Measurement of dissolved oxygen during red wines tank aging with chips and micro-oxygenation

Nowadays, micro-oxygenation is a very important technique used in aging wines in order to improve their characteristics. The techniques of wine tank aging imply the use of small doses of oxygen and the addition of wood pieces of oak to the wine. Considering the low dissolved oxygen (DO) levels used by micro-oxygenation technique it is necessary to choose the appropriate measurement principle to apply the precise oxygen dosage in wine at any time, in order to assure its correct assimilation. This knowledge will allow the oenologist to control and run the wine aging correctly.This work is a thorough revision of DO measurement main technologies applied to oenology. It describes the strengths and weaknesses of each of them, and draws a comparison of their workings in wine measurement. Both, the traditional systems by electrochemical probes, and the newest photoluminescence-based probes have been used. These probes adapted to red wines ageing study are then compared.This paper also details the first results of the dissolved oxygen content evolution in red wines during a traditional and alternative tank aging. Samples have been treated by three different ageing systems: oak barrels, stainless-steel tanks with small oak wood pieces (chips) and with bigger oak pieces (staves) with low micro-oxygenation levels. French and American oak barrels manufactured by the same cooperage have been used.     

Identification, amounts, and kinetics of extraction of C-glucosidic ellagitannins during wine aging in oak barrels or in stainless steel tanks with oak chips

The C-glucosidic ellagitannins are found in wine as a result of its aging in oak barrels or in stainless steel tanks with oak chips. Once dissolved in this slightly acidic solution, the C-glucosidic ellagitannins vescalagin can react with nucleophilic entities present in red wine, such as ethanol, catechin, and epicatechin, to generate condensed hybrid products such as the β-1-O-ethylvescalagin and the flavano-ellagitannins (acutissimin A/B and epiacutissimin A/B), respectively. During this study, we first monitored the extraction kinetic and the evolution of the eight major oak-derived C-glucosidic ellagitannins in red wines aged in oak barrels or in stainless steel tank with oak chips. Their extraction rates appeared to be faster during red wine aging in stainless steel tanks with oak chips. However, their overall concentrations in wines were found higher in the wine aged in barrels. The formation rates of the vescalagin-coupled derivatives were also estimated for the first time under both red wine aging conditions (i.e., oak barrels or stainless steel tanks with oak chips). As observed for the oak-native C-glucosidic ellagitannins, the concentrations of these vescalagin derivatives were higher in the red wine aged in oak barrels than in stainless steel tanks with oak chips. Despite these differences, their relative composition was similar under both red wine aging conditions. Finally, the impact of the oak chips size and toasting level on the C-glucosidic ellagitannins concentration in wine was also investigated.     

Identification,amounts, and kinetics of extraction of <Emphasis Type="Italic">C</Emphasis>-glucosidic ellagitannins during wine aging in oak barrels or in stainless steel tanks with oak chips

The C-glucosidic ellagitannins are found in wine as a result of its aging in oak barrels or in stainless steel tanks with oak chips. Once dissolved in this slightly acidic solution, the C-glucosidic ellagitannins vescalagin can react with nucleophilic entities present in red wine, such as ethanol, catechin, and epicatechin, to generate condensed hybrid products such as the β-1-O-ethylvescalagin and the flavano-ellagitannins (acutissimin A/B and epiacutissimin A/B), respectively. During this study, we first monitored the extraction kinetic and the evolution of the eight major oak-derived C-glucosidic ellagitannins in red wines aged in oak barrels or in stainless steel tank with oak chips. Their extraction rates appeared to be faster during red wine aging in stainless steel tanks with oak chips. However, their overall concentrations in wines were found higher in the wine aged in barrels. The formation rates of the vescalagin-coupled derivatives were also estimated for the first time under both red wine aging conditions (i.e., oak barrels or stainless steel tanks with oak chips). As observed for the oak-native C-glucosidic ellagitannins, the concentrations of these vescalagin derivatives were higher in the red wine aged in oak barrels than in stainless steel tanks with oak chips. Despite these differences, their relative composition was similar under both red wine aging conditions. Finally, the impact of the oak chips size and toasting level on the C-glucosidic ellagitannins concentration in wine was also investigated.     

