Acid In Red Wine Research Articles

Dual-signal detection of tannic acid in red wines based on the peroxidase activity of carbon dots.

Herein, a novel type of phosphorus and iron-doped carbon dot (P,Fe-CD) with outstanding peroxidase activity and excellent fluorescence performance was hydrothermally synthesized to colorimetrically and fluorimetrically detect tannic acid (TA). In the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, the P,Fe-CDs could oxidize colorless TMB to a blue oxidation product (oxTMB) resulting in an increased value of absorbance. Simultaneously, the fluorescence intensity of P,Fe-CDs at 430 nm could be quenched owing to the fluorescence resonance energy transfer (FRET) between P,Fe-CDs and the generated oxTMB. Meanwhile, after adding the TA to the system containing TMB, H2O2 and P,Fe-CDs, the value of absorbance could be decreased and the fluorescence could be recovered because of the reduction reaction between TA and oxTMB. Therefore, fluorescence intensity and value of absorbance could be applied to quantitatively detect TA with good linearities between the concentration of TA and the fluorescence intensity/value of absorbance (0.997 and 0.997 for the colorimetric signal and fluorimetric one, respectively) and low limits of detection (0.093 μmol L-1 and 0.053 μmol L-1 for the colorimetry and the fluorimetry, respectively), which was successfully applied to the detection of TA in red wines. Moreover, we applied a smartphone-assisted method to the point-of-care detection of TA with accurate results, providing a new technique for TA detection and food quality monitoring.

Evaluation of Red Wine Acidification Using an E-Nose System with Venturi Tool Sampling.

The quality of wine is checked both during the production process and upon consumption. Therefore, manual wine-tasting work is still valuable. Due to the nature of wine, many volatile components are released, and it is therefore difficult to determine which elements need to be controlled. Acetic acid is one of the substances found in wine and is a crucial substance for wine quality. Gas sensor systems may be a potential alternative for manual wine tasting. In this work, we have developed a TGS2620 gas sensor module to analyze acetic acid levels in red wine. The gas sensor module was refined according to the Venturi effect along with signal slope analysis, providing promising results. The example included in this paper demonstrates that there is a direct relationship between the slope of the MOS gas sensor response and the acetic acid concentration. This relationship is useful to evaluate the ethanol oxidation in acetic acid in red wine during its production process.

Phenolic Acids in Red Wine Interact Directly with the Protein Fraction of Saliva

Wine-evoked astringency is usually associated with interactions between proanthocyanidins and salivary proteins. Limited information exists about interaction of other wine phenolic compounds with saliva. This study assessed the ability of single phenolic acids and mixes of phenolic acids to interact with salivary protein. Protein diffusion on cellulose membranes and protein precipitation assays were conducted. Single phenolic acids (PA), excepting tannic acid (T), showed concentrationdependent reduction of the area of diffusion of the diffusible salivary protein. PAs were weak precipitants of the salivary protein but strong inducers of soluble PA-salivary protein complexes. T precipitated non-diffusible salivary proteins without effect on the diffusible protein. Compared to single PAs, mixes of gallic acid (G) and PAs showed similar effects regarding inhibition of protein diffusion and formation of soluble PA-protein complexes. Contrarily, T interfered with both effects of PAs. It is concluded that PAs interact directly and diversely with the salivary protein and thence may cause astringency

Determination of the amount of volatile acids in oxidized wines and neutralization of these by using chemical reagents and biological materials

The aim of this paper is as follows: (I) determination of physical and chemical characteristics of the wine; (II) determination of the possibility of neutralizing and improving the characteristics of oxidized wines. Two types of wine (red and white) of the individual manufacturer from at south from river Ibar in the territory of Kosovo and Metohia were analyzed. Experimentally determined physico-chemical characteristics are density and quantity of the following: alcohol; extract; reducing sugars; ash; total acids; volatile acids; total; and free sulfur dioxide. Neutralization of oxidized wines (reduction of quantity of volatile acids) was carried out using chemical reagents (sodium hydrogen carbonate, calcium carbonate, calcium oxide, calcium hydroxide) and biological material (corn flour). By using sodium hydrogen carbonate to neutralize oxidized wines, the amount of volatile acids is reduced by 57% in red wine and 54.6% in white. By using corn flour, the content of volatile acids in red wine is reduced by 56% and in white by 54%, which is confirmed by the traditional experience of application of corn pistes during distillation. The methods of classical analytical chemistry were used to perform the experimental part of this paper.

