Stacy Deshaies
email: stacy.deshaies@umontpellier.fr

Luca Garcia
email: luca.garcia@umontpellier.fr

Frédéric Veran
email: frederic.veran@inrae.fr

Laetitia Mouls
email: laetitia.mouls@supagro.fr

Cédric Saucier
email: cedric.saucier@umontpellier.fr

François Garcia
email: francois.garcia@umontpellier.fr

Red Wine Oxidation Characterization by Accelerated Ageing Tests and Cyclic Voltammetry

Keywords: cyclic voltammetry, phenolic compounds, red wine, oxygen consumption rate, oxidation

In order to obtain information on the oxidative behavior of red wines, oxygen consumption rates and electrochemical changes (cyclic voltammetry) were measured for nine red wines subject to three different accelerated ageing tests: chemical (with hydrogen peroxide), enzymatic (with laccase from Trametes versicolor), and temperature (at 60 • C). Oxidative behavior depended both on the wine sample and accelerated ageing test type. A good correlation was observed between electrochemical parameters of charges for reference/non-oxidized wines, in accordance with their antioxidant capacity, and the variation of charges after enzymatic and temperature tests, meaning that cyclic voltammetry could be used in order to predict these two oxidation tests and reflect the wine sensitivity towards respective oxidation targets. However, it was not possible to predict wine chemical oxidation test based on hydrogen peroxide from the electrochemical measurements.

Introduction

During the winemaking process and storage, red wines can undergo many undesirable changes, particularly oxidative degradation due to numerous atmospheric oxygen intakes. This spoilage can deeply impact organoleptic properties [START_REF] Atanasova | Effect of oxygenation on polyphenol changes occurring in the course of wine-making[END_REF][START_REF] Kilmartin | The Oxidation of Red and White Wines and Its Impact on Wine Aroma[END_REF][START_REF] Ferreira | Key Changes in Wine Aroma Active Compounds during Bottle Storage of Spanish Red Wines under Different Oxygen Levels[END_REF][START_REF] Gambuti | Oxygen exposure of tannins-rich red wines during bottle aging. Influence on phenolics and color, astringency markers and sensory attributes[END_REF][START_REF] Ugliano | Oxygen Contribution to Wine Aroma Evolution during Bottle Aging[END_REF] and color stabilization [START_REF] Echave | Bottle Aging and Storage of Wines: A Review[END_REF] but its impact is strongly wine dependent [START_REF] Danilewicz | Reaction of Oxygen and Sulfite in Wine[END_REF][START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF][START_REF] Waterhouse | Sulfur Dioxide-Oxygen Consumption Ratio Reveals Differences in Bottled Wine Oxidation[END_REF].

Phenolic compounds constitute primary targets to oxidation reactions [START_REF] Oliveira | Oxidation mechanisms occurring in wines[END_REF][START_REF] Singleton | Oxygen with Phenols and Related Reactions in Musts, Wines, and Model Systems: Observations and Practical Implications[END_REF][START_REF] Waterhouse | Oxidation of Wine Phenolics: A Critical Evaluation and Hypotheses[END_REF], particularly those possessing an ortho-diphenol functional group which are going to be quickly converting into quinones; unstable and highly reactive compounds. Indeed, quinones are able to undergo nucleophilic addition, which is one of the main mechanisms responsible for oxidative degradation [START_REF] Ugliano | Oxygen Contribution to Wine Aroma Evolution during Bottle Aging[END_REF]. Numerous nucleophiles are available in wines, including SO 2 , phenolic compounds, amino acids, ascorbic acid, and volatile and non-volatile thiols [START_REF] Danilewicz | Reaction of Oxygen and Sulfite in Wine[END_REF][START_REF] Danilewicz | Review of Reaction Mechanisms of Oxygen and Proposed Intermediate Reduction Products in Wine: Central Role of Iron and Copper[END_REF][START_REF] Nikolantonaki | Reactivity of volatile thiols with polyphenols in a wine-model medium: Impact of oxygen, iron, and sulfur dioxide[END_REF][START_REF] Nikolantonaki | A Method to Quantify Quinone Reaction Rates with Wine Relevant Nucleophiles: A Key to the Understanding of Oxidative Loss of Varietal Thiols[END_REF][START_REF] Nikolantonaki | Measuring protection of aromatic wine thiols from oxidation by competitive reactions vs. wine preservatives with ortho-quinones[END_REF][START_REF] Oliveira | Quinones as Strecker degradation reagents in wine oxidation processes[END_REF].

Consequently, due to the manifold possible reactions and the complexity of the media, oxidation reactions effects are still difficult to predict. Thus, for example, Ferreira et al. [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF] recently highlighted the unusual behavior of certain red wines towards antioxidants as SO 2 and so the presence and competition of more reactive antioxidants.

Electrochemical methods, in particular linear sweep voltammetry and cyclic voltammetry (CV), using either carbon paste or glassy carbon electrodes, were developed and applied to the analysis of wine phenolic compounds [START_REF] Kilmartin | A Cyclic Voltammetry Method Suitable for Characterizing Antioxidant Properties of Wine and Wine Phenolics[END_REF][START_REF] Kilmartin | Correlation of Wine Phenolic Composition versus Cyclic Voltammetry Response[END_REF][START_REF] Makhotkina | Uncovering the influence of antioxidants on polyphenol oxidation in wines using an electrochemical method: Cyclic voltammetry[END_REF][START_REF] Ugliano | Rapid fingerprinting of white wine oxidizable fraction and classification of white wines using disposable screen printed sensors and derivative voltammetry[END_REF]. Recently, electrochemical techniques became widely used to determine antioxidant capacities of food or beverages as well as to analyze polyphenols [START_REF] Hoyos-Arbeláez | Electrochemical methods as a tool for determining the antioxidant capacity of food and beverages: A review[END_REF][START_REF] Piljac-Žegarac | Electrochemical determination of antioxidant capacity of fruit tea infusions[END_REF] as they appear as sensitive, fast, and easy to use techniques [START_REF] Lorrain | Evolution of Analysis of Polyhenols from Grapes, Wines, and Extracts[END_REF].

Cyclic voltammetry is among the most commonly used method to characterize total polyphenols content, antioxidant capacity, as well as to discriminate wine samples [START_REF] Geană | Wine varietal discrimination and classification using a voltammetric sensor array based on modified screen-printed electrodes in conjunction with chemometric analysis[END_REF][START_REF] Gonzalez | Untargeted voltammetric approaches for characterization of oxidation patterns in white wines[END_REF]. Voltammograms represent both anodic and cathodic curves. Concerning the anodic one, corresponding to the oxidation phenomenon, information can be drawn from the following parameters: (i) the peak current, proportional to the concentration of oxidizable compounds in solution; (ii) the peak potential, corresponding to the ease of oxidation of involved compounds (the more the potential is low and the more the compounds are easy to oxidize); (iii) the charge (corresponding to the area under the curve) which allows for the characterization of antioxidant capacity [START_REF] Hoyos-Arbeláez | Electrochemical methods as a tool for determining the antioxidant capacity of food and beverages: A review[END_REF].

Glassy carbon is used as a material for classical electrochemical electrodes but presently, carbon based disposable screen-printed electrodes appear as a promising tool and are become more widely used [START_REF] Dai | Glucose Biosensor Based on Multi-Walled Carbon Nanotube Modified Glassy Carbon Electrode[END_REF]. Indeed, they offer numerous advantages, including disposability [START_REF] Liu | A disposable amperometric sensor for rapid detection of serotonin in the blood and brain of the depressed mice based on Nafion membrane-coated colloidal gold screen-printed electrode[END_REF], reproducibility, practicality, high sensitivity, their ability to limit samples consumption thanks to miniaturization, and low detection limits [START_REF] Bordonaba | Electrochemical behaviour of polyphenol rich fruit juices using disposable screen-printed carbon electrodes: Towards a rapid sensor for antioxidant capacity and individual antioxidants[END_REF][START_REF] Pasakon | A high-performance, disposable screen-printed carbon electrode modified with multi-walled carbon nanotubes/graphene for ultratrace level electrochemical sensors[END_REF]. Among these, carbon nanotubes are used, allowing for the increase in, among others, sensitivity. Two categories of carbon nanotubes electrodes exist: multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) [START_REF] Dai | Glucose Biosensor Based on Multi-Walled Carbon Nanotube Modified Glassy Carbon Electrode[END_REF][START_REF] Chowdhry | Characterization of functionalized multiwalled carbon nanotubes and comparison of their cellular toxicity between HEK 293 cells and zebra fish in vivo[END_REF][START_REF] Gokceli | A Comparative Study of Single-and Multi-Walled Carbon Nanotube Incorporation to Indium Tin Oxide Electrodes for Solar Cells[END_REF]. SWCNTs were privileged in this work for their good results concerning wine polyphenols characterization and antioxidant capacity as shown by Newair et al. [START_REF] Newair | Square wave voltammetric analysis of polyphenol content and antioxidant capacity of red wines using glassy carbon and disposable carbon nanotubes modified screen-printed electrodes[END_REF]. The objectives of this article were first to determine the phenolic composition of nine different red wines (different varieties and vintage). Then, for each wine, their oxygen consumption rates (initial and average) and their voltammetry behavior with different accelerated ageing tests (H 2 O 2 , laccase and temperature) were analyzed. Finally, the possible correlations of electrochemical parameters with ageing tests results, and phenolic compounds were evaluated in order to use them as a quick method of characterization of red wine oxidation.

Materials and Methods

Chemicals and Reagents

Ethanol (absolute), tartaric acid (≥99.5%), laccase from Trametes versicolor (0.94 U•mg -1 ), Folin-Ciocalteu reagent, sodium hydroxide, chloride acid (1 M), (+)-catechin, (-)-epicatechin, quercetin and caffeic acid were purchased from Sigma-Aldrich (Saint-Quentin Fallavier, France). Oenin chloride was obtained from Extrasynthese (Genay, France).

Model Wine Solution

The model wine solution used as blank for electrochemical measurements was composed as follows: 12% vol. ethanol in water, 0.033 M tartaric acid and pH adjusted to 3.6 (sodium hydroxide 1 N).

Red Wines

Wines with different characteristics were selected for experiments. Commercial red wines were selected from various grape varieties from four vintages, 2019, 2018, 2014 and 2010, and origins: Côtes du Rhône (Syrah 2018, 2014 and 2010 from the same winery) corresponding to R1 to R3, Chinon (Cabernet Franc, 2018) corresponding to R4, Morgon (Gamay, 2018) corresponding to R5, Alsace rouge (Pinot noir, 2018) for R6, Ardèche (Syrah, 2019) for R7, Côteaux de Béziers (Syrah 2019) for R8 and Grès-de-Montpellier (Syrah, 2019) for R9.

A bottle of each wine was opened and slowly homogenized under nitrogen to avoid oxidation reactions. Aliquots of 50 mL tubes were then immediately frozen at -80 • C.

Wine Global Chemical Characterization

Wine Global Chemical Characterization

Studied wines were characterized with enological usual chemical analyses (Natoli laboratory, St Clément de Rivière, France) according to OIV procedures (www.oiv.int, accessed on 23 November 2021). Analyses included: alcoholic percentage (Fourier transformed infrared spectroscopy: FTIR); total acidity (FTIR); volatile acidity; total sulfur dioxide (automated colorimetric method); pH (FTIR); Fe (colorimetric method, reaction with disodium salt of (pyrildil-2)-3bis(phenyl-4-sulfonic 5-6 triazin-1,2,3,4) acid), absorbance read at 570 nm on a sequential analyzer (Olympus AU2700); Cu (colorimetric method 4-(3,5-Dibromo-2-Pyridilazo)-N-Ethyl-N-(3-Sulfopropyl) aniline reaction, absorbance read at 570 nm on a sequential analyzer (Olympus AU2700) (Supplementary Data Table S1).

Quantitative Analysis of Free SO 2 Levels (GC-MS)

Free SO 2 level (samples after oxygen saturation) was determinate by head-space gas chromatography coupled to a quadrupole mass spectrometer detector (HS-GC-MS) following the method described in Carrascon et al. [START_REF] Carrascón | The kinetics of oxygen and SO 2 consumption by red wines. What do they tell about oxidation mechanisms and about changes in wine composition?[END_REF] with slight modifications. GC-MS analysis was carried out on a GC Trace Ultra gas chromatograph (Thermo Fisher, Waltham, MA, USA) and coupled to an ISQ Series mass spectrometer (Thermo Fisher, Waltham, MA, USA). A DB-WAX (30 m × 0.25 mm i.d. × 0.25 µm) capillary column (Agilent Technologies, Santa Clara, CA, USA) was used for the chromatographic separation. For the analysis, 4.5 mL of sample was placed into a 10 mL headspace vial and 500 µL of ortho-phosphoric acid (85%) was added before closing and vials were incubated at 40 • C for 15 min. After this, 400 µL of the headspace was injected into a PTV injector, working in split mode (1:7 split ratio) and kept at 200 • C. An AOC-5000 autosampler (Shimadzu, Kyoto, Japan) with a static headspace unit was used and the 1mL gas-tight syringe was heated at 50 • C. After the injection, the hot syringe was cleaned by purging for 5 min with nitrogen. The temperature method started at 50 • C for 4 min then raised to 220 • C at 50 • C/min and was kept at this temperature for 5 min. The carrier gas employed was helium at 1.5 mL/min. The mass spectrometer was used with an electron impact (EI) ion source and acquisition was performed in single ion monitoring (SIM) mode. The m/z used for quantification were 48 and 64.