Analysis for low molecular weight phenolic compounds in a red wine aged in oak chips

The evolution of low molecular weight polyphenols in a red wine aging in different systems (barrels, oak chips and oak staves) made of different oak species was studied. All were placed under the same aging conditions in a wine cellar participating the Cigales Appellation of Origin programme (Spain). The wine aged in contact with oak chips experienced a quicker aging and loss of certain compounds, and a greater number of polymerisations than the wine aged in barrels. The discriminant analysis showed that samples of the same source wine aged in barrels, oak chips and oak staves tended to group together according to the aging system when wood from different botanical species is used (American, French or Hungarian).     

Changes in wine volatile compounds of varietal wines during ageing in wood barrels

Twelve single-variety wines were aged in new American oak barrels. A control wine of each variety without ageing in wood was also studied. The volatile aroma composition of these wines was analysed after the following combinations of time in wood and time in bottle: 0 months in wood plus 18 months in bottle, 4 months in wood plus 14 months in bottle, 9 months in wood plus 12 months in barrel and 12 months in barrel plus 6 months in bottle.The data obtained were studied by two different multivariate methods: factor analysis by principal components and stepwise linear discriminant analysis. The results obtained showed that the capacity of wine to extract the volatile compounds from the wood depended on the variety of grape used. Furthermore, it was also found that the changes in the volatile composition of the wines induced by the wood ageing were more important during the first 4 months. In addition, the volatile compounds studied allowed to differentiate and correctly classify the wines according to the time they had been in contact with the wood.     

Aging markers from bottled red wine aged with chips, staves and barrels

This paper shows the results of the experiments carried on Spanish red wines aged through alternative as well as traditional oak barrel systems, i.e., chips stainless steel tanks and staves stainless steel tanks, at the same time and under the same conditions.Wine aging through wood pieces is not accepted as an enological practice by the European Union and, in fact, it is considered a fraud. It is, then, of a great interest to identify those parameters able to establish the aging technique that had been used in a wine ready to be consumed. With this idea in mind, the development of the same wine has been studied while aging for 3 years in three different systems.During the first six aging months wines stored with staves obtained characteristics that were halfway between wines treated with chips and those aged in barrels. However, as wood contact period length increased so did the differences between wines stored in traditional and alternative systems (either with staves or chips). These differences grew during the bottling period, so that after a 2-year bottling period wines from the three systems became different enough to tell them apart. Discriminant analysis of the variables studied made it possible to establish these differences. The most meaningful variables were yellow colour component, anthocyanins (cyanidin-3-glucoside, vitisin A and sum of pcoumaryl derivates), vanillin acid, protocachuic aldehyde and epicatechin.     

Application of LC–MS and tristimulus colorimetry to assess the ageing aptitude of Syrah wine in the Condado de Huelva D.O. (Spain), a typical warm climate region

The study of the evolutions of different wine pigment families, copigmentation/polymerisation processes and colour characteristics during the first year of ageing in oak barrel has allowed the assessment of the ageing aptitude of Syrah wines from “Condado de Huelva D.O.”, a warm climate region. A total of 32 anthocyanic pigments were identified, including 14 major compounds from grape and 18 minor derivatives formed during the vinification. The anthocyanin profile changed towards more chemical complexity, being vitisin-like pyranoanthocyanins the predominant minor pigments during the first month of ageing. As wine became older, a progressive increase on the content of 4-vinylcatechin, 4-vinylphenol and 4-vinylcatechol compounds took place. Results showed that copigmentation occurred during the whole process of ageing inducing visual perceptible colour effects. Simultaneously to the copigmentation decrease, the degree of polymerisation increased during ageing, being maximum at 9 months old wines (77%). The colour of wines evolved progressively in a positive way from 3 to 9 months of ageing, becoming darker and with more vivid colour. However, from 9 to 12 months of ageing, the chemical structure of wines was negatively affected resulting in lighter, with more red-orange hues and less vivid colours. The inclusion of the chemical and colorimetric information on the PCA model allows us to reach very good discriminations among the Syrah wines with different wood contact period.     

Quantitative analysis of 4-ethylphenol and 4-ethylguaiacol in red wine

2,3,5,6-[2H4]-4-Ethylphenol (d4-4-ethylphenol) was synthesised for use as an internal standard in a new, rapid and accurate analytical method, employing gas chromatography-mass spectrometry to determine the concentration of the important aroma compounds 4-ethylphenol and 4-ethylguaiacol in red wine. The concentrations of both compounds in wine stored in 44 American and 47 French new and used oak barrels from several suppliers were measured. Wine stored in shaved and refired oak barrels contained up to 85% less 4-ethylphenol and 4-ethylguaiacol than wine stored in normal barrels of the same age that were not shaved. The concentration of 4-ethylphenol found in 61 bottled commercial Australian red wines of various ages ranged from 2 microg/l in a Merlot up to 2660 microg/l in a Shiraz, with a mean concentration of 795 microg/l. 4-Ethylguaiacol was also detected in every red wine analysed, ranging in concentration from 1 microg/l (in a Pinot Noir) up to 437 microg/l (in a Merlot) with a mean concentration of 99 microg/l.     

