Safety evaluation of Staphylococcus and its application in soy sauce brewing

The strain Staphylococcus PT-1 was isolated from soy sauce mash and whole genome sequencing revealed it didn't contain drug resistance genes and virulence genes. Salt tolerance test showed that PT-1 could withstand 20% NaCl. It was inoculated into a pork broth medium. Through volatile component detection, the content of pyrazine in the fermentation broth was 0.83% pyrazine and 1.36% 2, 5-dimethylpyrazine. When the strain was applied to the brewing process of soy sauce, the contents of total nitrogen and amino acid nitrogen in the resulting product were higher than those in the control group; the contents of ammonium salt and NaCl were lower than those in the control group; the total acid content was similar. Solid phase microextraction-gas chromatography-mass spectrometry was used to detect the volatile components of two finished soy sauce products. Compared to soy sauce fermented by typical means, that added with PT-1 contained unique components, such as 2,5-dimethylpyrazine (1.8027%), 2-methylpyrazine (0.0158%), 3-ethyl-2,5-dimethylpyrazine (0.5809%), and 4-ethyl guaiacol (8.7477%). Sensory evaluation showed that the total score of PT-1-fermented soy sauce was higher than that of the control group and was characterized by full and rich flavor. These results provide new insights for improving the quality of soy sauce by using novel strains for fermentation.