Effects of origins and fermentation time on the antioxidant activities of kombucha

Effects of kombucha origins and fermentation time on their antioxidant properties were investigated using in vitro free radical scavenging assays. Kombucha from various sources demonstrated different antioxidant activities, and most showed the time-dependent characteristics. The average antioxidant potentials of kombucha after fermenting for 15 days were raised to about 70%, 40%, 49% determined, respectively, by the assays of DPPH, ABTS radical scavenging, and inhibition of linoleic acid peroxidation, while the ferrous ion binding ability was inversely diminished by 81%. The total phenol content increased up to 98% which implied that thearubigin might be subjected to biodegradation during fermentation, resulting in the release of smaller molecules with higher antioxidant activities.