Behavior of histamine-producing bacteria in shimesaba, raw mackerel salted and marinated in vinegar during processing and storage at various temperatures

To study the behavior of histamine-producing bacteria during the processing and storage of shimesaba , we inoculated histamine-producing bacteria into raw mackerel and then evaluated bacterial counts and histamine content at each shimesaba processing step. Six histamine-producing bacteria— Morganella morganii , Enterobacter aerogenes , Raoultella planticola , Photobacterium damselae (2 strains), and Photobacterium phosphoreum —were inoculated onto the surface of mackerel fillets at various cell densities (no inoculation, 10 4 , and 10 7 cfu ml −1 ). The fillets were then treated according to the common procedure used for processing shimesaba . The concentration of NaCl in brine during the salting procedure was 10 % (w/v), and the main ingredients of the marinade broth were 27 % vinegar, 3.8 % sucrose, 0.3 % sodium glutamate, and 0.1 % sodium succinate. The level of histamine-producing bacteria and of histamine did not increase during the salting and marinating procedures. However, during the storage tests, histamine content increased remarkably in the shimesaba products stored at 10 °C for 3 days, and organoleptical degradation was also observed. However, significant deterioration, based on bacterial count, histamine content, and organoleptic evaluation, was not observed in samples stored at 5 °C. These results indicate that the use of traditional marinade broth during the processing of shimesaba and storage below 5 °C are effective methods for preventing histamine accumulation.