A new chemical criteria for white wine: the glutathione equivalent capacity

The present work aimed at showing the interest in applying liquid chromatography with amperometric detection at a silver electrode (LC-EC-Ag) in order to record a chromatogram highly selective to non volatile aminothiols present in white wines. By integrating and summing the peak area of the aminothiols and by normalizing with respect to the peak area of an injected standard solution of glutathione (1 μM) a new quantitative criteria for white wine characterization is proposed namely, the glutathione equivalent capacity (GEC). The LC setup uses a C18 column in isocratic mode and the analysis takes less than 4 min. The wine sample needs no sample treatment other than dilution with the mobile phase. This new methodology and concept is illustrated by the LC-EC-Ag analysis of several white wines of different origins especially Alsace Riesling wines and Riesling grape juice. It is anticipated that in addition to the determination of the GEC, the developed method may be of interest for establishing a white wine "signature" based on the chromatographic profile.