Green Extraction of Antioxidants from Different Varieties of Red Grape Pomace

The extraction yield, phenolic content, anthocyanin content and antioxidant activity of extracts from different varieties of red grapes, Cabernet Sauvignon, Merlot, Petit Verdot, Syrah, Tempranillo and Tintilla, using pressurized green solvents have been analyzed. Two techniques were studied and compared: supercritical fluid extraction (SFE) with CO2 + 20% ethanol and pressurized liquid extraction (PLE) with either ethanol, water or an ethanol/water mixture as the extraction solvents. The Petit Verdot variety allowed the highest global and phenolic yield, and antioxidant activity. The best conditios for PLE obtained from the experimental design and kinetic study were 50% ethanol/water as the pressurized solvent at 90 bar, 120 degrees C, a flow rate of 5 g/min and, an extraction time of 90 min. A statistical analysis of variance has been performed and it was found that temperature is the only variable that has a statistical influence on the extraction yield. The antioxidant activity levels of the extracts are very promising and they are similar to those obtained with the antioxidant tocopherol.