Effect of Black Bean Koji Enzyme on Fermentation, Chemical Properties and Biogenic Amine Formation of Fermented Fish Sauce

This study aimed to study the combined effect of pH and sodium chloride on black bean koji enzyme activities and the effects of these enzyme on fermentation, chemical properties, and biogenic amine formation of fermented fish sauce. A pH of 5 was optimal for the amylase and protease activity of the black bean koji enzyme. Higher sodium chloride concentrations exerted more detrimental effects on the protease than the amylase enzyme. Protease activity clearly decreased with sodium chloride concentrations higher than 5%. In contrast, during fish sauce fermentation, the protease activity in samples containing 40% koji increased over 12 weeks of fermentation, which correlated with an increase in total soluble nitrogen. The histamine content in 40% koji fish sauce samples was 13.83-16.86 mg/L, which was lower than the commercial product, and no other biogenic amines were detected. Therefore, active proteolytic enzymes from black bean koji could be used as accelerant enzymes for fish sauce fermentation and reduce the risk of scombroid fish poisoning.