[Evaluation of the Capacity to Produce Histamine by Histamine-Producing Bacteria during Storage at 10℃]

Histamine is produced from histidine using histidine decarboxylase of histamine-producing bacteria. However, associated histamine food poisoning demands microbiological controls. Furthermore, studies reported that histamine production by histamine-producing bacteria is affected by temperature. Therefore, to prevent histamine food poisoning, it is desirable to store foods below 4℃. However, it is challenging to maintain the storage temperature of food substances in refrigerators constantly below 4℃. Thus, we investigated histamine production capacity using seven histamine-producing bacterial strains under storage at 10℃, a more reasonable cold storage condition. Subsequently, we examined the variation of histamine production in buffers, the correlation between bacterial density and histamine production quantities, and the growth rate in broths. Results showed that similar levels of histamine were produced in buffers even after 5 days of storage under certain conditions in which histamine-producing bacteria did not grow. Moreover, bacterial density was proportional to histamine production, and the coefficient of determination was more than 0.97, and the bacterial density required to produce 200 μg/mL of histamine during storage at 10℃ was calculated to be 4×10⁷-4×10⁸ CFU/mL. When the initial bacterial density was 10²-10³ CFU/mL, psychrophilic bacteria required 2 or 3 days and mesophilic bacteria required more than 4 days to grow above 10⁷ CFU/mL. The above results suggest that understanding the capacity of histamine-producing bacteria to produce histamine and its growth rate in foods is important for the prevention of histamine food poisoning.