Handbook of Natural Polymers, Volume 1: Sources, Synthesis, and Characterization [1 ed.] 0323998534, 9780323998536

Citation preview

HANDBOOK OF NATURAL POLYMERS VOLUME 1: SOURCES, SYNTHESIS, AND CHARACTERIZATION

Edited by

M.S. SREEKALA School of Chemical Sciences, International and Inter-University Centre for Nanoscience and Nanotechnology & School of Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India

LAKSHMIPRIYA RAVINDRAN School of Energy Materials, Mahatma Gandhi University, Kottayam, Kerala, India

KOICHI GODA Department of Mechanical Engineering, Yamaguchi University, Yamaguchi, Yamaguchi, Japan

SABU THOMAS School of Energy Materials, International and Inter-University Centre for Nanoscience and Nanotechnology & School of Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2023 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-99853-6 For information on all Elsevier publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Matthew Deans Acquisitions Editor: Ana Claudia A. Garcia Editorial Project Manager: Tim Eslava Production Project Manager: Prasanna Kalyanaraman Cover Designer: Christian J. Bilbow Typeset by TNQ Technologies

Contributors Marisa Masumi Beppu School of Chemical Engineering, University of Campinas, Campinas, São Paulo, Brazil

Rameshwar Adhikari Department of Chemistry, Tribhuvan University, Kathmandu, Nepal N.

Shabeer Ahmed Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India

Verônica Simões de Borba Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil

Janaína Barreto Alves Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil

Sowriappan John Don Bosco Department of Food Science and Technology, Pondicherry University, Puducherry, India

Pathipati Anitha Department of Botany, BMS College for Women, Bangalore, Karnataka, India

Rupa Chakraborty Department of Chemistry, Govt. V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India

Panthavur Nairveetil Anjali Department of Food Science and Technology, Pondicherry University, Puducherry, India

Jorge L. Cholula-Díaz School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey, NL, Mexico

N. Ashokkumar Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India

Fernando Cunha Associação Fibrenamics Instituto de Inovação Em Materiais Fibrosos e Compósitos, Guimarães, Portugal Srijan Das Government College of Engineering and Textile Technology, Serampore, West Bangal, India

Gholamreza Askari Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran; Functional Food Research Core (FFRC), University of Tehran, Tehran, Iran

Mallika Datta Government College of Engineering and Textile Technology, Serampore, West Bangal, India J. Desbrieres University of Pau and Adour Countries (UPPA), IPREM, Hélioparc Pau Pyrénées, Pau, France

Anupama Asthana Department of Chemistry, Govt. V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India

Larissa de Souza Department of Microbiology, School of Sciences, JAIN (Deemed-to-be University), Bangalore, Karnataka, India

Eliana Badiale-Furlong Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil

Luciana Di Giorgio Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA, CONICET CCT La Plata - CIC PBA Universidad Nacional de La Plata), La Plata, Argentina

Gautam Basu ICAR-National Institute of Natural Fibre Engineering and Technology, Kolkata, India

Mohammad Ekrami Transfer Phenomena Laboratory (TPL), Department of Food Science,

xi

xii

CONTRIBUTORS

Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran

Sunkadakatte Gowda Jyothi Department of Chemistry, BMS College for Women, Bengaluru, Karnataka, India

S. Elkadaoui Interdisciplinary Research Laboratory in Bioresources Environment and Materials (LIRBEM), ENS, Cadi Ayyad University, Marrakech, Morocco

Amol Kahandal MIT School of Bioengineering Sciences & Research, MIT Art, Design and Technology University, Pune, Maharashtra, India

Zahra Emam-Djomeh Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran; Center of Excellence in Biothermodynamics, University of Tehran, Tehran, Iran; Functional Food Research Core (FFRC), College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran Raúl Fangueiro Associação Fibrenamics - Instituto de Inovação Em Materiais Fibrosos e Compósitos, Guimarães, Portugal; Centre for Textile Science and Technology (2C2T), University of Minho, Guimarães, Portugal Raquel Galante Centro de Inovação em Materiais e Produtos Avançados, LDA, Lagoa, Portugal Koichi Goda Department of Mechanical Engineering, Yamaguchi University, Yamaguchi, Japan Gulden Goksen Department of Food Technology, Vocational School of Technical Sciences at Mersin Tarsus Organized Industrial Zone, Tarsus University, Mersin, Turkey Victória Marques Gropelli Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil Euis Hermiati Research Center for Biomass and Bioproducts, National Research and Innovation Agency (BRIN), Bogor, West Java, Indonesia; Research Collaboration Center for Biomass and Biorefinery, BRIN-UNPAD, Sumedang, West Java, Indonesia Soo-Ah Jin Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States Ravin M. Jugade Department of Chemistry, R T M Nagpur University, Nagpur, Maharashtra, India

Ghulam Mustafa Kamal Institute of Chemistry, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan Ambothi Kanagalakshimi Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India; Postgraduate and Research Department of Biochemistry, Government Arts College for Women, Krishnagiri, Tamil Nadu, India M. Karunanidhi Postgraduate and Research Department of Chemistry, Government Arts College, Udumalpet, Tamil Nadu, India Yokraj Katre Kalyan Chhattisgarh, India

PG

College,

Bhilai,

Ayesha Kausar National Center for Physics, Quaid-i-Azam University Campus, Islamabad, Pakistan Muhammad Khalid Institute of Chemistry, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan S. Kirtana Department of Food Science, Faculty of Veterinary and Agriculture Science, University of Melbourne, Melbourne, VIC, Australia Mariana Larrañaga-Tapia School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey, NL, Mexico Arfa Liaquat Institute of Chemistry, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan Laise Maia Lopes School of Chemical Engineering, University of Campinas, Campinas, São Paulo, Brazil Mahadeva Manjushree Rotary Educational Society, Mandya, Karnataka, India Matías A. Marcantonio Centro de Investigación y Desarrollo en Criotecnología de Alimentos

CONTRIBUTORS

xiii

(CIDCA, CONICET CCT La Plata - CIC PBA Universidad Nacional de La Plata), La Plata, Argentina

Kuppan Narendra Department of Botany, Annamalai University, Chidambaram, Tamil Nadu, India

Juan J. Martínez-Sanmiguel School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey, NL, Mexico

Gulzar Ahmad Nayik Department of Food Science and Technology, Government Degree College, Shopian, Jammu and Kashmir, India

Adriana N. Mauri Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA, CONICET CCT La Plata - CIC PBA Universidad Nacional de La Plata), La Plata, Argentina

Shima Nikkhou Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran

David Medina-Cruz Department of Chemical Engineering, Northeastern University, Boston, MA, United States

Ayesha Noreen Institute of Chemical and Environmental Engineering, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan

Mona Miran Department of Food Science and Engineering, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran Antonia Montilla Instituto de Investigación en Ciencias de la Alimentación (CIAL) (CSICUAM) CEI (CSICþUAM), Campus de la Universidad Autónoma de Madrid, Madrid, Spain Mariana Agostini de Moraes Department of Chemical Engineering, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de Sao Paulo (UNIFESP), Diadema, São Paulo, Brazil F. Javier Moreno Instituto de Investigación en Ciencias de la Alimentación (CIAL) (CSICUAM) CEI (CSICþUAM), Campus de la Universidad Autónoma de Madrid, Madrid, Spain Ebrahim Mostafavi Department of Medicine, Stanford University School of Medicine, Stanford, CA, United States; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, United States Raju Murali Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India; Postgraduate and Research Department of Biochemistry, Government Arts College for Women, Krishnagiri, Tamil Nadu, India Nanda Nagappa Department of Chemistry, BMS College for Women, Bengaluru, Karnataka, India

Murilo Santos Pacheco Department of Chemical Engineering, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de Sao Paulo (UNIFESP), Diadema, São Paulo, Brazil Vinod V.T. Padil Amrita School for Sustainable Development (AST), Amrita Vishwa Vidyapeetham, Amrita University, Amritapuri Campus, Clappana, Kerala, India Barbara Morales Passos Department of Chemical Engineering, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de Sao Paulo (UNIFESP), Diadema, São Paulo, Brazil Fabiana Perrechil Department of Chemical Engineering, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de Sao Paulo (UNIFESP), Diadema, São Paulo, Brazil P. Pugalendhi Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India Cinthia da Silva Queiroz School of Chemical Engineering, University of Campinas, Campinas, São Paulo, Brazil Devarajan Raajasubramanian Department of Botany, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India; Department of Botany, Thiru. A. Govindasamy Government Arts College, Tindivanam, Tamil Nadu, India

xiv

CONTRIBUTORS

Abbas Rahdar Department of Physics, University of Zabol, Zabol, Iran Seema Ramniwas University Centre for Research and Development, Chandigarh University, Gharuan, Mohali, Punjab, India Lakshmipriya Ravindran School of Energy Materials, Mahatma Gandhi University, Kottayam, Kerala, India Mônica Oliveira Reis Federal Institute Catarinense, Araquari, SC, Brazil Anelise Christ Ribeiro Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil Elly Robles School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey, NL, Mexico Victor Hugo Campos Rocha Department of Chemical Engineering, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de Sao Paulo (UNIFESP), Diadema, São Paulo, Brazil Asma Sabir Institute of Chemistry, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan Maryam Salami Functional Food Research Core (FFRC), College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran; Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran Pablo R. Salgado Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA, CONICET CCT La Plata - CIC PBA Universidad Nacional de La Plata), La Plata, Argentina R. Saravanan Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India P. Selvaraj Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India

Marzieh Shakouri Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran Lokesh Sharma MIT School of Bioengineering Sciences & Research, MIT Art, Design and Technology University, Pune, Maharashtra, India Marianne Ayumi Shirai Federal University of Technology e Parana, Post-graduation Program of Food Technology, Londrina, Brazil Srividya Shivakumar Department of Microbiology, School of Sciences, JAIN (Deemed-tobe University), Bangalore, Karnataka, India Cinthia Ortiz Silveira Mycotoxin and Food Science Laboratory, Chemistry and Food School, Federal University of Rio Grande e FURG, Rio Grande, RS, Brazil Ajaya Kumar Singh Department of Chemistry, Govt. V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India; School of Chemistry and Physics, College of Agriculture, Engineering and Science, Westville Campus, University of KwaZulu-Natal, Durban, South Africa Dewi Sondari Research Center for Biomass and Bioproducts, National Research and Innovation Agency (BRIN), Bogor, West Java, Indonesia Adrián Soto-Mendoza School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey, NL, Mexico Richard J. Spontak Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States; Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, United States M.S. Sreekala International and Inter-University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India; School of Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India; School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, India

CONTRIBUTORS

xv

S. Sreevidya Kalyan PG College, Bhilai, Chhattisgarh, India

Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India

Subramani Srinivasan Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India; Postgraduate and Research Department of Biochemistry, Government Arts College for Women, Krishnagiri, Tamil Nadu, India

Alka Tiwari Department of Chemistry, Govt. V.Y.T.PG Autonomous College, Durg, Chhattisgarh, India

Titi Candra Sunarti Department of AgroIndustrial Technology, Faculty of Agricultural Technology, IPB University, Bogor, West Java, Indonesia

Linh B. Truong Department of Chemical Engineering, Northeastern University, Boston, MA, United States

Kappat Valiyapeediyekkal Sunooj Department of Food Science and Technology, Pondicherry University, Puducherry, India

A. Tolaimate Interdisciplinary Research Laboratory in Bioresources Environment and Materials (LIRBEM), ENS, Cadi Ayyad University, Marrakech, Morocco

Jalal Uddin Department of Pharmaceutical Chemistry, College of Pharmacy, King Khalid University, Abha, Saudi Arabia

Md Abu Bin Hasan Susan Department of Chemistry, University of Dhaka, Dhaka, Bangladesh

Abhilash Venkatesh Institute for Nanomaterials, Advanced Technologies and Innovation (CXI), Technical University of Liberec (TUL), Liberec, Czech Republic

Chandrakant Tagad MIT School of Bioengineering Sciences & Research, MIT Art, Design and Technology University, Pune, Maharashtra, India

Juliane Viganó Centro de Ciências da Natureza, Universidade Federal de São Carlos (UFSCar), Buri, São Paulo, Brazil

