Mixed Fermentation Process Optimization And Antioxidant Properties Of Kombucha

Kombucha is a kind of traditional folk acid fermented beverages with a long history. It is produced by fermentation of sweetened tea that is carried out by acetic acid bacteria, yeast and other microorganisms, there are various health care function. The production of Kombucha is mainly open fermentation, which dominated by the inoculation conditions and other conditions such as temperature, and it is susceptible to miscellaneous bacteria pollution, spawn degeneration and other issues. then product quality is difficulty to control, and affecting its industrial development and utilization. In this paper strains isolated from Kombucha for pure mixed fermentation, optimize the fermentation process, preliminary study the metabolism of Kombucha and antioxidant capacity. the main results and conclusions are as follows:1. Changes of metabolites during Kombucha fermention with black tea and green tea. Changes in the number of yeasts and Acetic acid bacteria had similar trends in two kinds of fermentation broth. Two kinds of bacteria have synergistic growth characteristics of coordinated. The number of green tea broth more than black tea broth, Acetic acid bacteria and yeast had synergistic growth characteristics. Total sugar utilization, total acid content, protein content in green tea broth was higher than black tea broth, biofilm growth and change of total acid content had a certain association. The pH of Kombucha broth was stable after 6 days, which showed that Kombucha was mature, the pH values of black tea broth slightly higher than green tea broth.2. Kombucha fermentation process optimization and changes of physical and chemical index in the process of storage. Fermentation conditions of Kombucha be gotten by single factor and the response surface analysis of test, green tea as a medium, Saccharomyces pastorianus Hansen and Acetobacter xylinus combination in a 1:1 ratio, inoculum amount was 10% (v/v), tea concentration was 0.7% (w/v), fermentation temperature was 30℃, sugar concentration was 84.5g/L, fermentation time was 5d. Main physical and chemical index of Fermentation products by treatment was pH 3.22, total sugar content of 77.77 g/L, total acidity of 1.71 g/L, soluble solids content of 7.95%. The products of main physical and chemical index had little change at room temperature and cold storage for four months, the quality of the products remained stable.3. The changes of antioxidant capability of kombucha tea during fermentation. In the further 6 days, the polyphenol content of two fermentation broth had an increasing trend, reducing power also had an upward trend, and hydroxyl and superoxide anion of clear capacity of the two kinds of fermentation broth had a different degree of increase; as the fermentation time incresed, total phenolic content, reducing power, the scavenging capacity of hydroxyl, superoxide anion and DPPH radicals had no change. The total phenolic content had good positive relativity with reducing power, the scavenging capability of hydroxyl and superoxide anion. During the total fermentation, the scavenging capability of DPPH radicals had no obviously change. The total phenolic content, reducing force and DPPH radicals of Green tea broth were higher than that of black tea broth, however black tea broth had significantly stronger scavenging capability of hydroxyl radicals and superoxide than that of green tea broth.