Respostas metabólicas da fermentação do consórcio de Kombucha ao processamento ultrassônico

Abstract

Kombucha is a fermented beverage of Chinese origin, traditionally prepared from green tea and a symbiotic consortium of bacteria and yeasts (SCOBY). It is widely known for its health benefits, as its composition is rich in phenolic compounds, antioxidants, and organic acids. In this study, the effects of ultrasonic processing on metabolic responses during the fermentation of mango-flavored kombucha were evaluated. Three kombucha samples were prepared: Control, US7, and US15. They were obtained by infusing dried Camellia sinensis leaves in hot water, followed by the addition of 3% sucrose (w/v), 20% previously fermented tea (v/v), and 1% SCOBY (w/v). The Control sample was not subjected to ultrasound treatment, while the US7 and US15 samples underwent ultrasonic processing at 19 kHz with an energy intensity of 113 W/cm2 for 7 and 15 minutes, respectively. The first fermentation (F1) was carried out over 9 days. After removing the symbiotic consortium, a second fermentation (F2) was initiated by adding mango juice and continued for 48 hours. The results revealed significant differences in sugar consumption kinetics among the processed kombuchas. During F1, sucrose consumption was higher in the Control sample compared to the ultrasonically treated ones. However, during F2, ultrasonic processing increased sucrose consumption rates in proportion to the ultrasound exposure time, with the US15 sample showing a 19% increase in sucrose consumption. Ultrasound also promoted greater production of gluconic, propionic, and isobutyric acids in the US7 and US15 kombuchas. Gluconic acid concentration increased continuously, reaching a maximum of 6.74 g/L on the 12th day of F2 in the US15 sample, compared to 4.17 g/L in the untreated sample. Notable changes were also observed in the bioactive compound profile: the processed samples showed higher antioxidant activity, as well as increased levels of phenolic compounds and vitamin C. Ethanol content remained below 0.5 g/L in the processed kombuchas, reaching a maximum of 0.46 g/L in US7 and 0.25 g/L in US15 after 28 days of refrigerated storage. Ultrasonic processing, when combined with fermentation, can attenuate the microbiota and modify cellulose fibers, thereby modulating the metabolic activity of the kombucha consortium. The findings of this study contribute to the development of beverages with greater bioactive potential and support the optimization of the kombucha fermentation process.