Molecular structures of rice starch

Abstract

New procedures for the structural analysis of starches are described. The beta-amylolysis limit of the branched component of seven rice amyloses was estimated to be 39% from the relationship between the beta-amylolysis limit and the number of branched molecules. The d.p. n and the proportions of the linear and branched molecules were estimated on the basis of the structures of the amyloses and their beta-limit dextrins. The limiting viscosity numbers [η] showed good correlation with the proportions of the linear and branched molecules, but not with their molecular sizes. The iodine affinity and the [η] of eight rice amylopectins were dependent on the longest chain component, which is lacking in waxy amylopectin but abundant in some indica varieties. The [η] of rice amylopectin showed a good correlation with the proportions of the components with the longest and shortest chains, but not with the molecular size.