Chemistry
Starch
Starch is a complex carbohydrate found in plants, serving as a major source of energy. It is composed of glucose units linked together in long chains, and it is the primary storage form of energy in plants. Starch is commonly found in foods such as potatoes, rice, and wheat, and it is a key component in many industrial processes.
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10 Key excerpts on "Starch"
eBook - PDF- Alistair M. Stephen, Glyn O. Phillips(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
59 References ........................................................................................................................... 59 2.1 INTRODUCTION Starch is among the most abundant of plant products, a major food reserve providing a bulk nutrient and energy source, often at low cost, in the diet of man. Although normally referred to in the singular, as in this article, there are in fact numerous Starches that differ according to their 25 origins and modes of preparation; genetic modification of source crops complicates the issue further. As with so many definitions, the concept of Starch is ultimately very difficult to define comprehensively; there are many Starches differing in granular morphology, molecular weight and composition (degree of branching of the polysaccharide macromolecules), and physicochemical properties, that it is remarkable that a single appellation has sufficed for many decades. Starch, therefore, is a subject that dominates the literature from many scientific view-points, for example, its botanical distribution and function, production and marketing, molecular structure, and its role in nutrition and food processing. Physicochemical challenges include the complex molecular organization of Starch as laid down in granular form in the plant, and the solution properties of Starch. As far as this book is concerned only limited coverage will be attempted of the extensive world literature on the subject, contained in books, encyclopedias, reviews, society and conference proceedings, and journals. Sources, analysis, rheological properties, and some commercial food applications of Starch are dis-cussed in this chapter; the analytical section includes reviews in depth of physicochemical methods applicable to the granule in its native and gelatinized states (x-ray diffraction, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) spectros-copy).
eBook - PDF- Susan Sungsoo Cho(Author)
- 1999(Publication Date)
- CRC Press(Publisher)
The components of complex carbohydrates/dietary fiber have traditionally been defined on the basis of the solvent extraction procedures used for their isolation. This does not result in clearly definitive separations of the components, nor in definition when a structural basis is used. The chemistry of complex carbohydrates 107 Starch Starch is the most important reserve polysaccharide of many higher plants where it occurs as discrete granules in the leaf, stem (pith), root (tuber), seed, fruit and pollen. The size, shape and gelatinization temperature of the granules depend on the botanical source of the Starch. Common food Starches are derived from seed (wheat, maize, rice, barley) and root (potato, cassava/tapioca) sources. Starch consists of a mixture of two polymers, amylose and amylopectin, that are composed entirely of glucose units, i.e. homopolysaccharides. The glucopyranosyl units in amylose are linked through alpha-D-(1→4)-glucosidic linkages. Amylose has traditionally been considered to be a linear polymer with an average chain length and degree of polymerization of approximately 1000 or less. However, it is now known that it contains a limited amount of branching involving alpha-D-(1→6)-glucosidic linkages at the branch points. Amyloses, as isolated, are often a mixture of linear and branched molecules (Figure 1). The behavior of amylose is dominated by two major properties: (a) Its ability to form inclusion complexes with iodine, aliphatic primary alcohols, lipids and surfactants. Amylose produces a deep blue inclusion complex with iodine, used in the detection of Starch, in which the amylose chain forms a helix around the iodine molecule with six glucosyl units per turn of the helix. (b) Its ability to form strong intermolecular interactions, hydrogen bonding, leading to precipitation or gel formation when a solution of amylose is cooled.
eBook - PDFHandbook of Food Analysis
Volume 1: Physical Characterization and Nutrient Analysis
- Leo M.L. Nollet(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
Table 1 summarizes several different classifications of carbohydrates for the purpose of food analysis. For its part, and from a nutritional point of view, Starch can be divided into glycogenic (‘‘available’’) and resistant Starch, which is not absorbed in the small intestine. Starch consists primarily of two components, amylose and amylopectin. Amylose is a linear or very lightly branched polymer consisting of several thou-sand (1 ! 4)- -D -linked D -glucose units with molecular masses ranging from 2 10 5 to 2 10 6 (9). Amylo-pectin is a much larger, highly branched polymer consisting of relatively short segments of (1 ! 4)- -D -linked D -glucan units connected by (1 ! 6)- -D -glyco-sidic linkages, with molecular masses ranging from 10 7 to 5 10 8 . Plant Starches typically contain 20–30% amylose, but the amylose may range from 0 to 80%. In potato and some other species a small fraction (<1%) of the glucose residues in amylopectin are phosphory-lated. All foods, with few exceptions, contain carbo-hydrates, which may vary in form from a simple monosaccharide to a more complex polysaccharide. The primary end use of Starch is also in food products. Table 2 summarizes the most important food carbo-hydrates along with their characteristics. It also briefly describes where they are usually found. Carbohydrates (sugars) are a major source of energy for the human body and their varied functional properties are utilized by the food industry to enhance, for instance, the 383 palatability, acceptability, and shelf life of foodstuffs. There is thus a continuing need to monitor levels of carbohydrates in foods in order to predict and control the properties of the food as well as interactions of the components. Albeit all sugars have similar densities in the dry state, they differ significantly in other physicochemical properties. For instance, viscosity increases with increasing molecular weight, whereas osmotic pressure logically decreases.
