Effectiveness of gamma irradiation in the inactivation of histamine-producing bacteria

Histamine is a cause of scombroid foodborne poisoning. The control of histamine-producing bacteria is a method that can be used to avoid the accumulation of histamine. This study examined the effectiveness of gamma irradiation in inactivating histamine-producing bacteria. The histamine-producing bacteria Morganella morganii (JCM 1672), Enterobacter aerogenes (ATCC 43175) and Raoultella planticola (ATCC 43176) were suspended in tryptic soy broth and were gamma-irradiated at 0.5–4.0 kGy at room temperature. The bacterial populations declined with higher absorbance doses, and the radiation D10 (the dose of radiation required to cause a 90% reduction in the number of survivors) values ranged from 0.32 to 0.42 kGy. Histamine-producing bacteria were inoculated on tuna and were gamma-irradiated; the D10 values were between 0.31 and 0.34 kGy, depending on the type of bacteria. Complete inactivation of the histamine-producing bacteria that were inoculated on tuna was achieved at 4.0 kGy. Although gamma irradiation was effective in controlling histamine-producing bacteria in order to reduce the risk of histamine poisoning, excessive doses were associated with color changes in the tuna.