Functional food ingredients and nutraceuticals: processing technologies [Second edition] 9781482240658, 9781482240641, 1482240645

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Shi

Food & Culinary Science

FUNCTIONAL FOODS AND NUTRACEUTICALS SERIES

Functional Food Ingredients and Nutraceuticals

Processing Technologies

The second edition of a bestseller, Functional Food Ingredients and Nutraceuticals: Processing Technologies covers new and innovative technologies for the processing of functional foods and nutraceuticals that show potential for academic use and broad industrial applications. The book includes a number of “green” separation and stabilization technologies that have also been developed to address consumers’ concerns on quality and safety issues. It also details the substantial technological advances made in nano-microencapsulation that protect the bioactivity and enhance the solubility and bioavailability, and the preservation of health-promoting bioactive components in functional food products. Containing nine entirely new chapters, the second edition has been enhanced with coverage of recent developments in the different areas of processing technologies. The incorporation of these new emerging technologies strengthens the second edition without compromising the contextual integrity of the original publication.

See What’s New in the Second Edition: • Theoretical approaches in mass transfer modeling, solubility properties, and simulation in extraction process • Innovative nanotechnologies in packaging process and nano-microencapsulation process and technology to protect bioactivity and enhance solubility and bioavailability of health-promoting bioactive components • “Green” separation technologies updated with more information in industrial applications Thousands of research papers have been published on the health benefits of bioactive components from natural resources; many books on functional foods are related to chemical properties or medical functions. With only a few books capturing the related processing technologies, the first edition became a valuable tool to help transform results from the lab into industrial applications. Filled with current and sound scientific knowledge of engineering techniques and information on the quality of functional foods, the second edition of this groundbreaking resource is poised to do the same.

Functional Food Ingredients and Nutraceuticals

SECOND EDITION

SECOND EDITION

Functional Food Ingredients and Nutraceuticals Processing Technologies

E D IT E D B Y

SECOND EDITION

K23337 ISBN: 978-1-4822-4064-1

90000 9 781482 240641

John Shi

SECOND EDITION

Functional Food Ingredients and Nutraceuticals Processing Technologies

Series Editor

John Shi, Ph.D.

Guelph Food Research Center, Canada

Functional Food Ingredients and Nutraceuticals: Processing Technologies, Second Edition

(2015)

Edited by John Shi, Ph.D.

Marine Products for Healthcare: Functional and Bioactive Nutraceutical Compounds from the Ocean

(2009)

Methods of Analysis for Functional Foods and Nutraceuticals, Second Edition

(2008)

Handbook of Fermented Functional Foods, Second Edition

(2008)

Functional Food Carbohydrates

(2007)

Dictionary of Nutraceuticals and Functional Foods

(2006)

Handbook of Functional Lipids

(2006)

Handbook of Functional Dairy Products

(2004)

Herbs, Botanicals, and Teas

(2002)

Functional Foods: Biochemical and Processing Aspects, Volume 2

(2002)

Functional Foods: Biochemical and Processing Aspects, Volume 1

(1998)

Vazhiyil Venugopal, Ph.D.

Edited by W. Jeffrey Hurst, Ph.D.

Edited by Edward R. Farnworth, Ph.D.

Costas G. Biliaderis, Ph.D. and Marta S. Izydorczyk, Ph.D. N. A. Michael Eskin, Ph.D. and Snait Tamir, Ph.D. Edited by Casimir C. Akoh, Ph.D.

Edited by Collete Short and John O’Brien

Edited by G. Mazza, Ph.D. and B.D. Oomah, Ph.D. Edited by John Shi, Ph.D., G. Mazza, Ph.D., and Marc Le Maguer, Ph.D. Edited by G. Mazza, Ph.D.

SECOND EDITION

Functional Food Ingredients and Nutraceuticals Processing Technologies

EDITED BY

John Shi

Boca Raton London 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 © 2016 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 Version Date: 20150827 International Standard Book Number-13: 978-1-4822-4065-8 (eBook - PDF) 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 organization 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. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

Contents Foreword..................................................................................................................ix Preface.......................................................................................................................xi Acknowledgments............................................................................................... xiii Editor.......................................................................................................................xv Contributors......................................................................................................... xvii

Section I “Green” Separation/Extraction/ Concentration Process and Technology 1. Extraction of Health-Promoting Components by Supercritical-CO2 Fluid Process...................................................................3 John Shi, Sophia Jun Xue, Lamin S. Kassama, and Xingqian Ye 2. Solubility of Food Components in the Supercritical-CO2 Fluid Process................................................................................................... 53 John Shi, Sophia Jun Xue, and Siew Young Quek 3. Mathematical Modeling of Supercritical Fluid Extraction................. 105 Helena Sovová 4. Biochemical Reactions in Supercritical Fluids...................................... 127 Željko Knez, Maja Leitgeb, and Mateja Primožicˇ 5. Mass Transfer Coefficient of Plant Oil in Supercritical-CO2 Fluid Extraction............................................................................................ 159 John Shi and Sophia Jun Xue 6. Pressurized Low-Polarity Water Extraction of Biologically Active Compounds from Plant Products................................................ 177 Juan Eduardo Cacace and Giuseppe (Joe) Mazza 7. Purification of Orange Peel Oil and Oil Phase as Functional Foods by Vacuum Distillation.................................................................. 199 Mércia de Fátima M. Bettini 8. Membrane Technology for Production of Nutraceuticals................... 217 Marie-Pierre Belleville and Fabrice Vaillant

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9. Extraction of Functional Food Ingredients and Nutraceuticals from Dairy..................................................................................................... 235 Geneviève Gésan-Guiziou

Section II Nano-Microencapsulation, Delivery System, and Packaging Technologies 10. Microencapsulation of Food Ingredients for Functional Foods........ 267 Siew Young Quek, Qiong Chen, and John Shi 11. Nano-Microencapsulation Technology and Applications in Fortified and Functional Foods................................................................. 319 Yao Olive Li 12. Microencapsulation and Delivery of Omega-3 Fatty Acids............... 373 Luz Sanguansri and Mary Ann Augustin 13. Packaging Functional Foods: From Basic Requirements to Nano Perspectives.................................................................................................. 409 Louise Deschênes 14. High-Pressure Processing of Foods toward Their Industrialization and Commercialization: An Up-to-Date Overview....................................................................................................... 427 Giovanna Ferrentino, Sara Spilimbergo, and Alberto Bertucco 15. Spray-Drying of Nano- and Microcapsules of Nutraceuticals........... 455 Xiang Li, Nicolas Anton, and Thierry F. Vandamme

Section III  Bioprocessing Technology 16. Bioprocessing Technology for Production of Nutraceutical Compounds................................................................................................... 481 Terry H. Walker, Caye M. Drapcho, and Feng Chen 17. Microbial Modeling as Basis for Bioreactor Design for Nutraceutical Production........................................................................... 509 Caye M. Drapcho and Darryl B. Jones

Contents

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Section IV Stability and Bioactivity of Antioxidative Components during Food Processing 18. Dehydration Technologies for Functional Foods and Nutraceuticals.......................................................................................545 Robert V. Parsons and Stefan Cenkowski 19. Biological Antioxidation Mechanisms: Quenching of Peroxynitrite............................................................................................ 589 Takashi Maoka and Hideo Etoh 20. Bioactive Stability and Antioxidative Property of Lycopene from Tomatoes during Processing........................................................... 609 John Shi, Sophia Jun Xue, Lishui Chen, Wenliang Wang, Hetong Lin, Ying Ma, and Gauri S. Mittal Index...................................................................................................................... 639