Muhammad Suleman Tahir Institute of Chemical and Environmental Engineering, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Punjab, Pakistan Haniyeh Takbirgou Transfer Phenomena Laboratory (TPL), Department of Food Science, Technology and Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Karaj, Iran Sabu Thomas School of Energy Materials, Mahatma Gandhi University, Kottayam, Kerala, India; International and Inter-University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India; School of Nanoscience and

K. Vijayasri Department of Chemistry, Bhilai Mahila Mahavidyalaya, Bhilai, Chhattisgarh, India V. Vinothkumar Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Chidambaram, Tamil Nadu, India Prakash G. Williams Department of Botany & Biotechnology, Bishop Moore College, Mavelikkara, Kerala, India Syeda Mahvish Zahra Environmental Design, Health and Nutritional Sciences, Allama Iqbal Open University, Islamabad, Pakistan; Institute of Food Science and Nutrition, University of Sargodha, Sargodha, Pakistan Juliano Zanela Federal University of Technology e Parana, Dois Vizinhos, Brazil

Preface Synthetic polymers have depleted oil reserves and caused related global warming, with a resulting gain in the importance of biopolymers, such as those generated from plant, animal, or microbial biomass. Renewable biomaterials are alternatives to conventional waste disposal that are more ecologically friendly and safer than conventional waste. They can reduce trash generation and environmental damage. Applying unique and inventive ways to use biopolymer-based materials has resulted in considerable advancements in sustainable biotechnology and the bioeconomy in recent years. Oil supply shortages, as well as the consequent, progressive drop in the consumption of oil-based goods, are key motivators for scientists and the general public to work toward environmental sustainability. The polysaccharides, lipopolysaccharides, glycolipids, proteins, and polyhydroxyalkanoates making up this class of compounds are highly suited for environmental applications. The increased polluting of natural resources is a problem that must be addressed as soon as possible if the earth is to remain a habitable home for future generations. We must immediately attend to the degradation of freshwater resources caused by the discharge of untreated or insufficiently treated industrial effluents. Over the past several decades, various initiatives have been devoted to extracting natural polymers. As a result, researchers

and academicians must learn about the preparation, properties, and uses of natural polymers to be successful in gaining awareness about environmental sustainability. Natural polymers have been the subject of major research efforts to improve their properties according to their intended applications. The properties of natural polymers can be enhanced by adding various nanomaterials, blending with biopolymers, fabricating interpenetrating polymer networks (IPNs), etc. Developing a readily available, cost-effective, and environmental pollutionereducing biocomposite is a significant accomplishment for researchers. This book is divided into 26 units. The first unit is a general introduction to natural polymers. The next three units deal with extraction, classification, and composite preparation using starch. The following chapters describe the extraction and characterization of nanocellulose, chitin, pectin, casein, keratin, collagen, alginate, soya protein, polyhydroxyalkanoates, wool, natural rubber, gluten, gutta-percha, and zein. This book also covers the development of composites, gels, and IPNs using natural polymers, as well as the biodegradation, life cycle assessment, and recycling of natural polymers. We believe the scientific community and students will benefit from this book, and we look forward to receiving recommendations and critiques to make it even better in the future!

xvii

C H A P T E R

1 The state of the art of biopolymersnew challenges, opportunities, and future prospects Lakshmipriya Ravindran1, M.S. Sreekala2, 3, 5, Koichi Goda4 and Sabu Thomas1, 2, 3 1

School of Energy Materials, Mahatma Gandhi University, Kottayam, Kerala, India; International and Inter-University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India; 3School of Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India; 4Department of Mechanical Engineering, Yamaguchi University, Yamaguchi, Japan; 5School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, India 2

1.1 Introduction Environmental issues and awareness in sustainability, the drive to produce “eco-friendly” goods that lessen our reliance on petroleum, and economic opportunities are driving advancements in polymers. Eco-friendly polymers are not brand-new (or innovative) substances. But in light of rising greenhouse gas levels, carbon dioxide emissions, and fossilfuel-related resource availability, the creation of eco-friendly polymers with the right mix of characteristics for a range of uses has become a significant research priority. Various biopolymers are shown in Fig. 1.1. Biomaterials have been used mostly as food or in the manufacturing of textiles and furnishings by humans over time [2]. Since the dawn of the industrial revolution, materials derived from petroleum have been the most important source used in creation and production by nearly all commercial entities. This includes the wide use of plastic. However, these resources are becoming depleted, and environmental effects must be considered when using petroleum products for manufacturing and power. Adopting a sustainable approach means that the resources utilized can be replenished by the Earth’s natural cycles. As a result of their

Handbook of Natural Polymers https://doi.org/10.1016/B978-0-323-99853-6.00023-1

1

© 2023 Elsevier Inc. All rights reserved.

2

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

FIGURE 1.1

Types of biopolymers [1].

renewability, biopolymers are experiencing a revolution and greater attention. The demand for eco-friendly goods has propelled the growth of novel biopolymers derived from sustainable biomasses over the last 2 decades. Perhaps not in terms of functional characteristics but relative to expense, biopolymers are competitive with polymers generated from fossil fuels. With the rising cost of oil and biomass, biopolymers are viable because maize and starch are cheap. Bionanocomposites are a remarkable multidisciplinary field that combines biology, materials engineering, and nanotechnology. Polymer nanocomposites are generally formed on the nanometer scale, combining polymers and inorganic/organic fillers. Clays, cellulose whiskers, metal nanoparticles, and other natural fillers are among the biopolymers and fillers that give these novel materials exceptional adaptability. Electrospinning, a powerful novel process, was used to create these advanced products [3]. Specifically, in these materials, fillers at the nanoscale work to link polymers, improving the properties of nanocomposites compared with standard composites [4]. However, because bionanocomposites are biocompatible or biodegradable, they bring a new dimension to the composite. As a result, the body progressively absorbs or eliminates them. Hydrolysis or physiological functions are primarily responsible for their decomposition. As a result, nanocomposites are attracting much attention in medical applications such as tissue engineering, medical implants, dental applications, and drug carriers. Yet the widespread use of these beneficial bionanocomposites in our daily lives will only be possible if they become readily available to customers in sufficient

1.1 Introduction

3

quantities. Nanoclays, now mass-produced on an industrial scale and used as conventional nanomaterials in a spectrum of uses, may be threatened by cellulose whiskers [5]. Nanomaterials based on natural polymers are also commonly used in the production of packaged foods, and the development of nanoparticles based on proteins or polysaccharides has lately transformed the world of benign and biodegradable natural biomaterials [6]. As a result, the toolbox provided by micro- and nanotechnologies opens new possibilities for innovation processes in the food business. More efficient food production is made possible by managing processes and functions within the nanometer range. It is possible to design nutrient delivery systems that contain healthy or low-calorie nutrients using this technique, as well as sensors and diagnostic equipment that can assure the quality and safety of food along the food supply chain. Various packaging concepts are available to improve storage life or indicate degradation in packed product quality. On the other hand, consumers do not have an entirely positive attitude toward foods connected with these new technologies, most notably nanotechnology. So it is crucial to effectively communicate the potential benefits and hazards of various nanotechnology applications so that customers can make educated decisions about whether to partake in those benefits or risks. Those decisions operate as impulses for the development of biopolymer-based materials. Several opportunities exist in pharmaceuticals, food, and food-related industries, as well as medical and food-related products and consumer goods, for biopolymers as stabilizers, thickeners, lubricants, and adhesives. It is possible to implant biopolymers in a patient for an extended period or permanently. The primary materials used in wound treatment and dental repair until this century were derived from plants and creatures. Science and medication have progressed significantly since that time. Over the last 50 years, major breakthroughs have been made in medical devices that work with live tissues. The development of constructed polymers for use in restorative biomaterial devices was sparked by advancements in design and increased accessibility to made materials. Antimicrobials and other pharmaceuticals have lessened the risk of contamination and dismissal, and research into biomaterials frameworks has become a key new interest. Various points of reference have been feasible in this light. New materials today endure longer and perform better than before. Polymer-based biomaterials, in particular, are gaining a great deal of attention for various factors. They deal with various challenges in the restorative sector, including dental, neurological, cardiovascular, and implantable devices to extend patient lives. Polythene sacks have been suffocating the hawksbill sea turtle, which is trying to be released. Plastic waste in the stomach of a sperm whale washed ashore on the coast of Spain, creating an ocean of polythene trash [1]. Since the invention of polythene in the early 20th century, the human race has produced roughly 8300 million tonnes of trash. Most food has been squandered, with around three-fourths of the food being thrown away. Eight million tonnes of plastic waste annually ends up in the ocean. As ingested plastic makes its way up the food chain, our continued healthiness remains unclear. Plastic banning, recycling systems, and harnessing microorganisms that eat plastic are just a few of the many proposed solutions that will be floated in the coming years. Even if something works well, it is not ideal. In light of this, developing biocompatible and biodegradable materials that do not include hazardous or unpleasant chemicals in production and can decay naturally in the environment is critical. Given these factors, scientists and engineers worldwide are working hard to enhance biodegradable materials, such as natural polymers, with carefully regulated characteristics. Fig. 1.2 depicts a graphical representation of the biodegradable polymer life cycle.

4

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

FIGURE 1.2 Life cycle of natural polymers [1].

Natural polymers make up less than 1% of the 300 million tonnes of polymers produced yearly, but their demand continues to rise. Growing consumer consumption of natural polymers in medicinal, healthcare, and other applications is driving the economy [7]. Additionally, natural polymers are utilized in a wide range of sectors other than those in paint and ink. These include building materials like cement and wood, as well as the food packaging and beverage industries, including soft drinks, juices, and personal care products. Economic activity worldwide has grown significantly in recent years. This massive expansion has had serious consequences for current manufacturing and consumption designs. In today’s society, people are becoming more environmentally conscious, and as a result, the perception of sustainable economic systems that rely on energy and materials from unrenewable sources has improved. Biobased polymers are becoming an important element worldwide as they start to be used.

1.2 Classifications of natural polymers 1.2.1 Starch Because of its intrinsic biodegradability, abundance, and yearly recyclability, starch is one of the greatest potential natural polymers. Due to their cheap material cost and ease of processing using ordinary plastic manufacturing equipment, starches make an appealing,

1.2 Classifications of natural polymers

5

low-cost foundation for novel bioplastics [8e11]. Since the well-publicized concerns of oil scarcity and an increased interest in minimizing the environmental impacts of widespread petroleum polymer use, the development and implementation of sustainable starch-based products have received more attention. In recent years, an increasing number of nations have enacted legislation prohibiting single-use plastics. However, research into the distinctive morphologies of various starches and their multiphase transitions during thermal processing has enhanced a thorough understanding of polymeric science, particularly in comprehending the configuration relations in polymers [12]. It is possible to manipulate the amylose/amylopectin ratio by altering the starch’s source and age, along with the processing method. Throwaway plastics are being phased out in many nations, and starch-based products have shown tremendous promise as replacements. Many goods have been created and sold throughout the years. Examples include coatings and pills, panels, and even foams. Ongoing strategies include improved performance and reduced costs for all products. In theory, combining starch-based materials with synthetic oil-based polymers can considerably improve the characteristics of the resulting composite. Such blends are not biodegradable, however, negating the benefit of using a biobased polymer.

1.2.2 Nanocellulose Nanocellulose refers to cellulose nanoparticles on the nanometric scale. A primary component in the great majority of plants’ cell dividers originates from the family of glucose and is specifically an anhydroglucose homopolymer. Cellulose is an intricate biomaterial that can be naturally produced. Because it is environmentally benign, chemical, and biodegradable, it is widely used in biomaterials-based sectors such as the healthcare, pharmaceutical, and food industries [13,14]. The blending and application of nanocellulose as a composite to make outstanding biomaterials have advanced significantly over time. When developing new materials, academics and industry leaders are smitten with nanoparticles. Nanocellulose is categorized as (1) cellulose nanocrystals, (2) cellulose nanofibrils, and (3) bacterial cellulose [Fig. 1.3]. Currently, cellulose nanocrystals are made via acid hydrolysis under controlled circumstances using sulfuric acid (H2SO4), hydrochloric acid (HCl), or phosphoric acid (H3PO4). Three techniques may be used to complete the extraction of nanofibrils from cellulose strands: (I) mechanical medications (homogenization, ultrasonication. crushing, and ball-milling), (II) chemical methods (acid/alkaline hydrolysis, TEMPO mediated-oxidation), and (III) a combination of physical and chemical methods (electrospinning, hydrolysis).

