Studies on the biosynthesis of starch granules : Part III. The properties of the components of starches from the growing potato tuber

Abstract

Starch granules have been isolated from potato tubers of various stages of maturity, and their properties investigated. Increase in maturity was accompanied by an increase in granule size and amylose-content, whilst the gelatinization-temperature decreased. The amylose-content and gelatinization-temperature were both directly related to granule size. The starches have been fractionated into their amylose and amylopectin components, and the fine-structure of these investigated. For both components, it was found that with increase in maturity there was ( i) an increase in molecular size, and ( ii) a decrease in the extent of conversion into maltose by β-amylase. The properties of an intermediate fraction have also been characterized. One starch sample was separated into granules of different sizes, and the properties of these and their component amylose and amylopectin were studied. The results indicated that the fundamental properties of a sample of potato starch are determined essentially by the size of the granules.