The Research Of Citrus Fruit Vinegar By Mixed Fermentation

Acetic acid bacteria(AAB), an important group of bacteria widely used in the food and beverage industry, is obligate aerobic gram negative bacteria characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. Fruit vinegars are rich in organic acids, amino acids, vitamins, mineral substances, and so on, they also have some physiological functions. So fruit vinegar is born at the right moment. It not only has the general function of vinegar, but also retains the original nutrition ingredient. Therefore, the aim of this study was to provide an initial test of the interactions between microorganisms during the preparation of soy sauce koji and the resulting effects to soy sauce quality.1. Three AAB, identified as Acetobacter pasteurianus, were isolated from Chinese industrial vinegar pei in drastic conditions to improve industrial vinegar quality. Among them, A2 exhibited best resistance on three aspects,the transform ratio by A2 was even well retained by 62.5%(25.8 g/L) at 42℃. And at 30℃, A2 maintained the alcohol-acid transform ratio 34.2%(28.2 g/L) with 12% ethanol. Moreover,A2 was shown to produce acetic acid about 6.6g/L with 6% initial acetic acid, which is the upper limit of Acetobacter. The maximum acid production was achieved at 8% ethanol with 60 g/L.2. This part describes the effect of Lactobacillus plantarum(L.plantarum) was added to citrus fruit vinegar fermentation. According to the production of alcohol and lactic acid, as well as yeast growth, the optimized fermentation parameters were determined as the L.plantarum inoculation amount is 2%, the fermentation temperature is 33 ℃ and the initial p H value is 4. Under the optimal condition for alcohol fermentation, the soluble solid content decreased from 15 °Brix to 2.41 °Brix, the p H of fermentation broth decreased from 4 to 3.74, alcohol degree increased to 7.88%, and the content of lactic acid content reached 2.89 g/L. During the acetic acid fermentation, there was a little change in citrus fruit vinegar, acetic acid production finally was 47.9 g/L. As observed, citric acid content showed a fast decrease from 8.21g/L to 5.46g/L, the amount of malic acid in citrus juice decreased from 1.13g/L to 0.11g/L, lactic acid contents increased from 0 to nearly 2.91g/L, acetic acid and lactic acid were little or no content in citric juice, through the fermentation. For vinegar fermentation, a large amount of acetic acid accumulation, the biggest acetic acid production was 47.9 g/L at 6 day. Moreover, an obvious phenomenon was that lactic acid contents decreased to 0.92g/L. In the end of the fermentation, the content of Arg, Asp, Ser, Ala and Tyr in the mixed fermentation shown a increase than single fermentation. Through the analysis of flavor,mixed fermentation system of citrus fruit vinegar volatile compounds increased more obviously than single fermentation. The antioxidant activity also had distinctly improvement by evaluation of DPPH.