External calibration curves in model wine containing known amounts of SO 2 (as potassium metabisulfite) were prepared.

Accelerated Ageing Tests

Three accelerated oxidation tests were applied to the nine wines after oxygen saturation. Each wine sample was saturated with air by vigorously shaking a 500 mL flask containing 35 mL of wine for 10 s, after which the cap was opened (5 s) to let fresh air enter the flask. This saturation operation was repeated three times. The procedure and the test optimization have been previously described by Deshaies et al. [START_REF] Deshaies | Red Wine Oxidation: Accelerated Ageing Tests, Possible Reaction Mechanisms and Application to Syrah Red Wines[END_REF]:

Briefly, enzymatic test was performed by the addition of 50 µL of a 10 mg•L -1 laccase from Trametes versicolor solution in 11 mL of red wine.

For chemical test, 20 µL of hydrogen peroxide solution (30% in water) was added to 11 mL of red wine.

Finally, the heat treatment was performed by heating 11 mL of wine at 60 • C. For each test, red wine was put in Hermetic Pyrex 11 mL culture tubes (VWR 734-4224, Radnor, PA, USA) containing Pst3 oxygen sensors (Presens-Precision Sensing GmbH, Regensburg, Germany) with a minimum headspace.

Determination of Phenolic Composition

Determination of Total Phenolic Content (TPC)

The Folin-Ciocalteu method, revised by Magalhaes et al. [START_REF] Magalhães | Rapid microplate high-throughput methodology for assessment of Folin-Ciocalteu reducing capacity[END_REF], was used to determine total phenolic content. Absorbances were measured on a multiplate reader (Spectrostar Nano-BMG Labtech) equipped with spectrophotometric detection and 96-well plates. Each well contained: 50 µL diluted wine (1/100) + 50 µL Folin Ciocalteu reagent (1:5 v/v in water) + 100 µL sodium hydroxide solution (0.35 M). Absorbance at 750 nm of formed blue complex was read after 3 min.

The absorbance values for the wine samples were related to the calibration curve (gallic acid solution: 10 mg•L -1 to 200 mg•L -1 ). They reflected the total phenolic content in the considered wine. TPC was expressed in gallic acid equivalent (mg/L) and the result was multiplied by the associated dilution factor.

Total Tannins Content (TC)

The Bate-Smith method was used to determine total tannins content (TC) [START_REF] Ribéreau-Gayon | Le Dosage Des Tannins Du Vin Rouge et La Détermination de Leur Structure[END_REF]. To 4 mL 1/50 diluted wine (in water) in a tube was added 2 mL water and 6 mL HCl (12 N). The tube was then heated in a water bath at 100 • C for 30 min. The reference tube was identically treated without the heating step. A total of 1 mL ethanol (95%) was added to both tubes and absorbances at 550 nm were measured on spectrophotometer UV-1900 (Shimadzu, Marne-La-Vallée, France) against water under one cm of optical path. A 550 values were plotted on a standard curve drawn from reference oligomers.

Total Pigments Index (TP)

Wine samples were diluted in HCL 1 M (1/100) in a hermetic flask. After 30 min out of light, absorbance at 520 nm was read on spectrophotometer UV-1900 (Shimadzu, Marne-La-Vallée, France) against water under 1 mm of optical path. The result was multiplied by the associated dilution factor [START_REF] Atanasova | Effect of oxygenation on polyphenol changes occurring in the course of wine-making[END_REF][START_REF] Labarbe | Potentiel Polyphenolique de La Grappe de Vitis vinifera var[END_REF].

SO 2 Bleaching Resistant Pigments Index (RP)

To 10 mL wine in a hermetic flask, 150 µL of SO 2 solution was added (Na 2 S 2 O 5 in water at 200 g/L). After 30 min out of light, absorbance at 520 nm was read on spectrophotometer UV-1900 (Shimadzu, France) against water under 1 mm of optical path. The result was multiplied by the associated dilution factor [START_REF] Ducasse | Effect of macerating enzyme treatment on the polyphenol and polysaccharide composition of red wines[END_REF].

Electrochemical Apparatus and Measurements

Electrochemical measurements were performed with potentiostat/galvanostat (Autolab PGSTAT 302N) using software Nova 2.1.5 (Metrohm, Herisau, Switzerland). Model wine solution was used to dilute wine samples (1/75). Measurements were performed in the range of -0.2 V to 0.8 V (vs. Ag (s) ) with a scan rate of 100 mV/s using single-walled carbon nanotubes-modified screen-printed carbon electrode SWCNTs-SPCE (4 mm diameter, Dropsens, Oviedo, Spain) in a three-electrode configuration (silver solid reference electrode and carbon counter electrode). A total of 200 µL of sample were dropped at the electrode surface and measurements were immediately carried out. The experimental set-up is presented in Figure 1.

was multiplied by the associated dilution factor.

Total Tannins Content (TC)

The Bate-Smith method was used to determine total tannins content (TC) [START_REF] Ribéreau-Gayon | Le Dosage Des Tannins Du Vin Rouge et La Détermination de Leur Structure[END_REF]. T mL 1/50 diluted wine (in water) in a tube was added 2 mL water and 6mL HCl (12N). T tube was then heated in a water bath at 100 °C for 30 min. The reference tube was ide cally treated without the heating step. A total of 1mL ethanol (95%) was added to b tubes and absorbances at 550 nm were measured on spectrophotometer UV-1900 (S madzu, Marne-La-Vallée, France) against water under one cm of optical path. A550 val were plotted on a standard curve drawn from reference oligomers. 2.6.3. Total Pigments Index (TP) Wine samples were diluted in HCL 1M (1/100) in a hermetic flask. After 30 min of light, absorbance at 520 nm was read on spectrophotometer UV-1900 (Shimad Marne-La-Vallée, France) against water under 1 mm of optical path. The result was m tiplied by the associated dilution factor [START_REF] Atanasova | Effect of oxygenation on polyphenol changes occurring in the course of wine-making[END_REF][START_REF] Labarbe | Potentiel Polyphenolique de La Grappe de Vitis vinifera var[END_REF].

SO2 Bleaching Resistant Pigments Index (RP)

To 10 mL wine in a hermetic flask, 150 µL of SO2 solution was added (Na2S2O water at 200 g/L). After 30 min out of light, absorbance at 520 nm was read on spectrop tometer UV-1900 (Shimadzu, France) against water under 1 mm of optical path. The res was multiplied by the associated dilution factor [START_REF] Ducasse | Effect of macerating enzyme treatment on the polyphenol and polysaccharide composition of red wines[END_REF].

Electrochemical Apparatus and Measurements

Electrochemical measurements were performed with potentiostat/galvanostat (A tolab PGSTAT 302N) using software Nova 2.1.5 (Metrohm, Herisau, Switzerland). Mo wine solution was used to dilute wine samples (1/75). Measurements were performed the range of -0.2 V to 0.8 V (vs. Ag(s)) with a scan rate of 100 mV/s using single-wal carbon nanotubes-modified screen-printed carbon electrode SWCNTs-SPCE (4mm dia eter, Dropsens, Oviedo, Spain) in a three-electrode configuration (silver solid refere electrode and carbon counter electrode). A total of 200 µL of sample were dropped at electrode surface and measurements were immediately carried out. The experimental s up is presented in Figure 1.

Statistical Analysis

The ANOVA, correlation and PCA (principal component analysis) tests were performed using XLSTAT software (Addinsoft version 19.02, Paris, France). A Tukey test was carried out and where p-values were <0.05 was considered as significant. Pearson's correlation coefficient was carried out for the determination of correlations between electrochemical parameters, oxygen consumption rates and phenolic composition. All analyses, experiments and tests were performed in triplicate.

Results and Discussion

Wines Phenolic Characterization

According to Table 1, phenolic and tannin contents were mostly in accordance, with significant highest contents for R8 wine concerning phenolic content (3.1 g GAE•L -1 ), and R8 (4.6 g•L -1 ), R3 (4.4 g•L -1 ) and R4 (4.2 g•L -1 ) concerning total tannins content, whereas lowest contents were observed for R7 (1.4 g•L -1 and 2.1 g•L -1 respectively). These values were also in accordance with pigment index ones, with total pigment index values ranging from 4.8 for R6 to 21.2 for R9 and also the SO 2 bleaching resistant pigments index from 1.7 to 7.2 for the same wines. Finally, it can be concluded that, although some wines were from the same cultivar, the nine wines presented very different initial phenolic composition.

Accelerated Ageing Tests: Oxygen Consumption Parameters

The red wines were submitted to three accelerated ageing tests experiments [START_REF] Magalhães | Rapid microplate high-throughput methodology for assessment of Folin-Ciocalteu reducing capacity[END_REF]: chemical (H 2 O 2 added), enzymatic (by laccase from Trametes versicolor) and heat treatment (at 60 • C). The oxygen consumption was monitored non-destructively by means of fluorescence oxygen sensors. The wine samples submitted to ageing test oxidations consumed an oxygen concentration of approximately 6.5 mg•L -1 whereas, in the case of non-oxidized controls, average total consumed oxygen was only 0.20 ± 0.15 mg•L -1 .

Table 2 data confirm that wines can differ for their kinetics to consume oxygen, in agreement with recent studies [START_REF] Danilewicz | Reaction of Oxygen and Sulfite in Wine[END_REF][START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF]. Oxidation mechanisms in wine start with oxygen activation by metal catalysis (Fe or Cu), inducing radicals named reactive oxygen species (ROS). Quinones are then formed as well as hydrogen peroxide, both capable of reacting with several other wine compounds [START_REF] Ugliano | Oxygen Contribution to Wine Aroma Evolution during Bottle Aging[END_REF][START_REF] Singleton | Oxygen with Phenols and Related Reactions in Musts, Wines, and Model Systems: Observations and Practical Implications[END_REF][START_REF] Oliveira | Quinones as Strecker degradation reagents in wine oxidation processes[END_REF]. Consequently, a decrease in the dissolved oxygen concentration is systematically observed and the measure of this reflects the evolution of wine oxidative kinetics [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF][START_REF] Singleton | Oxygen with Phenols and Related Reactions in Musts, Wines, and Model Systems: Observations and Practical Implications[END_REF].

Experiments were carried out in hermetic culture tubes with minimum headspace. It was previously shown that this procedure allowed a headspace volume between 0 µL and 120 µL [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF], and so oxygen ingress through the cap was negligible and only evolution of dissolved oxygen in wine was considered during the time of the experiment. Oxygen consumption parameters are summarized in Table 2. Important differences were observed between wines both for initial and average O 2 rates. Values ranged from 0.17 ppm•h -1 (R8 lac) to 4 ppm•h -1 (R8 H 2 O 2 ) for average O 2 rates and from 0.38 ppm•h -1 (R8 lac) to 9.32 ppm•h -1 (R8 H 2 O 2 ) for initial O 2 rates. The wines can have completely opposite behaviors towards the oxidation process. R9 and R7 wines showed similar rates around 1 ppm•h -1 whatever the oxidation protocol, whereas R8 and R4 wines also had low consumption rates less or around 1 ppm•h -1 for temperature and enzymatic tests but were among the highest rates for chemical oxidation (9.32 and 5.33 ppm•h -1 respectively). Globally, chemical oxidation using H 2 O 2 showed the equal highest oxygen consumption rates for all considered samples except for R1 and R3, for which enzymatic oxidation (using laccase) showed the highest consumption rates.

