# A Method of Reducing Salt Content in Fermented Soy Sauce Improves Its Flavor and Quality
## 3 Results and Discussion
### Comparison of the Free Amino Acid Compositions of the Different Kinds of Soy Sauce  
FAAs are gradually released from raw materials through enzyme catalysis, which is closely related to the taste of soy sauce [39; 40]. Principal component analysis (PCA) was performed according to the results of the FAAs determination. The PCA showed that the FAAs in the three kinds of soy sauce were quite different. According to Figure 5a, there are apparent zoning features. The HS soy sauce was located in PC1's positive area, the SR soy sauce was in PC2's positive area, and the LS soy sauce was significantly different from the above two kinds of soy sauce in PC1's and PC2's negative areas. As shown in Figure 5b, the PCA load diagram suggests that 16 FAAs are mainly distributed in the first and fourth quadrants, mainly concentrated in the first quadrant. From PC1, 14 FAAs were positively loaded, and the other two FAAs, arginine and tyrosine, were negatively loaded. The results show that the 14 FAAs in the positive and negative charges were the main representatives of the HS soy sauce. From the perspective of PC2, seven FAAs, including alanine, arginine, and glutamate, were the main FAAs in the SR soy sauce. Moreover, tyrosine was the main component of FAAs in the LS soy sauce.  
According to the taste of the FAAs (umami, sweet, bitter, and flavorless), the three kinds of soy sauce were analyzed by the relative contents of the flavor substances. On the basis of the analysis of the relative contents of the flavor substances in Figure 5c, the SR soy sauce was higher than the other two groups in terms of umami, which shows that this SR soy sauce was better in terms of umami. Regarding sweetness, the SR soy sauce was on the sweet side, while the LS and HS soy sauce were slightly less sweet. In terms of bitterness, the LS soy sauce had high FAA contents, which might be related to the continuous high-temperature fermentation of the LS technology. The other two groups had  
Figure 4: Comparison of the contents of nine organic acids among three soy sauce. The red, blue, and green rings on the left depict several types of soy sauce. The different colored rings and cords on the right side indicate different organic acids. The widths of the cords represent the contents of organic acids (mg/mL).  
lower bitter FAA contents. In terms of unflavored FAAs, the three groups of soy sauce were basically the same.  
The formation rate of AAN can be a good indicator of the degree of protein decomposition in raw materials and the economics of soy sauce [41]. The determined AAN production rates of the three kinds of soy sauce are shown in Figure 5d. As can be seen in Figure 5d, by comparing the three soy sauce, the AAN production rate of the SR soy sauce was 53%, which is significantly higher than that of the LS soy sauce, and it was basically the same compared with that of the HS soy sauce.  
Overall, the SR soy sauce is similar to the HS soy sauce in terms of the amino acid distribution, with a reduced salt content, substantially lower production cost, and practical application value.