Starch amylose and amylopectin

Pea starch granules are oval, sometimes fissured, with a diameter of 20-40 ym (13). Molecular and structural characteristics of the two main components of field pea starch—amylose and amylopectin—are important in determining functional properties (25,26). Smooth field pea starch concentrate contains 97.2% starch of which 30.3-37.8% is amylose (9,23,25-27), and wrinkled pea starch concentrate contains 94.8% starch, which is 64% amylose (26). The gelatinization temperature of smooth pea starch is between 64 to 69 C, and that of wrinkled pea starch is greater than 99 C to 115 C. Gelatinization temperature depends on maturity of field pea seed and amylose content (26,27). 

Starch (amylose and amylopectin) hydrolysis along with ester-fication, etherification or oxidation have been previously discussed as available methods for producing starch derivatives with improved water dispersibilities and reduced retrogradation potential (, ). Since oxidative and hydrolytic reactions are simple, easily controlled chemical modifications, starch-derived polymers made by hydrolysis alone or oxidative and hydrolytic processes were developed and tested. 

Properties of Granular Potato Starch, Amylose, and Amylopectin after Irradiation with High-Energy Electrons"... 

Free radicals originating from starch, amylose, and amylopectin form well-distinguished 1 3 1 or 1 4 1 triplets showing hyperfine splitting of 30 gauss. These triplets are attributed to the derivatives of alkyl radicals produced by abstraction of hydrogen atoms from the 2-, 3-, and/or 4-positions of glucose residues.269... 

IV. Properties of Wheat Starch and Wheat Starch Amylose and Amylopectin 451... 

White et al.8,30,31 have, in several papers, studied the chemical composition of oat starch amylose and amylopectin (Table 15.2). Gel permeation chromatography (GPC) of the total starch gave rise to two peaks, but some of the material had an unusual iodine affinity and was, therefore, described as an intermediate fraction.8... 

The greatly enlarged chapter on wheat starch presents advances in its production, the differences between large and small granules, the fine structures of wheat starch amylose and amylopectin, genetic and chemical modification of wheat starch, and its functionalities and uses, especially in food products. 

Kobayashi, S., Schwartz, S. J., and Linebeck, D. R. (1985). Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography. /. Chromatogr. 319 205-214. 

Dextrinisation The dominant polymers of starch (amylose and amylopectin) are very high molecular weight extended molecules subject to size reduction by shear and amylase degradation in dilute solution. Conditions in the extruder should rapidly deactivate amylase, but the very high shear conditions have been shown to reduce the average molecular weight (Colonna et al. 1984 Davidson et al. 1984). 

In most diets, carbohydrates are a major source of the body s energy requirements. The predominant digestible carbohydrates are starches (amylose and amylopectin). Depending upon the diet, the digestible carbohydrates may... 

D. a-Amylase hydrolyzes a( 1 4) glycosidic bonds present in starch (amylose and amylopectin) in a random fashion leaving primarily the disaccharide maltose, the trisaccharide maltotriose, and an oligosaccharide known as the a-limit dextrin, which is composed of 6 to 8 glucose residues with one or more a(l—>6) glycosidic bonds. Galactose and fructose are not present in starch. 

STARCH Starch, the energy reservoir of plant cells, is a significant source of carbohydrate in the human diet. Much of the nutritional value of the world s major foodstuffs (e.g., potatoes, rice, com, and wheat) comes from starch. Two polysaccharides occur together in starch amylose and amylopectin. 

Several attempts have been made to bind dyes to starch, amylose, and amylopectin.2307 2454,2455 Other starch-based dyes were prepared from starch and corresponding trichloropyrimidine or chlorotriazine derivatives. It was reported that these base-catalyzed reactions proceeded at room temperature within one day.2456... 

Reaction (7) is catalyzed by starch synthases (EC 2.4.1.21 ADP-Glc 1,4-a-D-glucan 4-a-glucosyltransferase), the same reaction as the one catalyzed by the bacterial glycogen synthase (Reaction (2)). Here a different reaction number is given to stress that the final products of starch, amylose, and amylopectin, are different in structure. Isozymic forms of plant starch synthases z.i i-is,65-69 of branching enzymes 4-i 6,65,66,70-76 reported. 

The breakdown of starch (amylose and amylopectin) also requires two enzymes, ot-amylase, and ot(l ->6) glucosidase (another "debranching enzyme"). ot-Amylase cleaves... 

EXAMPLE 11.6 What are the respective dietary sources of the starches amylose and amylopectin ... 

Figure 3 Molecular structures of a-o-glucose and the two major molecules that make up starch, amylose, and amylopectin. 

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