Effects of long-term storage on radical scavenging properties and phenolic content of kombucha from black tea

Kombucha is a fermented beverage. Its consumption has significantly increased during the last decades due to its perceived beneficial effects. For this reason, it has become a highly commercialized drink, industrially produced. However, kombucha is still also a homemade beverage, and the parameters which, besides organoleptic characteristics, define the duration of its potential beneficial properties over time, are poorly known. Therefore, this study aimed to determine the effect of nine-month storage at 4 °C with 30-day sampling on the pH, total phenolic and flavonoid contents, free radical scavenging properties of kombucha fermented from black tea. Our results highlighted that, after four months, phenolic content decreased significantly from the initial value of 234.1 ± 1.4 µg GAE mL-1 to 202.9 ± 2.1 µg GAE mL-1, as well its antioxidant capacity tested by two in vitro models, DPPH and ABTS assays. Concomitantly, the pH value increased from 2.82 to 3.16. The novel findings of this pilot study revealed that kombucha from sugared black tea can be stored at refrigerator temperature for four months. After this period the antioxidant properties of kombucha are no longer retained.