A comprehensive study on Kombucha and its analogues

Abstract

Kombucha is a tea-based, non-alcoholic fermented beverage known for its refreshing scent, anti-microbial and anti-oxidant activity. Traditionally it is produced by fermenting black tea that is sweetened with sucrose and pitched with a SCOBY (a polysaccharide matrix containing yeasts and bacteria) that contains yeast and bacteria. This study aimed to firstly identify the microbial profile of a black tea kombucha produced in Brazil and secondly compare traditional black tea kombucha with analogue kombuchas produced with five alternative substrates, including green tea, white tea, chrysanthemum, honeysuckle and mint infusions. A combination of chemical tests, MALDI-TOF MS and 16s rRNA gene sequencing was used for identification of the microbiota of black tea kombucha. Debaryomyces hansenii and Pichia occidentalis were the most abundant yeasts, while Brettanomyces anomalus, Rhodotorula mucilaginosa and Meyerozyma guilliermondii were also found. Acetobacter tropicalis was the predominate acetic acid bacteria in this culture. Scanning electron microscopy was conducted to examine the ultrastructure of the SCOBY. Both yeast and bacteria were observed and an ultrafine cellulose structure was recorded as well. Throughout the analogue kombucha fermentations, sugars, ethanol and organic acids were monitored by HPLC and volatile compounds were analyzed by GC-MS. The results showed that sugar consumption was substrate- dependent. A total of 46 volatile organic compounds were detected across all kombuchas, including alcohols, esters, acids, aldehydes, ketones and other compounds. The final kombuchas contained compounds that were substrate-specific but also had compounds in common, that were produced during the fermentation. A sensory analysis was carried out by an untrained panel with 58 participants. Mint and green tea kombucha obtained the highest and lowest scores for overall approval, respectively.