- Visakh P M, Long Yu(Authors)
- 2015(Publication Date)
- Royal Society of Chemistry(Publisher)
cement and oil drilling. 2,3 Starch varies greatly in form and functionality between and within botanical species, and even from the same plant cultivar grown under different conditions. Starches with a wide range of functional properties are needed to ensure fitness-for-purpose for such a diverse range of end uses. Starch can also be converted into Starch nanocomposites to enhance its properties and serve as an ideal ‘‘green’’ biopolymer that comes from Nature and readily goes back to Nature. Various research activities are ongoing worldwide in different areas of Starch nanocomposites, opening up new avenues for its application. 4 2.2 Starch Structure Starch has been the subject of intensive research over many decades, re-sulting in a vast body of published literature on preparative and analytical methods, molecular structure, physical, chemical and biochemical prop-erties, functionality and uses. Starch is a polysaccharide consisting of D -glucose units, referred to as homoglucan or glucopyranose, and has two major biomacromolecules – amylose and amylopectin (Figure 2.1). Starch consists primarily of D -gluco-pyranose polymers linked together by a -(1 -4) and a -(1 -6) glycosidic bonds. In forming these bonds, C1 on a D -glucopyranose molecule reacts with C4 or C6 from an adjacent D -glucopyranose molecule. Starch polymers always have one reducing end because the aldehyde group on one end is Figure 2.1 Structures of (a) amylose and (b) amylopectin. Reproduced from Xie et al. 11 with permission of Elsevier. 18 Chapter 2 free. The other end of the polymer is called the non-reducing end. There could be a large number of non-reducing ends in a Starch molecule de-pending on the number of polymeric branches. The glycosidic linkages in Starch are in the a configuration. Formation of the a linkages is determined by the orientation of the hydroxyl group (–OH) on C1 of the pyranose ring.
eBook - PDFFood Carbohydrates
Chemistry, Physical Properties, and Applications
- Steve W. Cui(Author)
- 2005(Publication Date)
- CRC Press(Publisher)
348 References ............................................................................................................. 349 7.1 Introduction Among food carbohydrates, Starch occupies a unique position. It is the major carbohydrate storage material in many higher plants and is considered the second largest natural biopolymer next to cellulose. Starch is deposited in plant organs in the form of granules that are relatively dense, insoluble in cold water, and range from 1 to 100 μ m in size depending on the plant species. Starch contributes to the physicochemical properties of food prod-ucts made from cereals, tubers, roots, legumes, and fruits. It is the basic source of energy for the majority of the world’s population. In human nutri-tion, Starch plays a major part in supplying the metabolic energy that enables the body to perform its different functions. Recent studies suggest that slowly digested Starch and enzyme resistant Starch have significant implica-tions for human health. Unlike some carbohydrates and digestible Starches, resistant Starch resists enzymatic hydrolysis in the upper gastrointestinal Understanding Starches and Their Role in Foods 311 tract, thus resulting in little or no direct glucose absorption. In addition, resistant Starch causes increased microbial fermentation in the large intestine to produce short-chain fatty acids, a similar physiological effect to dietary fiber. Starch is also one of the most important raw materials for industrial use. In its native granular form, Starch has limited applications. However, using chemical and physical modifications, Starch has been applied in a wide variety of industrial products including food ingredients, sizing agents for paper, textiles, and Starch-based plastics (Table 7.1). More information on modified Starch is given in Chapter 8. Starch occurs throughout the plant world. Cereal grains, legume seeds, and tubers are the most important sources of Starch.
