Comparative Evaluation of Kaempferia galanga L, Clitoria ternatea L., and Hibiscus sabdariffa L. as Kombucha Substrates: Physicochemical Properties and Antioxidant Activity

Herbal kombuchas have been widely studied. However, comparisons among different herbal kombuchas remain difficult as most previous studies were conducted independently under different fermentation conditions and employing different evaluation methods. This study aimed to compare roselle (Hibiscus sabdariffa L.), aromatic ginger (Kaempferia galanga L.), and butterfly pea (Clitoria ternatea L.) as kombucha substrates under standardized fermentation conditions by integrating biochemical profiling with consumer acceptance data. The three herbal kombuchas were fermented for 7 days at room temperature (25 ±2^oC). Total acidity, antioxidant activity, and vitamin C content were evaluated using acid-base titration, the FRAP assay, and the DCPIP titrimetric method, respectively. Sensory acceptance was determined through a hedonic test involving 45 panelists. Differences among kombucha samples were statistically analyzed, and significance was determined at p < 0.05. The highest contents of ash (minerals), protein, and carbohydrate were observed in aromatic ginger kombucha, with values of 0.12 ±0.023%, 0.43 ±0.244%, and 10.14 ±0.728%, respectively. Aromatic ginger kombucha had the highest total acidity (2.648 ± 0.049 g acetic acid equivalents/100 mL) and FRAP antioxidant activity (1.0254 µmol TE/mL), followed by roselle kombucha and butterfly pea kombucha. Ascorbic acid (vitamin C) content remained similar among all kombucha samples. Aromatic ginger kombucha also received the highest sensory acceptance score. As the first standardized comparative study integrating biochemical and consumer acceptance data for these three herbal substrates, this study suggests that aromatic ginger is the most promising substrate for producing kombucha with favorable antioxidant properties and consumer acceptability.