Differential Prevalence of Spoilage Bacteria in Salmon Fillets during Refrigerated Storage and Identification of Predominant Spoilage Bacterial Species
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Abstract:
Chilled fresh salmon fillets were used for the study; the differential prevalence of spoilage bacteria during storage at 0 ℃ was analyzed by morphological observations and 16S rDNA sequence analysis. In addition, the specific spoilage bacteria were separated and identified using the VITEK 2 automated microbial identification system. The major spoilage bacterial species identified in salmon fillets stored at 0 ℃ during the start of storage (day 0) were Staphylococcus sp., Pseudomonas sp., Pediococcus sp., Micrococcus sp., Aeromonas sp., Carnobacterium sp., and Sphingomonas sp. The phase of spoilage bacteria gradually became unitary with the increase in storage time; a significant decrease was observed in the numbers of Staphylococcus sp., Pediococcus sp., and Micrococcus sp., whereas the Aeromonas sp. and Sphingomonas sp. disappeared completely over time. No significant changes were observed in the Carnobacterium sp; on the other hand, there was a gradual increase in the proportion of Pseudomonas sp., leading to its predominance during the end of the storage time. The sequences, amplified by polymerase chain reaction (PCR), were compared against the sequences present in the National Center for Biotechnology Information (NCBI) database; the phylogenetic tree constructed using the MEGA 5.05 software was used for analysis, and the automated microbial identification system was utilized for all measurements. These results identified Pseudomonas fluorescens to be the dominant spoilage bacterium in refrigerated salmon fillets.
