Antioxidants from winemaking wastes: a study on extraction parameters using response surface methodology

Winemaking by-products present a high environmental impact due to their considerably high biochemical and chemical oxygen demands. This study is focused on the optimization of the traditional solvent extraction technology of phenols from Pinot Noir grape skins (Vitis vinifera). To such a purpose, the combined effects of the extraction time (9, 19 and 29 h) and the solid-liquid ratio (0.10, 0.20 and 0.30 gDW/mL), were investigated by a 32 full factorial design combined with response surface methodology; total polyphenols, flavonoids and trans-resveratrol extraction yields were used as response variables.Results demonstrated that PinotNoir skins had high levels of both total polyphenols (3.22 mgGAE/gDW) and flavonoids (1.01 mgCE/gDW), being the optimumextraction time 19 h approximately. t-resveratrol was found in a considerable amount (2.24 mg/100 gDW), while the main phenolic compounds analyzed with Reverse Phase-High Performance Liquid Chromatography were gallic acid, catechin and quercetin. A significant linear correlation was found between polyphenols concentration and their antiradical power.