Foreword Food and nutrition science has advanced significantly over the years, progressing from the introduction of fortified foods to the construction of foods that promote health. Consumer demand for foods with benefits beyond basic nutrition has created commercialization opportunities for food manufacturers; functional foods containing bioactive ingredients and nutraceuticals are becoming more prominent in the marketplace. The creation and application of functional food ingredients and nutraceuticals require knowledge and understanding of complex physiochemical processes. Food scientists, nutritionists, functional food designers, and manufacturers are all confronted with issues related to consumer expectations and confidence. These include challenges regarding the stability and safety of functional foods and dietary supplements that are associated with claims to health-promoting benefits. This edition of Functional Food Ingredients and Nutraceuticals: Processing Technologies helps address some of these challenges in a structured way. The editor, Dr. John Shi (Agriculture and Agri-Food Canada, Guelph Food Research Centre, Ontario), has once again assembled leading experts from 12 countries to update this valuable resource. Thousands of research papers have been published on the health benefits of bioactive components from natural resources; many books on functional foods are related to chemical properties or medical functions. With only a few books capturing the related processing technologies, the first edition of this book has been in high demand by those in the food industry, research, and education fields. This resource has become a valuable tool to help transform results from the lab to industrial applications. The second edition incorporates many new and emerging technologies that were not present when the first edition was published in 2004. This includes an emphasis on nanotechnology in packaging processes and nanomicroencapsulation technology to protect and stabilize the bioactivity of health-promoting components. The section on green separation technologies contains revised information on industrial applications as well as some new processes and stabilization technologies that have been developed to address consumer concerns regarding quality and safety. Congratulations to Dr. Shi and his colleagues for pursuing the second edition. It will serve as a unique reference for food science professionals and food companies involved in research and development of functional foods

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and food ingredients, as well as college and university students majoring in food science and technology and nutrition science. Siddika Mithani, PhD Assistant Deputy Minister, Science and Technology Branch Agriculture and Agri-Food Canada Gilles Saindon, PhD Associate Assistant Deputy Minister, Science and Technology Branch, Agriculture and Agri-Food Canada

Preface Since the publication of the book Functional Food Ingredients and Nutraceuticals: Processing Technologies in 2004, many new and innovative technologies for the processing of functional foods and nutraceuticals have emerged that show potential for academic use and broad industrial applications. Hence, the editor felt obligated to update the original version commensurate with the new developments in the area of functional foods and nutraceuticals. Furthermore, a number of “green” separation and stabilization technologies have also been developed to address consumers’ concerns about quality and safety issues. For example, nano-microencapsulation field has witnessed substantial technological advancements in enhancing the solubility, bioactivity and bioavailability, and the preservation of health-promoting bioactive components in functional food products. The second edition of Functional Food Ingredients and Nutraceuticals: Process­ ing Technologies has been extensively revised and expanded considerably to reflect recent developments in the different areas of processing technologies. These include theoretical approaches in mass transfer modeling, solubility properties, and simulation in the extraction process, as well as the practical review of new application technologies. The incorporation of these new emerging technologies is aimed to strengthen the second edition without compromising the contextual integrity of the original publication. In this new edition, the innovative nanotechnologies in packaging process and nanomicroencapsulation technology to protect bioactivity and enhance solubility and bioavailability of health-promoting bioactive components have been emphasized. The green separation technologies have been updated with more information on industrial applications. This book can serve as a reference for food science professionals in either government or industry pursuing functional food, and in food ingredient development and for R&D staff in food companies. The book is also appropriate for academic use, as it makes a good scientific reference source for food science and technology and nutrition science and pharmaceutical science faculty and students. Readers will obtain current and sound scientific knowledge of engineering techniques, and information on the quality of functional foods. It is our hope that the scientific community will appreciate our efforts in preparing this book and the impact it will have on advancing the frontiers of functional foods and nutraceuticals. John Shi, PhD Senior Research Scientist Guelph Food Research Center Agriculture and Agri-Food Canada xi

Acknowledgments This book is a product of an extensive multidisciplinary collaborative effort  among scientists and engineers, academicians, and government and industry personnel. Therefore, the editor wishes to express his sincere appreciation to Assistant Deputy Minister Dr. Siddika Mithani, Associate Assistant Deputy Minister Dr. Gilles Saindon, Director General Dr. Denis Petitclerc, and Science Directors Dr. Michele Marcotte and Dr. Gabriel Piette at the Science & Technology Branch, Agriculture and Agri-Food Canada for their assistance, support, and direction in my career accomplishments at Agriculture and Agri-Food Canada. The editor would also like to express his profound appreciation to Professor Yukio Kakud and Professor Gauri S. Mittal (University of Guelph, Canada), Professor James H. Moy (University of Hawaii at Manoa, USA), Professor Sam K.C. Chang (Mississippi State University, USA), Dr. Asbjørn Gildberg (Norwegian Institute of Fisheries and Aquaculture Research, Norway), Dr. Giuseppe Joe Mazza (former CRC Press series editor and senior scientist at Agriculture and Agri-Food Canada, current CEO of MAZZA Innovation Ltd., Canada), Professor Pedro Fito and Professor Amparo Chiralt (Polytechnic University of Valencia, Spain), Professor Albert Ibarz (University of Lleida, Spain), and Stephen Zollo (CRC Press/ Taylor & Francis) for their valuable scientific comments and support and encouragement during the editing process.

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Editor Dr. John Shi is a senior research scientist with the Federal Department of Agriculture and Agri-Food Canada and an adjunct professor at the University of Guelph, Canada. He is coeditor of four books: Functional Foods II—Biochemical and Processing Aspects; Asian Functional Foods; Functional Food Ingredients and Nutraceuticals: Processing Technology; and Functional Foods of the East, published by CRC Press, USA. Recently, he was invited to serve as the book series editor for the Functional Foods and Nutraceuticals book series for CRC Press, as a guest editor for the special issue of Food Innovation in China, and as an editorial member of LWT-Food Science and Technology. Dr.  Shi graduated from Zhejiang University, China, with a master’s in 1985, and Polytechnic University of Valencia, Spain, with a PhD in 1994. As a postdoctoral research fellow, he conducted a USDA research project at North Dakota State University, USA. As a visiting professor he conducted international collaborative research at the Norwegian Institute of Fishery and Aquaculture, Norway, and Lleida University, Spain. He has been an invited keynote speaker at numerous international conferences in the United States, Canada, France, Portugal, Japan, China, Korea, Italy, Thailand, Spain, Argentina, Columbia, Brazil, etc. He has published more than 180 peerreviewed research papers in international scientific journals and 47 book chapters. His current research interests are focused on innovative “green” processes and technology for health-promoting food ingredients, including innovative green separation technology for recovery of functional food ingredients and nano-microencapsulation and micronization technologies to protect bioactivity and enhance the solubility and bioavailability of healthpromoting bioactive components in functional foods for better health benefits.

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Contributors Nicolas Anton Faculté de Pharmacie Laboratoire de Conception et d’Application de Molécules Bioactives Université de Strasbourg Strasbourg, France Mary Ann Augustin CSIRO Food and Nutrition Flagship Werribee, Victoria, Australia Marie-Pierre Belleville Institut Européen des Membranes Université Montpellier 2 Montpellier, France Alberto Bertucco Department of Industrial Engineering University of Padova Padova, Italy Mércia de Fátima M. Bettini Flavor Tec – Aromas de Frutas Ltd. Pindorama, Brazil

Lishui Chen Food R&D Centre COFCO Institute of Nutrition and Health Beijing, China Qiong Chen Food Science and Nutrition School of Chemical Sciences The University of Auckland Auckland, New Zealand Louise Deschênes Food Research and Development Centre Agriculture and Agri-Food Canada St. Hyacinthe, Quebec, Canada Caye M. Drapcho Department of Environmental Engineering and Earth Sciences Clemson University Clemson, South Carolina

Juan Eduardo Cacace Pacific Agri-Food Research Center Agriculture and Agri-Food Canada Summerland, British Columbia, Canada

Hideo Etoh Faculty of Agriculture Shizuoka University Shizuoka, Japan

Stefan Cenkowski Department of Biosystems Engineering University of Manitoba Winnipeg, Manitoba, Canada

Giovanna Ferrentino Department of Industrial Engineering University of Trento Trento, Italy

Feng Chen Department of Food Science and Human Nutrition Clemson University Clemson, South Carolina

Geneviève Gésan-Guiziou INRA-Agrocampus Ouest Science et Technologie du Lait et de l’Oeuf Rennes, France xvii

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Contributors

Darryl B. Jones Department of Environmental Engineering and Earth Sciences Clemson University Clemson, South Carolina

Ying Ma School of Food Science and Engineering Harbin Institute of Technology Heilongjian, China

Lamin S. Kassama Department of Food and Animal Sciences Alabama A&M University Normal, Alabama

