Use of electrochemical color index as emerging analytical method for evaluating the quality of Tequila 100% agave

Abstract

Physicochemical and electrochemical characterization of Tequila 100% agave and its classes was carried out to obtain fundamental information that allows the design of specific electrodes useful as electrochemical sensors for evaluating the quality of alcoholic beverages. The physicochemical characterization consisted of gas and liquid chromatography, and atomic absorption spectroscopy studies. It was observed that the chromatographic parameters declared by the current Mexican official standards must be complemented with another analytical technique to differentiate between Tequila and problem samples. The above results relate satisfactorily to electrochemical studies. The differential pulse voltammograms of the Tequila 100% agave samples in their different classes showed three characteristic signals: i) −0.05 V vs. Ag/AgCl(sat) attributable to the reduction of Cu2+ to Cu0 present in the sample; ii) 0.34 V vs. Ag/AgCl(sat) related to the polyphenolic fraction that has antioxidant activity; therefore to the oxidation of organic compounds that contain the catechol group, and iii) 0.50 V vs. Ag/AgCl(sat) due to the oxidation of the flavonoid group which can be related to the maturation process of the beverage; with this results, electrochemical color index was determined for Tequila, problem samples and alcoholic beverages obtained from other agave species.