Differentiation of young red wines based on cultivar and geographical origin with application of chemometrics of principal polyphenolic constituents

Nineteen major polyphenolic phytochemicals including hydroxycinnamate derivatives, flavanols, flavonols, and anthocyanins, were determined in 40 experimental red wines employing HPLC-DAD. All wines analysed were young (non-aged), produced, and stored under identical conditions, in an effort to minimize the effect of oak wood and vinification technology. The data obtained from this examination composed the matrix for the implementation of chemometrics, which aimed at differentiating the wine samples on the basis of cultivar and geographical region of origin. Discriminant analysis performed at a 95% significance level revealed a very satisfactory categorization of the samples both in terms of cultivar and region of origin, thus illustrating the validity of major phenolic phytochemicals for studies pertaining to wine quality and authenticity.     

Application of multi-way analysis to UV–visible spectroscopy,gas chromatography and electronic nose data for wine ageing evaluation

In this study, a multi-way method (Tucker3) was applied to evaluate the performance of an electronic nose for following the ageing of red wines. The odour evaluation carried out with the electronic nose was combined with the quantitative analysis of volatile composition performed by GC–MS, and colour characterisation by UV–visible spectroscopy. Thanks to Tucker3, it was possible to understand connections among data obtained from these three different systems and to estimate the effect of different sources of variability on wine evaluation. In particular, the application of Tucker3 supplied a global visualisation of data structure, which was very informative to understand relationships between sensors responses and chemical composition of wines. The results obtained indicate that the analytical methods employed are useful tools to follow the wine ageing process, to differentiate wine samples according to ageing type (either in barrel or in stainless steel tanks with the addition of small oak wood pieces) and to the origin (French or American) of the oak wood. Finally, it was possible to designate the volatile compounds which play a major role in such a characterisation.     

Comparison of wine aromas with different tannic content aged in French oak barrels

A method has been developed to determine the most significant volatiles of a wine aged in barrels: trans- and cis-whiskylactone, guaiacol, 4-ethylguaiacol, eugenol, 4-ethylphenol, vanillin, furfural and γ-butyrolactone. This method consists in an extraction with dichloromethane, according to classical methods, but emulsion formation is avoided and the later analysis is carried out by thermal desorption-gas chromatography with mass spectrometric detection. This method is quite rapid and gives calibration graphs with linear regression coefficients between 0.97 and 0.99 for each compound and variation coefficients of variation <10%. This method has been applied to three wines with different tannic content (free-run or base wine and two other from base wine by adding both enological tannin and its own press wine) aged 6 months in French oak barrels (Allier). Sensorial analyses were carried out by expert tasters. All results were used in discriminant analyses, but only the lactones and vanillin were necessary to properly classify all the wines according to tannic content.     

Determination of volatile oak compounds in aged wines by multiple headspace solid-phase microextraction and gas chromatography–mass spectrometry (MHS-SPME–GC–MS)

Multiple headspace solid-phase microextraction (MHS-SPME) with gas chromatography–mass spectrometry is proposed for quantification of nine volatile oak compounds in aged wines. These compounds are formed and extracted by wine when it is matured in oak barrels and are responsible for particular organoleptic properties and the high quality of these wines. Some important variables of the extraction process, for example volume of sample and extraction time, were studied. Extraction of 50 μL wine was performed with a divinylbenzene–Carboxen–polydimethylsiloxane fibre at 55 °C for 60 min. For calibration the same conditions were used, except that the wine was substituted by 50 μL of a standard solution in synthetic wine. The linearity, detection limits, and repeatability of the method were determined by use of standard solutions in synthetic wine. Detection limits were between 0.01 and 10 μg L⁻¹ (for eugenol and furfural, respectively) and repeatability, expressed as relative standard deviation, was from 2 to 6%. The method was used to analyse six red wines and the concentrations obtained were statistically compared with those obtained by the standard addition method for the same wines.     

