Emerging Natural Hydrocolloids: Rheology and Functions

The first guide devoted to the functions, structures, and applications of natural hydrocolloids

In today’s health-conscious climate, the demand for natural food products is growing all the time. Natural hydrocolloids, therefore, have never been more popular. With their thickening, stabilizing, gelling, fat replacing, and binding qualities, these naturally occurring, plant-based polymers can fulfil many of the same functions as commercial ingredients like xanthan, guar, gum Arabic, pectin, and starch. Moreover, certain health benefits have been linked with their often biological active compounds and high-fiber compositions, including potential prebiotic effects and the reduction of blood cholesterol levels.

Application of these novel hydrocolloids is, however, still underexplored. Emerging Natural Hydrocolloids aims to remedy this by providing a thorough overview of their structure–function relationships, rheological aspects, and potential utility in mainly the food and pharmaceutical industries. This accessible, quick-reference guide features:  

• A comprehensive and up-to-date survey of the most significant research currently available on natural hydrocolloids
• Examinations of the major functions and rheological aspects of novel hydrocolloids
• Information on the potential applications of biopolymers within both foods and pharmaceutical systems
• Collaborations from an international team of food scientists

Emerging Natural Hydrocolloids: Rheology and Functions offers scientists, engineers, technologists, and researchers alike a unique and in-depth account of the uncharted world of novel hydrocolloids, their uses, properties, and potential benefits.

• Language: English
• Publisher: Wiley
• Release date: Feb 5, 2019
• ISBN: 9781119418542

Book preview

About the Editor

Seyed M.A. Razavi is currently a Professor at the Department of Food Science and Technology, Ferdowsi University of Mashhad (FUM), Iran. He received the BSc degree in Food Science & Technology from the Ferdowsi University of Mashhad, MSc degree in Food Process Engineering from the University of Tehran, and PhD degree in Food Physics & Engineering from the Ferdowsi University of Mashhad in collaboration with the University of Wales, Swansea. His research interests are mainly focused on food rheology and hydrocolloids with an emphasis on the biopolymers' functional properties, structure‐function relationships, and product formulation engineering. He is the founder and director of Food Hydrocolloids Research Center (FHRC) at FUM. He has authored or co‐authored over 250 peer‐reviewed papers, 6 book chapters, and 3 edited books. He is editor‐in‐chief of the Iranian Food Science and Technology Research Journal (IFSTRJ) and also serves as editor for several scientific journals. Prof. Razavi was named a highly cited author (top 1% globally) in Agricultural Sciences (2015, 2016, 2017, Web of Science) by ISI‐Thomson Reuters Scientific and has received several awards for his achievements in research, teaching, and scholarly works. Other details are available at http://profsite.um.ac.ir/∼s.razavi/index.htm.

List of Contributors

S. Abbasi

Food Colloids and Rheology Laboratory

Department of Food Science and Technology

Faculty of Agriculture

Tarbiat Modares University

Tehran

Iran

A. Alghooneh

Food Hydrocolloids Research Center

Department of Food Science and Technology

Ferdowsi University of Mashhad

Mashhad

Iran

F.M. Amoah

Cocoa Research Institute of Ghana

Akim‐Tafo

Ghana

G. Askari

Transfer Phenomena Laboratory (TPL)

Control Release Center

Department of Food Science

Engineering and Technology

College of Agriculture and Natural Resources

University of Tehran

Karaj

Iran

S. Bakhshizadeh‐Shirazi

Department of Food Science and Technology

School of Agriculture

Shiraz University

Shiraz

Iran

F. Behrouzian

Food Hydrocolloids Research Center

Department of Food Science and Technology

Ferdowsi University of Mashhad

Mashhad

Iran

M.A. Bertuzzi

Instituto de Investigaciones para la Industria Química

Universidad Nacional de Salta

Salta

Argentina

C. Carrara

Food Technology Institute

Chemical Engineering Department

National University of Litoral

Santa Fe

Argentina

Z. Emam‐Djomeh

Transfer Phenomena Laboratory (TPL)

Control Release Center

Department of Food Science

Engineering and Technology

College of Agriculture and Natural Resources

University of Tehran

Karaj

Iran

A. Farahnaky

School of Science

RMIT University

Bundoora West Campus

Melbourne

Australia

M. Fathi

Transfer Phenomena Laboratory (TPL)

Control Release Center

Department of Food Science

Engineering and Technology

College of Agriculture and Natural Resources

University of Tehran

Karaj

Iran

A. Golkar

Department of Food Science & Technology

Sari Agricultural Sciences and Natural Resources University (SANRU)

Sari

Iran

E. Gyedu‐Akoto

Cocoa Research Institute of Ghana

Akim‐Tafo

Ghana

M.A. Hesarinejad

Department of Food Processing

Research Institute of Food Science and Technology (RIFST)

Mashhad

Iran

F. Javidi

Food Hydrocolloids Research Center

Department of Food Science and Technology

Ferdowsi University of Mashhad

Mashhad

Iran

H. Karazhiyan

Department of Food Science & Technology

Torbat‐e Heydarieh Branch

Islamic Azad University

Torbat‐e Heydarieh

Iran

A. Koocheki

Department of Food Science and Technology

Ferdowsi University of Mashhad

Iran

P. Loyeau

Food Technology Institute

Chemical Engineering Department

National University of Litoral

Santa Fe

Argentina

M. Majzoobi

Department of Primary Industries

Wagga Wagga Agricultural Institute and Graham Centre for Agricultural Innovation

Wagga Wagga

NSW

Australia

J.M. Milani

Department of Food Science & Technology

Sari Agricultural Sciences and Natural Resources University (SANRU)

Sari

Iran

A. Mohammad Amini

Department of Food Science and Technology

Faculty of Agriculture

University of Kurdistan (UOK)

Sanandaj

Iran

S.F. Mousavi

Food Hydrocolloids Research Centre

Department of Food Science and Technology

Ferdowsi University of Mashhad (FUM)

Mashhad

Iran

S. Naji‐Tabasi

Department of Food Nanotechnology, Research Institute of Food Science and Technology (RIFST)

Mashhad

Iran

I. Oduro

Kwame Nkrumah University of Science and Technology

Kumasi

Ghana

M. Perduca

Engineering and Technological Faculty

Scientific Research Institute

Universidad de la Cuenca del Plata

Corrientes

Argentina

A. Rafe

Department of Food Processing

Research Institute of Food Science and Technology (RIFST)

Mashhad

Iran

Seyed M.A. Razavi

Food Hydrocolloids Research Center

Department of Food Science and Technology

Ferdowsi University of Mashhad

Mashhad

Iran

S. Razmkhah

GUM Group Knowledge Base Company

Technology Development Center

Ferdowsi University of Mashhad

Iran

A. Rubiolo

Food Technology Institute

Chemical Engineering Department

National University of Litoral

Santa Fe

Argentina

E. Salehi

Transfer Phenomena Laboratory (TPL)

Department of Food Science

Technology and Engineering

Faculty of Agricultural Engineering and Technology

Agricultural Campus of the University of Tehran

Karadj

Iran

A.M. Slavutsky

Instituto de Investigaciones para la Industria Química

Universidad Nacional de Salta

Salta

Argentina

M.J. Spotti

Food Technology Institute

Chemical Engineering Department

National University of Litoral

Santa Fe

Argentina

A.R. Yousefi

Department of Chemical Engineering

Faculty of Engineering

University of Bonab

Bonab

Iran

Y. Zahedi

Department of Food Science and Technology

Faculty of Agriculture and Natural Resources

University of Mohaghegh Ardabili

Ardabil

Iran

Preface

Hydrocolloids are finely divided particles dispersed in water with long‐chained polymeric systems. Depending on the quantity of the medium, namely, water, hydrocolloids exist as sols or as gels. Hydrocolloids are versatile ingredients with a wide range of functions and applications, especially in modifying the rheology and texture of complex fluids.

