Deciphering the redox signature and reactivity of wines with differential pulse voltammetry

Phenolic compounds, including polyphenols and tannins, contribute to the sensory characteristics of wines and help protect them against oxidation through their reductive properties. Linear or cyclic voltammetry methods were previously reported to monitor specific wine phenolic compounds and decipher on their antioxidant activity. Pulsed voltammetry methods improve selectivity and accuracy and recently raised further interest for wine studies. We report the use of differential pulse voltammetry-DPV to characterize each wine redox profile and reactivity. Without any prior solution preparation, DPV analysis in wine provides curves displaying several oxidation peaks assigned to families of reductive phenolic acids or anthocyanins, flavonoids and tannins. Wine redox profiles vary as a function of their color, winemaking process, grape variety, vintage, etc. DPV and cyclic voltammetry-CV allowed further to study wines when changing their composition in caffeic and gallic acids, demonstrating the reactivity between phenolic species. Finally, the oxidation of a red wine under air and oxygen-saturated conditions was monitored by colorimetric and DPV analyses, directly showing the correlation between color browning, decrease of reductive ability and dissolved oxygen level. This work demonstrates the effectiveness of DPV in directly deciphering the oxidation-reduction processes occurring during winemaking and wine ageing.