Vinegar Quality Deterioration Caused by Gas-Producing Acetilactobacillus jinshanensis and Quality Changes after Heat Treatment

In this study, a gas-producing strain of Acetilactobacillus jinshanensis was isolated from spoiled vinegar. After heat treatment at different temperatures, it was found that this strain was a heat-intolerant one, which could be inactivated at 60 ℃ for 10 min. The effect of A. jinshanensis on the quality of vinegar was studied. The results showed that the total acid, amino acid nitrogen, soluble solids, and sediment contents of vinegar increased significantly, while the reduced sugar content decreased significantly after vinegar quality deterioration caused by A. jinshanensis (P < 0.05). In addition, the total organic acid content increased; the contents of lactic, oxalic, and malic acid increased significantly, the contents of citric and tartaric acid decreased significantly (P < 0.05), while the contents of acetic and succinic acid did not significantly change (P > 0.05). The content of total volatile flavor substances decreased by approximately 50%, with the dominant ones being esters and aldehydes. Based on odor activity value (OAV), it was found that the contents of the main characteristic flavor substances such as 3-hydroxy-2-butanone, 2,3,5,6-tetramethylpyrazine, ethyl acetate, phenethyl acetate decreased after vinegar quality deterioration, and the contents of furfuryl alcohol and isovaleric acid increased, resulting in a bland taste or even off-flavor in vinegar, which was in line with the results of sensory evaluation. Furthermore, low-temperature (60 ℃) heat treatment did not have a significant effect on physicochemical indexes or organic acids, but had a significant impact on the flavor of vinegar (P > 0.05). The heat treatment increased the contents of characteristic flavor substances such as phenylethyl acetate, 3-hydroxy-2-butanone, phenethyl alcohol, and reduced the content of isovaleric acid in spoiled vinegar, thereby improving its flavor. To sum up, contamination with A. jinshanensis has a great impact on the flavor of vinegar, which can be improved by heat treatment to a certain extent.