Takashi Maoka Research Institute for Production Development Kyoto, Japan

Željko Knez Faculty of Chemistry and Chemical Engineering University of Maribor Maribor, Slovenia

Giuseppe (Joe) Mazza MAZZA Innovation Ltd. Summerland, British Columbia, Canada

Maja Leitgeb Faculty of Chemistry and Chemical Engineering University of Maribor Maribor, Slovenia

Gauri S. Mittal School of Engineering University of Guelph Guelph, Ontario, Canada

Xiang Li Faculté de Pharmacie Laboratoire de Conception et d’Application de Molécules Bioactives Université de Strasbourg Strasbourg, France Yao Olive Li Food Science/Engineering Human Nutrition and Food Science Department California State Polytechnic University Pomona, California Hetong Lin College of Food Science Fujian Agriculture and Forestry University Fujian, China

Robert V. Parsons Department of Biosystems Engineering University of Manitoba Winnipeg, Manitoba, Canada Mateja Primožič Faculty of Chemistry and Chemical Engineering University of Maribor Maribor, Slovenia Siew Young Quek Food Science and Nutrition School of Chemical Sciences The University of Auckland Auckland, New Zealand Luz Sanguansri CSIRO Food and Nutrition Flagship Werribee, Victoria, Australia

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Contributors

John Shi Guelph Food Research Center Agriculture and Agri-Food Canada Guelph, Ontario, Canada Helena Sovová Institute of Chemical Process Fundamentals Academy of Sciences of the Czech Republic Prague, Czech Republic Sara Spilimbergo Department of Industrial Engineering University of Trento Trento, Italy Fabrice Vaillant Research Center of Food Technology University of Costa Rica San José, Costa Rica Thierry F. Vandamme Faculté de Pharmacie Laboratoire de Conception et d’Application de Molécules Bioactives Université de Strasbourg Strasbourg, France

Terry H. Walker Department of Biosystems Engineering Clemson University Clemson, South Carolina Wenliang Wang Institute of Agro-Food Science and Technology Shandong Institute of Agricultural Sciences Jinan, China Sophia Jun Xue Guelph Food Research Center Agriculture and Agri-Food Canada Guelph, Ontario, Canada Xingqian Ye College of Biosystems and Food Science Zhejiang University Zhejiang, China

Section I

“Green” Separation/ Extraction/Concentration Process and Technology

1 Extraction of Health-Promoting Components by Supercritical-CO2 Fluid Process John Shi, Sophia Jun Xue, Lamin S. Kassama, and Xingqian Ye CONTENTS 1.1 Introduction.....................................................................................................4 1.2 Principle of Supercritical-CO2 Fluid Extraction Technology....................5 1.3 Process Concept Schemes and Systems....................................................... 8 1.3.1 Process Principle................................................................................. 9 1.3.2 Process System.................................................................................. 10 1.3.3 Single-Stage Extraction Process...................................................... 13 1.3.4 Multistage Extraction Process......................................................... 13 1.4 Physicochemical Properties of Supercritical-CO2 Fluids........................ 14 1.4.1 Phase Diagram.................................................................................. 14 1.4.2 Physical Properties........................................................................... 15 1.5 Factors Affecting Extraction Yield............................................................. 15 1.5.1 Pressure.............................................................................................. 16 1.5.2 Temperature....................................................................................... 17 1.5.3 Moisture Content of Raw Materials............................................... 18 1.5.4 Cosolvent............................................................................................ 19 1.5.5 Particle Size........................................................................................ 21 1.5.6 Flow Rate............................................................................................ 23 1.5.7 Effect of Time on Yield..................................................................... 24 1.6 Applications in the Food Industry............................................................. 24 1.6.1 Extraction of Bioactive Compounds............................................... 29 1.6.2 Fractionation of Flavors and Fragrances.......................................30 1.6.3 Cholesterol-Free Food Products...................................................... 32 1.6.4 Separation of Spices and Essential Oils......................................... 33 1.6.5 Decaffeination of Coffee and Tea................................................... 36 1.6.6 Fish Oil Concentration..................................................................... 39 1.7 Summary........................................................................................................ 40 References................................................................................................................43

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1.1 Introduction Extraction of health-promoting components from raw materials has usually been accomplished by conventional extraction processes such as solid–liquid extractions, employing organic solvents such as methanol, ethanol, acetone, or hexane, and also through steam distillation. An additional process to evaporate these solvents from extracts is required when organic solvents are used, and the disposal of the effluent raises environmental and safety concerns. There is increasing public awareness of the hazards associated with the use of organic solvents in food processing with regard to the possible contamination of the final products. The possibility of toxic solvent residues remaining in the final product has been a growing concern to consumers, thus warranting stringent regulations. The demand for ultrapure and high value-added products is redirecting the focus of the food and pharmaceutical industries into seeking the development of new and clean separation technology to obtain natural compounds with excellent quality. One of the most important aspects in developing new extraction processes is safety. Thus, there has been increasing interest in the use of environmentally friendly “green” separation technologies that are able to provide high-quality and high bioactive extracts while precluding the toxicity associated with solvents. The reasons to employ “green” separation technologies as a viable separation technique are: (a) tightening government regulations on toxic-chemical solvent residues in food and environmental pollution control, (b) consumers’ concern over the use of toxic-chemical solvents in the processing of food commodities, and (c) increased demand for higherquality products which traditional processing techniques cannot meet. The supercritical fluid extraction technology provides an excellent alternative to the conventional organic solvent extraction methods. It is considered clean and safe, thus generally recognized as “green” separation technology (Herrero et al., 2006; Wu et al., 2007; Chang et al., 2008). Similar to other innovative emerging separation technologies that meet the food quality and safety requirements, it will also ameliorate some of the problems associated with conventional organic solvent-oriented separation processes. Recent changes in the food-processing practices and the new opportunities that exist for innovative food product development have prompted much interest in the supercritical-CO2 fluid extraction technology. Although the technology is known for many years, its application in the food and pharmaceutical industry began only three decades ago (Sihvonen et al., 1999). Since then, more than 100 plants of different capacities have been built globally for extraction of desired solutes from solid materials (Brunner, 2005; Oliveira et al., 2013; Zulkafli et al., 2014). Supercritical-CO2 fluid technology has been widely used to extract essential oils, functional fatty acids, and bioactive compounds, and also recently been applied in the extraction and fractionation of carbohydrates (Glisic et al., 2007; Shi et al., 2007a; Montañés

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et al., 2008, 2009; Mitra et al., 2009; Sahena et al., 2009; Sanchez-Vicente et al., 2009; Shi et  al., 2010a,b). Therefore, supercritical-CO2 fluid extraction is an excellent “green” separation process for health-promoting components because of its nontoxic and environmentally friendly attributes and it does not leave any traces of toxic residues in foods.

1.2  Principle of Supercritical-CO2 Fluid Extraction Technology Supercritical-CO2 fluid extraction is a clean technology and a novel separation process that utilizes the solvent properties of fluids near their thermodynamic critical points. Although many different types of supercritical fluids exist for many industrial applications, CO2 as supercritical solvent is the most desirable fluid for the extraction of bioactive components because of its generally recognized as safe (GRAS) status. The advantages of CO2 as solvent are its easy accessibility and good technological process stability, and it prevents degradation of thermosensitive compounds. It can easily be separated from the extract by altering the system pressure under standard atmosphere or controlled pressure and temperature conditions (Abbas et al., 2008). Table 1.1 shows the physical properties of compressed (20 MPa) supercritical CO2 at 55°C when compared with some condensed liquids that are commonly used as extraction solvents at 25°C. It should be noticed that supercritical-CO2 exhibits density similar to that of the liquid solvents, but it is less viscous and hence highly diffusive. This fluid-like attribute of CO2 coupled with its ideal transport properties and other quality attributes outlined above make it a better choice over other solvents. The specific heat capacity (Cp) of CO2 increases rapidly as the critical point (31.1°C temperature, 7.37 MPa pressure, and at 467.7 g/L flow rate) is approached. Like enthalpy and entropy, the heat capacity also is a function TABLE 1.1 Comparison of Physical Properties of Supercritical CO2 at 20 MPa and 55°C with Some Selected Liquid Solvents at 25°C Properties Density (g/mL) Kinematic viscosity (m2/s) Diffusivity (m2/s) Cohesive energy density, δ (cal/cm3)

CO2 0.75 1.0 6.0 × 109 10.8

n-Hexane 0.66 4.45 4.0 × 109 7.24

Methylene Chloride

Methanol

1.33 3.09 2.9 × 109 9.93

0.79 6.91 1.8 × 109 14.28

Source: Modified from King, J.W., Hill Jr., H.H., Lee, M.L. 1993. In Supplement and Cumulative Index Anonymous. New York, John Wiley & Sons, pp. 1–83. Copyright Wiley-VCH Verlag GmbH & Co. KGaA.