Natural hydrocolloids, as biological macromolecules (mainly polysaccharides and proteins), are frequently used in various industries as stabilizing, thickening, fat replacing, flavor and bioactive encapsulating, edible coating/film, plasticizing, emulsifying, carrier, binding, and gelling agents. Compared to synthetic and semi‐synthetic hydrocolloids, natural hydrocolloids have distinct advantages, such as being nontoxic, sustainable, renewable, biodegradable, biocompatible, eco‐friendly, cost‐effective, readily available, and capable of chemical modifications. Moreover, the demand for natural products is increasing among health‐conscious consumers. For example, the growing demand for functional foods and increasing public awareness about the importance of fiber in diet have increased the consumption of various biopolymers in food products. This has resulted in the tremendous growth of the global hydrocolloids market in different industry sectors.

In recent years, an ever‐growing interest has been devoted to finding new sources of natural hydrocolloid with interesting functions in the product matrix. Therefore, an extensive range of studies has focused on the characterization of new sources (mainly plant gum exudates and seed gums) of hydrocolloids, which could be potential substitutes for commercial gums. In fact, scientists, technologists, and industries over the world have paid special attention to emerging hydrocolloids, especially the natural ones, owing to their functional and nutraceutical properties.

Since the aim is to replace the existing commercial (semi‐synthetic and synthetic) hydrocolloids by the natural ones for various applications, one needs to find novel hydrocolloids that perform certain unique functions for this purpose. In order to introduce the potential and applicability of novel hydrocolloids in industries, it is necessary to explore emerging hydrocolloids with the desired properties. So, in this book, the recent scientific papers, theses, and research works about emerging hydrocolloids have been reviewed in detail. This book contains 24 chapters prepared by outstanding scientists who have made a significant impact on the field of emerging natural hydrocolloids. This comprehensive set provides an updated and highly structured material for researchers in food, paper, oil, textile, paint, and pharmaceutical fields. It is also a valuable compendium of recent scientific progress, along with the best‐known applications of hydrocolloids in the food industry, to be used by researchers and technologists. Moreover, novel opportunities and ideas for developing the emerging hydrocolloids are highlighted.

I sincerely hope that this comprehensive compilation of studies on emerging natural hydrocolloids in book form is useful to researchers in the field, and I welcome any suggestions to improve the book and additional information on this subject.

Seyed M.A. Razavi

1

Introduction to Emerging Natural Hydrocolloids

Seyed M.A. Razavi

Food Hydrocolloids Research Center, Department of Food Science and Technology, Ferdowsi University of Mashhad, PO Box: 91775‐1163, Mashhad, Iran

1.1 Introduction

Hydrocolloids, also known as gums, are a diverse group of long‐chain and hydrophilic polymers with high molecular weight which are readily dispersive, fully or partially soluble, and prone to swell in water, thus producing colloidal systems of different structures. Therefore, a hydrocolloid is a highly water‐soluble (or water‐dispersible) material that readily dissolves (or disperses) to form highly hydrated entities of colloidal dimensions (1–1000 nm) [1,2]. Hydrocolloids generally produce a dispersion, which is intermediate between a true solution and a suspension, and exhibit the properties of a colloid [3]. Each dissolved polymer molecule of a hydrocolloid ingredient is deemed to interact strongly via hydrogen bonding with its surrounding water molecules as well as with any neighboring hydrocolloid molecules. Due to the tendency of these large hydrophilic macromolecules to overlap and join together into entangled networks and macroscopic gels, most hydrocolloids have the capability to function as viscosity modifiers and thickeners in aqueous media at relatively low concentrations [4]. The presence of many hydroxyl groups in their structures conspicuously increases the affinity for binding water, rendering them hydrophilic. At sufficiently high concentrations, the hydrocolloids become entangled with each other, forming loose networks (gel) that change their rheological properties [5].

The term food hydrocolloid includes all the polysaccharides and proteins that are widely used in a variety of food processing sectors to control and regulate such a colloidal state. Food hydrocolloids are from various natural sources: agar and carrageenan are from seaweeds, guar gum and locust bean gum from plant seeds, pectin from citrus or apple peels, xanthan gum and gellan gum from microorganisms, and chitin and chitosan from animals [1]. Food hydrocolloids exhibit multiple functions in foods, including thickening, gelling, water holding, dispersing, stabilizing, film forming, and foaming, and have been used as a texture modifier in almost every kind of food product. Because of their interesting properties, food hydrocolloids are widely used as food additives to obtain particular functional properties [3]. In fact, food hydrocolloids are important parts of our daily diet in food systems such as yogurt, ice cream, cheese, mayonnaise and salad dressing, dessert jellies, bakery products, and so on [ 2,6]. The food industry especially has been using a large number of hydrocolloids in recent years as ingredients. Although they are often applied at low concentration (less than 1% of the final product), they significantly influence the textural, rheological, and sensory properties of the final products. These substances are best known as powerful thickeners but perform an extraordinary number of other functions essential to food quality. They impart food texture and structure, and they play a role in flavor release, appearance, and shelf stability [7,8]. They are actually not emulsifiers, because they lack the characteristic lipophilic and hydrophilic linkage in the molecular structure [9]. However, they can stabilize emulsions by increasing the viscosity of the continuous phase or by interaction with surface‐active substances. In recent years, food hydrocolloids have been recognized as healthy sources of fiber as well [10].

In general, hydrocolloids are natural‐origin biopolymers, but this does not mean that one cannot produce hydrocolloids through synthetic means. All kinds of hydrocolloids can be obtained from both renewable and non‐renewable resources. For many reasons, preference is being given to the renewable hydrocolloids. Due to the recent trends in the demand for all‐natural products by consumers, the aim is to replace the existing non‐renewable and synthetic hydrocolloids by renewable ones for different applications in industry, so we need to find novel natural hydrocolloids to provide certain unique features for the purpose. In order to introduce the novel hydrocolloids' potential and applicability in industries, it is necessary to explore the emerging natural hydrocolloids with the desired properties. In this chapter, some aspects of the hydrocolloids including hydrocolloid classification and functions are highlighted. In addition, a brief review of the chapters is presented at the end of this chapter.

