Optimization of two-phase extraction of polyphenols from grape skins using response surface methodology

Two phase extraction method was presented for extracting total phenols from grape skins.Based on single factor experiments,the optimal extraction was explored by response surface methodology.Results showed that the extraction yield obtained by static constant temperature water was higher than that obtained by ultrasonic-assisted and ethanol extraction.The optimal extraction conditions were obtained as follows: ethanol-water ratio of 6:4(v/v) and ammonium sulfate concentration 0.1 g/mL,liquid-material ratio of 8:1(mL/g),ascorbic acid concentration 0.7 g/L,extraction time of 2 h,extraction temperature of 50 ℃.Under these optimal conditions,the extraction content of phenol is 12.36 mg/g,which was very close to predicted value.Under the same condition extract twice,extraction rate can reach 94%.