Detection of histamine and histamine-related bacteria in fish-nukazuke, a salted and fermented fish with rice-bran, by simple colorimetric microplate assay

Histamine content and numbers of histamine-forming and histamine-decomposing bacteria in 10 fish-nukazuke (a salted and fermented fish with rice-bran) products (five mackerel-nukazuke, three sardine-nukazuke, one codfish-nukazuke and one puffer-nukazuke) were determined with a simple method using histamine-dehydrogenase microplate assay. Two mackerel-nukazuke and two sardine-nukazuke products showed high content of histamine from 12.6 to 30.5 mg/100 g. The both number of halophilic histamine-forming and histamine-decomposing bacteria were various in the fish-nukazuke products. The histamine content was tended to be low in the product containing high number of halophilic histamine-decomposing bacteria. These results suggest that accumulation of histamine in fish-nukazuke may be affected by histidine content and halophilic histamine-related bacteria.