Several factors can influence the oxygen consumption rates of wine as pH, ascorbic acid concentration or metals concentration [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF][START_REF] Danilewicz | Review of Reaction Mechanisms of Oxygen and Proposed Intermediate Reduction Products in Wine: Central Role of Iron and Copper[END_REF] pH, and also copper and iron concentrations, are shown in the supplementary data, all play a part in oxygen consumption during experiments. For example, R8, which had the highest metals concentrations, very quickly consumed oxygen when it was oxidized adding H 2 O 2 compared to other samples (Table 2). On the contrary, R6 had the lowest metal concentrations and was globally oxidized slower than other samples whatever the considered oxidation protocol. However, it is difficult to conclude on a clear relation between OCRs and the above variables, metals concentrations not completely reflecting the fraction involved in oxidation reactions [START_REF] Danilewicz | Review of Reaction Mechanisms of Oxygen and Proposed Intermediate Reduction Products in Wine: Central Role of Iron and Copper[END_REF][START_REF] Gonzalez | Untargeted voltammetric approaches for characterization of oxidation patterns in white wines[END_REF][START_REF] Clark | Measurement of labile copper in wine by medium exchange stripping potentiometry utilising screen printed carbon electrodes[END_REF][START_REF] Kontoudakis | The impact of wine components on fractionation of Cu and Fe in model wine systems: Macromolecules, phenolic and sulfur compounds[END_REF].

As an antioxidant, SO 2 can affect oxygen consumption kinetics during accelerated ageing tests. Free SO 2 values are available in the supplementary data (Tables S1 andS2) and were measured after oxygen saturation (before oxidation) and after the different controlled oxidations. Chemical and temperature tests completely consumed available free SO 2 (if available after saturation) whatever the initial concentration, this latter having consequently a limited impact on OCRs. This decay in SO 2 was primarily due to its reaction with the quinones and H 2 O 2 deriving from oxidation of phenolics [START_REF] Danilewicz | Mechanism of Interaction of Polyphenols, Oxygen, and Sulfur Dioxide in Model Wine and Wine[END_REF]. Concerning enzymatic oxidation, all the available SO 2 was not systematically consumed. However, R3 and R7 samples were statistically the ones with highest OCR lac (initial and average) but these two samples presented no available free SO 2 before enzymatic oxidation. Consequently, it can be hypothesized that free SO 2 content had no impact on enzymatic oxidation.

Several factors can be responsible for SO 2 consumption as ascorbic acid concentration [START_REF] Bradshaw | Ascorbic Acid: A Review of its Chemistry and Reactivity in Relation to a Wine Environment[END_REF] or sulfonation reactions [START_REF] Arapitsas | Wine metabolomics reveals new sulfonated products in bottled white wines, promoted by small amounts of oxygen[END_REF]. Even if a theoretical molar reaction ratio of 2:1 (SO 2 /O 2 ) should be expected [START_REF] Danilewicz | Reaction of Oxygen and Sulfite in Wine[END_REF], it is generally not observed. Recent studies showed that such a molar ratio can hardly be applied to a complex media such as wine [START_REF] Waterhouse | Sulfur Dioxide-Oxygen Consumption Ratio Reveals Differences in Bottled Wine Oxidation[END_REF][START_REF] Carrascón | Oxygen and SO 2 Consumption Rates in White and Rosé Wines: Relationship with and Effects on Wine Chemical Composition[END_REF]. Indeed, SO 2 does not directly react with oxygen and other chemical species are involved and other strong reductants can compete with it, as recently observed by Ferreira et al. [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF]. For certain wines, oxygen consumption might be really fast but not result in immediate SO 2 loss, other highly reactive reductants can consume O 2 with no involvement of SO 2 . 3. Only one anodic peak was present for caffeic acid at a potential of 166 mV, whereas for catechin and gallic acid two peaks were present with a potential of 151 mV for the first one (Ep,a 1 ). This is attributed to the oxidation of hydroxyl groups (on B-ring for catechin) into corresponding ortho-quinones [START_REF] Kilmartin | Correlation of Wine Phenolic Composition versus Cyclic Voltammetry Response[END_REF][START_REF] Souza | Voltammetric Determination of the Antioxidant Capacity in Wine Samples Using a Carbon Nanotube Modified Electrode[END_REF][START_REF] Petrovic | Correlation of Perceived Wine Astringency to Cyclic Voltammetric Response[END_REF]. The formed ortho-quinones can be reduced on the reverse scan generating a well-defined cathodic peak as, for example, for caffeic acid (Figure 2b). The second anodic peak observed only for catechin and gallic acid (Ep,a 2 = 476 mV) corresponded to the oxidation of catechin A-ring hydroxyl group [START_REF] Rebelo | Comparative study of the antioxidant capacity and polyphenol content of Douro wines by chemical and electrochemical methods[END_REF] and to the oxidation of the third phenol group adjacent to the ortho-diphenol group in gallic acid [START_REF] Novak | Square-wave and cyclic voltammetry of epicatechin gallate on glassy carbon electrode[END_REF]. For quercetin, only one peak at low potential (166 mV) was present and the second peak was not clearly observable. At last, concerning anthocyanins, electrochemical behavior of oenin chloride in model wine was also investigated showing only one peak at 398 mV. Oenin chloride revealed that anthocyanins tend to be less easily oxidizable compounds than other phenolic compounds. The classification obtained considering only the first peak potential for the studied standards at equal concentration (0.1 mM) by increasing potential was as follows: quercetin 151 mV/catechin 151 mV < gallic acid 154 mV < caffeic acid 166 mV < oenin chloride 398 mV and revealed the ability of the compounds to oxidize at different potentials. These potentials depend on a molecule structure's chemical reactivity. This ranking appears to be logical when considering substituents to catechol groups. An electro donating group reduces potential values while electro accepting groups (as carboxyl) tend to increase potential values. Moreover, it is noteworthy that the galloyl substitution of gallic acid is more oxidizable than the catechol group of caffeic acid [START_REF] Newair | Square wave voltammetric analysis of polyphenol content and antioxidant capacity of red wines using glassy carbon and disposable carbon nanotubes modified screen-printed electrodes[END_REF].

Electrochemical Behavior of

Electrochemical Behavior of Wines Non-Oxidized and Oxidized with Different Oxidation Protocols

Electrochemical methods, and in particular cyclic voltammetry (CV), involve mechanisms similar to those occurring in wines [START_REF] Makhotkina | Uncovering the influence of antioxidants on polyphenol oxidation in wines using an electrochemical method: Cyclic voltammetry[END_REF]. CV is consequently of major interest in order to study wine oxidation. It has already been applied to the study of white wine oxidation [START_REF] Gonzalez | Untargeted voltammetric approaches for characterization of oxidation patterns in white wines[END_REF][START_REF] Martins | Oxidation Management of White Wines Using Cyclic Voltammetry and Multivariate Process Monitoring[END_REF][START_REF] Rodrigues | Resistance to Oxidation of White Wines Assessed by Voltammetric Means[END_REF] and recently, carbon-based screen printed sensors turned out to be a rapid and reproducible device for the analysis of polyphenols [START_REF] Benbouguerra | Voltammetric Behavior, Flavanol and Anthocyanin Contents, and Antioxidant Capacity of Grape Skins and Seeds during Ripening (Vitis vinifera var. Merlot, Tannat, and Syrah)[END_REF] and wine components. They give access to voltammograms resulting from the current responses from a large number of polyphenols.

Values in Table 4 showed the high variability in anodic current measurements through the resulting calculated charges, depending on each wine. Wine samples were increasingly diluted (in model wine solution) from 1/100 to 1/10 and acquisitions were performed on 1/75 diluted samples. This dilution allowed for the linear part of the total charge response as a function of wine concentration. Moreover, experiments were performed on wines diluted 75 times in order to discard free SO 2 influence in anodic reactions (oxidation) [START_REF] Vilas-Boas | Evaluation of total polyphenol content of wines by means of voltammetric techniques: Cyclic voltammetry vs. differential pulse voltammetry[END_REF]. Indeed, with higher SO 2 contents, semi quinone radicals formed during electrochemical oxidation can react, leading to quinone reduction back to the original polyphenol [START_REF] Makhotkina | The phenolic composition of Sauvignon blanc juice profiled by cyclic voltammetry[END_REF]. Further reactions could also take place as the formation of sulfonic acid derivatives, disrupting CV results by increasing anodic peak intensity and also decreasing the cathodic peak intensity [START_REF] Makhotkina | The phenolic composition of Sauvignon blanc juice profiled by cyclic voltammetry[END_REF].

Voltammetric experiments were carried out for all reference wines as well as all oxidation protocols. Cyclic voltammograms showed for each sample three peaks at approximately the same potentials: around 220, 480 and 700 mV. Reverse cathodic peak was also observed. An example of obtained cyclic voltammograms for the reference R2 wine and the three accelerated protocols (blank subtracted) is presented in Figure 3. 4. Charges (Q) for reference (non-oxidized) wines (blanck substracted) and difference of charges (∆Q) between reference wines and oxidized wines with three different accelerated protocols (60 • C, laccase and H 2 O 2 ). Q and ∆Q are expressed in µC. Different letters indicate the significant differences between samples in one column according to Tukey's test, p < 0.05. sities on cyclic voltammograms. In addition to that, oxidized wine intensitie mograms were almost equal or inferior to the reference ones corresponding, oxidation protocol impact on the oxidizable compound content in the samp ple, concerning the R2 wine in Figure 3 representing cyclic voltammograms wine and three accelerated protocols, enzymatic and chemical oxidation p peared to have a moderate impact on the wine compared to temperature ox the latter having the most important one.

A Q 240mV Q 520mV Q 520mV -Q 240mV Q 240mV /Q 800mV Q 800mV R1 7.

Charges of Non-Oxidized Red Wines and Charge Variation after Accel ing Tests

The different charges extracted from voltammograms and correspondin under the anodic curve until the given potential value shown in Table 4 allo trate the polyphenol's capacity to be oxidized at the working electrode [5 charge Q800mV corresponds to all oxidizable phenolic compounds that will con total antioxidant capacity of the wine sample. Q240mV represents the electroche The first oxidation peak can be assigned to the most oxidizable compounds as catechintype flavonoids [START_REF] Benbouguerra | Voltammetric Behavior, Flavanol and Anthocyanin Contents, and Antioxidant Capacity of Grape Skins and Seeds during Ripening (Vitis vinifera var. Merlot, Tannat, and Syrah)[END_REF], including oligomers and polymers, caffeic acid and derivatives, flavonols containing a catechol or a galloyl group (Table 3). As described by Newair et al. [START_REF] Newair | Square wave voltammetric analysis of polyphenol content and antioxidant capacity of red wines using glassy carbon and disposable carbon nanotubes modified screen-printed electrodes[END_REF], red wines contain high concentrations of flavan-3-ols, caffeic acid and gallic acid, all responsible for the first anodic peak intensity.

The second peak on the voltammograms at around 520 mV could correspond to overlaps [START_REF] Vilas-Boas | Evaluation of total polyphenol content of wines by means of voltammetric techniques: Cyclic voltammetry vs. differential pulse voltammetry[END_REF] mainly resulting from the malvidin anthocyanins oxidation as well as to the second oxidation of catechin type flavanols and galloyl containing compounds (Table 3). Ferulic acid and trans resveratrol or similar polyphenols could also interact [START_REF] Kilmartin | A Cyclic Voltammetry Method Suitable for Characterizing Antioxidant Properties of Wine and Wine Phenolics[END_REF].

Concerning the third peak, its presence was less marked on the voltammograms and can corresponds to the oxidation of phenolic compounds with high oxidation potentials, such as para-coumaric or vanillic acids [START_REF] Kilmartin | Correlation of Wine Phenolic Composition versus Cyclic Voltammetry Response[END_REF][START_REF] Singleton | Caftaric Acid Disappearance and Conversion to Products of En-zymic Oxidation in Grape Must and Wine[END_REF][START_REF] Lopes | A: A Quinone Methide Derivative Resulting from Malvidin 3-O-Glucoside Degradation[END_REF]. The presence of a cathodic peak on the reverse scan on the voltammograms is noteworthy.

As mentioned previously, differences between wines were mainly notables on intensities on cyclic voltammograms. In addition to that, oxidized wine intensities on voltammograms were almost equal or inferior to the reference ones corresponding, reflecting the oxidation protocol impact on the oxidizable compound content in the sample. For example, concerning the R2 wine in Figure 3 representing cyclic voltammograms for reference wine and three accelerated protocols, enzymatic and chemical oxidation protocols appeared to have a moderate impact on the wine compared to temperature oxidation, with the latter having the most important one.

Charges of Non-Oxidized Red Wines and Charge Variation after Accelerated Ageing Tests

The different charges extracted from voltammograms and corresponding to the area under the anodic curve until the given potential value shown in Table 4 allow us to illustrate the polyphenol's capacity to be oxidized at the working electrode [START_REF] Benbouguerra | Voltammetric Behavior, Flavanol and Anthocyanin Contents, and Antioxidant Capacity of Grape Skins and Seeds during Ripening (Vitis vinifera var. Merlot, Tannat, and Syrah)[END_REF]. The total charge Q 800mV corresponds to all oxidizable phenolic compounds that will contribute to the total antioxidant capacity of the wine sample. Q 240mV represents the electrochemical charge of the most easily oxidizable polyphenols (generally hydroxyl group oxidation into quinones for flavan-3-ols, phenol acids and flavonols) that have consequently the highest antioxidant capacity. Q 520mV estimates the charge of the compounds which oxidize until 520 mV (the major part). In addition to that, the difference (Q 520mV -Q 240mV ) gives the charge of the compounds that correspond to the second oxidation peak on the voltammograms, whereas the ratio Q 240mV /Q 800mV illustrates the contribution of the most antioxidant compounds to the total antioxidant capacity of the wine.

