Appropriately raising fermentation temperature beneficial to the increase of antioxidant activity and gallic acid content in Eurotium cristatum-fermented loose tea

•Gallic acid becomes a major antioxidant and quality index in the fermented tea.•E. cristatum fermentation increased the gallic acid and antioxidant ability (p < 0.01).•Fermentation temperature affected the gallic acid and antioxidant ability (p < 0.05).•Gallic acid content formed at 37 °C reached 2.38% similar to that in Galla chinensis.

There were little reports on effects of fermentation conditions on the quality and function of Fu-brick tea. In this study, gallic acid contents and antioxidant properties of Eurotium cristatum-fermented loose tea at different fermentation temperatures were analyzed. The results showed that E. cristatum fermentation had resulted in an obvious increase of the antioxidant ability, and fermentation temperature significantly affected gallic acid and antioxidant ability of E. cristatum-fermented loose tea (p < 0.05). Appropriately raising fermentation temperature significantly contributes to increasing gallic acid content and antioxidant ability of E. cristatum-fermented loose tea (p < 0.05). Gallic acid was significantly correlated with antioxidant activity in E. cristatum-fermented loose tea (p < 0.05), and its content fermented at 37 °C reached 2.38% of the dry weight, similar to that in Galla chinensis. Gallic acid becoming a primary antioxidant can be as a quality index of E. cristatum-fermented loose tea. The results provide a basis for increasing active components and functional activity in microbe-fermented teas by controlling fermentation temperature.