Application of Novel Indigenious Lactic Acid Bacteria and Yeast Co-Culture on Low-Salt Soy Sauce Fermentation

Abstract

Soy sauce fermentation utilize high salt (NaCl) concentration to inhibit spoilage microorganisms while promoting the growth of beneficial halotolerant microorganisms that develops soy sauce aroma. Although the addition of NaCl is essential, high NaCl content in soy sauce has been associated with hypertension. Previous attempts has been made by lowering or substituting NaCl during soy sauce fermentation, however, it resulted in taste alteration. In other food fermentation, addition of starter cultures has been known for ages in aroma development during fermentation. This study aim to select potential starter cultures to compensate the altering soy sauce flavor in low-salt fermentation through analyzing the physicochemical properties and the aroma profile of moromi. This study used three microorganisms, Staphylococcus condiment (SC), Clavispora lusitaniae (CL), and Yamadazyma triangularis (YT). The microorganisms were compared to the commonly used model Tetragenoccocus sp. (TS) and Zygosaccharomyces rouxii (ZR) in high and low-salt concentration, HSC (18% NaCl, TS-ZR) and LSC (6% NaCl, TS-ZR). The microorganisms were further combined as five different combinations of starter cultures, CM-1 (6% NaCl, TS-CL), CM-2 (6% NaCl, TS-YT), CM-3 (6% NaCl, SC-ZR), CM-4 (6% NaCl, SC-CL), and CM-5 (6% NaCl, SC-YT), in low-salt concentration. Soy sauce was prepared through a two-step fermentation process: koji and moromi. The moromi was fermented for a month and analyzed for its physicochemical characteristic, including pH, residual reducing sugar, protein content, and volatile aroma compounds. The pH of low-salt moromi reached ~5.0 at day 4 while it took 21 days for the high-salt control. The final pH was between 4.62 to 4.97 for all samples. The highest amount of residual sugar and protein content were measured in CM-4 at 0.46 mg.mL-1 and CM-1 at 9% w/w respectively. Volatile aroma compounds analysis showed that both salt and starter cultures affect the composition of the volatile compounds in moromi, with acid as the prominent compound in low-salt samples and alcohol in the high-salt sample.