Understanding the mechanism of starch digestion mitigation by rice protein and its enzymatic hydrolysates

Starch digestibility strongly depends on the food composition and microstructure formed during food processing. Identifying the interplay among food ingredients is vital to design starch-based foods with low digestibility. In this work, the effects of native and enzymatic (pepsin and pancreatin) hydrolyzed rice proteins on structural features, enzyme activity and digestibility of cooked rice starch were systematically investigated. All protein and its hydrolysates showed potent abilities in mitigating starch digestion. Native and pepsin hydrolyzed proteins increased starch retrogradation extent and thus increased ordered and aggregated structures of cooked starch. Pepsin-pancreatin hydrolyzed proteins displayed anti-retrogradation activity and decreased starch ordered structures, however, increased V-type inclusion complexes and displayed a potent mixed-type (competitive and non-competitive) inhibitory activity against alpha-amylase. Based on these findings, it can be concluded that native and pepsin hydrolyzed proteins decreased starch digestibility via increasing ordered structures of cooked starch, while pepsin-pancreatin hydrolyzed proteins mitigated starch digestion by the synergistic effects of V-type structures enhancement and mixed-type suppression activity against alpha-amylase. The data is of significant to formulate low glycemic health-promoting food products via native or proteolytic proteins complexation.