Oxidation Management of White Wines Using Cyclic Voltammetry and Multivariate Process Monitoring

Abstract

The development of a fingerprinting strategy capable to evaluate the "oxidation status" of white wines based on cyclic voltammetry is proposed here. It is known that the levels of specific antioxidants and redox mechanisms may be evaluated by cyclic voltammetry. This electrochemical technique was applied on two sets of samples. One group was composed of normal aged white wines and a second group obtained from a white wine forced aging protocol with different oxygen, SO(2), pH, and temperature regimens. A study of antioxidant additions, namely ascorbic acid, was also made in order to establish a statistical link between voltammogram fingerprints and chemical antioxidant substances. It was observed that the oxidation curve presented typical features, which enables sample discrimination according to age, oxygen consumption, and antioxidant additions. In fact, it was possible to place the results into four significant orthogonal directions, compressing 99.8% of nonrandom features. Attempts were made to make voltammogram fingerprinting a tool for monitoring oxidation management. For this purpose, a supervised multivariate control chart was developed using a control sample as reference. When white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity. Finally, quantification of substances implicated in the oxidation process as reagents (antioxidants) and products (off-flavors) was tried using a supervised algorithmic the partial least square regression analysis. Good correlations (r > 0.93) were observed for ascorbic acid, Folin-Ciocalteu index, total SO(2), methional, and phenylacetaldehyde. These results show that cyclic voltammetry fingerprinting can be used to monitor and diagnose the effects of wine oxidation.

Oxidation mechanisms occurring in wines

“…Recently, studies using cyclic voltammetric measurements enables the grouping of both quantitative and qualitative information concerning antioxidants (Kilmartin et al, 2001;Roginsky et al, 2006;Rodrigues, Silva Ferreira, Guedes de Pinho, Bento, & Geraldo, 2007;Martins et al, 2008;Makhotkina & Kilmartin, 2009). Wines originated from a forced aging degradation along with wines of different ages were monitored by cyclic voltammetry and the consumption rates of oxidizable species were estimated (Rodrigues et al, 2007 and ascorbic acid on the cyclic voltammograms of four representative wine polyphenols (catechin, caffeic acid, rutin and quercetin), in a model wine solution, along with five different wines was investigated using a glassy carbon electrode (Makhotkina & Kilmartin, 2009).…”

“…A similar trend was seen for glutathione, except in the case of quercetin, where the addition of glutathione led to the formation of a second set of voltammetric peaks, corresponding to the redox activity of a glutathione derivative (Makhotkina & Kilmartin, 2009). In addition, voltammogram fingerprinting was already used for monitoring oxidation management (Martins et al, 2008). In this study, a supervised multivariate control chart was developed using a control sample as reference, and when white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity (Martins et al, 2008).…”

“…In addition, voltammogram fingerprinting was already used for monitoring oxidation management (Martins et al, 2008). In this study, a supervised multivariate control chart was developed using a control sample as reference, and when white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity (Martins et al, 2008). A simple method based on a single-line FIA (Flow Injection Analysis) system with amperometric detection, at a potential of + 0.4 V (Ag/AgCl reference electrode) and wine pH, has been developed to evaluate the antioxidant capacity of red and white wines (Mannino, Brenna, Buratti, & Cosio, 1998).…”

Review of Oxidative Processes in Wine and Value of Reduction Potentials in Enology

“…The method has been modified to remove sulfite interference by adding a small amount of acetaldehyde (Makhotkina and Kilmartin 2010). Cyclic voltammetry has also been used to study wines of different origin and ages and to determine the effect of accelerated aging on adding O 2 and SO 2 as well as increasing pH (Rodrigues et al 2007, Martins et al 2008). …”

Reducing Antioxidant Capacity Evaluated by Means of Controlled Potential Electrolysis

“…Voltammetric methods constitute one of the most effective means to control and monitor electron-transfer reactions, although quantitative information is not straightly obtained from voltammograms of AOs mixtures. Recently it was demonstrated that cyclic voltammetry is adequate for establishing robust multivariate control charts for monitoring and diagnostic of the oxidation of white wines [44].…”