Amylose amylopectin and

Substances commonly found in starch granules are amylopectin, amylose, molecules intermediate between amylose and amylopectin, lipid (including phospholipids and free fatty acids), phosphate monoester and proteins/enzymes. The contents and the structures of amylopectin and amylose play major roles in the functional properties of starch. However, lipids, phospholipids and phosphate monoester groups have significant effects on starch functional properties, even though they are minor constituents. 

Mutants of maize starch varieties have been extensively studied.12 85-100 Amylose, amylopectin, and intermediate material contents of various single and double mutants have been analyzed the results are shown in Table 6.2. Relationships between structures of the starch polymers and functional properties of these mutant starches have also been reported.12,85-100 

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Starch is composed of two major components—amylopectin and amylose. It is the second most abundant polysaccharide and is found largely within plants. 

The dependence of the mobilities of amylopectin and amylose on iodine concentration in the background electrolyte and applied temperature was studied by Brewster et al. (111). The method was used for the separation and identification of different plant starches, but no binding constants were calculated. 

Starch granules are composed of two different polysaccharides, amylopectin and amylose the former constitutes about 80 % of the most common starches. Separation of the two components can be achieved by selective precipitation involving the formation of an insoluble complex of amylose with polar organic substances. 

Further Studies of Gbss and Isoforms Their Involvement in Both Amylopectin and Amylose Synthesis... 

Waxy com starch contains only amylopec-tin com starch contains both amylopectin and amylose. This results in a different viscosity profile (Figure 8-37). Com starch shows a lower peak viscosity and less breakdown during heating. After cooling, the viscosity continues to increase, probably because the amylose interlinks with the amylopectin. On further storage at 25°C, the slurry sets to a firm gel. Tapioca starch is intermediate between com and waxy com starch (Figure 8-37). This is explained by the... 

From the information available on the branching enzyme and starch synthase isozymes, a possible route for the synthesis of amylopectin and amylose can be proposed as shown in Fig. 1. 

These reactions do not have to occur in perfect sequence, and the phases may have some overlap (e.g., phases 2, 3, and 4 may overlap, and possibly even 5 and 6). However, the present evidence, such as intermediate products formed by starch mutants of C. reinhardtii and of higher plants, supports the sequence of reactions shown in Fig. 1 for amylopectin and amylose biosynthesis. Further experiments are required to test this hypothetic scheme, and attempts to purify and characterize the debranching enzyme, crucial to this hypothesis, are under way. 

Phenols readily form starch complexes, and they are also readily extract-able. As indicated in Table XXXII, the extraction of phenols from their complexes with amylopectin and amylose using diethyl ether generally proceeds more readily with amylopectin. 

Hand building finishes that lose their effect after one or two launderings are considered non-durable. The two major product types of non-durable hand builders are starch derivatives and polyvinyl alcohol. Natural starch is produced commercially from potatoes, com, wheat, rice and tapioca. Its two main components are polymers of a-glucose, amylopectin and amylose, shown in Fig. 4.1. The thickening effect of starch is mainly due to the long and branched amylopectin chains. 

Isozymes of plant starch synthases (2, 16-20) and branching enzymes (2, 16, 21-26) have been characterized. Presumably, they play distinct roles in amylopectin and amylose synthesis. Also, plant and Chlamydomonas reinhardtii granule-bound starch synthases (27-33) are responsible for synthesis of amylose. Mutants defective in this enzyme are known as waxy mutants and contain starch granules that have little or no amylose. 

C in all cases, the commonly used frozen storage conditions (approximately — 18°C) would be located above the Tg temperatures thus systems stored at this temperature would be at the rubbery state and would have more molecular mobility. In this situation, deteriorative phenomena depending on diffusion could occur. As amylopectin and amylose retrogradation are crystallization phenomena occurring in starch systems, they were studied in the present work as examples of deteriorative changes. As observed in Table 18.1, values foimd for the onset temperature (T p varied between... 

Cooking starch in the presence of amino acids may favour the occurrence of Maillard reactions, lowering the bioavailability of lysine in the diet. 13C CPMAS was used to follow the effect of Maillard reactions on the bioavailability of potato starch.124 A loss of crystallinity was found for the three samples studied starch, amylopectin, and amylose, being more marked for amylose. A similar study on chestnut starch indicated that Maillard reactions do not influence significantly its digestibility.125 NMR was used to characterize some Maillard reaction products extracted from model reactive mixtures such as starch-glucose-lysine 126 and lactose-lysine.127... 

Our aim has been to elucidate the behaviour of starch films by investigating the properties of films prepared with pure amylopectin and amylose plasticised by glycerol and water. Even though amylose is known to be a good film former1 both amylose and amylopectin were studied in order to get better understanding of the phenomenon related to plasticisers. 

Although, on the basis of chemical studies, it was possible to ascertain the gross structures of the molecules of starch and glycogen, the use of highly purified enzymes has become established as one of the most versatile and definitive methods for the determination of the fine structure of these polysaccharides. The use of these techniques in the examination of the fine structures of glycogen, amylopectin, and amylose will now be discussed. 

Fig. 34 shows schematic structures of amylopectin, amylose, and cellulose and also indicates where different glucanases attack these polysaccharides. Alpha-amylases (EC 3.2.1.1) are enrio-enzymes, which hydrolyze a-(l—>4) glueosidie linkages in amylopectin and amylose (Fig. 34A). In amylopectin, flie A, B, and C chains are hydrolyzed by these enzymes, whereas the a-(l—>6) glueosidie linkages in fire branching points of amylopectin are not attacked. These hnkages can be hydrolyzed by pullulanases (EC 3.2.1.41) and isoamylases (EC 3.2.1.68).

Digital oscillator densimeter techniques have been used to determine the density of dispersions of starch, glycogen, dextrin, amylopectin, and amylose in water at 40 C but at different concentrations. ... 

Kokini, J.L., Baumann, G.C., Bresslauer, K., Chedid, L.L., Herh, P., Lai, L.S. A kinetic model for starch gelatinization and effect of starch/protein interactions on rheological properties of 98 % amylopectin and amylose rich starches. In Spiess, W.E.L., Schubert, H. (eds.) Engineering and Foods, Advanced Process, pp. 109-121. Elsevier/Applied Science Publishers, New York (1990)... 

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