Abstract: The microbial community composition and diversity in Huizhou stinky mandarin fish from Huangshan, Anhui province were investigated by high-throughput sequencing, and the nutritional components, physicochemical properties and texture properties were evaluated in comparison with those of fresh mandarin fish. Meanwhile, the antioxidant activity of stinky mandarin fish hydrolysates prepared with different proteases was tested. The results showed that the microbial community composition in stinky mandarin fish was greatly different from that in fresh mandarin fish, and so was the dominant bacteria. Pseudomonas and Carnobacterium were the predominant genera in fresh mandarin fish, which accounted for 69.30% and 17.33% of the total genera, respectively. Psychrobacter and Vagococcus were the predominant genera in stinky mandarin fish, accounting for 59.96% and 26.97% of the total genera, respectively. The contents of ash, soluble polypeptide and total soluble sugar, and hardness of stinky mandarin fish were higher than those of fresh fish, while the contents of moisture and crude protein, and water activity significantly decreased. Moreover, significant variation in the color parameters a*, b* and L* was found between fresh and stinky mandarin fish. It was found that the composition and abundance of the microflora had a great influence on physicochemical indexes of stinky fermented mandarin fish, which were more largely influenced by Vagococcus than by other bacteria. Scanning electron micrographs (SEM) revealed more significant cell shrinkage and cell shape curling in stinky mandarin fish compared with the fresh fish. After protein hydrolysis of stinky mandarin fish with acid protease, neutral protease, alkaline protease or papain, soluble polypeptide contents significantly increased (P < 0.05). All resulting hydrolysates possessed stronger 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities and reducing power than those of the fermented fish (P < 0.05). In conclusion, this study provides a theoretical reference for the deep processing and utilization of Huizhou stinky mandarin fish.

Key words: Huizhou stinky mandarin fish; microbial diversity; quality characteristics; enzymatic hydrolysate; antioxidant activity