Optimization of Total Phenolics Content and Total Antioxidant Activity of Black Tea Using Response Surface Methodology

Response surface methodology was used to optimize the fermentation conditions for the total phenolics content and antioxidant activity of black tea (Camellia sinensis). Fresh tea leaves were fermented following a rotatable central composite design of eleven experiments replicated thrice. The minimum and maximum fermentation time and temperature were respectively of 1 - 3 h and 30 - 40 °C. The results demonstrated that fermentation time and temperature significantly affect the total phenolics content and antioxidant activity of black tea. The optimum fermentation conditions for the present study were at 36 °C for 35 min which the values for total phenolics content and total antioxidant activity were 38.99 g GAE/100 g dw and 19.74 mg VitC Eq/100 g dw, respectively. Antioxidant activity was strongly correlated with total phenolics content of black tea.