1.2 World Market of Hydrocolloids

The global hydrocolloids market has been growing tremendously due to the increasing demand for healthy and natural products by health‐conscious consumers. Hydrocolloids are used in different industries, such as oil, food, paper, paint, textiles, and pharmaceuticals. The extensive range of functions exhibited by hydrocolloids in the industry is an important driving force in the market. The main reason for the widespread use of hydrocolloids in industry is their functions as stabilizing, thickening, binding, emulsifying, and gelling agents [11].

The world hydrocolloids market was valued at about 2100 MT (US$5.5 billion) in 2014. The value increased to about US$5.70 billion in 2015. The global market for hydrocolloids is projected to reach $7.9 billion by 2019 [12] and a value of US$8.5 billion by 2022 with a growing compound annual growth rate (CAGR) of 5.8% [11]. The base year considered for the study is 2014, and the forecast period is from 2015 to 2020. In 2013, the market was dominated by North America, followed by Europe. The Asia‐Pacific market is projected to grow at the highest CAGR with rapid growth in the food and beverage industries in developing countries, such as India and China. Increasing consumer awareness of health, diet, nutrition, and natural products is driving the market.

The market has been segmented on the basis of types, sources, functions, applications, and regions. The major types of hydrocolloids are gelatin, pectin, xanthan gum, and guar gum. On the basis of the hydrocolloid type, gelatin held the largest share in the food hydrocolloids market as it is widely used as a gelling agent in confectionary, meat, poultry, and dairy products. The market has been divided on the basis of natural sources, such as plant, seaweed, animal, microbial, and synthetic sources. On the basis of function, hydrocolloids have been segmented into thickeners, gelling agents, stabilizers, fat replacers, and coating materials. Dairy products have the largest food hydrocolloid applications. Hydrocolloids are extensively used in dairy and frozen products such as ice creams, milkshakes, and creams to maintain stability and increase the shelf life. The multifunctional characteristics of hydrocolloids, coupled with the growth in demand from the food and beverage industries, drive the hydrocolloids market. The market has also been divided on the basis of geographies, such as North America, Europe, Asia‐Pacific, and Rest of the World (RoW). Key participants in the supply chain of the hydrocolloids market are the manufacturers, end‐use industries, and raw material suppliers. The leading players involved in the hydrocolloids market include Cargill Incorporated (United States), Ingredion Incorporated (United States), E. I. du Pont de Nemours and Company (United States), Darling Ingredients Inc. (United States), Kerry Group plc (Ireland), CP Kelco (United States), Ashland Inc. (United States), DuPont (United States), Hawkins Watts (Australia), Royal DSM (the Netherlands), Archer Daniels Midland Co. (United States), Fuerst Day Lawson Limited (United Kingdom), E.I. Dupont De Nemours and Company (United States), Lucid Colloids Ltd. (India), and Danisco A/S company (Denmark). These market players have been focusing on the expansion of new facilities and launching new products [ 11, 12].

According to an IHS Markit report, native (unmodified) and modified starches account for the great majority (95%) of the market by weight; smaller‐volume, higher‐priced materials such as gelatin, guar gum, casein, xanthan gum, gum Arabic, and carrageenan make up the remainder [13]. The world consumption of hydrocolloids, including starches in 2015, is shown in Figure 1.1. As is seen, Asia was responsible for 60% of total hydrocolloid consumption, with China alone accounting for almost half (46%) of the demand. In contrast, the Americas and EMEA (Europe, the Middle East, and Africa) accounted for the bulk of consumption in the (much smaller) non‐starch hydrocolloid market. Together, the Americas and EMEA consumed 60% of non‐starch hydrocolloids.

Horizontal bar chart of world consumption of hydrocolloids in 2015, with 33.75 % in EMEA, 31.32% in North America, 16.18% in other Asia/Oceania, 8.96% in Central/South America, 5.71% in Japan, and 4.1% in India.

Figure 1.1 World consumption of hydrocolloids in 2015 (EMEA means Europe, the Middle East, and Africa regions).

China will drive future market growth. In 2020, China is expected to account for 70%–75% of the increase over 2015 market volumes. Chinese hydrocolloid consumption is expected to rise by 5.0% per year through 2020, exceeding the world average annual growth rate of just over 3%. All other regions expect slower growth. In North America, Central and South America, EMEA, and Japan, consumption will increase at low rates (0.4%–2.0% per year); in India and Other Asia and Oceania, consumption will grow at a moderate pace (2.4%–3.0% per year). Paper and board production is the largest end use for starches. They serve as binders, sizing, and coating agents in the paper‐making process; starch‐based adhesives are essential to the manufacture of corrugated cardboard, paper bags, and envelopes. Food applications are second in importance for starches, but they represent the single most important end use for many other hydrocolloids. Pectin serves as a gelling agent in jams, jellies, and marmalades; gum Arabic inhibits sugar crystallization in soft drinks; locust bean gum maintains ice cream's creamy texture by controlling ice crystal formation, to give just a few examples. The hydrocolloid market has a reputation for volatility, but this is somewhat undeserved. Raw materials for various hydrocolloids are periodically in short supply as a result of weather or political disruptions, but only guar gum has experienced major fluctuations in supply and demand in recent years. In this case, demand for guar gum surged because of the dramatic expansion of hydraulic fracking activity in the United States. The collapse of crude oil prices at the end of 2014 led to a reduction in drilling activity and lower consumption of guar gum. Additionally, in the food sector, processors have reformulated many products, replacing guar gum with other hydrocolloids. In the energy sector, the use of guar‐free slickwater fluids as cost‐effective alternatives to guar‐thickened fracking fluids is increasing. The overall demand for hydrocolloids will track growth in major end‐use industries, including paper, food, oil and gas production, and pharmaceuticals [13].

