1Hokkaido Kushiro Fisheries Experimental Station, Kushiro, Hokkaido 085-0027, 2Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, 3Hokkaido Industrial Technology Center, Hakodate, Hokkaido 041-0801, Japan
The effects of ripening temperature on the chemical and microbiological characteristics of Izushi made of chum salmon (Oncorhynchus keta) were investigated. Izushi were ripened for a cumulative temperature 280°C•d at 5, 10, 15 and 20°C. When ripened at higher temperatures, total acid, volatile basic nitrogen, free amino acid, aerobic bacteria, and lactic acid bacteria obviously increased in Izushi products, and pH values and yields of the products were reduced. For lactic acid bacteria, Leuconostoc mesenteroides was dominant in the Izushi at every ripening temperature. In the Izushi ripened at 5°C, Saccharomyces cerevisiae was dominant for yeast, whereas yeast was not detected in that ripened at 10, 15 and 20°C. In sensory evaluation, Izushi ripened at higher temperatures were not so acceptable as those ripened at at lower temperatures. These results suggested that high-quality salmon Izushi might be produced by ripening at lower temperature for a long period.