1.2.3 Chitin and chitosan In 1884, scientists initially identified and defined chitin for the first time [15]. Chitin may be obtained from various environmentally friendly resources [16]. Waste biomass may be converted into useful biomaterials using various bioenergies. This achieves economic and ecological sustainability since it decreases the quantity of garbage to discard and the carbon emissions associated with biomaterials being transformed again into CO2 [17]. Arthropod exoskeletons and fungal and yeast cell membranes include chitin, which may be found as

6

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

FIGURE 1.3 Nanocellulose classification. source, products, and application C. Zinge, B. Kandasubramanian, Nanocellulose based biodegradable polymers, Eur. Polym. J. 133 (2020). 109758. https://doi.org/10.1016/J.EURPOLYMJ.2020.109758.

semicrystalline microfibrils. The polymer chitin comprises 10% D-glucosamine and 90% Nacetyl-D-glucosamine (Fig. 1.4) [18]. It is a linear polysaccharide with a glucosamine content of 10 wt.% and 90%, respectively. Inherently hydrophobic due to its high acetyl concentration. In chitosan, the deacetylation of chitin results in a polar solvent-friendly material, thereby improving the efficiency of chitosan. Because of their unique properties, chitin and chitosan are widely used in packaging, dietary supplements, agro-industry, and beauty products [19].

1.2.4 Alginate When disposed of properly, plastic materials that are not biodegradable or recyclable may lead to trash creation and pollution that become dangerous environmental contamination.

FIGURE 1.4 Structure of chitosan [16].

1.2 Classifications of natural polymers

7

Due to procedural and budgetary constraints, only about 3% of the plastic trash produced each year goes into recycling programs. Natural biodegradable and renewable polymers have been offered to decrease the harmful effects and environmental concerns of nonbiodegradable plastic polymers [19e21]. The use of biopolymers to replace synthetic plastics has been investigated in several areas [22,23]. Polysaccharides, proteins, and lipids, as well as mixtures of these, have all been investigated. Polysaccharide-based biopolymers, for example, offer suitable superior mechanical characteristics and have been widely used to develop biofilms [4,7e9] and other applications [24,25]. In addition to its outstanding film-forming characteristics, alginate is biodegradable, biocompatible, and readily available [26,27]. Alginate is made from brown seaweed and is frequently used in the food sector to gel and emulsify products. In alginate, mannuronic and glucuronic acid units are joined to form a copolymer, with the characteristics of alginate mostly determined by the ratio of these units [28]. Numerous publications have discussed the use of alginate films/composites in various applications (Fig. 1.5) [30,31]. Because of their poor mechanical strength and water vapor barrier characteristics, alginate films have had little industrial use despite being a potential component in the manufacture of biodegradable films. The inclusion of various functional elements into alginate-based films has been investigated to improve the films’ physical and functional characteristics [31]. Nanoparticlereinforced composite films for packaging materials have recently received much research interest. When creating functional nanocomposite films, metal and metal oxide nanoscopic particles are the inorganic nanoparticles most often employed. These are nontoxic and biocompatible and used in various biochemical and nonbiological pharmaceutical applications, laser light sensing, solar cells, capacitors, sensing applications, safety glasses, pollutant photodegradation, laser therapy, and antimicrobials [32,33].

FIGURE 1.5 Advantages of alginate [29].

8

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

1.2.5 Natural rubber The chemical formula of natural rubber (NR) is cis-1,4-poly(isoprene). In its original form, NR is an elastomer made from a milky colloidal dispersion obtained from the sap of certain plants, called NR latex [34]. The only commercially significant NR is from sap obtained from the Hevea brasiliensis tree. It is endemic to Brazil and generates a great deal of B 97% poly(isoprene), called hevea. That is how one knows that the NR polymer chain will stay on one side of the double-bond throughout the rest of the molecule. Over the course of around 30 years, the hevea tree produces high-quality latex that may be used in various ways. To connect pendant groups or use chemically reactive locations for cross-linking or grafting, NR has double bonds along its backbone. Because of the weak van der Waals forces of its intermolecular interaction and occasional cross-linking, NR is a mushy and sticky solid with poor tensile strength and elastic modulus. In tropical climates, it becomes pliable at room temperature. The NR backbone’s double bonds make it possible to connect pendant groups or provide chemically reactive spots for cross-linking or grafting during the manufacturing process. During warm weather, it becomes pliable; during cold weather, it becomes brittle. It readily crystallizes when stretched [35]. This substance is dissolvable in organic solvents such as tetrahydrofuran (THF), chloroform (CHF), acetone (Ace), 2-butanone (BBT), 2-hexane (N-HEX), and benzene (BENZEN). Due to its high level of unsaturation, the characteristics of NR degrade rapidly in the presence of sunshine, ozone, and oxygen, making it unsuitable for industrial use. Sulfur, accelerator, fillers, and antioxidants are added to the NR and heated during the vulcanization process to create cross-links (Fig. 1.6). A strong and nonsticky polymer is formed by vulcanization, which has better tensile good durability resistant to polar solvents than the original rubber material. This watershed moment in NR history sparked a global NR industry worth several billion dollars.

1.2.6 Gluten Because wheat has a particular combination of proteins, when flour and water are combined, they may produce an elastic dough with remarkable results [36]. The rubbery substance remains after wheat dough has been rinsed to remove starch granules and water-soluble components is described as gluten. Gluten is a protein component of flour

FIGURE 1.6 Structure of natural rubber [34].

1.2 Classifications of natural polymers

9

that provides the dough with viscoelastic properties [37]. A flour’s qualities must be determined in the culinary business, such as total protein, gluten content, and viscous features [38]. As a by-product of separating starch from wheat flour, gluten may be characterized as a “cohesive, viscoelastic proteinaceous substance.” Once the gluten extract has been dried, the process comes to a close. Studies have greatly emphasized drying of the gluten extract, since excessively elevated temperatures have an adverse influence on the molecular structure of gluten. Lyophilisation has been found to generate more efficient gluten for bread processing on a lab scale than high-temperature air drying does for commercialized gluten synthesis. Grain protein, which is heavily impacted by weather conditions, correlates directly with gluten concentration. Gluten’s qualitative properties are heavily influenced by its genome, according to current thinking [39]. Higher total protein in the flour is positively related to the amount of gluten.

1.2.7 Pectin Pectins are a group of biopolymers with a wide range of chemical properties and are widely used in the nutraceutical and cosmetic sectors for thickening/emulsifying [40]. Several features are critical in these applications, including the molecular structure of the monosaccharide present, degree of esterification, and molecular weight, all of which rely on pectin sources and extraction conditions. Pertinent evidence suggests that several fruits and vegetables contain pectin. It is important to note that many of these “pectins” are not actually “pectin” since they include substantial amounts of sugars that cannot be classified as “pectin” for culinary and therapeutic systems (e.g., arabinose, galactose, and rhamnose) [41]. Since pectins are derived from citrus peels, apple pulps, and sugar cane bagasse, these are now the most abundant industrial pectin resources. Acid extraction, enzyme isolation (cellulases, hemicellulases, polygalacturonases), electromagnetic induction heating, and microwave/ultrasound extraction have all been used for pectin extraction.

1.2.8 Keratin, silk, wool Biomedical engineering and biomedical applications pay close attention to natural fibrous proteins such as collagens, silks, and keratins because of their unique bioactive properties [42,43]. Both Nephila pilipes spider silk and Bombyx mori silkworm silk generate high-tech soft natural fiber composite materials with exceptional mechanical properties [44]. Silk has been used as a woven fabric for hundreds of years due to its distinctive sheen, handling, and mechanical characteristics [45]. Silk includes two proteins: fibroin, which forms the tread corn, and sericin, which surrounds the fibroin fibers to hold them together. It is made up of the amino acids glycine, alanine, and serine and is a very insoluble protein. It causes fibers to form in an alternatively splicedepleated sheet structure caused by the amino acids glycine, alanine, and serine being present in abundance. Silk becomes a well-oriented and highly crystalline polymer when the silkworm’s silk fiber is hardened during spinning. Silk exhibits thermoset behavior despite not being fully cross-linked. Silk fiber dissolution requires a chaotropic salt, which can destabilize proteins in solution. Keratins are fibrous proteins found in many types of epithelial coverings, including hair, wool, feathers, nails, horns, and other

10

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

epithelial proteins. Keratins make up roughly half of the cortical cells in wool. Keratins have a high concentration of half cystine residues, which makes them stand out among other proteins on a molecular level. SOS connections between decreased keratin monomeric units allow keratins to be seen as three-dimensional polymers interconnected by SOS bonds. Wool keratin is a structural fibrous protein used to make films [46e48]. For this reason, as well as pure sericin films, pure keratin films are extremely brittle and have little pliability [49]. Research studies have shown that wool keratin and silk fiber composites have high mechanical characteristics, a-helix transitioning to b-conformation under tension, and bconformation transitioning to a-helix after releasing stretching [50] (Fig. 1.7.). Wool-keratin materials can enhance their mechanical and swelling characteristics when plasticizer is added, as demonstrated in several studies [50]. The structure of wool protein is depicted below (Fig. 1.8.).

FIGURE 1.7 Molecule structure of keratin protein; a-keratin (a-helix) and b-keratin (b-pleated sheet) [51].

1.2 Classifications of natural polymers

FIGURE 1.8

11

Chemical structure of wool protein [74].

1.2.9 Shellac Lac insects in China, India, and Thailand exude a natural polymer of animal origin called shellac, derived from parasitic fungi that live on certain types of trees. It is widely used in the food and paint industries, and to a lesser extent in the pharmaceutical sector, for its outstanding film-forming and protective characteristics [52]. In pharma companies, shellac has been used for encapsulating, glossing, and enteric coating of medicinal goods; however, the use of shellac as an enteric coating material has decreased significantly in recent years. However, there is still a difficulty with solubility. In neutral pH, shellac is not soluble. Shellac-coated tablet disintegration is still an issue due to the pH range in the small intestine’s proximal area of between 3.8 and 6.9. Throughout the enteric polymer family, the carboxyl group controls the enteric characteristics of each molecule (Fig. 1.9.). A rise in pH increases the acidealkaline balance, increasing water solubility and ionized salt production.

1.2.10 Casein Milk and cheese include a high concentration of casein, which constitutes over 80% of their proteins [53]. While casein does not have disulfide linkages, it is still a structurally stable protein due to the numerous proline peptides that contribute to its overall structure. Additionally, casein is often used as an alternative to other proteins in various applications, including food and beverage production, due to its unique functional properties, such as its ability to form stable gels and emulsions. As a result, secondary and tertiary structures are few. Milk contains casein, which has hydrophobic characteristics and is weakly soluble in water. It appears as a suspension of casein particles. As a food ingredient, casein is used to produce a wide range of products, including adhesives, binders, coatings, textiles, and food [54,55]. Casein is an excellent choice for bioengineering since it is low-cost, easily accessible, harmless, and extremely durable. Drug carriers made of casein are commonly seen in the shape of

12

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

FIGURE 1.9

Chemical structure of shellac. Polyesters (A), single esters (B) [52].

spheres. Using glutaraldehyde cross-linking, Latha et al. [56] produced theophylline-loaded casein microspheres with a loading capacity ranging from 54% to 79%. The microspheres had a diameter of 75e200 m and incorporation effectiveness of around 61% when loaded with casein, which also showed improved loading characteristics for the lipophilic medication progesterone [57].

1.2.11 Zein It is estimated that 40%e50% of grain protein content is composed of zein. A key reason for their discovery is that zein is highly soluble in alcoholewater combinations (60%e95%). Zein is part of the protein family known as prolamines. Because of its high concentration of hydrophobic and uncharged amino acids, this compound’s solubility is determined by the makeup of its amino acids, which comprise leucine (20%), proline (10%), and alanine (1%). (10%). Zein is a disulfide-bonded complex blend with an average molar mass of 44 KDa. It is estimated that between 50% and 60% of zein is -helical, with the remaining 15% made up of alphasheets and nonperiodic residues [58]. In the nutraceutical and pharmaceutical sectors, zein is commonly employed in coatings. In addition, zein has been used as a glue and in

1.2 Classifications of natural polymers

13

bioplastics, bubble gum, and cosmetics [59]. Endothelial cells in umbilical veins, human liver cells, and mouse fibroblasts have all shown biocompatibility with zein. This means zein may have applications in administering drugs and constructing bioengineered bones [60,61].

