on gum tragacanth, 54, 55f Phaeophyceae, see also Brown seaweed, I 16--118 Pharmaceutical applications, of gum karaya, 44-45 Phosphate(s), use with alginates, 153--154 Phosphate salts, applications, 100 _ Physical properties, of gums, 4--5

Pie filling, use of alginates in, 139-140 Piping jellies, use in algin in, 174 Pizza sauce, calciurn/algin interaction and, I54-156 pKa values, for alginic acid, 133, 134 Plants, gum exudates from, 4 Plasma-alginate mixtures, 173 Polyguluronan, in alginic acid, 126, 127 Polyguluronic acid segments (poly G blocks), calcium ions and, 141 Polymannuronan, in alginic acid, 126, 127 Polymannuronic acid segments, (poly M blocks), calcium ions and, 141 Polymer(s), insoluble, calciurn/algin interaction and, 168-173 Polysaccharide components, of tragacanth, 51 Polysaccharidic acid, 32 in gum arabic, 15 Polysorbate, 80, 85 Potash, 167 Potassium, 84, 86, I 16 Potassium alginate, I 16, 117 gel formation and, 157 Potassium cations, in tragacanthic acid, 51 Potassium furcellaran, 88 Potassium salt in alginates, 123 in gum arabic, 15 Potassium sorbate, 132 Poultry products, use of agar in, 82-83 Powder, agar, 75 Preservation, of gum tragacanth, 57 Preservatives, use with hydrocolloids, 132 Product development, alginates in, 180-182 Propylene glycol alginate, 57, 116, 117 applications, 176--180, 183 production, 123 properties, 127, 128 solubility in water, 129 viscosity, 137, 140 reaction with calcium ions, 142, 144 regulations, 118 Propylene glycol esters (PGAs), of of alginic acid, 153 Propylparaben, 132 Protective coatings, use of gum arabic in, 24-25 Protein(s) in gum arabic, 16 interaction with hydrocolloids, 175 reaction with propylene glycol alginates, 180 Protein concentrates, non-denatured, production, 175 Protein fibers fabricated, use of carrageenan in, I05 spinning process, 172-173 Protein reactivity, of carrageens, 92-94 Puddings, use of carrageenan and furcellaran in in milk puddings, 99-100 in non-dairy puddings, 103--104 Purification, of gum karaya, 41 Pyruvic acid, 70

198

Food Hydrocolloids

in agar, 48

Q Quaternary ammonium salt procedure, 78

R Red seaweed (Rhodophyceae), 64, 75, 84 botanical classification, 65 chemical structure, 69 cultivation, 64 sulfate content, 70 Red seaweed extracts agar, see Agar carrageenan, see Carrageenan chemical structure, 69. 70 furcellaran, see Furcellaran Regulatory status, see under Specific gum Relishes, use of carrageenan in, 106 Rhamnose, in gum arabic, 15, 17 L-Rhamnose in karaya gum, 4 I, 42 in tragacanthic acid, 5 I, 52 Rheology of alginates, 132, 133 of tragacanth, 53, 54 Rhodophyceae. see Red seaweed Ribbon(s), of gum tragacanth, 50, 52. 56

RNUD, II

s Saccharomyces cerevisiae cells, encapsulation, 162 Salad dressings, 153 carrageenan and, 106 gum karaya and, 45 gum tragacanth and, 57 propylene glycol and, 17~177, 180 Salt effect on alginate, 141 solubility of alginate in, 131-132 Sauce(s), 154, 155 use of carrageenan in, 106 use of gum tragacanth in, 57 Seasoning agents, use of gum arabic in, 25 Seaweed, see also Brown seaweed, Red seaweed background, 64, 65, 67 business developments, 66, 69 chemical structure common basic composition, 69-70 sulfate content, 70 collection of, 7~77 cultivation, 64, 6~8 Seaweed extract(s) brown, see Alginate extraction, 75 red, see Red seaweed extracts

Sequestrants alginate gels and , 162, 163 binding efficiency of, 147 use with alginates, 146, 147, 153 Shapes. gels for, 162 Single-line gum type business, 66, 69 Size reduction, of gum karaya, 41 Sodium, 84 gel formation and, 157 Sodium alginate, 81 , 116, 117, 152, 158 applications, 174, 176 food, 139-140, 167 description, 117 production, 123 properties, 127 viscosity, 136, 138 regulations, 118 Sodium benzoate, 132 Sodium carbonate, use with alginates, 147 Sodium carboxymethylcellulose, 97 Sodium carrageenate, application, 105 Sodium cations, in furcellaran, 86 Sodium citrate, use with alginates, 147 Sodium hexametaphosphate, 172 use with alginates, 146 Sodium salts, gum ghatti viscosity and, 35 Sodium tripolyphosphate (STPP, STP). use with alginates, 147 Solieriaceae, 85 Solubility of cal-rageenan and furcellaran, 90 of gum arabic, 17 Solution properties, of alginates, 128--132 Sorbate, 17 I Sorbic acid, 132 Soy protein concentrates, manufacture, 175 Sphaerococcaceae, 75 Spray-dried flavor , use of gum arabic for, 21-23 Spun fibers, properties, 173 Stabilizer agar as, 83 gum ghatti, as, 36 Stabilizing properties, 116 of gum karaya, 45, 46 Sterculia gum, see Gum karaya Srerculia urens tree, 40, 41 Sterilized milks, use of carrageenans in, 98--99 Strawberry topping, use of propylene glycol alginate in, 178 Strips, agar, 75 Sugars, see also sugars by name crystallization, prevention, 22 effects on carrageenan, 90 Sugar residues, sulfation and methylation of, 70 Sulfate content, in seaweed, 70 Sulfated polysaccharides, protein reactivity of, 92 Sulfation, of sugar residues, 70 Surface activity, of gum tragacanth, 54-56 Suspending properties, I 16 Syneresis, 80 of gels, 158

199 Synergistic reactions, of gum tragacanth , 57 Syrup, 156 buttered. use of propylene glycol alginate in, 179 use of algin in, I 74, 178

T Tank aquaculture, of seaweed, 64 Tannins, gum color and, 5 Temperature. effects on alginate, 140 on alginate gels, 168 Tetrasodium pyrophosphate (TSSP), 157. 163 use with alginates, 146 Thickening propenies, 116 Tomato, carrageenan stability and , 106 Tragacanthic acid, structure. 51-52 Trees, gum exudates from, 4 Trisodium phosphate (TSP), 158 use with alginates, 146 Tungfen, see Agar

u UNEF, II Uronic acid, 70 in gum arabic, 15 Uronic acid residues, in gum karaya, 41 U.S. Department of Agriculture, algin and, 118 U.S. Pharmacopeia XX, gum arabic standards. I 3

V Vanilla flan, alginate gel for , 168 Vegetarian products, use of agar in, 83 Venturi 's effect, 129 Viscosity of agar, 80 of alginates, 132-149, 153 of gum arabic, 17,19

of gum ghatti, 33 .34 of gum karaya, 42-43 of gum tragacanth. 52-53 Viscosity building. use of algin for. 173--174 Vitamin(s), use of gum arabic in, 24--25 Vitamin C, stabilization, 59

w Water absorption, by alginates , 176 solubility in of alginates, 129-131 of furcellaran and carrageenan, 90 Water-soluble plant gums, 5 Water systems, application of carrageenan in, 95, 96, IOI Whey. sequestration, 97 Whipped cream products, use of carrageenans in. 101

Whipped toppings , non-diary , use of carrageenan in, 104 Wounds, treatment of, use of alginates for, 175

X Xanthan gum, 57, 139 applications, 97, 177 manufacture, 66 o-Xylopyranose, in tragacanthic acid, 53 Xylose, 70 o-Xylose in gum ghatti, 33 in tragacanthic acid, 5 I

y Yogun. use of carrageenans and furcellaran in, 1~101

Food Hydrocolloids Volume III Editor

Martin Glicksman General Foods Corporation Tarrytown, New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 Reissued 2019 by CRC Press © 1986 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www. copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organiza-tion that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged.

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Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com DOI: 10.1201/9780429290459

PREFACE Volume III of this series of books on food gums and hydrocolloids continues with a pragmatic coverage of three important categories of gums, i.e., the cellulose gums, the plant seed gums, and the pectins. The chemical, physical, and functional properties of each of the important food gums in these categories are reviewed and discussed in relation with their utility in food product applications. I would like to thank each of the contributing authors for their participation and assistance in this undertaking, and I also wish to express my gratitude to my many friends and associates in the food industry and at General Foods Corporation for their helpful advice, counsel, and encouragement. I specially want to thank Ms. Elly Cohen for her assistance with literature references and helpful library assistance and my grateful thanks to Mrs. Lillian Varian and Ms. Pat Lyon for typing and correcting the sections of the manuscript that I wrote. Martin Glicksman Valley Cottage, N.Y. May 15, 1984

THE EDITOR Martin Glicksman is a Principal Scientist in the Central Research Department of General Foods Corporation, Tarrytown, New York. For the past 30 years he has been actively involved in applied research and in the development of many new food products. Before joining General Foods he worked for seven years in the pharamaceutical and fine chemical industry as an organic chemist. Mr. Glicksman has acquired an international reputation in the field of hydrocolloid technology, has published many papers, and holds 22 patents in the field. His best-known publication is the book Gum Technology in the Food Industry, which is a basic reference book on hydrocolloids in the food processing industry. Mr. Glicksman holds a B.S. degree from City College of New York and M.S. and M.A. degrees from New York University. He is a Fellow of the Institute of Food Technologists and is currently a Counselor of the New York Section of the I.F. T. which has a membership of about 1100 food industry members. He is also on the Executive Board of the Carbohydrate Division of the national I.F.T. and serves on the editorial boards of the Journal of Food Science and Carbohydrate Polymers.

DEDICATION To the memory of my friend, Dr. (formerly Private) Martin Gold, Comrade-in-arms at Fort Benning, Georgia, and the 86th (Black Hawk) Infantry Division

CONTRIBUTORS Steen Hffjgaard Christensen, M.Sc. Manager, Application Research Research and Development A/S K0benhavns Pektinfabrik Lille Skensved, Denmark Martin Glicksman, M.S., M.A. Principal Scientist Central Research Department General Foods Corp. Tarrytown, New York Joseph A. Grover, Ph.D. Research Associate Michigan Applied Science and Technology Laboratories The Dow Chemical Co. Midland, Michigan Carl T. Herald, Ph.D. Product Sales Manager Celanese Water Soluble Polymers Louisville, Kentucky

*

Now with Nestle S. A., New Milford, Connecticut.

John D. Keller, M.S.* Manager, Research and Development Food Hydrocolloid Group Hercules, Inc. Middletown, New York

Christopher McIntyre, L.R.S.C., A.I.F.S.T. Director, Technical Services PFW Division Hercules, Inc. Food Technology Center Middletown, New York

William R. Thomas Product Marketing Manager Marine Colloids Division FMC Corp. Philadelphia, Pennsy Jvania

FOOD HYDROCOLLOIDS Volume I Section I: Comparative Properties of Hydrocolloids Background and Classification Structure and Conformation of Hydrocolloids Functional Properties Gums and Nutrition Section II: Fermentation (Biosynthetic) Gums Introduction Xanthan Curdlan Dextran Potentially Important Fermentation Gums Volume II Section I: Natural Food Exudates Introduction Gum Arabic (Gum Acacia) Gum Ghatti Gum Karaya (Sterculia Gum) Gum Tragacanth Section II: Seaweed Extracts Introduction Red Seaweed Extracts (Agar, Carrageenan, Furcellaran) Brown Seaweed Extracts (Alginates) Volume III Section I: Cellulose Gums Introduction Microcrystalline Cellulose (MCC or Cellulose Gel) Sodium Carboxymethylcellulose (CMC) Hydroxypropylcellulose (HPC) Methylcellulose (MC) and Hydroxypropylmethylcellulose (HPMC) Section II: Plant Seed Gums Introduction Locust/Carob Bean Gum Guar Gum Tara Gum Tamarind Seed Gum Section III: Plant Extracts Pectins

TABLE OF CONTENTS I. CELLULOSE GUMS Introduction ........... . .............................. . . . ................................. 3 Martin Glicksman Chapter I Microcrystalline Cellulose (MCC or Cellulose Gel) ...................................... 9 William R. Thomas Chapter 2 Sodium Carboxymethylcellulose (CMC) ................................................. 43 John D. Keller Chapter 3 Hydroxypropylcellulose (HPC) ................................................ . ........ 111 Christopher McIntyre Chapter 4 Methylcellulose (MC) and Hydroxypropylmethylcellulose (HPMC) .................... 121 Joseph A. Grover II. PLANT SEED GUMS Introduction ............................................................................ 157 Martin Glicksman Chapter 5 Locust/Carob Bean Gum ............................................................... 161 Carl T. Herald Chapter 6 Guar Gum .............................................................................. 171 Carl T. Herald Chapter 7 Tara Gum .............................................................................. 185 Martin Glicksman Chapter 8 Tamarind Seed Gum ........................ . .............. . ........................... 191 Martin Glicksman III. PLANT EXTRACTS Chapter 9 Pectins ................................................................................. 205 Steen Ht,jgaard Christensen INDEX ............................. . ................................................... 233

Cellulose Gums

DOI: 10.1201/9780429290459-1

@ Taylor & Francis a

1

Taylor & Francis Group http://taylorandfrancis.com

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INTRODUCTION Martin Glicksman TABLE OF CONTENTS I.

Background ...... . ................................................................ 4

II.

Structure ................................................ . ......................... 4

III.

Preparation ........................................................................ 5

IV.

Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

References ................................................................................ 8

DOI: 10.1201/9780429290459-2

4

Food Hydrocolloids

I. BACKGROUND Cellulose - the backbone of the vegetable world - is the most plentiful renewable resource in the world. It has been estimated that between !0 10 and !0 11 tons are synthesized and destroyed each year. 8 Cellulose thus is an extremely good economic starting material for the development of new functional polymers. Cellulose is the major constituent of all vegetation, comprising from one third to one half of dry-plant material. Cellulose, together with hemicelluloses and lignins, are the major structural constituents of most land plants and form the cell walls and intercellular layers of the basic supporting structure of the plant. About 40 to 50% of all woody materials and up to 98% of cotton !inters are made up of cellulose. Other agricultural residues such as com stalks, com cobs, and wheat straw contain smaller amounts of cellulose (about 30%), but are all available as a giant reservoir of potentially available cellulosic raw material. 1. 2

II. STRUCTURE Cellulose is a linear polymer of o-glucose monomers joined by 13-D-( 1-4) - linkages and arranged in repeating units of cellobiose, each composed of two anhydroglucose units. It has a high molecular chain length, and the hydrogen-bonding capacity of the three hydroxyl groups is very great. Because of the uniform nature and linear structure of the molecules, they can fit together over at least part of their length to form crystalline regions of great strength and rigidity. These crystalline regions give plant cell walls their great strength and rigidity as exemplified by the high tensile strengths of all vegetable fibers.1. 2 •7 • 10 In nature, cellulose occurs in the presence of other polysaccharides such as xylan and mannan, which are often known as "hemicelluloses". Cellulose is purified by removal of these materials, as well as proteins and lipids, etc. by boiling in dilute alkali. The degree of polymerization (DP) of cellulose ranges from 3900 to I 8,000, 8 and each o-glucose component is in the pyranose form in the Cl(D) chair conformation, the complete polymer being arranged spatially into long thread-like molecules, as confirmed by X-ray measurements of native cellulose. The cellulose molecules are aligned to form fibers, some regions of which are highly ordered and have a crystalline structure due to lateral association by hydrogen bonding. The crystalline regions vary in size and represent areas of great mechanical strength and high resistance to attack by chemical reagents and hydrolytic enzymes. The physical and chemical properties of cellulose are greatly dependent on the relative amount and arrangement of the crystalline regions. The cellulose molecules tend to remain extended but may normally undergo a degree of turning and twisting. Because of its size and strong associative forces, it can only be brought into solution under certain conditions, usually by chemically modifying the polymer to add side chains that will separate the polymers and allow hydration and solubilization in aqueous media to take place. In this way, many diverse and useful functional properties can be imparted to the cellulose molecule. 1•2 ·7 -9 • 1° The cellulose derivatives most useful in the food industry are ethers in which alkyl or hydroxyalkyl groups have been substituted upon one or more of the three available hydroxyl groups in each anhydroglucose unit of the cellulose chain. The effect of the substituent groups is to disorder and spread apart the cellulose chains so that water or other solvents may enter to solvate the chain. By controlling the type and degree of substitution, it is possible to produce products that have a wide range of functional properties. The more important water-soluble derivatives are those with the following substituent groups:

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Sodium carboxymethyl

Na00C-CH 2 -

Methyl HO-CH2-CH 2-CH2or CH 3 -HOCH-CH 2 -

Hydroxypropyl

CH 3 -HOCH-CH 2 - and CH 3 -

Methylhydroxypropyl

When all three available hydroxyl positions on the cellulose molecule are replaced by a substituent group, the derivative is said to have a degree of substitution (DS) of three. Actually, this is rarely the case, since partial substitutions are preferred, but it can readily be seen that varying the degree of substitution as well as the type of chemical substituent makes possible a tremendous range of permutations and combinations offering a wide selection of functional properties. However, only a comparatively limited number of these derivatives have been found to have industrial or food applications.1._;.io

III. PREPARATION All o-glucose units in the cellulose polymer chain have hydroxyl groups available at carbons C-2, C-3, and C-6 which can be substituted by etherification or esterification (Figure 1). When all the hydroxyl groups are substituted, the cellulose is said to have its maximum degree of substitution of 3.0 (DS of 3.0). Most commercial water-soluble cellulose derivatives have substantially less substitution, usually in the area of DS 1.0. When side chain formation is possible, the substituent groups are defined in molar terms and the molar substitution (MS) value can exceed 3.0. The properties of a specific cellulose ether depend on the type, distribution, and uniformity of the substituent groups. The water-soluble cellulose ethers possess a range of multifunctional properties resulting in a broad spectrum of end uses and applications. The preparation of water-soluble derivatives, mostly ethers, essentially begins with the same initial step - treatment of the cellulose with aqueous sodium hydroxide to swell and distend the fibers. This is followed by reaction with the appropriate reagents to form the desired compounds. The water-soluble cellulose ethers important to the food industry are prepared in the following ways: I.

Carboxymethylcellulose (CMC) 5 · 12 - CMC is produced by treating cellulose with aqueous sodium hydroxide followed by reaction with sodium chloroacetate: R-OH + NaOH + ClCH 2COONa ➔ R-OCH 2 COON a + NaCl + H2 0 A side reaction, the formation of sodium glycolate, also occurs: ClCH 2 COONa + NaOH

2.

➔

HOCH 2 COONa + NaCl

Methylcellulose and Hydroxypropylmethylcellulose4 · 11 - Methylcellulose is prepared by reacting purified wood pulp or cotton !inters having a high a-cellulose content with aqueous sodium hydroxide, and then with methyl chloride according to the following reactions where R is the cellulose radical:

6

Food Hydrocolloids

•Main reactions: R-OH + NaOH R-OH • NaOH R-ONa + CH 3 Cl

➔

~ ➔

R-OH • NaOH (complex) R-ONa +.H 2 0 R-OCH 3 + NaCl

•Side reactions: CH 3 Cl + NaOH CH 3 Cl + H2 0 CH 3 0H + NaOH CH 3 ONa + CH 3 Cl

➔ ➔ ~ ➔

CH 3 0H + NaCl CH 3 0H + HCl CH 3 0Na + H2 0 CH 3 OCH 3 + NaCl

For the production of hydroxypropylmethylcellulose, propylene oxide is also added to the mixture and reacts as follows: •Main reaction:

/0"

NaOH

R-OH + CH 2 --CH --➔ I CH3

OH I R-O-CH 2 -CH-CH 3

•Side reaction:

glycols + glycol ethers The relative amounts of methyl and hydroxypropyl substitution are controlled by the weight ratio and concentration of sodium hydroxide and the weight ratios of methyl chloride and propylene oxide per unit weight of cellulose.

3.

Hydroxypropylcellulose6 · 13 - Cellulose derived from wood pulp or cotton !inters is treated with aqueous sodium hydroxide, and the resulting alkali cellulose is reacted with propylene oxide: 0

/\

R-OH + CH 3 CHCH2

➔

R-OCH 2 CHOHCH 3

The secondary hydroxyl group in the hydroxypropyl group is capable of hydroxypropylation to give a side chain:

➔

CH 2 CHOHCH 3 I 0 I R-CHCHCH 3

The sodium hydroxide functions as a swelling agent and a catalyst for the etherification. A side reaction in which propylene oxide reacts with water to form a mixture of

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H

HO

OH

FIGURE I.

Structure of cellulose and derivatives.

propylene glycols also occurs, but can be minimized by keeping the water input as low as possible.

IV. PROPERTIES Of the many cellulose polymers and derivatives investigated and manufactured, these four water-soluble polymers have found utility in the food industry. In addition, pure cellulose in specially prepared, physically modified form 9 has been shown to have useful functional hydrocolloidal properties and has found significant use in certain food applications. These five materials will be discussed in the four chapters of this section of the book. Sodium carboxymethylcellulose (cellulose gum or CMC) is the most important cellulosederived hydrocolloid used in the food industry. It is an anionic polymer, and in addition to its ability to thicken and modify rheology of water solutions, it has the unique property of being able to react with proteins and other charged molecules within specific pH ranges. These functional properties have led to its extensive use in the food industry in many diverse product applications. 3 ·5 · 12 Methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) are polymers having the useful properties of thickening, surfactancy, film forming ability, adhesiveness, and the unique property of thermal gelation. They have the unusual property of solubility in cold water and insolubility in hot water, so that when a solution is heated, a three-dimensional gel structure forms, which is reversible when the solution cools. These properties have led to widespread industrial applications and limited, specialized applications in the food industry. 4 • 11 Hydroxypropylcellulose (HPC), sold under the trade name of Klucel® ,6 is a nonionic cellulose ether with an unusual combination of properties. These include solubility in both water (below 40°C) and polar organic solvents, high surface activity, and thermoplasticity plastic flow (extrudability under pressure) properties; and the insensitivity of viscosity to changes in pH. 6 · 13 Microcrystalline cellulose (MCC), sold under the trade name of Avicel®, is really a family of materials having hydrocolloidal functional properties which has resulted in their use as hydrocolloid ingredients in food applications. The basic microcrystalline cellulose is an acid-hydrolyzed, pure ex-cellulose material that has effective thickening and water-absorptive properties when dispersed under high shear conditions. To improve hydration rate and capacity, several of the microcrystalline cellulose materials have to be dried with other materials such as CMC. This has improved their functionality and extended their utility in food products application, especially in the area of dairy and frozen food products. 1. 9

8

Food Hydrocolloids

REFERENCES I. Glicksman, M., Gum Technology in the Food Industry, Academic Press, New York, 1969. 2. Whistler, R. L., Industrial Gums. 2nd ed., Academic Press, New York, 1973. 3. Ganz, A. J., Cellulose hydrocolloids, in Food Colloids, Graham, H., Ed., AV! Press, Westport, Conn., 1977, 382--417. 4. Dow Chemical Co., Handbook on Methocel® Cellulose Ether Products, Dow Chemical Co., Midland, Mich., 1981. 5. Hercules, Inc., Cellulose Gum - Chemical and Physical Properties, Hercules, Inc., Wilmington, Del., 1978. 6. Hercules, Inc., Klucel® Hydroxypropyl Cellulose - Chemical and Physical Properties, Hercules, Inc., Wilmington, Del., 1976. 7. Ward, K., Jr. and Seib, P. A., Cellulose, lichenan and chitin, in The Carbohydrates - Chemistry and Biochemistry, Vol. 2A, 2nd ed., Pigman, W., Horton, D., and Herp, A., Eds., Academic Press, New York, 1970, 413--445. 8. Walton, A. G. and Blackwell, J., Biopolymers. Academic Press, N.Y., 1973, 464--474. 9. Battista, 0. A., Microcrystal Polymer Science, McGraw-Hill, New York, 1975. 10. Whistler, R. L. and Zysk, J. R., Carbohydrates, in Encyclopedia of Chemical Technology, Vol 4, 3rd ed., Grayson, M. and Eckroth, D., Eds., John Wiley & Sons, New York, 1978, 535-555. 11. Greminger, G. K., Jr. and Krumel, K., Alkyl and hydroxyalkylalkylcellulose, in Handbook of WaterSoluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill, New York, 1980, chap. 3. 12. Stelzer, G. I. and Klug, E. D., Carboxymethylcellulose, Handbook of Water-Soluble Gums and Resins, Davidson, R. L., Ed., McGraw-Hill. New York, 1980. chap. 4. 13. Butler, R. W. and Klug, E. D., Hydroxypropylcellulose, in Handbook ofWater-Soluble Gums and Resins, Davidson, R. L., Ed., McGraw, Hill, New York, 1980, chap. 13.

