Evaluation of new fish sauces prepared by fermenting hot-water extraction waste of stock from dried fish using various kojis

After hot-water extraction of stock from dried fish, most of the waste is usually discarded. However, the waste still contains nutritional components and in this study, an investigation was done to use this waste product to prepare good quality sauce. A new type of fish sauce was developed using hot-water extraction waste of stock from dried fish, and chemical analysis (pH, total nitrogen content, free amino acids, odor ingredients) and sensory analysis of the fish sauce was done. The fish sauce was prepared by fermenting the hot-water extraction waste of stock from dried fish using koji produced from rice, wheat, soybean, and barley. Sensory evaluation of these sauces revealed good umami (savory taste) with a flavor unlike that of conventional fish sauce. Chemical analysis of the prepared fish sauce indicated that fermentation with soybean koji influences taste, whereas fermentation with rice, wheat or barley koji influences flavor. Therefore, the combination of koji mold is important for controlling the taste and flavor of fish sauce. Furthermore, changes in the components and sensory evaluation of fish sauce were observed over time. It was observed that a steep change occurred, and high-quality fish sauce was obtained after six months of fermentation.