Antioxidant, Antibacterial and Color Analysis of Garlic Fermented in Kombucha and Red Grape Vinegar

Background and Objective: Garlic, in different types, is a very common food ingredient all over the world. Traditionally, garlic is fermented in grape vinegar to produce garlic pickles; in this study, to produce a novel fermented food, garlic was fermented in kombucha beverage; then, antibacterial and chemical properties and color changes of garlics fermented in kombucha and vinegar were compared with each other and those of fresh garlic.Material and Methods: Folin-Ciocalteu assay was performed to evaluate total phenolic contents; free radical scavenging activity was evaluated using 2,2- diphenyl-1-picrylhydrazyl. Disk diffusion method was performed to measure inhibitory activity against testing bacteria. A digital method was designed for color analysis. All data were statistically analyzed by ANOVA test at significant level of (p≤0.05).Results and Conclusion: Fresh garlic extract had the highest inhibitory effect (mean 27.7 mm) against tested bacteria; kombucha fermented garlic showed bigger inhibition zone (mean 21.7 mm) than vinegar fermented garlic (mean 17.9 mm). Anti-staphylococcus aureus activity of fresh garlic was stronger than gentamycin and amoxicillin; inhibitory effect of garlic extracts against tested bacteria was significant in comparison with standard antibiotics. Fresh-garlic extract contained highest amount of phenolic contents; fermentation of garlic in kombucha decreased phenolic content of garlic bulbs by 1.92% and IC50 factor for antioxidant activity was 10.25% higher than fresh garlic; fermentation in vinegar reduced 21% of phenolic contents and IC50 obtained 47.4% higher than fresh garlic. Fermentation of garlic reduces the density of colors and luminosity, but the reduction in garlics fermented in vinegar is more than in kombucha. Appearance of vinegar fermented garlic changed to yellowish and kombucha inclined the color to reddish. Fermentation of garlic in kombucha provides better preservation of biological properties of garlic than in grape vinegar.Conflict of interests: We declare that we have no conflicts of interests

Antioxidant and Antibacterial Activity of Kombucha Beverages Prepared using Banana Peel, Common Nettles and Black Tea Infusions

Backgrounds and Objective: Kombucha is a several thousand years old traditional fermented beverage originated from East. While black tea infusion is the common substrate for preparing kombucha, other herbal infusions can be applied for this reason too. Common medicinal herbs or even waste herbal materials, like banana peel, could be suitable substrates for preparing kombucha analogues. In this study, kombuchas were fermented using nettles leaf and banana peel infusions. Materials and Methods: Herbal infusions were fermented by kombucha fungi. Folin-Ciocalteu assay was performed to evaluate total phenolic contents; Free radical scavenging activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl. Disk diffusion method was performed to measure inhibitory activity against testing bacteria. All data were statistically analyzed by ANOVA test at significant level of p≤0.05. Results and Conclusion: Black tea contained highest amount of phenolics (530.5 ppm gallic acid equivalent) and fermentation decomposed approximately 50% of phenolic contents to 265.5 ppm while phenolic content of nettles infusion and fermented beverage were 173 gAE and 188 gAE respectively and for banana peel, 136.5 gAE and 155 gAE; it indicated increase of phenolic contents due to fermentation that may be cause of protein contents of nettles and banana peel gone under fermentation by lactic acid bacteria. Fermented beverage of three herbs had higher antioxidant potent than infusions. Kombucha from banana peel showed the highest antioxidant activity by inhibiting 94.62% of DPPH. While antioxidant activity of fermented beverages of black tea and nettles leaf were more related to their acetic acid content, it was found that a considerable part of antioxidant activity of banana peel kombucha was due to other acids and phenolics. No antibacterial activity was observed from either of samples. Banana peel, as a waste herbal material, and nettles leaf are good ingredients for being used as substrate to make antioxidant kombucha beverage