Optimization of fermentation conditions and analysis of the changes in flavor compounds for lemon vinegar

The flavor composition is an important index to evaluate the quality of fruit vinegar, including volatile and nonvolatile components. The flavor quality of fruit vinegar is related to fermentation technology. This study analyzed the acetic acid fermentation conditions and the changes in the flavor composition of lemon vinegar. After optimization, the pH, alcohol content, and inoculum were 3.0, 6%, and 10%. The statistical analysis showed significant changes in flavor components during the whole fermentation. After acetic acid fermentation, the highest organic acid changed from citric acid to acetic acid. The content of amino acids showed a decreasing trend, mainly used for the growth and metabolism of microorganisms and the precursor of aroma compounds. Terpenoids were the main aroma compounds before the fermentation, while the main aroma compounds were esters after the fermentation. Linalool, the characteristic aroma compound in lemon, was well preserved. Isoamyl acetate was the main aroma compound during the fermentation. Almost all the flavor compounds had significant changes during the lemon vinegar fermentation. This study helps to understand the changes in flavor compounds during lemon vinegar brewing and lays the foundation for further improving the quality of lemon vinegar.