Oxygen radical absorbance capacities of grape/wine industry byproducts and effect of solvent type on extraction of grape seed polyphenols

Grape seed powders, byproducts of either winemaking or grape processing, were prepared from Vitis vinifera (Merlot and Chardonnay) and Vitis rotundifolia (Muscadine) species. Water, methanol, acetone and ethanol were tested as extractants on Muscadine seed powder. Antioxidant activities of grape seeds and skins were determined as oxygen radical absorbance capacity with phycoerythrin (ORACPE) for both grape species. The results indicated that aqueous solutions of ethanol, methanol or acetone were better than a single-compound solvent system for extraction of total phenols from Muscadine seed powder. Antioxidant capacities of Chardonnay, Merlot and Muscadine grape seeds were 638, 345 and 311 μmol Trolox equivalent (TE)/g dry weight in decreasing order ( P < 0.05 ) , respectively. (ORACPE) values of Chardonnay and Merlot grape skin powders were similar. Total phenol contents of extracts used to determine the antioxidant capacities of grape seeds and skins had a trend similar to (ORACPE) values. Our results showed that health functional components of grape skin and seed powders from the tested byproducts of grape/wine industry are comparable to those of fruits and vegetables.