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Correlation of Perceived Wine Astringency to Cyclic Voltammetric Response

¹ Associate professor, Department of Chemistry, Southern Oregon University, 1250 Siskiyou Blvd., Ashland, OR 97520.

Acknowledgments: The author thanks James Kennedy and his research group at Oregon State University for hosting and providing logistical support for this sabbatical research and Southern Oregon University for granting the sabbatical leave in order to pursue this research.

^* Corresponding author (email: petrovis{at}sou.edu; fax: 541 552-6415)

A link between perceived astringency in red wines and the cyclic voltammetric response of those wines is described. Voltammetric current, generated in large part from the B-ring oxidation of flavan-3-ols and malvidin, is significantly correlated to the perceived astringency (R² = 0.68) of a set of red wines having previously undergone sensory evaluation. It is suggested that the concentration-dependent formation of a passivation layer on a glassy carbon electrode, resulting from polymerization of electrooxidized wine phenolics, could be monitored by plotting the ratio of the A-ring:B-ring oxidation current. This current ratio is highly correlated to the perceived astringency (R² = 0.77) and to the sum of the epicatechin and epigallocatechin subunit concentration in the wines as previously determined by phloroglucinolysis (R² = 0.84). These results indicate that electrochemical determination of astringency is correlated to concentration and passivation effects at a glassy carbon electrode. Using simple dilution in a model wine matrix for sample preparation, cyclic voltammetry compares favorably with established analytical methods (e.g., protein precipitation and liquid chromatography) in the effort to correlate analytical response to red wine astringency.

Key words: voltammetry, astringency, phenolics, tannin