Effects of Fermentation with Kombucha Symbiotic Culture of Bacteria and Yeasts on Antioxidant Activities, Bioactive Compounds and Sensory Indicators of Rhodiola rosea and Salvia miltiorrhiza Beverages

Kombucha is a well-known fermented beverage traditionally made from black tea infusion. Recent studies have focused on finding alternative materials to create novel kombucha beverages with various health benefits. In this study, we prepared and evaluated two novel kombucha beverages using <i>Rhodiola rosea</i> and <i>Salvia miltiorrhiza</i> as materials. The effects of fermentation with the residue of these plants on the kombucha were also investigated. The antioxidant activities, total phenolic contents, and concentrations of the bioactive compounds of the kombucha beverages were determined by the Trolox equivalent antioxidant capacity test, ferric-reducing antioxidant power test, Folin-Ciocalteu method, and high-performance liquid chromatography, respectively. The results revealed that the kombucha beverages made with <i>Rhodiola rosea</i> and <i>Salvia miltiorrhiza</i> had strong antioxidant capacities and abundant phenolic contents. Additionally, the kombucha fermented with <i>Rhodiola rosea</i> residue had higher FRAP, TEAC and TPC values than that fermented without residue. On the other hand, the <i>Salvia miltiorrhiza</i> kombucha fermented with residue had similar FRAP and TEAC values but lower TPC values compared to that fermented without residue. The correlation analysis showed that gallic acid, salidroside, and tyrosol were responsible for the antioxidant abilities and total phenolic contents of the <i>Rhodiola rosea</i> kombucha, and salvianolic acid A and salvianolic acid B contributed to the antioxidant abilities of the <i>Salvia miltiorrhiza</i> kombucha. Furthermore, the kombucha fermented with <i>Rhodiola rosea</i> residue had the highest sensory scores among the kombucha beverages studied. These findings suggest that <i>Rhodiola rosea</i> and <i>Salvia miltiorrhiza</i> are suitable for making novel kombucha beverages with strong antioxidant abilities and abundant phenolic contents, which can be used in preventing and managing oxidative stress-related diseases.