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Chapter I

MICROCRYSTALLINE CELLULOSE (MCC OR CELLULOSE GEL) William R. Thomas

TABLE OF CONTENTS I.

Introduction ........ . .......................... . .............. . . . ............ . .... I0

II.

Production ........................................... . ........................... IO A. Powdered Microcrystalline Cellulose ..... . .......................... . . ... 11 B. Colloidal Microcrystalline Cellulose ...................................... 11

III.

Technical Properties ......................................... . ............. . . .... 13 A. Powdered Microcrystalline Cellulose Types .............................. 13 B. Colloidal Microcrystalline Cellulose ...................................... I4 I. Flocculation by Electrolytes .................................. . .... 16 2. Quality Control ................................................... 18 3. Selection of Colloidal Microcrystalline Cellulose (Cellulose Gel) Types - Comparison of Colloidal MCC with Powdered Type MCC .................................................. .. .... 18 4. Rheological Properties ............................................ 2 I 5. Comparison of Dispersibility of Bulk-Dried Colloidal MCC and Spray-Dried Colloidal MCC in Distilled and City Water .......... 22 6. Recommended Equipment for Dispersing Spray-Dried Microcrystalline Cellulose in Monovalent and Divalent Salt Solutions .......................................................... 23 7. Use of Sequestrants to Improve Dispersibility of Spray-Dried Microcrystalline Cellulose in Water with High Electrolyte Content ........................................................... 24 8. Compatibility with Other Hydrocolloids .......................... 24 9. Compatibility with Miscible Liquids .............................. 25

IV.

Application in Foods ............................................................. 25 A. How Colloidal Microcrystalline Cellulose (Cellulose Gel) Functions ..... 25 B. Functions of Microcrystalline Cellulose in Food .......................... 25 I. Heat Stability ..................................................... 26 2. Starch Extension .................................................. 26 3. Foam Stability .................................................... 28 4. Sugar Gels ........................................................ 28 5. Ice Crystal Control ................................................ 28 6. Thickening with Favorable Mouthfeel ... . ........... . . ........... 29 7. Improved Clingability (Flow Control) ............................. 31 8. Caloric Reduction and Fiber Addition ............................ 31 9. Whitening ......................................................... 33 10. Suspension ......................................................... 33 11 . Emulsion Stabilization ............................................ 33 12. Formed Extruded Foods .......................................... 34

DOI: 10.1201/9780429290459-3

IO

V.

Food Hydrocolloids Federal Regulations Pertaining to the Use of Microcrystalline Cellulose in Foods ............................................................................ 37

References ............................................................................... 40

I. INTRODUCTION Microcrystalline cellulose is one of the few relatively new ingredients available to the food industry. The first commercial quantities were produced in 1962; however, MCC did not become a factor in food stabilization until very late in the 1960s. Although it was first believed that MCC was the ideal ''low calorie'' ingredient for foods, there has been only limited success in that area. By far, the major uses of edible microcrystalline cellulose are for pharmaceutical tableting and the functional (stabilizing) applications for foods. Microcrystalline cellulose results from the concentration of the naturally occurring crystalline portion of the cellulose fiber after acid hydrolysis to the level of DP. It is not a chemical derivative, but a purified native cellulose reduced from a fibrous state to a crystalline powder or a redispersible colloidal gel. The evaluation and application of microcrystalline cellulose (cellulose gel) in food products must take into consideration the science of fine particle technology and be differentiated from the technology associated with starch and soluble gums.

II. PRODUCTION To understand the application of microcrystalline cellulose, it is necessary to understand its source, manufacturing, and how it differs from other hydrocolloids. Cellulose is one of the most abundant and renewable natural resources available to mankind. Cellulose is a polysaccharide polymer composed of glucose units, linked in a linear B14 configuration, which forms the fibrous tissue of plant life. Therefore, it is present in much of the food we eat.

End of Chain with four reactive OH

groups

The cellulose polymer is thread-like and studded with hydroxyl groups. These hydroxyl groups are responsible for very strong lateral forces between adjacent molecules which hold together bundles of chains into these fibrils. The molecules in the fibril bundle are arranged in sufficient regularity to defract X-rays in a characteristic pattern in the same way that inorganic crystals do. Microfibrils are then arranged in layers to form the cell wall of plant fibers. During the manufacture of MCC, the dissolving alpha cellulose pulp is treated with a dilute mineral acid and the cellulose microfibril is unhinged. This hydrolysis process is carried out until a point of leveling off of degree of polymerization is obtained. The paracrystalline regions (Figure I), areas of disordered molecular structure, are weakened as the acid selectivity etches away this area from around the densely arranged crystalline cellulose, similar to removing the mortar from around bricks (Figure 2). Subsequent shear releases the cellulose aggregates, which are the basic raw materials for commercial microcrystalline cellulose products.

Volume lII

11

Cellulose Microfibrils

Crystalline Region { Paracrystalline Region {

FIGURE l.

Cellulose microfibrils.

The manufacturing schematic shown in Figure 3 is helpful in differentiating the major types of cellulose products available in the food industry. Soluble gums, such as CMC, are produced by first treating or opening up the molecular structure of alpha cellulose so that it can be chemically derived. In comparison, microcrystalline cellulose remains insoluble and is not derived during the acid treatment and drying steps. Hence, it remains native cellulose. A second major product from cellulose is fibrous floe which is basically pulverized or wet-milled alpha cellulose. A. Powdered Microcrystalline Cellulose The manufacturing process most common to microcrystalline cellulose produced two divergent products. The first type of product is powdered microcrystalline cellulose (Figure 4). This powdered MCC is a spray-dried MCC aggregate that ranges from 2 to 200 µg and is porous, plastic, and sponge-like. This powdered nonfibrous form of microcrystalline cellulose is used for tableting, dietary applications, as a flavor carrier, and as an anticaking agent for shredded cheese. B. Colloidal Microcrystalline Cellulose The second major type of microcrystalline cellulose is water-dispersible colloidal cellulose that has similar function as soluble gums. Major Functions of MCC Powdered MCC

Colloidal MCC

Binder/disintegrant for tablets Flow aid for cheese Carrier for flavors Fiber

Emulsion stabilizer Thixotropic thickener Moisture control Foam stabilizer Provide cling Ice crystal control Suspending agent

12

Food Hydrocolloids

FIGURE 2.

Microfibril of cellulose releasing microcrystals of cellulose. (Magnification x 50,000.)

In the manufacturing of colloidal types, considerable energy in the form of mechanical attrition is put into the cellulose pulp after hydrolysis, in order to tear the weakened microfibril apart and complete the unhinging process. Current production techniques provide 90% yields of 60 and 70% colloidal crystallite aggregates below 0 .2 µm .

Volume Ill

13

Cellulosic Products

Q

Cellulose

,------,~..----------'-Chemical Chemical Mechanical Oerivatization Disintegration Oepolymerization 1 - - - - . i Wet Mechanical

Disintegration

l

Soluble Cellulose Derivative

Fibrous Cellulose Floe

+Wall!r

HydrocolloKI Solution

Microcrystalline Cellulose

Po-•

l

Colloidal Microcrystalline Cellulose

+Water

Aqueous Colloid

FIGURE 3. ingredients.

Manufacturing process for major types of cellulose food

If the colloidal cellulose were dried at this point, hydrogen bonding would cause homification of cellulose, preventing it from becoming functional as a hydrocolloid stabilizer. For this reason, CMC is used to act as a barrier during drying to prevent this homification. The CMC also is a dispersant to aid in the redispersion of the insoluble microcrystals in aqueous systems. In most colloidal grades of microcrystalline cellulose (cellulose gel), 60 to 70% of these microcrystals will be below 0.2 µg and function as a stabilizer after redispersion in aqueous medium. These submicron particles do not hydrate, but disperse; hence, the use of minute particles to stabilize food systems. Although the microcrystalline cellulose itself forms a thixotropic gel, CMC adds additional stability and can be used to alter the rheology of the system.

III. TECHNICAL PROPERTIES A. Powdered Microcrystalline Cellulose Types The spray-dried agglomerated aggregate of microcrystalline cellulose is sold in various size ranges typified by these FMC Corporation grades: Powdered Microcrystalline Cellulose Types Average particle size (µm) PH-IOI PH-102 PH-105

50 90 18

The different configurations and particle size ranges affect flow properties in tableting, oil and water absorptive capacity, as well as bulk density. Although the MCC is totally carbohydrate, it is not metabolized; therefore, it may be used in low-calorie foods or as a source of food fiber.

14

Food Hydrocolloids

• 100µm■ FIGURE 4.

Avicel® MCC type PH.102.

Typical Properties of MCC Appearance

Heavy metals Water soluble substances Residue on ignition pH (all except for PH~I05) pH (for PH~I05)

White, odorless, tasteless, free-flowing powder

,

~

5000

(.)

1000

>"' 4000 3000 Viscosity measured using a Brookfield Viscometer (Model RVT) with #5 spindle at 20 rpm. Viscosity changes are reversible.

0

20

40 60 Temperature

•c

FIGURE 15.

80

2000 1000 4 2 3 Percent Avicel-RC-501

100

5

Effect of varying temperatures on viscosity.

0

4% modified waxy maize

"'"' 0

-' 75

Viscosity measured using a Brookfield Viscometer, Model RVT, spindle :5 at 10 rpm with helipath on.

100 -----~2----3--4...__5..__~6-----'7 T,me in Days

FIGURE 16. MCC.

• • • •

Effect of prolonged heat on the viscosity of a waxy maize starch and a waxy maize/

Improved flow control Greater resistance to breakdown and shearing Improved heat stability Improved stability in low pH foods

The graph in Figure 16 shows that under prolonged heat, the heat stability of a blend of microcrystalline cellulose and starch is better than that of a 4% modified waxy maize by itself. Admittedly, 77°C for 7 days is very severe - but so are ovens, steam tables, and vending machines. Standardizing the viscosity, body, and texture of fillings such as those used in the baking industry is an excellent use of cellulose gel. Usually these sauces are overheated and then sheared during pumping transfers and reheated to baking temperatures, resulting in a variation

28

Food Hydrocolloids The Effect of Shear 5000

4000

A 4% B 3% and C. 2%

Rate of •Recovery After Shear 5000

Modified Waxy Marze 3:2 Blend Mod,fred Waxy Marze Av,cel RC-591 MCC Avicel RC-591 MCC

Viscosity measured using a Brookl1eld

v,scome1er. Model RVT. spindle ::2 al 10 rpm w,th helipath on Temp 25°C Eppenbach Homo-Mixer at 6000 rpm

4000

C. ,,,,,,.,,,,,

.,;

~

8- 3000

C.

"

?:

3000

.,...

/

·;;; 0

~

/

/

,,,,,,,,,,,,. /

/

/

/

,. /

/

/

/

,. ,.

/'

.,.. ,.

,. /

/'

.,....,.,,,.

/'

/'

/' /'

.,....,...,9_

1000

A. ------------8

10

12

Stirring T,me--Minutes

FIGURE 17.

14

16

6

8

10

12

14

16

Recovery Time-Hours

Effect of shear on viscosity of starch systems.

of viscosity. Cellulose gel (microcrystalline cellulose) can standardize this loss as shown in Figure 17.

3. Foam Stability

Cellulose gel (MCC) is an excellent foam stabilizer, but it does not have film forming properties. When used in a topping, ingredients with film forming properties such as sodium caseinate or hydroxypropyl cellulose are required. A fat reduction of 3 to 4% is usually possible when cellulose gel is used. Insoluble MCC microcrystals are used effectively in frozen desserts to stabilize the foam and improve overrun control (Figure 18). These microcrystals, located primarily in the aqueous phase, improve the extrusion characteristics and at the same time will strengthen the protein film around each air cell (Figure 19).

4. Sugar Gels

The addition of sucrose to aqueous dispersions of colloidal MCC yields higher viscosities than would be expected from the microcrystalline cellulose/water ratios (Figure 20). At concentrations of less than I% of microcrystalline cellulose type RC-591, viscous pourable syrups are obtained; but at cellulose gel concentrations higher than 1%, thixotropic gels are formed. Thus it is possible to impart many unique rheological properties of microcrystalline cellulose to gelled sucrose systems (Figure 21).

5. Ice Crystal Control

The addition of 0.4% microcrystalline cellulose to ice cream mix preserves the original texture of the frozen dessert products during storage and distribution (Figure 22) by increasing their resistance to heat shock and by maintaining these products' three-phase system of air/ fat/water. It also allows for reduction of fat and solids content by 2 to 4% with minimal loss of texture. It is theorized that as the water freezes, it forms large ice crystals which force concentration of the proteins and other solids, causing them to aggregate. But when the ice crystals rethaw, the solids do not fully rehydrate (Figures 23 and 24). Large surface areas of the microcrystalline cellulose allows for absorption of the moisture during the freeze/ thaw cycle, thus preventing moisture migration and controlling aggregation of protein.

Volume Ill

29

MCC Staoillzes aqueous phase

Etlect of .lw,cel AC-S81 on Toi:,o1no Stillness 8 U - Brookfield Un.ts on a AVT Uodel T-Bar He1pa1h on 20 rpm

300

260

220

180

,_

uo

/

24% Fat

100

60

/

0.1% AC-581 (37.78 T.$.)

....

I

I - I-

,\~'-

24% Fat ~(37.68T.S.)

,'-:-'

MCC Strengthens intertace

20 2

4

6

B

10 12

u

16

18 20

FIGURE 19.

Wt11pp1ng Time 1n M,nu1es

MCC in foams.

FIGURE 18. Effect of MCC on the stiffness of a vegetable fat topping.

20.000 Equ,ht)roum w,scos11y meuura-d usUIQ a Btookl,eld v,scomeie,

60'!1.t sucroie

Model RVT. SOUIOle =s

5 rom ,..,,n n,11oa1n on

15.000

A111cel RC,591 MCC

10.000

S.000

AIIICl'I AC-591 MCC ('I'. sohdSI

FIGURE 20.

MCC/sugar syrup.

Like carrageenan, microcrystalline cellulose (cellulose gel) has the ability to prevent whey separation in mixes, thereby countering the destabilizing effects of some soluble gums (Figures 25 and 26). Illustrative of its multifunctional characteristics, the stabilizing effect of microcrystalline cellulose on serum solids is also related to its ability to control ice crystal growth during storage.

6. Thickening with Flavorable Mouthfeel Colloidal MCC dispersions are capable of creating a mouthfeel which is unique. For example, it can be used to shorten the texture of a gum or starch combination or to control

30

Food Hydrocolloids

FIGURE 21.

Photograph of bakery filling.

Volume Ill

31

Avicel RC-581 improves the Heat Shock Resistance of a Frozen, Aerated Dairy Emulsion

,,

A-Control 0.18% CMC-7H B--0.2% Avicel RC-581. 0.16% C-0.4% Avicel AC-581: 0.14% D--0.6% Avicel RC-581: 0.11% E-0.8% Avicel RC-581. 0.09%

I

CMC-7H CMC-7H CMC-7H CMC-7H

D

3.0

C

0

j

5,

!

2.0

Magnitude of Defect

, .o

L

4.0-Near perfect, no criticism 3.5-No definite criticism, but not quite perfect 3.0-Defect slightly detectable 2.5-Definite defect (usually coarse) 2.0-Defect quite pronounced (usually coarse) 2.0-Defect very objectionable

r,me rn Weeks at -

FIGURE 22.

,s·c

MCC improves heat shock resistance.

the flow of the food system without creating or affecting gummy or pasty texture. In many cases, these insoluble microcrystals are used to shorten the texture of xanthan gum solutions or frozen desserts containing large amounts of low DE corn syrup or whey. This is also attributed to the pseudoplastic characteristics of the insoluble microcrystals cellulose gel. Unlike many other vegetable gums, these insoluble microcrystals provide a clean mouthfeel and mask flavor only slightly. Microcrystalline cellulose gels would definitely fall into the "one" rating with starch and polysaccharide gums in Table 6.

7. Improved Clingability (Flow Control) Figure 27 graphically demonstrates how the retention (clingability) of a starch sauce can be improved even at a temperature of 90°C. Note that the viscosity measurements on the samples containing 3% modified waxy maize and 0.5 to 1.5 cellulose gel (MCC) were lower than those of samples containing 5% of the same starch; yet, those containing the cellulose gel (MCC) had better retention. 8. Caloric Reduction and Fiber Addition Cellulose gel (microcrystalline cellulose) is ideal for use in foods, where the caloric density must be controlled. In some foods, microcrystalline cellulose has also been used to increase the crude fiber content. The two basic types of MCC are both used for this application. The spray-dried agglomerates of MCC range in particle size from 90 to 200 µm. These powdered MCC products are used as a direct replacement for high caloric ingredients, such as flour, sugar, and fats in low-moisture food products. In high-moisture food products, the multifunctional water dispersible colloidal MCC grades are applied. Not only do these water dispersible colloidal gels control the aqueous portion of the formulation, but they also suspend solids, stabilized foams and emulsions, modify texture, and control ice crystal growth in frozen desserts.

y,I

N

~ ~

I:)_

~

1 §: ~

FIGURE 23 .

Commercial sample ice milk with MCC.

FIGURE 24.

Ice milk stabilized without MCC.

Volume /Il

FIGURE 25. solids.

33

Ice milk stabilized with Avicel® RC demonstrates the ability of microcrystalline cellulose to stabilize

Because of the removal of primary ingredients like sugar. fat, and starch. these applications are difficult and require proper selection of the cellulose types as well as alterations in the manufacturing procedure and the formulation. 9. Whitening Even in low pH foods, microcrystalline cellulose will not brown on heating. The insoluble particles which are white are often used to opacify food systems. JO . Suspension Dispersions of microcrystalline cellulose at levels of 0.3% will suspend solids such as chocolate in sterilized chocolate drinks, due to the interaction of the microcrystalline cellulose with the milk solids. Where this interaction is not available , levels of 0.5 to 1.5% may be required to suspend large heavy particles. An example might be in the canning operations, where suspensions of solids during cooking and retorting is important. For example, cooked starch granules can be suspended. 11 . Emulsion Stabilization Avicel® serves as an emulsion stabilizer in a way similar to other finely divided solids . Advantage may be taken of its physical properties to impart yield point and prevent coalescence of emulsified materials . Stokes' Law is overcome in emulsions which have a sufficient yield point. It is also theorized that because cellulose can be wet by both oil and water, that some of the crystallites locate in the O/W interface (Figure 14).

34

Food Hydrocolloids

FIGURE 26.

Commercial sample of ice milk showing the flocculated milk solids.

12. Formed Extruded Foods Probably the best example of MCC in an extruded food which utilizes the structuring effect of MCC is the fabricated frozen French fries. Major improvements in the quality of fabricated frozen French fries are achieved at all stages. from initial dough extrusion to final consumption, through the addition of I% or less by weight of microcrystalline cellulose to the ingredient formulation (Figure 28). Because it adds structural firmness and integrity to the dough, MCC (cellulose gel) improves extrudability and reduced breakage after extruding. This structural effect also improves the body and texture of the finished fry, providing a smoother consistency, fewer void spaces, and thinner crust. The result is a more tender, but firm fry with a more pleasing "mouthfeel". A principal benefit achieved through the use of MCC (cellulose gel) is a reduction of approximately 15% in the absorption of cooking oil by the product during frying. MCC also maintains the fry structure retarding of moisture loss from the finished fry during storage under heat lamps, and keeping them firm and fresh-tasting over longer periods of storage after frying. As MCC is added and the level increased, there is a corresponding increase in the firmness as indicated by these Universal Penetrometer readings (Figure 29). The normal life of French fries under heat lamp storage is approximately 4.5 min. Control French fries became limp

Table 6 CORRELATION BETWEEN MOUTHFEEL AND VISCOSITY VS. RATE-OF-SHEAR BEHAVIOR Organoleplic e,,alualion Type

Gum

Starch Polysaccharide B-1459 Sodium carboxypolymethylene Carrageenan Gum karaya Gum lragacanth Gum guar Locust bean gum Carboxymethylcellulose Sodium alginate Low-methoxy pectin Methylcellulose Polyvinyl alcohol Pectin

Cooked , cum

-

Sodium sail of Carbopol 934 SeaKcm® 9 -

-

-

-

CMC 7H XSP 500 cps Exchange® 466 Methocel® 400 Elvanol® 72--60 Exchange® 681

Concenlralion (%)

Rating

2.0 0.15 0.3 1.0 1.0 1.0 0.6 0.7 1.0 1.3 5.0 2.6 7.0 2.5

I

I

2

3 3 2 2-3 3 4 5-6 7 6 6

7

How slim}'

Non Non Very slight Somewhat Somcwhal Very slight Very slight to somewhat Somewhal Moderate Slimy to very Extremely Very Very Extremely

From Szczesniak, A. S. and Farkas. E. H.. J . Food Sci.. 27, 381-385. 1962. Wilh permission.

~

~ :,I

::: ~

~

IJl

36

Food Hydrocolloids 3% modified waxy ma,ze and 1.0%

ooa:-:::::----------RC-591 7600 Cps

1

90

3% modified waxy maize and

o 6%

RC-591 5400 cps.

70 C:

0

.,

~ 60

3% modified waxy maize and

0 5% RC-591 3380 cps

oj

a: 50

c., u

~ AO 30

20 10

4% modified waxy maize

1000 cps

3% modified waxy ma,ze

60 cps.

Time in Minutes

FIGURE 27.

FIGURE 28.

Effect of MCC on clingability.

Structuring effect of 0.5% MCC in frozen fabricated French fried potatoes.

Volume Ill

80

E E

90

·=~ 100 :; ~

a:

37

EFFECT OF MCC ON FABRICATED FRIES HELD UNDER 60°C HEAT LAMP

,,,, ...

-· -.. ----------.................

, ...

-control 0.5% MCC • - • 2.0%MCC

11111111

-...

·········· ,,,,, .... ······-.....-, ········.,,,,,,,

110

~ 120

.,

g

130

,,,

,,,,,,,,,,,,,,,,,,,,,

······

.,~ 140

C

A. Cellulose

B. CMC- Dry

C. CMC - State la or lb

D. CMC - State 11

E. CMC - State Ilb

F. CMC - State Ill

FIGURE 8.

Cellulose gum in various states of aggregation.

is promoted. Note the similarity in shape of the solvent strength curves to the idealized disaggregation curve in Figure 9. The mutual effect of increasing DS and solvating power on dissolution is also shown in Figure 10. Given the most optimum solvation, the temperature of the solvent system plays a further role. Generally, as solvent temperature increases, the disaggregation process is accelerated.

Volume III

57

(I I) Fully Swollen

(lb)

-

-\- -

-

-

_._.....,,...(1-ll)_F_u_lly_D_i_spe-rsed

Panly Swollen

(1) Unaffected by Solvent

Degree of Disaggregation - - - - -

FIGURE 9. gum.

