# Microbial Community and Functional Analysis of Regionally Produced Traditional Korean Grain Vinegar

## TL;DR

This study explores how microbial communities and fermentation conditions affect the flavor and quality of traditional Korean grain vinegars.

## Contribution

The study identifies key microorganisms and their roles in vinegar fermentation, linking microbial activity to flavor and functional properties.

## Key findings

- Lactobacillus acetotolerans and Acetobacter pasteurianus are key microbes influencing acidity and acetic acid production.
- Five-grain vinegar (YO) produces more complex flavor compounds due to microbial and raw-material interactions.
- Free amino acids like alanine contribute to vinegar sweetness through microbial-fermentation interactions.

## Abstract

This study investigated changes in microbial communities and functional components during the fermentation of traditional Korean grain vinegars collected from various regions as well as the correlations among these components. Microbial community analysis revealed that Lactobacillus acetotolerans was the dominant microorganism, while Acetobacter pasteurianus numbers gradually increased during fermentation, playing a key role in acetic acid production. L. acetotolerans, known to thrive in acidic environments, contributed to increasing the acidity of the vinegar and enhanced its preservative properties. The rise in the levels of organic acids, particularly acetic acid, was influenced by the activity of these microorganisms. Additionally, the production of free amino acids, such as alanine, was influenced by interactions between the fermentation medium and microbial communities, significantly contributing to the vinegar’s sweetness. Volatile flavor compounds exhibited considerable diversity due to changes in microbial communities driven by raw-material differences. In particular, five-grain vinegar (YO) tended to generate more complex and intense flavor compounds, with uniformly elevated levels of aldehydes, acids, and ketones. These findings suggest that raw-material selection and fermentation conditions significantly influence the flavor and functional properties of grain vinegars, providing valuable foundational data for improving vinegar production processes to enhance flavor and functionality.