Histamine content and isolation of histamine-forming bacteria in fish meal and fish soluble concentrate

Forty fish meals and five fish soluble concentrates (FSC) imported to Taiwan were sampled to determine biogenic amines and histamine-forming bacteria. Average levels of water activity (0.8), water content (39.9%), salt content (7.32%), and total volatile basic nitrogen (TVBN) (150.7 mg/100 g) in FSC samples were significantly higher than those of fish meal samples, whereas the average levels of crude fat (3.94%) and crude protein (40.7%) in FSC samples were lower than those of fish meal samples. Thirty-five (87.5%) fish meal samples and 5 (100%) FSC samples had TVBN levels above the decomposition limit level of 30 mg/100 g in fresh fish meat. Average contents of putrescine, cadaverine, histamine, and tyramine in tested samples were higher than those of tryptamine, 2-phenylamine, spermidine, and spermine. Four fish meal samples (10%, 4/40) and 1 FSC sample (20%, 1/5) had histamine levels >20 mg/100 g. Five histamine-producing bacterial strains isolated from fish meal samples producing 1.31–6.21 ppm of histamine in trypticase soy broth supplemented with 1.0% l-histidine (TSBH) were identified as Bacillus licheniformis (three strains), B. amyloliquefaciens (one strain), and B. subtilis (one strain).