Effect of amino acid composition of yeast extract on the microbial indicators and quality of brewed soy sauce

In this experiment, the effects of adding five types of yeast extracts (Y1-Y5) on the microbial community and quality of brewed soy sauce (SY1-SY5) were studied. The results indicated that Proteobacteria and Frimicutes dominated the microbial community of brewed soy sauce. After adding 5 kinds of yeast extracts, the contents of reducing sugar, total acid, amino acid nitrogen, soluble salt-free solids and volatile flavor components in the soy sauce fermented for 90 d were all increased compared with the brewed soy sauce without adding yeast extracts (CK). Soy sauce with Y1 addition (SY1) (neutral-non-polar, neutral-polar, acidic and basic amino acid mass ratio 40:18:27:15) had the highest intensity of caramel aroma, malt aroma and smoky aroma, and the highest overall aroma score. This research provided new ideas for the regulation of soy sauce fermentation.