Transformation of Salted Soy Whey by Co- and Sequential Culturing with Zygosaccharomyces rouxii and Tetragenococcus halophilus

This study transformed salted soy whey, a food side stream from pressed bean curd (tofu) production, by fermenting it with Zygosaccharomyces rouxii and Tetragenococcus halophilus with an ultimate goal to develop a soy sauce-like condiment. Different inoculation modes (mono-, simultaneous, and sequential) were investigated for their effect on microbial growth and physicochemical profile change. An antagonistic relationship was observed between Z. rouxii and T. halophilus, significantly suppressing the growth of T. halophilus while not affecting Z. rouxii. The volatile and nonvolatile profiles were consistent across all inoculation modes involving Z. rouxii, which produced aroma compounds like isobutyl alcohol and 3-(methythio)-propanol commonly found in soy sauce. In contrast, T. halophilus primarily produces acetic acid and lactic acid and potentially enhances umami and savory flavors through the conversion of methionine into volatile sulfur compounds. These findings highlight the potential of valorizing salted soy whey for condiment production and the crucial role of Z. rouxii in flavor development.