Antioxidant properties of commercial grape juices and vinegars

Antioxidant activity of commercial red (n = 5) and white (n = 5) grape juices and wine vinegars (n = 5) were determined by the oxygen radical absorbance capacity (ORAC) assay using fluorescein (FL) as fluorescent probe. The ORAC-FL values varied from 14.6 to 25.0 μmol of trolox equivalents/ml for red grape juices, from 3.5 to 11.1 μmol of trolox equivalents/ml for white grape juices, and from 4.5 to 11.5 μmol of trolox equivalents/ml for wine vinegars. Differences in the antioxidant activities among grape juice, wine, and vinegar were attributed to their different phenolic contents and compositions and to other non-phenolic antioxidants present in the samples. These data confirm grape juice and wine vinegar as good dietary sources of antioxidants.