Measurements of the in vitro antioxidant activity of German white wines using a novel method

Abstract.

This article provides a study of a new method recently reported and its applicability for the measurements of antioxidant activity of several German white wines. The results obtained are compared with those of a commonly used method, total antioxidant status (TAS) measurements. This new method is based on the inhibitory effects by antioxidants scavengers of free radicals on the Briggs-Rauscher (BR) oscillating reaction. The effect consists of an immediate cessation of the oscillatory regime, an inhibition time that depends linearly on the quantity of the antioxidant added, and subsequent regeneration of oscillations. Sixteen German white wines were tested with the new method, recording potentiometrically the inhibition times produced on an active BR mixture. The different results concerning the ranking order of the antioxidant activity of the examined wines is ascribed to the different pH values at which the two testing methods work. The method based on the BR reaction works in fact at pH≈2, which is similar to that of the fluids in the human stomach while the TAS method works at a pH value near that of the blood (pH=7.4). The mechanism of the antioxidant action of phenols contained in the wines at pH≈2 is qualitatively illustrated. The benefits of the novel method are described.