1.3 Hydrocolloids Classification

Hydrocolloids could be categorized according to their origins, chemical structure and composition, chemical nature (ionic and non‐ionic), and functional properties. Hydrocolloids, depending on their origin, may be classified as natural, semi‐synthetic, and synthetic. The natural hydrocolloids are hydrophilic biopolymers of plant, animal, and microbial origin. The plant‐derived hydrocolloids are mainly used to stabilize oil‐in‐water emulsions, but the animal‐derived hydrocolloids generally form water in oil emulsions. They are quite likely to cause allergies and are susceptible to microbial growth and rancidity. The semi‐synthetic hydrocolloids are those synthesized by modification of naturally occurring hydrocolloids. Starch and cellulose derivatives such as methylcellulose (MC), carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), microcrystalline cellulose (MCC), acetylated starch (AS), phosphorylated starch (PS), and hydroxypropylated starch (HPS) are the examples of the semi‐synthetic hydrocolloids. The semi‐synthetic hydrocolloids are stronger emulsifiers, are non‐toxic, and less likely to undergo microbial growth. Synthetic hydrocolloids are the ones that are completely synthesized in industries starting with petroleum‐derived base materials. These are basically derived from chemical combinations to give a product having a structure similar to the natural polysaccharides. The acrylate copolymers, carboxyvinyl polymers (Carbopol), polyethylene oxide polymers (Polyox), and polyvinylpyrrolidone (PVP) are examples of synthetic hydrocolloids [ 2, 5,14]. The synthetic hydrocolloids are the strongest emulsifiers, and they do not support microbial growth, but their cost may be prohibitive. The synthetic hydrocolloids are mainly limited to use as oil‐in‐water emulsifiers. Semi‐synthetic hydrocolloids are preferred to the purely synthetic gums. The literature has shown that the synthetic hydrocolloids are far more inefficient and have the following inherent disadvantages:

High cost

Toxicity to the body and other animal life

Environmental pollution during the manufacturing process

Non‐renewable sources

Acute and chronic adverse effects on the skin in some cases

Poor biocompatibility compared to the natural gums

Synthetic hydrocolloids offer certain advantages over their natural counterparts, such as increased potency, resistance to microbial degradation, and solution clarity. Compared to synthetic and semi‐synthetic polymers, the natural hydrocolloids are the most preferred in all the industries due to the following distinct advantages:

Cost‐effective and inexpensive.

Readily available, easy to handle, and they are also easier to extract.

Biodegradable; they are renewable sources which are easily biodegradable.

Biocompatible.

Capable of physical and chemical modifications.

Non‐toxic to the body.

Sustainable, eco‐friendly, and easily available in nature.

They have more public acceptance due to their numerous health benefits, and they are also extracted from edible sources.

In pharmaceutical applications, there is less chance of side effects to patients compared to synthetic hydrocolloids.

On the other hand, the growing demand for ready‐made meals and increasingly public awareness about the importance of fiber in the diet has increased the consumption of various biopolymers in food products. However, the naturally occurring plant hydrocolloids have the disadvantages of being required in large quantities to be effective as emulsifiers (compared to semi‐synthetic or synthetic ones) and are susceptible to microbial growth. With all these advantages and disadvantages, the natural hydrocolloids are gradually replacing synthetic gums in industrial applications.

Another classification of food hydrocolloids is based on their chemical structure. For example, guar gum, tara gum, locust bean gum, and fenugreek gum are galactomannan. Other structure‐based groups are glucan (starch, curdlan, and so on), fructan (inulin), xylan, rhamnan, glucomannan (alginate), arabinoxylan (flaxseed gum), galactan (agar, carrageenan), arabinogalactan (gum Arabic), galacturonan (pectin), glycano‐rhamnogalacturonan, glycano‐glycosaminoglycans, glucosamine polymer (chitin, chitosan), and protein (gelatin).

1.3.1 Natural Hydrocolloids

The natural hydrocolloids may originate from proteins or carbohydrates as they are the two main macromolecules that are naturally available. These two macromolecules are the major foods for human beings and are consumed every day. Human beings mainly derive their food from the plants, as various parts of a plant (seed, stem, root, leave, flower, fruit, etc.) are edible. The classification of hydrocolloids into proteins and carbohydrates is the classification based on their chemistry but in fact, the natural hydrocolloids are categorized based on their origin. As shown in Figure 1.2, the classification of commercially important hydrocolloids is (1) botanical, (2) algae, (3) microbial, and (4) animal sources [ 1,15]. Cellulose (trees origin), gum Arabic, gum karaya, gum ghatti, gum tragacanth (exudate gums), starch, pectin, cellulose (plants source), guar gum, locust bean gum, tara gum, (seed endosperm flour), konjac gum (extracted from tubers), fenugreek seed gum, mustard seed gum, and flaxseed gum (mucilage) are overall grouped under botanical sources. Agar, carrageenan (red seaweeds), and alginate (brown seaweeds) are classified as of algal origin. Microbial sources are included as xanthan gum, curdlan, dextran, gellan gum, and cellulose. Gelatin, caseinate, whey proteins, and chitosan are natural hydrocolloids belonged to the animal group. Nowadays, the demand for hydrocolloids from plants (e.g., plant cell walls, tree exudates, seeds, seaweeds) is greater than those from animals (hyaluronan, chitin, chondroitin sulfate) because of more benefits and a consumer‐friendly image.

Illustration 2 trees and a crab depicting source of natural hydrocolloids in nature, with boxes indicating microorganism, seeds, fruits, seeds , animals, tree exudates, tree pulps, root , and seaweeds.

Figure 1.2 Source of natural hydrocolloids in nature.

Source: Adapted from Funami [2011] with permission from Elsevier.

Hydrocolloids from seeds are the major source of natural gums. In general, seed gums are derived from ground endosperm of seeds. They are highly viscous at low concentrations [16]. Collection and processing of seed gums include the drying and crushing of harvested pods to separate seeds from pod husk. The seeds are dehulled, and the germ is separated from the endosperm. The pieces of endosperm are then ground to the required particle size to furnish the gum. Further processing involves either chemical modification of the gum or blending with other gums to produce a final product (food additive) with a range of physical and functional properties designed to suit end‐user requirements.

One of the most promising sources of plant hydrocolloids is mucilaginous substances. Mucilage is a heterogeneous branched and hydrophilic polysaccharide which forms a thick and sticky solution when dissolved in water. Mucilage is generally produced in the seeds, buds, and leaves of many plants. In seeds, it is presumed that the mucilage is located in the outer cells that form the seed coat, called mucilaginous cells, and can be easily removed after hydration. The seed coat or testa is composed of three layers: an outer layer, formed by rectangular thin‐walled cells, where presumably the mucilage is localized; a scleroid layer of long and thin cells resembling fibers, and the endocarp, a thin and inner layer. Tamarind seed, mustard seed, chia seed, fenugreek seed, and flaxseed are the well‐known sources of seed mucilage. When this seed is hydrated, the mucilage is exudated, and spiral filaments (mucilage fibers) become apparent. These filaments begin to expand until fully stretched to achieve maximum hydration, and new structures on the seed surface become apparent. These new structures, called columella, have a volcano‐shaped conformation and are uniformly distributed on the surface. When the mucilage is fully hydrated, it forms a transparent capsule surrounding the seed that adheres to it with great tenacity, and when many seeds are hydrated in water, a highly viscous solution is formed. The mucilage hydrocolloids have attractive functional properties such as stabilizing, thickening, water absorption capacity, emulsifying and foaming properties, and high solubility in cold and hot water and show promise for incorporation into different food formulations.

