# Simulate the natural four-season fermentation system for high-salt diluted-state soy sauce brewing: Application in flavor promotion regulation

## TL;DR

This study develops a lab-based system to simulate seasonal temperature changes in soy sauce fermentation, helping maintain consistent flavor year-round.

## Contribution

A novel seasonal temperature simulation system for soy sauce fermentation is introduced, enabling rapid microbial and flavor analysis.

## Key findings

- Low-temperature (15°C) fermentation reduces flavor due to low abundance of Staphylococcus lloydii, Leuconostoc lactis, and Kodamaea ohmeri.
- Adding Staphylococcus lloydii and Kodamaea ohmeri to low-temperature fermentation enhances key aroma compounds like benzene acetaldehyde and ethyl acetate.
- The system allows efficient reinoculation testing to maintain consistent soy sauce flavor across seasons.

## Abstract

The seasonal temperature dependency of soy sauce fermentation poses significant challenges to flavor consistency, particularly under low-temperature conditions (e.g., 15°C in winter), where diminished aroma arises from microbial metabolic constraints. Traditional multi-year field studies to decipher these mechanisms are impractical for rapid industrial optimization. In this study, we present an innovative laboratory-based seasonal temperature simulation fermentation system that precisely replicates climatic conditions (15–37°C) of the Lingnan region, enabling accelerated investigation of microbial dynamics and targeted strain interventions. Our findings revealed that, compared to the 30°C (simulating the autumn season) fermented soy sauce, which exhibits optimal flavor, 15°C (simulating the winter season) had a weaker flavor of soy sauce due to the low relative abundance of specific strains, especially Staphylococcus lloydii, Leuconostoc lactis, and Kodamaea ohmeri. Those three strains were added into the low-temperature fermentation process, Staphylococcus lloydii and Kodamaea ohmeri promoted the formation of soy sauce key aroma compounds, such as benzene acetaldehyde, 1-octen-3-ol, and ethyl acetate. Our research offers the soy sauce industry a feasible tool to efficiently and cost-effectively test the reinoculation of functional microbial strains, thereby ensuring consistent flavor profiles throughout the year.