For the reference wines (Table 4A), the charges (Q) values were extracted from voltammograms with blank subtracted (model wine solution), whereas for the oxidized wine samples (Table 4B-D), the difference of charges (∆Q) values were extracted from voltammograms corresponding to oxidized wines with reference wine subtracted in order to obtain values representing only oxidized compounds.

For non-oxidized wines the obtained charges values (Q 240mV , Q 520mV and Q 800mV ) were very different (Table 4A). The lowest values for the charges were observed for R7 wine and these weak values were in accordance with its phenolic and total tannins contents which were also the lowest ones (Table 1). On the opposite end, the highest values were observed for R8 wine which presents a significantly high content of polyphenols and tannins, compared to other wines.

Values in Table 4B-D were those of reference wines minus oxidized wines (∆Q) in order to take into consideration only oxidation effect. As described by previous researchers [START_REF] Kilmartin | A Cyclic Voltammetry Method Suitable for Characterizing Antioxidant Properties of Wine and Wine Phenolics[END_REF][START_REF] Kilmartin | Correlation of Wine Phenolic Composition versus Cyclic Voltammetry Response[END_REF][START_REF] Makhotkina | Uncovering the influence of antioxidants on polyphenol oxidation in wines using an electrochemical method: Cyclic voltammetry[END_REF], the majority of compounds involved in wine oxidation reactions (phenolic compounds, ascorbic acid) are able to oxidize at the surface of an electrode and therefore can be analyzed using voltammetric methods. A comparison of oxidized wines with their corresponding non-oxidized ones (subtractive approach) can provide additional information on global wine oxidation. Indeed, due to the numerous simultaneous voltammetric signals occurring during wine analysis, this method is unable to provide specific information on individual wine components.

Interestingly, charge differences (∆Q) of subtractive voltammograms were also strongly wine-dependent, which provides interesting information on chemical reactions involving the major wine oxidizable compounds during oxygen consumption. Some wines showed important current decrease at 240 mV and consequently high values of difference of charge. It was the case for R8 wine oxidized with laccases or at 60 • C or R6 wine for all oxidation types. It revealed that they contained oxidizable species which were easily degraded upon oxygen consumption. On the other hand, other wines showed opposite behavior, as for R7 wine oxidized with H 2 O 2 or at 60 • C. Moreover, the different values of ∆(Q 520mV -Q 240mV ) indicated that oxidation also induced changes in less easily oxidizable compounds.

All these measurements were also very different depending on the considered oxidation protocol, as for R2 wine values, which were among the highest ones with temperature oxidation and among the lowest ones with laccase or H 2 O 2 oxidation protocols, whereas R1 wine showed opposite trends for the same protocols. These results are in accordance with the influence of wine composition on its oxidation ability.

It is noteworthy that even older wines (R2 and R3 were respectively from 2014 and 2010) contain oxidizable compounds and can undergo further oxidations. Hydrogen peroxide had an impact on them whereas R7 and R8 wines were very little impacted. On the contrary, enzymatic oxidation had a negligible impact on them. Temperature oxidation impacts R2 and R3 wines whereas it was not true for R1 wine (2018 Syrah wine). Even if oxidation phenomena are strongly wine dependent, these results can suggest that oxidation reactions lead to the formation of different products which are able to further oxidize themselves.

Correlation between Phenolic Composition, Oxygen Consumption Rates and Electrochemical Parameters

Table 5 represents the Pearson correlation matrix between electrochemical parameters for non-oxidized wines and for all accelerated ageing tests (H 2 O 2 , laccase and at 60 • C), OCRs (initial and average oxygen consumption rate) and wine composition (tannins, polyphenols, total pigments, and SO 2 bleaching resistant pigments). Concerning the phenolic composition, the charges Q 240mV ref and Q 520mV ref were well correlated with TPC (itself well correlated with TC (R = 0.91)) with R = 0.86 and 0.80 respectively. A better correlation between TPC and the total charge Q 800mV ref could have been expected since the Folin-Ciocalteu test (TPC) is a global method for which all hydroxyl groups that are able to react with the F-C reagent are implied [START_REF] Carrascón | The kinetics of oxygen and SO 2 consumption by red wines. What do they tell about oxidation mechanisms and about changes in wine composition?[END_REF]. These three charges were also well correlated with the values of their corresponding difference of charge at the same potential for enzymatic and temperature oxidation tests, while no correlation was observed with chemical oxidation using hydrogen peroxide. The fact that the calculated charges of non-oxidized (reference) wines, in accordance with its oxidability, presented high correlations with the difference of the charges for enzymatic as well as temperature oxidized wines (reference subtracted) emphasizes that cyclic voltammetry can partly predict these two oxidation tests and reflects the wine sensitivity towards respective oxidation targets. However, it is not possible to predict the wine chemical oxidation test using hydrogen peroxide. These last results are in accordance with the good negative correlations between the oxygen consumption rates and the charges of the reference wines: between aOCR lac and Q 240mV ref (R = -0.82) or Q 800mV ref (R = -0.84), and between iOCR 60 • C and Q 240mV ref , Q 520mV ref and Q 800mV ref (R = -0.84; -0.82 and -0.88 respectively).

Considering the parameters related to oxygen consumption kinetics, for a same oxidation test, iOCR was highly correlated with aOCR: R(iOCR 60 • C /aOCR 60 • C ) = 0.89; R(iOCR lac /aOCR lac ) = 0.95 and R(iOCR H2O2 /aOCR H2O2 ) = 0.90. These results are in accordance with previous studies studying OCR of oxygen saturated white wines [START_REF] Gonzalez | Untargeted voltammetric approaches for characterization of oxidation patterns in white wines[END_REF]. It is worth mentioning that OCRs for enzymatic by laccase and temperature at 60 • C oxidations were partly correlated to each other (iOCR 60 • C correlated with aOCR lac and iOCR lac with respectively R = 0.85 and 0.80).

Concerning the relation between OCRs and the differences of charges (∆Q) for oxidized wines, strong negative correlations were observed for the temperature oxidation between the oxygen consumption rates and the charge at low potential ∆Q 240mV 60 • C as well as the total charge ∆Q 800mV 60 • C and more particularly for iOCR 60 • C . For the laccase oxidation test, less robust correlations were obtained.

Kinetic parameters for the H 2 O 2 ageing test (iOCR H2O2 or aOCR H2O2 ) were not correlated with the electrochemical parameters of reference wines but showed a high negative correlation with ∆Q 520mV H2O2 with R = -0.88 and -0.84, respectively (R = -0.84 between aOCR H2O2 and ∆Q 520mV H2O2 ).

Principal Component Analysis

Principal component analysis (PCA) was used in this work in order to classify wines. Factor analysis was calculated with the same parameters as the ones used for Pearson's correlation in Table 5. Figure 4 shows the plots of loadings and scores in the space described by the 1st and 2nd factors.

The first factor explains 51.19% of the total data variability and it is mainly related to the richness in polyphenols and tannins (TPC and TC) and to the electrochemical parameters for non-oxidized wines, enzymatic and temperature oxidations, and their respective OCRs. It allows us to distinguish red wine samples depending on their oxidation rates with laccases or at 60 • C. Indeed, the first factor is positively correlated with electrochemical parameters, TPC and TC, while it is negatively correlated with OCRs. R1, R3, as well as R7, are red wines being the fastest oxidized by laccases and by temperature. R1 and R7 wines are among the lowest in TPC and TC values.

Principal Component Analysis

Principal component analysis (PCA) was used in this work in order to classify wine Factor analysis was calculated with the same parameters as the ones used for Pearson correlation in Table 5. Figure 4 shows the plots of loadings and scores in the space d scribed by the 1st and 2nd factors. The second factor explains 18.68% of the total data variability. It is positively correlated with electrochemical parameters concerning chemical oxidation with H 2 O 2 and negatively correlated with corresponding OCRs and with anthocyanins content (TP and RP). R8 is the red wine with the highest TPC and TC and the fastest oxidized by hydrogen peroxide, and the slowest oxidized by the two other tests.

Wines can consequently be discriminated in Figure 4 into three groups depending on their variable responses. The three Syrah wines (R1, R2 and R3) from the same winery but with different vintages are gathered together on the left of the PCA while both 2019 aged Syrah wines (R7 and R8) are at the bottom of Figure 4. All other wines from different grape cultivars are gathered in a third group, also containing the last 2019 aged Syrah wine (R9), a hypothesis being that it is the only Syrah wine in the study which was aged in barrels.

Figure 5 is a PCA of the reference wines according to their electrochemical parameters (except Q 240mV /Q 800mV ratio). It shows the plots of loadings and scores in the space described by the 1st and 2nd factors. The first factor explains 92.47% of the total data variability while the second one explains 5.23%. Three groups can be seen on Figure 5 depending on wine OCRs (initial or average). Indeed, the first group contains R1, R3 and R7 wines, and corresponds to the wines which consume oxygen the most quickly when oxidized with temperature or laccases, while R8 wine shows really low OCRs with these two oxidation processes. All other wines (R2, R4, R5, R6 and R9) have intermediate values compared the two previous groups. Consequently, electrochemical measurements on nonoxidized (reference) wines allow us to classify wines depending on their OCRs (for laccase and temperature). It is then possible to predict a wine's sensibility towards oxidation (laccase and temperature) thanks to electrochemical measurements of the reference wines. This method is very promising as it is quick and necessitates a sample diluted drop.

peroxide, and the slowest oxidized by the two other tests.

Wines can consequently be discriminated in Figure 4 into three groups depending on their variable responses. The three Syrah wines (R1, R2 and R3) from the same winery but with different vintages are gathered together on the left of the PCA while both 2019 aged Syrah wines (R7 and R8) are at the bottom of Figure 4. All other wines from different grape cultivars are gathered in a third group, also containing the last 2019 aged Syrah wine (R9), a hypothesis being that it is the only Syrah wine in the study which was aged in barrels.

Figure 5 is a PCA of the reference wines according to their electrochemical parameters (except Q240mV/Q800mV ratio). It shows the plots of loadings and scores in the space described by the 1st and 2nd factors. The first factor explains 92.47% of the total data variability while the second one explains 5.23%. Three groups can be seen on Figure 5 depending on wine OCRs (initial or average). Indeed, the first group contains R1, R3 and R7 wines, and corresponds to the wines which consume oxygen the most quickly when oxidized with temperature or laccases, while R8 wine shows really low OCRs with these two oxidation processes. All other wines (R2, R4, R5, R6 and R9) have intermediate values compared the two previous groups. Consequently, electrochemical measurements on non-oxidized (reference) wines allow us to classify wines depending on their OCRs (for laccase and temperature). It is then possible to predict a wine's sensibility towards oxidation (laccase and temperature) thanks to electrochemical measurements of the reference wines. This method is very promising as it is quick and necessitates a sample diluted drop. Another PCA representation gathering all the electrochemical parameters (before and after oxidation) also reveals a discrimination into three main groups (Supplementary data Figure S1) and confirms previous results. Representation of the loadings (variables-electrochemical parameters (except Q 240mV /Q 800mV ratio) for the reference wines) and the scores (wines) in the plane defined by respectively the first (F1) and second (F2) factor (explained variance: 97.74%).

Figure 1 .

 1 Figure 1. Cyclic voltammetry experimental set-up.

Figure 1 .

 1 Figure 1. Cyclic voltammetry experimental set-up.

  Figure 2 represents the cyclic voltammograms of representative wine polyphenols (flavanol, hydroxycinnamic acid, benzoic acid, anthocyanin and flavonol) in model wine solutions using single-walled carbon nanotube (SWCNT) electrodes. The corresponding anodic (oxidation) peak potentials are given in Table3. Only one anodic peak was present for caffeic acid at a potential of 166 mV, whereas for catechin and gallic acid two peaks were present with a potential of 151 mV for the first one (Ep,a 1 ). This is attributed to the oxidation of hydroxyl groups (on B-ring for catechin) into corresponding ortho-quinones[START_REF] Kilmartin | Correlation of Wine Phenolic Composition versus Cyclic Voltammetry Response[END_REF][START_REF] Souza | Voltammetric Determination of the Antioxidant Capacity in Wine Samples Using a Carbon Nanotube Modified Electrode[END_REF][START_REF] Petrovic | Correlation of Perceived Wine Astringency to Cyclic Voltammetric Response[END_REF]. The formed ortho-quinones can be reduced on the reverse scan generating a well-defined cathodic peak as, for example, for caffeic acid (Figure2b). The second anodic peak observed only for catechin and gallic acid (Ep,a 2 = 476 mV) corresponded to the oxidation of catechin A-ring hydroxyl group[START_REF] Rebelo | Comparative study of the antioxidant capacity and polyphenol content of Douro wines by chemical and electrochemical methods[END_REF] and to the oxidation of the third phenol group adjacent to the ortho-diphenol group in gallic acid[START_REF] Novak | Square-wave and cyclic voltammetry of epicatechin gallate on glassy carbon electrode[END_REF]. For quercetin, only one peak at low potential (166 mV) was present and the second peak was not clearly observable. At last, concerning anthocyanins, electrochemical behavior of oenin chloride in model wine was also investigated showing only one peak at 398 mV. Oenin chloride revealed that anthocyanins tend to be less easily oxidizable compounds than other phenolic compounds.

