Alternative plant infusions as substrates for kombucha production: fermentation performance and functional properties

ABSTRACT Kombucha is traditionally produced by fermenting sweetened Camellia sinensis tea with a symbiotic culture of bacteria and yeasts. Growing interest in alternative plant-based substrates has created new opportunities for the development of kombucha-type beverages with distinct physicochemical and in vitro bioactive characteristics. This study investigated kombucha-type beverages produced from organic sobacha (buckwheat seed infusion), raspberry leaves, dandelion leaves, and nettle leaves, and compared them with a conventional black/green tea kombucha. Fermentation performance was evaluated through the monitoring of pH evolution, SCOBY biomass production, and metabolite profiling, including carbohydrates, ethanol, and organic acids. In addition, total vitamin C, phenolic and flavonoid contents, antioxidant capacity (DPPH and FRAP assays), and cyclooxygenase-2 (COX-2) inhibitory activity were assessed throughout fermentation. Apart from nettle leaf infusion, all substrates successfully supported kombucha fermentation, although significant differences in fermentation performance, physicochemical characteristics, and functional properties were observed. Black/green tea kombucha exhibited the highest antioxidant capacity and in vitro COX-2 inhibitory activity. Raspberry and dandelion leaf kombuchas showed intermediate antioxidant and COX-2 inhibitory responses while supporting efficient fermentation, whereas sobacha showed comparatively low results for these assays. Nettle-based kombucha developed atypical physicochemical characteristics that limited its suitability under the tested conditions. Overall, the results demonstrate that botanical substrate selection is a key determinant of kombucha fermentation behaviour, physicochemical characteristics, and in vitro bioactive properties. Raspberry and dandelion leaf infusions emerged as promising alternatives to traditional tea, highlighting the potential of locally sourced plant materials for the development of innovative fermented beverages.