Effect of fermentation conditions on the formation of ammonium salt in soy sauce

Soy sauce contains several nitrogen-containing compounds, most of which are proteins and their decomposition products during the fermentation process. These compounds include potentially harmful ammonium salts. In this study, the effects of changing the koji making and fermentation conditions of soy sauce on the ammonium salt and amino acid nitrogen content in soy sauce are researched. The results indicate that mixed microbial koji making can significantly influence the ammonium salt content in soy sauce, with the increase in the amount of microbial inoculated, the ammonium salt content exhibited an overall upward trend, and increase the total amount of free amino acids. Besides, the ammonium salt content and brine concentration was a significant negative correlation between the two. Moreover, as the temperature of koji making increases, the ammonium salt content first decreases and then increases, and the content of ammonium salt gradually decreased with the increasing fermentation temperature. This study demonstrates that changes in soy sauce brewing conditions will influence the formation of ammonium salts and amino acid nitrogen in soy sauce, providing a foundation for further optimization of the soy sauce brewing process.