Traditional and flavored kombuchas with pitanga and umbu-caja pulps: Chemical properties, antioxidants, and bioactive compounds

The present study aimed to evaluate the impact of the addition of pitanga (Eugenia uniflora L.) and umbu-caja (Spondia tuberosa) fruits on the physicochemical parameters, volatiles, phenolics (profile and bioaccessibility) and antioxidant capacity of kombucha. All beverages TK (traditional kombucha), PFK (pitanga-flavored kombucha) and UCFK (umbu-caja-flavored kombucha) showed throughout the 7-day evaluation process a reduction in pH, an increase in acidity, and a reduction in the content of soluble solids and sugars (glucose and fructose) that characterize the fermentation process. Higher values and lower sugar losses were found in the flavored kombuchas, showing that the pre-existing levels of glucose and fructose in fruits contributed to sweeter beverages. Acetic, butyric, citric, succinic, and malic acids were identified in all kombuchas, except for the malic acid in PFK. Terpenes were the main volatile compounds described in beverages, which was found to have favored the sensorial profile of PFK and UCFK, as they contributed to the increase and/or appearance of new terpenoids, such as curzerene and beta-caryophyllene. In contrast, TK presented acetic acid as its major component. High antioxidant activity was observed for fruit flavored kombuchas, and among the identified phenolics, epigallocatechin gallate was the most predominant component in all beverages (above 63%). The most bioaccessible phenolics in all kombuchas were caftaric acid (22.38%-29.98%), catechin (17.61%-23.48%) and hesperidin (22.43%-28.47%). After a simulated gastrointestinal digestion, the phenolic contents in all kombuchas reduced, having an influence on the significant drop of the antioxidant capacity. Findings demonstrated that pitanga and umbu-caja contribute to diversify and improve the chemical and bioactive characteristics of the kombucha, revealing a sweeter beverage, with a tendency to fruity aromas.