Effects of variety and growth location on the chain-length distribution of rice starches

Abstract

Five rice varieties with a wide range of amylose content harvested from three different agro-climatic zones (Yanco, Mackay, and Darwin) of Australia are used to explore effects of rice varieties and growth location on the fine structure of rice starches. Number chain-length distributions (CLDs) of amylopectin branches are characterized by fluorophore-assisted carbohydrate electrophoresis (FACE) and parameterized by both empirical subdivision method and biosynthesis-based model. This shows that amylopectin branches with degree of polymerization (DP) ∼6–32 are not affected by both rice variety and growth location, but rice varieties from Yanco tend to have smaller proportions of intermediate (DP∼33–62) and long (DP∼63–100) amylopectin branches than those from Darwin and Mackay. The fitting results of starch biosynthesis model keep consistent with the above observations. Weight CLDs of amylose are parameterized by size-exclusion chromatography (SEC), showing that Yanco rices have significantly higher amylose content and higher proportion of amylose branches with DP∼500–5000. The significant interaction between rice variety and growth location indicates that effects of grow location on these fine structures are rice variety-specific. This study could provide implications of environmental effects on the cooking and eating quality of cooked rice for rice breeders and industry.