Formation of amino acid derivatives in white and red wines during fermentation: Effects of non-Saccharomyces yeasts and Oenococcus oeni

This study aimed to investigate the effect of commercial non-Saccharomyces yeasts and Oenococcus oeni on the formation of amino acid derivatives, some of which have neuroactive properties, during fermentation in laboratory-scale processing of white and red wines. Changes in the content of amino acid derivatives during fermentation of large-scale white and red wines were also evaluated. The highest kynurenic, picolinic, and quinolinic acid concentrations were observed in white wine fermented with Torulaspora delbrueckii, Kluyveromyces thermotolerans and Saccharomyces cerevisiae simultaneously. No changes in the content of picolinic and kynurenic acid were observed during large-scale white wine fermentation. Tryptophan ethyl ester concentration in all wines increased significantly during alcoholic fermentation. Natural and O. oeni malolactic fermentation did not alter the content of picolinic acid, a neuroprotective compound, in red wine. The decrease in the content of tyramine, phenylethylamine, and dopamine in laboratory-scale white wines was observed during alcoholic fermentation.

Fabrication of SnO2 decorated graphene composite material and its application in electrochemical detection of caffeic acid in red wine

Metal oxide/graphene composite has become a promising electrode material to improve the performance of electrochemical sensor. Here SnO2 decorated graphene (SnO2-RGO) composite was facilely fabricated by a hydrothermal reduction of graphene oxide with SnCl2, and applied as active electrode material into constructing electrochemical sensor for caffeic acid (CA). The SnO2-RGO composite was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical sensor (SnO2-RGO/GCE) obtained from SnO2-RGO coating of glass carbon electrode showed excellent electrocatalytic performance for the redox reaction of CA. A linear range of 0.15–25 μM and a detection limit of 80 nM (S/N = 3) were achieved in 0.1 M phosphate buffer (pH 7.0). The present electrochemical sensor also showed high selectivity for CA, excellent reproducibility and stability. Eventually, the sensor SnO2-RGO/GCE was successfully applied for CA detection in commercial red wine samples with satisfactory recovery results.

A Sensor Based on Hollow, Octahedral, Cu2O‐Supported Palladium Nanoparticles – Prepared by a Galvanic Replacement Reaction – and Carboxylic Multi‐Walled Carbon Nanotubes for Electrochemical Detection of Caffeic Acid in Red Wine

AbstractA novel nanocomposites prepared from hollow, octahedral cuprous oxide supported palladium nanoparticles (Cu2O‐PdNPs) through a facile galvanic replacement reaction and carboxylic multi‐walled carbon nanotubes (MWCNTs‐COOH) was modified on the surface of glassy carbon electrode (Cu2O‐PdNPs@MWCNTs‐COOH/GCE) to fabricate a sensor for electrochemical detection of caffeic acid. The synergistic effect between Cu2O‐PdNPs and MWCNTs‐COOH exhibited remarkable electrocatalytic activity, higher selectivity and higher sensitivity toward caffeic acid. At optimized test conditions, the Cu2O‐PdNPs@MWCNTs‐COOH/GCE nanocomposites sensor revealed wider linear range of 0.006‐60 μM with a lower detection limit of 0.002 μM (S/N=3) for caffeic acid determination. Eventually, the proposed nanocomposites sensor was successfully applied to determine the concentration of caffeic acid in red wine samples.

A UFLC-MS/MS method for the simultaneous determination of eight bioactive constituents from red wine and dealcoholized red wine in rat plasma: Application to a comparative pharmacokinetic study.

