Histamine-related hygienic qualities and bacteria found in popular commercial scombroid fish fillets in Taiwan

To determine the histamine-related hygienic qualities and bacteria of scombroid fish fillets sold in traditional retail markets, 61 samples were collected from northern and southern Taiwan. It was found that the content of volatile base nitrogen in most samples was below 25 mg/100 g, which is the regulatory level in Taiwan. The ratio of unacceptable samples/total samples for aerobic plate count and Escherichia coli was 100% and 15% in northern samples and 100% and 20% in southern samples, respectively, compared with the requirements of hygienic standards. The average content of various biogenic amines in all samples were lower than 3 mg/100 g, except for histamine average content (4.6 mg/100 g) in southern samples. Among southern samples, four samples contained 12.8 to 28.8 mg/100 g histamine, which is more than 5 mg/100 g that is the allowable limit suggested by the U.S. Food and Drug Administration. Furthermore, 14 bacterial strains were isolated from sailfish fillets on a selective medium for histamine-forming bacteria. These presumptive histamine-forming strains, such as Proteus, Enterobacter, Klebsiella, Rahnella, and Acinetobacter, have been identified and found to produce 20 to 2,000 ppm histamine after incubating at 37degreesC for 24 h.