Volatile compounds as markers of ageing in Tempranillo red wines from La Mancha D.O. stored in oak wood barrels

Solid-phase extraction cartridges (SPE)-GC/MS method was used to analyse red wines aromas. The matrix effect was studied with chemicals standard prepared in synthetic wines with water/alcohol solutions (12% ethanol, v/v) following the procedure proposed. The method offers good reproducibility since the relative standard deviations (RSD%) for the volatile compounds levels were less than 9%. This method was used to differentiate the aroma of one hundred mono-varietal young, crianza, reserva and gran reserva La Mancha D.O. wines (cv. Tempranillo) on the basis of oak barrel contact period. Samples were checked at ten time points over 36 months. Sixty important wine odorants, such as volatile phenols, vanillin derivatives, lactones, norisoprenoids, benzene compounds, esters and terpenols, can be quantitatively determined in a single run. Results showed significant quantitative differences in the volatile profiles of wines depending on the length of time in contact with wood, even in wines belonging to the same commercial category. Stepwise multiple linear regression (SMLR) was used to obtain a model that predicted the time of barrel ageing to which wines were submitted in relation with the wine volatile composition. A successful function based on eight compounds with a mean deviation of 0.37 months in the predictions, was obtained.     

Determination of anthocyanins in wine by direct injection liquid chromatography-diode array detection-mass spectrometry and classification of wines using discriminant analysis

A rapid HPLC-diode array detection (DAD) method was developed for the routine analysis of 16 anthocyanins in wine. Direct injection of filtered wine samples followed by selective detection at 520 nm allowed quantitation of these compounds in red wines. The method was linear for malvidin-3-glucoside over the range 5-250ppm, and the limit of detection for this compound was 0.18 ppm. A volatile mobile phase is used, which enables hyphenation to mass spectrometry (MS). With HPLC-MS, a total of 44 pigments could be identified in South African wines. Obtained mass spectra are discussed for a series of representative wine constituents and results are compared with literature references. An attempt was made to differentiate between different cultivars according to the anthocyanin content using stepwise forward linear discriminant analysis (LDA).     

Comparison of high-performance liquid chromatography separation of red wine anthocyanins on a mixed-mode ion-exchange reversed-phase and on a reversed-phase column

Anthocyanins, which confer the characteristic color to red wine, can be used as markers to classify wines according to the grape variety. It is a complex separation that requires very high chromatographic efficiency, especially in the case of aged red wines, due to the formation of pyranoanthocyanins. A coelution between these kinds of compounds can affect the R_ac/coum ratio of aged wines, and might lead to false results when classifying the wine variety. In 2007, the use of a novel mixed-mode ion-exchange reversed-phase column was reported to separate anthocyanins extracted from grapes of Vitis labrusca with different selectivity than C-18 columns. In the present work, the separation of anthocyanins including pyranoanthocyanins in young and aged Cabernet Sauvignon wines and other varieties is evaluated. The most interesting contributions of this research are the different elution order and selectivity obtained for anthocyanins and pyranoanthocyanins (only formed in wine), compared with those observed in C-18 stationary phases. Also interesting is the separation of the polymeric fraction, which elutes as a clearly separated peak at the chromatogram's end. However, a comparison with a high efficiency C-18 column with the same dimensions and particle size demonstrated that the tested mixed-mode column shows broader peaks with a theoretical plate number below 8000, for malvidin-3-glucoside peak, while it can be up to 10 times higher for a high efficiency C-18 column, depending on the column manufacturer. Under the tested conditions, in mixed-mode phase, the analysis time is almost twice that of a C-18 column with the same dimensions and particle size. A mixed-mode phase with increased efficiency should provide an interesting perspective for separation of anthocyanins in wine, due to its improved selectivity, combined with a useful role in a second-dimension separation in preparative anthocyanin chromatography.     

Analysis of several phenolic compounds with potential antioxidant properties in grape extracts and wines by high-performance liquid chromatography-photodiode array detection without sample preparation

A RP-HPLC method that allows the separation of several types of phenolic compounds present in grapes and wines by direct injection of samples, using a binary gradient with solvents free of salts and photodiode array detection is described. Results show that more than 15 different phenolic molecules with antioxidant properties (flavan-3-ols, anthocyanins, cinnamic acid derivatives, flavonol derivatives and trans-resveratrol) may be separated in a single run by direct injection of red wine. The method is also valuable for the analysis of these compounds in white wine and in skins, seeds and pulp extracts of red and white grapes.     

