Process Optimization of Grape Mulberry Compound Fruit Vinegar and the Detection of Flavor Components in Different Fermentation Periods

Using grape and mulberry as raw materials, the optimal fermentation technology of compound fruit vinegar from grape and mulberry by alcohol fermentation and acetic acid fermentation was studied. The ethanol concentration, fermentation temperature, pH and inoculum amount of acetic acid bacteria were used for single factor experiments. The fermentation process of grape mulberry compound fruit vinegar was optimized by response surface methodology with acid production as response value. The results indicated that the optimum fermentation conditions were as follows: Initial ethanol concentration 7.4%, pH5.0, inoculum amount 9.8%, temperature 32 ℃. Under these conditions, the maximum acid yield of fruit vinegar was 5.38 g/100 mL. At the same time, the electronic nose technology was used to detect the different fermentation periods of grape mulberry compound fruit vinegar, which were the fruit juice period before alcohol fermentation, acetic acid fermentation period and fermentation completion period. Combined with principal component analysis (PDA), loading analysis and linear discriminant analysis (LDA), it was determined that the main flavor components of grape mulberry compound fruit vinegar were nitrogen oxides, nitrogen oxides and nitrogen oxides. The order of odor concentration in different fermentation stages was as follows: Finished fruit vinegar>mid fermentation stage>fruit juice. It showed that the electronic nose could accurately distinguish grape mulberry compound fruit vinegar products in different fermentation periods.