Effect of polymer disaggregation on viscosity of cellulose

Viscosity of CMC Types In Glycerin-Water

(CMC Concentration, 1,75% by Weight) 100.000 . . - - - - - , . - - - - , - - - - . - - - - - - , - - - - .

1,000

300 0

20

40 Water In Solvent, Weight, '!lo

FIGURE I 0. Effect of solvent strength on disaggregation of cellulose gum.

However, increasing solvent temperature enhances the affinity of the particles for each other (fisheye formation). This may become a problem when dispersion is inadequate. The influence of solutes (salts) on the dissolution of CMC is illustrated in Figure l I.

58

Food Hydrocolloids

300 200

~

"'.100

~

-~ 80 i;l

~

60

.1J: 40 C:

~

,.. )NaCl;()() NaCl+ NaOH (pH 10.1); (o) Na 2 SO,; (o) Na,P 2 0 7 • 10H 2 0 (pH 9.5-9.8); (Xl KCI or LiCI

j

lOL,__ __,1.._ _ _.,__....___ __ . , , - - - - ~ - - - - - : : - - : - ' .02 .04 .08 .1 .2 .4 .8 1.0

Molal Concentration of Cation, Including Counterion

FIGURE 11.

Effect of solutes on the viscosity of cellulose gum solutions.

Salts tend to decrease the hydration of the gum and the corresponding solution viscosity. Salt cations provide a screen of counter-ions around the carboxyl group, thereby leading to a reduction of the repulsive forces between carboxyl groups which disfavors dissolution. 19 Order of addition of solutes and hydrocolloid regulates the interaction. When salt is added to fully dissolved CMC, the chains are already separated and viscosity depression by the salt is minimal (Figure 11). However, when CMC is added to saline solution (Figure 11) the chains never have a chance to separate by mutual repulsion. Consequently, dissolution is inhibited and viscosity development is markedly reduced. Figuratively speaking, salts function to maintain the crystalline regions along the chain, especially when order of addition is wrong. Therefore, it is no surprise that the effect of solutes on CMC dissolution is less pronounced with high DS or uniformly substituted material which contains fewer crystalline areas. B. Rheological Behavior Sodium carboxymethylcellulose exhibits several interesting and useful rheological properties upon reaching complete dissolution. To the food technologist, knowledge of these rheological properties can serve as a guide for selection of the proper cellulose gum type to achieve desired textural characteristics in the finished food system. The single most important rheological property of cellulose gum is the ability to impart viscosity to aqueous systems, foods, or beverages. Viscosity is a measure of system resistance to flow when subjected to an applied shearing force. In simple solutions where the dissolved material is low in molecular weight, is nonassociating, and limited solute-solvent interactions occur, the flow is directly proportional to the force applied. The system is said to be Newtonian and the viscosity remains constant as shear stress varies. More complex solutions, however, like CMC respond in a nonlinear manner to applied stress. Here, the dissolved molecules are large, the tendency to reassociate is high and the solvent must exert some solvating force to maintain the polymer in solution. Such solutions are classified as non-Newtonian, and the viscosity changes as shearing action is varied.

Volume III

l

59

NEWTONIAN

....►

en 0

u

en

s:

....z

LI.I

a::

~

A.

C(

SHEAR RATE _ _ _ _ _ _ _ _ _ _..,.. FIGURE 12.

Pseudoplastic flow.

In common with other linear water-soluble polymers, cellulose gum solutions are pseudoplastic; that is, the viscosity decreases as the rate of shear increases (Figure 12). However, if the applied force is removed, the solution will revert instantly to its nonsheared rheology. As a practical food example, cake frostings stabilized with high-viscosity cellulose gum are quite immobile when "poured" from their container (low shear), but thin substantially when spread onto cakes with a knife (higher shear). 49 Upon cessation of spreading (shear removal), the frosting is again immobile. One may contemplate as to why cellulose gum in solution exhibits pseudoplasticity. Basically, this rheological property occurs when the long-chain molecules orient themselves in the direction of flow. Figure 13 provides an oversimplification of the phenomenon involving a Brookfield rotational viscometer. At rest or low shear, CMC polymer chains exist in a random state. At higher shear, the random chains elongate and orient themselves to the direction of flow triggered by the applied force from the faster turning spindle. As chain alignment improves, the spindle turns more easily in the matrix, because the resistance to flow - the viscosity - decreases. When the instrument is turned off, the random state is instantly reassumed. The pseudoplastic behavior of CMC varies with the molecular weight (chain length) and DS of the particular CMC grade. In Figure 14, the effect of increasing shear on different molecular weight grades of CMC may be observed. All behave as Newtonian materials at very low shear rates. As the shear rate increases, low molecular weight types become less pseudoplastic than high molecular weight types. Thixotropic flow is another rheological property characteristic of cellulose gum. The term itself, thixotropic, is derived from the Greek - "thixis" meaning to strike or touch and "tropo" meaning to turn or change. The Greek nomenclature provides an insight as to the nature of this rheological behavior. Basically, thixotropy is a type of pseudoplastic flow with a time dependency. Figure 15 illustrates the phenomenon. Similar to pseudoplastic flow, thixotropic cellulose gum solutions undergo shear thinning with an increase in applied shear force. However, when the shear force is removed, time is required for the thixotropic solution to revert to its original viscosity, whereas a pseudoplastic solution reverts back instantly after shear removal. Upon preparation, thixotropic cellulose gum solutions or products containing the gum will display an increase in apparent viscosity while remaining at rest for a protracted period of time. If sufficient agitation (a shear force) is applied, the viscosity will be reduced. If a rest period is renewed, the viscosity will again begin to build.

60

Food Hydrocolloids BROOKFIELD SPINDLE (AT REST OR LOW SHEAR)

HIGHER VISCOSITY FIGURE 13. 100,000

BROOKFIELD SPINDLE (AT HIGH SHEAR)

LOWER VISCOSITY

Why cellulose gum solutions are pseudoplastic.

,---.....----,r----,----,.----.----.----.--.......

'"""'"" °'

l',l,,ITICU SUSN:NSION ltfS!

AT

l'OIJIINC;

UNDE1 GIAY!TY

.001

.01

FIGURE 14.

0.1

1.0 10 100 SHEAR RATE csec-1)

1000

10,000

100,000

Typical flow behavior of cellulose gum solutions.

◄•...,_;CO=NS;;.;T.;.;ANT;.;.;_.,►+I, . _ • - - - - - - N O SHEAR-----► SHEAR

TIME - - - - - - FIGURE 15.

Ideal curve for thixotropic solutions.

In extreme cases, the thixotropic viscosity build may approach a gel-like consistency . 18 •19 •23

If enough force is applied, the structure is broken and consistency is lessened. Such extreme

thixotropic behavior is analogous (but not identical) to the rheology of a modified Bingham body where a yield stress is required to initiate flow :22

Volume Ill

61

FIGURE 16. Thixotropic and nonthixotropic solutions of cellulose gum. Solution of regular Hercules cellulose gum (left) is thixotropic; "$"-type Hercules cellulose gum (right) is essentially nonthixotropic.

The key factor responsible for the thixotropic nature of certain cellulose gum solutions is the uniformity of substitution and/or lack of substituents which cause' 'insoluble'' (somewhat hydrophobic) regions along the chain. 18 •22 These insoluble regions or "gel centers" tend to reassociate with time, forming a three-dimensional network or structure which translates as a viscosity increase. Shear, of course, will break the structure, but not permanently. Elliott and Ganz23 concluded that thixotropy in CMC solutions arises because of the presence of unsubstituted crystalline residues in the CMC. These would be present as fringe micelles which could form cross-linking centers that would entrap a relatively large amount of molecularly dispersed CMC by electrostatic hydrogen bonding, or Van der Waals forces, and thus enable a three-dimensional structure to be set up. 23 The thixotropy phenomenon is concentration dependent; with more gum in solution, a "crowding effect" occurs which enhances the magnitude of the thixotropic increase. High viscosity types as well as low OS types of CMC (0.4 to 0. 7) will generally display thixotropy, because these species have the greatest amount of unsubstituted or insoluble regions. Figure 16 visualizes the difference between a uniformly substituted, smooth flowing, nonthixotropic CMC solution vs. a randomly substituted, thixotropic solution of CMC with structured flow. Solution appearance can be altered from a thixotropic (applesauce consistency) to a very smooth (syruplike) consistency with no change in OS by special reaction conditions and raw material selection during manufacture. 6 Uniformly substituted, smooth flowing cellulose gum is highly desirable as a texturizer for food systems such as syrups, puddings, or frostings where smooth consistency is a must. Thixotropic cellulose gum finds use in foods requiring a structure "grainy" texture. Sauces and purees are typical examples. 1. Gelation Sodium carboxymethylcellulose will undergo gelation in the presence of specific cations or shear conditions. Trivalent cations, such as Al+ 3 , Cr+3, or fe+3, may precipitate, form very thixotropic solutions, or gel CMC. Careful selection of ion concentration, regulation of pH and use of a chelating agent for controlled ion release favor gelation. Depending on conditions and technique, various gel strengths may be produced. Ganz 18 suggests that gel formation rather

62

Food Hydrocolloids

than precipitation may be achieved by avoiding localized concentrations of trivalent cation through the use of sparingly soluble salts such as basic aluminum acetate or by the slow addition of a dilute solution of a more soluble salt, e.g., alum. As to the mechanism of gelation of cellulose gum with aluminum or other polyvalent ions, it is believed that the ion serves as a cross-linking agent for polymer chains through salt formation with adjacent anionic groups. 18 High DS cellulose gum is more apt to gel with trivalent cations. Unfortunately, aluminum cellulose gum gels have not found an application in the food industry due to their astringent taste and poor mouthfeel. Gels may be prepared from cellulose gum when polymer of sufficiently low DS is subjected to high shear conditions. 19 ·22 •23 Elliott and Ganz22 demonstrated this gelation technique by preparing gels from low-to-high DS CMC (5% solutions) at high shear in a Waring Blendor® . Subsequent characterization of the effect of DS on gel strength using a Weissenberg Rheogoniometer was made. The sample made from the lowest DS type (0.18) showed the sharpest stress peak and extremely rapid stress decay on the Rheogoniometer trace of all trials, indicating firmest gel strength .22 These gels were judged organoleptically to be unctuous , whereas those of higher DS were not. Matz 28 defined unctuous foods as fatty substances. Webster's Third International Dictionary defines "unctuous" as having the nature or qualities of unguent or ointment, or smooth and greasy in texture. Elliot and Ganz postulated the mechanism of CMC shear-gels as follows: ''The formation of a gel when a thixotropic CMC solution without cross-linking cations is subjected to high power input stirring is believed to arise because of the dispersion and disaggregation of the fringe micelles arising from the crystalline residues , thus providing more potential crosslinking points , and not by disruption of the individual cellulose crystalline residues." 11 ·2 3 ·29 One would anticipate more crystalline residues to be present in low DS CMC than in high DS CMC. Nijhoff 30 has been granted a U.S . patent on the use of low DS CMC to form unctuous gels for low-calorie spreads, dressings, and desserts processed with homogenization shear. This work cited CMC in a DS range of 0.35 to 0.40 as optimum for the desired effect. C. Solution Viscosity 1. Effect of Concentration Figure 17 shows the relationship of concentration and apparent viscosity of various cellulose gum types available from one manufacturer. The increase in viscosity is not directly proportional to changes in concentration, but instead an exponential function exists . A good rule of thumb is that doubling the concentration will usually increase the viscosity tenfold . It is particularly important to remember the effect of concentration on viscosity when developing a food product or making minor adjustments to products during processing. At a fixed concentration, the DP (degree of polymerization) regulates the viscosity of cellulose gum. This relationship is straightforward - the higher the DP (the longer the polymer chain), the higher the viscosity of the CMC derived from it. Food grade cellulose gum has a molecular weight range between 40,000 and 1,000,000.6

2. Effect of Temperature As with most water-soluble polymers, the viscosity of cellulose gum solutions decreases with increasing temperature (Figure 18). U oder normal conditions, the effect of temperature on viscosity is reversible and raising or lowering the solution temperature has no permanent effect on the viscosity characteristics of the solution. However, prolonged heating at very high temperatures will tend to depolymerize cellulose gum and permanently decrease the apparent viscosity. Hence cellulose gum, like many other long chain polymers, is not perfectly retort stable.

Volume III 30,000

63

----~~-~----r--.--.....---,---,-----,

20,000

7L

C/l

0..

(.)

c.5

1,000 "' N

~ >.... iii 0

~

>

z 0

.::

3

5l

100

10 1---llt---- ...

·u; 0 0

.!!!

>

*

100

N

1000

10,000

100,000

Number & Weight Average Molecular Weight-Mn, Mw FIGURE I. Molecular weight/viscosity correlation. (Reprinted by permission of the Dow Chemical Company. 28)

In theory it is possible to determine molecular weight of water-soluble polymers by gel permeation chromatography as has been done for organosoluble cellulose derivatives. 29 ·30 However, the very large hydrated size of the water-soluble cellulose ethers coupled with extreme sensitivity of the hydrated polymer volume to the presence of small quantities of electrolytes or other interacting species has not allowed broad development of this technique. The use of gel permeation chromatography to determine molecular weight of polymers in aqueous solution is currently a topic of research interest.

VI. PROPERTIES A. Solubility Cellulose itself is highly insoluble in most solvents due to the very high level of intramolecular hydrogen bonding in the cellulose polymer. A high degree of crystallinity is also present which reduces solubility as well. In order for dissolution of the polymer to take place, the crystallinity and intramolecular hydrogen bonding must be reduced. In the case of the cellulose ethers, this is accomplished by etherification. In effect, the ability of the cellulose molecule to hydrogen bond is reduced, but the capacity of the polymer

128

Food Hydrocolloids

Table 2

VISCOSITIES OF METHYCELLULOSE OF VARIOUS MOLECULAR WEIGHTS Viscosity grade 2%, 20°C, mPa·S

Intrinsic viscosity (1)), dt/g at 20°C

Number average DP.

Number average molecular weight, M.

5 10 40 100 400 1,500 4,000 8,000 15,000 19,000 40,000 75,000

1.2 1.4 2.05 2.65 3.90 5.7 7.5 9.3 11.0 12.0 15.0 18.4

53 70 110 140 220 340 460 580 650 750 950 1,160

10,000 13,000 20,000 26,000 41,000 63,000 86,000 110,000 120,000 140,000 180,000 220,000

From Encyclopedia of Polymer Science and Technology, 3, lnterscience, New York, 1965. 504. With permission.

molecule to be hydrated is not eliminated. In addition, replacement of hydroxyls by bulkier ether groups sterically inhibits close fitting and crystallization of cellulose molecules. As the level of etherification is increased, the cellulose molecule proceeds from a species which is swoJien by alkali to a partial ether which is soluble in dilute alkaline solution. This takes place at a methoxyl substitution of about 16 to 22.5%, corresponding to a DS of about 0.9 to 1.3. Further etherification results in water solubility being obtained at a DS of about 1.4, equivalent to a methoxyl content of about 24%. Swelling and partial solubilization in various organic solvents is noted at a DS of 2.1, corresponding to 34% methoxyl content. Water solubility with good organic solubility is found at about 36% OCH 3 , or a DS of 2.25. Water solubility is eventually lost altogether, and the methylcellulose becomes soluble in organic solvents at a DS of about 2.6, in the range of 40% or higher methoxyl substitution. The effect of hydroxypropoxyl substitution is to broaden the range of both water and organic solvent solubility. The most organosoluble of the methylhydroxypropylcellulose ethers which are permitted for food applications are those which have nearly the maximum permitted substitution of both substituents. Such a product is typefied by METHOCEL® E which may have a DS of as high as 2.03 methoxyl and an MS of 0.336 hydroxypropoxyl. This material is soluble in a number of solvents at elevated temperatures and in aqueous/organic mixed solvents at room temperature as may be seen in the data presented in Table 3. When preparing aqueous solutions of the cellulose ethers, care must be taken to prevent formation of Jumps. When properly dispersed, clear solutions may be obtained in a matter of minutes. If, due to improper solution makeup techniques, lumps are allowed to form, it often requires many hours to effect complete dissolution. There are three commonly used techniques to promote full dispersion and uniform wetting of methylcellulose particles to promote rapid and complete dissolution. The first of these takes advantage of the unique thermogelation properties of this family of gums. In this method, the cellulosic gum is dispersed in water which has been heated to a temperature above the gelation temperature of the gum; i.e., the temperature above which the compound is insoluble in water. NormaJiy, the dispersion is accomplished using about one quarter to one half of the total water required. Once the polymer is fully wetted and dispersed in the

Volume Ill

129

Table 3 REPRESENTATIVE SOLVENTS FOR METHOCEL® E BRAND CELLULOSE ETHER AT ELEVATED TEMPERATURES Compound

Glycols Ethylene glycol Diethylene glycol Propylene glycol I ,3-Propanediol Glycerine Dowanol® EE Ethylene glycol Ethyl ether Dowanol® TPM Tripropy lene glycol Methyl ether Esters Ethyl glycolate Glyceryl monoacetate (acetin) Glyceryl diacetate (diacetin) Amines Monoethanolamine Diethanolamine

Solubility point, ec

Degree or solubility"

197.3 244.8 188.2 214 290 134.7

158 135 140 120 260 120

C C C C p

242.4

160

p

160 127/3 mm I23-133/4 mm

110 100 100

C C C

170--172 268-269

120 180

C C

Boiling point, ec

C

C: Completely soluble; P: partially soluble Reprinted by Permission of The Dow Chemical Company, 1978.

hot water, the rest of the water is added as ice or cold water while agitation is continued. This addition cools the dispersion and full dissolution occurs rapidly (Figure 2). A second technique which is often used when a number of other dry ingredients are called for in the formulation is to dry blend the gum with the rest of the dry ingredients. When liquid is eventually added, lump formation is prevented and hydration takes place normally. A third method involves the wetting of the cellulosic material with nonaqueous liquid ingredients, e.g., propylene glycol, followed by the addition of water which then promotes lump-free dissolution with adequate agitation. The choice of technique involves consideration not only of the convenience of incorporation, but also the function of the cellulosic gum in the system to which it is being applied. Experimentation may show that the procedure for achieving dispersion may affect the performance of the gum in the system due to the degree of hydration which is achieved. This is particularly true in food fonnulations due to the limited amount of water which is present and the competition of the various hydrophilic ingredients for the available water. B. Viscosity The eighth root of measured methylcellulose and hydroxypropylmethylcellulose solution viscosities shows a linear relationship with concentration which is illustrated in Figures 3 and 4. This is an empirically derived relationship. Since solutions of these cellulose ethers, other than very dilute solutions, are highly pseudoplastic, the observed viscosity is highly dependent on the viscometer used. This property will be discussed in more detail later. For very dilute solutions of certain cellulose ethers, the Martin equation has been shown to be valid with a Martin k of 0.191 for hydroxyethylcellulose. 31

130

Food Hydrocolloids 10,000 , - - - - - - - - - - - - - - - - - - - - - - ,

Viscosity on Initial Cooling

.,

of METHOCEL A15C

.-:

.,-/

,, I ,"

1000

0..

E

i

I

I

I I

"8

~

>

I

100 Viscosity on Initial Cooling _ of METHOCEL K15C

10.___.___ _.__....__ __.__ __.__ __._ ___.___..___...__~ 0 40 20 100 60 80 Temperature, °C

212

176

140

104

68

32

Temperature, °F

FIGURE 2. Viscosity development of METHOCEL® Kl5C and METHOCEL® Al5C brand products slurried at 2% in hot water. (Reprinted by permission of the Dow Chemical Company. 28 )

100,000 70,000 40,000 20,000 (.)

0

0

N

10,000

@)

5,000

CV

3,000

".'

c..

E

i -~ >"'"

1,000 300

100 40

10 3 % METHOCEL Cellulose Ether

FIGURE 3. Viscosity-concentration chart for high viscosity METHOCEL® products. (Reprinted by permission of the Dow Chemical Company. 28 )

Volume Ill

131

40,000 20,000 10,000

(.)

'b

"' @,

.

.,

0.

E

i

·s ~

>

5,000 3,000

1,000 500 300

100 40 10 3

Concentration, % of METHOCEL

FIGURE 4. Viscosity-concentration chart for low viscosity METHOCEL® products. (Reprinted by pennission of the Dow Chemical Company. 28 )

log(TJ,/C)

= log[TJ] + k[11]c,

It is expected that this equation will also hold for methylcellulose and hydroxypropylmethylcellulose, although a different k value may be found . The viscosity of an aqueous solution of methylcellulose or hydroxypropylmethylcellulose will initially decrease upon heating . However, when the gel temperature for the particular gum is reached, the solution will gel, causing a very substantial increase in measured viscosity and the development of a yield value . This gelation phenomenon , as shown in Figure 5, will be discussed in detail separately. Since these gums are nonionic, their solutions are relatively insensitive to changes in pH. In this respect, they differ significantly from both cationic and anionic water-soluble polymers which normally show dramatic changes in solubility and solution viscosity near their isoelectric points. In common with many polysaccharides, the cellulose ethers undergo hydrolysis at extremes of pH (less than pH 3 or greater than pH 11 ), particularly in strong acid solutions . In vinegar-containing systems, they are reasonably stable, but at lower pH values, hydrolysis possibilities must be considered. The hydrolysis rates of some methylcelluloses in hydrochloric acid solution are shown in Figure 6. It is seen that the effect of level of substitution on hydrolysis rate is only minor. The nonionic character of methylcellulose and hydroxypropylmethylcellulose which is responsible for the stability of viscosity to changes in pH also result in solutions which are highly tolerant to electrolytes. Although added electrolytes do cause gradual viscosity loss with increasing concentration, these gums are less sensitive to electrolytes than are ionic water-soluble polymers. However, the presence of certain surfactants, in particular the sulfates and sulfonates, has profound effects on the viscosity of cellulose ether solutions . The effects of some additives and of some of these surfactants are tabulated in Tables 4 and

5.

132

Food Hydrocolloids 5.1 5 4.9 4.8 4.7

"'°

-=

4.6

160 140

.

120

.;, 100

Q.

E 90

4.5 4.4 4.3

·~ 80

4.2 4.1 4

60

>

. > 0

CJ

70

50

3.7

401 3

I

3.3 Temperature

3.1

I

3.4

-oc, 10

20

30

60

3.5

-1.x1C>3 T

FIGURE 5. Viscosity-temperature relationship for 2% aqueous solution of METHOCEL® AIOO methylcellulose at a shear rate of 86 sec: 1 • (Reprinted by permission of the Dow Chemical Company. 21)

6.5 . - - - - - - - - - - - - - - - - - - - .

6.0

_

1.81 N HCI 17% OCH 3

7.5

7.0

1.81 N HCI28.8% 0CH 3

~

Cl

0

...J

8.5

8.0

9.5

0.0030

0.0032 1/T Abs.

0.0034

FIGURE 6 . Arrhenius plots for hydrolysis of methylcelluloses in HCI. (Reprinted by permission of the Textile Institute. ·'')

Volume 1/1

133

Table 4 GRAMS OF ADDITIVE TOLERATED BY 100 cc 2% SOLUTION WITHOUT SALTING OUT METHOCEL® Additive NaCl MgCI, Na,SO4 Al,(SO4 ) 3 Na,CO 3 Na,P04 Sucrose

AIS II II 6 3.1 4 2.9 100

A4M 7 8 4 2.5 3 2.6 65

FSO 17 35 6 4.1 5 3.9 120

F4M II 25 4 3.6 4 3.5 80

KIOO

K4M

JSM

19 40 6 4.1 4 4.7 160

12 39 4 3.6 4 4.3 115

IO 22 3 2.7 3 2.5 100

Reprinted with permission of the Dow Chemical Company. 1974.

