Starch granules amylose

Amylose and amylopectin are the main carbohydrate components of the starch granule. Amylose is an essentially linear a-1, 4-D-glucan chain. About 25-55% of the... 

At least two polymers can be distinguished within the starch granule amylose, which is essentially linear and amylopectin, which is highly... 

In contrast to the fibrous and well-oriented polysaccharides (such as cellulose and chitin), amylose in its natural state is found only in more-or-less spherical starch granules. Amylose is the minor constituent of most starches, and is a linear polymer of a-D-(l—>4)-linked D-glucose residues. The birefringence of starch grains was already well known at the turn of the century, and the cross of isocline pattern between crossed Nicols was interpreted in terms of radially arranged crystallites. Later,... 

Within the semicrystalline native starch granules amylose and amylopectin molecules are held tightly together via a dense network of internal hydrogen bonds. This internal network provides a barrier to water penetration inside the granules that are therefore insoluble in water. One way to break up this barrier and allow for penetration of water and dissolution of the polymer network is a thermal treatment, also called... 

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). 

Birefringence (or double refraction) is the decomposition of a light ray into two rays when it passes through certain types of crystalline material. This occurs only when the material is anisotropic, that is, the material has different characteristics in different directions. Amylose and amylopectin polymers are organized into a radially anisotropic, semicrystalline unit in the starch granule. This radial anisotropy is responsible for the distinctive... 

Maltese cross (Blanshard, 1979). The crystallinity of starch is caused essentially by amylopectin pol)Tner interactions (Banks and Greenwood, 1975 Biliaderis, 1998 Donald, 2004 Hizukuri, 1996). An illustration of currently accepted starch granule structure is given in Fig. 5.5. It is believed that the outer branches of amylopectin molecules interact to arrange themselves into "crystallites" forming crystalline lamellae within the granule (Fig. 5.5 Tester et al., 2004). A small number of amylose polymers may also interact with amylopectin crystallites. This hypothetical structure has been derived based on the cluster model of amylopectin (Hizukuri, 1986 Robin et ah, 1974 Fig. 5.1). 

Cheetham, N. W.H. and Tao, L. (1998). Variation in crystalline type with amylose content in maize starch granules X-ray powder diffraction study. Carbohydrate Polymers. 36, 277-284. 

Debet, M. R. and Gidley, M. J. (2007). Why do gelatinized starch granules not dissolve completely Roles of amylose, protein, and lipids in granule "ghosP integrity. /. Agric. Food Chem. 55, 4752- 760. 

Jenkins, P. J., and Donald, A. M. (1995). The influence of amylose on starch granule structure. International Journal of Biological Macromolecules. 17,315-321. 

In these plant organs, starch is present in the form of microscopically small granules in special organelles known as amyloplasts. Starch granules are virtually insoluble in cold water, but swell dramatically when the water is heated. Some 15-25% of the starch goes into solution in colloidal form when the mixture is subjected to prolonged boiling. This proportion is called amylose ( soluble starch ). 

Starch granules are composed of two types of a-glucan, amylose and amylopectin, which represent approximately 98-99% of the dry weight. The ratio of the two polysaccharides varies according to the botanical origin of the starch. 

Jane, J. L., Xu, A., Radosavljevic, M., Seib, P. A. (1992). Location of amylose in normal starch granules. 1. Susceptibility of amylose and amylopectin to cross-linking reagents. Cereal Chem., 69,405 09. 

Kasemsuwan, T., Jane, J. (1995). Location of amylose in normal starch granules. II Location of phospho-diester cross-linking revealed by phosphorous-31 nuclear magnetic resonance. Cereal Chemistry, 72, 169-176. 

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