- Piotr Tomasik(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
81 0-8493-1486-0/04/$0.00+$1.50 © 2004 by CRC Press LLC 7 Starch: Structure and Properties Jay-lin Jane CONTENTS 7.1 Introduction ................................................................................................... 81 7.2 Chemical Structures and Starch Molecules ................................................. 82 7.2.1 Amylose ............................................................................................ 82 7.2.2 Amylopectin ...................................................................................... 83 7.2.3 Minor Components of Starch ........................................................... 87 7.3 Organization of Starch Granules .................................................................. 89 7.4 Properties of Starch ...................................................................................... 90 7.4.1 Starch Gelatinization ......................................................................... 91 7.4.2 Pasting of Starch ............................................................................... 92 7.4.3 Starch Retrogradation ....................................................................... 94 7.4.4 Glass-Transition Temperature of Starch ........................................... 95 References .............................................................................................................. 96 7.1 INTRODUCTION Starch is produced by higher plants for energy storage and is the second largest biomass produced on earth, next to cellulose. Starch is also the major energy source in human and animal diets. Starch granules, consisting of highly branched amy-lopectin and primarily linear amylase (Chapter 1), are synthesized by apposition in amyloplasts of plants. Amylopectin and amylose molecules are organized in semi-crystalline Starch granules, and the outer chains of amylopectin molecules are arranged in double-helical crystalline structures.
eBook - PDFCereal Grain-based Functional Foods
Carbohydrate and Phytochemical Components
- Trust Beta, Mary Ellen Camire(Authors)
- 2018(Publication Date)
- Royal Society of Chemistry(Publisher)
Reprinted with permis-sion from J.-L. Jane, T. Kasemsuwan, S. Leas, H. Zobel and J. F. Robyt, Starch/Stärke , 1994, 46 (4), 121–129. Copyright 2006, John Wiley and Sons. 1 87 Starch Properties and Modification in Grains and Grain Products Starch is made up of two polymers of anhydroglucose: amylose and amylo-pectin. Amylose is the smaller molecule, typically a few hundred α -d-glucose units arranged linearly (with very little branching) with α (1–4) linkages. Amy-lopectin is much larger, perhaps the largest molecule commonly occurring in nature. It consists of many thousands of α -d-glucose units and is highly branched. The chains are linear α (1–4) glucosidic linkages and the branch points are α (1–6) bonds (Figure 5.2). The size and size distribution of amylose and amylopectin molecules affect the crystallinity and order within the granule. The branch point dis-tribution and chain length of amylopectin affect important properties of Starch, such as the viscosity of cooked pastes. Starch is largely indigestible to humans until it has been gelatinized, where the Starch granule absorbs water and loses crystalline order on heating past the gelatinization temperature (GT). Gelatinization, in common language, is the cooking of Starch. Starch granules may require higher or lower temperatures to gelatinize, depending on various factors, such as the taxonomic/genotypic origin, the amylose to amylopectin ratio, and the molecular structure of amylose and amylopec-tin. Without gelatinization, Starch is not cooked; it is inaccessible to human digestive enzymes (amylases) and cannot be consumed. Figure 5.2 Molecular structure of (a) amylose (2-NEUROtiker) and (b) amylopectin (3-NEUROtiker). 2,3 Chapter 5 88 Starch has a major effect on the structural and textural properties of many foods in which it is the predominant component, such as baked products, noodles and pasta, and rice.
eBook - PDFPolysaccharides
Structural Diversity and Functional Versatility, Second Edition
- Severian Dumitriu(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
25 Starch: Commercial Sources and Derived Products Charles J. Knill and John F. Kennedy University of Birmingham Research Park, Birmingham, United Kingdom I. INTRODUCTION Starches are the principle food reserve polysaccharides in plants and are therefore the major source of carbohydrates in the human diet, traditionally supplying f 70–80% of the calories consumed by humans with approximately two-thirds of these calories coming from Starch [1–3]. Starch is present in all staple foods, e.g., wheat ( Triticum vulgare ), maize ( Zea mays ), rice ( Oryza sativa ), potato ( Solanum tuberosum ), sago ( Metroxylon palm species), tapioca/cas-sava ( Manihot esculenta ), rye ( Secale cereale ), barley ( Hor-deum vulgare ), oats ( Avena sativa ), etc. [4–14]. Other less common sources of Starch include sorghum ( Sorghum bicolor ), yam/sweet potato ( Dioscorea species), and arrow-root ( Maranta arundinacea ) [4,5,7,12,15]. The breakdown of consumed Starch molecules to component glucose is somewhat slow, thus providing a sustained source of energy. Starch, taken from grains, tubers, and roots, has been consumed as food and feed for centuries and is of great economic importance, being isolated on an industrial scale from many sources. Wheat is the leading cereal grain produced, consumed, and traded in the world, followed closely by rice and maize [16]. Food is the major use for wheat, accounting on average for ap-proximately two-thirds of total consumption [17]. No other single food ingredient compares with Starch in terms of sheer versatility of application in the food industry. The industrial uses of Starch arise from its unique character since it can be used directly as intact granules, in the swollen granular state, in the dispersed form, as a film dried from a dispersion, as an extrudate powder, after controlled partial hydrolysis to a mixture of oligosaccha-rides, after hydrolysis and isomerization to glucose and fructose syrups, or after chemical modification [18].
