Optimization of Ultrahigh-Pressure Extraction of Polyphenolic Antioxidants from Green Tea by Response Surface Methodology

Abstract

A new extraction technique, ultrahigh-pressure extraction, was used to obtain antioxidants from green tea. The response surface methodology was employed to optimize the extraction process. The effects of ethanol concentration (x1, 33.2–66.8 %), pressure (x2, 281.8–618.2 MPa), and liquid/solid ratio (x3, 11.6–28.4 ml/g) on the total phenolic content (y1) and α,α-diphenyl-β-picrylhydrazyl free radical scavenging activity (y2) were investigated. Analysis of variance showed that second-order polynomial models produced a satisfactory fitting of the experimental data with regard to total phenolic content (R2 = 0.9996, P < 0.0001) and antioxidant capacity (R2 = 0.9986, P < 0.0001). The optimal condition determined was as follows: ethanol concentration, 50 %; pressure, 490 MPa; and liquid/solid ratio, 20 ml/g. Under this condition, the maximum total phenolic content and antioxidant activity of 583.8 ± 0.9 mg/g dry weight and 85.6 ± 0.7 % could be achieved, respectively, which were well matched with the predicted value.