HISTAMINE FORMATION AND BACTERIOLOGICAL QUALITY IN SKIPJACK TUNA (KATSUWONUS PELAMIS): EFFECT OF DEFROSTING TEMPERATURE

ABSTRACT Temperature abuse of skipjack tuna (Katsuwonus pelamis) was carried out in order to assess the histamine formation and bacterial growth in fish‐processing facilities where fish can be exposed to high temperatures for short periods of time. Histamine production and bacteriological quality were monitored under different defrosting time and abuse conditions (4, 10, 15, 25 and 30C). A high‐performance liquid chromatography method involving an isocratic elution was validated for the determination of histamine in the samples. Most of the fish samples showed higher contents than the allowable level, whereas samples stored at 4C had negligible histamine levels. The highest level of histamine formed was 185.21 mg/kg after 96 h of defrosting at 10C. In the samples stored at 30C, the histamine contents markedly increased up to 166.91 mg/kg after 96 h, while the histamine content began to gradually increase following defrosting at 10C. Aerobic plate counts reached 7.2 × 105 cfu/g after 24 h at 25C. The dominant microbial group was the Enterobacteriaceae family throughout the storage period. The optimal temperature for bacterial growth was 30C, whereas the optimal temperature for histamine production was 10C. PRACTICAL APPLICATIONS Skipjack tuna (Katsuwonus pelamis) is much appreciated worldwide because of its abundant population, excellent nutritional value and sensory characteristics. The use of frozen skipjack as raw material is becoming more frequent in the canning industry as a way of expanding production across the whole year. Thus, frequently, there is a crucial phase from defrosting the frozen fish to getting it to the canning process. Therefore, monitoring histamine is a critical task for the seafood industry. To control histamine formation, good fish‐handling techniques should be applied to prevent proliferation and cross‐contamination. In the fishery industry, chilling or low‐temperature defrosting is critical for reducing histamine.