O que caracteriza a bebida Kombucha? Uma comparação entre infusão de chá verde e café arábica fermentadas por cultura simbiótica de bactérias e leveduras (Symbiotic Culture of Bacteria and Yeasts - SCOBY)

Abstract

Kombucha is a non-alcoholic beverage traditionally obtained by fermenting sweetened Camellia sinensis tea with a biofilm formed by bacteria and yeasts (Symbiotic Culture of Bacteria and Yeasts - SCOBY). The popularity of the beverage has grown due to its availability in different flavors, however, there are still gaps in the knowledge about the fermentation dynamics and metabolites produced during the fermentation process of Kombucha prepared with different raw materials. In this sense, the objective of this work was to verify the physicochemical, microbiological and chromatographic profile of Kombucha using Arabica coffee infusion for the first fermentation. Different concentrations of coffee infusion (25-100% v/v) were tested, with green tea as the control treatment. After 14 days of fermentation at room temperature, microbiological, physicochemical (pH, °Brix, total acidity, instrumental color), phenolic compounds, antioxidant and antimicrobial activity, as well as quantification of carbohydrates, ethanol and organic acids by HPLC and volatile compounds by GC-MS were performed. The beverage and the SCOBY presented high populations of lactic acid bacteria (5.0 and 8.4 log UFC/mL, respectively), correlated with the increase in coffee concentration. The coffee treatments presented similar physicochemical changes to the control, with a reduction in pH (3.4-4.0) and sucrose content (37.4-84%), with total acidity ideal (~0.4%) for kombucha. A total of 111 volatile organic compounds were detected, including alcohols, esters, acids, aldehydes and ketones. The residual alcohol concentration (0.05-0.09% v/v) was within the legal limit (≤0.5% v/v). The total color difference between the initial and final times ranged from 2.28 to 16.15, indicating the influence of fermentation on color. There was a tendency to increase phenolic compounds and antioxidant activity after fermentation, more pronounced with increasing coffee concentration. No treatment showed antimicrobial activity. Scanning electron microscopy (SEM) of the SCOBY revealed bacteria and yeasts among bacterial cellulose microfilaments, confirming the bioactivity of the SCOBY in coffee kombucha. This study demonstrated the feasibility of fermenting kombucha with Arabica coffee infusion, resulting in a beverage with physicochemical characteristics similar to the green tea control, opening up new possibilities for the fermented beverage industry.