Short communicationEvaluation of Non-bacterial factors contributing to histamine accumulation in fish fillets

Histamine is one cause of scombroid foodborne poisoning. The bacterial decarboxylation of amino acids leads to the formation of biogenic amines such as histamine. This study examined histamine accumulation in tuna and yellowtail fillets that had been sterilized by gamma irradiation to confirm whether factors other than bacterial activity are able to induce histamine accumulation. Fish fillets were sterilized by gamma irradiation at 35 kGy and stored for 7 days at 5, 15, or 25 °C, and the resulting histamine concentrations were measured. The histamine concentrations in all tested samples of tuna and yellowtail were below the detection limit of the assay used (<10 mg/kg). In contrast, the tuna and yellowtail meats inoculated with Morganella morganii, a known histamine-producing bacterium, showed significant histamine accumulation at 15 and 25 °C. These results indicated that non-bacterial factors do not promote histamine accumulation. Therefore, the proper control of histamine-producing bacteria is both necessary and sufficient to prevent histamine accumulation.