Composition of chains in waxy-rice starch and its structural units

phi,beta-Limit dextrins of fractions of intermediate products obtained by alpha-amylolysis of waxy-rice starch were analysed for their unit chain distributions by gel-permeation chromatography. The proportion of long chains decreased in fractions of low-molecularweight dextrins, but the ratio of A:B-chains, A:Ba-chains, and Ba:Bb-chains remained almost constant. High-performance anion exchange chromatography was used for a detailed analysis of the composition of B-chains. Chains with a length intermediate to the groups of short and long B-chains increased in small dextrins. The shortest B-chain in the phi,beta-limit dextrins was maltotriose and was preferentially produced during alpha-amylolysis. Models are proposed showing the fine structure of the clusters of the amylopectin, that probably originated from different structural domains within the starch granules.