1.2.12 Collagen Collagen is a lengthy and tubular protein complex. It comprises three peptide chains linked to create triple helices by intramolecular hydrogen bonds between glycine and hydroxyproline in neighboring units [62]. An animal’s tissue is mostly composed of collagen, which accounts for 25 to 35% of the total body protein in mammals [63]. To sustain most tissue and cell structures in vivo, numerous collagen fibrils combine to create fibrous collagen. With regard to connective tissue, collagen holds up well under tension and is the primary building block. Collagen is a natural substance with great bioactivity, low cytotoxicity, and high absorption efficiency. Many commercialized collagen materials have been used to fabricate tissue engineered to treat severe burns.

1.2.13 Hemicellulose In terms of dry weight, hemicellulose accounts for about 25%e30% of the total. Because of its reduced molecular weight, it is a polysaccharide rather than cellulose [64]. It consists of Dxylose, mannose, galactose glucose, L-arabinose, beta-1,4- and b-1,3-glycosidic linkages. Hardwood hemicellulose’s primary constituent is glucuronoxylan, while softwood’s primary constituent is glucomannan. This polysaccharide is made up of sugar monomers such arabinose, xylose, mannose, galactose, and uronic acids [65]. They do not produce microfibrils as cellulose does. However, they have the ability to create hydrogen bonds with cellulose and lignin, and as a result, they are referred to as “cross-linking glucans.”

1.2.14 Lignin Lignin is the wood’s cementing substance, and it gives the wood flexibility and mechanical strength. The phenylpropane units of this phenolic macromolecule are highly cross-linked. It results in higher thermal stability than hemicellulose [66]. Lignin is one of the most common biopolymers on the planet, coming in second only to cellulose in global production. Tonnes of lignin are biosynthesized each year on Earth. In softwoods, lignin accounts for up to 30% of the dry weight, while in hardwoods, it makes up 20%. This natural composite substance, made of lignin and hemicellulose, gives trees and plants their strength and stiffness. Forage legumes and grasses contain complexes of lignin phenolic acids, which appear to have an extra function in lignin metabolism. Ruminants are believed to be inhibited in their digestion of theoretically digestible carbohydrates due to the presence of lignin phenolic acids in their digestive tracts.

1.2.15 Soya protein On a dry basis, soybean proteins comprise around 38%e42% crude protein, 16%e20% triglycerides, and approximately 33% carbs. Put another way, soy proteins are the primary

14

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

derivatives of soybeans. They are produced from soybean meal that has been dehulled and defatted. Commercially available, high-protein soy is produced in three forms: soy flour, concentrated, and isolated. Soy proteins have lately been a focus of research for the potential health benefits of consuming them. Phytoestrogens included in soy protein have been linked to an increased risk of some types of cancer, according to research. So in the future, these proteins might be repurposed for uses other than foodstuffs [67].

1.2.16 Gum Heteropolysaccharide is either neutral or slightly acidic in pH and comprises 1, 3-linked -Dgalactopyranosyl units that are complicated and branching [68]. This polymer also contains the sugars L-arabinose, L-rhamnose, and D-glucuronic acid [69]. To make the side chains, the main chain has two to five 1, 3-linked -D-galactopyranosyl units attached by 1, 6linkages. Polysaccharides and glycoproteins are reportedly present in this gum, according to certain studies. Bright orange or white gum granules are water-soluble. Gum has been used since the Bronze Age, 5000 years ago. In Middle Eastern nations, it has long been considered a treatment for chronic renal disease [70]. Gum has found widespread use in the food sector because of its palatable nature, high water solubility, generally accepted safety status, absence of aftertaste, and other desired properties. Many culinary products use glycerin because of its ability to stabilize and thicken as well as its ability to bind. Examples of these products range from ice creams to chewing gum. Its film-forming characteristics make it an excellent choice for confectionery coatings and glazes.

1.2.17 Polyhydroxyalkanoates Polyhydroxyalkanoates (PHAs) are a kind of intracellular biopolymer that many bacteria produce as carbon and energy storage granules within their cells. Fermentation is the primary way PHAs are derived from biomass sources. PHAs make up 30% to 80% of the dry weight of a wide range of prokaryotic species [71]. When cells become deficient in a critical nutrient yet are exposed to an excess of carbon, biotechnological investigations have demonstrated that PHB is generated under balanced growth circumstances [72]. Different monomers and (co)polymers can be produced depending on the composition substrates and microbial metabolism [73]. PHAs are also ideal for short-term packaging since they are disposable. They are also noncytotoxic with tissues and may be utilized in biomedical applications. An enzymefree way to break down PHA is via simple hydrolysis of the ester link, which requires no additional catalysts. The enzymes in the biodegradation process break down the leftovers until they are completely mineralized (biotic degradation). A PHA’s chain length may be divided into two categories: short-chain-length (sCL-PHA) and medium chain-length. The difference between the two categories is the number of carbons in the monomer units.

1.3 Summary and future outlook According to investigations, natural polymer-based products have both difficulties and possibilities. To that end, researchers will continue to work on biomaterials’ well-known

References

15

flaws and moisture sensitivity. These concerns will be major focuses of future research. Modifications such as functionalization and chemical treatments for decreasing moisture sensitivity should be considered and balanced with biodegradability. Natural polymers are becoming increasingly popular, and they have shown much promise. Throughout the natural world, proteins have demonstrated their usefulness as structural elements. Scientists working in the tissue engineering field have noticed their outstanding qualities. For the past 2 decades, natural polymers have been the subject of several investigations. When considering a larger range of disposal options with a reduced environmental effect, developing these polymers (10%e20% each year) substantially contributes to sustainable development. Adequate legislative attention might serve as an additional incentive for the creation of biodegradable goods and optimize the environmental, social, and economic benefits they offer. Products of this caliber are only successful if strict quality requirements are met. Quality here refers mostly to environmental quality.

References [1] D. Gnanasekaran, Green Biopolymers and its Nanocomposites in Various Applications: State of the Art, 2019, pp. 1e27, https://doi.org/10.1007/978-981-13-8063-1_1. [2] C. Chassenieux, D. Durand, P. Jyotishkumar, S. Thomas, Biopolymers: State of the Art, New Challenges, and Opportunities, n.d. [3] J.D. Schiffman, C.L. Schauer, A review: electrospinning of biopolymer nanofibers and their applications, Polym. Rev. 48 (2008) 317e352, https://doi.org/10.1080/15583720802022182. [4] O. Faruk, A.K. Bledzki, H.P. Fink, M. Sain, Biocomposites reinforced with natural fibers: 2000-2010, Prog. Polym. Sci. 37 (2012) 1552e1596, https://doi.org/10.1016/j.progpolymsci.2012.04.003. [5] D.R. Paul, L.M. Robeson, Polymer nanotechnology: nanocomposites, Polymer 49 (2008) 3187e3204, https:// doi.org/10.1016/j.polymer.2008.04.017. [6] S. Sundar, J. Kundu, S.C. Kundu, Biopolymeric nanoparticles, Sci. Technol. Adv. Mater. 11 (2010) 014104, https://doi.org/10.1088/1468-6996/11/1/014104. [7] V.A. Fomin, V.V. Guzeev, Biodegradable polymers, their present state and future Prospects, Int. Polym. Sci. Technol. 28 (2001) 76e84, https://doi.org/10.1177/0307174x0102801120. [8] T. Jiang, Q. Duan, J. Zhu, H. Liu, L. Yu, Starch-based biodegradable materials: challenges and opportunities, Adv. Ind. Eng. Polym. Res. 3 (2020) 8e18, https://doi.org/10.1016/j.aiepr.2019.11.003. [9] A. Jiménez, M.J. Fabra, P. Talens, A. Chiralt, Edible and biodegradable starch films: a review, Food Bioprocess Technol. 5 (2012) 2058e2076, https://doi.org/10.1007/s11947-012-0835-4. [10] I. Arvanitoyannis, A. Nakayama, S.I. Aiba, Edible films made from hydroxypropyl starch and gelatin and plasticized by polyols and water, Carbohydr. Polym. 36 (1998) 105e119, https://doi.org/10.1016/S0144-8617(98)00017-4. [11] L. Yu, G. Christie, Microstructure and mechanical properties of orientated thermoplastic starches, J. Mater. Sci. 40 (2005) 111e116, https://doi.org/10.1007/s10853-005-5694-1. [12] F. Xie, P.J. Halley, L. Avérous, Rheology to understand and optimize processibility, structures and properties of starch polymeric materials, Prog. Polym. Sci. 37 (2012) 595e623, https://doi.org/10.1016/j.progpolymsci.2011.07.002. [13] C. Zinge, B. Kandasubramanian, Nanocellulose based biodegradable polymers, Eur. Polym. J. 133 (2020) 109758, https://doi.org/10.1016/J.EURPOLYMJ.2020.109758. [14] P. Kumar Gupta, S. Sai Raghunath, D. Venkatesh Prasanna, P. Venkat, V. Shree, C. Chithananthan, S. Choudhary, K. Surender, K. Geetha, An Update on Overview of Cellulose, its Structure and Applications, Cellulose, IntechOpen, 2019, https://doi.org/10.5772/intechopen.84727. [15] I. Younes, M. Rinaudo, Chitin and chitosan preparation from marine sources. Structure, properties and applications, Mar. Drugs 13 (2015) 1133e1174, https://doi.org/10.3390/md13031133. [16] K.B. Abdan, S.C. Yong, E.C.W. Chiang, R.A. Talib, T.C. Hui, L.C. Hao, Barrier properties, antimicrobial and antifungal activities of chitin and chitosan-based IPNs, gels, blends, composites, and nanocomposites, in: Handb. Chitin Chitosan, Elsevier, 2020, pp. 175e227, https://doi.org/10.1016/b978-0-12-817968-0.00006-8.

