Starches structure

French500 has collected together unit-cell data for maltose hydrate and some poly-O-acylsaccharides in the hope that some packing information might be obtained which could be applied to the problem of starch structure. 

FIGURE 5.4 Potato starch granules viewed under polarized light (magnification, x400). Reprinted from Encyclopedia of Food Sciences and Nutrition (Second Edition), Jackson (2003b), Starch - Structure, properties and determination. Pages 5561-5567, with permission from Elsevier. 

FIGURE 5.5 Schematic diagram of starch granule structure. Adapted from Donald et al. (1997), Starch - Structure and functionality, ISBN 0854047425, with permission from Woodhead Publishing Ltd., Cambridge, UK. 

Starch phase transitions occur in a wide temperature range. The phase transition process starts at temperatures as low as 35-40 °C, depending on the type of starch. In contrast to what was previously believed, it is now understood that amylose and/or amorphous phases also play significant roles in the phase transition process (Ratnayake and Jackson, 2007 Vermeylen et ah, 2006). Theories that describe gelatinization and phase transition in terms of crystallite melting, therefore, are unlikely to adequately explain the phenomena. In summary, it is evident that starch gelatinization is not an absolute result of crystallite melting. Hence, it should not be considered a simple order-to-disorder phase transition of starch structures. 

Donald, A. M. (2004). Understanding starch structure and functionality. In "Starch in Food-Structure, Function and Applications" (A.-C. Eliasson, ed.), pp. 156-184. Woodhead Publishing Limited, Cambridge. 

Jackson, D. S. (2003b). Starch-Structure, properties and determination. In "Encyclopedia of food sciences, food technology, and nutrition" (Revised Second Edition), pp. 5561-5567. Academic Press, New York. 

Prior to 1939, however, it was not known whether the cyclodextrins were products of the synthetic metabolism of Bacillus macerans, and therefore, perhaps, quite different from the components of starch, or whether they were formed by a single enzyme and therefore closely related to the starch structure. Then, Tilden and Hudson announced the discovery of a cell-free enzyme preparation from cultures of Bacillus macerans which had the ability to convert starch into the Schardinger dextrins without the production of maltose, glucose, or any other reducing sugars. They thus concluded that the Schardinger dextrins were either the true components of starch or closely related to such true components. 

Thus, Freudenberg concluded that the cyclodextrins are not preformed in starch, but that their formation is made possible by the helicity of the starch chain. Freudenberg s hypotheses concerning the starch structure (that is, the amylose fraction) and the Bacillus macerans amylase mechanism have been confirmed by X-ray crystallography and chromatographic techniques. ... 

Imberty, A., Buleon, A., Tran, V., Perez, S. (1991). Recent advances in knowledge of starch structure. Starch/Stdrke, 43,375-384. 

Barichello, V., Yada, R. Y, Coffin, R. H., Stanley, D. W. (1990). Low temperature sweetening in susceptible and resistant potatoes Starch structure and composition. J. FoodScL, 54, 1054-1059. 

Mitehell, I, Hill, S., Faterson, L., Valles, B., Barelay, F., Blanshard, J. (1997). The role of moleeular weight in the eonversion of stareh. In F. J. Frazier, A. M. Donald, F. Riehmonds (Eds.), Starch structure and functionality. Royal Society of Chemistry, Cambridge, UK. 

Despite the widespread cultivation and use of potatoes, very little is known about the influence of some factors on their GI and RGI, whereas some obvious factors, such as starch structure and processing, have been subjected to a limited amount of research. 

GI values. The relationship between maturity, starch structure, and glycemic impact requires further research. 

Mutations of SSIIa have been observed in wheat and rice.208 In wheat, each of the three wheat genomes were mutated to entirely eliminate expression of the SSIIa gene product, Sgp-1 protein in one line 209 the result was reduced starch amounts and an altered starch structure. In rice, two classes of starch have been found. In Indica rices, the starch is of the long chain variety, while in Japonica, it is of the short chain variety.208 Genetic analysis showed that the mutation in Japonica rice led to a loss of starch synthase II.209 Thus, in higher plants, it seems that loss of SSII activity in dicots and SSIIa activity in monocots have the same results with respect to reduced starch content, due to a lowered amount of amylopectin and altered amylopectin chain size distribution. Thus, these genes may have the same function in starch biosynthesis. 

Amylose extender mutants have been found in rice.272 The alteration of the starch structure is very similar to that reported for maize endosperm ae mutants. The defect is in the BE3 isozyme, BE3 of rice being more similar in amino acid sequence to maize BE11 than to BEl.36,272 Thus, rice BE3 may catalyze the transfer of small chains, rather than long chains. 

In addition to the three starch biosynthetic enzymes, other enzymes have been shown to have some effect on starch structure. 

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