Comparative Analysis of Flavor Quality between Traditional and Closed Solid-State Vinegar Brewing Systems

In the traditional solid-state fermentation system, the temperature and humidity fluctuations inside and outside the fermented grains in summer cause poor flavor quality of vinegar. To address this issue, this study integrated high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), an electronic tongue and sensory evaluation to compare the changes and differences in various indices between closed and traditional solid-state vinegar fermentation under different fermentation conditions. The results showed that closed solid-state fermentation exhibited higher efficiency than traditional solid-state fermentation in terms of temperature control, total acid content, non-volatile acid generation rate and reducing sugar consumption rate. Vinegar produced by closed solid-state fermentation showed higher proportion of non-volatile organic acids, faster production of umami free amino acids, and a larger number of volatile flavor compounds, indicating milder taste and more pronounced textural layers. Sensory evaluation showed that the vinegar showed a distinct sour and umami taste with more refreshing overall mouthfeel. In general, closed solid-state fermentation has significant advantages and potential in improving both the fermentation efficiency and product quality, laying a theoretical foundation for stable and high-yield Zhenjiang vinegar production.