16

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

[17] S. Kaur, G.S. Dhillon, Recent trends in biological extraction of chitin from marine shell wastes: a review, Crit. Rev. Biotechnol. 35 (2015) 44e61, https://doi.org/10.3109/07388551.2013.798256. [18] A. Einbu, S.N. Naess, A. Elgsaeter, K.M. Vårum, Solution properties of chitin in alkali, Biomacromolecules 5 (2004) 2048e2054, https://doi.org/10.1021/bm049710d. [19] R. Harris, E. Lecumberri, I. Mateos-Aparicio, M. Mengíbar, A. Heras, Chitosan nanoparticles and microspheres for the encapsulation of natural antioxidants extracted from Ilex paraguariensis, in: Carbohydr. Polym, Elsevier, 2011, pp. 803e806, https://doi.org/10.1016/j.carbpol.2010.07.003. [20] T.G. Hoffmann, D.A. Peters, B.L. Angioletti, S.L. Bertoli, L.V. Péres, M.G. Ratto Reiter, C.K. de Souza, Potentials nanocomposites in food packaging, Chem. Eng. Trans. 75 (2019) 253e258, https://doi.org/10.3303/ CET1975043. [21] J.W. Rhim, P.K.W. Ng, Natural biopolymer-based nanocomposite films for packaging applications, Crit. Rev. Food Sci. Nutr. 47 (2007) 411e433, https://doi.org/10.1080/10408390600846366. [22] C.G. Otoni, R.J. Avena-Bustillos, H.M.C. Azeredo, M.V. Lorevice, M.R. Moura, L.H.C. Mattoso, T.H. McHugh, Recent advances on edible films based on fruits and vegetablesda review, Compr. Rev. Food Sci. Food Saf. 16 (2017) 1151e1169, https://doi.org/10.1111/1541-4337.12281. [23] V. Siracusa, P. Rocculi, S. Romani, M.D. Rosa, Biodegradable polymers for food packaging: a review, Trends Food Sci. Technol. 19 (2008) 634e643, https://doi.org/10.1016/j.tifs.2008.07.003. [24] K.M. Zia, S. Tabasum, M. Nasif, N. Sultan, N. Aslam, A. Noreen, M. Zuber, A review on synthesis, properties and applications of natural polymer based carrageenan blends and composites, Int. J. Biol. Macromol. 96 (2017) 282e301, https://doi.org/10.1016/j.ijbiomac.2016.11.095. [25] A. Nesic, G. Cabrera-Barjas, S. Dimitrijevic-Brankovic, S. Davidovic, N. Radovanovic, C. Delattre, Prospect of polysaccharide-based materials as advanced food packaging, Molecules 25 (2020) 135, https://doi.org/ 10.3390/molecules25010135. [26] Z. Mahcene, A. Khelil, S. Hasni, P.K. Akman, F. Bozkurt, K. Birech, M.B. Goudjil, F. Tornuk, Development and characterization of sodium alginate based active edible films incorporated with essential oils of some medicinal plants, Int. J. Biol. Macromol. 145 (2020) 124e132, https://doi.org/10.1016/j.ijbiomac.2019.12.093. [27] A. Abbaszad Rafi, M. Mahkam, Preparation of magnetic pH-sensitive film with alginate base for colon specific drug delivery, Int. J. Polym. Mater. Polym. Biomater. 64 (2015) 214e219, https://doi.org/10.1080/ 00914037.2014.936593. [28] S. Kim, S.K. Baek, K. Bin Song, Physical and antioxidant properties of alginate films prepared from Sargassum fulvellum with black chokeberry extract, Food Packag. Shelf Life 18 (2018) 157e163, https://doi.org/10.1016/ j.fpsl.2018.11.008. [29] R.G. Puscaselu, A. Lobiuc, M. Dimian, M. Covasa, Alginate: from food industry to biomedical applications and management of metabolic disorders, Polymers 12 (2020) 1e30, https://doi.org/10.3390/polym12102417. [30] F. Bagheri, M. Radi, S. Amiri, Drying conditions highly influence the characteristics of glycerol-plasticized alginate films, Food Hydrocolloids 90 (2019) 162e171, https://doi.org/10.1016/j.foodhyd.2018.12.001. [31] S. Shankar, L.F. Wang, J.W. Rhim, Preparations and characterization of alginate/silver composite films: effect of types of silver particles, Carbohydr. Polym. 146 (2016) 208e216, https://doi.org/10.1016/j.carbpol.2016.03.026. [32] K.B. Ayaz Ahmed, V. Anbazhagan, Synthesis of copper sulfide nanoparticles and evaluation of in vitro antibacterial activity and in vivo therapeutic effect in bacteria-infected zebrafish, RSC Adv. 7 (2017) 36644e36652, https://doi.org/10.1039/c7ra05636b. [33] S. Goel, F. Chen, W. Cai, Synthesis and biomedical applications of copper sulfide nanoparticles: from sensors to theranostics, Small 10 (2014) 631e645, https://doi.org/10.1002/smll.201301174. [34] S. Thomas, H.J. Maria, C.H. Chan, L.a. Pothen, Natural Rubber Materials Volume 1: Blends and IPNs, 2014. https://books.google.co.in/books?hl¼en&lr¼&id¼Me1cAgAAQBAJ&oi¼fnd&pg¼PA3&dq¼NaturalþRubber þMaterialsþ:þVolumeþ2:þCompositesþandþNanocomposites&ots¼ICQmz_Rbc5&sig¼47p8U0L1RHfwgkw YAXYgiU6D0UQ#v¼onepage&q¼Natural Rubber Materials %3A Volume 2%3A Composites a. (Accessed 14 October 2021). [35] W. Sainumsai, K. Suchiva, S. Toki, Influence of sulphur crosslink type on the strain-induced crystallization of natural rubber vulcanizates during uniaxial stretching by in situ WAXD using a synchrotron radiation, in: Mater. Today Proc, Elsevier, 2019, pp. 1539e1548, https://doi.org/10.1016/j.matpr.2019.06.179.

References

17

[36] J.A. Delcour, C. Bruneel, L.J. Derde, S.V. Gomand, B. Pareyt, J.A. Putseys, E. Wilderjans, L. Lamberts, Fate of starch in food processing: from raw materials to final food products, Annu. Rev. Food Sci. Technol. 1 (2010) 87e111, https://doi.org/10.1146/annurev.food.102308.124211. [37] H. Wieser, Chemistry of gluten proteins, Food Microbiol. 24 (2007) 115e119, https://doi.org/10.1016/ j.fm.2006.07.004. [38] C. Miralbés, Quality control in the milling industry using near infrared transmittance spectroscopy, Food Chem. 88 (2004) 621e628, https://doi.org/10.1016/j.foodchem.2004.05.004.  c, D. Horvat, Z. Jurkovic, G. Drezner, D. Novoselovic, K. Dvojkovic, The genotype effect on the ratio of [39] G. Simi wet gluten content to total wheat grain protein, J. Cent. Eur. Agric. 7 (2006) 13e18. https://jcea.agr.hr/en/ issues/article/307. (Accessed 14 October 2021). [40] G.A. Morris, H.A.S. Binhamad, Isolation and characterisation of pectin, in: Pectin Technol. Physiol. Prop, Springer, Cham, 2020, pp. 61e82, https://doi.org/10.1007/978-3-030-53421-9_4. [41] C.D. May, Industrial pectins: sources, production and applications, Carbohydr. Polym. 12 (1990) 79e99, https:// doi.org/10.1016/0144-8617(90)90105-2. [42] B. Brodsky, J. Baum, Structural biology: modelling collagen diseases, Nature 453 (2008) 998e999, https:// doi.org/10.1038/453998a. [43] S. Kim, P. Wong, P.A. Coulombe, A keratin cytoskeletal protein regulates protein synthesis and epithelial cell growth, Nature 441 (2006) 362e365, https://doi.org/10.1038/nature04659. [44] H. Tu, R. Yu, Z. Lin, L. Zhang, N. Lin, W.D. Yu, X.Y. Liu, Programing performance of wool keratin and silk fibroin composite materials by mesoscopic molecular network reconstruction, Adv. Funct. Mater. 26 (2016) 9032e9043, https://doi.org/10.1002/adfm.201603403. [45] Y. Iridag, M. Kazanci, Preparation and characterization of Bombyx mori silk fibroin and wool keratin, J. Appl. Polym. Sci. 100 (2006) 4260e4264, https://doi.org/10.1002/app.23810. [46] B. Chen, Y. Xing, W. Yu, H. Liu, Wool keratin and silk sericin composite films reinforced by molecular network reconstruction, J. Mater. Sci. 53 (2018) 5418e5428, https://doi.org/10.1007/s10853-017-1909-5. [47] S. Reichl, Films based on human hair keratin as substrates for cell culture and tissue engineering, Biomaterials 30 (2009) 6854e6866, https://doi.org/10.1016/j.biomaterials.2009.08.051. [48] A. Thonpho, P. Srihanam, Preparation and characterization of keratin blended films using biopolymers for drug controlled release application, Orient, J. Chem. 32 (2016) 1739e1748, https://doi.org/10.13005/ojc/320402. [49] H.W. Kwak, M. Shin, H. Yun, K.H. Lee, Preparation of silk sericin/lignin blend beads for the removal of hexavalent chromium ions, Int. J. Mol. Sci. 17 (2016) 1466, https://doi.org/10.3390/ijms17091466. [50] X. Hu, D. Kaplan, P. Cebe, Determining beta-sheet crystallinity in fibrous proteins by thermal analysis and infrared spectroscopy, Macromolecules 39 (2006) 6161e6170, https://doi.org/10.1021/ma0610109. [51] C.R. Chilakamarry, S. Mahmood, S.N.B.M. Saffe, et al., Extraction and application of keratin from natural resources: a review, 3 Biotech 11 (2021) 220, https://doi.org/10.1007/s13205-021-02734-7. [52] S. Limmatvapirat, C. Limmatvapirat, M. Luangtana-Anan, J. Nunthanid, T. Oguchi, Y. Tozuka, K. Yamamoto, S. Puttipipatkhachorn, Modification of physicochemical and mechanical properties of shellac by partial hydrolysis, Int. J. Pharm. 278 (2004) 41e49, https://doi.org/10.1016/j.ijpharm.2004.02.030. [53] H.J. Wang, L. Di, Q.S. Ren, J.Y. Wang, Applications and degradation of proteins used as tissue engineering materials, Materials 2 (2009) 613e635, https://doi.org/10.3390/ma2020613. [54] N. Somanathan, M.D. Naresh, V. Arumugam, R. Sanjeevi, Mechanism of failure of hydrolyzed casein films, Eur. Polym. J. 36 (2000) 2485e2490, https://doi.org/10.1016/S0014-3057(00)00030-6. [55] O. Abu Diak, A. Bani-Jaber, B. Amro, D. Jones, G.P. Andrews, The manufacture and characterization of casein films as novel tablet coatings, Food Bioprod. Process. 85 (2007) 284e290, https://doi.org/10.1205/fbp07030. [56] M.S. Latha, K. Rathinam, P.V. Mohanan, A. Jayakrishnan, Bioavailability of theophylline from glutaraldehyde cross-linked casein microspheres in rabbits following oral administration, J. Contr. Release 34 (1995) 1e7, https://doi.org/10.1016/0168-3659(94)00088-C. [57] M.S. Latha, A.V. Lal, T.V. Kumary, R. Sreekumar, A. Jayakrishnan, Progesterone release from glutaraldehyde cross-linked casein microspheres: in vitro studies and in vivo response in rabbits, Contraception 61 (2000) 329e334, https://doi.org/10.1016/S0010-7824(00)00113-X. [58] Y. Wang, F. Lopes Filho, P. Geil, G.W. Padua, Effects of processing on the structure of zein/oleic acid films investigated by X-ray diffraction, Macromol. Biosci. 5 (2005) 1200e1208, https://doi.org/10.1002/ mabi.200500140.

18

1. The state of the art of biopolymers-new challenges, opportunities, and future prospects

[59] R. Shukla, M. Cheryan, Zein: the industrial protein from corn, Ind. Crop. Prod. 13 (2001) 171e192, https:// doi.org/10.1016/S0926-6690(00)00064-9. [60] J. Dong, Q. Sun, J.Y. Wang, Basic study of corn protein, zein, as a biomaterial in tissue engineering, surface morphology and biocompatibility, Biomaterials 25 (2004) 4691e4697, https://doi.org/10.1016/j.biomaterials. 2003.10.084. [61] H.J. Wang, Z.X. Lin, X.M. Liu, S.Y. Sheng, J.Y. Wang, Heparin-loaded zein microsphere film and hemocompatibility, J. Contr. Release 105 (2005) 120e131, https://doi.org/10.1016/j.jconrel.2005.03.014. [62] D.I. Zeugolis, S.T. Khew, E.S.Y. Yew, A.K. Ekaputra, Y.W. Tong, L.Y.L. Yung, D.W. Hutmacher, C. Sheppard, M. Raghunath, Electro-spinning of pure collagen nano-fibres - just an expensive way to make gelatin? Biomaterials 29 (2008) 2293e2305, https://doi.org/10.1016/j.biomaterials.2008.02.009. [63] G.A. Di.Lullo, S.M. Sweeney, J. Korkko, L. Ala-Korkko, J.D. San Antonio, Mapping the ligand-binding sites and disease-associated mutations on the most abundant protein in the human, type I collagen, J. Biol. Chem. 277 (2002) 4223e4231, https://doi.org/10.1074/JBC.M110709200. [64] V. Pasangulapati, K.D. Ramachandriya, A. Kumar, M.R. Wilkins, C.L. Jones, R.L. Huhnke, Effects of cellulose, hemicellulose and lignin on thermochemical conversion characteristics of the selected biomass, Bioresour. Technol. 114 (2012) 663e669, https://doi.org/10.1016/j.biortech.2012.03.036. [65] J. Bidlack, M. Malone, R. Benson, Molecular structure and component integration of secondary cell walls in plants, Proc. Oklahoma Acad. Sci. 72 (1992) 51e56. [66] M.V. Ramiah, Thermogravimetric and differential thermal analysis of cellulose, hemicellulose, and lignin, J. Appl. Polym. Sci. 14 (1970) 1323e1337, https://doi.org/10.1002/app.1970.070140518. [67] J. Zhang, L. Jiang, L. Zhu, J.L. Jane, P. Mungara, Morphology and properties of soy protein and polylactide blends, Biomacromolecules 7 (2006) 1551e1561, https://doi.org/10.1021/bm050888p. [68] S. Patel, A. Goyal, Applications of natural polymer gum Arabic: a review, Int. J. Food Prop. 18 (2015) 986e998, https://doi.org/10.1080/10942912.2013.809541. [69] A. Shirwaikar, A. Shirwaikar, S. Prabhu, G. Kumar, Herbal excipients in novel drug delivery systems, Indian J. Pharmaceut. Sci. 70 (2008) 415e422, https://doi.org/10.4103/0250-474X.44587. [70] O. Nasir, A.T. Umbach, R. Rexhepaj, T.F. Ackermann, M. Bhandaru, A. Ebrahim, F. Artunc, D.S. Kempe, G. Puchchakayala, B. Siraskar, M. Föller, A. Saeed, F. Lang, Effects of gum Arabic (Acacia Senegal) on renal function in diabetic mice, Kidney Blood Press. Res. 35 (2012) 365e372, https://doi.org/10.1159/000336359. [71] L.L. Madison, G.W. Huisman, Metabolic engineering of poly(3-hydroxyalkanoates): from DNA to plastic, Microbiol. Mol. Biol. Rev. 63 (1999) 21e53, https://doi.org/10.1128/mmbr.63.1.21-53.1999. [72] L.G. Donaruma, in: Y. Doi (Ed.), Microbial Polyesters, VCH, New York, 1990, p. 156, https://doi.org/10.1002/ pola.1991.080290916. J. Polym. Sci. Part A Polym. Chem. 29 (1991) 1365e1365. [73] M. Zinn, B. Witholt, T. Egli, Occurrence, synthesis and medical application of bacterial polyhydroxyalkanoate, Adv. Drug Deliv. Rev. 53 (2001) 5e21, https://doi.org/10.1016/S0169-409X(01)00218-6. [74] J.A. Rippon, D.J. Evans, Improving the properties of natural fibres by chemical treatments, in: Handbook of Natural Fibres, Woodhead Publishing, 2020, pp. 245e321, https://doi.org/10.1016/B978-0-12-818782-1.00008-0.

