1Hokkaido Kushiro Fisheries Experimental Station, Kushiro, Hokkaido 085-0027, 2Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, 3Hokkaido Industrial Technology Center, Hakodate, Hokkaido 041-0801, Japan
Changes in the organoleptic, chemical, and microbiological characteristics of the salmon Izushi were investigated during the pre-treatment and ripening process at around 5°C. Organoleptically, Izushi became acceptable to eat by ripening for 35 d and subsequently became most suitable to eat ripening for 44 d because of the emergence of a specific Izushi flavor. Ripening proceeded uniformly in the entire Izushi. During the ripening process, pH values of the fish and sub-material portions of Izushi remained below pH 5.0. Organic acids in Izushi were mostly acetic acid due to pickling and vinegared rice. Microbial counts of Izushi did not significantly increase during the ripening process. As to the microbial flora of Izushi, Bacillus sp. became the dominant aerobic bacteria by ripening periods of longer than 14 d, and Leuconostoc mesenteroides subsp. cremoris and Debaryomyces hansenii were dominant for groups of lactic acid bacteria and yeast, respectively, after ripening for 35 d or longer.