Modelling the extraction of phenolic compounds and in vitro antioxidant activity of mixtures of green, white and black teas (Camellia sinensis L. Kuntze)

The aim of this study was to model the extraction of phenolic compounds and antioxidant activity from mixtures of green, white and black teas (Camellia sinensis) using a simplex-centroid design coupled with multiple regression analysis. White tea showed the highest content of phenolic compounds and in vitro antioxidant activity, while black tea presented the opposite behaviour. The lowest values found in black tea are due to the oxidation of phenolic antioxidants during the fermentation. Gallic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, epigallocatechin, and epicatechin gallate showed a significant correlation (P < 0.05) between all the antioxidant assays. All the mathematical models proposed were significant (P < 0.05) and showed high determination coefficients (R-2 (adj) > 0.80). A simultaneous optimization was performed using the desirability function and the optimum condition to maximize the extraction of epicatechin, epigallocatechin gallate, epicatechin gallate, as well as the antioxidant activity (DPPH and FRAP). The results showed that pure white tea was the best solution for obtaining a higher content of antioxidants.