Plant/tree exudates from various plant species are obtained as a result of tree bark injury. They are normally collected as air‐dried droplets with diameters from 2 to 7 cm. Plant exudates are generally excreted from tree species belonging to families of Burseraceae, Mimosaceae, and Sterculiaceae, which grow in the wild. Almost all the existing gum‐bearing trees grow naturally in the wild under arid, warm or hot, unorganized, and rugged topographic conditions. This type of gum includes gum Arabic, karaya, tragacanth, and cashew gum [17]. Exudates from the stem and branches of a tree are produced as large nodules during a process called gummosis to seal wounds in the bark of the tree. The major commercial processes involved in the production of these plant exudates are collection, sorting, processing, quality control, and end‐user marketing [18]. They are mostly not processed in countries of production but are exported to overseas markets for processing. Gums are produced by exudation from trees resulting from natural damage on the trees by natural agents or individuals and animals on a casual basis [17]. Several techniques are now being used to produce gum artificially to guarantee viability and improvement of the quality of the commercial product. These techniques involve systematically controlled tapping and collection procedures. Exudate gums could be graded physically based on their color, size, and brightness. They could also be graded in terms of solubility, viscosity, bark and foreign matter (BFOM) and total ash content [19]. All this grading could be done when the gum is in its natural as well as powdered forms. The quality of gum is usually assessed by its moisture content, optical rotation, and the level of foreign matter. Gum Arabic, for instance, must have a moisture content between 12% and 14%, optical rotation between −25 and −35, and foreign matter must be less than 3%–5%. Also, the microbiological count for Salmonella, Escherichia coli, and Staphylococcus aureus must be negative [20].

Seaweed gums are gelatinous products isolated from seaweed, mainly red and brown algae, by hot water or an alkali extraction process followed by drying or isolate precipitation. Industrial gums extracted from seaweeds fall into three categories: alginates (derivatives of alginic acid), agars, and carrageenans. The first is extracted solely from brown seaweeds, while the last two are extracted only from red seaweeds. There are a number of artificial products reputed to be suitable replacements for seaweed gums, but none have the exact gelling and viscosifying properties of seaweed gums, and it is very unlikely that seaweeds will be replaced as the source of these polysaccharides in the near future [21].

Microbial hydrocolloids are extracellular polysaccharides which originate from microorganisms produced from nutritive media. The major types of microbial hydrocolloids include xanthan gum, which accounts for over 90% of the overall microbial hydrocolloids market. Other types of microbial hydrocolloids include pullulan and gellan gums. Xanthan gum is one of the microbial gums permitted for use in foods. It has many interesting properties such as high viscosity at low shear rates and yield stress [21].

Animal hydrocolloids commonly originate from the bones and skins of animals such as swine and cattle. The major types of animal hydrocolloids include gelatin, which accounts for approximately 99% of the overall animal hydrocolloids market. Other animal hydrocolloids include chitin, chitosan, whey proteins, and caseins. Semi‐synthetic hydrocolloids, also known as chemically modified hydrocolloids, include sodium caseinate and derivatives of several other types of animal hydrocolloids.

Table 1.1 Functions of hydrocolloids in food and non‐food systems.

1.4 Functions of Hydrocolloids

Natural hydrocolloids as biological macromolecules are frequently applied in food and pharmaceutical industries due to their excellent functional properties. Hydrocolloids perform various interesting functions in a formulation including thickening and gelling aqueous solutions; stabilizing/emulsifying foams, emulsions, and dispersions; inhibiting ice and sugar crystal formation; controlled release of flavors; flocculation; film formation, plasticization, fat replacement, biological active encapsulation, edible coating formation, carrier, and binding [ 1 22–24]. The most used commercial hydrocolloids in the food industry, as well as their functions, are listed in Table 1.1. It can be seen that these compounds are usually used in food systems depending on their functional properties, for example, as thickener (soups, gravies, salad dressing, and topping), gelling agent (puddings and jellies), emulsifier (ice cream, yogurt, and butter), stabilizer (ice cream, mayonnaise, and sauces), fat replacer (meat and dairy products), clarifying agent (beer and wine), flocculating agent (wine), clouding agent (juice and soft drinks), whipping agent (beer, whipped cream, and cake), coating agent (confectionary and fried foods), suspending agent (chocolate milk), anti‐staling agent (breads and batters), water binding agent (gluten‐free foods), encapsulating agent (powders' flavors), and crystallization inhibitors (ice cream and sugar syrups) [ 1, 2]. From the viewpoint of compatibility, some hydrocolloids may be used in combination for obtaining better properties. Also, some hydrocolloids have a synergistic effect in mixture form with other hydrocolloids (e.g., xanthan gum in combination with galactomannans such as locust bean gum).

The functional characteristics of natural hydrocolloids considerably depend on their physicochemical properties such as molecular weight, chemical composition, the sequence of monosaccharide, conformation, configuration, the position of glycoside linkage, particle size, hydrodynamic volume (intrinsic viscosity), and so on [106,107].

Hydrocolloids can dramatically alter the viscosity of many times their own weight of water due to their interactions with the water molecules through hydrogen bonding. There are two rheological properties which are of major importance in hydrocolloid science and technology: gel (viscoelasticity and texture) and flow (shear thinning and thixotropy) properties. A clear understanding of the rheological behavior of hydrocolloids has emerged over the last 20 years, which has led in turn to the exploitation of commercial hydrocolloids in various industries. The viscosity of a biopolymer solution shows a marked increase at a critical polymer concentration, commonly referred to as the critical concentration (C*). This corresponds to the transition from the dilute region, where the polymer molecules are free to move independently in solution without interpenetration, to the semi‐dilute region, where molecular crowding occurs which gives rise to the overlapping of polymer coils, thus causing interpenetration. The structural characteristics of hydrocolloids and their interaction with water (solvent) affect the rheology of hydrocolloids, leading to thickening, gelling, and so on. It is generally found that [14]:

The hydrodynamic size of biopolymer molecules in solution is significantly influenced by its molecular structure. Linear and stiff molecules have a much larger hydrodynamic size than highly branched flexible polymers with the same molecular mass, and thus they give rise to higher viscosity values.

Hydrocolloids stabilize emulsions primarily by increasing the viscosity of the system. They also act as emulsifiers, wherein the emulsification ability is reported to be mainly due to accompanying protein moieties.

Hydrocolloids form gels when the intra‐ or intermolecular hydrogen bonding is favored over hydrogen bonding to water.

The charged polymers or polyelectrolytes exhibit very high viscosity as compared to the non‐ionic polymers of similar molecular mass.

On the whole, it can be concluded that the rheological properties of hydrocolloids form the basis for their wide functions and applications in industries and also that the unique rheological behavior of the hydrocolloids can be attributed to the presence of a large number of hydroxyl groups in their structure, which leads to their H‐bonding interactions in aqueous systems. During the last decades, the search for new sources of natural hydrocolloids and their characterization have been the subject of invaluable studies due to the need for novel and/or improved functional properties. So, in recent years, several important studies have been published on the characterization and functional properties of emerging hydrocolloids for application in various food systems. On the basis of recently published works, some of the emerging natural hydrocolloids and their functions in the food and non‐food systems are addressed in Table 1.2.

