Fermentation of kamaboko products using rice and/or red rice koji in ethanol

Kamaboko is a traditional Japanese seafood product. Large amounts of non-standard by-products or kamaboko pieces are discarded during preparation. Tofuyo, a unique fermented soybean protein food produced in the Okinawa prefecture, Japan, is prepared by fermenting tofu (soybean curd) in a soaking mixture. In this study, we applied the tofuyo fermentation method to efficiently utilize kamaboko wastes with the aim of obtaining valuable food products. Rice and/or red rice koji was mixed in ethanol and fermented to prepare the soaking mixture. Ethanol concentration affected the protease activity of the soaking mixture, which influences the texture (hardness) of the fermented kamaboko that can consequently affect consumer preferences; at 20-40% ethanol concentration, protease activity of the soaking mixture decreased by about 20-50% compared to that of the soaking mixture without ethanol, after fermentation for 2 weeks. We also experimentally produced fermented kamaboko using soaking mixtures with ethanol concentrations of 20% and 40%. During fermentation, physical changes in texture and chemical changes in protein components of the fermented kamaboko were investigated. The maximum load values, which characterize the hardness of kamaboko, decreased during ripening. The values were higher in the soaking mixture with 40% ethanol than that with 20% ethanol. Crude protein content decreased during the 2-month fermentation period. However, there was no significant difference in these results between the soaking mixtures at 20% and 40% ethanol concentrations. Furthermore, viable bacterial counts decreased to almost undetectable levels. Collectively, our results showed that fermentation changed the texture of kamaboko; additionally, fermented kamaboko is hygienic owing to the low viable bacterial count.