Antioxidants 2021 , 19 Figure 2 .Table 3 .

 20211923 Figure 2. Cyclic voltammograms of different standard polyphenols at SWCNT-SCPE: catechin (A); caffeic acid (B); gallic acid (C); oenin chloride (D) and quercetin (E) at a concentration of 0.1 mM (blank subtracted); SWCNT-SPCE: single walled carbon nanotubes modified screen printed carbon electrodes. Table 3. Voltammetric peak potentials of the standard polyphenols (concentration of 0.1 mM) in model wine solution (pH 3.6) using SWCNT-SPCE. Ep,a1 represents the potential of the first anodic peak and Ep,a2 represents the potential of the second anodic peak.

Figure 2 .

 2 Figure 2. Cyclic voltammograms of different standard polyphenols at SWCNT-SCPE: catechin (A); caffeic acid (B); gallic acid (C); oenin chloride (D) and quercetin (E) at a concentration of 0.1 mM (blank subtracted); SWCNT-SPCE: single walled carbon nanotubes modified screen printed carbon electrodes.

Table

Figure 3 .

 3 Figure 3. Cyclic voltammograms of R2 wine non-oxidized (ref) and oxidized with three different protocols: tem (60 °C), chemical (H2O2) and enzymatic (laccase) with SWCNT.

Figure 3 .

 3 Figure 3. Cyclic voltammograms of R2 wine non-oxidized (ref) and oxidized with three different protocols: temperature (60 • C), chemical (H 2 O 2 ) and enzymatic (laccase) with SWCNT.

Figure 4 .

 4 Figure 4. Representation of the loadings (variables) and the scores (wines) in the plane defined by respectively the first (F1) and second (F2) factor (explained variance: 69.87%).

Antioxidants 2021 , 19 Figure 5 .

 2021195 Figure 5. Representation of the loadings (variables-electrochemical parameters (except Q240mV/Q800mV ratio) for the reference wines) and the scores (wines) in the plane defined by respectively the first (F1) and second (F2) factor (explained variance: 97.74%).

Figure 5 .

 5 Figure 5.Representation of the loadings (variables-electrochemical parameters (except Q 240mV /Q 800mV ratio) for the reference wines) and the scores (wines) in the plane defined by respectively the first (F1) and second (F2) factor (explained variance: 97.74%).

Table 1 .

 1 Phenolic characterization of the different red wines. Values represent means of triplicate determination ± SD. GAE: gallic acid equivalent. Different letters indicate the significant differences between samples in one column according to Tukey's test, p < 0.05.

	Wine Sample	Total Phenolic Content (g GAE/L)	Total Tannins Content (g/L)	Total Pigments Index	SO 2 Bleaching Resistant Pigments Index
	R1	1.9 ± 0.1 d	2.8 ± 0.2 d	19.2 ± 0.9 a	5.4 ± 0.4 b
	R2	1.9 ± 0.1 d	3.2 ± 0.1 c,d	4.9 ± 0.1 d	4.3 ± 0.1 c,d
	R3	2.5 ± 0.1 b	4.4 ± 0.1 a,b	6.0 ± 0.5 d	4.8 ± 0.1 b,c
	R4	2.4 ± 0.1 b	4.2 ± 0.1 a,b	8.35 ± 1.1 c	4.6 ± 0.3 b,c
	R5	2.6 ± 0.1 b,c	3.4 ± 0.1 c	9.1 ± 0.1 c	3.5 ± 0.2 d
	R6	2.7 ± 0.2 b	2.8 ± 0.1 d	4.8 ± 0.3 d	1.7 ± 0.1 e
	R7	1.4 ± 0.1 e	2.1 ± 0.1 e	14.7 ± 0.5 b	3.5 ± 0.4 d
	R8	3.1 ± 0.05 a	4.6 ± 0.1 a	16.2 ± 1.3 b	6.8 ± 0.2 a
	R9	2.5 ± 0.1 b	4.1 ± 0.2 b	21.2 ± 1.9 a	7.2 ± 0.1 a

Table 2 .

 2 Oxygen consumption rates (ppm•h -1 ) of wines for the accelerated ageing tests. Values represent means of triplicate determination ± SD. Initial O 2 rate (iOCR) is calculated as tangent to the linear regression O 2 = f (time) in the first 30 min. Average O 2 rate (aOCR) is calculated between the first O 2 value before the aging test and the first O 2 value of the final threshold. Different letters indicate the significant differences between samples in one column according to Tukey's test, p < 0.05.

		Initial O 2 Rate	Average O 2		Initial O 2 Rate	Average O 2 Rate		Initial O 2 Rate	Average O 2
		iOCR	Rate aOCR		iOCR	aOCR		iOCR	Rate aOCR
	R1 • C R2 • C R3 • C R4 • C R5 • C R6 • C R7 • C R8 • C R9 • C	2.40 ± 0.06 a,b 1.83 ± 0.52 a,b,c 2.59 ± 0.32 a 1.07 ± 0.09 c,d 2.14 ± 0.10 a,b 0.87 ± 0.21 c,d 2.4 ± 0.24 a,b 0.7 ± 0.11 d 1.61 ± 0.43 b,c,d	1.27 ± 0.05 a 0.71 ± 0.30 b,c,d 1.02 ± 0.10 a,b 0.54 ± 0.11 c,d 0.93 ± 0.11 a,b,c 0.33 ± 0.12 d 0.86 ± 0.02 a,b,c 0.37 ± 0.06 d 0.89 ± 0.01 a,b,c	R1 lac R2 lac R3 lac R4 lac R5 lac R6 lac R7 lac R8 lac R9 lac	3.33 ± 0.05 b,c 2.58 ± 0.40 c,d 5.47 ± 0.82 a 1.2 ± 0.04 e,f 1.4 ± 0.05 e,f 1.85 ± 0.11 d,e 4.2 ± 0.09 b 0.38 ± 0.10 f 1 ± 0.05 e,f	1.35 ± 0.21 a,b 1.19 ± 0.13 b,c 1.9 ± 0.50 a 0.77 ± 0.09 b,c,d 0.8 ± 0.05 b,c,d 0.57 ± 0.13 c,d 2 ± 0.08 a 0.17 ± 0.03 d 0.54 ± 0.01 c,d	R1 H 2 O 2 R2 H 2 O 2 R3 H 2 O 2 R4 H 2 O 2 R5 H 2 O 2 R6 H 2 O 2 R7 H 2 O 2 R8 H 2 O 2 R9 H 2 O 2	2.86 ± 0.28 c,d 5.1 ± 0.19 b 3.74 ± 0.05 b,c 5.33 ± 0.77 b 4.89 ± 0.89 b 1.69 ± 0.58 d 8.55 ± 0.19 a 9.32 ± 0.25 a 1.69 ± 0.05 d	1.44 ± 0.21 c 2.65 ± 0.74 b 2.35 ± 0.17 b,c 2.9 ± 0.12 b 2.4 ± 0.14 b,c 0.25 ± 0.08 d 2.72 ± 0.09 b 4 ± 0.15 a 0.22 ± 0.06 d

Table 3 .

 3 Voltammetric peak potentials of the standard polyphenols (concentration of 0.1 mM) in model wine solution (pH 3.6) using SWCNT-SPCE. Ep,a 1 represents the potential of the first anodic peak and Ep,a 2 represents the potential of the second anodic peak.

	Standards	Potential (mV) SWCNT-SPCE (vs. Ag (s) )
		Ep,a 1	Ep,a 2
	Catechin	151	476
	Caffeic acid	166	/
	Gallic acid	154	476
	Oenin chloride	398	/
	Quercetin	151	/

240mV ∆Q 520mV ∆(Q 520mV -Q 240mV ) ∆(Q 240mV /Q 800mV ) ∆Q 800mV

			64 ± 0.76 d	20.49 ± 1.74 d	12.83 ± 1.12 e	0.21 ± 0.03 b,c	37.30 ± 1.98 e
	R2		7.42 ± 1.26 d	26.11 ± 2.23 d	18.54 ± 1.01 d,e	0.15 ± 0.02 c,d	50.25 ± 3.21 c,d,e
	R3	9.67 ± 1.55 c,d	27.62 ± 3.32 d	17.94 ± 1.67 d,e	0.23 ± 0.06 b,c	42.57 ± 3.87 e
	R4	19.00 ± 5.41 b	46.00 ± 3.02 b,c	27.96 ± 2.21 b,c	0.29 ± 0.03 a,b	65.11 ± 12.92 b,c,d
	R5	16.21 ± 1.93 b,c	38.25 ± 0.29 c	22.04 ± 1.42 c,d	0.38 ± 0.01 a	43.29 ± 6.78 d,e
	R6	20.73 ± 0.46 b	51.30 ± 4.36 b	30.55 ± 3.62 b	0.31 ± 0.01 a,b	67.75 ± 0.96 b,c
	R7		3.60 ± 0.74 d	17.93 ± 1.82 d	14.33 ± 1.07 e	0.09 ± 0.01 d	37.75 ± 6.28 e
	R8	29.28 ± 2.77 a	96.52 ± 1.12 a	69.71 ± 0.87 a	0.30 ± 0.03 a,b	99.00 ± 1.88 a
	R9	10.67 ± 2.13 c,d	38.98 ± 4.40 c	28.31 ± 2.25 b,c	0.14 ± 0.04 c,d	75.98 ± 8.51 a,b
	B		∆Q 240mV	∆Q 520mV	∆(Q 520mV -Q 240mV ) ∆(Q 240mV /Q 800mV )	∆Q 800mV
	R1	60 • C	0 f	0 d	0 f	0 a	0 d
	R2	60 • C	8.20 ± 0.86 b,c	17.30 ± 0.87 c	9.11 ± 0.01 d	0.34 ± 0.03 a	24.11 ± 0.10 b
	R3	60 • C	0.56 ± 0.53 e,f	3.88 ± 0.46 d	3.35 ± 0.07 e	0.05 ± 0.05 a	10.62 ± 0.8 c,d
	R4	60 • C	10.70 ± 0.37 b	70.20 ± 0.56 a	59.53 ± 0.19 a	0.24 ± 0.01 a	44.32 ± 0.50 a
	R5	60 • C	3.36 ± 2.05 d,e	5.50 ± 4.91 d	2.13 ± 2.87 e,f	0.52 ± 0.60 a	11.70 ± 7.22 c
	R6	60 • C	10.56 ± 1.06 b	23.80 ± 1.64 b	13.24 ± 0.58 c	0.40 ± 0.03 a	26.42 ± 4.41 b
	R7	60 • C	0 f	2.35 ± 1.09 d	2.34 ± 1.02 e,f	0 a	4.61 ± 1.12 c,d
	R8	60 • C	23.22 ± 1.66 a	49.04 ± 6.16 a	50.23 ± 0.82 b	0.48 ± 0.03 a	73.45 ± 2.48 a
	R9	60 • C	5.64 ± 1.06 c,d	16.27 ± 2.15 c	10.64 ± 1.09 c,d	0.17 ± 0.02 a	31.98 ± 5.26 b
	C		∆Q 240mV	∆Q 520mV	∆(Q 520mV -Q 240mV ) ∆(Q 240mV /Q 800mV )	∆Q 800mV
	R1	Lac.	3.37 ± 0.60 c,d,e	5.74 ± 1.59 d,e	2.36 ± 1.00 d,e	0.30 ± 0.09 a,b	11.37 ± 1.48 c
	R2	Lac.	0.22 ± 0.17 e	0.61 ± 0.24 e,f	0.40 ± 0.08 e	0.02 ± 0.01 c	9.49 ± 2.47 c
	R3	Lac.	0 e	0 f	0 e	0 c	1.61 ± 0.53 c
	R4	Lac.	2.05 ± 0.13 d,e	1.48 ± 0.52 e,f	0 e	0.47 ± 0.19 a	4.93 ± 2.11 c
	R5	Lac.	5.88 ± 1.69 c	8.92 ± 2.63 d	3.04 ± 0.94 d,e	0.41 ± 0.03 a	14.15 ± 3.04 c
	R6	Lac.	11.80 ± 1.29 b	32.31 ± 1.48 b	20.50 ± 0.22 b	0.40 ± 0.02 a	29.13 ± 1.43 b
	R7	Lac.	0.63 ± 0.51 e	4.68 ± 1.63 d,e,f	4.03 ± 1.12 d	0.05 ± 0.03 c	12.18 ± 4.83 c
	R8	Lac.	22.80 ± 2.31 a	46.31 ± 8.55 a	48.78 ± 1.59 a	0.50 ± 0.04 a	71.58 ± 0.72 a
	R9	Lac.	5.70 ± 2.09 c,d	16.43 ± 4.40 c	10.73 ± 2.31 c	0.18 ± 0.02 b,c	31.49 ± 8.20 b
	D ∆Q R1 3.29 ± 0.13 c,d H 2 O 2 R2 1.45 ± 0.04 d,e H 2 O 2 R3 3.66 ± 0.88 b,c H 2 O 2 R4 2.22 ± 0.32 c,d H 2 O 2 R5 2.68 ± 0.89 c,d H 2 O 2 R6 13.11 ± 1.46 a H 2 O 2 R7 0 e H 2 O 2 R8 0 e H 2 O 2 R9 H 2 O 2 5.72 ± 1.03 b	5.73 ± 0.08 c,d,e 4.05 ± 1.08 d,e,f 9.56 ± 1.13 b,c 8.13 ± 0.56 b,c,d 5.36 ± 2.49 c,d,e 15.50 ± 3.31 a 1.35 ± 0.19 e,f 0 f 11.92 ± 1.90 a,b	2.45 ± 0.05 b,c 2.7 ± 0.88 b 5.87 ± 0.25 a 5.91 ± 0.23 a 2.68 ± 1.57 b 2.39 ± 1.85 b,c 1.35 ± 0.19 b,c 0 c 6.20 ± 0.87 a	0.07 ± 0.01 a 0.55 ± 0.58 a 0.18 ± 0.03 a 0.16 ± 0.08 a 0.11 ± 0.03 a 0.30 ± 0.01 a 0 a 0 a 0.39 ± 0.09 a	45.39 ± 2.64 a 5.28 ± 4.12 c,d 19.77 ± 1.81 b 17.22 ± 9.48 b,c 23.75 ± 0.53 b 43.27 ± 6.75 a 3.77 ± 1.45 c,d 0 d 15.59 ± 5.98 b,c

