# A Method of Reducing Salt Content in Fermented Soy Sauce Improves Its Flavor and Quality
## 3 Results and Discussion
### Determination of New Fermentation Technology
The multiple correlation coefficient R\({}^{2}\) was 0.8917, indicating a good fit between the measured and predicted values. The \(p\)-value of the misfit term in the table (0.5630) was greater than 0.05, indicating that it was not significant. This demonstrates that the AAN was influenced by these four fermentation conditions rather than the noise in the domain. The regression model's significance test and ANOVA results show that the regression model obtained by adopting the response surface method in the experimental design was valid and suitable for the optimization test of the fermentation conditions of the SR soy sauce. The partial regression coefficients of A\({}^{2}\), B\({}^{2}\), C\({}^{2}\), and D\({}^{2}\) in the quadratic terms reached the highly significant level. A quadratic response surface regression analysis was performed on the experimental data using Design Expert 8.0 software, and the simulated equations for the AAN content of the soy sauce with each dependent variable were obtained as follows:  
\[ \begin{array}{l}Y=0.85+0.000A+0.018B+0.040C+0.037D-0.047 AB+0.013 AC+0.010 AD\\ +0.017 BC-0.020 BD-0.020 CD-0.14A^{2}-0.12B^{2}-0.14C^{2}-0.15D^{2}\end{array}  \tag{2}\]  
where \(Y\) is the AAN, \(A\) is the salinity, \(B\) is the ultrasonic time, \(C\) is the mixed yeast addition, and \(D\) is the temperature variation range. The optimal solution of the model was obtained with a salinity of 10.15%, ultrasonic time of 10.2 min, mixed yeast addition amount of 2.40 \(\times\) 10\({}^{6}\) CFU/g, and temperature variation range of 30-41.2 \({}^{\circ}\)C. To test the reliability of the results obtained by the response surface methodology, an actual fermentation process was carried out under the following conditions: salinity of 10%, ultrasonic time of 10 min, mixed yeast addition of 2.50 \(\times\) 10\({}^{6}\) CFU/g,and variable temperature value of 30-41 \({}^{\circ}\)C. The average AAN contents of the SR soy sauce products produced by fermentation under these conditions was 8.40 g/L for three replicate experiments, consistent with the theoretical prediction. Therefore, the optimal fermentation process conditions obtained on the basis of the response surface method are realistic, reliable, and have practical production value. Taken together, a new fermentation process was established. Briefly, seed koji was inoculated in a 6:4 mixture of steamed soybean meal and fried wheat and cultured for 44 h. The koji was then collected, mixed with 10% saline for soy sauce fermentation, and sonicated for 10 min from day 1 to day 3. Lactic acid bacteria (1.00 \(\times\) 10\({}^{6}\) CFU/g) and the mixture of _Z. rouxii_ and _C. versatilis_ (1.25 \(\times\) 10\({}^{6}\) CFU/g each) were separately added on the third and seventh days. The initial fermentation temperature was 42 \({}^{\circ}\)C for 7 days, then cooled down to 30 \({}^{\circ}\)C and increased by 0.5 \({}^{\circ}\)C daily to 41 \({}^{\circ}\)C until the end of the fermentation. The entire soy sauce mash fermentation cycle of the new process was 35 days. A comprehensive comparative study was conducted on the qualities of the soy sauce samples fermented by the new fermentation process and traditional LS and HS fermentations (20% and 12% saline for HS and LS, respectively). The indicators for comparison included the AAN, TN, RS, salt content, color indexes, organic acids, FAAs, and flavor substances.