Abstract: This study aimed to ascertain the relationships of cathepsin with proteolysis and flavor development in dry-salted Decapterus maruadsi. The fish were processed by two methods to obtain traditional high-salted fish (HS) and low-salted and lactic acid bacteria-fermented fish (LS). The changes in cathepsin B, L, and H activities, proteolysis index (PI) and free amino acid (FAA) contents were measured at different stage of processing. Furthermore, correlation analysis was performed using Pearson’s correlation test. The results showed a similar trend in cathepsin B, L and H activities between HS and LS samples. During the salting stage, cathepsin B, L and H activities in LS fish were higher than in HS fish; however, during drying cathepsin B and L activities in HS fish were higher than in LS fish, indicating HS method is more conducive to cathepsin B and L activities. LS method gave higher cathepsin than HS method during the whole process. The evolutionary trends of PI in LS and HS samples were identical. For both samples, PI and the contents of total free amino acids and total taste-active amino acids significantly increased during drying (P < 0.05); PI and total free amino acid content were higher in HS sample, while higher total content of taste-active amino acids was found in LS sample. Proteolysis by cathepsin B was more pronounced in HS sample. Both cathepsin B and L played an important role in promoting protein degradation and FAA formation, with the former being more effective. Compared with HS method, LS method could improve the percentage of taste-active amino acids as flavor substances while reducing the rate of protein degradation.

Key words: Decapterus maruadsi, traditional high-salted fish (HS), low-salted and lactic acid bacteria-fermented fish (LS), cathepsin, free amino acid, flavor substances