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of temperature, pressure, and density (Mukhopadhyay, 2000). Under ­constant temperature, both the enthalpy and entropy of supercritical-CO2 decreases with increased pressure and increases with increased temperature at constant pressure. The change in specific heat as a result of varying the pressure and temperature is also dependent on density. For example, under constant temperature, specific heat increases with increasing density up to a certain critical level. Above this critical level, any further increase in density reduces the specific heat. When CO2 fluid is pressurized above its critical pressure and temperature (Figure 1.1), it exhibits supercritical solvent behavior. Under these conditions, various characteristic features of the fluid are neither gas nor liquid but in between the two. Although the density of a supercriticalCO2 fluid is similar to that of a liquid, its viscosity is similar to a gas, and hence the diffusivity is intermediate between the two states. Thus, the supercritical state of a fluid has been defined as a state in which the liquid and gas are indistinguishable from each other, or as a state in which the fluid is compressible (i.e., similar behavior to a gas), even though possessing a density similar to that of a liquid and a similar solvating power. Owing to its different physicochemical properties, supercritical-CO2 provides several operational advantages over traditional extraction methods. Due to their low viscosity and relatively high diffusivity, supercritical-CO2 fluids have better transport properties than liquids. They can diffuse easily through solid materials and therefore give faster extraction yields. One of the main characteristics of a supercritical fluid is the possibility of modifying the density of the fluid by changing its pressure and/or temperature. As density is directly related to solubility, the solvent strength of the fluid can be simply modified by altering the extraction pressure (Raventós et al., 2002; Shi and Zhou, 2007; Shi et al., 2009a).

FIGURE 1.1 Supercritical carbon dioxide pressure–temperature phase diagram.

Extraction of Health-Promoting Components

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The significant characteristic traits of CO2 are its inertness, nonflammability, noncorrosiveness, nontoxicity, inexpensiveness, easy availability, odorlessness, tastelessness, and environmentally friendly and GRAS status. Its near-­ambient critical temperature makes it ideal for thermolabile natural products (Mendiola et al., 2007; Oliveira et al., 2013). Carbon dioxide has low selectivity for some polar components, and therefore changing selectivity by the addition of a relatively low amount of modifier (cosolvent) such as ethanol and other polar solvents (water) improves the extraction efficacy. It may be considered the most desirable supercritical fluid for extracting natural products for food and medicinal uses (Shi et al., 2007b, 2009b; Kassama et al., 2008; Yi et  al., 2009; Vargas et  al., 2013). Other supercritical fluids, such as ethane, propane, butane, pentane, ethylene, ammonia, sulfur dioxide, water, chlorodifluoromethane, etc., are also used as fluid for extraction processes. The supercritical-CO2 fluid has a solvating power similar to organic liquid solvents and a much higher diffusivity because of its low surface tension and viscosity. The physicochemical properties of supercritical fluids, such as the density, diffusivity, viscosity, and dielectric constant, can be controlled by varying the operating conditions such as the pressure and temperature or both in combination (Tena et al., 1997; Shi et al., 2007a,b,c, 2009b; Kassama et al., 2008). The separation process can be affected by simply changing the operating pressure and temperature to alter the solvating power of the solvent. After modifying CO2 with a cosolvent, the extraction process can significantly augment the selective and separation power and in some cases extend its solvating powers to polar components (Shi et al., 2009a). In short, the supercritical-CO2 fluid has many advantages over other solvents: (a) it has a solvating power similar to organic liquid solvents and higher diffusivity, lower surface tension, and viscosity; (b) separation can be affected by simply changing the operating pressure and/or temperature to alter the solvating power of the solvent; and (c) modifying CO2 with a cosolvent can significantly augment the selective and separation power, and in some cases extend its solvating powers to polar components. Supercritical-CO2 is being given a great deal of attention as an alternative to industrial solvents because of (a) increased governmental scrutiny and new regulations restricting the use of common industrial solvents such as chlorinated hydrocarbons; (b) its nontoxic and environment-friendly attributes, given that it leaves no traces of toxic solvent residue in final products; (c) sharp increase in energy cost, which increased the cost of traditional energy-intensive separation technique, such as distillation; (d) carbon dioxide is cheap, safe to use, recyclable, and with minimum disposal cost required; (e) stringent pollution-control legislation prompting industries to seek alternative means of waste treatment and utilization; and (f) increased performance demands on materials, which traditional processing techniques cannot meet. Supercritical-CO2 fluid extraction is particularly relevant to food and pharmaceutical applications because of the processing and handling of complex, thermo-sensitive bioactive components, increased application

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in the areas of nutraceuticals, flavors, and other high-value items such as fats and oils (Sahena et al., 2009; Oliveira et al., 2013; Carla et al., 2014; Zhao and Zhang, 2014), purification of a solid matrix, separation of tocopherols and antioxidants, removal of pesticide residues from herbs, medicines, and food ­products, the detoxification of shellfish, the concentration of fermented broth, fruit juices, essential oils, spices, coffee, and the separation of caffeine, etc. (Perrut, 2000; González et  al., 2002; Quancheng et  al., 2004; Liu et al., 2008, 2009; Martinez et al., 2008; Miyawaki et al., 2008; Bashipour and Ghoreishi, 2014; Solana et al., 2014). The supercritical extraction fluid systems are designed such that an intimate contact exists between packed beds formed by a ground solid substratum (fixed-bed of extractable material) with supercritical fluid (Ferreira and Meireles, 2002). During the supercritical extraction process, the solid phase comprises of the solute and the insoluble residuum (matrix) and is brought into contact with the fluid phase which is the solution of the solute in the supercritical fluid (solvent). The extracted material is then conveyed to a separation unit. This technology has been successfully applied in the extraction of bioactive components (antioxidants, flavonoids, lycopene, essential oils, lectins, carotenoids, etc.) from a variety of biological materials such as hops, spices, tomato skins, and other raw or waste agricultural materials (Kassama et al., 2008; Shi et al., 2009a, 2010a,b; Yi et al., 2009; Huang et al., 2010; Xiao et al., 2010). The scale up of some supercritical extraction processes has already been proved in industrial use. It must, however, be stated that commercial applications of the ­supercritical-CO2 fluid extraction technology remained limited to a few highvalue products due to high initial capital investment, its novelty, and complex operating system (Perrut, 2000; Rosa and Meireles, 2005). Adoption of the technology is on the rise as a result of advances in processing ­equipment and the realization of producing high-value products with high profitability (Rosa and Meireles, 2005).

