It has been demonstrated that wine and other products derived from the grape have a high antioxidant capability; as a possible consequence of this, they may have potential benefits for health. The byproducts of the winemaking process represent a source of antioxidant compounds that has been relatively unexploited to date, but that is now the subject of increasing industrial interest. This article describes an approach to the study of the antioxidant activity of grape marcs, stalks, and dregs of both white and red varieties. This activity is compared with the measurements of their content of total polyphenols and of individual polyphenolic compounds, identified and quantified by HPLC. From the results we have been able to establish a positive correlation between the antioxidant activity and the total polyphenolic content of samples, but not with specific compounds.

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A new method for measuring the antioxidant power of wine has been developed based on the accelerated electrochemical oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The calibration (R = 0.9922) and repeatability study (RSD = 7%) have provided good statistical parameters. The method is easy and quick to apply and gives reliable results, requiring only the monitoring of time and absorbance. It has been applied to various red and white wines of different origins. The results have been compared with those obtained by the total antioxidant status (TAS) method. Both methods reveal that the more antioxidant wines are those with higher polyphenolic content. From the HPLC study of the polyphenolic content of the same samples, it is confirmed that there is a positive correlation between the resveratrol content of a wine and its antioxidant power.

A new method, rapid and simple to apply, has been developed to measure antioxidant activity. It is based on the electrochemical oxidation of 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and gives reliable results, with the monitoring of only absorbance and time. It has been compared with the total antioxidant status test and gives similar but more repeatable results. The method has been applied to wines, brandies and vinegars. It has been confirmed that the antioxidant activity of these products is highly correlated with their polyphenolic content, and that other majority components in the samples, such as ethanol, SO 2 or acetic acid, do not interfere in the method.