Optimization of ultrasound-assisted enzymatic hydrolysis extraction of tea polyphenols from green tea and their antioxidant activities

Abstract

Production of natural extracts requires suitable processing conditions to facilitate the accumulation and preservation of bioactive ingredients. This study aimed to optimize the conditions for extracting tea polyphenols (TPs) from green tea using ultrasound-assisted compound enzymatic extraction (UACEE) technology with response surface methodology (RSM), based on a three-level, four-variable central composite rotatable design (CCRD). Extracted TPs yields were in the range of 16.48% to 28.77%; the experimental results were fitted to a second-order quadratic polynomial model and showed a good fit to the proposed model (R2 > 0.90). Compared with other ex-traction methods, UACEE exhibited significant advantages in the TPs extraction rate and preservation of catechins composition. The antioxidant activities of these extracts were also analyzed using reducing power and DPPH radical scavenging activity; all extracts showed excellent antioxidant activity in a dose-dependent manner, and UACEE extracts showed the strongest antioxidant activity in vitro.