Recovery of phenolic compounds from grape seeds: effect of extraction time and solid-liquid ratio.

The aim of this research was to study the recovery of phenolic compounds from grape seeds, by-products from winemaking industries, using ethanolic solid-liquid extraction. For 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(-1)), were investigated (where dw = dry waste). Results demonstrated that Pinot Noir seeds had high levels of both total polyphenols (73.66 mg(Gallic Acid Equivalent) gdw(-1)) and flavonoids (30.90 mg(Catechin Equivalent) gdw(-1)), being the optimum extraction time 19 h approximately. The main phenolic compounds analysed with high performance liquid chromatography were catechin and quercetin with a maximum extraction yield obtained at 29 h (362.23 and 339.35 mg/100 gdw, respectively). Concentration of the polyphenols and their antiradical powers are demonstrated to have a significant linear correlation.