To explore whether alcohol has an effect on the pharmacokinetic behavior of phenolic acids, the main bioactive constituents in red wine, a highly sensitive and simple ultra-fast liquid chromatography coupled with triple quadrupole mass spectrometry (UFLC-MS/MS) method was developed for simultaneous quantitation of eight phenolic acids in plasma samples. Plasma samples were extracted by liquid-liquid extraction and the chromatographic separation was achieved on a Zorbax SB-C18 column within 7.0 min. Results of the validated method revealed that all of the calibration curves displayed good linear regression (r > 0.99). The intra- and inter-day precisions of the analytes were <14.0% and accuracies ranged from -8.5 to 7.3%. The extraction recoveries of the analytes were from 71.2 to 110.2% and the matrix effects ranged from 86.2 to 105.5%. The stability of these compounds under various conditions satisfied the requirements of biological sample measurement. The method was successfully applied to a comparative pharmacokinetic study of phenolic acids in rat plasma. For gallic acid and gentisic acid, the parameters AUC0-t and AUC0-∞ increased remarkably (p < 0.05) after oral administration of red wine, which suggested that alcohol might enhance their absorption. This is the first report to compare the pharmacokinetic behavior of phenolic acids in red wine and dealcoholized red wine.

Sonochemical synthesis of graphene oxide sheets supported Cu2S nanodots for high sensitive electrochemical determination of caffeic acid in red wine and soft drinks

A nanocatalyst based on copper sulfide nanodots grown on graphene oxide sheets nanocompsite (Cu2S NDs@GOS NC) was synthesized by a simple sonochemical techniques and applied in electrocatalytic sensing of caffeic acid (CA). The structural and elemental aspects of Cu2S NDs@GOS NC were analyzed by XRD, XPS, FE-SEM, TEM, and EDX. The interfacial electron transfer property of the composite was probed by EIS. The nanocompsite modified SPCE showed excellent electrocatalytic ability towards redox reaction of CA. Under optimized conditions, Cu2S NDs@GOS NC modified electrode delivered rapid and sensitive amperometric responses towards CA. The linear range was 0.055–2455 μM. Interestingly, the modified electrode able to detect nanomolar concentration of CA and the detection limit is 0.22 nM, which surpassed the detection limits of many existing methods. The Cu2S NDs@GOS NC/SPCE is able to quantify the amount of CA present in carbonated soft drinks and red wine without sample pretreatments.

Highly Efficient Malolactic Fermentation of Red Wine Using Encapsulated Bacteria in a Robust Biocomposite of Silica-Alginate.

Bacteria encapsulation to develop malolactic fermentation emerges as a biotechnological strategy that provides significant advantages over the use of free cells. Two encapsulation methods have been proposed embedding Oenococcus oeni, (i) interpenetrated polymer networks of silica and Ca-alginate and (ii) Ca-alginate capsules coated with hydrolyzed 3-aminopropyltriethoxysilane (hAPTES). On the basis of our results, only the first method was suitable for bacteria encapsulation. The optimized silica-alginate capsules exhibited a negligible bacteria release and an increase of 328% and 65% in L-malic acid consumption and mechanical robustness, respectively, compared to untreated alginate capsules. Moreover, studies of capsule stability at different pH and ethanol concentrations in water solutions and in wine indicated a better behavior of silica-alginate capsules than untreated ones. The inclusion of silicates and colloidal silica in alginate capsules containing O. oeni improved markedly their capacity to deplete the levels of L-malic acid in red wines and their mechanical robustness and stability.

A voltammetric determination of caffeic acid in red wines based on the nitrogen doped carbon modified glassy carbon electrode

We reported an electrochemical determination of caffeic acid (CA) based on the nitrogen doped carbon (NDC). The described sensor material was prepared by the flame synthesis method, which gave an excellent platform for the synthesis of carbon nanomaterials with the hetero atom dopant. The synthesized material was confirmed by various physical characterizations and it was further characterized by different electrochemical experiments. The NDC modified glassy carbon electrode (NDC/GCE) shows the superior electrocatalytic performance towards the determination of CA with the wide linear concentration range from 0.01 to 350 μM. It achieves the lowest detection limit of 0.0024 μM and the limit of quantification of 0.004 μM. The NDC/GCE-CA sensor reveals the good selectivity, stability, sensitivity and reproducibility which endorsed that the NDC is promising electrode for the determination of CA. In addition, NDC modified electrode is applied to the determination of CA in red wines and acquired good results.

