Moromi mash dysbiosis trigged by salt reduction is relevant to quality and aroma changes of soy sauce.

• Salt reduction caused failure of soy sauce fermentation and brought safety problems. • Salt reduction influenced both spoilages and beneficial microorganisms in the moromi. • Yeast and Weissella are positively correlated with many main volatiles in soy sauce. • Spoilages are positively correlated with most unacceptable volatiles in soy sauce. Health concerns related to excessive salt consumption have increased the demand for foods with reduced salt content. However, it is a challenge to perform low salt fermentation of high salt liquid-state (HSL) soy sauce due to the interplay between salt and microorganisms. In this study, ≤12 % (w/v) NaCl led to failed fermentation of HSL soy sauce. At 9 % (w/v) NaCl, amino acid nitrogen decreased to 0.31 g/100 mL, total acid increased to 10.1 g/L, and biogenic amines increased to 904.49 mg/L. With reduced salt, the total number of bacteria (1–2 orders of magnitude) and spoilage bacteria (Bacillus , Kurthia , Staphylococcus saprophyticus , and Lactobacillus pobuzihii) increased, and the total number of functional microorganisms (Weissella , Zygosaccharomyces , and Candida) decreased. Unacceptable volatiles contents were higher in reduced-salt soy sauce than in normal salt soy sauce. Most of the unacceptable volatiles were positively correlated with spoilage bacteria. [ABSTRACT FROM AUTHOR]