In general, the effects of additives on viscosity must be determined experimentally for particular systems, since it is not possible to predict with accuracy the magnitude or direction of these effects. C. Solution Rheology As previously stated, the rheological behavior of methylcellulose and hydroxypropylmethylcellulose solutions is dependent upon the concentration of the dissolved polymer hydrocolloid. Other factors which affect the solution rheology include the molecular weight of the polymer, the solution temperature, and as has been noted, the presence of other solutes. Solutions of methylcellulose and hydroxypropylmethylcellulose generally exhibit pseudoplastic behavior, i.e., the solution viscosity decreases with increasing rate of shear. However, at very low shear rates, solutions of these gums exhibit Newtonian properties. The degree of pseudoplasticity increases with increasing concentration and increasing molecular weight. Therefore, the shear rate above which pseudoplastic behavior becomes apparent decreases as higher molecular weight polymers are used and as the solution concentration is increased, as is illustrated in Figures 7 and 8. In addition to the above shear rate dependence, certain systems containing methylcellulose and hydroxypropylmethylcellulose demonstrate a thixotropic behavior, i.e., the viscosity will decrease with time at constant shear. This property is often exhibited by methylcellulose solutions containing a substantial amount of undissolved solids. D. Thermogelation I. Definition The unique property of the formation of completely reversible gels of methylcellulose and hydroxypropylmethylcellulose upon heating their solutions is responsible for many of the food use applications of these products. 1034 The applications include, among others, binders for reconstituted meat and vegetable products, foam stabilization, film formation in fried foods, stabilization of fruit pie fillings during baking, and dough strengthening during the baking of low-gluten bakery products. 16•35 The phenomenon of thermogelation of methylcellulose products is graphically demonstrated in Figure 9 showing the effect of heating on the viscosity of a methylcellulose solution. The incipient gelation temperature (IGT) is defined as the temperature at which the viscosity reaches a minimum. Once gelation begins, viscosity build takes place due to intermolecular and intramolecular association. Since the dehydration and association leading to gelation are time-dependent processes, the rate of temperature change will have an effect upon the gelation

Table 5 EFFECT OF ADDITIVES ON VISCOSITY OF l % SOLUTIONS OF METHOCEL® CELLULOSE ETHER

Trademark

% Additive

Increase in viscosity of METHOCEL® brands Producer

Conco AA5-35S

I

Con1inen1al Chemical Co .

Conco sulfate EP

I

Continental Chemical Co.

Miranol® C2M cone.

I 25

Miranol Chemical Co.

I 10

Miranol Chemical Co.

I IO

Miranol Chemical Co.

I 10

Miranol Chemical Co.

Polystep® B-11

I

Stepan Chemical Co.

Qualcmary 0

I

Geogy Chemical Corp.

Span® 60 Teepol® 610

I I

ICI Americas Shell Chemicals UK Ltd.

Trilon® CQ 400

I

Rohm & Haas Co.

Tween® 20

I

ICI United S1a1es

Ultrawe1® 30 DS

I

ARCO Chemical Co.

Miranol® L2MSF

Miranol® 2MCT modified

Miranol® HM cone.

Description Sodium dodecyl benzene sulfonale Diethanolamine lauryl sulfalc Dicarboxyla1ed imidazoline derivative of coconut fatty acid Dicarboxylated imidazoline dcrivalive of lall oil fany acid Polyoxyethylene (3)1ridecyl sulfate sail of a dicarboxylated imidazoline derivalive of coconul fally acid Monocarboxylaled imidazoline derivative of !auric acid Ammonium lauryl elhoxylale (4) sulfale Qua1ernary ammonium imidazoline derivative Sorbitan monos1eara1e Secondary sodium alkyl sulfonale Stearyl dimethyl henzyl ammonium chloride Polyoxyethylene (20) sorbitan monolaurate Sodium linear alkylale sulfona1e

-

"O

£-

3,000

C)

C:

f in

.;

(!)

2,000

1,000 ,___ _....__ _.....__ _ _...__ _....__ ___,__ _ _...__ __.

0

2

4 3 Time, Hours

5

6

7

FIGURE 12. Rate of gel strength development for a 2% solution of METHOCEL® A4C upon heating at 65°C. (Reprinted with permission of the Dow Chemical Company. 10)

Volume III

139

7000

40

~E

u

~.,

::,

"C

~...

0

C

>-

.,~ a. .,E

£

C)

6000

I-

~

en

~ (.:,

30

20

C

L-----"------'---.....___ ___.__ _ _.___ _~5000

0

2

3

4

5

6

Concentration of NaCl,%

FIGURE 13. Incipient gelation temperature (IGT), incipient precipitation temperature (IPT), and gel strength of a 2% solution of METHOCEL® Al5C methylcellulose as a function of NaCl concentration. (Reprinted by permission of the Dow Chemical Company. 10)

the IGT is raised by the addition of low levels of hydroxypropoxyl substitution (see Figure 16) and that the sensitivity of the IGT to concentration is reduced by increasing the amount of hydroxypropoxyl substitution at a relatively constant level of methoxyl substitution as may be seen from Figure 17. Accompanying the raising of the IGT with added hydroxypropoxyl substitution, there is a large reduction in the strength of the gel formed. In Figure 18, it is seen that a drop in gel strength to one fifth of the original level is obtained as the hydroxypropoxyl content is increased from Oto an MS of approximately 0.17 at an essentially constant methoxyl DS of about 1.75 . The dependence of gel strength phenomena upon this collection of factors allows substantial freedom in adjusting gel strength and texture while maintaining other properties, such as binding strength , film formation , or solution rheology, at a desired level. The effects of various ionic and nonionic additives on gelation temperature are shown in Table 6 and in Figures 19 and 20. It is important to food applications that it is possible , by suitable selection, to either increase or decrease the gelation temperature. The normal effect of these additives upon gel strength is that those which raise the gelation temperature tend to soften the gel while those which lower the gel temperature make the gel firmer.

E. Compatibility With Other Hydrocolloids The effects of electrolytes, pH changes, and certain surfactants have already been dealt with earlier in this chapter in discussing effects of additives on viscosity. In addition to the

140

Food Hydrocolloids 10,000--------------------------, 8000

5000

.E ~

"'C>

A15C

A4M

3000

"tl

~ C) C

~

2000

ui -.;

Cl

Numbers Designate METHOCEL A Samples of Different Viscosity Grades.

1000 800

500..__ _ _ _ _ _ __.__...__ _ _ _ _ _ _ _ _ _ _ __. 30

50

80

100 MW x 10·3

200

300

500

FIGURE 14. Gel strength of 2% aqueous methylcellulose gels after 4 hr at 65°C as a function of molecular weight. (Reprinted by permission of the Dow Chemical Company. 10 )

tolerance of solutions of methylcellulose gums to such compounds , they are also compatible with a substantial number of synthetic and natural water-soluble polymers. These include acacia, gum arabic, tragacanth, starch, starch ethers, carragheenan , the alginates, poly(vinyl alcohol), and xanthan gum as well as many others (see Table 7). The limits of compatibility are affected by the structure of the added hydrocolloid and the molecular weights of the gums. Normally, lower molecular weight methylcellulose gums are more compatible than are higher molecular weight examples. In addition to simple compatibility, synergistic viscosity increases are sometimes exhibited by mixed gum systems such as methylcellulose with starch ethers or carboxymethylcellulose. 25 In general, the behavior of mixed gum systems in food applications must be determined experimentally, since the effects of other components in the total product system may greatly alter the effects seen in a pure water system. In cases in which fillers or solids are combined with methylcellulose solutions, no salting out or precipitation is observed . In fact, low molecular weight methylcellulose and hydroxypropylmethylcellulose may be used as dispersants in such systems. Again, the use of gum combinations including these products often leads to improved stabilization of emulsions and solids suspensions when compared to that obtained for either gum alone. Performance of gum combinations must normally be determined experimentally although the manufacturers of the cellulose ethers have published some recommended gum systems in their product literature. The effects of additives on solutions of methylcellulose and hydroxypropylmethylcellulose may best be predicted by bearing in mind the expected effects of the additives on the

Volume lll

Heating Time -- 3 Hrs.

20

.

"E

~ a,

C:

>-

15

"O ~

0'

X

-5

"'C:~

10

en ai

.._ A25

(!)

•

5

A4C

■ A15C

0 ..__ __._ _ _...__ _ _....__ __.__ _ _....__ ____._ _ _....__ ____. 0

2

3

4

5

6

7

8

Concentration, %

FIGURE 15. Gel strength of METHOCEL® A methylcellulose of different viscosity grades at 65°C as a function of concentration. (Reprinted with pennission of the Dow Chemical Company. 36)

60---------------------(.J

0

55

•

Methoxyl OS = 1.63 - 1.88 2% Solution Viscosity= 400 - 8,000 mPa • s

4 0 ' - - - - - ~ ~ - - - - _ ._ _ _ _ ___,__ _ _ ____, 0.20 0.15 0.10 0.05 0 Hydroxypropyl MS

FIGURE 16. Incipient gelation temperatures of hydroxypropylmethylcellulose as a function of hydroxypropyl molar substitution. (Reprinted by pennission of the Dow Chemical Company. 10)

141

142

Food Hydrocolloids

60.------------------------, 55 ~ ~- 50

E ~

" I"

C.

E 45 C:

0

-~ 40 .;

'-' C:

·a " ·.;

35

C:

25 '-----''----'---'---'---'----'---'---'--.......L-.......L--l 1 2 4 5 7 3 6 8 9 10 11 12 Concentration, Wt. %

FIGURE 17. Incipient gelation temperature of different METHOCEL® products as a function of concentration. (Reprinted with permission of the Dow Chemical Company.) 5,000 . + - - - - - - - - - - - - - - - - - - ,

Methoxyl OS = 1.63 • 1.88 2% Solution Viscosity = 400 - 8,000 cP 4,000

N

E

.,a,

~ C

>-

3,000

"C

£

C)

C

~

en .;

(!)

2,000

1,000

O'------L-------------0.10 0.15 0

0.20

0.05

Hydroxypropyl MS

FIGURE 18. Gel strength of 2% aqueous hydroxypropylmethylcellulose gels after 4 hr at 65°C as function of hydroxypropyl molar substitution. (Reprinted with permission of the Dow Chemical Company. 10 )

Volume III

143

Table 6 EFFECT ON GELATION TEMPERATURE NOTED WITH ADDITIVES TO 2% SOLUTIONS OF METHOCEL® CELLULOSE ETHER METHOCEL"'

METHOCEL''

•c

%

Compound

Control (no additive) NaCl MgCI," FeCI, Na,SO4 Al,(SO4 ), Na,CO,S Na,PO. Sucrose Sucrose Sorbitol Glycerineh Ethanol Polyethylene glycol 400h Propylene glycolh

5 5 3 5 2.5 5 2.0 5 20 20 20 20 20 20

32 51 44 30 34 >75 52 59

•c

Of 122 91 107 107 Salted out Salted out Salted out 89 124' Ill 86 93 >167 126 138

50 33 42 42

METHOCEL''' K4M

FISC•

AISC

Additive

OF

"C

145 105 125 127 Salted out 113 Salted out 107 151 138 115 140 >167 >176 >176

63 41 52 53 45 42 66 59 46 60 >75 >80 >80

85 59 67 76 48 52 84 61 48 65-70 >75 >80 >80

OF 185 138 153 169 Salted out 118 Salted out 125 183 142 118 149-158 >167 >176 >176

Nore: Of the compounds in the table, sucrose, ethanol, and the two polyglycols raise the gelation temperature.

Unlisted additional compounds that raise the thermal gel temperature include Armac®··, Armac®HDT'. Hyamine 1622,d alkali metal thiocyanates, and urea.

' ' '

A special viscosity grade made by blending. The Dow Chemical Company Armour and Company Rohm & Haas Company

Reprinted by permission of the Dow Chemical Company, 1978.

25..---------------------.45

;)

20

36 u. 0

ci E Q)

I-

-.;

0

%

3

4

s

6

~SlE CONCENTRATION, W/V

7

e

FIGURE 2. Viscosity as a function of concentration of solutions of TKP compared to starches. (From Rao. P. S. and Srivastava. H. C .. Industrial Cums. 2nd ed .. Whistler. R. L .. Ed .. Academic Press. New York. 1973. 369.)

unless it is heated for 20 to 30 min. 5 The solution exhibits typical non-Newtonian flow properties common to most other hydrocolloids. In general, the viscosity of TKP dispersions is much higher than those of starch solutions of equal concentration, as shown in Figure 2. 5 Tamarind seed extract or polysaccharide is more soluble but still requires heating to obtain maximum solution viscosity. A typical 1.5% gum solution will yield a viscosity of 500 to 800 cps at 25°C. 2 Typical viscosity-concentration relationships are shown in Figure 3. The relationship of tamarind seed polysaccharide viscosity vs. shear rate is shown in Figure 4 and appears to indicate Newtonian flow behavior at low viscosity concentrations.

B. Effect of pH Tamarind seed gum or polysaccharide has excellent stability over the acid pH range and

196

Food Hydrocolloids

1000

E

e-

0

(')

500

(.)

0

IO N

vi a..

(.)

...>

·;;; 0

rn

>

100

50

0.2

0.4 0.6 0.8 1.0 1.2 1.4

1.6

Concentration (%)

FIGURE 3. Viscosity concentration relationship of tamarind seed extract. (Courtesy of Dainippon Pharmaceutical Co., Inc .. Osaka. Japan.)

Maximum viscosity of TKP solutions was reported to be in the pH range of 7.0 to 7.5, 5 which is somewhat at variance with studies on the pure extract.

C. Effect of Electrolytes Tamarind seed gum shows excellent stability in high concentrations of salt (20%) as shown in Figure 6. 2 Other electrolytes have some effect on viscosity of TKP solutions. Copper sulfate and zinc chloride reduce the viscosity while soluble calcium and magnesium salts have no appreciable effect; calcium chloride is even reported to cause an increase in viscosity. 5 D. Effect of Temperature Tamarind seed gum shows good stability to heat at lower temperatures (65°C) over a pH range 3.0 to 7.0. At higher temperatures (100 to l 10°C), tamarind gum is stable at neutral pH, but degrades rapdily at lower pHs, similar to many other gums. 2 E. Effect of Sugars Sugars have an unusual synergistic effect upon tamarind seed polysaccharide. As sucrose

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u

0

It)

N

vi a..

\

191

o - - o GUAR GUM x - - x LOCUST BEAN GUM .o.--.o. XANTHAN GUM • - - • GLYLOID3A

CONCENTRATION 0.3%

~~

(.)

~ 102

·;;; 0

0

~

>

x-x----x------x

10

•-•----•------•

6 12

30

D (rpm)

60

FIGURE 4. Rheological behavior of tamarind seed extract. (Courtesy of Dainippon Pharmaceutical Co., Inc., Osaka, Japan.)

or glucose is added to a solution of tamarind seed gum, the viscosity increases markedly (Figure 7), and when the concentration of sugar exceeds 40%, a gel forms. 2 ·3 F. Gelation Tamarind seed polysaccharide has the ability to form gels in the presence of sugar or alcohol. In this respect, it is similar to pectin and can be used to form pectin-like gels in such products as jams, jellies, marmalades, and preserves. 3 Good quality gels can be made using tamarind seed gum at concentrations of 0.5 to 1.5% with sugar concentrations ranging from 70% down to as low as 45%. If alcohol (up to 20%) is added, the amount of sugar needed to form a gel can be substantially reduced and even eliminated in some cases. 2 •3 To form a gel, heating is required in order to get all of the gum into solution and upon cooling to room temperature, the gel will form. Maximum gel strength is reported to be at pH 2.7 for l.0% gum concentration. 3 The relationship of gel strength to gum and sugar concentrations is shown in Figure 82 while the relationship of gel strength to sucrose and ethanol concentrations is shown in Figure 9. 2

198

Food Hydrocolloids

200 E Q.

0 (")

1.0% Solution

180

(.)

•

0

Ln

N

Cl)

Q.

160

2

~

., 0 .,

140

120 100 2

3

4

5

6 7 pH

8

9

10 11 12

• • - - - • • pH Adjustment by citric acid o----

8

·;;; 7

------.____.

0

"' 6 a,

> ·.:; a,

ai

a:

-----··-----·

5 4

3 2

10

30

60

90

days at room temperature FIGURE 6. Stability of tamarind seed extract in salt solution. (Courtesy of Dainippon Pharmaceutical Co .• Inc., Osaka, Japan.)

G. Film-Forming Properties TKP films can be prepared by conventional pouring of dispersions onto a glass plate, spreading it into a thin layer, and allowing it to dry. The resultant films are smooth, strong,

Volume III ~

~

80 GLYLOID 3A 0.5%

...

0,

0 M

(.)

0

60 GLYLOID 3A 0.2%

It)

N

vi

0.. (.)

...

199

40

>

·;:;; 0 .u,

>

20 SUCROSE ONLY 0

40

20

60

Concentration of sucrose (%)

FIGURE 7. Synergistic effect of sucrose on tamarind seed extract viscosities. (Counesy of Dainippon Pharmaceutical Co.. Inc .. Osaka. Japan.)

x--x GLYLOID 3A

800 X

700

"E

600

2

500

\

~

,£ C:

CJ)

ai

(!I

\

400 300 200

100 0

,.___.,.GLYLOID3A 0.5%

X

CII

...~

1.5% o--oGLYLO1D3A 1.0%

X

JI r~~·"'· X

0~ \

vnf';

40

45

50

55

~~n

60

65

Concentration of sucrose (%)

70

FIGURE 8. Relationship of gel strength to sucrose concentration. (Counesy of Dainippon Pharmaceutical Co .. Inc .. Osaka. Japan.)

continuous, and extensible. They compare well with those of starch and appear to be more adhesive. 5

VII. FOOD APPLICATIONS In the U.S., tamarind seed gum or polysaccharide is not permitted in food products under current FDA regulations, probably because no user or supplier saw fit to petition for its use

200

Food Hydrocolloids 1800

...

--

E tJ

.!!!!

... ...... tn

J:. Q

C

G)

-a;

(!)

1600

GLYLOID3A 1.2%

1400

SUCROSE 23%

1200 1000 800 600 400 200

0

4

8

12

Ethanol(%)

15

19

FIGURE 9. Relationship of gel strength to sucrose and ethanol concentrations. (Counesy of Dainippon Pharmaceutical Co.. Inc .. Osaka. Japan.)

Table 2 TAMARIND GUM FOOD APPLICATIONS IN JAPAN2 Food Filling (flour paste) Ice cream. sherbet Sauce. gravy Tomato ketchup Canned food Jam. marmalade Mayonnaise, salad dressing Fruit juice Cake mixes Powdered soup Noodle Pickles

Function Syneresis inhibitor Stabilizer Thickening agent Thickening agent Thickening agent Gelling agent Stabilizer Thickening agent Thickening agent Thickening agent Improving texture Thickening agent. syneresis inhibitor

Use amount(%)

0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

~ ~

= =

~

= = ~ ~ ~

= ~

0.3 0.2 0.3 0.2 0.5 0.5 0.3 0.3 0.3 0.5 0.5 0.5

as a food additive. In Japan, however, tamarind seed gum has been used for many years as a food additive or ingredient and is now used widely in many food applications as listed in Table 2. 2

A. Jams and Jellies One of the more important characteristics of tamarind seed gum is its ability to form jellies with concentrated sugar solutions over a wide pH range. Thus it has been used as a substitute for fruit pectin in jam, jelly, and preserve products. 5 Early work comparing tamarind seed gum and pectin in such applications reported advantages of tamarind gum. Much less tamarind gum (about half) is required to form a fruit gel of equal gel strength to a pectin gel. In addition, tamarind gum can form gels over a wide pH range (approximately 2 to IO), whereas pectin can only gel within a comparatively short acid pH range. Another

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advantage is that tamarind seed gum is not affected by boiling in neutral aqueous solutions, whereas pectins undergo severe degradation on boiling under such conditions. Both tamarind seed gum and pectins are readily degraded by treatment with hot acids or hot alkalis. 5 B. Confectionery Tamarind seed polysaccharide or gum has been used in the preparation of jelly candies and related confections such as jujubes. Conventional methods are used wherein the hot jelly solutions are poured into starch molds and allowed to set. The molded pieces are then further dried to a desirable moisture content, rolled in sugar to form a surface coating of sugar, and then packaged. 5 ·8 C. Salad Dressings and Mayonnaise Tamarind seed gum is reported to be comparable to other gums such as tragacanth, arabic, and karaya in stabilizing oil emulsions (by reduction of interfacial tension) . 17 It has thus been used as an emulsion stabilizer in mayonnaise and similar food emulsion products. 9 - 1 1 The emulsion stabilizing properties of tamarind seed gum in oil-in-water emulsions can be improved by combining it with xanthan gum in approximately equal proportions. 18 Comparative studies by Tanaka and Fukuda 22 compared tamarind seed extract favorably with pectin, tragacanth, and guar gums in the stabilization of French-style salad dressings. D. Frozen Desserts Tamarind seed polysaccharide alone or in combination with carrageenan, sodium alginate, or low-methoxy pectin is a very effective stabilizer in frozen dessert products such as ice cream, ice milk , sherbet, and water ice. 9 J 6 It has been reported to give good overrun, no wheying-off, excellent heat shock resistance, and good water-holding properties without the separation of ice crystals and sugar after long storage. 16 Wada et al. 19 employed a blend of tamarind seed gum (4 parts) and tara gum (I part) at 3% levels as a stabilizer for producing a smooth, shape-retaining, heat shock resistant sherbet. E. Miscellaneous Tamarind seed gum has been used to provide adhesiveness in protective coatings based on casein and starch hydrolyzates for preserving eggs and similar products. 20 It has been employed as a thickening agent in an improved kneaded dough, bread production system. 21 In Japan; tamarind seed gum is also used as a thickening agent in condiments such as ketchup, soy sauce, and pickled seaweeds. It is also utilized in specialized pasta products such as Ramen noodles.

REFERENCES I. Gerard, T., Tamarind gum. in Handbook of Water.Soluble Gums and Resins. Davidson . R. L.. Ed .. McGraw-Hill. New York. 1980. chap. 23. 2. Dainippon Pharmaceutical Co.. Inc.. Glyloid (Tamarind Seed Polysaccharide) Bulletin. Dainippon Pharmaceutical Co. , Ltd .. Osaka. Japan. 1982. 3. Dainippon Pharmaceutical Co.. Inc .. How to Use Glyloid in Food Applications. Dainippon Pharmaceutical Co.. Ltd., Osaka. Japan. 1982. 4. Dainippon Pharmaceutical Co.. Inc .. Tamarind seed polysaccharide feeding study. J. Toxicol. Sci .. 3. 163--192. 1978. 5 . Rao, P. S. and Srivastava, H. C., Tamarind. in lndus1rial Gums , 2nd ed .. Whistler. R. L. . Ed .. Academic Press. New York. 1973. 369-411 . 6. Rao, P. S., Tamarind. in Industrial Gums, Isl ed.. Whistler. R. L. and BeMiller. J .. Eds .. Academic Press. New York. 1959. 461-504.

