Abstract
Kombucha is a fermented tea beverage which is traditionally prepared by fermenting sweetened black or green tea (Camellia sinensis L.) with symbiotic consortium of bacteria and yeasts (SCOBY). In this study, lemon balm (Melissa officinalis L.) was used as the only nitrogen source for kombucha fermentation. During the seven-day fermentation process, pH value, titratable acidity (TA), total phenolic content, phenolic compounds, and antioxidant activity against hydroxyl (˙OH) and 1,1-diphenyl-2-picrylhydrazil (DPPH) radicals were measured to detect the connection between the fermentation time and antioxidant and antibacterial activities of lemon balm kombucha. Antibacterial activity of finished beverages with optimum acidity (TA=4-4.5 g/L), the value which is confirmed by long-time kombucha consumers, and enhanced acidity (TA=8.12 g/L) was tested against eleven wild bacterial strains. The results showed that lemon balm could be successfully used as an alternative to C. sinensis L. for kombucha fermentation. Total phenolic content and antioxidant activity against DPPH radicals of lemon balm fermentation broth were higher than those of traditional kombucha. Rosmarinic acid is the main phenolic compound of the lemon balm-based kombucha that probably provides biological activity of the beverage. Judging from the EC 50 values, kombucha beverages exhibited higher antioxidant activities compared with C. sinensis L. and M. officinalis L. infusions, which can probably be ascribed to SCOBY metabolites. Lemon balm kombucha with both optimum and enhanced acidity showed antibacterial activity, which can be primarily ascribed to acetic acid, but also to some other tea components and SCOBY metabolites.
Highlights
Kombucha is a traditional fermented beverage which originated in northeast China (Manchuria) in 220 BC and was spread to Russia, Germany and the rest of the world [1]
Judging from the EC50 values, kombucha beverages exhibited higher antioxidant activities compared with C. sinensis L. and M. officinalis L. infusions, which can probably be ascribed to symbiotic consortium of bacteria and yeasts (SCOBY) metabolites
Samples were injected into a Waters high-performance liquid chromatography (HPLC) system consisting of 1525 binary pumps, a thermostat and 717+ autosampler connected to a Waters 2996 diode array detector (Waters, Milford, CT, USA)
Summary
Kombucha is a traditional fermented beverage which originated in northeast China (Manchuria) in 220 BC and was spread to Russia, Germany and the rest of the world [1]. Kombucha is sometimes reffered to as tea fungus, mother, or mushroom, the actual fermenting organisms are a symbiotic consortium of bacteria and yeasts, known as SCOBY [2]. This consortium includes acetic acid bacteria (Acetobacter aceti, Acetobacter pasteurianus and Gluconobacter oxydans) and yeasts (Saccharomyces spp., Torulopsis spp., Pichia spp., Bre anomyces spp., Zygosaccharomyces kombuchaensis, etc.) [3,4,5]. The yeasts ferment glucose and fructose to ethanol, which is oxidized by acetic acid bacteria to acetic acid This is the main metabolic path of kombucha fermentation, and acetic acid, ethanol and gluconic acid are the main SCOBY products [1,6]. Other components present in kombucha beverage are sugars, ethyl gluconate, oxalic, saccharic, lactic, keto-gluconic and amino acids, water-soluble vitamins, tea components (catehins, theaflavins, flavonols, etc.) and hydrolytic enzymes (invertase, amylase, etc.) [7,8,9]
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