Table 1.2 Some emerging hydrocolloids and their functions (2007–2017).

1.5 Overview of the Chapters

In this book, recent papers, theses, and research works about some emerging hydrocolloids have been reviewed in detail. The following paragraphs aim to provide a brief overview of the chapters for the readers.

1.5.1 Chapter 2: Dilute Solution Properties of Emerging Hydrocolloids

In this chapter, the dilute solution properties of novel hydrocolloids have been discussed. The viscosity behavior of macromolecular substances in the dilute regime is one of the most frequently used approaches to determine its specification. In dilute solution, it is assumed that macromolecule chains are separated without intermolecular interactions. Investigation of molecular properties such as macromolecule–solvent interaction, macromolecule–macromolecule interaction, molecular weight, molecular shape, and conformation seems to be useful for understanding and controlling the behavior of a hydrocolloid in dilute solution under different conditions. Intrinsic viscosity [η] is a measure of the capability of a polymer in solution to increase the viscosity of the solution. Much information on the fundamental properties of a solute and its interaction with a specific solvent can be obtained by determination of the intrinsic viscosity. In this chapter, the dilute solution properties of some emerging natural hydrocolloids like basil (Ocimum basilicum L.) seed gum, cress (Lepidium sativum) seed gum, sage (Salvia macrosiphon) seed gum, Balangu (Lallemantia royleana) seed gum, Qodume Shirazi (Alyssum homalocarpum) seed gum, Qodume Shahri (Lepidium perfoliatum) seed gum, chia seed gum, canary seed starch, hsian‐Tsao leaf gum, and so on, under various conditions (temperature, pH, salts, sugars) have been investigated. Finding interactions between hydrocolloids and solvent/cosolutes helps food researchers and manufacturers to understand the functional properties of these hydrocolloids in different food systems.

1.5.2 Chapter 3: Steady Shear Rheological Properties of Emerging Hydrocolloids

This chapter aims to give an idea about how to use steady shear rheological measurements to identify the important structure‐related characteristics of biopolymers and enables the reader to compare the rheological properties of various hydrocolloids and select the most appropriate hydrocolloid for their specific usage. For this purpose, a number of rheological tests were applied in the steady shear mode to describe the flow characteristics of two novel gums (sage seed gum [SSG] and cress seed gum) and three commercial gums (xanthan gum, guar gum, and pectin) dispersions. Various methods were used to quantify the thixotropic behavior of the selected gums, that is, hysteresis loop, shear stress decay, in‐shear structural recovery, and time‐dependency of steady shear properties. In addition, the static yield stress, dynamic yield stress, difference between yield stress at short and long time scales, and the corresponding time intervals were investigated. In order to categorize the hydrocolloids, the hierarchical clustering technique (HCT) and principal component analysis (PCA) were employed in serial mode. These data allow researchers to know the most critical parameter in the clustering of hydrocolloids.

1.5.3 Chapter 4: Transient and Dynamic Rheological Properties of Emerging Hydrocolloids

In a steady shear flow test, the flow properties of all fluids, regardless of whether or not they exhibit elastic behavior, are a concern. However, much of the rheological behavior of food products cannot be described by viscosity function alone, and elastic behavior must also be taken into consideration. Experiments involving the application of unsteady state deformations, such as transient and oscillatory tests, are implemented to generate data that reflect both the elastic and viscous characters of materials. These tests can be implemented in linear and nonlinear regions. This chapter focuses on a number of new viscoelastic parameters beside some commonly used viscoelastic parameters to compare the dynamic and transient rheological characteristics of two novel gum dispersions, SSG and cress seed gum, and three commercial hydrocolloids, guar gum, xanthan gum, and pectin.

1.5.4 Chapter 5: Hydrocolloids Interaction Elaboration Based on Rheological Properties

The study of synergistic polysaccharide–polysaccharide interactions remains a very attractive research area. The literature has proved that some novel gums could serve as alternatives to some of the commercial hydrocolloids in gum blend formulations as a stabilizer, thickener, binder, and gelling agents and could be used in food, cosmetics, and pharmaceutical systems. This chapter is invaluable for blends characterization regarding thermos‐rheology, thermodynamic, and the kinetics of the interaction behavior of biopolymers. It reviews studies on new gums and some conventional gum mixtures and reports their rheological properties and the effect of temperature, salts, and pH on these characteristics to provide an assessment of the potential of these gums for influencing the structure of food products. The chapter enables the reader to compare the properties of different sources and aids in the eventual utilization of novel gums in blend systems for their specific usage.

1.5.5 Chapter 6: Sage (Salvia macrosiphon) Seed Gum

Sage (Salvia macrosiphon) is a pharmaceutical plant distributed worldwide. The literature has proved that SSG could be an interesting alternative to some of the commercial gums as a stabilizer, thickener, binder, and as fat‐replacing and gelling agents in food, cosmetics, and pharmaceutical systems. Besides the SSG properties themselves, food ingredients and processing conditions affect its function. This chapter focuses on the very latest researches on the rheological properties of SSG and reviews the effect of some processing conditions, especially temperature, and other food components to provide an assessment of the potential of this novel biopolymer for influencing the structure of food products. In the end, some of the potential applications of SSG within foods, such as ice cream, sauce, yogurt, D‐limonene‐in‐water emulsions, and edible film, are highlighted.

1.5.6 Chapter 7: Balangu (Lallemantia royleana) Seed Gum

Balangu (Lallemantia royleana) seed has been recently investigated for its potential as a novel source of hydrocolloid for its superior thickening, stabilizing, and fat‐replacing characteristics. Furthermore, the chemical and structural properties of Balangu seed gum (BSG) have been studied, which revealed the presence of arabinose, galactose, and rhamnose as the major monosaccharides with strong shear‐thinning properties and high intrinsic viscosity comparable to those of commercial hydrocolloids. This chapter aims to review the structural, physicochemical, functional, and rheological properties of the gum extracted from Balangu seeds. Additionally, the research trends and prospects of BSG are discussed by specifically considering the potential applications in food systems.

1.5.7 Chapter 8: Qodume Shirazi (Alyssum homolocarpum) Seed Gum

Alyssum homolocarpum seed gum (AHSG) is a carbohydrate with a small number of uronic acids. This gum is a rhamnogalactan polysaccharide with a random coil structure and has an average molecular weight compared to other hydrocolloids. The aqueous dispersions of AHSG exhibit shear‐thinning behavior, making it a good candidate for a thickening agent. AHSG solution exhibits high viscosity at low shear rates, and hence AHSG nano‐capsules could be used as a wall material for encapsulation of bioactive compounds. This gum provides a relatively strong biopolymer gel and has a solid‐like behavior. Moreover, AHSG has great emulsion stabilizing capacity, and with the incorporation of AHSG into O/W emulsion, the stability of the emulsion against flocculation, coalescence, and gravitational phase separation improves. On the other hand, AHSG has low surface activity due to its high hydrophilic nature and low molecular flexibility. The biodegradable film could also be prepared from AHSG with suitable mechanical characteristics and low oxygen permeability, making this film a great source for packaging materials. On the basis of the prominently reported references, this chapter provides a review of the extraction optimization, chemical constituents, functional properties, and applications of AHSG.

