Use of Pecan Shell Extract and Green Tea in a Kombucha-Vinegar-Based Beverage with Enhanced Antioxidant Properties

We aimed to develop kombucha-vinegar beverages inspired by switchel (a beverage that combines apple cider vinegar and ginger extract), using pecan shell aqueous extract (PSE) and green tea infusion (GTI) in the preparation of kombucha vinegar, and to assess its effects on physicochemical characteristics, antioxidant activity, and sensory acceptance. Combinations of PSE and GTI (100:0, 75:25, 50:50, 25:75, and 0:100) were tested as substrates to produce kombucha vinegar with an initial sugar concentration of 80 g/L. After, the initial sucrose concentration was tested (80 to 60 g/L) using two of the previous formulations (50% of PSE and 50% of GTI; 25% of PSE and 75% of GTI), that showed better results in antioxidant capacity and sensory characteristics, particularly bitterness, which was attributed to the addition of higher amounts of pecan nutshell extract (100 and 75%). The formulation with 60 g/L of sucrose and higher pecan shell extract (50%) was chosen, allowing a beverage with less sugar at the end of kombucha fermentation. An increase in antioxidant potential was observed during the fermentations, with this being a highlight of this study. Kombucha vinegar beverages inspired by switchel were developed (50% PSE and 50% GTI, 60 g/L of sucrose), with the use of ginger extract or juice fruits (apple, pineapple, or white grape), in order to make the beverage palatable to consumers. The samples without ginger showed the highest antioxidant capacity values. In the sensory evaluation using acceptability and the check all that apply method (CATA), the beverages without ginger showed acceptability ranging from 74.4% (addition of white grape juice) to 84.0% (addition of pineapple juice), being described as refreshing, healthy, and energizing.