C H A P T E R

2 Extraction and classification of starch from different sources: Structure, properties, and characterization Euis Hermiati1, 2, Dewi Sondari1 and Titi Candra Sunarti3 1

Research Center for Biomass and Bioproducts, National Research and Innovation Agency (BRIN), Bogor, West Java, Indonesia; 2Research Collaboration Center for Biomass and Biorefinery, BRIN-UNPAD, Sumedang, West Java, Indonesia; 3Department of Agro-Industrial Technology, Faculty of Agricultural Technology, IPB University, Bogor, West Java, Indonesia

2.1 Introduction Starch is an abundant polysaccharide that provides energy storage in green plants; it has become the cheapest energy source for humans. Starchy foods have been consumed by humans and their ancestors for thousands of years. Food, pharmaceutical, textile, and paper sectors all use starch. It is also used as feedstock for bioethanol and biodegradable plastics to substitute for gasoline and plastics derived from fossil fuels. Nonfood businesses are expected to have a greater demand for starch in the future than food industries [1]. Despite criticisms that using starch for energy and other materials would conflict with the need for starch for food, using starch for those products continues to be a focus of interest because starch is renewable and biodegradable and thus considered a green resource. Starch is tasteless, odorless, white in color, and present in the seeds, fruits, roots, tubers, stems, and leaves of green plants. Currently, maize (73%), tapioca (11%), wheat (9%), potatoes (6%), and others (2%e3%) are the sources of starch [1]. Tropical plants, such as cassava, yams, sweet potato, sago, and sorghum, are potential starch sources. However, only cassava that has been produced widely and gives significant contribution to the world starch production. The other plants make only small contributions for various reasons; for example, they are not widely cultivated, or their starch characteristics do not meet the properties required by established industries. Nevertheless, these starches might have unique properties for specific products. Starch can be extracted from plant tissues through various methods that

Handbook of Natural Polymers https://doi.org/10.1016/B978-0-323-99853-6.00012-7

19

© 2023 Elsevier Inc. All rights reserved.

20

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

basically consist of two processes. These processes are the disintegration of materials, for example, milling, grinding, crushing, shredding, and raspingdand mechanical separation based on sizes using screens or filters, or using weights through decantation or centrifugation. Starch molecules are biosynthesized in starch granules. Granules with different botanical origins have various sizes and shapes, as well as distributions within the plant tissue. The size of the granules may vary from 15 m)

30

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

FIGURE 2.5 Scanning electron micrographs of starches: (A) elephant yam, (B) new cocoyam, (C) sweet potato, (D) kudzu, (E) arrowroot, (F) sago, (G) taro, (H) yam bean, (I) cassava, (J) corn, (K) rice, (L) edible canna, (M) water yam, (N) potato and (O) lesser yam. Reproduce from S. Srichuwong, T.C. Sunarti, T. Mishima, et al., Starches from different botanical sources I: contribution of amylopectin fine structure to thermal properties and enzyme digestibility, Carbohydr. Polym. 60 (2005) 529e538. https://doi.org/10.1016/j.carbpol.2005.03.004.

starch granules are disklike, whereas B- (5e15 m) and C-5 m granules are spherical [3]. Some plants produce a normal size distribution, but a clear bimodal distribution of granule size was shown in all wheat cultivars [121]. Distribution of starch granule size is a very important characteristic, since it correlates to the chemical composition (such as the ratio of amylopectin to amylose) and physicochemical and functional properties of starch (gelatinization and pasting properties). In addition, the main identifying characteristic of a starch granule is the presence of birefringent structures. Fig. 2.7 shows the shape and size of starch granules from several botanical sources with the birefringence ability. Most native starch granules exhibit maltese cross when observed by using polarized light microscopy and show their birefringence ability. A strong interference cross through the hilum of a starch granule indicates an orderly,

31

2.4 Structure of starch

TABLE 2.2

Morphology and crystallinity of several sources of starch granules.

Granule Botanical sources of starch size (mm)

Shape

Type of crystallinity

Relative crystallinity (%) References

Oval, ellipsoid

A

24.5e25.4

[6,69]

Arrowroot (Maranta arundinacea)

35.1 þ 16.0 Oval, spherical

A

34.6 23.3 20.01

[98] [99] [100]

Banana (Musa spp.)

36e47 5.5e59

B B and C

31.94e34.06 33.2e38.6

[101] [102]

Barley (Hordeum vulgare)

17.18e18.56 Disc shape, spherical

A and C

22.30e24.85

[54,103,104]

36.2

[105]

35.8 43.30

[98] Our research [106]

Avocado (Persea americana) 35.1 seed

Breadfruit (Artocarpus altilis) 10e20

Oval Elongated, spheroidal

Spherical and segmented B

Cassava (Manihot utilissima) 23.2 þ 21.4 Round A 2e32 Round, bell-shaped, oval B A Cassava (Manihot esculenta) 5.65e7.64 stem Corn (Zea mays)

21.4 þ 6.2 6.9e19.23

Oval

A

Round, polygonal

A

31.0

[47,98]

B B

27.2

[13,98]

Edible canna (Canna edulis) 38.7 þ 30.2 Oval, elliptical 10e100 Oval

[15]

Elephant yam (Amorphophallus paeoniifolius)

17.6 þ 6.8

Polygonal

A

34.2

[98]

Jackfruit (Artocarpus heterophyllus) seed

6e13

Round, bell

A

31.7

[19,61,63,64]

Kudzu (Pueraria lobata)

19.9 þ 7.8

Round, polygonal

A

34.4

[98]

Lesser yam (Dioscorea esculenta)

4.9 þ 1.3

Polygonal

C

27.8

[98]

Litchi (Litchi chinensis) seed 3.01e10.18 9.52e50

Round, oval Oval, elliptical

A

28

[20,70,107]

Mango (Mangifera indica) seed

Smooth with some grooves

A

31.1

[67,107,108]

New cocoyam (Xanthosoma 20.7 þ 8.1 sagittifolium)

Spherical, polygonal

A

33.2

[98]

Oat (Avena sativa)

10e15

Polygonal

A

44.4

[109e111]

Oil palm (Elaeis guineensis) trunk

5e25 3e37

Oval, spherical, round

B A

[27,88]

Pineapple (Ananas comosus) stem

9.69

Polyhedral

A

[29,91]

11.4e59

(Continued)

32 TABLE 2.2

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

Morphology and crystallinity of several sources of starch granules.dcont’d

Granule Botanical sources of starch size (mm)

Type of crystallinity

Relative crystallinity (%) References

B B

29.8

[73,98,112]

A

37.1

[98,113]

Sago (Metroxylon sp.) trunk 34.3 þ 22.5 Oval, spherical 3.20e59.15 20e60

A A C

32.9 40.74

Our research [34,86,98]

Sorghum (Sorghum bicolor)

A

43

[53,114]

Shape

Potato (Solanum tuberosum) 42.3 þ 38.1 Oval, spherical 4e20 Round, oval Rice (Oryza sativa)

4.7 þ 1.4 2e10

5e27

Sugar palm (Arenga pinata) 10e100 trunk

Polygonal

Polygonal or spherical Round, oval

[37,87]

Sweet potato (Ipomoea batatas)

22.7 þ 11.4 Round, polygonal 2.9e4.8 Angular, round, polygonal, bell-shaped

A C

34.4

[76,98,115]

Taro (Colocasia esculenta)

5.3 þ 1.5

A

35.3

[98]

B

29.5

[98]

23.4e27.3

[50,116,117]

Polygonal

Water yam (Dioscorea alata) 33.8 þ 14.8 Rod like round Wheat (Triticum aestivum)

29e34 8e10

Yam (Dioscorea sp.)

15.52e30.47 Oval, polygonal

A and C

Yam bean (Pachyrhinus erosus)

7.7 þ 4.1

A

FIGURE 2.6

Large, lenticular, oval or A B spherical Small, round, irregular or polyhedral

Spherical, polygonal

[75,81] 36.0

[98]

(A) sago starch and (B) canna starch granules under light microscope.

2.4 Structure of starch

33

FIGURE 2.7 Shape, size, and birefringence ability of starches: (A) lesser yam, (B) elephant yam, (C) water yam, (D) taro, (E) new cocoyam, (F) canna.

spherocrystalline arrangement of the starch substance. The X-ray spectra of granular starches show that this orderly crystalline structure extends all the way down to the molecular level. Observing granular birefringence (Maltese cross) under polarized light can also be a useful tool for determining starch gelatinization behavior. Starch gelatinization is an endothermic process that, under particular heat and moisture conditions, causes the disruption of molecular orderliness within the starch granule, granular swelling, crystallite melting, loss of birefringence, viscosity development, and solubilization. Munoz et al. [122] found that loss of birefringence and swelling of starch granule was different for each starch source.

2.4.2 Molecular structures Starch granules are formed from two glucans, which are amylose and amylopectin. Amylose is a chain polymer of a-D-glucopyranosyl residues linked 1 / 4, and amylopectin is a branched glucan with side chains attached to the glucose residues at the 6-position (Fig. 2.8). Normal starch granules contain 70%e80% amylopectin, whereas waxy maize and rice contain almost 100% amylopectin. Amylomaize corn cultivars, which contain 50%e80% amylose, have been developed. Table 2.1 lists the ratio of amylopectin and amylose from different starch sources. The molecular weight of amylose ranges from 80,000 to 1,000,000 and varies by plant species, variety, and starch maturity. It has been reported that among the starches, potato amylose has the largest size, while cereal amyloses have smaller sizes [123]. Amylopectin dominates in a very large, highly branched molecule having molecular weights ranging from 107 to 109. The structures and average molecular weights of amylopectin vary with the botanical sources. An average of 15e30 glucose residues are present in shortchain branches, and the average short-chain length is 20e25 glucose units, according to

34

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

FIGURE 2.8

Molecular structure of amylose and amylopectin.

studies [124]. The branch point linkages account for 4%e5% of the total linkages [125]. Polymodal chain distributions of amylopectin have been reported by Hizukuri [124] and Koizumi et al. [126], but most amylopectin molecules have a trimodal distribution of chain lengths [127].