1.5.8 Chapter 9: Espina Corona (Gleditsia amorphoides) Seed Gum

Espina Corona gum (ECG) is extracted from the seeds of Gleditsia amorphoides trees that grow in South American countries. This gum is approved by the Argentinean food code. It is a galactomannan with an approximate molecular weight of 1.39 × 10⁶ Da, consisting of 71.4% D‐mannose and 28.6% D‐galactose with a mannose/galactose (M/G) ratio of 2.5. The mannose forms a linear chain of (1 → 4) β‐mannopyranose units with one molecule of D‐galactopyranose linked at position 6 every three units of mannose. Structurally, ECG is similar to guar gum (GG), which has an M/G ratio of 2.0. ECG solutions exhibit shear‐thinning behavior. The viscosity of ECG presents good stability during heating and to the addition of salts and acids. At 1% w/w, ECG exhibits the viscoelastic behavior of a weak gel, with light frequency dependence. Moreover, ECG shows very good stabilizing properties in colloid systems by increasing the viscosity of the continuous phase and thus delaying the creaming and coalescence in emulsions, and the drainage, disproportionation, and coalescence in foams. In gels and films, ECG also presents synergistic effects with xanthan gum and improves the mechanical properties of carrageenans/K+ and whey protein systems. This chapter shows this gum is a promising hydrocolloid with great potential use in food and pharmaceutical applications.

1.5.9 Chapter 10: Qodume Shahri (Lepidium perfoliatum) Seed Gum

Lepidium perfoliatum seed gum (LPSG), with 88.23% total carbohydrate, exhibits interesting shear‐thinning behavior with a consistency coefficient higher than pectin, starch, and locust bean gum. This gum can bind and immobilize a large amount of water and increase the viscosity and modify the texture of food products. LPSG can add texture to formulations and stabilize the dispersions and emulsions. LPSG has the ability to reduce the surface and interfacial tensions due to the presence of proteinaceous moiety being present either as an inherent part of the molecular structure or as impurities when extracting this gum. Since LPSG has a weak gel‐like property in aqueous systems, this gum could be an excellent new source of polysaccharides for the formation of films and coatings. LPSG is highly compatible with legume proteins such as grass pea protein isolate and forms homogeneous single‐phase blends. This ability enables LPSG to improve the quality of foods prepared from legume seeds. Addition of LPSG could reduce the amount of oil absorbed by fried food and improves the quality of the final products. In addition, LPSG has the potential to be used as a fat replacer and can act as a binder in food. Most of LPSG functional properties in food are due to the thickening action of this gum in aqueous systems. In this chapter, the rheological and functional properties, as well as the effect of LPSG on the structure and quality of food products, are discussed.

1.5.10 Chapter 11: Persian Gum (Amygdalus scoparia Spach)

Persian gum is one of the emerging potential emerging hydrocolloids which has been introduced and studied during the past decade. This chapter will first discuss our present understanding of the botanical source of the wild almond tree (Amygdalus scoparia Spach) alongside one of its by‐products, Persian gum. Then, the following subsections will deal with how it is harvested and processed, its physicochemical characteristics, structure, rheology, interaction with other macromolecules, surface activity, thermal properties as well as potential applications. In the last subsection, the major challenges with reference to characterization and expansion of its applicability will be addressed.

1.5.11 Chapter 12: Gum Tragacanth (Astragalus gummifer Labillardiere)

Gum tragacanth (Astragalus) (GT) is a plant gum exuded from the stems and branches of various species of Astragalus with a branched heterogeneous anionic structure, containing carboxylic acid groups. There are various species of GT which have different physicochemical and rheological properties. All species of GT are made up of two distinct fractions: tragacanthin, which is the water‐soluble part, and bassorin, which is water swellable. The objective of this chapter is to review safety assessments, structural, rheological, and functional properties of various species of this gum for exploration of their potential applications as a natural pharmaceutical and food agent.

1.5.12 Chapter 13: Cashew Tree (Anarcadium Occidentale L.) Exudate Gum

The cashew tree gum is seen as a promising plant exudate for the food industry; however, there is a lack of understanding of its basic physicochemical, rheological, and toxicological properties, thus preventing its utilization in foods. The best long‐term strategy for promoting the use of cashew gum in the food industry is, therefore, to understand and exploit the agricultural production, harvesting, physicochemical, and rheological properties of the gum. Cashew gum is similar to gum arabic and can be used as a liquid glue substitute for paper, in the pharmaceutical and cosmetic industries as an agglutinant for capsules and pills, and in the food industry as a stabilizer of juices. The production and physicochemical properties of cashew gum can be influenced by the environment within which the trees are found and the age of the trees. Studies on cashew gum have shown that it has good physicochemical, rheological, and functional properties. Cashew gum has been found to be safe for consumption, with a median lethal dose (LD50) of more than 30 g kg−1 b.w., and its application in the production of pineapple jam and chocolate pebbles and as a fat replacer in baked doughnuts as well as an excipient in drug formulation has been studied. In this chapter, the role of this gum in food formulations and product development has been discussed along with examples and methods of characterization to indicate the increasing use of cashew gum.

1.5.13 Chapter 14: Brea Tree (Cercidium praecox) Exudate Gum

Brea gum is the exudate from the Brea tree (Cercidium praecox) that is widespread in arid and semiarid regions of the American continent. The Brea tree grows in poor soils and can help with degraded environment restoration. Brea gum is obtained through cuts or incisions on the bark. Its chemical composition is based on a β‐(1 → 4) xylan backbone heavily substituted by short branch chains containing neutral sugars and uronic acids and their ethers. In an aqueous solution, the molecules acquire a spherical form and exhibit high solubility and a rheological behavior practically Newtonian with a moderate viscosity at high concentrations. Brea gum contains 4%–10% of proteins that influence its functional properties. The gum is suitable as a stabilizer for systems containing high insoluble solids. It acts as a good emulsifier and stabilizer of oil‐in‐water emulsions and favors foam formation and stabilization. Besides, Brea gum forms dense edible films with high water solubility, and hence their mechanical and barrier properties are strongly affected by the ambient relative humidity. Clay nanoparticle incorporation into the film matrix reinforces the structure and reduces the effect of humidity on the film properties. In bread making, an addition of 0.5% of Brea gum to wheat flour increases the moisture of the crumb. The food safety of this hydrocolloid has been demonstrated, and it was approved as a food additive. According to its physicochemical and rheological properties discussed in this chapter, Brea gum could be used as a substitute for gum arabic or similar gums in several applications.

