Study on endogenous protease and protein degradation of dry-salted Decapterus maruadsi

Extensive proteolysis and formation of flavor substances occur during the processing of dry-salted fish due to the action of endogenous proteases. This study analyzed the evolution of the endogenous proteases and the relationship between endogenous protease levels and protein degradation during processing. Cathepsin B and L activity increased significantly during the last two stages, while cathepsin H activity decreased non-significantly (residual activity was 92.27%) compared to initial activity levels in fresh fish. Dipeptidyl peptidase (DPP I, IV) activity decreased overall. The activity of three aminopeptidases (arginine aminopeptidase; alanyl aminopeptidase; leucyl aminopeptidase) initially decreased (P < 0.05) then significantly increased (P < 0.05) during the final stage. Principal component analysis indicated that cathepsins B and L had larger influences than cathepsin H on protein degradation and flavor substance formation in dry-salted fish, but the influence of dipeptidyl peptidases and aminopeptidases on protein degradation and flavor substance formation was limited