Application of lactic acid bacteria and yeasts as starter cultures for reduced-salt soy sauce (moromi) fermentation

- Comparison of microbiological and biochemical properties of reduced salt and traditional soy sauce.
- Zygosaccharomyces rouxii and Meyerozyma guilliermondii starter enhanced formation of volatile flavor compounds in soy sauce.
- Low biogenic amines formation was observed in reduced salt soy sauce fermentation with Tetragenococcus halophilus starter.

The use of starter cultures (Tetragenococcus halophilus TS71, Zygosaccharomyces rouxii A22, and Meyerozyma (Pichia) guilliermondii EM1Y52) in reduced-salt moromi fermentation was investigated. Reduced-salt moromi fermentation (12%NaCl) with starter cultures was monitored for changes of microbiological and biochemical properties including volatile flavor compounds (VFCs) and biogenic amines (BAs) during three months. The inoculation was done after one-month fermentation with two combinations: TS71 and A22 (L2); and TS71, A22 and EM1Y52 (L3). Controls were 12% salt (CL) and 18% salt traditional (CT) without inoculation. Total bacteria counts significantly increased (P < 0.05) in CL. Total lactic acid bacteria and total yeasts in the reduced-salt moromi with inoculation (L2 and L3) were significantly higher than both controls. Key VFCs including ethanol, 2-methyl-1-propanol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 3-hydroxy-2-methyl-4H-pyran-4-one (maltol) were detected in L2 and L3 at higher levels than the traditional CT. Lower amount of BAs was accumulated in the reduced-salt moromi fermentation, particularly with lactic acid bacterium (L3) than other fermentations. Hence, the reduced-salt moromi fermentation with using starter cultures was therefore feasible for the soy sauce production without undesirable impact on formation of VFCs and safety levels of BAs.