Preliminary Study of the Growth of Zygosaccharomyces rouxii, Candida etchellsii, and an Unidentified Yeast as Potential Inoculum for Low-Salt Soy Sauce

Abstract

Soy sauce is one of main condiments that commonly used in many traditional foods in Indonesia. During its fermentation process, this essential condiment fermentation process take up to 4 years before it can be sold commercially. There are two main steps in the fermentation process, which are the solid-state fermentation and brine fermentation. Solid-state fermentation (koji) is conducted mostly by molds, with incubation time around 3 days. The second step is the brine fermentation (moromi). During this fermentation, koji as the solid-state fermentation product, will be immersed into high-salt concentration water. Salt concentration in brine will limit undesired microorganisms growth and halophilic microbes will grow. Several studies has been done to minimize salt content in soy sauce, due to risk of hypertension due to excessive salt consumption. Candida etchellsii and Zygosaccharomyces rouxii are the most common yeasts that has been used in the moromi fermentation. Optimizing Zygosaccharomyces rouxii while decreasing the salt concentration was done in the previous studies. However, issues such as excessive spoilage bacterial growth and reduction in flavor has appeared in moromi that was inoculated with Z. rouxii when the salt concentration was decreased; therefore, potentials of other yeast candidates for low-salt moromi fermentation need to be evaluated. As a preliminary study for potential inoculum in low-salt soy sauce, growth pattern of two other yeasts in low-salt concentration environment and appearance of moromi maintained by the yeasts as closely as possible to the normal moromi were successfully investigated. Candida etchellsii had the highest biomass production and closest appearance compared to the normal moromi compared to the unidentified yeast.