Direct determination of phenolic acids and hydroxymethylfurfural in wines elaborated in Vale do São Francisco region-Brazil by HPLC DAD

We describe a direct method to determine gallic acid, hydroxymethylfurfural, vanillic, caffeic, p-coumaric, ferulic, caftaric, cis-coutaric, fertaric and trans-coutaric acids in red wines by direct injection using reverse phase HPLC.

Front-face fluorescence spectroscopy combined with second-order multivariate algorithms for the quantification of polyphenols in red wine samples.

The potential of front-face fluorescence spectroscopy combined with second-order chemometric methods was investigated for the quantification of the main polyphenols present in wine samples. Parallel factor analysis (PARAFAC) and unfolded-partial least squares coupled to residual bilinearization (U-PLS/RBL) were assessed for the quantification of catechin, epicatechin, quercetin, resveratrol, caffeic acid, gallic acid, p-coumaric acid, and vanillic acid in red wines. Excitation-emission matrices of different red wine samples, without pretreatment, were obtained in front-face mode, recording emission between 290 and 450 nm, exciting between 240 and 290 nm, for the analysis of epicatechin, catechin, caffeic acid, gallic acid, and vanillic acid; and excitation and emission between 300-360 and 330-400nm, respectively, for the analysis of resveratrol. U-PLS/RBL algorithm provided the best results and this methodology was validated by an optimized liquid chromatographic coupled to diode array and fluorimetric detectors procedure, obtaining a very good correlation for vanillic acid, caffeic acid, epicatechin and resveratrol.

Using of molecularly imprinted polymers for determination of gallic and protocatechuic acids in red wines by high performance liquid chromatography

The sorption capacities of gallic- and protocatechuic acid-molecularly imprinted polymers (GA-MIP and PCA-MIP, respectively) and non-imprinted polymer (NIP) have been determined on the piston columns by the frontal analyses (FAs). Mobile phases consisted of MeOH, MeOH/H2O (1:1), 12.5% EtOH or ACN. Solutes concentrations used in FAs were 1μg/mL and 50μg/mL. All sorption capacities were depended on analyte and solvent used. Results obtained from the FAs have shown that both imprinted polymers almost always were preferentially recognized PCA molecule. Only in MeOH, the GA-MIP had ability to recognize its template molecule positively. Surprisingly, in some cases, also the NIP exhibited higher sorption capacities than the MIPs for their templates, e.g. in ACN for GA or in MeOH for PCA. This behaviour indicates that in some solvents, the low affinity sites of the blank polymer can act as strong interacting sites. In the next, prepared MIPs were successfully used as the SPE-sorbents for the extraction and purification of chosen phenolic acids from red wine samples. The recoveries both of MIPs were the highest for PCA, what was in agreement with the experiments carried out in 12.5% EtOH during FAs. Prepared MIP-beads allowed the purification of chosen red wine samples with satisfactory selectivities and high recoveries. The linearity of the method was in the range from 10μg/mL to 70μg/mL and 0.1μg/mL to 4.5μg/mL for GA and PCA, respectively, with the determination coefficients ranging from 0.996–0.999. The LODs (S/N=3) ranged from 0.1μg/mL to 0.4μg/mL. The RSDs for the recoveries varied from 4.0% to 8.1%. The PAs-MIPs and corresponding NIP were also characterized by attenuated total reflectance analysis Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron analysis (SEM).