202

Food Hydrocolloids

7. Hooper, D., Axric. Ll!dger. 2. 13. 1907 (see Reference 5). 8. Rao, P. S., R l!sl!arch /11dill. 4. 173. 1959. 9. Shoji, 0., Wada, K., Tamura, A., and Wada, K., Frozen Desserts . U.S. Palent 3.342.608 . 1967; Chem . Absrr.. 68. 2121. 1968. 10. Savur, G. R., Indian Food Packer. 9 (7). 15. 1955 . 11. Savur, G. R., U1iliza1ion of tamarind seed polyose in food indus1ries. lndia11 Food Padil!f. 9 (2). 13. 1955 . 12. Meer Corp.. Tamarind Seed Gum brochure . 13. Srivastava, H. C. and Singh, P. P., S1ructure of 1he polysaccharide from 1amarind kernel. Carbohydr. Res.. 4. 326-342. 1967. 14. Gordon, A. L., Tamarind Seed Polysaccharide Recovery. U.S . Pa1ent 3.399.189. 1968; Chem. Absrr .. 69 . 97856u. 1968. 15. Dainippon Pharmaceutical Co .. Lid .. Jellose from Tamarind Seed. British Pa1ent 1.007 .303. 1965; Chem. Ab.Hr.. 63. l7809e. 1965 . 16. Shoji, 0., Wada. K., Tamura, A., and Wada, K., Frozen Desserts. U.S. Pa1ent 3.342.608. 1967. 17. Patel, R. P. and Raghunathan , lndia11 J. Phann .. 21. 159. 1959. 18. Kyu.Pi Co., Stabilization of Food Emulsions. Japanese Pa1en1 82-91.172 . 1982; Chem. Absrr.. 71. 12601 la. 1982 . 19. Wada, K., Wada, K., and Deguchi, K., Method for Improving 1he Quality of Food and Drink. Japanese Patent 48-35463 . 1973. 20. Matsutani Kagaku Ko. Coaling Composi1ions for Preserving Foods. Japanese Patent 51-56.580. 1981. 21. Atsumi, S., Sasaki, M., and Kitamura, I., Me1hod for Producing Bread. U.S. Patent 4.405.648. 1983 . 22. Tanaka, M. and Fukuda, H., Studies on the tex1ure of salad dressings containing xanthan gum. Can . Inst . Food Sci. Technol.. 9(3). 130-134. 1976. 23. Yin, R. I. and Lewis, J. G., Novel Blend of Algin. TKP and Guar Gum . U.S. Patent 4.257.816. 1981. 24. Whistler, R. L., Polysaccharides. in Encyclopedia of Polymer Science and Technology , 11. 415. 1969. 25. Cottrell, I. W. and Baird, J. K., Gums. in Kirk-Othmer's Encyclopedia of Chemical Technology. 3rd ed .. Vol. 12. John Wiley & Sons. New York. 1980. 59--00.

PZant Extracts

DOI: 10.1201/9780429290459-13

@ Taylor & Francis a

1

Taylor & Francis Group http://taylorandfrancis.com

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205

Chapter 9

PECTINS Steen ffffjgaard Christensen

TABLE OF CONTENTS I.

Background ..................................................................... 206 A. Introduction ................................................ . ............ 206 B. Origin ................................................................... 206 C. Nomenclature.......... . .................................... . ............ 206

II.

Description ..................................................................... ,207 A. Classification of Commercial Pectins .................................... 207 B. Specifications............................................................ 209 C. Standardization .......................................................... 211

III.

Regulatory Status ......................... . ..................................... 211 A. Physiological Properties ................................................. 211 B. Acceptable Daily Intake ................................................. 212 C. U.S. Food and Drug Administration Regulation ................... . ..... 212 D. Regulations Outside the U.S ............................................. 212

IV.

Manufacture ............................... . .................................... 212 A. Raw Material. ........................................... . ............... 212 B. Extraction ............................................................... 213 C. Purification .............................................................. 213 D. Isolation ................................................................. 213 E. De-Esterification ........................................................ 214 F. Pectin Manufacturers .................................................... 215

V.

Structure ........................................................................ 216 A. Conformation and Structural Randomness ............................... 216 B. Molecular Weight ....................................................... 217

VI.

Properties ....................................................................... 218 A. Powder Properties and Solubility ........................................ 218 B. Solution Properties ...................................................... 219 C. Gel Formation of High-Ester Pectin ..................................... 220 D. Gel Formation of Low-Ester Pectin ..................................... 221 •

VII.

Food A. B. C. D. E. F. G.

Applications .............................................................. 223 Function in Foods ....................................................... 223 Jams, Jellies, and Preserves ............................................. 223 Bakery Fillings and Glazings ............................................ 224 Fruit Preparations ....................................................... 226 Fruit Beverages and Sauces ............................................. 226 Confectionery Products .................................................. 226 Dairy Products .......................................................... 226

DOI: 10.1201/9780429290459-14

206

Food Hydrocolloids H.

Miscellaneous ............. .... . . .. .. . . . . ....... ... . .... . . . ....... .. . .. . . 227

References .......... ........ .. ..... .................. ... ... . . . .. ... .. .. ........... .... .. 227

I. BACKGROUND A. Introduction Pectin is the designation for a group of valuable polysaccharides extracted from edible plant material and used extensively as gelling agents and stabilizers by the food industry . The world production of pectin in 1982 is estimated to amount close to 16,000 metric tons. Main application field is traditionally fruit-based products. especially jams and jellies. where pectin is used as a gelling agent. Unlike most other food hydrocolloids, pectin shows optimum heat stability at acidic conditions and is therefore a potential candidate whenever a texturizer or stabilizer is required in an acidic food product. Increasing amounts of pectin have accordingly found application outside the fruit processing industry. Some I000 metric tons are today used in confectionery products and as stabilizers for acidic milk drinks. and new application possibilities are constantly being investigated and developed. A considerable amount of pectin is further used outside the food industry primarily for pharmaceutical purposes. The word pectin stems from the Greek phrase 'ITTJXTO::. 12

B. Origin Like starch and cellulose. pectin is a structural carbohydrate product present in all plants . Pectic substances are integral components of the cell structures and play an important role as cementing material in the middle lamellae of primary cell walls . Pectic substances are abundant in fruits and vegetables and to a large extent responsible for firmness and form retention of their tissue . The process of ripening and maturing involves enzymatic hydrolysis and depolymerization of the parent pectic substances. partly to yield soluble pectins.

C. Nomenclature

Pectin and pectic substances are heteropolysaccharides mainly consisting of galacturonic acid and galacturonic acid methyl ester residues. In the early days of pectin research. a great deal of confusion regarding pectin terminology was created by the various investigators in the field. In 1944. the American Chemical Society adopted a "Revised Nomenclature of the Pectic Substances •' , which is still used by many scientists as a standard pectin terminology. iJ These uniform definitions are as follows:

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Pectic substances are those complex colloidal carbohydrate derivatives that occur in or are prepared from plants and contain a large proportion of anhydrogalacturonic acid units, which are thought to exist in a chain-like combination. The carboxyl groups of polygalacturonic acids may be partly esterified by methyl groups and partly or completely neutralized by one or more bases. Protopectin is the water-insoluble parent pectin substance that occurs in plants and which on restricted hydrolysis yields pectin or pectinic acids. Pectinic acids are the colloidal polygalacturonic acids containing more than a negligible proportion of methyl ester groups. Pectinic acids, under suitable conditions, are capable of forming gels in water with sugar and acid, or, if suitably low in methoxyl content, with certain ions. The salts of pectinic acids are either normal or acid pectinates. Pectin (or pectins) are those water-soluble pectinic acids of varying methyl ester content and degree of neutralization which are capable of forming gels with sugar and acid under suitable conditions. Pectic acid is a term applied to pectic substances composed mostly of colloidal polygalacturonic acids and essentially free from methyl ester groups. The salts of pectic acids are either normal or acid pectates. Protopectinase is the enzyme that converts protopectin into a soluble product. It has also been called "pectosinase" and "propectinase". Pectinesterase (PE), or pectinmethylesterase, is the enzyme that catalyzes the hydrolysis of the ester bonds of pectic substances to yield methanol and pectic acid. The name ·'pectase'' does not indicate the nature of the enzyme action and has given way to these more specific names. Polygalacturonase (PG), or pectin polygalacturonase, is the enzyme that catalyzes the hydrolysis of glycosidic bonds between de-esterified galacturonide residues in pectic substances. "Pectinase" is frequently used to designate the glycosidase as well as pectic enzyme mixtures.

Due to increasing commercialization of pectinic acids with a low methyl ester content and partly amidated pectinic acids for use in various food products, a modified definition of the food additive, pectin, has been adopted recently by the food industry and food legislative authorities. The following definition complies with contemporary food legislation in most countries:

•

Pectin is a complex, high molecular weight polysaccharide mainly consisting of the partial methyl esters of polygalacturonic acid and their sodium, potassium. and ammonium salts. In some types (amidated pectins) galacturonamide units further occur in the polysaccharide chain. The product is obtained by aqueous extraction of appropriate edible plant material, usually citrus fruits and apples.

II. DESCRIPTION A. Classification of Commercial Pectins Commercial pectin is generally obtained by dilute-acid extraction of citrus albedo or apple pomace followed by various purification and isolation processes. The product usually occurs as a practically odorless, off-white to yellowish white coarse to fine powder having a mucilaginous taste. For practical purposes, the pectin molecule can be considered as an unbranched chain containing 200 to IO00 galacturonic acid units linked together by a-1,4-glucosidic bonds. Some of the galacturonic acid units in the molecule are esterified and present as galacturonic acid methyl esters. Remaining acid groups may be partly or fully neutralized to form ammonia, potassium, or sodium salts (Figure I).

Food Hydrocolloids

208

OH

COOH

COOCH3

J-----0

J-----0

OH

H

H

D-Galacturonic acid

-o: OH ~ COOCH3

0

H

FIGURE 2.

FIGURE I.

H

OH

D-Galacturonic acid methyl ester Principal units in the pectin molecule.

Oo:OOH o OHO o:H OH O HHO H ~:Oo:OOH OH H H ~ O, H

H OH

COOCH3

0

H

H

H OH

COOCH:,

0

H

Section of a high-ester pectin molecule with a degree of esterification ""'-60%.

The degree of esterification is defined as the ratio of esterified galacturonic acid units to total galacturonic acid units in the molecule. High-ester pectins - often called HM-pectins or high methoxyl pectins - are pectins with a degree of esterification above 50% (Figure 2). High-ester pectins require a minimum content of sugar (a soluble solid above approximately 55%) and acid (a pH around 3.0) in order to form gels. Once formed, the high-ester pectin gel cannot be remelted by heating. The degree of esterification of high-ester pectins determines their relative gelling rate. Pectins with a degree of esterification in the range 70 to 75% are often referred to as rapid set high ester pectins while the designation slow set is used for pectins with a degree of esterification in the range 55 to 65%. Ultrarapid set-, medium set-, and extra slow set- are prefixes sometimes used to characterize marginal or intermediate high-ester pectin types. Low-ester pectins (LM-pectins or low methoxyl pectins) are pectins with a degree of esterification below 50%. Commercial low-ester pectins are generally produced from plant material containing high-ester pectin. The transformation (de-esterification) of high-ester pectin accordingly takes place at controlled conditions during the manufacturing process by treatment at either mildly acidic or alkaline conditions. If ammonia is used for the alkaline de-esterification process, a so-called amidated low-ester pectin will result. Apart from galacturonic acids and galacturonic acid methyl esters, amidated low-ester pectins contain galacturonamide units in the molecular chain (Figure 3). The gelling mechanism of low-ester pectins differs essentially from that of high-ester pectins. To obtain gel formation in a system containing low-ester pectin, the presence of calcium ions is crucial. Low-ester pectins may, on the other hand, form gels at much lower solids than high-ester pectins and larger variations of pH are tolerated without major effect on the gel formation. Unlike high-ester pectin, low ester pectin gels may further melt when heated. Amidated low-ester pectins are usually able to jellify preserves, jams, and jellies at the calcium level as is (i.e., with calcium ions originating from fruit and water). Nonamidated low-ester pectins generally require a higher calcium level and addition of "extra" calcium is very often necessary to obtain proper gel formation (Figure 4). Degree of esterification and degree of amidation together control the readiness with which a specific low-ester pectin will react with calcium to form a gel. Nonamidated low-ester

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FIGURE 3. -20%.

209

Section of a low-ester pectin molecule with a degree of esterification ""40% and a degree of amidation

.s::. ....

Ol C

....... Cl)

Ill

Cl)

Ol

E ::, E

50 ~-+--+-:;,.;,.;.+-,.~+-,-,;,-.,+;::,;..-e..,.,_,_,.,.,.,.,..,..,,.,.,.,.,-.+---+---t

X

IO

...

E 0

o\O

10

20 30 40 mg calcium per g pectin

50

FIGURE 4. Typical calcium requirement for amidated (-) and nonamidated (-) low-ester pectins. Shaded area indicates range of "natural" calcium usually found in preserves, jams, and jellies.

pectins with a degree of esterification in the range 25 to 35% and amidated low-ester pectins with a degree of esterification in the range 20 to 30% and a degree of amidation of 18 to 25% are usually characterized as highly calcium reactive or rapid setting and find application in systems with a low calcium content or at low soluble solids. Nonamidated low-ester pectins with a degree of esterification in the range 35 to 45% and amidated low-ester pectins with a degree of esterification in the range 30 to 40% and a degree of amidation of 10 to 18% are less calcium reactive, slow set types, and mainly used in systems with a high calcium content or at relatively high soluble solids (Table 1). Pectins as extracted vary in respect of functional properties and commercial products are therefore most often diluted with sucrose or dextrose for standardization purposes to produce, for example "150 USA-SAG jelly grade" high-ester pectin for use in jams and jellies, or "100 gel power" low-ester pectin for use in products with a reduced sugar content. In addition to sugars, suitable food grade buffer salts may be added for pH control and to achieve desirable setting characteristics. B. Specifications Commercial pectins for food applications must generally meet internationally accepted specifications as per the following three publications: (I) FAO Food and Nutrition Paper -

210

Food Hydrocolloids

Table I MAIN COMMERCIAL PECTIN TYPES

Pectin type

High ester High ester High ester High ester High ester Low ester Low ester Amidated low ester Amidated low ester

Setting rate designation

Calcium reactivity

Ultra rapid set Rapid set Medium set Slow set Extra slow set Slow set Rapid set Slow set Rapid set

Not relevant Not relevant Not relevant Not relevant Not relevant Low High Low High

Typical degree of esterification (%)

Typical degree of amidation (%)

76

0 0 0 0 0 0 0 15 20

72

68 62 58 40 30 35 30

Table 2 OFF1CIAL PURITY SPECIFICATIONS FOR COMMERCIAL PECTINS Reference

Loss on drying (volatile matter) Acid-insoluble ash Ash (total) Sulfur dioxide Sodium methyl sulfate Methanol, ethanol, and isopropanol Nitrogen content, amidated pectin Nitrogen content, nonamidated pectin Galacturonic acid Total anhydrogalacturonides in peetin component Degree of amidation, amidated pectin Degree of esterification of high-ester pectin component Degree of esterification of low-ester pectin component Arsenic, ppm Lead, ppm Copper, ppm Zinc, ppm Copper + zinc, ppm Heavy metals (as Pb), ppm

14 (FAO)

max 12% maxi% max 50 mg/kg max 1% max 2.5% max 0.5% min 65% max 25%

15 (FCC)

max 12% max 1% max 10% max 0.1%

min 70% max 40%

16 (EEC)

max 12% max 1% max 50 mg/kg max 1% max 2.5% max 0.5% min 65% max 25%

min 50% max 50% max max max max

3 IO 50 25

max 3 max IO

max 40

max 3 max IO max 25 max 50

19, 14 (2) Food Chemicals Codex, 3rd ed., 15 (3) EEC Council Directive of July 25, 1978. 16 The specifications mainly deal with the identity and purity of the product. A summary of the official purity specifications for pectins intended for use within the food industry is shown schematically in Table 2. Apart from chemical.purity, most pectin manufacturers specify the microbiological purity of their product. As pectin is an acid polysaccharide finding use mainly in acidic media, yeast and mold counts are especially relevant for the user. Typical microbiological specifications may read as follows: Total plate count (37°C) Yeast and mold count (25°C)

Less than 500/g Less than 10/g

Volume Ill E. coli Salmonella Staphy lococci

211

Test result negative Test result negative Test result negati ve

Pectins used within the pharmaceutical industry must comply with the specifications for identity and purity in the U.S. Pharmacopeia. 17-:.' 9

C. Standardization

To meet the users ' requirement to obtain a pectin with constant properties , most commercial pectins are standardized . High-ester pectins used for jams and jellies are generally Stand~ ardized to uniform gel strength and setting rate at specified constant conditions. Gel strength standardization is achieved by addition of sucrose or dextrose (ingredients used extensively in all regular jams and jellies) and often expressed as jelly grades . 20 The " USA-SAG method " based on the work by Cox and Higby and adopted in 1959 2 for grading high= method common most the today is ' by the Institute of Food Technologists part of pectin is I that implies USA-SAG 150° of ester pectins. A jelly grade designation conditions standardized under prepared jelly a into sucrose of parts able to transform 150 : follows as and with standard properties I. 2. 3.

Refractometer soluble solids: 65% pH: 2.20 to 2.40. Gel strength: 23 .5% SAG over 2 min of a gel cast in and removed from a standard glass with exactly specified inner dimensions .

Other methods for grading pectin d iffer from the USA-SAG method in terms of test jelly preparation, properties, and evaluation. Grade specifications on basis of different methods are not readily comparable or correlated. 22 The setting rate of high-ester pectins may be standardized according to a method developed by Joseph and Baier.23 The properties of the test jelly specified are exactly the same as used by the USA-SAG test , and the same jelly batch may in fact be utilized for both determinations. The jelly is exposed to a standard cooling procedure, obtained by placing a USA-SAG standard glass with freshly prepared jelly in a constant temperature (30°C) water bath. The time taken for the jelly to set is measured and typical results obtained for rapid and slow set high-ester pectins are 50 and 225 sec, respectively . The setting temperature of pectins is sometimes specified and may, in many cases, prove more useful for practical purposes than a setting rate designation , especially if test jelly composition and cooling rate are comparable with actual application conditions . Setting temperature is generally defined as the temperature at which the first sign of jellification can be observed either visually as described by Hinton 24 or by measuring changes in viscoelastic properties or cooling rate. Gel power of low-ester pectins may be standardized by procedures similar to the USASAG method for grading high-ester pectins. 25 However, the idea of standardizing low-ester pectins according to jelly grade has not gained any broad acceptance. Unlike high-ester pectins , low-ester pectins are used in a great variety of products differing in respect of soluble solids content , calcium level , pH , and other factors influencing gel strength performance of the pectin . Market preferences today seem to point towards a variety of lowester pectin types, each standardized by specific performance tests in systems relevant for the intended application.

III. REGULATORY STATUS A. Physiological Properties

As a constituent in all land plants, pectin has always been consumed in significant quantities

212

Food Hydrocolloids

by man. Pectolytic enzymes are found in plants and excreted by many microorganisms . Man, however, possesses no enzyme system to degrade pectin, and it therefore passes unchanged to the large intestine, where bacteria are able to use pectin as their carbohydrate source. Although pectin is hydrolyzed in the intestinal tract. it has no, or only insignificant, net calorie value. 26

B. Acceptable Daily Intake Pectins and amidated pectins were evaluated by the "Joint FAO/WHO Expert Committee on Food Additives'' (JECFA) in 1981 . 27 The committee found that there were no toxicological differences between pectins and amidated pectins, and consequently it was deemed unnec. essary to retain the previously established preliminary ADI-value for amidated pectins . A group of ADI "not specified" was established for pectins and amidated pectins, meaning that from a toxicological point of view there are no limitations for the use of pectins, whether amidated or not. C. U.S. Food and Drug Administration Regulation Pectins are affirmed "generally recognized as safe" for use in human foods under 21 CFR 184.1558. 2 " This affirmation became effective in 1983 and states that pectin is generally recognized as safe for food use when: I. 2. 3.

It meets the specifications of the Food Chemicals Codex, 3rd ed. 15 It is used as an emulsifier, stabilizer, or thickener. The levels do not exceed current good manufacturing practice.

In accordance with present practice for "substances whose use has been shown to be safe under reasonably foreseeable conditions of use", the Food and Drug Administration has, besides "good manufacturing practice" not issued any specific limits or guidelines for use levels of pectin in any food.

D. Regulations Outside the U.S. According to the Canadian Food and Drug Act, the use of pectin is permitted in jams, jellies, and marmalades; in relishes and salad dressings; in certain milk and meat products: and in unstandardized foods at levels only limited by good manufacturing practice. It is further permitted at maximum use level of 0.5% in ice cream products and sour cream and at O. 75 % in sherbet. 29 Food legislation in the member states of the European Economic Community at present distinguishes between pectin (E 440 a) and amidated pectin (E 440 b). Apart from certain limitations regarding the use of amidated pectin in Italy and the Federal Republic of Germany, food regulations in the individual member states generally allow the use of pectin in food products, when a technological need can be proven, at use levels corresponding to "good manufacturing practice." In most other countries, food legislative authorities recognize pectin as a valuable and harmless food additive. If regulated, permitted use levels are generally in accordance with "good manufacturing practice".

IV. MANUFACTURE A. Raw Material Apple pomace and especially citrus peel are the only raw materials of any significance for commercial pectin production. Both products are available in ample supply as a residue from juice production and have a high content of pectin with desirable properties, which can be liberated by a relatively simple extraction process. A number of other surplus materials

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213

of vegetable origin (e.g., sunflower bottoms and sugar beet waste) have been suggested as basis for pectin manufacture, but apart from a small production of beet pectin in the USSR, none of these alternative sources are utilized today. 30 Pretreatment of the citrus peel for pectin production involves blanching and washing to terminate pectinesterase activity and remove glucosides, sugars, and citric acid. The peel may further be dried to attain storage stability and allow transportation over longer distances. Dried citrus peel generally contains 20 to 30% pectin. Apple pomace is normally dried immediately after the juice pressing. Yeast exudates pectolytic enzymes and any fermentation of the fresh apple pomace would rapidly degrade the pectin contained. Dried apple pomace generally yields JO to 15% pectin.

B. Extraction To solubilize and liberate the pectin, the raw material - fresh or dried - is added to acidified water (pH usually 1.5 to 3.0). The acid used is most often hydrochloric acid or nitric acid, but sulfuric acid or sulfur dioxide may also come into question. At the extraction conditions, a certain de-esterification of the pectin will take place, To arrive at the desired degree of esterification at the end of the extraction process, pH, temperature, and time must be controlled carefully. Rapid set high-ester pectins are generally extracted at temperatures close to the boiling point. The high temperature accelerates hydrolysis of the parent pectic substances, lowers viscosity, and facilitates diffusion. Accordingly, the extraction procedure may be finished in less than I hr with only minor deesterification of the pectin taking place. Lower extraction temperature and longer extraction time favors the de-esterification process, yielding slow set high-ester pectins or even lowester pectins. C. Purification The raw extract is a viscous liquid containing 0.3 to 1.5% dissolved pectin and the peel or pomace residue in a more or less swollen and disintegrated state. The separation of the residue from the extract presents one of the key problems in pectin manufacture. Usually, more separation processes, filtrations with various types of filter aid and centrifugations, are necessary to obtain a clear extract. At this stage, the pectin may be further de-esterified by holding at controlled pH and temperature, and the extract may be concentrated by evaporation. Minor quantities of pectin are simply sold as the concentrated extract. This "liquid pectin" is normally preserved with sulfur dioxide and delivered in barrels or by tank car. D. Isolation The pectin may be isolated in its pure form either by precipitation with alcohol or by precipitation as an insoluble salt by addition of suitable cations, usually aluminum. A simple drum drying of the concentrated pectin extract leads to a commercial product containing all extracted impurities and is hardly used anywhere today. Alcohol precipitation is obtained by mixing the extract with methanol, ethanol, or 2propanol. The gelatinous precipitate obtained is washed with alcohol and pressed to remove soluble impurities, and finally dried and milled to yield powdered pectin. Aluminum precipitation involves addition of a concentrated solution of either aluminum sulfate or aluminum chloride, together with alkali (for pH-control) to the purified extract. By this procedure, pectin is isolated as a co-precipitate with aluminum hydroxide. To obtain a pure pectin, it is necessary first to wash the precipitate with acidified alcohol to remove aluminum, and second, to wash with alkaline alcohol to neutralize the product. Pressing, drying, and milling to obtain a powdered pectin finalize the process. The various production methods and production steps in high-ester pectin manufacture are shown in a condensed form in Figure 5.

