Effect of amino acids composing rice protein on rice starch digestibility

During the digestion of rice, proteins are among the main rice components and are hydrolyzed into amino acids by enzymes. In this study, we evaluated the influence of free amino acids liberated from rice proteins during digestion on rice starch digestibility for exploring the starch digestion mechanisms in the presence of rice protein. The results showed that all the amino acids inhibited the activity of porcine pancreatic α-amylase. Moreover, glutamate (Glu) displayed a mixed-type suppression of porcine pancreatic α-amylase, with a half-inhibitory concentration of 11.67 mg/mL. Amino acids were complexed with rice starch through heat-moisture treatment and the slowly digestible starch content significantly increased from 29.6 to 41.3 g/100 g. The interaction between amino acids and starch increased the ordered and aggregated structure of rice starch. Therefore, the enzyme inhibition and starch structure changes induced by amino acids contributed to the mitigation of starch digestion. These findings will improve our understanding of the relationship between amino acids and starch digestion and provide a theoretical basis for preparing starch-based food with a low glycemic index.