Structure and digestion of hybrid Indica rice starch and its biosynthesis

The fine structure (including contents, size and chains length distribution) of amylose and amylopectin of Hybrid Indica Rice starch have an impact on digestion properties of Indica Rice. Indica Rice starches with different amylose contents were chosen as model materials in this study. The amylose and amylopectin size were characterized using size-exclusion chromatography (SEC), the fine structure of amylopectin were studied by flurophore-assisted carbohydrate electrophoresis (FACE) and parameterized by amylopectin biosynthesis model to identify associations with starch digestibility. The digestograms of all starches fit first-order kinetics. All results show that the hybrid Indica rice starch with higher amylose content has a slower digestion rate. SEC results show that there is no obviously in chains length distribution (CLD) for amylopectin, but a significantly sharp difference in amylose. No difference in amylopectin was also observed from FACE result. The amylose starch controlled by GBSSI enzyme may be the key parameter to influence starch digestion.