Moderate papain addition improves the physicochemical, microbiological, flavor and sensorial properties of Chouguiyu, traditional Chinese fermented fish

The objective of this study was to investigate the effect of papain on the physicochemical and microbiological properties, volatile compound profiles, and sensorial attributes of Chouguiyu. Papain was applied at a dose of 10, 50, 200, 400 U/g fish. Results showed that papain addition improved the release of free amino acids, essential amino acids, eicosapentaenoi acid (EPA, C20:5n3), and docosapentenoic acid (DPA, C22:5n6), respectively. Lower biogenic amines content, higher the volatile compound concentrations and relative abundance of Lac-tobacillales were also observed. Further results showed that the papain dose group decreased the fermentation time from 10 to 7 days while good organoleptic quality was remained, especially in the 200 U/g dose group. The redundancy analysis (RDA) showed a high correlation between Lactobacillus and the key volatile compounds in the 200 U/g and 400 U/g groups, which indicated that Lactobacillus could contribute to the fatty flavor. In summary, proper papain addition (i.e. 200 U/g or 400 U/g) could reduce biogenic amines contents and maintain acceptable sensorial properties of Chouguiyu in a shorter fermentation time.