214

Food Hydrocolloids

CITRUS PEEL OR APPLE POMACE

EXTRACTION (DE-ES TERI Fl CATION)

PEEL OR POMACE RESIDUE

FILTRATION

DE-ESTERIFICATION

PURIFIED EXTRACT

CONCENTRATION

+

PRECIPITATION WITH ALUMINIUM

PRECIPITATION WITH ALCOHOL

WASH WITH ACIDIFIED ALCOHOL

WASH WITH ALCOHOL

I-I

"LIQUID PECTIN"

I

WASH WITH

ALKALI NE ALCOHOL PRESSING

1 l 1

DRYING

MILLING

HIGH ESTER PECTIN

FIGURE 5 .

Principal production methods for high-ester pectins.

E. De-Esterification The de-esterification of the extracted pectin required to produce low-ester pectin types may, as explained before, take place during extraction or in the purified extract. However, to avoid undesired depolymerization, it is often preferred to postpone the de-esterification till the pectin has been precipitated. The precipitate is dispersed in alcohol and either acid or alkali is added to obtain the desired reaction. If the base used is ammonia, a certain amidation in addition to the de-esterification will take place . The use of specific microbial pectin esterases for the production of low-ester pectins has been suggested. 31 Unlike pectin esterases of vegetable origin, certain microbial pectin esterases will lead to a random distribution pattern of free carboxyl groups, similar to that obtained by acid- or alkali-induced de-esterification. 32 The idea is, however, hardly economic for any industrial utilization at present. Flow diagrams showing various production methods for low-ester pectins are presented in Figure 6.

Volume l/1 CITRUS PEEL OR APPLE POMACE

215

EXTRACTION (OE-ESTERIFICATION)

PEEL OR POMACE RESIDUE

FILTRATION

DE-ES TERI Fl CATION

PURIFIED (CONCENTRATED) EXTRACT

PRECIPITATION WITH ALUMINIUM OR ALCOHOL

i

.___ _ _ _P_R_E_S~S_I_N_G_ _ _

r i l

_,I

WASH WITH ALCOHOL

__,I I. ._____P_R_E_S~S_IN_G_ _ _ _____.

r i _,I I. . _____ l

~----D_R_Y_I_N_G_ _ _ ___.I

.___ _ _ _M_I_L~L_IN_G_ _ _ _

IAMIDATED LOW ESTER PECTIN'

FIGURE 6.

PRECIPITATION WITH ALUMINIUM OR ALCOHOL

DE-ESTERI Fl CATION WITH ACID OR BASE IN ALCOHOL

DE-ESTERIFICATION WITH AMMONIA IN ALCOHOL

.____w_A_s_H_w_1_T~H_A_L_co_H_o_L_

PURIFIED (CONCENTRATED) EXTRACT

D_R_Y_IN_G _ _ _ _ __.

-1_ _ _ _ _

M_I_L_L_IN_G_ _ _ __.

LOW ESTER PECTIN

Principal production methods for low-ester pectins.

F. Pectin Manufacturers Pectin production originally sprang up in citrus- or apple-growing and processing areas, where fresh raw material was abundant. Today, however, a number of major producers have grown to a size where production, wholly or partly, must be based on imported dried citrus peel. Hercules, Inc., Wilmington, Del., is the largest pectin producer at present, owning pectin factories in Denmark (The Copenhagen Pectin Factory Ltd.), Germany (Pomosin AG), Italy (Cesalpinia S.P.A.), and since 1980 also producing domestically in Florida. Other large producers are Unipectine S.A. in France, HP Bulmer Limited in England, Pektin-Fabrik Hermann Herbstreith KG in Germany, Atlantic Gelatin Plant, General Foods Corp., Mas~ sachusetts, and Pectina de Mexico S.A. (owned by Grindsted Products Ltd.) in Mexico. Smaller pectin manufacturers are found in Switzerland, Brazil, Israel, Argentina, and in a number of East European countries.

216

Food Hydrocolloids

V. STRUCTURE A. Conformation and Structural Randomness As a complex heteropolysaccharide with varying composition according to origin and extraction conditions, pectin cannot be characterized in terms of a specific overall structure and conformation. It is, however, possible to recognize distinctive structural elements contained in all pectin material. Functional properties, especially gel formation and rheological phenomena, involving interactions between more molecules, depend on the presence of specific structural regions in the pectin molecular chains. Small variations in composition may cause spatial and conformative changes which totally invalidates the functional properties of the product. Pectins extracted from sugar beets and potatoes contain a high proportion of galacturonic acid units in which the hydroxyl groups at position C-2 and C-3 are esterified with acetate. As a result, sugar beet and potato pectin do not form gels at all, unless the acetate groups have been removed chemically or enzymatically. Depending on origin, extraction procedure, and preparation, hydrolysates of pectin always contain varying amounts of neutral sugars, especially o-galactose, L-rhamnose, and L-arabinose. 33 ·34 The neutral sugars are to a large extent constituents in side chains to the polygalacturonan backbone, a remainder from the complex protopectin structure, but 1,2-linked L-rhamnose will also be present in the main polygalacturonic chain. Rhamnose insertions will provide "kinks" in the molecular chain, a basic structural condition of a molecular gel network formation. 35 A comprehensive understanding of pectin structures and the consequences regarding conformative and interactive aspects has, by far, not been reached yet. Prevailing models concerning fundamental structure elements are even contradictive in certain ways. Different findings may to a large extent reflect the heterogeneity of the product and stem from variations in raw material and preparative methods. X-ray diffraction studies on dried fibers indicate that the galacturonan backbone forms a right-handed helix, with 3 galacturonic acid units in C, conformation as the repeating sequence, corresponding to a repeat distance of 13.4 A. 3&::.3s The 3 1 helical structure is stabilized by intramolecular hydrogen bonds to form a fairly stiff rod-like structure, which may be interrupted by irregularities in the molecule as, for example, rhamnose insertions (Figure 7). From circular dichroism and equilibrium dialysis investigations concerning calcium binding to poly-o-galacturonate and low ester pectins, Morris et al. 39 Ao have suggested that gel formation with calcium involves polygalacturonic acid sequences with a 2 1 , ribbon-like symmetry. On drying the gel, however, the 3 1 helical symmetry is restored through a polymorphic phase transition. Distribution of free carboxyl groups along the pectin molecules and the distribution of molecules with different degree of esterification within a specific pectin preparation has been investigated by various techniques. 41 -4 8 Enzymatic de-esterification in vivo tends to produce pectins with free carboxyl groups occurring in blocks and a large variation in degree of esterification among the contained pectin molecules. De-esterification in vitro with acid or alkali leads to a random distribution of free carboxyl groups and relatively small variations in degree of esterification between the individual pectin molecules. Accordingly, commercial pectins normally show a free carboxyl group distribution pattern in between the two, determined by extent of in vivo de-esterification in the raw material and subsequent in vitro de-esterification during the manufacturing process. Compared with pectin preparations extracted at mild conditions, commercial pectins generally contain lower quantities of neutral sugars. This can be explained as a result of acid hydrolysis of neutral sugar side chains during the industrial extraction process. Accordingly, a large part of the neutral sugars left in commercial pectins is I ,2 bound rhamnose present in the galacturonan backbone. Distribution of rhamnose insertions along the pectin molecular chains has not been fully elucidated at present. Partial acid hydrolysis of pectins of various origin tend to produce

Volume II/

217

0

o+

0

13,4

A

oG

GO

+')

0

0

..

7.*0~

+0

.o

0

"o

OC',s, .;J

\

FIGURE 7. CI conformation of the a-o-galacturonic acid methyl ester residue and model of the polygalacturonan chain showing 3, helical structure with a repeating unit distance of 13.4A.

galacturonan segments of fairly constant size corresponding to 25 units. As the glucosidic bond betwen C 1 in rhamnose and C4 in galacturonic acid is considered less acid stable than other glucosidic bonds in the molecule, Powell et al. 40 have suggested that the length of polygalacturonate sequences between rhamnose interruptions is fairly constant and corresponding to approximately 25 residues. (Figure 8 A.) Neukom et aL 49 have analyzed similar sequences with a degree of polymerization of 20 to 30, obtained by acid degradation of apple pectin preparations. Their experiment showed that the oligomers were almost fully made up by galacturonic acid units and only traces of rhamnose were present. They were , on the other hand, also able to isolate galacturonan segments containing rhamnose from apple tissue and concluded that the cell walls contained both a pure galacturonan-type pectin and a rhamnogalacturonan-type pectin, possibly located in different regions. Based on results obtained by specific enzymatic degradation of apple pectins, De Vries et al. 50 •5 ' have suggested a molecular model consisting of a long homogalacturonan chain intercepted by a few relatively short "hairy" regions containing all rhamnose insertions and side chains (Figure 8B). B. Molecular Weight Molecular weight of pectins can be expected to vary with raw material, extraction con-

218

Food Hydrocolloids

A

B ~

a:

C=:J

GALACTURONAN CHAIN RHAMNOSE SIOE CHAIN

FIGURE 8. Contemporary models for occurrence of side chains and rhamnose insertions in the pectin molecule. (A) Even distribution. as suggested by Powell et al:"' (B) Blockwise occurrence in a few hairy regions. as suggested by De Vries et al."'·"

ditions, and isolation procedure. Based on viscosimetry, the average molecular weight of commercial pectin normally falls within the range 50,000 to 150,000 daltons. 42 ·525' Other techniques used for molecular weight determination (e.g., light scattering) often result in apparent molecular weight around I million or even higher. The reason for this inconsistency is a considerable amount of intermolecular association even in fairly dilute solutions leading to aggregates of pectin molecules. 5 4-:57

VI. PROPERTIES A. Powder Properties and Solubility In the manufacturing process, pectins are normally dried to a water content below 10%. As the equilibrium moisture content is 12% in 70% relative humidity, pectin tends to take up moisture in most climates. To avoid caking and ensure optimum storage stability, it is recommended to keep the product in a vapor-tight package at cool and dry conditions. 5 " High-ester pectins will slowly loose gel power and gradually adopt slower setting characteristics due to depolymerization and de-esterification during storage. At a storage temperature of 20°C, a loss of gel power of 5%/year must be expected; at higher storage temperatures, the change in functional properties will take place at a much faster rate. Lowester pectins are considerably more stable than high-ester pectins. When the product is kept at room temperature, it is scarcely possible to detect any loss of functional properties over 1 year. Commercial pectins are typically milled to a particle size corresponding to a 99% pass through a 60 mesh (0.25 mm) sieve. The powder has usually a fairly low density, around 0. 7 g/cm' and a somewhat fibrous structure with powder flow properties inferior to a crystalline product. Pectin is generally soluble in water and insoluble in most organic solvents. Water solubility increases with decreasing molecular weight and increasing degree of ran-

Volume Ill

219

domness of the carboxyl group distribution. Sodium pectinates are generally more soluble than pectinic acids, which in tum are more soluble than calcium pectinates. Pectic acids and pectinic acids with a low degree of esterification are only soluble as the sodium or potassium salt. Increasing amounts of sugar or calcium ions in the water will make the pectin more and more difficult to dissolve. It is accordingly recommended always to dissolve pectin at soluble solids below 25% and preferably in hot water to ensure maximum hydration and disintegration of the large molecular aggregates present in the pectin powder. When added to water, powdered pectin tends to form lumps consisting of pockets of semidry powder enrobed by a shell of hydrated material. These lumps dissolve very slowly, and a rational dissolution process accordingly involves suitable techniques to obtain a perfect dispersion of the powder. Vigorous agitation as obtained with a high-speed mixer may serve to disperse the pectin before any lumps are formed and subsequently dissolve the pectin completely within a few minutes. When hot (.60 to 90°C) water is used, up to I 0% pectin solutions may be made using this technique. However, to avoid handling problems due to too high viscosity, only 5 to 8% solutions are normally produced. Complete dispersion may be obtained with conventional stirrers, if the pectin is dry blended with approximately 5 parts of inert material (most often sucrose) or initally dispersed in media where pectin is insoluble (e.g., alcohol or a concentrated sugar syrup). Dry blending with 2% sodium bicarbonate will further facilitate dispersion as carbon dioxide, developed during the dissolution process by the reaction between bicarbonate and the acidic pectin, will tend to break up any lumps formed.

B. Solution Properties

Pectin solutions show relatively low viscosities compared to other plant hydrocolloids. and pectin consequently has limited use as a thickener. The viscosity increases with increasing degree of polymerization and increasing degree of esterification, but is further affected by the presence of various solutes in the system (Figure 9). Basically, the viscosity of a pectin solution will depend on size and shape of the molecules, but formation of macromolecular aggregates and interactions with electrolytes or water molecules can be expected to affect the flow properties of the solution. In dilute solutions, where interactions between more pectin molecules are negligible, viscosity increases with increasing dissociation of the carboxyl groups and reaches a plateau when almost full dissociation has been obtained. 59 This phenomenon may be interpreted as an increase of the hydrodynamic volume of the molecule caused by repulsion between adjacent charged carboxyl groups. The pK value of pectin is approximately 3.3, and the observed viscosity increase corresponds to a change in pH from 2 to approximately 5. 60 J> 1 The intramolecular repellance of charged carboxyl groups may be counteracted by an increase in ionic strength of the solution. Addition of sodium chloride to a pectin solution has accordingly been shown to lead to a remarkable drop in viscosity. 10 ·59 Viscosity of highester pectin solutions generally increases with increasing degree of esterification. 62 This effect may be explained by an increase in the structuring of water molecules around the methyl ester groups. 38 In the case of low-ester pectins, low degrees of esterification or a blockwise occurrence of carboxyl groups will lead to high viscosities reflecting an inferior solubility of these pectins. Dilute pectin solutions show near to Newtonian flow properties, but these change to pseudoplastic as the pectin concentration is increased. This change in rheological properties indicates an interaction between pectin molecules in more concentrated solutions resulting in an integral structure which can be broken mechanically, but reforms when the shearing action is stopped. Addition of calcium or other divalent cations to pectin solutions leads to the formation of strong intermolecular chelate bonds involving carboxyl groups occurring in sequences of

220

Food Hydrocolloids

100000

High ester pectin - 2s0 c High ester pectin - &oOc

10000

i.

Ic

.

Low ester pectin -

2s0 c

Low ester pectin - 60°c

,ooo

~

~ -; 0

:;:

100

> 10

10

% Pectin in solution

FIGURE 9. Typical viscosity of commercial high-ester and low-ester pectin at 25 and 60°C.

suitable length and the metal cation in question. 63 Addition of calcium to low-ester pectin solutions may even cause formation of a true gel which will not reform after mechanical rupture. Intermolecular interactions leading to aggregation of high-ester pectin molecules are favored by decreasing the charge on the molecules (i.e., by lowering the pH) and by addition of cosolutes, normally sucrose or other carbohydrate sweeteners. Addition of water-soluble alcohols and ketones to pectin solutions causes precipitation of the polymer. Pectin is further precipitated by heavy metals, by quaternary detergents, and by most cationic macromolecules. 64 ·65 High-ester pectin will interact with casein particles in sour milk products to yield a stablilized suspension of casein particles which can be pasteurized without coagulation or precipitation. 66 Application procedures involving holding of pectin solutions at elevated temperatures leads to depolymerization and de-esterification of the pectin. Both processes are mainly governed by the. pH of the solution. Compared to other gelling agents, pectin shows a remarkable stability in the pH range 3 to 4.5. At lower pH values and elevated temperatures, degradation due to hydrolysis of glucosidic bonds is observed. De-esterification is also favored by low pH, and long holding times may cause a high-ester pectin gradually to adopt slower setting characteristics. At pH values above 4.5, high-ester pectin is stable only at room temperature. At elevated temperatures, chain cleavage by 13-elimination rapidly leads to Joss of viscosity and gelling properties (Figure IO). Only glucosidic bonds next to an esterified carboxyl group can be broken by 13-elimination, and low-ester pectins are accordingly considerably more stable at higher pH values than high-ester pectins. This phenomenon explains, for example, why it is possible to UHTST-sterilize milk desserts with low-ester pectin as the gelling agent. C. Gel Formation of High-Ester Pectin Any solution containing high-ester pectin at potential gelling conditions has an upper temperature limit above which gelation will never occur. When cooling the solution below this temperature, gel formation takes place after a certain time. Practical experience shows that the observed gelling temperature and gelling rate mainly depend on the following factors: l.

Degree of esterification - Increase in degree of esterification leads to higher setting temperatures and increased setting rate.

Volume Ill

◊-

OCOOCH30

HOH

---

COOCH

3

0 H

0/

OH

H

H

OH

FIGURE 10.

2.

3.

O O H

H

---o

OH

3

+

H

COOCH

COOCH

H

H

3

221

H

o---

H

H

OH

j.3-elimination.

pH - Reduction of pH leads to increase in gelling temperature and setting rate. Commercial high-ester pectins will generally not form gels at pH values above 4.0, and normal application conditions usually require a pH around 3.0 for proper gel formation. Soluble solids - Increase in sugar content leads to increase in gelling temperature and setting rate. Practical working range for commercial high-ester pectins is between 55 and 80% soluble solids. Below 55% soluble solids, no gel formation is obtained, and at solids above 80%, setting will occur practically at the boiling point of the system.

Polysaccharide gel formation generally involves crosslinking of the polymer to form a three-dimensional network in which water, sugar, and other solutes are held. A model for the junction zones in the high-ester pectin gel network has been suggested by Walkinshaw et al. 38 According to this model, 3 to 10 polymer chain segments with a 3 1 helical structure will form aggregates of parallel chains limited in size because of steric barriers, entropic factors and possible rhamnose insertions. This local crystallization would be sustained by intermolecular hydrogen bonds and probably reinforced by hydrogen bonding with water molecules in one set of triangular channels and hydrophobic attractions between methyl groups forming columns in a second set of triangular channels. (See Figure 11.) Gel formation of high-ester pectin can accordingly be explained as local polymer aggregations made possible by the combined effect of cosolutes (sugars) breaking up the cages of water molecules surrounding the individual polymer chains, a low pH resulting in protonation of carboxyl groups and hence a decrease in electrostatic repulsion between the galacturonan chains, and finally the presence of methyl ester groups lowering total charge of the molecules and actively contributing to the chain interactions. 68 •69 Rheological properties of high-ester pectin gels indicate that at least two types of bonding are involved in the molecular gel network. 70 One type of bond is strong and responsible for the elastic properties of the gel, while the other type of bond is weaker and capable of reforming after disruption. When sucrose as cosolute is substituted by com syrup, a remarkable increase in gelling temperature will occur. This observation indicates that sugars play an active role in the formation of the pectin gel network. Most likely pectin molecules associate with sugar molecules through hydrogen bonds to form secondary links reinforcing the molecular network structure. Gel strength of high-ester pectin gels generally increases with increasing pectin concentration and increasing molecular weight of the pectin. Homogeneity and specific structural characteristics of the pectin material in question plus the preparative method used to produce the gel will further influence the gel strength obtained. High-ester pectin gels are generally cohesive and show no tendency to syneresis. The gels are not temperature reversible, but will slowly dissolve in hot water. D. Gel Formation of Low-Ester Pectin Low-ester pectins form gels in the presence of calcium. and other divalent metal ions. Setting temperature of low-ester pectin gels generally increases with increasing de-esteri-

222

Food Hydrocolloids

f----8.37 A - - - i

FIGURE 11. Model of junction zone in a high-ester pectin gel as suggested by Walkinshaw et al." Parallel polygalacturonan chains, viewed along the helix axis, are packed in a hexagonal lattice. The structure is sustained by intermolecular hydrogen bonds (dotted lines) and reinforced by columns of methyl groups (filled circles).

fication of the pectin, increasing amount of calcium and soluble solids in the system, and increasing amount of possible galacturonamide substitutions in the molecule. Kohn et al. 63 •7 1. 72 have investigated the binding of calcium ions to oligogalacturonates, polygalacturonates, and pectinates. The investigations proved that calcium binding to lowester pectin can not be explained as a simple electrostatic interaction, but involves intermolecular chelate binding of the cation leading to the formation of macromolecular aggregates. The results further indicated that sequences of minimum IO galacturonic acid units in the polymer are required to obtain intermolecular association with calcium ions. Rees 73 ·74 has suggested a so-called "egg-box" model for the primary junction zones in the low-ester pectin molecular gel network. Chain segments of 14 or more residues with a 2, ribbonlike symmetry are believed pairwise to form parallel oriented aggregates. Calcium ions formin~ chelate bonds with oxygen atoms from both galacturonan chains will fit into "cavities" in the structure. (See Figure 12.) The extension of the crystallites will be limited by methyl ester residues and by rhamnose insertions side chains or other irregularities in the chains. Secondary junction zones in the gel network may arise from hydrogen bonding with water and sugar molecules and, if calcium is present in surplus amount, from subsequent calcium induced aggregation of the preformed dimers. The presence of galacturonamide substitutions in the low-ester pectin molecular chain is known to promote gel formation but also to counteract network collapse at higher calcium levels. (See Figure 4.) However, the mechanisms responsible for these modifications of the gel properties have not been elucidated yet. Gel strength of low-ester pectin gels varies with pectin concentration, pH, and calcium content. Optimum gel strength is normally found in the pH range 3.0 to 3.5, but excellent gels may be obtained at higher pH values by increasing pectin dosage or calcium level. Gel strength increases with increasing calcium content, but higher calcium levels lead to brittle

Volume Ill

FIGURE 12.

223

"Egg.box" model of a primary junction zone in a low-ester pectin gel.

gels with syneresis tendency and eventually to disintegration of the structure by extensive crystallization. Optimum calcium content required to produce coherent gels with minimum syneresis tendency depends primarily on degree of esterification of the pectin in question. Quality of commercial low-ester pectins is accordingly closely connected to inter- and intramolecular consistency of the material. Increasing amounts of soluble solids lead to less brittle gel structures and reduced syneresis tendency, but further increase setting temperature of the gel. The increase in setting temperature may be counteracted by selecting low-ester pectin types with a higher degree of esterification or by decreasing the calcium content of the system. Addition of polyphosphates or other calcium complexing agents will also decrease the gelling temperature. Unlike highester pectin gels, low-ester pectin gels weaken with increasing temperature and will usually melt when heated to a temperature 5 to 10°C above the setting temperature.

