# A Method of Reducing Salt Content in Fermented Soy Sauce Improves Its Flavor and Quality
## 3 Results and Discussion
### Determination of Strains and the Additional Amount  
The effect of LAB on the whole sauce mash system is the conversion of sugars into lactic acid, thereby inhibiting the growth of other microorganisms and improving the shelf life of products. Adding LAB during soy sauce fermentation can change the pH of the soy sauce mash system to one more conducive to the growth of yeasts added later. After ultrasonic treatment of the sauce mash in the first three days, _T. halophilus_ was added on the third day. It can be seen from Figure 2a that the addition of _T. halophilus_ can improve the AAN content of soy sauce. After fermentation, the final AAN contents of the 1.0 \(\times\) 10\({}^{6}\) CFU/g _T. halophilus_ fermentation group and the 3.0 \(\times\) 10\({}^{6}\) CFU/g _T. halophilus_ fermentation group were 6.30 g/L and 6.40 g/L, respectively, with no significant difference. In addition, both fermentation groups reached pH values below 5.0 on the 7 th day. Consequently, 1.0 \(\times\) 10\({}^{6}\) CFU/g _T. halophilus_ was selected for economic reasons.  
To improve the quality of the short-term fermentation of soy sauce, different yeasts and their combinations were added in this study. The main types of yeast were _Z. rouxii_, _T. halophilus_, and _C. versatilis_. It can be seen from Figure 2b that the addition of six different kinds of yeast in the early stage of soy sauce fermentation promoted the accumulation of amino acid nitrogen content. At the end of the fermentation, the AAN contents of the No. 7 soy sauce and No. 4 soy sauce were both 7.10 g/L, which is higher than that of the other groups. However, there was no significant difference among the combined  
Figure 2: The variation in the amino acid nitrogen during fermentation with Lactobacillus and yeast: (**a**) addition of _T. halophilus_—no. 1: 0 CFU/g, no. 2: 1.0 \(\times\) 10\({}^{6}\) CFU/g, and no: 3: 3.0 \(\times\) 10\({}^{6}\) CFU/g; (**b**) addition of different kinds of yeast—no. 1: _Z. rouxii_, no. 2: _T. halophilus_, no. 3: _C. versatilis_, No. 4: _Z. rouxii_ + _T. halophilus_, No. 5: _Z. rouxii_ + _C. versatilis_, No. 6: _T. halophilus_ + _C. versatilis_, and No. 7: _Z. rouxii_ + _T. halophilus_ + _C. versatilis_.  
yseats addition groups, so _Z. rouxii_ and _T. halophilus_ were selected because of economic consideration. Among the single addition groups, the effect of _Z. rouxii_ was better than that of _T. halophilus_, and both were better than that of _C. versatilis. Z. rouxii_ and _T. halophilus_ are the most frequently added yeasts in the HS soy sauce process. The main reason is that _Z. rouxii_ and _T. halophilus_ can make the raw materials more fully decompose, and _Z. rouxii_ can be fermented by glucose, maltose, and fructose. _T. halophilus_ was mainly used in the late stage of sauce mash fermentation, which can produce a large number of phenolic substances and other flavoring substances causing fermented soy sauce to possess a strong sauce flavor and a large number of flavor substances. The mixed addition of _Z. rouxii_ and _T. halophilus_ and the mixed addition of _Z. rouxii_, _T. halophilus_, and _C. versatilis_ improved the accumulation of AAN contents in the LS soy sauce in a short amount of time. However, the effect of three kinds of yeast mixed with _Z. rouxii_ and _T. halophilus_ on the soy sauce mash was basically the same. Therefore, the mixed addition of _Z. rouxii_ and _T. halophilus_ in equal proportions was applied to the fermentation process.