1.3  Process Concept Schemes and Systems The supercritical fluid extraction technology is conceptualized on the basis of obtaining pure extracts without detrimental residues in food and pharmaceutical products desired by consumers. Extraction is a unit process used to separate and isolate a targeted component from substances. The success of the process depends on the distribution of the analytes between two phases, the separation and stationary phases (King et al., 1993). In the phase equilibrium between the liquid and gas, the partition of the liquid phase increases with increasing pressure and decreases with increasing temperature. If the temperature and pressure are simultaneously increased, the transport

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9

properties of both liquid and gas increase and thus convergence occurs. When a supercritical extraction system is set to work under pressure and temperature of 5–50 MPa and ambient to 300°C, respectively, the solubility properties of the supercritical fluid are greatly influenced by its density, diffusivity, and viscosity. The supercritical-CO2 fluid becomes liquid-like with higher extraction potential than organic liquid solvents. King et  al. (1993) stated that CO2 at high densities has solvent properties similar to chloroform and acetone, and if intermediately compressed, it behaves like nonpolar hydrocarbons such as n-pentane or diethyl ether. The separation phase is the dynamic extraction period when the fluid is in direct contact with the sample, whereas the stationary phase is the sample material loaded as a fixed-bed in the extraction column. Supercritical fluid extraction involves the use of compressed gases at or above their critical temperature (Tc) and pressure (Pc). It utilizes the potentials of these special fluids as excellent solvents to solvate certain solutes (bioactive components) from a solid matrix (Rozzi and Singh, 2002). The solute extraction stream from the sample matrix is directly proportional to the product’s solubility and diffusivity in the supercritical medium. Hence, the solutes solubility increases with pressure, whereas its corresponding diffusivity is expected to decrease by two orders of magnitude. The solvent capacity is mainly the function of density and can be improved with the addition of a cosolvent to modify the density and increase the polarity of the supercritical fluid, and thus significantly increase the yield. The supercritical fluid extraction power is dependent on the solubility and phase equilibrium of substances in the compressed gas. Hence, the targeted bioactive components being extracted must be soluble in the supercritical fluid. Controlling the pressure and temperature of supercritical fluid varies the solubility and phase equilibria. The extraction of pure and high-value extract is accomplished without the risk of toxic residual solvent contamination in the final products and environmental pollution of the effluent. 1.3.1  Process Principle Supercritical fluid extraction is a novel separation technique that utilizes the solvent properties of fluids near their thermodynamic critical point (Uquiche et  al., 2004). The physicochemical properties of the supercritical fluids are crucial to the understanding of the process design, calculation and modeling of the extraction process, and optimization of the operating conditions. Therefore, selectivity of solvents to discriminate solutes is a key property of great significance to process engineers. Physical characteristics such as density and interfacial tension are important properties to manipulate for separation to proceed. The density and interfacial properties of the extracts must vary from that of the raffinate to influence coalescence, a step that must occur if the extract and raffinate phases are separate. The supercritical state of the fluid is influenced by temperature and pressure above the critical point.

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The critical point is the end of the vapor–liquid coexistence curve as shown in the pressure–temperature curve in Figure 1.1, where a single gaseous phase is generated. When pressure and temperature are further increased beyond this critical point, it enters a supercritical state. At this state, no phase transition occurs, regardless of any increase in pressure or temperature, nor will it transit into the liquid phase. Hence, diffusion and mass transfer rates during supercritical extraction are about two orders of magnitude greater than organic/liquid solvents. Substances that have similar polarities are easily soluble in solutions, but with increased deviation in polarity, make solubility increasingly difficult. Intermolecular polarities exist as a result of van der Waals forces. Although the solubility behaviors depend on the degree of intermolecular attraction between molecules, the discriminations between different types of polarities are also important. Substances dissolve in each other if their intermolecular forces are similar, or if the composite forces are manifest in the same manner. The physical properties such as the density, diffusivity, dielectric constant, viscosity, and solubility are paramount to supercritical extraction process design. A variety of processes involving extractions with supercritical fluids have been developed and are regarded as a viable extraction technology that meets the food quality and safety requirements. The physicochemical properties of supercritical fluids can be easily varied by altering the operating conditions of pressure and temperature individually or in combination (Brunner, 2005). Many supercritical fluids (carbon dioxide, ethane, propane, butane, pentane, ethylene, ammonia, sulfur dioxide, water, chlorodifluoromethane, etc.) are used in supercritical extraction processes. Brunner (2005) and Rozzi and Singh (2002) have recommended CO2 because of its favorable properties and the ease of changing selectivity by the addition of modifiers such as ethanol and or other polar solvents. 1.3.2  Process System The supercritical fluid extraction process is governed by four key steps: extraction, expansion, separation, and solvent conditioning. The steps are accompanied by four generic primary components: extractor column (highpressure vessel), pressure control valves, separator column, and pressure intensifier (pump) (Figure 1.2) for the recyclable solvent (Reverchon, 1997). The system has other built-in accessories such as heat exchangers for providing a source of heating and condensers for condensing supercritical fluids to liquid, storage vessels, and a supercritical fluid source. Raw materials are usually ground and charged into a temperature-controlled extractor column (forming a fixed bed), which is usually the case for a batch and single stage extractors (Shi et al., 2007a,b; Kassama et al., 2008). The supercritical-CO2 fluid is fed at high pressure by means of  a  pump, which pressurizes the extraction column and also circulates the supercritical

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Dry test meter

Extracts

Three-stage separator columns

Extractor column

CO2 inlet

Pressure regulator

Ice water trap

CO2 pump Mixer

Cosolvent inlet

Cosolvent pump

FIGURE 1.2 Schematic diagram of the supercritical-CO2 fluid extraction system used to fractionate bioactive components from plant matrix.

medium throughout the system. Figure 1.3 shows an example of a typical ­ single-stage supercritical-CO2 fluid extraction system. Once the ­supercritical-CO2 and the raffinate reach equilibrium in the extraction ­vessel by manipulation of p ­ ressure and temperature to achieve the ideal operating conditions, the extraction process proceeds. The mobile phase consisting of the supercritical-CO2 fluid and the solubilized components is transferred to the separator where the ­solvating power of the fluid is reduced by increasing the temperature and/or decreasing the pressure of the system. The extract precipitates in the separator, whereas the supercritical-CO2 fluid is either released to the atmosphere or recycled back to the extractor. In the case where highly ­volatile components are being extracted, a multistage configuration is employed as shown in Figure 1.4 (Shi et al., 2007a,b; Kassama et al., 2008).

Extractor column

Heat exchanger

Heat exchanger CO2 source

Cooling bath

Pressure valve

Separator

Back pressure valve

CO2 pump

CO2 outlet

Extracts outlet

FIGURE 1.3 Schematic diagram of a typical single-stage supercritical-CO2 fluid extraction system.

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2 stage separation vessels

Storage tank

3 stage extraction columns

Cosolvent inlet

CO2 inlet Pumps

FIGURE 1.4 Schematic diagram of a commercial-scale, multistage supercritical fluid extraction system used to fractionate bioactive components. The symbol “ ” is the pressure valves and “ ” is heat exchangers.

The processes described above are semibatch continuous processes where the supercritical-CO2 flows in a continuous mode, whereas the extractable solid feed is charged into the extraction vessel in batches. In commercial-scale processing plants, multiple extraction vessels are sequentially used to enhance process performance and output. Although the system is ­interrupted at the end of the extraction period, when the process is switched to another vessel prepared for extraction, the unloading and/ or loading of the spent vessels can be carried out while extraction is in progress, reducing the downtime and improving the production efficiency (Kassama et al., 2008). A semicontinuous approach on a commercial scale uses multistage extraction processes, which involve running the system concurrently by harnessing a series of extraction vessels in tandem as shown in Figure 1.4. In this system, the process is not interrupted at the end of extraction period for each vessel, because the process is switched to the next prepared vessel by control valves for extraction, while unloading and/or loading the spent vessels. Thus, supercritical-CO2 technology is available in the form of ­single-stage batch that could be upgraded to multistage semicontinuous batch operations coupled with a multiseparation process. The needs of improving the design into truly continuous modes are growing. Supercritical-CO2 fluid extraction could be cost-effective under large-scale production.