VII. FOOD APPLICATIONS A. Function in Foods

Pectin is primarily used as a gelling agent in foods. Dependent on pectin type and dosage, and the composition of the food system, textures ranging from soft and thixotropic to firm cohesive or brittle gels can be obtained. Gel formation is most often obtained by cooling the product below the gelling temperature of the system. However, the specific gelling mechanism of pectin also offers the possibility to obtain cold gelation by addition of acid, sugar, or calcium to a food system containing pectin in solution. Gel formation of pectin may be utilized to stabilize multiphase foods, either in the final product or at an intermediate stage in the process. The anionic character of the polymer may, in specific systems, also serve to counteract aggregation of, for example, protein particles. The thickening effect of pectin in terms of pure viscosity increase is utilized mainly where food regulations prevent the use of cheaper gums or where an "all natural" image of a product is essential. The main food applications of pectin are listed in Table 3. Close to 80% of all pectin produced is consumed by the fruit processing industry and the group, jams, jellies, and preserves, is by far the most important application area. For detailed information about formulations and application procedures for the various foods listed, it is recommended to consult commercial handbooks and technical data sheets as published by the pectin manufacturers. 75-::78

B. Jams, Jellies, and Preserves

Pectin is used to impart a texture to jams, jellies, and preserves that allows transportation without changes, gives a good fla.vor release, and minimizes syneresis. During the manu-

224

Food Hydrocolloids

Table 3 FOOD APPLICATIONS OF PECTIN Product group Jams. jellies, and preserves Bakery fillings and glazings Fruit preparations Fruit beverages and sauces Confectionery Dairy products Miscellaneous

Function of pectin Gelling agent, thickener Gelling agent. thickener Thickener. stabilizer Thickener. stabilizer Gelling agent. thickener Stabilizer. gelling agent

Pectin use level (%)

0.1-1.0 0.5-1.5 0.1-1.0 0.01---0.5 0.5-2.5 0.1-1.0

Estimated consumption (metric tons/year)

10,500 500 400 400

2.000 1.100 100

facture of a jam, the pectin must ensure uniform distribution of fruit particles in the continuous jelly phase from the moment the mechanical stirring ceases, i.e., the pectin must set quickly after the filling operation. Regular jams with a refractometer soluble solids content between 65 and 70% are usually made with high-ester pectins. Rapid set pectins are used for products filled into smaller jars at temperatures around 90°C. When filling into larger packages, the filling temperature must be reduced to avoid heat damages of the fruit, as product in the middle of the large pack only cools very slowly, irrespective of outside temperature. To avoid premature gel formation of the pectin, slow set types must accordingly be used for products in larger packages. Slow set pectins are always used for jellies, as the relatively low setting temperature allows ample time for any air bubbles to escape from the product before gel formation starts (Figure 13). Low-ester pectins may be used in jams with solids ranging from 25 to 75%. However, in regular jams and jellies, low-ester pectins are less economic in use than high-ester pectins and generally only used if a soft, spreadable and thixotropic texture is desired. Low sugar jams and fruit spreads are, on the other hand, generally produced with low-ester pectins. Calcium-reactive types find use at lower solids while types with a relatively higher degree of esterification are used at solids around 55%. At soluble solids below 25%, reactive lowester pectins may yield products with an adequate gel texture. When the gel is broken, however, syneresis will cause considerable juice exudation. At low solids, low-ester pectins are accordingly often used in combination with other water-binding hydrocolloids. The amount of added pectin to be used in a jam or jelly depends on desired consistency, amount of added fruit, pectin, or calcium content in the fruit used, soluble solids, heat treatment, and packing size. To obtain a jellified yet spreadable texture of a jam containing 50% fruit and with 65% soluble solids typically 0.2 to 0.3% high-ester pectin :s required. Approximate changes necessary in the pectin concentration in a jam formula when soluble solids are reduced or increased, the consistency remaining unchanged, can be calculated from Table 4. Apart from the industrial use of pectin for jams and jellies, a considerable amount of high- and low-ester pectins marketed as gelling powders or gelling liquids is used for homemade jams and jellies. 7Q

C. Bakery Fillings and Glazings Fruit-based products are important ingredients within the bakery industry, their acidulous taste and relatively high moisture content contrasting to the baked goods. Oven-resistant high sugar jams may be produced with high-ester pectins, if the recipe used ensures high temperature stability of the product. This is obtained if the solids content is kept relatively high (i.e., around 70%) and by using a relatively rapid setting pectin type. To obtain a satisfactory result, however, it is necessary that the product is not extensively ruptured mechanically (by stirring or pumping). Mechanical rupture of the gel tends to

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.... C 0

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E ,E

90

80

70

60

oc

50

Cooling FIGURE 13. Typical gel formation in jams produced with rapid set and slow set high-ester pectin.

Table 4 PECTIN TYPE AND RELATIVE CONCENTRATION RECOMMENDED FOR JAMS AND JELLIES WITH VARIOUS SOLUBLE SOLIDS CONTENT Percent soluble solids in jam 75 70 65 60 55 45 35 25

Recommended pectin type Slow set high-ester pectin Slow set high-ester pectin Rapid set high-ester pectin Slow set high-ester pectin Rapid set high-ester pectin Moderate calcium-reactive (slow set) low-ester pectin Moderate calcium-reactive (slow set) low-ester pectin Calcium-reactive (rapid set) low-ester pectin Calcium-reactive (rapid set) low-ester pectin

Relative pectin concentration required 77

88

100 (basis) 117 135 145 175 210

initiate syneresis which is greatly increased when heating to oven temperatures. By using nonamidated low-ester pectins, it is possible to produce bakery jams with satisfactory stability at oven temperatures and minimum syneresis tendency after breakage of the gel texture by pumping or stirring. An optimum result, however, requires a relatively high pectin dosage (0.7 to 1.0%) and a strict control of calcium content in the system. A number of pectin-based products are used for decoration purposes within the bakery industry. As these fillings and glazings normally are applied to the baked good after the baking, heat stability is of no importance. Semimanufactured liquid jelly bases containing pectin in solution are often used for industrial bakery lines. Cold gelation is obtained by a continuous addition of acid or calcium to the liquid base immediately before the filling or glazing operation. The heat reversibility of low-ester pectin gels may also be utilized in bakery glazings. By formulating a jelly base with a soluble solids of approximately 65% and a relatively high dosage of a calcium reactive low-ester pectin, a pregelled product with a paste-like texture

226

Food Hydrocolloids

and a relatively good microbiological stability is obtained. Prior to application in the bakery, water is added to the jelly base, and the diluted product is heated to 85°C to melt the lowester pectin gel. The product may now be used for "hot glazing" of fruit tarts and similar products. By cooling, the low-ester pectin gels at optimum conditions - due to the dilution with water - to form a coherent and glossy jelly. D. Fruit Preparations Industrial fruit preparations are mainly used for combination with yogurt and other dairy products. The product is often aseptically filled into large containers (e.g., 1000-kg containers) at relatively low temperatures. Low-ester pectin is usually incorporated into fruit preparations to create a soft, thixotropic gel texture, sufficiently firm to ensure uniform fruit distribution, but still allowing the product to flow out of the container by gravity and endure pumping without disintegration of the texture. 76 ·80 E. Fruit Beverages and Sauces High-ester pectin is used in fruit drink concentrates to stabilize oil emulsion and fruit particle suspension. In this application, the gelation is apparent in the end product only as a thickening effect, as the coherent gel texture 83 has been broken mechanically to obtain a smooth flow. Pasteurization or extensive homogenization must not be used, however, as these treatments tend to change the rheological properties of the system to an extent where the stabilizing effect is lost. The stabilizing and mouthfeel creating properties of pectin are utilized in recombinated juice products and, especially artificially sweetened, soft drinks. 8 1. 82 Pectin is further incorporated into iristant fruit drink powders to produce a natural mouthfeel in the drink. Low-ester pectins, alone or in combination with other food hydrocolloids, are used in fruit or tomato sauces, toppings, table syrups, and ripples to create a thickened, semigelled texture. F. Confectionery Products Slow set high-ester pectins are mainly used within the confectionery industry for making fruit jellies and jelly centers, flavored with natural fruit constituents or synthetic flavors. In combination with whipping agents, pectin is further used as a texturizer for aerated fruitflavored products. Buffered low-ester pectins not requiring addition of acid for gel formation are used for jellies and centers in which the low pH range necessary for high ester pectin gelation is not acceptable for flavor reasons (e.g., peppermint- or cinnamon-flavored jelly beans). At low concentrations, low-ester pectin may further impart a thixotropic texture to confectionery fillings. At higher concentrations, a cold gelation can be obtained if calcium ions are allowed to diffuse into the product. 77 ·84 ·85 Compared to other gelling agents commonly used for confectionery products, pectin requires that recipe and production parameters are strictly observed, but offers the advantage of an excellent texture and mouthfeel, an extremely good flavor release, and compatibility with modem continuous processing due to a fast and controllable gelation. Commercial pectins manufactured to yield specific solubility characteristics may dissolve in systems with a high soluble solids (i.e. 75 to 80%), if heated under pressure to a temperature close to l40°C. Such pectins are used for confectionery jellies or centers produced continuously on jet-cooking lines or with pressure dissolvers, equipment extensively used within the confectionery industry for a variety of products. G. Dairy Products The ''protective colloid'' effect of high-ester pectin is utilized to stabilize sour milk drinks either cultured or produced by direc·t acidification (fruit juice-milk combinations). (,6·78 ·86 ·87

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The pectin reacts with the casein, prevents the coagulation of the casein at pH below the isoelectric pH (4.6), and allows pasteurization of the sour milk products to extend their shelf life. The stabilizing effect is not limited to casein particles. It is, for example, possible to produce stable acidified whey drinks and soy milk drinks with pectin. The texture of yogurt may be improved by small amounts of low-ester pectin added to the milk before pasteurization and fermentation. Low-ester pectins also form gels with calcium present in milk at higher pH. Low-ester pectin is hence suited as gelling agent for milk desserts, but less economic in use than, for example, carrageenan, which gels milk at a much lower use concentration. Low-ester pectin may, however, be preferred as gelling agent for milk desserts combined with acidic fruit sauces. Unlike carrageenan, low-ester pectin will not react with casein in the gel to form a cheeselike precipitate at the interface where pH is reduced by hydrogen ion diffusion. The calcium reactivity of low-ester pectin may be utilized when adding milk (calcium ions) to a fruit syrup containing low-ester pectin. A canned fruit syrup with 20 to 30% soluble solids and pH 4.0, containing 2% low-ester pectin with moderate calcium reactivity in solution will, when mixed with an equal amount of cold milk, quickly produce a fruitflavored gelled milk dessert.

H. Miscellaneous The use of low-ester pectin as gelling agent and texturizer has been suggested in numerous food products, ranging from artificial caviar and meat products to dessert jellies. 88-:90 A synergistic effect between pectin and alginate regarding gel formation properties has been reported. 69 ·9 ' In combination with xanthan gum, pectin is used as a stabilizer for salad dressing. 92 ·93 Incorporation of pectin in water ice and sherbet reduces ice crystal growth and improves mouthfeel and melting properties. 94 Low-ester pectins may, in higher concentrations, be used to produce a frozen water gel on a stick. In combination with galactomannans or carboxymethylcellulose, pectin is further used in ice cream stabilizers. 95 Pectins and reaction products with pectin have been suggested as emulsifiers for lowcalorie mayonnaise and fruit butters. 96 Optimum effect in forming and stabilizing emulsions has been reported to depend on pH of the system. 97 The quality of frozen fruit may be improved by incorporation of low-ester pectin, adding firmness to the product and reducing juice exudation. 98 Shelf life and appearance of dehydrated or candied fruits may be improved by coating with an edible low-ester pectin film. 99 Binding and texturizing properties of pectin have been reported to influence the physical properties of spray-dried instant tea and dietetic bread positively. 100 - 101 As a curiosity, it can finally be mentioned that pectin has found its way as binder and texturizer into the standard "space menu" of Russian astronauts. 102 •

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9. Petit, R., Les matieres pectiques, Afinidad, 32. 585, 1975. 10. Kawabata, A., Studies on chemical and physical propenies of pectic substances from fruits. in Memoirs of the Tokyo University of Agriculture, Vol. 19, The Tokyo University of Agrigulture, Tokyo, 1977, 115. 11. Pedersen, J. K., Pectins, in Handbook of Water-Soluble Gums and Resins, Davidson, R. L.. Ed., McGrawHill, New York. 1980, chap. 15. 12. Pilnik, W. and Voragen, A.G. J., Pektine und Alginate in Gelier-und Verdickungsmillel in Lebensmi1teln, Neukom, H. and Pilnik. W .. Eds., Forster Verlag AG. Zurich. 1980, 67. 13. Baker, G. L., Joseph, G. H., Kertesz, Z. I., Mottern, H. H., and Olsen, A.G., Revised nomenclature of the pectic substances, Chem. Eng. News. 22, 105, 1944. 14. Anon., Amidated pectin, Pectins, in Specifications for identity and purity of carrier solvents, emulsifiers and stabilizers, enzyme preparations. flavouring agents, food colours, sweetening agents and other food additives. FAO Food and Nutrition Paper 19, Food and Agriculture Organization of the United Nations, Rome. 1981. 10-14, 152-155. 15. Anon., Pectin. in Food Chemicals Codex. 3rd ed., National Academy Press. Washington, D.C.. 1981. 215. 16. Anon., E 440(a) - Pectin, E 440(b) - Amidated pectin. in Council Directive of July 1978 laying down specific criteria of purity for emulsifiers, stabilizers, thickeners and gelling agents for use in foodstuffs, Official Journal of the European Communities. L 223, 1978, 16. 17. Anon., Pectin. in The United States Pharmacopeia. 20th rev., United States Pharmacopeial Convention. Rockville, 1980, 590. 18. Anon., Pectin. in The United States Pharmacopeia. 20th rev .. Suppl. 3. United States Pharmacopeial Convention. Rockville, 1982, 565. 19. Anon., Pectin. The United States Pharmacopeia. 20th rev .. Suppl. 3, United States Pharrnacopeial Convention, Rockville, 1983, 707. 20. Cox, R. E. and Higby, R. H., A better way to determine the jellying power of pectins. Food Ind .. 16, 441. 1944. 21. Institute of Food Technologists. Pectin standardisation, final repon of the IFT commillee, Food Technol., 13. 496. 1959. 22. Steinhauser, J., Otterbach, G., and Gierschner, K., Vergleich von Metoden zur Bestimmung der Gelierkraft von Pektin, Ind. Obst Gemuseverwerr., 64, 179, 1979. 23. Joseph, G. H. and Baier, W. E., Methods of determining the firmness and setting time of pectin test jellies, Food Technol.• 3, 18, 1949. 24. Hinton, C. L., The setting temperature of pectin jellies, J. Sci. Food Agric.. I, 300, 1950. 25. Anon., Gel power of low ester pectin, in Food Chemicals Codex. 2nd ed., National Academy of Science, Washington. D.C.. 1972, 580'. 26. Cambell, L. A. and Palmer, G. H., Pectin, in Topics in Dietary Fiber Research. Spiller. G. A.. Ed., Plenum, New York, 1978, 105. 27. Anon., Evaluation of cenain food additives, 25th repon of the Joint FAO/WHO Expen Committee on Food Additives, World Health Organization, Geneva, 1981. 28. Anon., Fed. Regist., 48, 51148, 1983. 29. Anon., Depanmental consolidation of the food and drugs act and of the food and drug regulations with amendments to August 5, 1982, Depanment of National Health and Welfare, Canada, 1981. 30. Karpovich, N. S., Telichuk, L. K., Donchenko, L. V., and Totkajlo, M. A., Pectin and raw material resources, Pishch. Promst. (Moscow), 3, 36, 1981. 31. Ishii, S., Kiho, K., Sugiyama, S., and Sugimoto, H., Low methoxyl pectin prepared by pectin-esterase fromAspergillusjaponicus. J. Food Sci., 44,611, 1979. 32. Kohn, R., Markovic, 0., Machova, E., Deesterification mode of pectin by pectin esterases of Aspergil/us foetidus. tomatoes and alfalfa, Collect. Czech. Chem. Commun.. 48, 790, 1983. 33. Barret, A. J. and Northcote, D. H., Apple fruit pectic substances, Biochem. J., 94, 617, 1965. 34. Aspinall, G. 0., Craig, J. W. T., and Whyte, J. L., Lemon peel pectin. I. Fractionation and panial hydrolysis of water-soluble pectin, Carbohydr. Res .. 7, 442, 1968. 35. Rees, D. A. and Wight, A. W., Polysaccharide conformation. VII. Model building computation for a1,4 galacturonan and the kinking function of L-rhamnose residues in pectic substances, J. Chem. Soc. B. 1366, 1971. 36. Palmer, K. J. and Hartzog, M. B., An X-ray diffraction investigation of sodium pectate, J. Am. Chem. Soc .. 67, 2122, 1945. 37. Walkinshaw, M. D. and Amott, S., Conformations and interactions of pectins. I. X-ray diffraction analyses of sodium pectate in neutral and acidified forms, J. Mo/. Biol., 153, 1055, 1981. 38. Walkinshaw, M. D. and Amott, S., Conformations and interactions of pectins. II. Models for junction zones in pectinic acid and calcium pectate gels, J. Mo/. Biol., 153, 1075, 1981. 39. Morris, E. R., Powell, D. A., Gidley, M. J., and Rees, D. A., Conformations and interactions of pectins. I. Polymorphism between gel and solid states of calcium polygalacturonate, J. Mo/. Biol., 155,507, 1982.

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40. Powell, D. A., Morris, E. R., Gidley, M. J., and Rees, D. A., Conformations and interactions of pectins. II. Influence of residue sequence on chain association in calcium pectate gels. J. Mo/. Biol., 155, 517, 1982. 41. Speiser, R., Copley, M. J., and Nutting, G. C., Effect of molecular association and charge distribution on the gelation of pectin, J. Phys. Colloid Chem., 51, 117, 1947. 42. Smit, C. J. 8. and Bryant, E., Properties of pectin fractions separated on diethylaminoethyl-cellulose columns. J. Food Sci., 32. 197, 1967. 43. Heri, W., Neukom, H., and Deuel, H., Chromatographische Fraktionierung von Pektinstoffen in Diathylaminoathyl-cellulose, Helv. Chim. Acta, 44. 1939, 1961. 44. Heri, W., Neukom, H., and Deuel, H., Chromatographic von Pektinen mit verschiedener Verteilung der Methylester-Gruppen auf den Fadenmolekiilen, Helv. Chim. Acta, 44, 1945, 1961. 45. van Deventer-Schriemer, W. H. and Pilnik, W., Fractionation of pectins in relation to their degree of esterification, Lebensm. Wiss. Technol., 9. 42, 1976. 46. Taylor, A. J., lntramolecular distribution of carboxyl groups in low methoxyl pectins - a review, Carbohydr. Polym., 2, 9. 1982. 47. Tuerena, C. E., Taylor, A. J., and Mitchell, J. R., Evaluation of a method for determining the free carboxyl group distribution in pectins. Carbohydr. Polym., 2, 193, 1982. 48. Baig, M. M., Burgin, C. W., and Cerda, J. J., Fractionation and study of chemistry of pectic polysaccharides, J. Agric. Food Chem., 30, 768, 1982. 49. Neukom, H., Amado, R., and Pfister, M., Neuere Erkenntnisse auf dem Gebiete der Pektinstoffe, Lebensm. Wiss. Technol., 13, I, 1980. 50. De Vries, J. A., Rombouts, F. M., Voragen, A.G. J., and Pilnik, W., Enzymatic degradation of apple pectins. Carbohydr. Polym .. 2. 25. 1982. 51. De Vries, J. A., den Vijl, C.H., Voragen, A.G. J., Rombouts, F. M., and Pilnik, W., Structural features of the neutral sugar side chains of apple pectic substances, Carbohydr. Polym., 3, 193. 1983. 52. Owens, H. S., Lotzkar, H., Schultz, T. H., and Maclay, W. D., Shape and size of pectinic acid molecules deduced from viscometric measurements. J. Am. Chem. Soc., 68, 1628. 1946. 53. Christensen, P. E., Methods of grading pectin in relation to the molecular weight (intrinsic viscosity) of pectin, Food Res., 19, 163, 1854. 54. Sorochau, V. D., Dzizenko, A. K., Bodin, N. S., and Ovodov, Y. S., Light-scattering studies of pectic substances in aqueous solution, Carbohydr. Res .. 20, 243, 1971. 55. Davis, M.A. F., Gidley, M. J., Morris, E. R., Powell, D. A., and Rees, D. A., Intermolecular association in pectin solutions, Int. J. Biol. Macromol., 2, 330, 1980. 56. Berth, G., Anger, H., Plashchina, I. G., Brando, E. E., and Tolstoguzov, V. 8., Structural study of the solutions of acidic polysaccharides. II. Study of some thermodynamic properties of the dilute pectin solutions with different degrees of esterification, Carbohydr. Polym., 2, I, 1982. 57. O'Beirne, D. and van Buren, J. P., Size distribution of high weight species in pectin fractions from !dared apples, J. Food Sci., 48, 276, 1983. 58. Padival, R. A., Ranganna, S., and Manjrekar, S. P., Stability of pectins during storage, J. Food Technol., 16, 367, 1981. 59. Michel, F., Doublier, J. L., and Thibault, J. F., Investigations on high-methoxyl pectins by potentiometry and viscometry, Prag. Food Nutr. Sci., 6, 367, 1982. 60. Rinaudo, M., Comparison between results obtained with hydroxylated polyacids and some theoretical models, in Polyelectrolytes, Selegny, E., Ed., Reidel, Dortrecht, 1974, 157. 61. Ravanat, G. and Rinaudo, M., Investigation on oligo- and polygalacturonic acids by potentiometry and circular dischroism, Biopolymers, 19, 2209, 1980. 62. Smit, C. J. 8. and Bryant, E. F., Ester content and jelly pH influences on the grade of pectins, J. Food Sci .. 33, 262, 1968. 63. Kohn, R., Ion binding on polyuronates - alginate and pectin, Pure Appl. Chem .. 42, 371, 1975. 64. Scott, J.E., Fractionation by precipitation with quaternary ammonium salts, Methods Carbohydr. Chem., 5, 38, 1965. 65. Stutz, E. and Deuel, H., Polyampholyte mit verschiedener Ladungsverteilung, Helv. Chim. Acta, 38, 1757, 1955. 66. Glahn, P. E., Hydrocolloid stabilization of protein suspensions at low pH, Prog. Food Nutr. Sci .. 6, 171, 1982. 67. Neukom, H. and Deuel, H., Ober den Abbau von Pektinstoffen bei alkalischer Reaktion, z. Schweiz. Forstv., 30, 223, 1958. 68. Morris, E. R., Gidley, M. J., Murray, E. J., Powell, D. A., and Rees, D. A., Characterization of pectin gelation under conditions of low water activity, by circular dichroism, competitive inhibition and mechanical properties, Int. J. Biol. Macromol., 2, 327, 1980. 69. Thom, D., Dea, I. C. M., Morris, E. R., and Powell, D. A., lnterchain associations of alginate and pectins, Prag. Food Nutr. Sci., 6, 97, 1982.

