Low-salt solid-state soy sauce significantly inhibits microbial activity during fermentation, leading to slower fermentation, reduced flavor compound production, and potentially undesirable flavors.
Low salt content directly impacts the microbial community involved in soy sauce fermentation. Insufficient salt concentration allows salt-tolerant bacteria to proliferate, while beneficial microorganisms such as *Saccharomyces rouxii* and *Saccharomyces globosa* are inhibited. This results in incomplete fermentation, reducing the umami, richness, and aroma complexity of the soy sauce.
Fermentation Speed and Efficiency: In low-salt environments, the metabolic activity of lactic acid bacteria and yeast slows down. Normally, a salt concentration of around 18% effectively inhibits unwanted bacteria while maintaining the activity of beneficial microorganisms. When the salinity is below 12%, fermentation time may need to be extended by 30%-50%, and the final product's total acid and amino acid nitrogen content may not meet the standards for high-quality soy sauce.
Flavor Formation: The unique flavor of soy sauce comes from compounds such as alcohols, esters, and organic acids produced during fermentation. Low salt content weakens the esterification process, resulting in insufficient aroma in soy sauce. It may also lead to the production of off-flavor substances, such as butyric acid, by microbial metabolism, causing unpleasant odors.
Product Quality and Safety: Salt is a natural preservative. Low-salt soy sauce, if not pasteurized or treated with added preservatives, will have a significantly shorter shelf life and is more prone to spoilage, mold growth, or film formation. Furthermore, a low-salt environment may lead to the accumulation of excessive biogenic amines, posing a potential health risk to sensitive individuals.
