Effect of Fermentation Time on Bio-Viability of Kombucha Tea

Abstract

Kombucha is a symbiotic system including synergistic effects of yeasts and acetic acid bacteria, produced by the fermentation of tea leaves and the incorporation of kombucha cultures under aerobic conditions. In this study, kombucha samples were produced using different tea leaves (white, green, oolong, black and pu-erh), and the number of lactic acid bacteria (LAB), total yeast (TM), total acetic acid (TAA) and total gluconobacter (TGB) were determined in these samples during the fermentation of 21 days (30°C, dark conditions). Moreover, the survival rates of the present microbiota were investigated by using the in vitro artificial gastrointestinal model depending on the various fermentation periods. On the 12th day of fermentation, the highest vitality rates were obtained for acetic acid bacteria (91.16-99.61%) and gluconobacteria (90.84-99.37%) in artificial gastrointestinal model. At the end of the fermentation period, TAA and TGB counts were 7.77-10.66 and 7.68-9.68 log cfu/mL, respectively. LAB counts increased first, followed by a reduction of 60% due to high acidity (11.17 g/L, as acetic acid) and a decrease in pH (2.82). In terms of antibacterial activity; E. coli was the most sensitive microorganism and Lactobacillus acidophilus was the most resistant microorganism to the elevated acidity. The Kombucha tea produced by Pu-erh tea leaves had the highest antibacterial effect on the microorganisms investigated (p<0.05). In terms of the industrial production of Kombucha tea and the viability of the probiotics, it was concluded that the ideal fermentation period should be 2 weeks, and the fermentation conditions should be standardized in order to maintain its functional properties.