Starch granule, structure

Starch occurs as highly organized structures, known as starch granules. Starch has unique thermal properties and functionality that have permitted its wide use in food products and industrial applications. When heated in water, starch undergoes a transition process, during which the granules break down into a mixture of... 

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. 

Li, J. H., Guiltinan, M. J., and Thompson, D. B. 2006. The use of laser differential interference contrast microscopy for the characterization of starch granule ring structure. Starch-Starke 58 1-5. 

Sahai, D., Jackson, D. S. (1996). Structural and chemical properties of native corn starch granules. Starch, 48, 249-255. 

Intrinsic factors that may influence potato digestibility include the structure of the starch molecules, the structure of starch granules, the composition of the potato, the presence of phosphate in starch granules, tissue structure, and factors that may affect these, including agronomic and growth history, storage, maturity, and variety. 

High-Resolution AFM (and LVSEM) Studies of Starch Granule Surface Structure... 

Owing to the method and the type of plasticizer used for TPS production, the process leads to the destruction of the starch granule lamellar structure, giving rise to a quasi-amorphous or semi-crystalline material. 

Yasuda (1945) deduced this from his observation that the protoplasm of the pollen tube is found primarily at the apex and constantly recedes from the older portions of the pollen tube. Later, O Kelley and Carr (1954) observed from electron micrographs that the wall structure of the extreme tip was more open than the portions behind the tip. This has been confirmed by Iwanami (1959), who considers the tip to be continuously in an unfinished state. He presents evidence that the tube contents are always under slight positive pressure maintaining a continuous tendency toward rupture of the tip membrane, counterbalanced by the continuous formation of new wall. He also observed that the protoplasm at the very apex of the tube has a different appearance than that further back because of the absence of granules (starch grains). This clear portion he has called a cap block. 

Amylopectin is a highly branched molecule which is responsible for the main crystalline charactCT of the starch granule. Its structure was modelled as a hyperbranched molecule [17, 51, 52], as proposed initially by Nikuni [53] and French [16] and later improved by Robin [37] (Fig. 15.4). In this model, short chains with 15 D-glucopyranosyl units branch out at almost regular intervals of 25 units to form either external A-chains or internal chains of amylopectin [37]. Starch crystallites are thus formed in compact areas made up of A-chains with DP 15. Less compact areas mainly occupied by B-chains, where the (l,6)-a-D-branching points are located, are placed between these compact areas. 

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