# A Method of Reducing Salt Content in Fermented Soy Sauce Improves Its Flavor and Quality
###### Abstract  
Most commercially available soy sauce is fermented by high-salt liquid-state (HS) fermentation, which has an excessive salt content and a long fermentation period. In this study, a new salt-reduced fermentation (SR) soy sauce technology involving multiple strains of bacteria was developed to reduce consumers' salt intake. The SR soy sauce was found to have an amino acid nitrogen content of 8.40 g/L and over 80 kinds of flavor substances, which were significantly higher than those of low-salt solid-state fermented soy sauce and approximately equal to HS soy sauce. Compared with HS soy sauce, the salt content of the SR soy sauce was reduced by 59.2%, achieving the salt reduction goal. The proportion of unamami amino acids in SR soy sauce reached 32.0% of the total level, enhancing SR soy sauce's quality. Hence, the new fermentation process can decrease salt content and shorten fermentation time. refmented foods; amino acid nitrogen; soy sauce; reduced salt; free amino acids; koji; flavor compounds +
Footnote †: journal: Foods  
020  
of more than 10.0% [11]. The direct reduction in salt content during fermentation can negatively affect a soy sauce's fermentation and pose food safety issues [12], mainly resulting in reduced quality, poor aroma, and the proliferation of spoilage microorganisms in the soy sauce produced using a salt reduction technique, which is related to ecological disorders in the mash during fermentation. Therefore, there is an urgent need to study a salt-reduced fermentation (SR) soy sauce that is high quality and low cost. To enhance the flavor of soy sauce, LAB and yeast are added at different stages of the fermentation process. LAB is typically added during the early stages of soy sauce fermentation, helping to stabilize the pH and total acid values of the system, thereby restricting the growth of spoilage bacteria [13] and promoting the formation of soy sauce flavor and color during the later stages of fermentation by producing various organic acids [2]. At present, the fermentation of soy sauce mainly involves adding _Tetragenococcus halophilus_ (_T. halophilus_), which can withstand high temperatures during soy sauce fermentation and enhance the aroma of soy sauce [14]. Several studies have reported that adding yeast during fermentation gives soy sauce a distinct aroma. Yeast strains, including _Zygosaccharomyces rouxii_ (_Z. rouxii_), _Candida versatilis_ (_C. versatilis_), and _Torulopsis halophilus_ (_T. halophilus_), are commonly added to soy sauce during fermentation [15; 16]. After approximately five months of fermentation, these microorganisms produce a significant number of flavor compounds, including alcohols, acids, esters, phenols, and other substances that impart soy sauce with a unique flavor [17]. The problems of hyperglycemia, hypertension, and hyperlipidemia have always plagued people. A diet high in salt is the main cause of high blood pressure, so reducing daily salt intake has become the primary task for people to ensure their health. Therefore, it is urgent to study an SR soy sauce that has good quality and low cost. Here, a new fermentation technology for SR soy sauce was studied, combining the LS method and HS method. This soy sauce can not only meet health requirements but also reduce the production costs for soy sauce enterprises. This study investigated a new SR method for soy sauce, combining the LS and HS methods. The optimal combination and ratio of the raw materials were determined by the koji enzyme activity. Then, an ultrasonic treatment was applied to the soy sauce mash during the initial fermentation stage to expedite the breakdown of the raw materials and suppress the growth of extraneous bacteria. Subsequently, LAB and different yeast strains were added at different fermentation time points and fermentation temperatures.