Abstract: The changes in the quality and microbial population structure of big-eye tuna during cold chain (CK) or logistic process (L1) were analyzed comprehensively, aiming to provide a theoretical basis for the circulation and preservation of aquatic products. The temperature fluctuations under the CK and L1 modes were simulated in this paper. Physicochemical parameters including pH and total volatile base nitrogen (TVB-N) and microbial parameters like total viable count (TVC) and Psychrobacter count (PC) were measured during the two processes, and the microbial diversity was studied by high-throughput sequencing analysis. The results showed that the quality and microbial diversity of the CK group at ?55 ℃ were stable, but the microbial indexes increased considerably at 4 ℃. The pH value of the L1 group decreased first and then increased. TVB-N, TVC and PC of L1 were higher than those of CK, which exceeded the safety limit because of temperature fluctuations after 168 h. The results of high-throughput sequencing showed that the dominant bacteria in the CK group at the end of circulation (SM-HR) were mainly Brochothrix thermosphacta, Endophytes, Ralstonia solanacearum, Acinetobacter spp., Bacillus spp. and Pseudomonas spp., and the main bacteria in the L1 group at the end of circulation (R-FT) were B. thermosphacta, Endophytes, R. solanacearum, Acinetobacter spp., Lysobacter, Pseudoalteromonas spp., Psychrobacter spp. and Shewanella spp..

Key words: Thunnus obesus, high-throughput sequencing, circulation, quality, microbial population