Ferulic acid regulates proso millet starch digestibility through alteration of starch multiscale structure and inhibition of digestive enzymes

This study aimed to investigate the regulatory mechanism of ferulic acid (FA) on proso millet starch (PMS) digestion. When the FA addition amount 0.2 g per g of starch, the relative crystallinity values of nonwaxy PMS (NS)-FA complexes and waxy PMS (WS)-FA complexes were higher by 15% and 6%, and the specific surface area decreased by 0.10 and 0.03 m2/g, respectively. The PMS-FA complexes gradually formed non-V-type inclusion aggregates with increased FA addition. FA could also inhibit digestive enzyme activity by binding to the active sites of α-amylase and amyloglucosidase. Compared with WS-FA, NS-FA complexes were more suitable for the preparation of low-glycemic index foods. The steric hindrance of enzymes by the complex structure and inhibitory effect of FA on the enzymes were the major reasons for the reduced digestibility of starch in complexes. These findings provided evidence for the use of FA to reduce the postprandial glycemic response of starchy foods.