Application of tea fungus culture in production of fermented milk beverages

Abstract

Kombucha and fermented milks have again become very popular due to their positive effect on human health. The aim of this work is to investigate possible usage of tea fungus culture as a starter culture for manufacture of fermented milks. Local tea fungus culture was grown on traditional substrate at 28 °C and 42 °C. One group of milk samples was incubated without kombucha and another group was inoculated with 10% of local kombucha beverage. Milk-based samples were incubated at 30 °C and 42 °C and fermentation was stopped when the pH value of samples reached 4.5. Fermentation process was monitored by determination of basic chemical and microbiological parameters. The samples of traditional kombucha beverage incubated at 42 °C after 4-day fermentation had the initial pH and titrabile acidity (4.61 and 0.37 g acetic acid/L) and during the first fermentation day number of acetic acid bacteria dramatically decreased from 6.6 × 105 (CFU/mL) to <1(CFU/mL). Pasteurized milk-based products, with and without kombucha inoculum, incubated at 42°C reached the target pH value in almost the same fermentation time. All milk - based samples fermented at 30°C did not reach the target pH during 24h fermentation. These results suggested that the temperature of 42 °C is not suitable for kombucha fermentation on used traditional substrate. Lactic acid bacteria from pasteurized milk and/or environmental contaminant bacteria probably had the main role in fermentation of milk-based samples.