The objective of the research study was to determine the level of some selected microorganisms in kombucha drinks available in retail trade and to compare the contents of polyphenols and anthocyanins in those drinks and their antioxidant potentials with a drink produced experimentally with the use of a traditional method. The research included 12 commercial drinks and one drink produced experimentally on the basis of green tea with 10 % of sucrose added. In the products studied, the following was determined: number of Acetobacter sp. bacteria, Gluconobacter sp., LAB and yeast, pH, total content of anthocyanins, total content of polyphenols and antioxidant activity. A diffusion method with small columns was applied to assess the antimicrobial activity of kombucha drinks in comparison to the reference strains: E. coli ATCC 35218, Listeria monocytogenes serotype 1/2a (KMSiFŻC), Yersinia entercolitica (PCM 1919), Salmonella enteritidis (ATCC 130764), Bacillus cereus (PCM 2019), Enterococcus faecalis (ATTC 29212), Staphylococcus aureus (ATTC 25923), Saccharomyces cerevisiae (LOCK 14) and Candida albicans (KMSiFŻC). It was found that the beverages declared to be pasteurized (K7 – K12) were free of the microorganisms from the groups under analysis. In other commercial products the predominant microorganism was Acetobacter sp. bacteria and its number ranged 6 × 106 ÷ 1.1 × 107 cfu/ml. In the experimentally produced drink the reported count of yeast cells was 6.5 × 105 cfu/g. The pH value of the products was specific and did not exceed 4.3. The content of anthocyanins in all the commercial drinks ranged 0.2 ÷ 0.3 mg/dl, while in the experimental sample this value was more than twice as high. The content of polyphenols in and the antioxidant capacity of the samples varied and no correlation was found between them and the origin of the product. The presence of organic acids is the main factor to determine the capability of kombucha beverages to inhibit bacteria potentially pathogenic to humans. None of the tested beverages showed antagonism against the tested yeast.
kombucha, fermentation, SCOBY, antioxidant properties