| In recent years, many published studies have stated that a diet rich in fruit, vegetables, cereals and grains has a preventive effect against cardiovascular diseases, cancers and other diseases related to ageing. This beneficial action in respect of health has been attributed to the phenolic compounds present in these foods, and largely to the antioxidant capability possessed by these compounds. A notable case, widely studied, is that of the potential protective effect against cardiovascular diseases provided by a moderate consumption of wine. This situation has encouraged the development of numerous methods for measuring antioxidant activity, both in foods and drinks and in body fluids.; In this doctoral thesis a new method has been developed for the measure of the antioxidant power. It is rapid and simple to apply and is based on the electrochemical oxidation of 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). It gives reliable results with the monitoring of only absorbance and time and without the need for oxidizing reagents nor the control of other variables, which are features of most of the methods published. It has been compared with the broadly used “Total Antioxidant Status” test and gives similar but more repeatable results. It requires fewer reagents and avoids the need to control the temperature.; The new electrochemical method has been applied to grape-derived products (grapes, musts, wines, brandies and vinegars) and byproducts (marcs, stalks and dregs). The different extraction methods applied to these products (extraction with pressurized solvent, in solid phase and assisted by ultrasonics) and the analysis procedures of the polyphenolic content by means of the method of Folin-Ciocalteu, high performance liquid chromatography (HPLC) and liquid chromatography coupled to mass spectrometry (LC-MS) are described. It has been confirmed that the antioxidant activity of the grape-derived products and byproducts is highly correlated with their polyphenolic content, and that other majority components in the samples, such as glucose, ethanol, SO 2 or acetic acid, do not interfere in the electrochemical method. |
