Formation of Protein Hydrolysate and Its Influencing Factors during the Post-Fermentation of Mucor-Type Douchi, a Chinese Traditional Fermented Soybean Product

This study analyzed the change of protein and its hydrolysate during the post-fermentation of Mucor-type douchi by SDS-PAGE and reversed-phase liquid chromatography (RP-LC). The correlation of free amino acid content with different chemical components and browning intensity was analyzed, and the extracellular enzymes from Mucor were semi-quantitatively detected by the API ZYM system. The results showed that the molecular weight of the final protein hydrolysate was mainly distributed in the range of 11-20 kD. The molecular weight of proteins was reduced rapidly at the early stage (from day 0 to 7), and the polypeptide composition changed greatly. The polypeptide content changed from day 7 to 42. The formation of free amino acids had the highest correlation with the total acid content with a correlation coefficient of 0.972, followed sequentially by the browning intensity and reducing sugar. Using the API ZYM system we detected 6 extracellular enzymes from Mucor. © 2017, China Food Publishing Company. All right reserved.