1.5.14 Chapter 15: Chubak (Acanthophyllum glandulosum) Root Gum

A new natural hydrocolloid can be isolated from the roots of Acanthophyllum glandulosum, popularly called Chubak in Iran. The gum has a high total content of carbohydrate (84.3%), and its uronic acid content is 10.3%, which is consistent with the acidic nature of the polysaccharide in gum. The Chubak root extract (CRE) has a high superficial and interfacial activity due to its saponin and hydrocolloid components; thus, it is known as a natural emulsifier and aerating agent because it enables formation of a stable foam. Its use in food systems has been recommended to improve foaming properties or, in other words, aeration. In this chapter, the extraction methods of CRE and its applications in different products such as doughnut, yogurt, ketchup, non‐alcoholic beer, muffin cake, sponge cake, mayonnaise, and grape juice have been discussed. In sum, this chapter demonstrates that CRE can serve as a natural emulsifier and an aerating agent with valuable pharmaceutical properties and a unique taste.

1.5.15 Chapter 16: Marshmallow (Althaea officinalis) Flower Gum

In this chapter, the effect of extraction variables including pH (5–9), temperature (25–65 °C), and water‐powder (W/P) ratio (40:1–80:1 v/w) on yield, consistency coefficient (k), emulsion stability index (ESI), foam stability index (FSI), and color component value (L* parameter) of marshmallow flower gum (MFG) are optimized using response surface methodology (RSM). In addition, some physicochemical properties and biological activity of the optimized MFG, including chemical compositions, average molecular weight, monosaccharides, uronic acids, thermal analysis, and antioxidant potential (DPPH), are characterized. The chapter suggests that MFG could potentially be used as a new source of hydrocolloid whose functional properties are comparable with commercial ones. Also, the influence of different temperatures (5, 25, 45, and 65 °C), pH (5, 7, 9, and 11), and concentration (0.25, 0.5, 1.0, and 2.0 w/v) on the steady shear rheological properties and intrinsic viscosity of MFG were evaluated. The results revealed that the power‐law model satisfactorily described the rheological behavior of the mucilage solutions, and all the MFG solutions exhibited shear‐thinning behavior and non‐dependence on shearing time at all temperatures, pH, and concentrations tested.

1.5.16 Chapter 17: Opuntia Ficus Indica Mucilage

The present chapter aims to summarize the research on the chemical compositions, molecular structure, functional properties, and rheological behavior (steady shear and dynamic rheology) of the mucilages extracted from different parts of Opuntia ficus indica to find their potential applications in food, pharmaceutical, and other systems. It has been suggested that Opuntia ficus indica mucilage is a rhamnogalacturonan polysaccharide mainly composed of xylose, rhamnose, and galactose. It also has been reported that the mucilage from Opuntia ficus can be used as an appropriate edible coating to extend the shelf life of vegetables and fruits. Furthermore, the positive effect of the mucilages of Opuntia ficus indica on encapsulation of phytochemicals and wastewater treatment has been demonstrated in this chapter.

1.5.17 Chapter 18: Emerging Technologies for Isolation of Natural Hydrocolloids from Mucilaginous Seeds

Many mucilaginous seeds around the world have been introduced for use as accessible, cost‐effective, and natural sources. These hydrocolloids are used as thickener, gel former, and as foam and emulsion stabilizing agents in a wide range of foods and pharmaceuticals. Due to the high stickiness between mucilaginous layers and seed cores, a severe mechanical stress is required for quick separation of mucilaginous layers from seed cores. The conventional method for isolating/extracting hydrocolloids from mucilaginous seeds includes hydration processes, followed by the application of a severe mechanical shear stress by high‐speed mixers or stirrers with rotating blade plates. Therefore, a heterogeneous mixture of crushed seeds and mucilage may be produced. Several stages of time‐consuming centrifugation are required to separate the crushed seeds' parts and impurities, which are followed by drying and grinding the derived gum. This leads to high level of damage and crushing of the seed cores, which, on the one hand, makes the use of centrifuge force inevitable and on the other hand results in a large amount of impurities from crushed seeds entering the isolated hydrocolloids. In recent years, attempts have been made to use emerging technologies and new methods for extraction of seeds gums aiming at improving the extraction process of seed gums. This chapter aims to review conventional and emerging extraction methodologies and provides an overview of the current state of hydrocolloid extraction techniques with comparisons of their advantages and disadvantages.

1.5.18 Chapter 19: Purification and Fractionation of Novel Natural Hydrocolloids

Purification of polysaccharides removes unacceptable flavors of the crude gums, and the purified gums give more stable solutions. Physicochemical, rheological, and functional properties of the crude gum improve after purification. In fractionation, the major polymer will be subdivided into fractions with different molecular weights and structures. Therefore, different physicochemical, rheological, functional, and application areas are expected for the fractions. Fractionation, physicochemical, rheological, and functional properties of the fractions and the effect of purification methods on the characteristics of some new hydrocolloids such as durian seed gum, chia seed gum, basil seed gum, and cress seed gum are reviewed in this chapter.

1.5.19 Chapter 20: Improving Texture of Foods using Emerging Hydrocolloids

Foods would never be foods if humans do not feel happiness and satisfaction during eating. From this perspective, palatability is the most important attribute of foods and differentiates them from medicines. Food palatability is determined by some organoleptic attributes, including flavor, texture, appearance, sound, and temperature, and flavor and texture are the two major factors determining food palatability. Texture sensing is primarily the responsibility of the tactile senses to physical stimuli which result from contact between some part of the body and the food. The tactile sense (touch) is the primary method for sensing texture, but kinesthetic (sense of movement and position) and some sight (degree of a slump, the rate of flow) and sound (associated with crisp, crunchy, and crackly textures) are also used to evaluate texture. Texture properties are perceived by human senses. To understand texture, it is critical to know how the human body interacts with food. Mastication is the process in which pieces of food are ground into a fine state, mixed with saliva, and brought to body temperature in readiness for transfer to the stomach, where most of the digestion occurs. Pulverization of food is the main function of mastication, but it also imparts pleasurable sensations that fill a basic human need. Mastication usually reduces particle size by two to three orders of magnitude before passage of the food to the stomach, where another approximately 20 orders of magnitude of size reduction is accomplished by chemical and biochemical action. Since texture is perceived by the human senses, one needs to understand how the body interacts with different foods, because this is the foundation on which is built an understanding of what is needed in objective and subjective tests for texture. In addition, the influence of thermal processing on hydrocolloids is important in some processes such as heating and freezing that are used to prepare many foods. Thus, this chapter is devoted to the effect of hydrocolloids on texture from the standpoint of oral processing, eating psychology, and fractal analysis of some studied hydrocolloids.

1.5.20 Chapter 21: New Hydrocolloids in Ice Cream

Ice cream is a complex colloidal system consists mainly of fat globules, air bubbles, and ice crystals dispersed in a highly viscous aqueous phase. The quality of ice cream largely depends on its formulation. The viscosity of the ice cream mix affects the body, texture, air incorporation, and melting resistance of ice cream. The most important factor which is