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-molecular-weight 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. (C) 2000 Elsevier Science Ltd. All rights reserved.