Microflora Composition Variation in Mackerel (Pneumatophorus japonicas) Stored in Refrigerated Seawater, and Isolation and Identification of the Dominant Spoilage Bacteria
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Abstract:
Mackerel stored in refrigerated seawater (RSW) was studied with respect to variation in the microflora composition during storage, as analyzed by selective culture media and 16S rDNA sequence analyses. The dominant spoilage bacteria of mackerel stored with RSW were identified and a phylogenetic tree of the typical strains at the late stage of the storage period was constructed using Molecular Evolutionary Genetics Analysis (MEGA) 5.2 software. The results showed that there were complex microbial communities in the mackerel samples at the initial stage of storage, with the dominant microorganisms being Pseudomonas sp. and Psychrobacter sp., along with small proportions of Paenibacillus sp., Shewanella sp., Bacillus anthracis, and Brevibacterium sp. With extended storage time, the microflora composition gradually became uniform, as a significant decrease and an increase were observed in the proportions of Pseudomonas sp. and Shewanella sp., respectively. The proportions of Shewanella sp. and Enterobacter sp. increased rapidly at the late stage of storage. Overall, the proportion of Shewanella sp. showed an upward trend, with the corresponding viable count becoming dominant by the late stage of storage. Therefore, Shewanella sp. was determined as the dominant spoilage bacteria for mackerel stored with RSW.