Study of changes organic acids in red wines during malolactic fermentation

The aim of this contribution is to be able to describe the movement of organic acids in red wine during malolactic fermentation. Wines from Znojmo wine region were represented by varieties of Svatovavřinecké (Saint Laurent), Rulandské modré (Pinot Noir), Zweigeltrebe, Frankovka (Lemberger) and Dornfelder. The grapes went through the same way of wine making and after completion of alcoholic fermentation were inoculated with pure culture of lactic acid bacteria Oenococcus oeni. Samples were taken for chemical analysis during biodegradation of acids within the range of 2 to 4 days and they were measured using a device WineScan FT 120. Chemical analysis detected changes in the concentrations of the following parameters: total acidity, lactic, malic, tartaric and citric acids. The total content of acids statistically significantly (P = 0.05) differed only between samples of Svatovavřinecké T 66 and Zweigeltrebe T 2.The differences of average mass concentrations of lactic, malic and citric acids were not statistically relevant. Nevertheless, statistically relevant difference in the concentration of tartaric acid from all other wines was detected in a sample of SV T 66 which also reached the highest average value (5.18 g/l).

Metabolism of Nonesterified and Esterified Hydroxycinnamic Acids in Red Wines by Brettanomyces bruxellensis

While Brettanomyces can metabolize nonesterified hydroxycinnamic acids found in grape musts/wines (caffeic, p-coumaric, and ferulic acids), it was not known whether this yeast could utilize the corresponding tartaric acid esters (caftaric, p-coutaric, and fertaric acids, respectively). Red wines from Washington and Oregon were inoculated with B. bruxellensis, while hydroxycinnamic acids were monitored by HPLC. Besides consuming p-coumaric and ferulic acids, strains I1a, B1b, and E1 isolated from Washington wines metabolized 40-50% of caffeic acid, a finding in contrast to strains obtained from California wines. Higher molar recoveries of 4-ethylphenol and 4-ethylguaiacol synthesized from p-coumaric and ferulic acids, respectively, were observed in Washington Cabernet Sauvignon and Syrah but not Merlot. This finding suggested that Brettanomyces either (a) utilized vinylphenols formed during processing of some wines or (b) metabolized other unidentified phenolic precursors. None of the strains of Brettanomyces studied metabolized caftaric or p-coutaric acids present in wines from Washington or Oregon.

Separation of acidic compounds and determination of shikimic acid in water extracts of several conifers by HPLC

The plants of Coniferae are rich resources that have been found to be of important medicinal value in recent years. The medicinal importance of pine needles prompted us to carry out phytochemical investigations on it [1]. In the past work, we isolated a variety of active compounds from the needles of Cedrus deodara (Roxb.) Loud [2]. In the present work, four small subclasses of acidic compounds have been isolated from the needles of Cedrus deodara (Roxb.) Loud; these were shikimic acid (1), vanillic acid (2), 3,4-dihydroxybenzoic acid (3), and p-hydroxybenzoic acid (4). Shikimic acid (1) is an important intermediate in the biosynthesis of aromatic amino acids in plants and microorganisms [3–6], which is the starting compound utilized for the manufacture of the drug Oseltamivir [3]. Although most autotrophic organisms produce shikimic acid, the isolation yield is low [7]. Shikimic acid is mostly obtained from the fruits of star anise [8]. Only one Chinese paper reported the determination of shikimic acid in the fruit of Illiciaceae plants by LC with diode-array detection [9]. Mardones et al. reported in 2005 [10] a CZE method for determination of shikimic acid in red wines. Garcia Romero et al. [11] described the LC method for the determination of organic acids in grape musts and vinegars. Fang et al. [12] characterized the phenolic constituents in dried plums by LC-MS/MS, and Bylund et al. [13] analyzed the organic acids in natural waters by tandem mass spectrometry. In the present work, we developed a simple and highly precise RP-HPLC method for the analysis of the bioactive molecules of shikimic acid in seven different conifers, viz. Cedrus deodara (Roxb.) Loud, Platycladus orientalis (Linn.) Franco, Pinus massoniana Lamb., Picea crassifolia Kom., Pinus tabulaeformis Carr., Juniperus chensis L., and Sabinacentrasiatica Kom. The method can also be used for quality control and standardization of the species and to identify the species used in a formulation. Pine leaves and branches of seven different conifers were obtained from Gansu Province in northwest China. The samples were identified by Prof. Fujiang He (Gansu Academy of Medical Science, Lanzhou, China). The specimens were authenticated and a voucher specimen of each (YKY0915) was deposited in the Herbarium. The pine needles of Cedrus deodara (3.5 kg) were extracted with 95% ethanol (10 times volume) twice to afford the ethanol extract (390 g), which was suspended in water and extracted with petroleum ether, ethyl acetate, and n-butanol, separately. The n-butanol extract (130 g) was chromatographed over Diaion HP-20 with H2O containing increasing amounts of MeOH. The 20% MeOH eluate (3.4 g) was chromatographed on Toyopearl HW-40 (coarse grade) developing with 20% MeOH 50% MeOH. The 20% MeOH eluate (1.5 g) was rechromatographed on silica gel to yield compound 1 (46 mg), compound 2 (11 mg), compound 3 (16 mg), and compound 4 (13 mg). Samples of air-dried (45–55 C) powdered pine leaves from the seven different conifer species (1.0 g) were sonicated in 100 mL of water for 20 min followed by centrifugation for 15 min at 3500 rpm. The clear supernatant solution was transferred to a 100 mL volumetric flask. The procedure was repeated thrice and the respective supernatants combined. The final volume was adjusted to 100 mL with water and mixed thoroughly. Quantitative analysis of shikimic acid by HPLC with UV detection showed that the amounts of shikimic acid were largest in Cedrus deodara (Roxb.) Loud. The mobile phase was methanol containing aqueous phosphoric acid (pH 3); the amount of the latter component was 90%. The flow rate was 1.0 mL·min–1. The results are summarized in Table 1.

