Screening, identification of 4-vinylguaiacol producing yeast and its application in soy sauce

In this study, 4-vinylguaiacol yeast was screened from fermentation mash of traditional soy sauce, the strain was identified by morphological observation, physiological and biochemical experiments and molecular biology techniques. Meanwhile, salt tolerance of yeast was studied and the yeast was applied to soy sauce production. The results showed that one strain of yeast L9-1, which could metabolize 4-vinyl guaiacol, was isolated and screened, and it was identified as Hyphopichia burtonii. Strain L9-1 could tolerate 18% NaCl, grow and metabolize normally in sauce mash, and synthesize 4-vinylguaiacol. When adding ferulic acid 50 mg/L, inoculated strain L9-1 could increase the 4-vinylguaiacol content in sauce mash by 36.2 times, significantly increased the total acid content and decreased the pH and reducing sugar content (P<0.05), but had no significant effects on amino acid nitrogen and salt (P>0.05). Adding 4-vinylguaiacol-enhanced sauce mash into the finished soy sauce could improve the flavor, mellow, char and comprehensive aroma of soy sauce, improve the thickness and comprehensive taste of soy sauce to a certain extent, and alleviate the salty taste, indicating that strain L9-1 had broad application prospects in improving the flavor and quality of soy sauce.