Assessment of spoilage potential and amino acids deamination & decarboxylation activities of Shewanella putrefaciens in bigeye tuna (Thunnus obesus)

Two Shewanella putrefaciens strains (00A and 00B) were inoculated into sterile bigeye tuna blocks. The biochemical changes (trichloroacetic acid (TCA)-soluble peptides, total volatile basic nitrogen (TVB-N), ammonia, trimethylamine (TMA), biogenic amines (BAs), free amino acids (FAA), and total amino acids (TAA)), decarboxylation and deamination activities of S. putrefaciens in bigeye tuna blocks were investigated in this study. All indicators, except for histamine, showed that 00A had a stronger spoilage potential than 00B. The extremely low histamine decarboxylation activities of 00A and 00B may be the main reason for the nonsignificant difference (p > 0.05) between the two groups in tuna. Meanwhile, arginine deiminase pathway can produce large amounts of putrescine and energy, and arginine deiminase may be the main rate-limiting enzyme of the whole pathway. Principal component analysis (PCA) revealed that the difference between TCA-soluble peptide and FAA content in the inoculated groups may be the main reason for the difference in the spoilage potential of the two strains.

Automated summary

This study investigated the spoilage potential and metabolic activities of two strains of Shewanella putrefaciens in bigeye tuna blocks. The results showed that one strain, 00A, had a stronger spoilage potential compared to the other strain, 00B, possibly due to its lower histamine decarboxylation activity.