The Molecular Properties of the Components of Starches

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Abstract
Summary: Starches from a wide variety of botanical sources have been isolated, purified and fractionated into their amylose and amylopectin components. Some molecular properties of the fractions have been examined.In the case of the pure amyloses, in addition to apparent variations in molecular size, as shown by differences in viscosity, there are large differences in the extent of β‐amylolysis. These differences appear to be a characteristic of the source of starch. All amyloses are heterogeneous and can be separated into fractions with varying β‐amylolysis limits. Recent experiments to identify the nature of the barrier to β‐amylase are described. The limitations of enzymic methods to solve this problem are emphasised, and the results of recent physicochemical techniques are discussed.The amylopectin components have been characterized by measurements ot their purity, average length of unit‐chain, β‐amylolysis limit and phosphorus‐content. Further, viscosity and lightscattering measurements have been made in a variety of solvents. The latter measurements enabled calculations of molecular weights and radii of gyration to be made. The solution behaviour of amylopectins is strongly influenced by the presence of phosphate groups. Examples of this behaviour are given and discussed.