Characterization of wine polyphenols with a carbon/nanoparticle TiO2 electrode

Abstract

The positive effects of polyphenolic compounds on the sensory characteristics of wine and human health indicate a great need for a simple, fast and easily accessible method to determine the content of polyphenols in wine. The aim of this study is the electrochemical characterization of polyphenolic compounds in natural wine samples using a modified carbon paste electrode with TiO2 nanoparticles (MCPE/npTiO2) and improved voltammo­gram processing to obtain indicative data for polyphenols. The most marked influence of the modification of CPE with TiO2 nanoparticles was an increased sensitivity to electrooxi­dation, which is reflected in an increase of the anodic peak current. Of the five tested poly­phenols, i.e., gallic acid (GA), caffeic acid (CA), catechin (CT), quercetin (QV) and resveratrol (RE), the current maximum of the first two oxidation peaks increased only for GA by a factor of about 2 and for CT by a factor of about 1.5. Of the three red wines, Vranac (VR), Merlot (ME), Cabernet Sauvignon (CS); three white wines, Graševina (GR), Temjanika (TE), Char­donnay (CS) and one rose wine, Belrose Mediterranée Rosé (RO) tested, an increase by a factor of about 2.5 was observed for two red wines (VR, CS) and by a factor of 1.5 for one red wine (ME), one white wine (GR), and the rose wine (RO), while no increase in the current signal was observed for one of the white wines (CS). The most significant increase in the voltam­metric signal of GA at the MCPE/npTiO2 compared to other studied polyphenols can be explained by its higher affinity for adsorption on TiO2 nanoparticles. The investigated modified electrode provides an improved, linear and reproducible voltammetric response in wine samples. Consequently, MCPE/npTiO2 represents a good basis for the further deve­lopment of an integrated sensor/data system with the possibility of a broader application for the detection of polyphenols, especially GA, as an aroma and visually relevant parameter in winemaking.