Succession of bacterial microbiota in tilapia fillets at 4 °C and in situ investigation of spoilers.

The succession of bacterial microbiota in tilapia fillets during cold storage at 4 °C was investigated employing PCR-DGGE method. Results showed that Pseudomonas was the most dominant genus during entire storage period. Shewanella and Psychrobacter were also always present, but became dominant only after 3 days of storage. Acinetobacter, Brevibacterium, Flavobacterium, Dietzia and Janthinobacterium were always the minor genera, among which Acinetobacter and Brevibacterium disappeared 6 days later, and Dietzia and Janthinobacterium only appeared at the end of storage. Further, the potential spoiler(s) of tilapia fillets at 4 °C were investigated in situ. The spoilage ability of a specific group of bacteria was evaluated as follows: Certain preservatives were selectively added to fillets to inhibit a specific group of bacteria, and then the changes in spoilage degree of fillets were determined. In this way the spoilage ability of the inhibited bacteria was evaluated. Our experiments showed that protamine strongly inhibited Pseudomonas but rarely inhibited Psychrobacter, Acinetobacter and Brevibacterium, but garlic juice, on the contrary, strongly inhibited the latter three but rarely inhibited the former. The mixed preservative, which consisted of protamine and garlic juice, didn't play better than protamine alone in preventing the spoilage of fillets. This indicated that Psychrobacter, Acinetobacter and Brevibacterium contribute little to the spoilage of tilapia fillets.