Bacterial growth and histamine formation in mackerel during storage at 0, 4, 15 and 25C were monitored. Histamine production and bacterial multiplication were accelerated with increase of the storage temperature. The highest histamine level of 2,080 mg/kg was detected after 2 days of storage at 25C. Selective media were used for isolation of histamine-producing bacteria (HPB) and the histamine production was confirmed by high-performance liquid chromatography analysis. A total number of 305 strains were isolated from spoiled mackerel and 32 of them were identified as HPB. Most of the HPB were isolated from violet red bile glucose agar. Morganella morganii, Citrobacter braakii, Hafnia alvei and Raoultella planticola were confirmed as high histamine-producing strains, whereas other microorganisms were found to possess weak histamine-producing ability.
In order to effectively inhibit the activity of HPB, it is necessary to have a good understanding of bacterial species contributing to histamine production in mackerel during storage. Therefore, we studied the variation of histamine content and the growth of bacteria related to histamine production in mackerel during storage. Results of this study could be useful to assure the safety of mackerel products by controlling histamine content.