Effects of Temperature Fluctuation on the Quality and Microbial Growth of Oyster Meat During Simulated Cold Chain Circulation
[Objective]To investigate the effect of temperature fluctuations on the freshness and microbial growth of oyster (Ostreidae) during circulation process,and to provide a theoretical reference for developing microbiological oyster meat preservation and cold chain logistics technologies.[Methods]The pH,water holding capacity,texture,total volatile base nitrogen (TVB-N),malondialdehyde (MDA) and bacterial colony number of oyster meat were analysed under the simulated cold chain (CC) and broken chain (BC) circulation methods.The 16S V3-V4 region of the microorganisms was sequenced at all circulation nodes,and the microbial growth pattern of oyster meat during the circulation process was analysed by sequence information,Alpha diversity index and species composition.[Results]As the circulation time prolonged from 0 to 192 h,the total bacterial count,TVB-N,and MDA content of oyster meat gradually increased,while pH value,water holding capacity,and texture characteristics gradually decreased.The freshness of the cold chain group (CC group) was significantly better than that of the broken chain group (BC group) after 96 h of circulation (P<0.05).The results of Alpha diversity analysis showed that the Ace,Chao and Shannon indices of the samples from the CC group were generally lower than those of the BC group at all circulation nodes,indicating that the microbial richness and microbial diversity of the samples from the BC group were higher than those of the CC group;The results of the microbial community composition of the samples during circulation showed that,at the phylum level,the species richness of the Pseudomonadota was maintained at a high level in both circulation modes,especially in the BC group,which was as high as 73.54％ after 192 h of circulation;At the genus level,the dominant genus in the CC group was Pleomorphochaeta,with a relative abundance of 49.66％ at 192 h.The dominant genus in the BC group was Aeromonas,with a relative abundance of 75.42％ after 192 h of circulation.[Conclusion]In the BC group,temperature fluctuation during circulation significantly sped up freshness deterioration of oyster meat compared with the CC group,indicating that temperature fluctuation was closely related to the deterioration of freshness of oyster meat;Pleomorphochaeta and Aeromonas were the dominant genera in the spoilage process of oyster meat during circulation in the CC and BC groups respectively.This study provides an important reference for the temperature setting of oyster meat in the cold chain logistics system and for the development of targeted bacterial inhibition and preservation technology.
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