eBook - PDFThe Carbohydrates
Chemistry And Biochemistry
- Ward Pigman(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
38. Starch AND GLYCOGEN C. T. GREENWOOD I. Starch 471 A. Introduction 471 B. Occurrence and Isolation . . . . . 472 C. The Starch Granule 473 D. Fractionation of Starch 482 E. Chemical Structure of Amylose and Amylopectin . 483 F. Properties of Amylose 487 G. Properties of Amylopectin 492 H. Action of Amylolytic Enzymes . . . . 494 I. Other Starch-Degrading Enzymes . . . 498 J. Industrial Starches, BY CHESTER SZYMANSKI . . 499 II. Glycogen 506 A. Introduction . . . . . . . 506 B. Occurrence and Isolation . . . . . 506 C. Chemical Structure of Glycogen . . . . 507 D. Properties of Glycogen 507 E. Action of Amylolytic Enzymes . . . . 508 References . . . . . . . . 509 I. Starch A. INTRODUCTION Starch is a mixture of glucans which is found mainly in the plant kingdom, where it occurs as the principal food reserve polysaccharide and may be utilized during growth of the plant. Starch usually forms the chief source of carbohydrate in the human diet. The polysaccharide is thus of great economic importance, and it is isolated on an industrial scale from many sources, particularly cereals. Although the food industry is a major outlet for the manufactured product, Starch, modified Starch, and Starch derivatives have many general uses in industry, particularly in paper and textile manufacture. After cellulose, Starch is probably the most widely commercially utilized of all the polysaccharides. 471 472 C. T. GREENWOOD Unlike most other polysaccharides, the isolation of Starch presents no major problems. The polysaccharide is laid down in the plant in the form of insoluble particles—the Starch granules—and usually these can be readily liberated from the plant tissue without degradation. In view of its practical importance, Starch has been extensively investi-gated.
eBook - PDF- F Meuser, D J Manners, W Seibel(Authors)
- 1987(Publication Date)
- Woodhead Publishing(Publisher)
Starch granules in banana retrogradation.Cooked Starch, once cooled, may contain regions where the Starch chains (mainly amylose) have crystallised into a configuration that is highly resistant to pancreatic amylase16. b) and potat09J~Js. c) The factors given above are related to the Starchy food itself and may be de- scribed as intrinsic factors. Other intrinsic factors that have been shown to affect a-amylase activity in vifro include amylose-lipid ~omplexes~~, native a-amylase inhibi- 138 Plant Polymeric Carbohydrates tors18, and non-Starch polysaccharides which may have a direct effect on enzyme ac- tivityl9. However, it is not clear to what extent these factors affect the digestibility of Starch in vivo. In addition to these intrinsic factors, Starch digestion is influenced by factors related directly to the consumer, which may be d e d extrinsic factors. Extrin- sic influences include the degree of chewing20, concentration of amylase and amount of Starch in the gut, transit time through the small intestine21, and the presence of other food materials in the digesta22. 3 NUTRITIONAL CLASSIFICATION OF Starch In order to clarify the differences observed in Starch digestibility, Englyst and C~mrnings~~ introduced a nutritional classification of Starch, which has subsequently been modified24,25 and is shown in Table 1. For nutritional purposes Starch may be classified into three main types. Rapidly digestible Starch (RDS) is Starch that is likely to be rapidly and completely digested and absorbed in the small intestine of man. Slowly digestible Starch (SDS) is Starch that is likely to be completely digested in the small intestine, but at a slower rate. Resistant Starch (RS) is Starch that is likely to re- sist digestion in the small intestine and become available for fermentation in the large intestine. Most Starchy foods will contain Starch belonging to two, if not all three, categories of Starch, but in very different proportions.
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