2.4.3 Crystallinity Native starch granules from different botanical sources have a crystallinity varying from 15% to 45%. Natural amylopectin crystallizes during biosynthesis as A-, B- or C-type polymorphs [128,129] as detected by X-ray diffractometry (Fig. 2.9). The A-type polymorph is generally found in most cereal, while the B-type polymorph is mostly found in the tuber and root starches. The C-type polymorph is believed to be a mixture of A- and B-type polymorphs and is characteristic of pea and other legume starches [131]. However, the primary reason for a plant’s formation of various crystal structures is unknown. Starches observed in Table 2.2 showed a broad range of X-ray crystalline polymorphic forms (A-, B- and Ctypes). The type of X-ray diffraction pattern has been classified based on the chain length

2.5 Functional properties of starch and their methods of analyses

35

FIGURE 2.9 X-ray crystalline types of granular starch. A-, B- and C-type diffraction patterns. Reproduce from H.F. Zobel, Starch crystal transformations and their industrial importance, Starch-Stärke 40 (1988) 1e7, https://doi.org/10.1002/star.19880400102, with permission from John Wiley & Sons-Books.

of amylopectin [1], as described in Table 2.3. In native starch granules, the amylose may be free or, as in cereal starches, where lipids (free fatty acids and/or lysophospholipids) formed lipid-complexed (V-type helix).

2.5 Functional properties of starch and their methods of analyses 2.5.1 Swelling and solubilization Swelling is one of the important functional properties of starch. It contributes to the viscosifying property of starch [132]. In most food systems, the swelling characteristic of the starch determines the pasting behavior and rheological properties of partially or fully swelled starch granules [133]. The swelling process involves interaction between starch molecules and water as well as heat. The process starts when water enters into the more amorphous regions of TABLE 2.3

Starch categories based on the X-ray diffraction.

Type

Botanical sources

Description

A

Cereal starch

Having amylopectin of chain length 23e29 glucose units

B

Tubers and amylose-rich starches

Having amylopectin of chain length 30e44 glucose units

C

Mixture of types A and B, legume starch

Having amylopectin of chain length 26e29 glucose units

D

Amylose

Present in swollen granules and formed upon gelatinization

36

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

starch granules, causing the granules to expand in both radial and tangential directions [134]. It occurs within a temperature range of 30e60 C and is reversible [135], and the swollen granules revert to their original shapes upon drying [4]. There is only minor swelling in this phase, which occurs in the granular regions where the intermolecular interactions are weakest, then rapid swelling occurs, reaching a maximum at the final stage [133]. This phase usually occurs at above 60 C and is irreversible [135]. Fig. 2.10 shows the swelling of potato starch granules observed under a hot stage-light microscope. Depending on the type of starch, different amounts and proportions of amylose and amylopectin are leached out from starch granules during the swelling process, and finally, the granules are dissolved into the aqueous medium when the disintegration temperature is reached [133]. The differences of botanical sources of starch cause differences in chemical structure and characteristics of starch granules which affect the swelling and solubilization properties of starch [3]. Besides that, the presence of other components such as protein and phospholipid at or near the surface of the granules [137], the sizes of the granules [138], and the presence of holes and channels in the granules [139] also affect the swelling behavior of the starch. Hydrogen bonds govern the stabilization of amylose’s double helices structure and amylopectin’s lateral chains. These hydrogen bonds are destroyed and replaced by water when the starch granules are hydrated and subjected to high temperatures [140]. The ability of starch granules to hydrate and swell is determined by the starch molecules’ ability to hold water through hydrogen bonding. Some experiments on the swelling behavior of starch using normal and waxy starches show that in normal starch, the amylose restricts the swelling and stabilizes the granular structure, while in waxy starch that contains almost 100% amylopectin, the granules hydrate easily, swell quickly, and rupture extensively, resulting in viscosity loss [132,133]. In the starch granules, the phospholipids might be in complex with amylose and together inhibit the water binding and swelling of the granules resulting in low swelling power and low viscosity even at high temperatures [133,140]. Starches with smaller amounts of proteins and lipids swell faster when heated than those with more protein and lipids [137]. Cereal starches, such as wheat, maize, barley, and rice, usually contain higher protein and lipids than tuber starch, such as potato, and root starch, such as tapioca. Therefore, the

FIGURE 2.10

The swelling of native potato starch granules at different temperatures for 15 min observed by hotstage light microscopy: (A) 25 C, (B) 68 C, (C) 90 C; bar 20 mm). Reproduce from W. Błaszczak, G. Lewandowicz, Light microscopy as a tool to evaluate the functionality of starch in food, Foods 9 (2020) 1e15, https://doi.org/10.3390/foods9050670, open access journal.

2.5 Functional properties of starch and their methods of analyses

37

swelling power of cereal starches is usually lower than that of tuber and root starches [137]. However, the effects of protein and lipid content of starch on swelling are less compared to the effects of the amylose content of the starch. Swelling is inhibited with high amylose content [137]. On the other hand, the high amylopectin level resulted in enhanced swelling power and viscosity at low temperatures [141]. The degree of polymerization of amylopectin affects starch swelling power. Amylopectin, with higher proportions of longer chains, tends to have higher swelling power [142]. Regarding the granule sizes, smaller granules have greater hydration and swelling capacity than larger ones [138]. Holes and channels in starch granules enable the water and ion molecules to enter the granules more easily, disrupt the amorphous region that contains amylose chains, lessen the restrictive effect, and increase hydration and swelling [143]. Swelling properties of starch also depends on processing condition, such as time and temperature, as shown by the granular mean diameter and size distribution of wheat starch granules that were heated at 30e90 C for 20 min [144]. Observation of the granule swelling of cowpea starch in the range of 30e86 C shows that in the range of 30e60 C the swelling of the starch granules is only slight, while at a temperature above the gelatinization temperature, the granules are much more swollen [135]. Similar results are obtained by Choi and Kerr [144]. They suggested that granule swelling in the temperature range of 30e50 C may be due to the sorption of water, while that between 60 and 90 C may be associated with starch gelatinization. An earlier study on starch swelling measurement is known as the Leach method. The ratio of the wet mass of the sedimented gel to its dry mass is used to calculate the swelling power. This method did not distinguish between intragranular water and intergranular or interstitial water, so the precision of measurements was not particularly good [133,145]. There were some improved methods for measuring a true starch swelling factor at certain temperature, which was only involving intragranular water, by using blue dextran dye exclusion method [133], microscopy [145e147], Coulter counter [133], and differential scanning calorimeter (DSC) [133]. The blue dextran dye exclusion method is based on the fact that enlarged granules do not allow the dye to penetrate. The swelling factor is the ratio of the volume of enlarged granules to the starch’s initial volume [145]. Another technique for measuring starch swelling is using light microscopy combined with a hot stage and an image analysis system, which can assess the advancement of the size and shape of starch granules heated at different temperatures [145,146]. By using this system, Munoz et al. [122] could identify three stages during the swelling process which related to the birefringence character of starches. Low granular swelling occurs at first, with little water absorption and 100% birefringence; secondly, gradual loss of birefringence occurs with the absorption of a substantial amount of water (about 50%); and eventually, complete granular swelling to equilibrium occurs. Compared to Leach and blue dextran methods, the analysis using light microscopy has the advantage that it can evaluate individual starch granules, while using the former provides only global estimates of the swelling of the total starch mass in the dispersion [145]. The swelling of starch could also be determined based on the number-average volumes of the granules using a custom-built pulse height channelyser connected to an Industrial Model D Coulter Counter [148]. With this system there is about 1% volume precision can be achieved [148]. The use of a laser diffraction particle size analyzer is also reported for the analysis of starch swelling [135,144]. This method provides information on the granule size distribution, mean diameter, standard deviation, and skewness and kurtosis of the distribution.

38

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

2.5.2 Gelatinization Gelatinization is another essential functional property of starch. As it is in the swelling process, the gelatinization of starch involves the interaction between starch granules and water. Gelatinization is a continuing process of starch swelling. Until a certain point, the swelling of starch is reversible. However, when the temperature is further increased, the starch granules will absorb more water, and this causes the loss of crystallinity and disruption of the granules and loss of birefringent character. This transition process is irreversible. The gelatinization of starch is described as the disruption of molecular order inside the granule, as well as all simultaneous and irreversible modifications that result in a change in its characteristics [149]. During gelatinization, starch crystallites melt, the granules lose their molecular order, structure, and birefringent property, and hence, the starch solubilizes simultaneously [150]. There are mainly four steps of the transition process during gelatinization: (1) swelling of granules, (2) leaching of carbohydrate material, primarily amylose, (3) formation of a three-dimensional starch network of leached material, and (4) interactions between granule remnants and the leached material [151]. At lower temperatures before gelatinization occurs, the energy absorbed by the starch granules induces the unfolding of amylopectin double helices as well as the rearrangement or formation of new bonds among molecules [152]. In this early stage of the gelatinization process, the starch component that has a major role is amylose. Meanwhile, new amylopectin crystallites that have different stabilities are formed. Starch gelatinization is not a sharp transition due to the granule polydispersity [153] and different kinds of loss-of-order transitions that occurred during the process [150]. Fig. 2.11 shows the phase transition during the gelatinization process of starch, from a crystalline to amorphous structure, and subsequent crystallization. Transition temperatures and gelatinization enthalpies in the paste, which are unique to each species, are important indicators that represent the gelatinization process [154]. The gelatinization temperature is the temperature at which granules lose their birefringence [155]. Thermal transitions of starch samples include To (onset temperature), Tp (peak of gelatinization temperature), and Tc (conclusion temperature), while DHgel is the enthalpy of gelatinization, which is calculated based on dry weight of the starch. The gelatinization of most starches occurs at a temperature range between 60 and 80 C [153]. High transition temperatures indicate a high degree of crystallinity, as well as granule structural stability and resistance to gelatinization [156]. Because enthalpy (DH) correlates positively with the percent starch crystallinity, more crystalline starches require more energy for gelatinization; for example, wheat starch, having relative crystallinity of 27.3%, has a lower enthalpy and gelatinization temperature than potato, rice, sweet potato, and corn starches, having relative crystallinities of 37.57%, 33.97%, 33.12%, and 32.6%, respectively [157]. The lower gelatinization temperature of wheat compared with those of other starches, such as corn, potato, cassava, and rice, is also reported [122,158]. Several factors influence starch gelatinization, and these can be clustered into two categories: raw materials properties and process parameters [149]. Raw material properties depend on the botanical source of the starch. The temperature range for gelatinization (phase transition) differs not just from granule to granule within a population of granules from the same source but also from botanical source to botanical source [150]. Different botanical sources resulted in different characteristics of starch granules, including the composition of amylose and amylopectin, morphology, molecular architecture, and molecular weight [149].

2.5 Functional properties of starch and their methods of analyses

39

FIGURE 2.11 A phase diagram depicting the state and phase transition of starch when a temperature profile is applied. When heated, starch undergoes a transition from a crystalline to an amorphous structure, followed by recrystallization when cooled and stored. AM, amylose; AP, amylopectin; Tg, gelatinization temperature. Reproduce from M. Schirmer, M. Jekle, T. Becker, Starch gelatinization and its complexity for analysis, Starch/Staerke 67 (2015) 30e41, https://doi.org/10.1002/star.201400071, with permission from John Wiley & Sons-Books.