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1.3.3  Single-Stage Extraction Process The supercritical fluid extraction system utilizes a prime mover, a pump which provides a constant pressure on the system, thus circulating the supercritical medium from the tank/cylinder throughout the system. Figure 1.3 is an example of a typical single-stage supercritical extraction system. Once operating parameters are preset, the system reaches equilibrium in the single extraction vessel under dynamic condition. The extracts are precipitates in the separator, whereas the supercritical fluids are either released or recycled back to the extractor. In the case where highly volatile components are being extracted, a multistage configuration may have to be employed as shown in Figure 1.4. As the solution leaves the extractor, it flows to the first separation vessel via a pressure regulator. The pasty oleoresins settle to the bottom as they separate due to density difference and collected, whereas the remaining solution goes to the second-stage separator where the fractionation of the volatile components takes place. For more sensitive products, the third stage of separation would be required for the complete isolation of pure volatile components. Saltzman et  al. (1993) presented a design (Figure 1.2) where the solution flows through a heated valve and precipitates into a preweight U-tube in an ice water bath. The glass wool on the U-tube exit trap entrains the solutes in the gasses, which in turn flows through a flow meter that monitors the flow rate. Oszagyan et al. (1996) used a similar system as illustrated in Figure 1.2 to extract essential oil from Lavandula intermedia Emeric ex ­aloisel and herb of Thymus vulgaris L., and further fractionated volatile components (ρ-cymene, γ-terpinene, thymol, and carvacrol). Similarly, Ozcan et al. (2003) used it to fractionate volatile components from Turkish herbal tea (Salvia aucheri Bentham var. canaescen Boiss and Heldr.). Duquesnoy et al. (2004) and Boutekedjiret et al. (2003) extracted and fractionated volatile compounds from plant materials using the supercritical-CO2 fluid with a similar multistage fractionation method. The processes described above are semibatch continuous processes where the supercritical-CO2 fluid is in a continuous mode, whereas the extractable solid samples are charged into the extraction vessel in batches. In commercial processing plants, multiple extraction vessels are sequentially used to enhance the process performance and output. Although the system is interrupted at the end of the extraction period, when the process is switched to a prepared vessel for extraction, the unloading and/or loading of the spent vessels can be carried out while extraction is in progress, reducing the downtime and improving the production efficiency. 1.3.4  Multistage Extraction Process A semicontinuous approach on a commercial scale uses multistage extraction processes that involve running the system concurrently by harnessing

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a series of extraction vessels in tandem as shown in Figure 1.4. The system provides an option to continue the extraction process at the end of the extraction period for each vessel by switching to the next prepared vessel by control valves for extraction while unloading and/or loading the spent vessels, although imperfect, continuity is attained. The primary extraction stages operate in a similar mode to the ones depicted in Figures 1.3 and 1.4. The raffinate from the premier stage enters the first separation vessel, whereas separation and fractionation of different compounds occur based on their relative solubility. The options of cosolvent are available to enhance the solvent power of separation of specific components. This is effective for cases where more than one targeted component is to be extracted, giving the flexibility to vary the extraction parameters such as pressure and temperature to achieve different solubilities for different components being extracted at each stage of the operation. Gamse (2003) suggested that highly soluble substances could be extracted at the initial stages at low supercritical-CO2 fluid density, and by increasing the density in the subsequent stages removes the less soluble substances. The supercritical pressure, temperature, and flow rate at each stage could be controlled independently.

1.4  Physicochemical Properties of Supercritical-CO2 Fluids Supercritical fluids combine unique properties of the gas and liquid phases to enhance their functionality. The values of the supercritical fluid density, diffusivity, and viscosity lie between those of conventional liquids and gases. For example, the supercritical density is less than that of a liquid organic solvent but greater than that of a gas. This distinct property provides supercritical fluid extraction a higher extraction efficacy compared with liquid ­solvents because of its higher mass transfer rate.

1.4.1  Phase Diagram Supercritical state of fluids is influenced by temperature and pressure above their thermodynamic critical points. The critical point is the interface of the saturated vapor–liquid curves as shown in Figure 1.1 for a single gas. Fluids are said to be in their supercritical state by increasing their relative pressure and temperature beyond the critical point. When fluids enter the supercritical region, no phase transition will occur even with further increase in pressure and/or temperature. Supercritical fluids are about two orders of magnitude greater than in the liquid state because of their diffusion and mass-transfer characteristics.

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1.4.2  Physical Properties Physical properties are critical to the functionality of supercritical fluids. Density, diffusivity, dielectric constant, viscosity, and solubility are important properties vital to the successful extraction process design. The physical properties of supercritical fluids such as high diffusivity, low viscosity, and interfacial tension may improve the dissolving power of supercritical fluids, consequently enhancing the extraction efficacy. Substances that have similar polarities are easily extracted because they are readily soluble in the selected solvent, hence with slight deviation in polarity decrease the solubility of the targeted components. The intermolecular polarities between the extraction components are influenced by the van der Waals forces, and the solubility behaviors depend on the degree of intermolecular attraction between molecules. Unique intermolecular forces of substances easily dissolve in each other and hence enhance extraction efficacy. Although many different types of supercritical fluids are available for industrial applications, CO2 is the most desired for extraction of bioactive components. Table 1.1 shows some physical properties of compressed ­supercritical-CO2 at pressure (20 MPa) and temperature (55°C) compared with condensed liquids commonly used as extraction solvents at 25°C. It should be noticed that supercritical-CO2 exhibited density similar to that of the liquid solvents, but it is less viscous and highly diffusive. This fluid-like attribute of CO2 coupled with its ideal transport properties and other quality attributes outlined above make it a better choice over other solvents. The heat capacity of supercritical fluids is a function of temperature, pressure, and density. The specific heat capacity (Cp) of CO2 increases rapidly as the critical point (31.1°C temperature, 7.37 MPa pressure, and at 467.7 g/L flow rate) is approached. This implies an increase in enthalpy per unit mass of supercritical fluid at any given unit change in temperature, thus having significant effect on the rate of heat transfer. Therefore, the effects of temperature and specific heat on energy gain/loss and on the target bioactive compounds must be well evaluated. Sample matrix is an important parameter that influences solubility and mass-transfer process during supercritical-CO2 fluid extraction. Properties such as particle shape and size distribution, porosity and pore size distributions, surface area, and moisture content influence solubility and mass transfer. The presence of water (moisture content) in the sample matrix during supercritical extraction also has an effect on the extraction outcome.

1.5  Factors Affecting Extraction Yield Several bioactive components were extracted successfully by the ­supercritical-CO2 fluid extraction method as outlined in the preceding

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sections. Optimization of yield is a function of various independent parameters. Process parameters such as solvent flow rate, resident time, moisture content, particle sizes, and particle size distribution in conjunction with supercritical pressures and temperatures are key parameters for achieving optimum results. Most of these parameters can have individual or combined effects on the rate of extraction, for example, the resident time can have an immense influence on the composition of the extracted compound. 1.5.1 Pressure Figure 1.5 is a typical extraction yield rate curve. It is apparent from the curve that pressure significantly influences the rate of extraction, likewise the extraction time. Extrapolating the normalized yield at the point where the yield curve becomes asymptotic gives significantly different normalized yields of 15%, 11%, and 4% for pressures of 10, 9, and 8 MPa, respectively (Marongiu et al., 2003). Macias-Sanchez et al. (2005) observed similar trends in the supercritical-CO2 fluid extraction of carotenoids and chlorophyll a from Nannochloropsis gaditana, although, as pressure increased beyond a critical point, the yields dropped as a result of increased density. Higher density manifests a double effect, causing an increase in salvation power and a decrease in interaction between the fluids and matrix thus decreasing the diffusion coefficient. Excessive pressure may also increase the compactness of the sample matrix in the extraction column, thus reducing the interparticle porosity hence reducing the mass transport through the matrix which eventually contributes to diminish the yield. The selectivity of solutes is a function of pressure, and an increase in the extraction pressure enhances the extraction ability of different solutes. 16

Yield (%)

12 8 4 0

0

100

200 8 MPa

300 400 Time (min) 9 MPa

500

600

700

10 MPa

FIGURE 1.5 The change in bioactive compound yield against time during supercritical-CO2 fluid extraction of essential oil from J. oxycedrus on extraction rate at a flow rate of 1.5 kg/h and a temperature of 50°C. (Modified from Marongiu, B. et al. 2003. Flavour and Fragrance Journal, 18: 390–397.)

