Identification and inhibition of histamine-forming bacteria in blue scad (Decapterus maruadsi) and chub mackerel (Scomber japonicus).

In this study, we investigated the differences in histamine accumulation between blue scad and chub mackerel and methods of inhibiting histamine-forming bacteria and controlling histamine accumulation in fish. The free histidine contents in blue scad and chub mackerel were 1.45 and 2.75 mg/g, respectively. The histamine-forming bacteria isolated from them were identified as Citrobacter freundii, Citrobacter braakii, and Enterobacter aerogenes using 16S rDNA sequence analysis, the VITEK 2 Compact system, and MALDI-TOF MS. The histamine-producing capacities of C. freundii, C. braakii, and E. aerogenes were 470, 1,057, and 4,213 mg/liter, respectively, after culture at 37°C for 48 h. Among the different antimicrobials and preservatives tested, potassium sorbate and sodium diacetate effectively inhibited the histamine-forming bacteria and their histamine production. After chub mackerel was dipped into 0.5% potassium sorbate or sodium diacetate, its histamine content increased more slowly at room temperature. Therefore, a potassium sorbate or sodium diacetate dipping treatment could effectively control histamine accumulation in fish.