BIOTRANSFORMATIONS IN GREEN COFFE KOMBUCHA DURING THE FERMENTATION PROCESS

Kombucha is a traditional beverage, formulated with green tea and fermented with a Symbiotic Culture of Bacteria and Yeast (SCOBY). Recently, various compounds have been used to formulate kombucha, and green coffee beverages may represent an innovative substrate for developing a product with bioactive properties. This study aimed to develop a green coffee kombucha (Coffea canephora var. Robusta) and evaluate the biotransformations during fermentation. The beverage was developed with green coffee extract and sucrose, and fermented at 25 °C in aerobic (first fermentation: 6 days) and anaerobic (second fermentation: 8 days). Every two days, samples were collected and analyzed for soluble solids content, pH, total phenolic compounds content, and antioxidant activity by the FRAP, ABTS, and DPPH methods. The initial total solids content was 5.08 Brix, which gradually decreased until the end of fermentation, reaching 3.93 Brix at 14 days. The initial pH of the beverage was 6.68, and on the second day of fermentation, it quickly reached 2.98. The pH of the beverage remained stable in the remaining fermentation periods, indicating that the most intense transformations in the substrate occurred in the first 48 hours of fermentation. The total phenolic compound content ranged from 179 to 204 mg EAG/L during fermentation; however, no difference was observed between the periods. Variations in antioxidant activity (FRAP: 1.7 to 2.4 mmol ET/L; DPPH: 1.4 to 0.7 mmol ET/L; ABTS: 0.5 a 0.7 mmol ET/L) did not differ statistically. The antioxidant activity did not vary throughout the fermentation process, remaining stable in the beverages. The data obtained in this study revealed that green coffee is a suitable substrate for kombucha preparation and that the bioactive compounds remained stable during processing. The data indicate that the fermentation time can be reduced in order to enable its processing on a commercial scale.