Relationship between Chain-length Distributions of Waxy Rice Amylopectins and Physical Properties of Rice Grains

Abstract

Chain-length distributions of amylopectins by HPAEC-PAD from japonica and indica waxy-rice samples were characterized, and the relationship between the chain-length distributions and pasting properties of rice flour by RVA and the physical properties of cooked rice grains by Tensipresser were studied. In comparison with jaonica and indica types, the pattern of chain-length distribution of indica amylopectin typically differed, and the ratio of degree of polymerization (DP) 6-12, fa short chains of indica type was clearly lower, while the ratio of DP>13, fb1+2+3 long chains was clearly higher. The physical properties of cooked rice grains and powder pasting of the indica type showed clearly as hard type starch. There were differences in the chain-length distribution among japonica waxy-rice starches. The ratios of fb3, DP>37 for japonica waxy amylopectins were positively correlated with RVA paste viscosity parameters, such as minimum viscosity, final viscosity, pasting temperature and setback, and iodine absorbance. Iodine absorbance was negatively correlated with properties of cooked rice grains, such as overall adhered mass, L6. The results showed the possibility that the long chain portion of the amylopectin structure is a factor in regulating its starch physical properties.