Department of Marine Bioscience, Fukui Prefectural University, Obama, Fukui 917-0003, Japan
Effects of temperature and NaCl content on changes in viable count as well as production of taste-active components, lactic acid (LA), free amino acids (FAA), and acid soluble peptides (ASP) in the flesh portion of heshiko were investigated through the aging process of salted mackerel with rice bran. The viable count in GYP agar plate containing 2.5 or 10.0% NaCl under either the aerobic or anaerobic cultivation condition gradually increased with aging period irrespective of the temperature. The elevation of the aging temperature from 10°C to 30°C barely affected the changes of viable count and slightly increased the production of LA, while the production of FAA and ASP was promoted depending on the temperature during the aging process. On the other hand, the reduction of the amount of NaCl added remarkably increased the viable count and the production of LA depending on the actual NaCl content in rice bran, while the increases of FAA and ASP were dependent on the NaCl content in the flesh part of heshiko. These results suggested that the production mechanism of FAA and ASP was different from that of LA and was independent of microbial growth during the processing of heshiko.