Effect of Tetragenococcus halophilus,Zygosaccharomyces rouxii,and Torulopsis versatilis addition sequence on soy sauce fermentation

The aim of this study was to investigate the effect that the sequences of ingredient addition had on soy sauce fermentation. Five strategies were assessed for the inoculation of Tetragenococcus halophilus, Zygosaccharomyces rouxii, and Torulopsis versatilis. The results of physicochemical analysis and levels of flavor compounds demonstrated that the best strategy for soy sauce fermentation was to inoculate T. halophilus (2 × 10⁵ CFU/mL) on the 15th day, Z. rouxii (1.0 × 10⁶ CFU/mL) on the 30th day, and T. versatilis (1.0 × 10⁶ CFU/mL) on the 45th day; this enhanced its fruity, sauce, alcoholic, and caramel-like flavors by 64.3%, 22.7%, 43.1%, and 36.2%, respectively, and saline taste by 64.3%. Spearman correlation analysis revealed the content of ethanol positively correlated with acetic acid (r = 0.82) and succinic acid (r = 0.80), while the level of formic acid negatively correlated with ethyl phenylacetate (r = −0.88). In summary, these results provided fundamental evidence for strain addition sequence for producing flavor-enhanced soy sauce with potential application in the future.