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D’Andrea et  al. (1994) also found optimum yield at a working pressure of 25 MPa and temperature of 55°C for the extraction of azadirachtin and 3-tigloylazadirachtol from neem seeds. Similarly, Tonthubthimthong et  al. (2001) reported optimum yield at a pressure of 23 MPa and a temperature of 55°C. 1.5.2 Temperature Manipulating temperature may have a significant influence on yield during supercritical-CO2 fluid extraction. Figure 1.6 shows a general trend of increase in extraction yield as process temperature increases relative to the pressure (Ge et  al., 2002). Tonthubthimthong et  al. (2001) reported similar trends for extracting nimbin from neem seeds at 20 MPa and at a CO2 flow rate of 0.62 mL/min, and the optimum yield was found at 35°C. Ge et al. (2002) indicated that at a temperature of 35°C, the highest yield was obtained in the first 45 min of a prolonged extraction period of 120 min (Figure 1.6). Although many literatures reported that a correlation is established between increasing temperature and extraction yield (Spanos et al., 1993), others showed no particular trend as far as temperature was concerned (Gomez et al., 1996; Kassama et al., 2008; Yi et al., 2009). Some researchers reported that yield was inversely proportional to temperature at 15 MPa. The combined effect of pressure and temperature on cholesterol extraction was studied by Chao et  al. (1993). At a pressure–temperature setting of 34 MPa and 50°C, respectively, cholesterol yield of 160 mg/100 g was realized compared with 430 mg/100 g when the temperature drops to 40°C and 2.5 kg of CO2 is used. As the CO2 mass increases, yields decrease, but the lowest temperature still maintains the highest yield as shown in Figure

Yield (mg/100 g)

2600 2200 1800 1400

10

15

20 35°C

25 30 Pressure (MPa) 40°C

45°C

35

40

50°C

FIGURE 1.6 The change in bioactive compound yield against pressure during supercritical-CO2 fluid extraction of wheat germ on extraction, time 120 min; rate at flow: 2.0 mL/min and sample size 5 g. (Modified from Ge, Y. et  al. 2002. Journal of Agricultural and Food Chemistry, 50: 686–689.)

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Cholesterol (mg/100 g)

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500 400 300 200 100 0

0

5

10 15 Carbon dioxide (kg) 34.5 MPa/50°C 34.5 MPa/40°C

20

25

13.8 MPa/50°C 24.1 MPa/40°C

FIGURE 1.7 Supercritical-CO2 fluid extraction of cholesterol against carbon dioxide mass in beef tallow at different pressures and temperatures. (Modified from Chao, R.R. et al. 1993. Journal of the American Oil Chemists’ Society, 70: 139–143; Chow, C.K. 2000. Fatty Acids in Foods and Their Health Implications, second edn. (revised and expanded). Marcel Dekker Inc., New York, Basel.)

1.7. Also under constant temperature, yield increase was achieved when pressure decreased. The results demonstrated that higher selectivity is possible at lower pressures and higher temperatures. Froning et  al. (1994) corroborated this fact based on their experiment with lipid and cholesterol extraction from dehydrated chicken meat. The combination of pressure and temperature, 38.6 MPa and 55°C, respectively, yielded 89% lipid and 90% cholesterol, whereas a pressure and temperature combination of 30.3 MPa and 45°C, respectively, produces a much lower yield. Yi et  al. (2009) also reported that increases in lycopene yield could be achieved by raising both the temperature and pressure. As expected, the temperature dependence of the lycopene yield was higher than was the pressure dependence. It is because higher temperatures promote solubility of the solute and increase mass transfer of solute from matrix to the supercritical fluid, thus increasing the yield of extracts. 1.5.3  Moisture Content of Raw Materials Moisture content is a factor that influences extraction of bioactive compound yields as shown in Table 1.2. A maxima yield of 1678 mg/100 g was achieved with 5% moisture content and any further increase or decrease in moisture reduced the yield (Ge et al., 2002). Therefore, it is important to establish an optimum moisture content to maximize yield in the supercritical-CO2 fluid extraction process. The effect of sample pretreatment is crucial in attaining the optimum condition. High-moisture samples inhibit the flow of the supercritical-CO2 fluid by changing the surface tension and contact angles as a result of phase interaction between the three components (water,

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TABLE 1.2 Effect of Moisture Variation on Bioactive Compound Yield during Supercritical-CO2 Fluid Extraction of Wheat Germ Water Content (% Wet Basis) 4 5 8 12

Yield (mg/100 g) 1470 1678 1352 1290

Source: Modified from Ge, Y. et al. 2002. Journal of Agricultural and Food Chemistry, 50: 686–689.

sample matrix, and supercritical-CO2 fluid). However, the removal of excess water frees up the interparticle pores and thus increases the mass transport intensity during extraction. For example, the higher the moisture content, the higher the probability for the formation of a thin film of water between the sample matrix and the supercritical fluid phase. Water has a small but finite solubility in the supercritical-CO2 fluid, and as a result it can also be extracted with the targeted components and its separation can be done at the end of the process. 1.5.4 Cosolvent The use of cosolvent (entrainers) during supercritical-CO2 fluid extraction is key to enhancing the extraction efficiency and cost-effectiveness of the processes. Joslin et  al. (1996) indicated two significant attributes of cosolvents: the interaction between the cosolvent and the solute (direct effect) and the cosolvent–solvent interactions (indirect effect). Cosolvents used in small doses normally at a range of 1%–15% in the supercritical-CO2 fluid can change the overall characteristics of the extraction fluid such as polarity, solvent strength, and specific interactions. These changes in turn can significantly alter the density and compressibility of the supercritical-CO2 fluid. Furthermore, cosolvents improve the selectivity of the desired components and facilitate selective fractional separations. Water and ethanol are GRAS products, an environmental benign, and can therefore be used in food-extraction processes. In consequence, the use of these cosolvents enables the extraction of polar compounds without losing the supercriticalCO2 fluid advantages. The use of cosolvent results in the development of an ­environment-friendly and safe process in food and pharmaceutical uses. Table 1.3 summarizes the results of different cosolvents, ethanol, methylene chloride, and methanol (Cygnarowicz et al., 1990). Ethanol seems to be the most used cosolvent and it was selected in 53% of the supercritical fluid extraction studies on vegetable matrices involving

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TABLE 1.3 Fractionation Data of β-Carotene from Supercritical Carbon Dioxide with Cosolvent Mixtures at the Temperature of 70°C and the Enhancement Factor Based on Fluid Density (17 mol−1) Pressure (MPa) β-Carotene CO 2 21.2 24.9 28.7 32.8 35.8 40.0 43.9

CO2 Density (mol−1) 15.71 16.73 17.65 18.43 18.91 19.49 19.95

β-Carotene CO 2 + 1 wt% Ethanol (Enhancement Factor = 4.7) 22.3 15.92 24.9 16.73 31.6 18.22 37.4 19.14

Yields (×107) 1.95 3.33 6.23 10.00 12.50 19.10 25.4

9.6 19.5 25.2 37.5

β-Carotene CO 2 + 1 wt% Methylene Chloride (Enhancement Factor = 3.5) 23.4 16.28 12.8 24.7 16.67 13.3 31.2 18.16 21.7 37.0 19.08 27.7 β-Carotene CO 2 + 1 wt% Methanol (Enhancement Factor = 2.1) 18.0 13.92 26.8 17.26 33.0 18.47 37.3 19.12

3.98 9.62 15.60 30.60

Source: Modified from Cygnarowicz, M.L., Maxwell, R.J., Seider, W.D. 1990. Fluid Phase Equilibria, 59: 57–71.

entrainers (de Melo et  al., 2014). The solubility enhancement with ethanol resulted in the complex interaction between β-carotene and the supercriticalCO2 fluid and the cosolvent. Joslin et al. (1996) also reported an enhancement factor of 64, 63, and 29 for extracting palmitic acid, stearic, and behenic fatty acids, respectively. Baysal et  al. (2000) used ethanol at different concentrations (5%, 10%, and 15%) to recover β-carotene and lycopene from tomato paste. Although they observed that with a high ethanol concentration, the extraction was hindered due to a decrease in the homogeneity of the extraction mixture, and no statistically significant differences were found between the 10% and 15% concentrations.

