The key enzymes and flavor precursors involved in formation of characteristic flavor compounds of low-salt fermented common carp (Cyprinus carpio L.)

Abstract

Unique flavor is the key quality of fermented fish. In this study, the precursors and key enzymes related to the flavor of Suanyu were analyzed. The results showed that 17 kinds of free amino acids and 22 kinds of free fatty acids were detected during the fermentation. According to variable importance for predictive components values (VIP), amino acids including aspartate, phenylalanine, methionine, glutamic acid, leucine, valine, isoleucine, cysteine and fatty acids including C16:0, C20:5, C20:4, C18:1, C22:6, C18:0 and C16:1 were screened as key precursors affecting the characteristic flavor of Suanyu. Moreover, the changes of enzyme activities in different metabolic processes of flavor were determined. Phosphofructokinase (PFK), pyruvate kinase (PK), lipoxygenase (LOX), hydroperoxidase lyase (HPL) and alcohol acyltransferase (AAT) activities reached the maximum in the first week of fermentation. However, hexokinase (HK), branched chain amino acid transferase (BCAT), aromatic amino acid transferase (ARAT) and esterase activities significantly decreased with the fermentation. Furthermore, ARAT, HPL, esterase, BCAT, AAT and HK were screened as the key enzymes that affected the characteristic flavor of Suanyu. All these results indicated that the control of key flavor precursors and enzymes during fermentation was a potential method to improve the flavor of fermented fish.