Influence of working conditions upon Kombucha conducted fermentation of black tea

Local domestic Kombucha was used in fermentation of 1.5 g l(-1) of black tea (Indian tea, 'Vitamin', Horgos, Serbia and Montenegro), sweetened with 66.47 g l(-1) of sucrose. Inoculation was performed by both 10% and 15% of fermentation broth from previous process. The fermentation was conducted alternatively, at 22 degrees C and 30 degrees C, for 10 days. The samples were analysed after 0, 3, 4, 5, 6, 7 and 10 days, so that their pH values, content of total acids, sucrose, glucose and fructose contents as well as quantity of ethanol were determined. At the same time, experiments were performed on tea inoculated with 10% of fermentation broth, at temperatures 22 degrees C, 30 degrees C and 35 degrees C, for 21 days. The samples were taken after 0, 3, 7, 10, 14, 17 and 21 days and quantity of vitamin C was measured. Experimentally obtained results were analysed and the response functions of glucose, fructose, metabolites and biosynthesized vitamin C were defined. Process duration was found the most influencing on the composition of fermentation products, then temperature and inoculum concentration.