Effects of microbial growth inhibition by antibiotics on the production of taste-active components during the processing of heshiko produced by aging salted mackerel with rice bran.

To elucidate the role of microbes and endogenous proteases in the formation of the taste-active components during processing of heshiko, a Japanese traditional seafood produced by aging salted mackerel with rice bran, the production of lactic acid, free amino acids, and acid-soluble peptides throughout the aging process was compared in the absence and presence of antibiotics including chloramphenicol, penicillin, and cycloheximide. Although viable counts on fish flesh on a 2.5% NaCl-GYP agar plate increased to 10 cfu/g with the aging process of heshiko in the absence of the antibiotics, adding the antibiotics suppressed the increase in viable counts to less than 10 cfu/g throughout the aging process. Lactic acid barely increased due to the suppression of microbial growth by the antibiotics. In spite of the inhibition of bacterial growth throughout the processing of heshiko upon the addition of the antibiotics, little difference was observed in the production of free amino acids and acid-soluble peptides. These results suggest that, unlike lactic acid (which is a fermentation product of lactic acid bacteria), free amino acids and acid-soluble peptides are mainly produced through protein hydrolysis by endogenous proteases in mackerel meats during the aging process of heshiko. [ABSTRACT FROM AUTHOR]