Evaluation of physicochemical, antioxidant, and antibacterial characteristics of kombucha tea enriched with Terminalia citrina

With the increase in the world population, the demand for healthy and functional products, as well as product diversity, is continuously growing. Certain plants meet this expectation due to their structures that have therapeutic properties in various diseases. In this context, a fermented product was developed by adding extracts of Terminalia citrina (commonly known as yellow myrobalan) to kombucha tea. Laboratory analyses included color analysis, Brix, pH, titratable acidity, Fe3+-Fe2+ reducing capacity, Cu2+-Cu+ reducing capacity, 2,2´-azino-bis(3-ethylbenzthioazoline-6-sulfonic acid) (ABTS·+) radical scavenging and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity, total phenolic content, total flavonoid content, and antibacterial activity determination. In the study, black tea (KTC), kombucha tea with 10 g of Terminalia citrina powder and 10 g of black tea (KTS1), and kombucha tea with 20 g of Terminalia citrina powder (KTS2) were produced. For the KTS2 sample, the total phenolic compound content was found to be 255 µg GAE/mg sample on the 14th day of fermentation and 253.33 µg GAE/mg sample on the 21st day. Additionally, the flavonoid content of the KTS2 sample was determined to be 28.64 µg QE/mg sample on the 21st day of fermentation. The DPPH radical scavenging activity of the KTS2 sample was observed to yield the best antioxidant activity result compared to standard antioxidants (BHA, BHT, and α-Tocopherol) with 7.25 μg/mL on the 14th day of fermentation. The ABTS radical scavenging activity of the KTS2 sample was found to be more effective than standard antioxidants (BHA, BHT, Trolox, and α-Tocopherol) with a value of 2.35 μg/mL on the 21st day of fermentation. In the antibacterial activity analyses, increasing the concentration of Terminalia citrina in kombucha tea led to increased sensitivity against the Staphylococcus aureus ATCC 25923 bacterial strain. In our study, a new functional product with high phenolic compound content, antibacterial and antioxidant properties was developed by adding Terminalia citrina to the increasingly popular kombucha tea, and its physicochemical properties were determined.