Table 5 .

 5 Pearson's correlation coefficients between electrochemical parameters, phenolic composition, and oxygen consumption rates. * (in green) represents significance at p ≤ 0.05 and ** (in red) represent significance at p ≤ 0.01.

		Folin TPC	TC	TP	RP	Q 240mV ref	Q 520mV ref	Q 520mV -Q 240mV ref	Q 240/800mV ref	Q 800mV ref	∆Q 240mV H2O2	∆Q 520mV H2O2	∆(Q 520mV -Q 240mV ) H2O2	Q 240/800mV H2O2 ∆Q 800mV H2O2
	Folin TPC	1.00	0.91 **	-0.08	0.26	0.86 **	0.80 **	0.74 *		0.53	0.74 *	0.31	0.29	0.09		0.00	0.06
	TC		1.00	-0.15	0.36	0.72 *	0.69 *	0.65		0.33	0.73 *	0.25	0.36	0.37		0.14	-0.07
	TP			1.00	0.72 *	-0.10	0.09	0.18		-0.49	0.21	-0.26	-0.25	-0.09		-0.35	-0.06
	RP				1.00	0.10	0.32	0.41		-0.40	0.45	-0.45	-0.29	0.18		-0.06	-0.38
	Q 240mV ref					1.00	0.94 **	0.87 **		0.66	0.80 **	0.18	0.03	-0.25		-0.23	-0.03
	Q 520mV ref						1.00	0.99 **		0.43	0.90 **	0.00	-0.16	-0.35		-0.23	-0.27
	Q 520mV -Q 240mV ref							1.00		0.31	0.90 **	-0.08	-0.24	-0.39		-0.23	-0.37
	Q 240/800mV ref									1.00	0.09	0.14	0.00	-0.25		-0.35	0.31
	Q 800mV ref										1.00	0.14	0.07	-0.09		0.07	-0.30
	∆Q 240mV H2O2											1.00	0.90 **	0.21		0.37	0.70 *
	∆Q 520mV H2O2												1.00	0.62		0.47	0.63
	∆(Q 520mV -Q 240mV ) H2O2													1.00		0.39	0.14
	∆Q 240/800mV H2O2															1.00	0.00
	∆Q 800mV H2O2																1.00
		∆Q 240mV lac	∆Q 520mV lac	∆(Q 520mV -Q 240mV ) lac	∆Q 240/800mV lac	∆Q 800mV lac	∆Q 240mV 60 • C	∆Q 520mV 60 • C	C ∆(Q 520mV -Q 60 • 240mV )	C ∆Q 240/800mV 60 •	∆Q 800mV 60 • C	aOCR H 2 O 2	aOCR lac	aOCR 60 • C	iOCR H 2 O 2	iOCR lac	iOCR 60 • C
	Folin TPC	0.71 *	0.65	0.53	0.62	0.58	0.67 *	0.55	0.49	0.66	0.65	0.02	-0.77 *	-0.49	-0.12	-0.58	-0.63
	TC	0.49	0.48	0.33	0.40	0.39	0.63	0.63	0.60	0.43	0.74 *	0.06	-0.61	-0.48	-0.15	-0.43	-0.60
	TP	0.23	0.26	-0.49	0.10	0.43	-0.03	-0.03	-0.02	-0.35	-0.03	-0.10	-0.15	0.36	0.08	-0.22	0.07
	RP	0.24	0.29	-0.40	0.02	0.36	0.26	0.29	0.28	-0.15	0.35	0.23	-0.27	0.21	0.14	-0.27	-0.06
	Q 240mV ref	0.86 **	0.81 **	0.66	0.83 **	0.65	0.87 **	0.80 **	0.73 *	0.74 *	0.76 *	0.25	-0.82 **	-0.75 *	0.21	-0.71 *	-0.84 **
	Q 520mV ref	0,93 **	0.92 **	0.43	0.69 *	0.79 *	0.94 **	0.81 **	0.72 *	0.66	0.80 **	0.36	-0.79 *	-0.72 *	0.38	-0.69 *	-0.82 **
	Q 520mV -Q 240mV ref	0.93 **	0.94 **	0.31	0.59	0.83 **	0.93 **	0.78 *	0.68 *	0.60	0.78 *	0.40	-0.74 *	-0.68 *	0.44	-0.65	-0.77 *
	Q 240/800mV ref	0.39	0.28	1.00 **	0.68 *	0.02	0.34	0.34	0.32	0.62	0.16	0.28	-0.33	-0.33	0.11	-0.25	-0.31
	Q 800mV ref	0.81 **	0.82 **	0.09	0.54	0.83 **	0.90 **	0.79 *	0.71 *	0.53	0.91 **	0.10	-0.84 **	-0.74 *	0.16	-0.76 *	-0.88 **
	∆Q 240mV H2O2	0.13	0.08	0.14	0.17	0.20	-0.02	-0.16	-0.20	0.15	0.02	-0.84 **	-0.28	-0.27	-0.77 *	-0.10	-0.31
	∆Q 520mV H2O2	-0.14	-0.19	0.00	0.04	-0.04	-0.18	-0.16	-0.15	-0.03	0.05	-0.84 **	-0.17	-0.10	-0.88 **	-0.02	-0.17
	∆(Q 520mV -Q 240mV ) H2O2	-0.55	-0.57	-0.25	-0.23	-0.45	-0.35	-0.08	0.02	-0.34	0.07	-0.36	0.12	0.27	-0.59	0.14	0.17
	∆Q 240/800mV H2O2	-0.28	-0.28	-0.35	-0.38	-0.08	-0.01	-0.14	-0.18	0.16	0.17	-0.44	-0.14	-0.12	-0.55	-0.10	-0.11
	∆Q 800mV H2O2	-0.09	-0.19	0.31	0.26	-0.15	-0.35	-0.36	-0.34	-0.13	-0.40	-0.70 *	-0.02	0.26	-0.75 *	0.11	0.10

Table 5 .

 5 Cont.

		∆Q 240mV lac	∆Q 520mV lac	∆(Q 520mV -Q 240mV ) lac	∆Q 240/800mV lac	∆Q 800mV lac	∆Q 240mV 60 • C	∆Q 520mV 60 • C	C ∆(Q 520mV -Q 60 • 240mV )	C ∆Q 240/800mV 60 •	∆Q 800mV 60 • C	aOCR H 2 O 2	aOCR lac	aOCR 60 • C	iOCR H 2 O 2	iOCR lac	iOCR 60 • C
	∆Q 240mV lac	1.00	0.99 **	0.39	0.68 *	0.91 **	0.83 **	0.59	0.48	0.63	0.59	0.17	-0.77 *	-0.62	0.29	-0.66	-0.74 *
	∆Q 520mV lac		1.00	0.28	0.58	0.92 **	0.84 **	0.59	0.47	0.55	0.60	0.21	-0.70 *	-0.63	0.36	-0.59	-0.72 *
	∆Q( 520mV -Q 240mV ) lac			1.00	0.68 *	0.02	0.34	0.34	0.32	0.62	0.16	0.28	-0.33	-0.33	0.11	-0.25	-0.31
	∆Q 240/800mV lac				1.00	0.48	0.61	0.65	0.63	0.60	0.53	0.10	-0.77 *	-0.48	0.08	-0.76 *	-0.70 *
	∆Q 800mV lac					1.00	0.72 *	0.43	0.31	0.50	0.55	-0.06	-0.75 *	-0.54	0.16	-0.67 *	-0.68 *
	∆Q 240mV 60 • C ∆Q 520mV 60 • C ∆(Q 520mV -Q 240mV ) 60 • C ∆Q 240/800mV 60 • C ∆Q 800mV 60 • C aOCR H 2 O 2						1.00	0.88 ** 1.00	0.79 * 0.99 ** 1.00	0.68 * 0.46 0.36 1.00	0.89 ** 0.92 ** 0.88 ** 0.55 1.00	0.39 0.48 0.49 0.19 0.26 1.00	-0.79 * -0.66 -0.58 -0.76 * -0.78 * 0.07	-0.83 ** -0.75 * -0.68 * -0.65 -0.79 * -0.17	0.39 0.41 0.40 0.14 0.21 0.89 **	-0.72 * -0.66 -0.60 -0.73 * -0.75 * -0.03	-0.90 ** -0.84 ** -0.78 * -0.64 -0.89 ** -0.05
	aOCR lac aOCR 60 • C												1.00	0.62 1.00	0.08 -0.27	0.95 ** 0.57	0.85 ** 0.90 **
	iOCR H 2 O 2														1.00	-0.06	-0.10
	iOCR lac															1.00	0.80 **
	iOCR 60 • C																1.00

Data Availability Statement: Data is contained within the article and Supplementary Material.

Conflicts of Interest:

The authors declare no conflict of interest.

Another PCA representation gathering all the electrochemical parameters (before and after oxidation) also reveals a discrimination into three main groups (Supplementary data Figure S1) and confirms previous results.

Conclusions

Overall, the results of this work confirm that different wine ageing tests produce distinct results for different red wines, depending on the chemical molecules targeted [START_REF] Ferreira | Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO 2[END_REF][START_REF] Carrascón | The kinetics of oxygen and SO 2 consumption by red wines. What do they tell about oxidation mechanisms and about changes in wine composition?[END_REF][START_REF] Coppola | Comparison of Three Accelerated Oxidation Tests Applied to Red Wines with Different Chemical Composition[END_REF]. These wines also showed different electrochemical behavior (cyclic voltammetry) before and after oxidation protocols. Wines were discriminated into three main groups depending on their electrochemical behavior, chemical composition, and OCRs: the first group gathered three Syrah wines from the same winery with different ages, the second one gathered two 2019 Syrah wines, while the other samples were gathered in the last group.

Electrochemical parameters before oxidation (temperature and laccases) revealed a discrimination into three groups between red wine samples according to their oxygen consumption rates. Electrochemistry and more specifically cyclic voltammetry appears then as a promising method to predict red wine oxidation and seems to be effective even on older vintages. Moreover, this method appears to be fast and allows us to obtain results with really few samples.

Further research is needed in order to confirm the obtained results by the oxidative and electrochemical characterization in a larger series of red wines.

