Pressurized liquid extraction of polyphenols from red grape pomace

The objective of this study was to recover polyphenols from red grape process waste by pressurized solvent extraction method. Effect of pressurized liquid extraction parameters (Temperature, extraction time and pH) on the quality and quantitiy of polyphenols as well as DPPH antiradical scavenging activity was investigated using response surface experimental design. The response surface optimization of the extraction of polyphenols from solid winery waste (grape pomace), was studied using pressurized liquid extraction (PLE). An optimization study was performed using 50% ethanol as a solvent and with extraction pressure (1700 psi), temperature (50-120oC), extraction time (20-40 min) and pH (2,5-5) as independent variables. The influence of extraction parameters on the antioxidant capacity (DPPH) and chemical composition of the extract was evaluated. Results indicated that extraction yield changed between 7- 27.67%, total phenol yield between 1.07-11.31%, total flavanol yield 0.76-5.90%, total polymeric procyanidin yield 0.38-3.56%, and total anthocyanin yield 0.04-5,17 mg/100 g. The highest DPPH scavenging activity as 19.81 mg/ml (EC50) was obtained at 120oC, pH 5 and for 20 min extraction condition. Extraction yields as well as total polyphenol yields increased with temperature increase, however, pH lower than 3,75 caused low polyphenol content and higher EC50 values.