Effect of Citrate Treatment on Quality of Fermented Fish-Miso Prepared from Small Horse Mackerel

Abstract

To utilize whole bodies of small Horse mackerel, we attempted to dissolve the fish bone by citrate treatment and prepared fish-miso. The fish were minced, treated by 2.3% (W/W) citrate for 72hr at 4°C, and fermented with 9% (W/W) NaCl and 21% (W/W) Koji at 30°C for 100 days. When compared with the fish-miso without citrate-treatment (MNC), the product with citrate (MWC) contained almost no hard bones (less than approximately 1/8 pretreatment levels). Additionally, the soluble calcium content of MWC was 300mg/100g, whereas that of MNC was 129mg/100g. MWC contained substantial levels of free amino acids (reaching 91% of MNC), suggesting that proteins were efficiently hydrolyzed in the presence of citrate. During the fermentation, proliferation of bacteria in MWC was greatly suppressed, resulting in minute de novo production of major organic acids, such as lactate (except pyroglutamate). Sensory evaluation suggested that the addition of MWC to the miso-soup enhanced umami. This study suggested that citrate-dependent production might be useful for dissolving fish bone, and improving the quality of fish-miso prepared from whole bodies of small fish.