Determination of anthocyanins and related components in red wines by micro- and capillary HPLC

Anthocyanins and derived components of red wines were determined by microHPLC using a 1 mm ID HPLC column coupled on-line with an MS detector equipped with an ESI (ElectroSpray Ionisation) source. The use of microcolumn HPLC greatly enhanced detection performance, allowing direct identification of components present in the fraction. Nineteen anthocyanins were detected. Fifteen were identified, two were tentatively identified, and only the aglycon of the remaining two components was certainly identified. Six anthocyanin-derived pigments, supposedly formed during wine maturation, were also investigated and found in a wine sample. The analysis of red wine anthocyanins was also carried out by injecting a large sample volume onto a 0.32 mm ID HPLC column, using the column focusing technique, in order to decrease the limit of detection and quantification of components present in a very small amounts.     

Isolation and quantification of oligomeric pyranoanthocyanin-flavanol pigments from red wines by combination of column chromatographic techniques

A combination of column chromatography on Toyopearl gel HW-40 (S) and polyamide resin has been developed for the preparative isolation and further determination of pyranoanthocyanins of oligomeric nature formed after reaction between anthocyanins and different flavanols in a complex wine matrix. Polyamide chromatography was found to be exceptionally useful to separate oligomeric pyanoanthocyanins from other classes of wine flavonoids and polymerized pigments into an advanced state of purity for further identification and quantification by HPLC-diode array detector coupled with electrospray ionization mass spectrometry (HPLC-DAD/ESI-MS). Fractionation on Toyopearl gel chromatography allowed the separation of pyranoanthocyanins bearing the same flavanols (catechin, epicatechin and procyanidin dimers) but with different anthocyanin moieties (either acylated or non-acylated in the glucose residue) in order to allow further isolation of individual oligomeric pigments on C18 chromatography. A quantitative procedure for analyzing the major pyranoanthocyanin-flavanol derivatives in different aged wines is proposed for the first time. Results obtained showed good reproducibility and recovery regarding sample pretreatment and quantitative method for all analyzed oligomeric pyranoanthocyanins. The combination of these two chromatographic separations is likely to be applicable to the preparative isolation of other anthocyanin-derived pigments.     

A new class of anthocyanin‐procyanidin condensation products detected in red wine by electrospray ionization multi‐stage mass spectrometry analysis

In our previous work, we have identified, in a model wine solution containing malvidin 3‐glucoside, epicatechin and acetaldehyde, a new condensation product – hydroxylethyl‐malvidin‐3‐glucoside‐ethyl‐epicatechin. The objective of this work was to verify the presence of such new condensation products in red wine. For this purpose, red wine was fractionated into various fractions by column chromatography on LiChroprep RP 18 and on Toyopearl 40 (F). The phenolic composition of each fraction was verified by HPLC‐DAD and direct‐infusion ESI‐MSⁿ analysis. In addition to the well‐known anthocyanins and their acetyl and coumaroyl derivatives, and several direct and indirect anthocyanin‐(epi)catechin condensation products, a new class of pigmented products, namely hydroxyethyl‐anthocyanin‐ethyl‐flavanol compounds, have been detected in red wine. The new class of pigmented products would be expected to be the major pigments responsible for the color of aged red wine. Copyright © 2010 John Wiley & Sons, Ltd.     

High-efficiency high performance liquid chromatographic analysis of red wine anthocyanins

The analysis of anthocyanins in natural products is of significant relevance in recent times due to the recognised health benefits associated with their consumption. In red grapes and wines in particular, anthocyanins are known to contribute important properties to the sensory (colour and taste), anti-oxidant- and ageing characteristics. However, the detailed investigation of the alteration of these compounds during wine ageing is hampered by the challenges associated with the separation of grape-derived anthocyanins and their derived products. High performance liquid chromatography (HPLC) is primarily used for this purpose, often in combination with mass spectrometric (MS) detection, although conventional HPLC methods provide incomplete resolution. We have previously demonstrated how on-column inter-conversion reactions are responsible for poor chromatographic efficiency in the HPLC analysis of anthocyanins, and how an increase in temperature and decrease in particle size may improve the chromatographic performance. In the current contribution an experimental configuration for the high efficiency analysis of anthocyanins is derived using the kinetic plot method (KPM). Further, it is shown how analysis under optimal conditions, in combination with MS detection, delivers much improved separation and identification of red wine anthocyanins and their derived products. This improved analytical performance holds promise for the in-depth investigation of these influential compounds in wine during ageing.