Tartaric acid in red wine as one of the key factors to induce superconductivity in FeTe0.8S0.2

We investigated the key factor of superconductivity in FeTe1−xSx induced by alcoholic beverages. To understand the reason why red wine shows larger shielding volume fraction than the other alcoholic beverages, the red wine dependence of superconductivity was performed. All the samples heated in red wine made from different grapes shows large shielding volume fraction compared with the samples heated in water and other alcoholic beverages. The shielding volume fraction of the red wine samples is proportional to the concentration of tartaric acid. We found that tartaric acid is one of the key factors to induce superconductivity in FeTe1−xSx.

Determination of phenolic composition and antioxidant capacity of native red wines by high performance liquid chromatography and spectrophotometric methods

A reversed-phase high performance chromatographic method for simultaneous determination of 14 phenolic compounds in native red wines was developed in this study. The identified compounds contained gallic acid, (+)-catechin, 3,4-dihydroxybenzoic acid, chlorogenic acid, (−)-epicatechin, 4-hydroxybenzoic acid, syringic acid, caffeic acid, p-coumaric acid, rutin, resveratrol, myricetin, quercetin and kaempferol. The method includes liquid–liquid extraction of acidic pH with ethylacetate. The analysis used a Zorbax Eclipse XDB-C18 column (5μm, 4.6mm×250mm). The chromatographic separation of these compounds performed in a single run by using the mobile phase gradient elution of methanol water mixture (% 0.2 formic acid) at room temperature, with flow rate at 1mL/min. Detection was carried out by UV–vis and fluorescence detector. Each analysis required an equilibration period of 10min and a run time of 14min for completion. The optimized chromatographic method was carefully validated for precision and accuracy. Our findings indicated that the developed HPLC method was precise, accurate, specific and sensitive for simultaneous determination of phenolic compounds. Consequently, the described method was applied to the analysis of six wines from Malatya and Elazığ. Gallic acid was dominant phenolic acid in red wines. (+)-catechin, (−)-epicatechin and p-coumaric acid were the next most abundant phenolics. The highest level of trans-resveratrol among the red wines was found Buzbağı (Bogazkere–Öküzgözü). The red wines were analyzed for total polyphenol content (TP) by Folin–Ciocalteu (FC) method, using gallic acid as standard. Antioxidant activities (AA) of the red wines were measured using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. There was a very high correlation between AA and TP in all of the wines tested.

