Abstract
A total of 12 strains of histamine-producing bacteria harboring a pyruvoyl-dependent histidine decarboxylase gene, identified as Tetragenococcus halophilus, were isolated from a fish sauce mash accumulating over 40 mg/100 g of histamine. To confirm that the strain can produce histamine in fish sauce mashes, the representative histamine-producing strain, FS-4, was inoculated into a fish sauce mash. The histamine content of the fish sauce mash inoculated with FS-4 accumulated over 100 mg/100 g of histamine after 7 days at 30℃. In contrast, histamine accumulation was not observed in sterile fish sauce mashes irradiated with over 10.0 kGy of gamma-rays, indicating that the causative agent of histamine accumulation in fish sauce mashes was microorganisms. The addition of starter culture consisting of T. halophilus NBRC12172 (isolated from soy sauce mash), which does not harbor the histidine decarboxylase gene, to the fish sauce mashes effectively suppressed histamine accumulation. According to the result of a competitive growth test between strain FS-4 and starter culture in fish sauce mashes, it is necessary to suppress histamine accumulation during fish sauce fermentation by adding to fish sauce mashes a starter culture with a total biomass more than one thousand times that of the histamine-producing bacterial cells.