Normal starch is easier to gelatinize than high-amylose starch [159]. Table 2.4 shows the gelatinization temperature and enthalpy of native starches from different kinds of botanical sources. Process parameters that could affect starch gelatinization include the starch-to-water ratio, time, temperature, mechanical energy, and other ingredients, such as salts, sugars, proteins, and lipids. Gelatinization of starch can be completed at a certain temperature and sufficient time [175]. The starch would be gelatinized completely only if it reaches a certain temperature, even if it is heated for an infinite time. When the temperature is kept constant, the gelatinization could proceed spontaneously with time [176]. Specific mechanical energy, such as during extrusion cooking, affects the gelatinization of starch due to the disruption of intermolecular hydrogen bonds by mechanical forces, which catalyzes the gelatinization process [177]. High pressure, such as in high-pressure processing (500e600 MPa, 15 min), induces gelatinization of starch by forcing the water to get into the starch granules so that the starch undergoes gelatinization at room temperature [172]. The properties of starch granules produced by pressureinduced gelatinization differ from those produced by heat-induced gelatinization. The former results in starch pastes and gels with unique functional properties due to limited granule swelling, lower amylose leaching, and better granule preservation [178]. A limited amount of water causes difficulty in accomplishing the gelatinization process of starch because there is not enough water to swell starch granules and access their internal structure for solubilization. The completion of gelatinization needs a minimum amount of water, which is called transitional water content [179]. The onset temperature (To) and temperature range of gelatinization shift to higher temperatures as the water content decreases [158]. The effect of salts on the gelatinization and rheological properties of starch, such as sago starch, is complex [180]. Their study reveals that sulfate ions increased gelatinization temperature and reduced

40

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

TABLE 2.4

Gelatinization temperature and enthalpy of starch of different botanical sources and types. Onset temperature/ To ( C)

Peak Conclusion temperature/ temperature/Tc Tp ( C) ( C)

Range/ Tc L To ( C)

Enthalpy/DH (J/g) References

Amaranth (Amaranthus sp.) (waxy)

66.7

70.2

75.2

8.5

16.3

[160]

Arisaema elephas tuber

62.7

69.8

78.3

15.6

12.1

[161]

Arisaema erubescens tuber

68.3

73.8

80.1

11.8

13.7

[161]

Arisaema yunnanense tuber

64.7

71.7

79.5

14.8

13.0

[161]

Bambarra groundnut (Voandzeia subterranean)

71.69

75.33

79.17

7.48

11.73

[162]

Banana (Musa sp.) (green)

66.4e68.6

69.8e72.0

74.0e76.1

7.5e7.6

15.8e17.2

[160,163]

Banana (Musa acuminata) 74.52

77.97

80.37

5.85

3.05

[164]

Banana (Musa sapientum) 73.64

76.98

80.69

7.05

7.76

[164]

Banana (Mysore)

75.18

87.56

20.02

12.38

[57]

Barley (Hordeum vulgare) 59.1e62.0

63.6e68.4

68.7e74.7

8.1e12.7

3.7e4.9

[55]

Barley (Hordeum vulgare) 56.3 (waxy)

59.5

62.9

6.6

10.0

[160]

Black bean (Phaseolus vulgaris)

62.0e66.9

69.9e76.5

82.8e84.2

16.1e20.8

12.1e12.9

[165]

Cassava/tapioca (Manihot esculenta)

56.56e63

62e71.29

69.1e77.12

10.67e14.7

[14]

Chickpea (Cicer arietinum)

63.44e63.70

68.69e70.30

73.84e81.39

Corn (Zea mays)

65.6e69.0

69.9e74.0

75.1e79.7

Corn (Zea mays) (low amylose)

62.00

67.35

73.52

Cowpea (Vigna unguiculata)

63.8e69.0

69.6e75.3

82.3e84.6

Dioscorea pyrifolia

71.51

75.05

78.25

Dioscorea opposite

68.10

79.76

Dioscorea alata

71.26

Dioscorea nipponica

Starch sources/types

67.54

10.14e17.95 10.68e22.14

[122,166]

11.2e12.7

[46]

8.44

[157]

14.7e15.4

[167]

6.74

3.86

[168]

92.03

23.93

3.00

[81]

74.33

82.11

10.58

3.58

[81]

70.09

77.63

85.18

15.09

0.64

[81]

Dioscorea bulbifera

71.63

75.98

81.23

9.6

2.05

[81]

Dioscorea septemloba

75.06

80.74

84.74

9.68

0.28

[81]

Dioscorea hispida

74.54

79.35

83.36

8.82

4.12

[80]

11.52

41

2.5 Functional properties of starch and their methods of analyses

TABLE 2.4

Gelatinization temperature and enthalpy of starch of different botanical sources and types.dcont’d Onset temperature/ To ( C)

Peak Conclusion temperature/ temperature/Tc Tp ( C) ( C)

Range/ Tc L To ( C)

Enthalpy/DH (J/g) References

Kidney bean (Phaseolus vulgaris)

66.57

73.58

78.46

11.89

7.46

[157]

Lentil (Lens culinaris)

60.7e63.0

66.1e69.6

76.1e78.7

15.4e15.7

12.6e13.3

[165]

Lotus (Nelumbo nucifera) 60.6 root

66.2

71.1

10.5

13.5

[160]

Millet (Panicum miliaceum) (normal)

64.6

70.5

77.4

12.8

9.6

[169]

Millet (Panicum miliaceum) (waxy))

71.1

77.9

82.3

11.2

10.8

[169]

Millet (Setaria italica) (normal)

65.1

71.0

76.3

11.2

6.6

[169]

Millet (Setaria italica) (waxy)

68.3

73.0

78.7

10.4

8.5

[169]

Mung bean (Vigna radiata)

56.3e59.2

67.0e67.8

79.9e80.8

e

13.7e15.3

[167]

Navy bean (Phaseolus vulgaris)

65.6e66.0

74.4e75.1

84.8e85.0

19.0e19.2

13.2e13.5

[165]

Oat (Avena sativa)

44.73e47.3

56.2e59.5

68.7e73.7

8.1e9.5

[170]

Oatchestnut (Castanopsis 60.38 sclerophylla)

64.01

74.62

14.24

9.465

[171]

Oil palm (Elaeis guineensis) trunk

57.4

67.3

72.6

15.2

62.5

[88]

Pea (Pisum sativum)

53.61

58.79

62.78

9.17

3.75

[172]

Potato (Solanum tuberosum)

64.64e66.66

67.32e70.17

71.13e74.80

e

15.54e17.85

[112]

Pinto bean (Phaseolus vulgaris)

72.0e72.5

75.0e75.5

80.5e81.0

8.0e9.0

15.4e16.2

[165]

Rice (Oryza sativa)

61.6e64.6

66.6e69.3

72.1e73.9

8.38e9.47

[52]

Rice (Oryza sativa) (waxy) 56.9

63.2

70.3

13.4

15.4

[160]

Rice (Oryza sativa) (sweet)

58.6

64.7

71.4

12.8

13.4

[160]

Sago (Metroxylon sp.)

59.0

70.1

78.7

19.7

16.5

[84]

Smooth pea (Pisum sativum)

60.8e61.6

66.9e67.4

73.4e74.5

12.6e12.9

10.8e13.8

[165]

Starch sources/types

(Continued)

42 TABLE 2.4

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

Gelatinization temperature and enthalpy of starch of different botanical sources and types.dcont’d Onset temperature/ To ( C)

Peak Conclusion temperature/ temperature/Tc Tp ( C) ( C)

Sorghum (Sorghum bicolor) (grain)

70.60e72.50

74.15e76.15

79.95e81.55

12.43e13.40

[53]

Sorghum (Sorghum bicolor) (sweet)

61.05e70.3

66.40e74.35

47.60e81.15

7.85e14.06

[53]

Sweet potato (Ipomoea batatas)

65.62

70.48

76.36

10.74

10.3

[157]

Taro (Colocasia esculenta var antiquorum)

66.1e66.94

74.36e74.7

77.9e78.96

11.8e12.02

13.4e13.98

[74,173]

Taro (Colocasia esculenta var esculenta)

67.2

74.1

78.6

11.3

12.2

[74]

Water chestnut (Eleocharis dulchis)

58.7

70.1

82.8

24.1

13.6

[160]

60.8e63.31

66.2e67.24

7.08e10.1

9.37e10.7

[157,174]

Starch sources/types

Wheat (Triticum aestivum) 56.1e60.16

Range/ Tc L To ( C)

Enthalpy/DH (J/g) References

the swelling properties, whereas iodide and thiocyanate ions reduced gelatinization temperature but increased the swelling properties. At higher salt concentrations, the gelatinization peak temperature increased to a maximum and then decreased. Sugars could increase the temperature of starch gelatinization because they bind with water and reduce its availability for starch gelatinization [181]. Sugars that have longer chain lengths delayed gelatinization more than did shorter-chain sugars [182]. Either 5, 6, or 12C sugars and sugar alcohols could increase the starch gelatinization temperature, and the gelatinization temperature increase with an increase in sugar concentration, which is due to the capacity of sugars to form growing numbers of intermolecular interactions with starch amorphous regions [183]. These interactions stabilize those regions, requiring more energy for gelatinization [182]. The gelatinization of starch and its associated properties can be determined using various methods, such as the birefringence end point, changes of viscosity, blue value (amyloseiodine binding), absorption of Congo red, enzymatic digestibility, light extinction, solubility or sedimentation of swollen granules, X-ray diffraction, NMR, and DSC [158]. Schirmer et al. [149] divided methods of analysis of the gelatinization process into rheological, calorimetric, and microscopic systems. In rheological methods, the analysis usually uses an empirical viscometer (RVA, amylograph, viscograph) or rheometer. The calorimetric method uses DSC, while the microscopic system uses hot-stage light microscopy or scanning electron microscopy (SEM). All of these methods measure slightly different physicochemical characteristics, and each has its own set of advantages and disadvantages. For example, the major

2.5 Functional properties of starch and their methods of analyses

43

drawback of empirical viscometers is that they are unable to determine the gelatinization properties of starch or food containing little or no water. However, the instrument can observe the change of viscosity that occurred during the gelatinization process and the effects of moisture, heat, and shear force on viscosity, which is important in industry, especially the food industry. Microscopic methods combined with a hot stage can show the process of starch granules swelling and the loss of birefringence during the gelatinization process. The gelatinization temperature is determined based on the end point of birefringence, which is a 98% loss of birefringence by the starch granules. A new method of microscopy, confocal scanning laser microscopy, enables observation of the changes within the starch granule from the three-dimensional angle during gelatinization [184]. By using this method, the crosssections of starch granules can be observed directly without destroying the sample, so it is very effective to study the mechanism of gelatinization simultaneously. The calorimetric method, such as using DSC, is beneficial for determining gelatinization temperature more precisely and the energy needed for gelatinization. However, it cannot show how the granules swell during gelatinization. As a result, it is critical to employ a variety of techniques in order to fully characterize starch gelatinization properties.

2.5.3 Retrogradation Starch retrogradation is a process in which a gelatinized starch solution is cooled for an extended period of time, causing it to thicken, change into a gel, and rearrange itself into a crystalline structure (granule) [185]. Recrystallization of amylose and amylopectin due to moisture migration in gelatinized starch causes the starch to be retrograde [4]. Retrogradation occurs when the molecular chains in gelatinized starches start reassociating in an ordered structure [151]. In the first step, amylose forms a double-helical association of 40e70 glucose units [186] and network through entanglements and/or junction zone formation, resulting in the formation of an elastic gel [150]. Meanwhile, amylopectin crystallizes by reassociation of the outermost short branches [187], which also may involve entanglements in a much slower process that may proceed for several weeks, depending on the storage temperature [150]. Amylopectin molecules can form weak gels in starches that do not contain amylose. The effect of retrogradation on starch can be beneficial (for the production of resistant starch) or detrimental (for example, causing staling of bakery products). Retrogradation of starch is quite complex and depends on many variables [4,188], for example, the granule size of starch [3], the concentration of starch [189], storage temperature and time [190,191], amylose content [192e194], phosphorus content [193], co-crystallization of amylose with amylopectin [195], the existence of nonstarch constituents, such as lipids [196], proteins [197], oligosaccharides [198], salts [199], sugars [200,201], and hydrocolloids [202]. Retrogradation behavior is also influenced by thermomechanical treatment, such as heat moisture [203], annealing [204], high hydrostatic pressure [188,205], and extrusion [206]. The molecular weight of starch polymer affects the retrogradation of soluble amylose, and amylopectin with higher molecular weight polymer causes faster retrogradation than lower molecular weight polymer [207]. Regular maize starch retrogrades slower than high amylose maize starch, which is likely due to the effects of long-term retrogradation of amylopectin and short-term retrogradation of amylose [188]. Low molecular sugars (glucose, sucrose,

44

2. Extraction and classification of starch from different sources: Structure, properties, and characterization

trehalose) can slow down the retrogradation of tapioca starch gels, with trehalose being the most effective inhibitor among those sugars [201]. However, besides the types and concentration of sugars, the role of sugars in starch retrogradation also depends on retrogradation conditions, especially water content and storage temperature [200]. Fructose significantly increased the rate of retrogradation across the range of water contents studied, and the increase was proportional to the sugar concentration, whereas xylose and sucrose did not. Both sugars accelerated starch retrogradation at 10% sugar concentration, whereas at 30% sugar content, xylose and sucrose accelerated the process at