Supplementary Materials:

The following are available online at https://www.mdpi.com/article/ 10.3390/antiox10121943/s1. Table S1: enological analytic characterization of the red wines, Table S2: free SO 2 levels in the red wines after the different oxidation tests, Figure S1: representation of the scores (wines) (variables-electrochemical parameters for the reference wines (Q) and oxidized wines by the three protocols minus reference wines (∆Q)) in the plane defined by respectively the first (F1) and second (F2) factor (explained variance: 79.55%).

Author


Adrien Bourgeade
email: adrien.bourgeade@ec-nantes.frmalek.ghanes@ec-nantes.fr

Malek Ghanes

Maurice Fadel
email: maurice.fadel@laplace.univ-tlse.fr

Abdelkader Bouarfa
email: abdelkader.bouarfa@renault.com

Jean-Pierre Barbot
email: barbot@ensea.fr

Off-line

teaching and research institutions in France or abroad, or from public or private research centers.

Off-line PWM control with a three phases relaxed symmetry applied to a two-level inverter

Bourgeade Adrien 1 , Malek Ghanes 1 , Fadel Maurice 2 , Bouarfa Abdelkader 3 , Barbot Jean-Pierre 4

Abstract-To control static converters, several Pulse Width Modulation (PWM) was proposed. Their aim was to achieve a specific minimisation by choosing the inverter switching angles. Optimal pulse patterns could be obtained considering classic symmetries on a single leg. Also known as Quarter Wave Symmetry (QWS) , Half Wave Symmetry or Full Wave Symmetry (FWS). By this way the angles on each leg can be easily deduced from the solution of the first leg, it is also known that the harmonics multiple of three are systematically removed. In this work, any symmetry is considered and simulation results are provided according to this new strategy based on relaxation symmetry. Evaluation is done with four objectives functions Weighted Total Harmonic Distortion (WTHD) and three types of electric motor models. According to the models, the new strategy is compared to the case where the symmetries (QWS,HWS and FWS) are considered. In the motor models is computed efficiency, which includes switching and conduction losses inside the legs of the inverter. Models and methods was evaluated in simulation with arbitrary parameters.

Index Terms-PWM, Optimised pulse patterns, Three-phase symmetry relaxation, off-line optimisation.

I. INTRODUCTION

In order to change the AC power of an electrical motor allowing to control the motor, an inverter is needed. It will transform the tension of the battery (continuous) to a tension which can be used by a motor (three alternative phases). In an automotive context, there are many problems which have to be considered, the first one is a cost problem. This problem leads us to consider a minimum of switches. In this paper it is considered here an inverter with only six switches composed each of an IGBT with an anti-parallel diode. This inverter is then composed of three legs and is commanded by two levels of tension.

Carrier based PWM exists since years to control power electronic devices such as inverters. Many works tried to improve the PWM by injecting harmonics in the modulated signal [START_REF] Holtz | Pulsewidth modulation for electronic power conversion[END_REF]- [START_REF] Capitaneanu | General and algebraic synthesis for pwm methods[END_REF], or on searching vector modulation methods [START_REF] Bozorgi | Optimum switching pattern of matrix converter space vector modulation[END_REF], [START_REF] Zhou | Relationship between space-vector modulation and three-phase carrier-based pwm: a comprehensive analysis [three-phase inverters[END_REF].

The gold standard of PWM strategies is the Space Vector Modulation (SVM), indeed it demonstrated an important efficiency in comparison with the Sinusoïdal PWM (SPWM). SVM also allows an extension of the linear zone, this effect have a positive influence on Total Harmonic Distortion (THD) [START_REF] Holtz | Advanced pwm and predictive control -an overview[END_REF], [START_REF] Holmes | Pulse Width Modulation for Power Converters: Principles and Practice[END_REF]. SVM strategy is often used to command inverter connected with motors thanks to its vector representation. It has been also shown that SVM strategy can be replaced by a zero sequence component injection [START_REF] Holmes | Pulse Width Modulation for Power Converters: Principles and Practice[END_REF], [START_REF] Bozorgi | Optimum switching pattern of matrix converter space vector modulation[END_REF], [START_REF] Zhou | Relationship between space-vector modulation and three-phase carrier-based pwm: a comprehensive analysis [three-phase inverters[END_REF]. Thanks to this method SVM strategy can be understood as a carrier based strategy.

More recently a new class of PWM (off-line) appeared with technical progress (Micro-controllers) [START_REF] Birth | Generalized three-level oprimal pulse patterns with lower harmonic distortion[END_REF]- [START_REF] Sorokin | An efficient method to calculate optimal pulse patterns for multi-level converters[END_REF]. Off-line PWM are also called Optimal Pulse Patterns (OPP).

The computation based on a mathematical model for OPPs is the most common way to compute solutions [START_REF] Birth | Generalized three-level oprimal pulse patterns with lower harmonic distortion[END_REF], [START_REF] Birth | Model predictive control of a medium-volatage gridconnected converte with LC filter usinp optimal pulse patterns with relaxed symmetry[END_REF], [START_REF] Birda | Synchronous optimal pulse-width modulation with differently modulated waveform symmetry properties for feeding synchronous motor with high magnetic anisotropy[END_REF]- [START_REF] Fei | A generalized formulation of quarterwave symmetry she-pwm problems for multilevel inverters[END_REF]. These papers are concerned about minimisation of THD or WTHD with different algorithms because it is very simple to compute, and, furthermore WTHD is a good way to evaluate current behaviour in an motor without considering motor parameters.

One of the main advantages of off-line solutions, is their linear zone extended to the modulation index m max = 2 π , [START_REF] Holmes | Pulse Width Modulation for Power Converters: Principles and Practice[END_REF]. This way all the off-line strategies should be better than the SVM one.

In [START_REF] Birth | Generalized three-level oprimal pulse patterns with lower harmonic distortion[END_REF], [START_REF] Hartgenbusch | Optimized pulse patterns for salient synchronous machines[END_REF], they evaluate respectively OPP for WTHD and salient pole synchronous machine. Their approach is based on harmonic evaluation.

Other people worked on the Selective Harmonic Elimination PWM (SHEPWM). The principle is to select precise harmonics to eliminate and then trying to eliminate them, [START_REF] Cikač | Pulse pattern optimization based on brute force method for mediumvoltage three-level npc converter with active front end[END_REF], [START_REF] Fei | A generalized formulation of quarterwave symmetry she-pwm problems for multilevel inverters[END_REF], [START_REF] Sahali | Selective harmonic elimination pulsewidth modulation technique (she pwm) applied to three-level inverter / converter[END_REF]. This objective is the second most classic objective function with WTHD. SHEPWM is not considered here, because it seems to be a particular case of WTHD, furthermore, choosing among all the harmonics which one to eliminate in order to reduce engine losses is quite complex.

The work presented here do a study on off-line PWM modulation, these solutions will be used in a control loop to feed a synchronous motor in an electric vehicle for our industrial partner. The control loop is considered here as a black box sending correct information about signal frequency (f 1 ) and desired tension (m.E DC , here m is called modulation index and E DC the bus tension). For now this study is only based on simulations consisting a first step to evaluate PWM strategies but not ideal. This decision was taken to have as quick as possible a first good approximation of what expected with a real motor. The purpose of this paper is to propose a complete and directly applicable optimisation problem, and a PWM strategy comparison between the proposed solution without symmetry and a classical symmetry FWS. FWS has demonstrated in [START_REF] Birth | Model predictive control of a medium-volatage gridconnected converte with LC filter usinp optimal pulse patterns with relaxed symmetry[END_REF] its superiority in front of SVM, QWS and HWS.

In the rest of the paper, a recall about mathematical modelling of objective functions is done in section II. The new method is then presented on section III. Section IV is reserved for the computation method of solutions. Section V, a discussion of the results obtained with models of section II is done. In conclusion some perspectives of improvements are given.

II. OBJECTIVE FUNCTION DESCRIPTION

To evaluate correctly the losses inside the inverter and the motor, it is necessary to consider the motor in order to do computations. Nevertheless the solutions found can be used for many applications, and many kind of loads, which involves an inverter. The computation method, is here applied in an automotive context but can be transposed to any another problem. The automotive context was chosen because of our industrial partner.

The motor model will be used for two purposes. The first one is to do the optimal computation. That mean that the computation must be as quick as possible. But, on another hand, it is necessary to have a reliable model to be very precise on the expected results on a real motor.

Four types of models are considered in this study. They are the WTHD and three other models of motor, one called RL, another RLE, and a dq motor model. The RL one is not really a classical motor model. But it's main advantage is its simplicity. The two last motors are more complicated, and even if they are not perfect, they afford a good approximation of solutions quality. In all the following models R, represent a resistance, L an inductance and ω a pulsation with ω = 2πf 1 .

Let's consider an ideal model of an inverter as (1), also see Fig. 1 for the associate electric diagram [START_REF] Holmes | Pulse Width Modulation for Power Converters: Principles and Practice[END_REF].

  V an V bn V cn   = E DC 3   2 -1 -1 -1 2 -1 -1 -1 2   •   S a S b S c   (1)
E DC is the bus tension, S x is the command of the leg x and V xn is the simple tension in the leg x of the motor.

A. WTHD

A lot of studies worked with the WTHD, because of its motor parameters dependency furthermore it allow to evaluate the quality of the solutions really fast and easily. The WTHD equation is represented as 2 [START_REF] Holmes | Pulse Width Modulation for Power Converters: Principles and Practice[END_REF].

V WTHD,% = 100 V 1 n≥2 V n n 2 (2)
V 1 is the desired tension, which is also the fundamental tension and V n is the tension of n th harmonic.

In order to implement it in a solver, a modified WTHD is computed (3). This equation do not have any physic meaning but is useful to study the solutions.

V WTHDm = n≥2 a 2 n,V + b 2 n,V n 2 (3)
a n,V and b n,V are the Fourier coefficients of the n th harmonic tension.

B. The RL and RLE model

First of all, the following models are not exacts, and do not fit to usual motor models. The purpose of these models is to compare them with a real engine (dq model here). The objective is to choose the model, which, with the optimisation afford the best dq results. In another words, RL model is only useful in our optimisation context. If the motor is represented only with a resistance and an inductance, the current equation will be described by [START_REF] Bouarfa | An optimization formulation of converter control and its general solution for the four-leg twolevel inverter[END_REF]. With the knowledge of this current the losses insides the switches can be computed, indeed switches losses are linked to current value.

i(α) =   i 0 -E DC n≥1 Ra n -nLωb n (nLω) 2 + R 2   e -Rα Lω + E DC n≥1 (Ra n -nLωb n ) cos(nα) (nLω) 2 + R 2 + E DC n≥1 (Rb n + nLωa n ) sin(nα) (nLω) 2 + R 2 (4)
On (4), a transient period term is observed and has inside it a e -Rα Lω , which depend of the electric angle, that mean that it also depend of time. Let's observe that lim α→∞ e -Rα Lω = 0. In section IV optimisation computation is done without transient period.

The steady state term is identified in the second part of the equation ( 4). Extraction of current Fourier coefficients is then done in [START_REF] Capitaneanu | General and algebraic synthesis for pwm methods[END_REF].

a n,I = E DC Ran-nLωbn (nLω) 2 +R 2 b n,I = E DC Rbn+nLωan (nLω) 2 +R 2 (5)
To compute the RLE model an Electromotive force is added. This force will react as a voltage source inside the legs of the RL device (see figure 1). This figure represent one of the most basic motor model, which is very useful for people that work in command control to develop a quick start controller for the motor. The main problem related to this model, that it is not precise enough to represent correctly a salient electric motor. With this model the equations ( 4) is modified to give us (6)

i(α) =   i 0 + E(ω) R -E DC n≥1 Ra n -nLωb n (nLω) 2 + R 2   e -Rα Lω + E DC n≥1 (Ra n -nLωb n ) cos(nα) (nLω) 2 + R 2 + E DC n≥1 (Rb n + nLωa n ) sin(nα) (nLω) 2 + R 2 - E(ω) R (6)
let's remark that the Electromotive force vary depending on the motor speed, and is not explicit here.

C. The dq model

The dq model 2 need more computation time than the previous ones because of numerical differential resolution. Then, if that equation does not afford enough advantages, more simple models will be preferred. Fig. 2 can be also written with differential equations [START_REF] Zhou | Relationship between space-vector modulation and three-phase carrier-based pwm: a comprehensive analysis [three-phase inverters[END_REF] and [START_REF] Birth | Generalized three-level oprimal pulse patterns with lower harmonic distortion[END_REF].

di d dt = V d L d + L q L d ωi q - R s L d i d (7) di q dt = V q L q - L d L q ωi d - R s L q i q - 3 2 ωφ f L q (8)
With these equations, like for models presented in section II-B, a current equation is established 9 [START_REF] Park | Two-reaction theory of synchronous machines generalized method of analysis-part i[END_REF]. Current which is useful to compute the losses inside the inverter as seen in section II-D.

i abc = 2 3   cos(θ) -sin(θ) cos(θ -2π 3 ) -sin(θ -2π 3 ) cos(θ + 2π 3 ) -sin(θ + 2π 3 )   i d i q (9)
With θ = ωt and homopolar current is equal to zero (i h = 0) because of the balanced motor .