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70. Mitchell, J. R., Rheology of gels. J. Texture Stud .. 7. 313, 1976. 71. Kohn, R. and Luknar, 0., Intermolecular calcium ion binding on polyuronates - polygalacturonate and polyguluronate, Collect. Czech. Chem. Commun .. 42. 731. I 977. 72. Bystricky, S., Kohn, R., and Sticzay, T., Effect of polymerization degree of oligogalacturonates and Dgalacturonans on their circular dichroic spectra. Collect. Czech. Chem. Commun .. 44. 167. 1979. 73. Rees, D. A., Polysaccharide gels. Chem. Ind. (London). 630. 1972. 74. Rees, D. A., Polysaccharide conformation in solutions and gels - recent results on pectins, Carbohydr. Polym .. 2, 254, 1982. 75. Anon., GENU handbook for the fruit processing industry. The Copenhagen Pectin Factory Ltd .. Lille Skensved (Denmark). 1984. 76. Anon., Fruit preparations for yoghurt. The Copenhagen Pectin Factory Ltd .. Lille Skensved (Denmark). 1980. 77. Anon., Confectionery products with GENU pectins. The Copenhagen Pectin Factory Ltd .. Lille Skensved (Denmark). 1981. 78. Anon., Stabilization of fermented and directly acidified sour milk drinks. The Copenhagen Pectin Factory Ltd .. Lille Skensved (Denmark). 1982. 79. Pfeifer and Langen KG., U.S. Patent 3.595,676, 1965. 80. Valet, R., Zur Herstellung von Fruchtzubereitungen und deren Anwendung in Milchprodukten. Ind. Obst. Gemiiseverwert .. 67. 507. I 982. 81. Termote, F., Rombouts, F. M., and Pilnik, W., Stabilization of cloud in pectinesterase active orange juice by pectic acid hydrolysates. J. Food Biochem. I. 15. 1977. 82. Riicken, W., Die Bedeutung von Pektin und Pektinasen fiir die Trubstabilitiit von Orangelimonaden. Brauwelt. 8. 224. 1979. 83. Schopf, L. D., Sakowicz, J. K., and Trenk, H. L., U.S. Patent 4.321.279. 1980. 84. Christensen, S. H., Pectin a natural hydrocolloid for confectionery products. Confect. Prod .. 43. 378. 1977. 85. Barwick, B. E. and Sneath, M. E., U.S. Patent 4.119.739. 1978. 86. Exler, H., German Patent 270.938. 1969. 87. Arolski, A. T., Usheva, V. B., Gruev, P. V., Richev, G. T., and Doucheva, Z. S., U.S. Patent 4.031,264. 1977. 88. Nesmeyanov, A. N., Rogozhin, S. V., Tolstoguzov, V. B., Misjurev, V. I., Erchova, V. A., and Braudo, E. E., British Patent 1.474.891. 1977. 89. Buckley, K. and Mitchell, J. R., U.S. Patent 3.973.051. 1976. 90. Waitman, R.H. and Hoos, J. W., U.S. Patent 3.367.784. 1978. 91. Toft, K., Interactions between pectins and alginates. Prog. Food Nwr. Sci .. 6. 89. 1982. 92. Jamison, J. D., Towle, G. A., and Vermeychuk, J. G., U.S. Patent 4.129.663. 1978. 93. Nelson, F. F., Newer applications for pectin, Food Prod. Dev .. 13. 38. 1979. 94. Leo, H. T. and Taylor, C. C., U.S. Patent 2.754.214. 1956. 95. ,Sanei Chemical Industries. Japanese Patent 53.124.661. I 978. 96. Kratschanov, C., Stancov, S., Popova, M., and Pancheva, T., Anwendung von Pektinemulgatoren zur Herstellung von Lebensmittelemulsionen mit reduziertem Energiewert. Nahrung. 26. 217.1982. 97. Tokunaga, K., Okuyama, G., Nagasawa, H., and Otani, Y., Effects of pectin on formation and stability of emulsions, Cosme/. Toiletries. 96, 30. 1981. 98. Wegener, J. B., Baer, B. H., and Rodgers, P. D., Improving quality of frozen strawberries with added colloids. Food Technol .. 5. 76. 1951. 99. Swenson, H. A., Miers, J. C., Schultz, T. H., and Owens, H. S., Pectinate and pectate coatings. II. Application to nuts and fruit products, Food Technol .. 7, 232. 1953. 100. Gurkin, M., Sanderson, G. W., and Graham, H. N., U.S. Patent 3,666.484, 1972. IOI. Mylaeus, A., British Patent 1.295.007. 1972. 102. Moldavian Food Industry Research Institute. U.S.S.R. Patent 542.505. 1977.

Index

@ Taylor & Francis a

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INDEX A Acacia, 140 Acceptable daily intake (ADI), pectins, 212 Acid-hydrolyzed cellulose, 7 Acidified whey drinks, 227 Acid milk beverages, 77 Acid resistance, Iara gum, 187- 188 Acute oral toxicity, sodium carboxymethylc~llulose,

103

Adhesiveness, 7 Aerated products , hydroxypropylcellulose, 115, 117 Agar, 83 Agar gel, tara gum, combination with, 187 Agglomeration, sodium carboxymethylcellulose, 53 Aggregation low-ester pectins, 222 pectins, 223 Agronomy guar gum, 172 locust/carob bean gum , 162 Alcohol, tamarind seed polysaccharide , 197 Alcoholic beverages, 50, 120 Alcohol precipitation , pectins, 213 Algaroba, see also Locust/carob bean gum, 164 Alginate, 51, 140, 192, 227 Alkali cellulose preparation, 123 Alkaline foods, 63 Aluminum cellulose gum gels, 62 Aluminum precipitation, pectins, 213 Amidated low-ester pectin, see also Pectins, 208 , 2IO Animal feed, 90, 176 Anionic character, 7 pectins. 223 Anticake , 82 Apple pomace, 212-213 Applications, see Food applications Arabic gum, 140, 201 L-Arabinose, 194 Arrhenius plots, hydrolysis of methylcellulose, 132 Artificial caviar, pectins, 227 Availability guar gum, 176 locust/carob bean gum, 165-166 Avicel®, see also Microcrystalline cellulose, 7, 100 compatibility with miscible liquids, 25 dispersion in water, I9, 20 dispersion using sequestrants , 24 flocculation values, 16, 20 ice cream, 73

B Background, see Historical background Bacteria, 115 Baked goods, see Bakery products

Bakers cheese products. I68 Bakery filling, 30. 22~226 Bakery glazings. see Glazings Bakery jams. 225 Bakery products. see also specific types colloidal microcrystalline cellulose. 38 freshness retention , 149 gluten replacement . 149 guar gum. 180-181 locust/carob bean gum. 168--1-69 low gluten. 152 low calorie, 149 low protein, 149, 152 methylcellulose , 147-149 sodium carboxymethylcellulose. 79-87 staling reduction. 149 tara gum, 188 Barbecue sauce. 169, 180. 182 Batters. 86 Beet pectin. 213 Beta-elimination. pectin solutions. 220-221 Beverage powders. 87-89 Beverages. see also specific types colloidal microcrystalline cellulose . 38-39 foam-mat drying, 151 guar gum, 180. 182 methylcellulose. 148, 151 pectins, 224. 226 sodium carboxymethylcellulose, 87-89 Binder. for matrix. 150 Biodegradation, guar gum. 179 Biscuit dough , 168 Bologna, 168 Bread. 8~6. 188 , 227 Bread flour . 168 Breadings , 180 Bread production system, 201 Brookfield rotational viscometer, 59 Brownie mix, 82 Butterfat antioxidant, 169

C Cake dough, 168 Cake icing, see also Icing, 180 Cake mix, 180, 200 Cakes, 80-82, 180, 188 Calcium, 51 , 222 Calcium binding, pectins, 216 Calcium reactivity, pectins, 210 Caloric reduction, colloidal microcrystalline cellulose, 31, 33 Calorie value, pectins, 212 Canada, regulation of use of pectins, 212 Candied fruits , 227 Candy products, 119 Canned foods , 95, 200

234

Food Hydrocolloids

Canned specialties. 38 Carbohydrate gum. 123 Carboxyl group distribution. pectins. 216, 219 Carboxymethylcellulose. see Sodium carboxymethylcellulose Carboxymethyl groups. 48, 53-54 Carcinogenicity, tara gum. 186 Carob bean gum. see Locust/carob bean gum Carrageenan. 51. 73, 140. 181,201 Carrageenan gel, 67, 166, 187 Casein. 65--66 Caviar. see Artificial caviar Cellobiose unit. 48 Cellulases, 67 Cellulose, 4-7, 10. 47-48 Cellulose ether. 112 Cellulose gel, see Microcrystalline cellulose Cellulose gums, see also specific topics. 1-8. IOI defined, 45 hydroxypropylcellulose, 6---7, 111-120 hydroxypropylmethylcellulose, 5-7, 121-154 methylcellulose, 5-7, 121-154 microcrystalline cellulose. 7, 9-42 sodium carboxymethylcellulose, 5, 7, 43-109 Cellulosic products, manufacturing process for. I 3 Cellulose microfibrils, 11, 12 Cellulose molecule. 48 Ceratonia siliqua, see Locust/carob bean gum Cereals. 87 Cesalpinia spinosum, see Tara gum Cheese, 168, 188 Cheese cake, I 80 Cheese dips, 180 Cheese spreads, 168 Chemical cotton. 48 Chemically leavened products, 80---82 Chemical properties. see Properties Chewiness, 70 Chicken franks, 95 Chlortetracycline (CTC). 97 Chocolate chiffon dessert, 183 Chocolate milk, 77 Chronic oral toxicity. sodium carboxymethylcellulose, 102-103 Chutneys, 192 Citric acid, 178 Citrus juice products, 169 Citrus peel, 212-213 Clingability, colloidal microcrystalline cellulose, 31, 36 Cloud point (CP), methylcellulose solution, 135137 CMC, see Sodium carboxymethylcellulose CMC-casein complex, 77~78 CMC-protein complex, 66 Coatings on foods hydroxypropylcellulose, I 17-119 preservative, 96---97 sodium carboxymethylcellulose, 86 tamarind seed gums, 201 Cocktail mix, 180, 182

Cold gelation. 223 Colloidal microcrystalline cellulose. see Microcrystalline cellulose Commercial pectins, see Pectins Compatibility, see also Hydrocolloid compatibility; Miscible liquids hydroxypropylcellulose, 116---117. 119 sodium carboxymethylcellulose. 64-67 Composition. see Typical composition Concentration. effect of hydroxypropylcellulose, 114 sodium carboxymethylcellulose. 62--63 Condensed whole milk, 77 Condiments guar gum, 180, 182 sodium carboxymethylcellulose, 9 I tara gum, 188 Confectionary colloidal microcrystalline cellulose, 39 pectins. 224, 226 sodium carboxymethylcellulose. 92 tamarind seed gum, 201 Conforrnation, cellulose, 4 Corn cobs, 4 Corn stalks, 4 Corn syrup. 221 Cosmetic lotions. 186 Cottage cheese, 168 , I 80---181 Cotton gin, 48 Cotton !inters, 48 Coulombic repulsion, 53-54 Cream cheese, 167-168 Creamy cocktails, 120 Crowding effect, 61, 66 Crystallization inhibitors, 66 Cultured dairy products, see Dairy products; specific types Curries, 192 Cyamposis rerragonolobus, see Guar gum

D Dainippon Pharrnaceutical Co., Ltd .. 193-194 Dairy products, see also specific types, 7 colloidal microcrystalline cellulose, 38 guar gum, 180---182 locust/carob bean gum, 167-168 pectins. 224, 226---227 sodium carboxymethylcellulose, 68-79 tara gum, 188 Deboned chicken meat, 96 De-esterification pectins, 213-216, 218 pectin solutions, 220 Degradation, pectin solutions, 220 Degree of amidation, pectins, 208-210 Degree of esterification pectins. 208-210, 216, 220 pectin solutions, 219 Degree of polymerization (DP), cellulose, 4, 48

Volume Ill Degree of pseudoplasticity. methylcellulose. I 33 Degree of substitution cellulose, 4--5 hydroxypropylcellulose, 112 methylcellulose, 125-126, 128 sodium carboxymethylcellulose, 49 Dehydrated foods, 95 Depolymerization pectins, 218 pectin solutions, 220 Dessen gels, see Gels Dessen jellies, 227 Dessens. see also specific types methylcellulose, 148 sodium carboxymethylcellulose, 98-99 Diarrhea treatment, I 69 Dietetic foods methylcellulose, 152 sodium carboxymethylcellulose, 92-93 Dioctyl sodium sulfosuccinate, 53 Dispersions colloidal microcrystalline cellulose, 18, 21-24, 33 guar gum, 176--177 sodium carboxymethylcellulose dissolution, 5153 Dissolution techniques, methylcellulose, 128-129 Dissolution time, hydroxypropylcellulose, 113 Doctors, 71, 92 Dolly Madison. 69 Domiati cheese, 79 Donut mixes, 82 Doublets, 63 Dough, 201 Dow Chemical Company, Methocel® products offered by, 126 Drilling muds, 46 Dry mixes. see Packaged dry mixes; specific types

E Edible containers, 120 Edible food bar coating, 152 Edible oil emulsions, 151 Egg-box model, 222-223 Egg composition, 152 Eggnog, 77 Electrolytes. effect of guar gum, 178 sodium carboxymethylcellulose. 63-64 tamarind seed gum, 196 Electrolyte tolerance, 131 13-Elimination, pectin solutions, 220--221 Emergency ration, 152 Emulsifying propenies, hydroxypropylcellulose. 115 Emulsion stabilizer colloidal microcrystalline cellulose, 33 methylcellulose, 151 tamarind seed gum, 201 tara gum, 188

235

Encapsulation of oils methylcellulose. 144, 151 sodium carboxymethylcellulose, 97 Endosperm, 157 guar seed, 172-173, 175-176 locust/carob bean, 162. 164 tamarind seed, 192-193 tara seed. I 86--187 Enzymes. hydroxypropylcellulose. 115 Ethanol, 143. 197. 200 Ethanol tolerance. sodium carboxymethylcellulose, 51 Etherification methylcellulose. 123-124, 127-128 sodium carboxymethylcellulose, 48 Ethers. cellulose. 5 European Economic Community nations. regulation of use of pectins. 212 Extract, tamarind seed. 193 Extraction, pee.tins. 213 Extruded foods colloidal microcrystalline cellulose. 34. 37 methylcellulose. 148. 150. 152 Eye irritation, sodium carboxymethylcellulose. 102

F Far East. tamarind seed gum. 157 FCC status, sodium carboxymethylcellulose. 101102 FDA status guar gum, 175 microcrystalline cellulose. 37 pectins, 212 sodium carboxymethylcellulose. 100--102 tamarind seed gum. 199 Fiber addition, colloidal microcrystalline cellulose. 31, 33 Fibrous floe. 11 Filling (flour paste), tamarind seed gum, 200 Film formation. 7 hydroxypropylcellulose, I 17-119 methylcellulose. 144. 149 plasticized. 144 sodium carboxymethylcellulose. 67 tamarind kernel powder, 198-199 tamarind seed gum. 198-199 unplasticized, 144, 147 Fisheyes. 51, 88, 98 Fish preservation. 97 Flavor component, 169 Flavor release. pectins. 223. 226 Flaxseed, 157 Flocculant in mining industry. guar gum. 176 Flocculation by electrolytes, colloidal microcrystalline cellulose. 16, 18, 20 Flow propenies colloidal microcrystalline cellulose. 22 hydroxypropylcellulose, 114, I 16 pectin solutions, 2 I 9

236

Food Hydrocolloids

tamarind seed gum. 195 Foam-mat drying. 151 Foam slahilizcrs colloidal microcrystallinc ccllulmc. 28-29 guar gum. 183 hydroxypropykellulose. 113 Food applicalions. see also specific 1ypes of foods guar gum. 179-183 hydroxypropykellulose . 117-120 locuslicarnh bean gum . 167-169 me1hykellulose. 144-153 microcryslallinc cellulose. 2.'i-37 mixed gum syslems. 140 pec1ins. 223-227 sodium carboxymelhylcellulosc. 46---47 . 68-- 107 tamarind seed gum. 199--201 Iara gum. 187--188 Food casings. 152--153 Food patties. 150 Food preserva1ion. sodium carhoxymelhykdlulose.

96-98

Freeze-dried producls meals. 150 sodium carhoxymethylcellulose. 95 Freeze-I haw . 188 French fried potatoes. 36 . 150 Fried foods haller replacemenl. 149 French fried potaloes. 36. 150 French frying. 149--150 matrix food hinder. 150 mcthykellulosc. 148--150 oil barrier. 149 Fringe micelles. 61 Frostings . 82--83 Frozen desserts guar gum. 180 tamarind seed gum. 201 Frozen food producls. 7 chicke n pallies . 94 chicken sticks. 94 ice crystal modification. 150 melhylcellulose. 150-151 sodium carhoxymelhylcellulose . 94-95 tara gum. 188 water migralion wntrol. 150 weepage from spinach soufnes. 94 Frozen l'ruil. 94. 227 Frozen peanut dessert. 75 Frozen vegetables. 94 Fruit beverages. see Beverages: specific types Fruit buuers . 227 Fruit drink concenlrates. 226 Fruit lillings in baked goods . 168-- 169 Fruit jellies. 226 Fruit juice. 200 Fruit preparalion. 224 . 226 Fruit spreads. 224 Fruil tarts. ho1 glazing . 226 Functional properties. see also Prnpenies cellulose . 4

hydroxyprnpylce llulose. 112 me1hykellulosc . 122 microcryslalline cellulose . 37--40 pectins. 216

G Galactomannans. 73 . 157. 164 . 175--176. 186 structure . 157 viscosity. 187 Galactose . see also Man nose to galactose (M IG) ratio . 176 D-Galacwse. 194 Garlic . 67 Gastrointestinal absorption . sodium carhoxymelhylcellulosc. 102 . 103 Gelatin. 65---06 Gelation. sodium carhoxymethykellulosc. 61. 62 Gel formation jams. 225 locust 'camh hean gum . 169 pectins . 220--22.l premalUrc. 224 tamarind seed gum . 194 . 197 . 199--200 Iara g um . 187-- 188 Gelling li4uids . 224 Gelling powders . 224 Gelling rate. peclins. 220 Gelling 1cmpcra1Ure . pectins. 220 Gel on a slick. 227 Gel s1reng1h pec1ins . 211. 221--223 1hermogela1ion of melhylcellulose pmduc1s .

136---142

Gel struclUre. 7 Generall y recognized as ,are (GRAS ) guar gum, 175 locuslfcarnb bean gum . 165 me1hykellulose . 123 pec1ins. 212 sodium carboxyme1hykellulosc. 45. 100 Glazings pectins. 224-226 sodium carhoxymclhylcellulose. 82--83 Iara gum. 188 o-Glucose . 194 Glyloid. 193-- 194. 19X Good manufac1uring prJclice hydroxyprupylmethylcellulose . 123 pectins . 212 GRAS. sec Generally rerngnized as safe Gravies sodium carhoxymelhykellulose. 91 tamarind seed gum. 200 Guar curry. 182 field. 173 pods . 174 seeds. 174 1amarind seed gum in combination with . 192

Volume III Guar gum, 66, 73, 157, 171-184, 186-187 agronomy, 172 animal feed, 176 applications, 179-183 availability, 176 baked goods, 180-181 beverages, 180, 182 biodegradation, 179 condiments, 180, 182 cottage cheese, 180-181 curry, 182 dairy products, 180-182 description, I 73, 175 dispersion, 176-177 electrolytes, effect of, 178 endosperm, 172-173, 175-176 FDA status, 175 flocculant in mining industry, 176 foam stabilizers, 183 frozen desserts, 180 generally recognized as safe, 175 historical background, 172-173 labeling, 175-176 mannose to galactose ratio, 158 manufacture, 176 maximum usage levels permitted for, 175 molecular weight, 176 nonionic, 178 packaged dry mixes, 180-182 particle size, 177 pet foods, 180-181 pH, effect of, 178-179 processed cheese products, 180-181 processing, 176 properties, 176-179 regulatory status, 175-176 rheology, 177 salad dressings, 20 I secondary oil recovery, 176 specifications, 175 splits, 176 stability, 178 stabilizer, I 80 structure, 158, I 76 synergy, 179 temperature, 177-178 therapeutic value, 182-183 trade names, 173 typical composition, 172-173 viscosity, 177-179 Guar seed, 157 Guar solutions, 176-179, 181 Gum combinations, see Mixed gum systems

H Heat shock resistance colloidal microcrystalline cellulose, 31 ice cream, 188 sodium carboxymethylcellulose, 70

237

Heat stability, colloidal microcrystalline cellulose, 26-27 Helical structure high-ester pectins, 221 pectins, 216-217 Hemicelluloses, 4 Hercules cellulose gum, see Sodium carboxymethylcellulose Hercules mixing device, 54 High-ester pectins, see Pectins High methoxyl pectins, see also Pectins, 208 High-temperature short-time (HTST) continuous process, 74 High-viscosity, see Viscosity Historical background guar gum, 172-173 locust/carob bean gum, 162-164 methylcellulose, 122 pectins, 206-207 sodium carboxymethylcellulose, 45 tamarind seed gum, 192-193 tara gum, 186 HM-pectins, see also Pectins, 208 Hot cocoa mixes, 88 HPC, see Hydroxypropylcellulose HPMC, see Hydroxypropylmethylcellulose Hydration, sodium carboxymethylcellulose dissolution, 51 Hydrocolloid compatibility methylcellulose, 139-140, 144 microcrystalline cellulose, 24-25 sodium carboxymethylcellulose, 66-67 Hydrocolloids, see also specific topics, 157 Hydroxyethylcellulose (HEC), 97 Hydroxypropylcellulose, 6-7, 66, 111-120 aerated products, 115, I 17 alcoholic beverages, 120 bacteria, 115 candy products, I 19 coatings on foods, 117-119 compatibility, 116-117, 119 concentration, effect of, 114 cream cocktails, 120 degree of substitution, 112 description, 112 dissolution time, 113 edible containers, 120 emulsifying properties, 115 enzymes, 115 film formation, 117-119 flow properties, 114, 116 foaming, I 13 food applications, 117-120 functional properties, 112 manufacture, 112 microorganisms, I 15 moisture and oxygen barrier, 118 moisture barrier efficiency, 118-119 molar substitution, 112 molds, I 15 molecular weight, 112

238

Food Hydrocolloids

nonionic, 7, 112 oil and water emulsions, 115 oxygen barrier efficiency, 119 pH, effect of, 115 precipitation temperature, 114-115 preparing solutions, 112 properties, 112-117 regulatory status, 112 rheology, I 16 salad dressings, 119-120 solubility, 7, I 12-113, I 15 stability, I I 5 stabilizing properties. I I 2 structure, 112-113 surface activity, 7, 112, I 15 thermoplasticity, 7. I 12, 120 thickening properties, 112 trade name, 112 viscosity, 7, I 13-116 whipped toppings, 117-118 whipping properties. I I5, 117 whiskey products. 120 Hydroxypropylmethylcellulose (HPMC), see also Methylcellulose, 5-7, 121-154

I Ice cream birthplace of industry, 69 carrageenan, 73 chewiness, 70 guar gum, 73, 180 heat shock resistance, 70, 188 high-temperature short-time (HTST) continuous process, 74 imitation, 75 lactose crystallization, 71 locust/carob bean gum, 73, 167 microcrystalline cellulose, 73 pectin as stabilizer, 227 primary stabilizer, 73 ribbonettes for, 76 sandiness, 7 I secondary stabilizer, 73 serum separation, 73 sodium carboxymethylcellulose, 45, 68-74 stabilizer houses, 73 symbiosis, 73 tamarind seed gum, 200-201 tara gum, 188 texture, I 88 variegated sauces for, 76 whey-off, 73 Ice crystals, colloidal microcrystalline cellulose, 28-29, 31-34 Ice milk, 32-34 guar gum, 180 sodium carboxymethylcellulose, 74 tamarind seed gum, 201 Ices

guar gum, 180 locust/carob bean gum, 167 sodium carboxymethylcellulose, 75-76 Icing, see also Cake icing, 82-83 Idealized disaggregation of CMC, 54-57 Imitation ice cream, 75 Incipient gelation temperature (!GT), 133, 136, 139. 141-142 Incipient precipitation temperature (!PT}, 135-137. 139 India. tamarind seed gum, 157 Instant bar mixes, 50, 88 Instant cereal, 180, 182 Instant frozen desserts, 75 Instant fruit drink powders, 226 Instant snacks, 180 Instant soups, 180 Instant tea, 227 Instant yogurt drink, 79 Interfacial tension, tara gum, I87 Irish coffee, 98

J Jaguar, 173 Jams and jellies pectins, 223-225 tamarind seed gum, I97, 200-20 I Japan, tamarind seed gum as food ingredient, 200 Javatol, I83 Jellies. see Jams and jellies Jelly beans, 226 Jelly candies, 20 I Jelly centers, 226 Jelly products, 39 Jet-cooking, 226 Juices dehydrated, I 5 I guar gum, 180 Jujubes, 200 Junction zones, 221-223

K Karaya gum, 181,201 Ketchup, 188, 200-201 Klucel®, see also Hydroxypropylcellulose, 7, 66, I 12, 114. I 16, 118-119

L Labeling guar gum, 175-176 locust/carob bean gum, 165 microcrystalline cellulose, 37 sodium carboxymethylcellulose, IOI Lactose crystallization, 71 Lignins, 4

Volume 1/1 Limmits®, 93 Liquid pectin, 213 LM-pectins, see also Pectins. 208 Locust bean seed, 157 Locust/carob bean gum, 66. 73. 157. 161-170. 18C--187 agronomy, 162 availability, 165-166 bakery products, 168-169 cheese . 168 cultured dairy products, 167-168 description , I64--165