Fermentation of passion fruit leaf tea with Kombucha inoculum: An upcycling approach for the development of functional fermented beverages

The global demand for innovative functional beverages has driven the search for alternative kombucha substrates that combine health benefits with unique sensory profiles. This study investigates the use of passion fruit (Passiflora edulis) leaf infusion as an alternative substrate for kombucha fermentation. Kombucha prepared with P. edulis infusion (KPE) was compared to traditional green tea kombucha (KCS) regarding their chemical composition (acetic acid, ethanol, and sugar), total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (DPPH and ABTS), antimicrobial activity, and sensory acceptance. After 12 days of fermentation, KPE showed significant pH reduction, sugar consumption, and ethanol production comparable to KCS, but with higher acetic acid levels. Fermentation increased phenolic content in both, while KPE showed a notable increase in flavonoids (78.66 ± 0.036 mg QE/L). Antioxidant activity improved notably against DPPH radicals (82 % inhibition for KPE, 85 % for KCS) after fermentation. Both kombuchas inhibited Staphylococcus aureus (MIC = 125 μL/mL) and gram-negative bacteria (E. coli, Salmonella; MIC = 250 μL/mL). Similar sensory evaluation was observed for both beverages, although KPE was slightly preferred for flavor and overall acceptance and had higher purchase intent. Passion fruit leaf infusion is a suitable medium for kombucha beverage production with desirable level of bioactive compounds and sensory acceptance, making them a promising kombucha substrate. This study adds value to an underutilized byproduct of the passion fruit processing chain and promotes the diversification of kombucha beverages, meeting the demand for functional fermented products with appreciated chemical and sensory profiles.