D. Losses in the inverter

In (1), the inverter is supposed perfect. But it exists losses inside this power device. The main losses in the inverter are due to IGBT and diode losses. There is two kind of losses, the conduction losses [START_REF] Cikač | Pulse pattern optimization based on brute force method for mediumvoltage three-level npc converter with active front end[END_REF] and the switching losses [START_REF] Hartgenbusch | Optimized pulse patterns for salient synchronous machines[END_REF]. The first one is due to the internal resistance of the semiconductors. The second one, is due to the current discontinuities.

P cond = 1 2π 2π 0 u(α)V ce |i(α)|dα (10)
P sw = 1 2 f 1 N dec i=1 (E on (α i ) + E of f (α i )) + 1 2 f 1 N dec i=1 (-1) i (E on (α i ) -E of f (α i )) (11)
Equations ( 10) and ( 11) [START_REF] Capitaneanu | General and algebraic synthesis for pwm methods[END_REF] are quite simple. Indeed they depend on few parameters and on the angle position. The sub functions V ce , E on and E of f are given by the data sheets of the chosen semiconductors. u is equal to one when the switch let the current go through the semiconductor and zero otherwise. u depends on the OPP found, it is the same for i (current) computed in previous sections for the different models. Finally because E on and E of f depend on the current when the switch will be opened or closed. So E on and E of f also depend on the OPP found by the algorithm. To simplify the computation, IGBT and diode are assumed to have the same characteristics.

E. Efficiency computation

To compute the efficiency, two information are needed. The first one is the useful power, and the second one are the losses. For the useful power, it depends on the motor model. About the losses a sum of the spoiled power and the inverter losses computed in section II-D is performed. The complete expression of the computation is then accessible with ( 12), ( 13) and [START_REF] Birda | Synchronous optimal pulse-width modulation with differently modulated waveform symmetry properties for feeding synchronous motor with high magnetic anisotropy[END_REF]. η symbol designate an efficiency.

η RL = 3V 1 I 1 cos(φ 1 ) 3P cond + 3P sw + 3 n≥1 (V n I n cos(φ n )) (12)
η RLE = 3E(ω) • I 3P cond + 3P sw + 3 n≥1 (V n I n cos(φ n )) (13)
η dq = ΓΩ 3P cond + 3P sw + 3 n≥1 (V n I n cos(φ n )) (14)
Here Γ represent the torque of the motor in N.m and Ω the motor speed in rad.s -1

III. NEW OPTIMISATION PROBLEM SETTING

The new method purpose is to do the hypothesis that the symmetry between phases do not exist anymore, but will be forced by constraints in the optimisation problem. With this new hypothesis, the optimisation problem is now written like [START_REF] Shi | Optimized random pwm strategy based on genetic algorithms[END_REF]. The idea, here is to find the optimal pulse pattern, according to the chosen objective function ((3), ( 12) or ( 13)). This relaxation of the assumptions will increase the quality of the solutions. Indeed feeding this optimisation problem with a FWS solution as starting point, will ensure that the solution will be better than the FWS one. In the worst case the solution quality will be the same than the FWS one.

A. Angle optimisation problem setting

                               f.o min(f (x)) s.c x = [x a ; x b ; x c ] x a,k ≤ x a,k+1 + dx min x b,k ≤ x b,k+1 + dx min x c,k ≤ x c,k+1 + dx min x a,4N +2 ≤ u b , x b,4N +2 ≤ u b , x c,4N +2 ≤ u b x a,1 ≥ l b , x b,1 ≥ l b , x c,1 ≥ l b a 0,a = 0, a 0,b = 0, a 0,c = 0 a 1,a = 0, a 1,b = - √ 3 2 m, a 1,c = √ 3 2 m b 1,a = m, b 1,b = -1 2 m, b 1,c = -1 2 m (15) With ∀k ∈ 1; 4N + 2 .
In problem [START_REF] Shi | Optimized random pwm strategy based on genetic algorithms[END_REF], f designates the chosen objective function ((3), ( 12) or ( 13)), and N the number of switches per quarter period. Constraints, are designed to respect three conditions. Time between switching times cannot be lower to dx min . Switching angles are bounded on a period (TABLE I) and finally, all the tensions must respect the correct tension with a correct initial phase for the fundamental.

To analyse the new method command, the same equation than for the FWS given by [START_REF] Birth | Generalized three-level oprimal pulse patterns with lower harmonic distortion[END_REF] is used. They are the same equations except that the angle index number vary between 1 and 4N +2. The main difference is that here the symmetry between the phases does not exist, then no harmonics will be forced to be equal to zero. In the problem [START_REF] Shi | Optimized random pwm strategy based on genetic algorithms[END_REF], k is inside 1 and 4N + 2. So it could appears there is one more switching in comparison than FWS and 2 more switching in comparison with QWS and HWS. But, The first additional switching is due to the symmetry which requires to have a switching in π. The second additional switching is due to the 2π symmetry, that add a switching at the end of the period.

IV. PROPOSED RESOLUTION

In order to compute the solutions, fmincon function from MatLab is used. Because the space of work is full of local minimum, a good starting point have to be chosen. Some random initial points are created. Then a quality evaluation of each point is performed with [START_REF] Shi | Optimized pwm strategy based on genetic algorithms[END_REF]. This equation consider the current value of the objective function which is modified, according to the respect of constraints with penalty coefficients. This way a good starting point will be selected, a starting point which have a good fitness and violate a minimum of constraints.

f v = f (x) + K 1 i (max(c i , 0)) + K 2 i g i (16)
In [START_REF] Shi | Optimized pwm strategy based on genetic algorithms[END_REF], inspired by the work presented in [START_REF] Sierra | Improving pso-based multi-objective optimization using crowding, mutation and -dominance[END_REF], f v represents the current objective value with constraint penalties. f , is the objective function (see II for more details). x the solution to test. K 1 and K 2 are two penalty constants to choose (for example K 1 = K 2 = 10 6 ). c is the vector of constraints, defined as lower than zero if the constraint is respected and greater than zero if the constraint is violated. In ( 16), g i is defined as follow:

g i = 1 if c i > 0 0 otherwise ∀i (17)
The first penalty of ( 16) indicates how far away the current solution is from the feasible domain and the second penalty indicates how many constraints are violated.

After application of the equation ( 16), to a large quantity of points and selection of the best fitness point. fmincon try to solve the problem [START_REF] Shi | Optimized random pwm strategy based on genetic algorithms[END_REF], from the point found previously. Furthermore, in order to keep the solution quality, computation with fmincon is done to two other starting points. The first starting point is found by doing an extension of the previous symmetry. In another words an extension of QWS is done to compute the HWS (equation ( 18)), the HWS to compute FWS(equation [START_REF] Fei | A generalized formulation of quarterwave symmetry she-pwm problems for multilevel inverters[END_REF]) and FWS to compute solutions without symmetry (equation ( 20)).

x H = [x Q,1 , • • • , x Q,N , π -x Q,N , • • • , π -x Q,1 ] (18) x F = [x H,1 , • • • , x Q,2N , π, π + x H,1 , • • • , π + x H,2N ] (19) x tot =    x F sort((x F -2π 3 ) mod 2π) sort((x F -4π 3 ) mod 2π) (20)
The second point chosen is the solution for the previous modulation index. This way the solution when m = 0.5, will be one of the starting point of the computation m = 0.501. This way, the previous local minimum is conserved.

The method has been evaluated on a very simplified motor of four poles pair.

V. SIMULATION RESULTS AND DISCUSSION

A. Results

In the Fig. 3, the WTHD value computed with the WHD objective function ( 2) is shown for two strategies, the FWS and the new method. The switching frequency is set at f s = 2f 1 , in another words N = 2 (N is the number of commutations per quarter period). In the same way, Fig. 4 was computed with the RL objective function [START_REF] Fotouhi | An efficient method to calculate optimal pulse patterns for medium voltage converters[END_REF] and Fig. 5 with the RLE (13) one. Here only the results for N = 2 are represented for readability. But results have been found for N = 2 to N = 5.

On each curve and for the computed objective function our method is at least as good as FWS. This way the proposed strategy is shown to be the best way to compute the commutation angle in the considered symmetries. Nevertheless, the advantage is often small. For the WTHD objective function, the gain is visible only when m is high enough Fig. 3.

On TABLE II and TABLE III, different results from a specific objective function are represented. For each a computation of the related function and the dq efficiency was performed. The second one is useful in order to determine which model is the most accurate with the dq model. Indeed dq model is supposed to have the most accurate behaviour of a real motor. To do this comparison between the dq model motor and the other models, the mean value for the FWS and N = 2 ( mF,2 ) (TABLE II), but also for N = 5 ( mF,5 ) is computed. The same thing was done for the proposed strategy ( mT,2 and mT,5 ). In another hand maximal gain for the considered objective function is computed, called ∆ (TABLE III).

This way a mean gain of 0.05% for the WTHD is observed, 0.89% for the RL model and 2.45% for the RLE one.

About the potential punctual gain it can reach 0.2% for the WTHD, more than 14% for the RL model, and 13.5% for the RLE one. According to the highest mean of dq efficiency, it appears that the RLE model is the most accurate one.

The efficiency computed with equation ( 14) is not regular with the other objective functions. Finding a simple model is really important, because computation of the solutions with the dq objective function was not successful because of the computation time. Computation time is one of the reason of why the only considered electrical frequency was 50Hz, which is equivalent to 750rpm. The 750rpm motor speed, is an arbitrary parameter, to test the algorithm and method. Increasing this frequency will result in an increasing of the minimal gap angle between the switches, and, as an implication, the solutions will be different.

Here, all the results has been computed with arbitrary parameters then it is necessary to see the shape and not the absolute value of efficiency.

B. Discussion

In this paper a demonstration that the new method used is at least as good as FWS, the superiority of the method is then established. But there is a lot of ignored problems that should be interesting to study. Indeed electromagnetic compatibility (EMC) [START_REF] Lezynski | Random modulation in inverters with respect to electromagnetic compatibility and power quality[END_REF], or noise and harshness [START_REF] Takahashi | Optimum pwm waveforms of an inverter for decreasing acoustic noise of an induction motor[END_REF]- [START_REF] Gieras | Noise of Polyphase Electric Motors[END_REF] are ignored here but cannot be neglected. Furthermore the behaviour of the OPP found previously while the motor starting (i.e. in transient period) was ignored too. Furthermore these results has been only found in simulation. It also remains to implement these solutions on a real electric motor, which is not easy because the number of switching per quarter period can change every time in order to respect the motor synchronism. This last point is perhaps the major problem of off-line PWM strategies.

The difference between strategies will be perhaps small, and on a real motor, the new strategy gain could be hard to measure because of sensors uncertainties.

VI. CONCLUSION

In this paper a new PWM method with a relaxation of symmetry was proposed. Four objective functions was presented, in order to test the method and compare it with more classical PWM. The simulation results have been obtained with three objective functions among the four defined. For all the computed results, the new strategy afford the best results or at least the same quality than the FWS solution. In next works it will be necessary to implement this strategy on a real motor, in order to confirm the feasibility of the proposed method.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Scheme of the RLE model

Fig. 3 .Fig. 4 .Fig. 5 .

 345 Fig. 3. Comparison between FWS and relaxed method according to WTHD for N = 2 when the objective function is WTHD

TABLE I

 I

	: Optimisation parameters for (15)
	symmetries/parameters	l b	u b
	New method	dx min 2π -dx min

TABLE II :

 II Comparison between solutions: mean value of the solutions for two different N

	f.o	f	mF,2	mT,2	mF,5 mT,5
		WTHD	8.1	8.1	4.2	4.2
	WTHD	η dq	19.8	19.8	19.2	19.5
		η RL	66.5 67.67 61.3	61.9
	η RL	η dq	19.3	18.9	19.4	19.3
		η RLE	38.3	40.0	31.7	34.9
	η RLE	η dq	19.4 20.26 19.2	20.1

TABLE III :

 III Comparison between solutions: Maximum gap between our method and FWS for two different N

	f.o	f	∆ 2	∆ 5
		WTHD 0.1	0.2
	WTHD	η dq	2.2	1.3
		η RL	3.3 14.7
	η RL	η dq	6.8	2.0
		η RLE	5.0 13.59
	η RLE	η dq	2.7	5.1

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This work was supported by the project Chair between Renault and Centrale Nantes about performances of electric vehicles propulsion.