Electrochemical behaviour and antioxidant capacity of anthocyanins from Chilean red wine, grape and raspberry

abstract The anthocyanin fractions were extracted from Cabernet Sauvignon red wine, skins of Vitis vinifera grapesand raspberry fruits (Rubus idaeus). In red wine extract, 16 anthocyanins were identified, malvidin-3-O-glucoside being the main anthocyanin, which comprised 53.6% of the total anthocyanin in grape extract.Raspberry extract contained mainly delphinidin-3-O-glucoside and cyanidin-3-O-glucoside. The antiox-idant capacity of the extracts was assayed by electrochemical methods. Best resolution of the oxidationpeaks for the extracts and diluted wine was obtained by pulse differential voltammetry. The wine diluted20 presented values of P1 (443 mV) and P2 (676 mV) similar to those corresponding to wine extract,and to the anthocyanin malvidin-3-O-glucoside. The antioxidant capacity of anthocyanins in extractsof wine, grape skin and raspberry fruit was also determined by the Trolox equivalent antioxidant capacity(TEAC) method. 2009 Elsevier Ltd. All rights reserved. 1. IntroductionRed wine is a complex system which contains a large variety ofphenolic compounds, such as flavonols, flavan-3-ols, anthocyaninsand phenolic acids. Anthocyanins are extracted from red grapesand are largely responsible for the colour exhibited by red wine;they play an important role in the antioxidant activity of red wine(Zoecklein, Fugelsang, Gump, & Nury, 2001). In red wine, anthocya-ninsinteractwithphenolicscompounds,pyruvicacidandacetalde-hyde to give new pigments (Francia-Aricha, Guerra, Rivas-Gonzalo,SFulcrand,Bernabdeljalil,Rigaud,Cheynier,M Mateus, Silva, Vercauteren, & De Feitas, 2001).The antioxidative capacity of anthocyanin was studied by differentchemical methods. The Folin–Ciocalteu method, the oxygen radicalabsorbancecapacity(ORAC)assayandtheTroloxequivalentantiox-idantcapacity(TEAC)assayarethemostconsideredmethods(Prior,Wu, & Schaich, 2005). Kilmartin and Hsu (2001) developed anelectrochemical method for the characterization of the antioxidantproperties of wine and wine phenolics. Recently, Janeiro andOliveira Brett (2007) studied the redox behaviour of anthocyaninsby voltammetric techniques, they found that all the phenolichydroxylgroupscanbeelectrochemicallyoxidized.DaSilva,RamosStradiotto,andOliveira(2008)developedamethodforthedetermi-nation of caffeic acid in red wine by differential pulse voltammetry.Zienlin´ska, Nagels, and Piskula (2008) determined the antioxidantcapacity of quercetin and its glycosides of onion by cyclic voltam-metry. Ghiselli, Nardini, Baldi, and Scaccini (1998) reported thatamong the red wine components, anthocyanins were the mosteffectiveinscavengingreactiveoxygenspecies(ROS)andinhibitinglipoprotein oxidation. Anthocyanins comprise around 70% of thetotalphenolsofItalianredwine.Inthisworkweevaluatedtheelec-trochemical behaviour of Chilean Cabernet Sauvignon red wine,Vitis vinifera grape and raspberry anthocyanin extracts in a modelwine solution at pH 3.6, and in acetate buffer.2. Materials and methods2.1. MaterialsCabernet Sauvignon red wine vintage 2005 and V. viniferagrapes were supplied by a local producer. Mature raspberry fruits(Rubus idaeus) were purchased in the local market. All the solventswere reagent grade and/or HPLC grade (Merck, Darmstadt,Germany), all the chemicals were reagent grade (Sigma, St. Louis,MO, USA).2.2. HPLC analysisFor the high performance liquid chromatography (HPLC) analy-sis a Waters 600 HPLC chromatograph (Waters, Mildford, MA, USA)equipped with a Waters 2990 diode array detector, and a