Effects of koji fermented phenolic compounds on the oxidative stability of fish miso

In the present study, Aspergillus oryzae-inoculated koji inhibited lipid oxidation in fermented fish paste rich in polyunsaturated fatty acids following a long fermentation period. The fermentation of koji by A. oryzae liberated several bioactive phenolic compounds, including kojic acid and ferulic acid, which were the most abundant. A linear correlation between several phenolic compounds and their bioactive properties, including their radical-scavenging activity, reducing power, metal-chelating activity, and ability to inhibit linoleic acid oxidation was observed. This suggested an important role of koji phenolics in the oxidative stability of fermented fish paste. The activities of different carbohydrate-cleaving enzymes, including α-amylase, cellulase, and β-glucosidase, were positively correlated with the liberation of several phenolic compounds through koji fermentation. Thus, the application of koji offers a novel strategy to enhance the oxidative stability of newly developed fermented fish miso. PRACTICAL APPLICATION: Application of traditional Japanese koji fermentation technique to develop an aroma enriched fish meat bases seasoning has been established. Aspergillus oryzae-inoculated koji releases several carbohydrate-cleaving enzymes, including α-amylase, cellulose, and β-glucosidase, which led to the liberation of several phenolic compounds during fermentation. Improvement of oxidative stability of the fermented fish meat paste by koji phenolics suggests a useful strategy to uplift the value of different trash fish meat-based seasoning through proper utilization of the present technique.