Enhanced kombucha fermentation with yerba mate and purple pitanga (Eugenia uniflora L.)

This study evaluated yerba mate (Ilex paraguariensis) and purple pitanga (Eugenia uniflora) as substrates for kombucha fermentation, focusing on their effects on microbial growth and bioactive properties of the resulting beverage. Simultaneous optimization revealed that the optimal fermentation conditions are 11.5 g/L of yerba mate, 130.0 g/L of sucrose at 25 °C. The beverage produced with yerba mate reached a pH of approximately 2.5 and an optimal concentration of bioactive components after 10 days, while the mixture of yerba mate and pitanga juice reached the same levels after 7 days of fermentation. The count of bacteria and yeast in the yerba mate was 0.5 log CFU/mL higher than that observed in the mixture containing purple pitanga, which indicates the presence of antimicrobial properties in the juice. Fermentation produces a kombucha that is considered low in caffeine. After 10 days of fermentation, the concentration of glucuronic acid was 1.21 ± 0.01 g/L, which is 86% higher than in the kombucha containing pitanga nectar. However, the levels of ascorbic acid were higher in the pitanga kombucha (0.8 g/L) compared to the yerba mate kombucha (0.33 g/L). Replacing part of the yerba mate infusion with pitanga nectar before fermentation incorporated anthocyanins, enhancing the antioxidant activity, antimicrobial effectiveness against pathogens and anti-glycemic activity of the beverages. These findings indicate the potential to produce fermented beverages containing bioactive compounds through the combined use of yerba mate, pitanga nectar, and kombucha microorganisms.