Short communicationAnalysis of the growth of histamine-producing bacteria and histamine accumulation in fish during storage at low temperatures

We have previously isolated psychrophilic histamine (Hm)-producing bacteria from fresh fish at low temperatures. Among these were strains that produce high levels of Hm even under low temperatures. In the present study, we inoculated 2 strains of psychrophilic Hm-producing bacteria into swordfish (104 cfu/g), and examined their behavior during storage at low temperatures (4 °C, 10 °C, and 15 °C). The average counts of normal viable bacteria and Hm-producing bacteria, and cumulative Hm levels in the fish were measured over time and analyzed. We detected Hm levels of 300 mg/kg or more in 5 days, and 800 mg/kg or more in 7 days, during storage at 4 °C. At 10 °C, we detected Hm levels of more than 150 mg/kg in 3 days, while at 15 °C, we detected Hm production of ≥200 mg/kg after 36 h. These data indicate that Hm accumulates in fresh fish during storage at low temperatures when psychrophilic Hm-producing bacteria are present. Further, we observe that inadequate storage temperatures cause the accumulation of Hm within a short time.

► Two strains of psychrophilic Hm-producing bacteria were inoculated into swordfish. ►We examined their behavior during storage at low temperatures (4 °C, 10 °C, and 15 °C). ► High amount of Hm accumulates in fresh fish during storage at low temperatures.