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Water as cosolvent has recently been gaining lots of attention. For instance, the addition of water to supercritical-CO2 has been reported to be more effective than adding ethanol to extract phenolic compounds from grape pomace (Da Porto et al., 2014). Water as cosolvent has also been demonstrated to be more efficient than ethanol on the supercritical fluid extraction of ro-grapholide from Andrographis paniculata (Burm. F) Nees leaves (Chen and Yin, 2009) and the removal of caffeine from green tea (Kim et al., 2008). Nevertheless, despite the promising results, experiments reported involving water as cosolvent is not widespread, hence only represents 5% of the supercritical fluid extractions in vegetable matrices (de Melo et al., 2014). 1.5.5  Particle Size Particle sizes have significant impact on the flow behavior of the ­supercritical-CO2 fluid in the sample matrix. The mechanism of sample pretreatment, for example, the methods of drying (air-, oven-, vacuum-, or freeze-drying), would influence particle sizes when subjected to attrition or size reduction. The sizes of particles, shapes, and their random layout (size distribution) would determine what goes through the medium and how fast. The layout would influence the type of pore, either open or blind pores, and their degree of interconnectedness. Process parameters such as pressure influence particle size distributions. Pressure tends to create compactness, and thus decreases the intergranular porosity resulting in increased solid density. The smaller the particle size, the larger is the surface area, and as a result bioactive components are released easily. Coelho et al. (2003) observed no significant effect of particle sizes on the extraction yield as a function of extraction time on a fixed flow rate. The oxygenated compounds increased from 81% to 85% as particle size decreases as shown in Table 1.4. However, the findings of Ge et  al. (2002) were contrary to those of Coelho et al. (2003) in their study of the effect of particle sizes on wheat germ (Table 1.5). Papamichail et al. (2000) extracted essential oil from celery with the supercritical-CO2 fluid. They experienced increased yield (more oil released) as the particle sizes of the seed decrease and attributed that to the pretreatment milling and sieving. A maximum yield of 1838 mg/100 g was obtained with an optimum particle size of 0.505 mm. They observed that very fine and big particle sizes have low extraction yield probably due to higher/too low resistances to mass transfer because of the compact tendency, reflecting reduced pore sizes in finer particle sizes while less interactions with the supercritical fluids in the case for the latter. Likewise, larger particles contain undamaged cell walls rendering them impervious. Particle size reduction is essential for lipoprotein matrix in order to release the embedded lipids in fish during supercritical-CO2 fluid extraction,

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TABLE 1.4 Supercritical-CO2 Fluid Data Compared to Hydrodistillation Extraction of Volatile Components from Fennel (F. vulgare) Fruits of Different Particle Sizes Hydrodistillation (%)

Volatile Components

Stalks

Canfene Sebinene Myrcene α-Phellandrene Limonene γ-Terpinene Terpinolene Fenchone Estragol (E)-Anethole Piperitenone oxide Unknowns Waxes

0.2 0.1 1.2 2.0 2.1 Tr 0.5 15.8 18.9 42.5 0.2 4.8 0.6

Fruits (0.5 mm) 0.2 0.2 1.4 2.2 3.6 0.1 0.6 16.8 20.9 42.2 0.2 3.4

Supercritical-CO2 (%) Fruits (0.55 mm)

Fruits (0.35 mm)

0.2 0.2 1.4 2.2 3.5 Tr 0.6 16.2 21.0 42.5 0.3 5.5

0.1 0.2 1.3 1.9 3.1 Tr 0.6 17.1 21.9 44.6 0.3 0.3

Source: Modified from Coelho, J.A.P. et al. 2003. Flavour and Fragrance Journal, 18: 316–319. Note: Tr (Trace  0.05) change on the yield of lycopene at constant pressure (30 MPa) or temperature (70°C). However, the increase in flow rate from 1.5 to 2.5 mL/ min could enhance the outcome of lycopene, but a further increase from 2.5 to 4.5 mL/min resulted in a decrease in the lycopene amount. Some of these facts were also corroborated by Peker et al. (1992) in their experimental study on extraction rates of coffee beans with the supercritical-CO2 fluid. They indicated the need for long extraction time in conditions where low flow rates are used. Figure 1.8 shows an apparent yield at high flow rates for supercritical extraction of celery oil (Papamichail et al., 2000) and Juniperus oxycedrus essential oil (Marongiu et al., 2003). Summarized in Table 1.6 are the results of Baysal et al. (2000), where a flow rate of 4 kg/h was identified as the optimum condition for attaining the highest yield. Similar trend was observed by Ferreira and Meireles (2002) for extracting essential oil from black p ­ epper. They observed larger yield at 30 MPa using the upper level flow rate (10.54 kg/s).

Yield (kg/kg feed)

0.18 0.12 0.06 0

0

50

100 150 Time (min) 1.1 kg/h

200

250

3 kg/h

FIGURE 1.8 The supercritical-CO2 fluid extraction yield against extraction time of essential oil from celery at pressure (15 MPa) and temperature (45°C). (Modified from Papamichail, I. et al. 2000. Journal of Supercritical Fluids, 18: 213–226.)

24

Functional Food Ingredients and Nutraceuticals

TABLE 1.6 Flow Rate Data on the Supercritical-CO2 Fluid Extraction of Lycopene and β-Carotene from Tomato Paste Flow Rate (kg/h) 2 4 8

Extraction Time (h)

Lycopene (%)

β-Carotene (%)

4 2 1

14 22 20

30 43 34

Source: Modified from Baysal, T., Ersus, S., Starmans, D.A.J. 2000. Journal of Agricultural and Food Chemistry, 48: 5507–5511.

When maximum solubility is attained, the highest CO2 flow rate would offer the highest recovery in extracting lipids from fish. 1.5.7  Effect of Time on Yield Several factors have direct or indirect implications on yield during ­supercritical-CO2 fluid extraction. Resident time is an important factor that influences yield and the economic viability of the process. Other factors such as temperature and pressure could have individual or combined effects. Cherchi et al. (2001) performed detailed analysis of flavor compounds in essential oil extracted from Santolina insularis by supercritical-CO2 fluid extraction and they reported that a change in concentration exhibited a reduced concentration of monoterpenes from 50% in the fraction collected after 30 min to 10% in the fraction collected after 240 min (Figure 1.9a) under optimum conditions of 9 MPa and 50°C in a two-stage separation process. The first-stage separation was accomplished under 9 MPa and 12°C, whereas the final stage used 2 MPa and 15°C. The yield becomes asymptotic at 1.75% with an increase in extraction time, whereas the rate decreases (Figure 1.9b). Hawthorne et  al. (1992) studied the extraction rate on basil conducted at 30 MPa and 45°C for 10 min and identified 1,8-cineole, estragole, eugenol, and selinene and the yield were reportedly dependent on time. Temelli et al. (1995) considered 3–4 h as sufficient time to extract all extractable lipids from freeze-dried krill and 6 h for rainbow trout regardless of the extraction conditions.

1.6  Applications in the Food Industry One of the most important trends in the food industry today is the demand for all-natural food ingredients that are free of chemical additives. Natural antioxidants for food are derivatives of plant by-products. A quantum leap in the supercritical-CO2 fluid extraction technology is made by its applications in decaffeinating coffee, tea, and other bioactive (essential oils from spices)

25

Extraction of Health-Promoting Components

(a) 60

Content (%)

50 40 30 20 10 0

Cumulative quantity (g)

(b)

0

50

100 HM

150 200 Time (min) OM HS

250

300

350

300

350

OS

2 1.5 1 0.5 0

0

100

50 HM

150 200 250 Time (min) OM HS OS

Overall

FIGURE 1.9 Families of flavor compounds extracted from S. insularis at different supercritical extraction times. (a) Percentage of the various compound families at different extraction times, (b) cumulative quantities, expressed as grams of extracted compound families at various extraction times. HM, hydrocarbon monoterpenes; OM, oxygenated monoterpenes; HS, hydrocarbon sesquiterpenes; OS, oxygenated sesquiterpenes. (Modified from Cherchi, G. et al. 2001. Flavour and Fragrance Journal, 16: 35–43.)

components used as ingredients in foods. Likewise, supercritical-CO2 fluid extraction is used to extract flavor and fragrance, and high-value compounds used as ingredients in the food, pharmaceuticals, and neutraceutical products. Large-scale supercritical-CO2 fluid extraction has become a reality for the extraction of high-value products from natural materials. The solvating power of supercritical-CO2 fluids is sensitive to temperature and pressure changes, and thus the extraction parameters may be optimized to provide the highest possible extraction yields with maximum antioxidant activity for health-promoting bioactive components (Kassama et al., 2008; Chen et al., 2009; Yi et al., 2009). With this innovative technology, a process could be designed to extract natural nutrients without the fear of organic solvent residues. A compendium of process parameters used for different product applications is listed in Table 1.7.

Dried ground Sweet orange Sieved (1, 0.7, 0.4, 0.2, 0.08 mm) Caraway seed Anise seed Cloves Spikenard

Wheat germ

Essential oil Limonene Carvone Anethole Eugenol and caryophyllene Yaleranone

Wheat germ oil

Dried, milled

Milled, powder (20 μm diameter)

Dried, ground (