In vitro starch digestibility of buckwheat cultivars in comparison to wheat: The key role of starch molecular structure

The objective of this study was to compare the in vitro digestibility of different buckwheat and wheat starch cultivars and establish the relationship between digestibility and structure of buckwheat starch. Structure of starches were analyzed with size exclusion chromatography and fluorophore-assisted capillary electrophoresis. Results showed that the amylose content of Tartary buckwheat starch (TBS) and common buckwheat starch (CBS) was 3-4% lower than that of wheat starch. However, no significant difference in the digestibility was found between them. The fast digestion rate coefficient of TBS was negatively correlated with the amount of long amylopectin chains (24 < DP <= 36), and the total digested starch percentage of CBS was negatively correlated with the amount of medium-long amylopectin chains (13 < DP <= 24). This suggests that the digestibility of fully gelatinized starch had no association with the botanical sources but may be more influenced by starch structure.