Improvement mechanism of umami peptides in oyster juice by cooperative enzymolysis of alcalase and trypsin based on peptidomics and molecular docking

Traditional oyster juice is a by-product of dried oyster through stew of whole oyster, leading to few umami components from oyster. In this study, cooperative enzymolysis of alcalase and trypsin was used to improve the umami components of oyster juice. The optimal enzymolysis conditions of oyster juice included enzyme concentration of 0.4% alcalase and 0.1% trypsin, enzymolysis time of 1.5 h, and solid-liquid ratio of 1:8, and the amino acid nitrogen content in these conditions reached 0.53 g/L, obviously higher than that in non-enzymolysis group (0.27 g/L). The total free amino acids and peptides in the oyster juice were significantly improved by cooperative enzymolysis. After identification by peptidomics, 159 umami peptides were screened and 5 most abundant umami peptides were used to reveal the taste mechanism by molecular docking with the umami receptor T1R1/T1R3. Umami peptides mainly interacted with Arg56, Thr55, Glu48 and Arg64 in T1R3 through hydrogen attractive charge, conventional hydrogen bond, and carbon hydrogen bond, while hydrogen bond, interpolated charge, hydrophilicity, ionizability, and solvent accessible surface were the main surface forces. The "DED" structure in umami peptides was prone to interact with T1R3 receptor. This study provides a novel approach for enhancement of umami components in oyster juice.