Characterization of the spoilage potential of pure and mixed cultures of bacterial species isolated from tropical yellowfin tuna ( Thunnus albacares )

Aim The spoilage potential of 28 bacterial strains isolated from spoiled raw yellowfin tuna was evaluated. Methods and Results Bacterial species were inoculated in irradiated tuna matrix. Chemical changes, bacterial growth and sensory quality were monitored during aerobic storage at 8°C. Pseudomonas spp., Enterobacter spp. and Escherichia hermanii had no spoiling effect. Brochothrix thermosphacta and Carnobacterium divergens/maltaromaticum developed moderate unpleasant odors. Hafnia paralvei and Serratia spp. released strong off-odors (pyrrolidine, sulfur/cabbage). No bacterial group (except H. paralvei) combined with Pseudomonas spp. deteriorated the sensory quality of tuna. When C. divergens/maltaromaticum was associated with H. paralvei or B. thermosphacta, the odor is close to the naturally contaminated tuna stored on the same conditions. The pH, Total Volatile Basic Nitrogen (TVBN) and Trimethylamine (TMA) were not correlated with the spoilage. Conclusions The bacterial species had a different impact on the sensory quality of the fish. The bacterial interactions leading to an enhancement or an inhibition of the spoilage potential and the bacterial growth. Significance and Impact of Study The Specific Spoilage Organism (SSO) appears to be an association of Lactic Acid Bacteria (LAB) with Enterobacteriaceae or B. thermosphacta. Pseudomonas, often dominant at the sensory rejection time, is not a good quality indicator