Isolation, Identification and Spoilage Ability of Dominant Spoilage Bacteria from Channel Catfish

This study was conducted in order to investigate the specific spoilage organisms (SSOs) in cold stored channel catfish and their spoilage ability. Eight strains of spoilage bacteria were isolated and identified from channel catfish at the end of refrigerated storage by traditional selective culture combined with 16S rDNA sequence analysis. Based on the sensory score of channel catfish inoculated with each of the spoilage strains after 0–8 days of storage, four strains of SSOs were selected for identification by their colony and morphology characteristics, physiological and biochemical properties and 16S rDNA sequence. The strains were inoculated into sterile fish fillets and stored at 4 ℃ for up to eight days. The total number of colonies and total volatile basic nitrogen (TVB-N) content were determined during the storage period. The yield factor of spoilage bacteria metabolites (Y_TVB-N) was used as an indicator to measure the spoilage ability of spoilage bacteria. The results showed that the SSOs in channel catfish were two strains of Shewanella putrefaciens, Pseudomonas aeruginosa and Pseudomonas aeruginosa. All the four strains could cause spoilage of sterile fish fillets, with Shewanella having the strongest spoilage ability.