Structure and Chemistry of the Starch Granule
1980; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-12-675403-2.50015-6
Autores Tópico(s)Clay minerals and soil interactions
ResumoThis chapter describes the structure and chemistry of the starch granule. Starch, the principal reserve carbohydrate of the higher plants, occurs as water-insoluble granules. The shape and size of the granules are markedly dependent on the botanical source. With increasing maturity, the amylose content of the starch increases, for studies on potato, pea, barley, wheat, and rice have all identified this feature of the growth process. In addition, during development, the average size of the amylose and amylopectin components increases. The β amylolysis limit of the amylose fractions decreased during growth—clearly indicates that the extent of long-chain branching of the amylose increased. It is envisaged that amylose and amylopectin are synthesized within the plastid and form a coacervate droplet that is then nucleated and undergoes spherulitic crystallization. The type of nucleation depends on the cultivar, like, in potato starch once nucleated the granules grow quickly to their limiting size before others are nucleated whereas in cereals, all granules may be nucleated at the same time and continue to grow relatively slowly.
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