Red Wine Aroma Research Articles

Determination of volatile phenols in red wines by dispersive liquid–liquid microextraction and gas chromatography–mass spectrometry detection

A new method was developed for analysing 4-ethylguaiacol and 4-ethylphenol in the aroma of red wines using dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry detection (GC–MS). Parameters such as extraction solvent, sample volume and disperser solvent were studied and optimised to obtain the best extraction results with the minimum interference from other substances, thus giving clean chromatograms. The response linearity was studied in the usual concentration ranges of analytes in wines (50–1500 μg/L). Repeatability and reproducibility of this method were lower than 5% for both volatile phenols. Limits of detection and limits of quantification were also determined, and the values found were 28 and 95 μg/L for 4-ethylguaiacol and 44 and 147 μg/L for 4-ethylphenol, respectively. This new method has been used for the determination of the volatile phenols concentration in different samples of Tannat wine affected by Brettanomyces contamination.

Which Impact for β-Damascenone on Red Wines Aroma?

beta-Damascenone, a C-13 norisoprenoid compound, is usually presented as an impact odorant in red wines. Its direct contribution to their aroma was investigated. Both free beta-damascenone and beta-damascenone precursors were isolated from various French red wines and then analyzed by gas chromatography-mass spectrometry, revealing concentrations in the vicinity of 1 and 2 microg/L for free compounds and both forms, respectively. Gas chromatography-olfactometry analyses were also performed on dilutions of both red wine extracts and pure beta-damascenone. The very low detection threshold in olfactometry for this compound explains why it is found at the highest dilution factor in aroma extract dilution analysis methods. Moreover, determination of beta-damascenone's odor thresholds confirmed the huge importance of the matrix: beta-Damascenone is characterized by a very low perception threshold in hydroalcoholic solution as compared to red wine, where it is over 1000-fold higher. In hydroalcoholic solution, beta-damascenone enhanced fruity notes of ethyl cinnamate and caproate and masked the herbaceous aroma of IBMP. Globally, these results suggested that beta-damascenone has more an indirect than a direct impact on red wine aroma.

Prediction of aged red wine aroma properties from aroma chemical composition. Partial least squares regression models.

Partial least squares regression (PLSR) models able to predict some of the wine aroma nuances from its chemical composition have been developed. The aromatic sensory characteristics of 57 Spanish aged red wines were determined by 51 experts from the wine industry. The individual descriptions given by the experts were recorded, and the frequency with which a sensory term was used to define a given wine was taken as a measurement of its intensity. The aromatic chemical composition of the wines was determined by already published gas chromatography (GC)-flame ionization detector and GC-mass spectrometry methods. In the whole, 69 odorants were analyzed. Both matrixes, the sensory and chemical data, were simplified by grouping and rearranging correlated sensory terms or chemical compounds and by the exclusion of secondary aroma terms or of weak aroma chemicals. Finally, models were developed for 18 sensory terms and 27 chemicals or groups of chemicals. Satisfactory models, explaining more than 45% of the original variance, could be found for nine of the most important sensory terms (wood-vanillin-cinnamon, animal-leather-phenolic, toasted-coffee, old wood-reduction, vegetal-pepper, raisin-flowery, sweet-candy-cacao, fruity, and berry fruit). For this set of terms, the correlation coefficients between the measured and predicted Y (determined by cross-validation) ranged from 0.62 to 0.81. Models confirmed the existence of complex multivariate relationships between chemicals and odors. In general, pleasant descriptors were positively correlated to chemicals with pleasant aroma, such as vanillin, beta damascenone, or (E)-beta-methyl-gamma-octalactone, and negatively correlated to compounds showing less favorable odor properties, such as 4-ethyl and vinyl phenols, 3-(methylthio)-1-propanol, or phenylacetaldehyde.

Determination of 4-ethylguaiacol and 4-ethylphenol in red wines using headspace-solid-phase microextraction-gas chromatography

A method for analysing 4-ethylguaiacol and 4-ethylphenol in the aroma of red wines using headspace-solid-phase microextraction is presented. The fibres used were coated with 100 μm of polydimethylsiloxane. Parameters like ionic strength, agitation of the sample, sample volume, temperature of the sample and adsorption/desorption times were studied and optimised to obtain the best extraction results. The linearity of the response was studied in the usual concentration ranges in wines (4-ethylguaiacol, 40–400 μg/l; 4-ethylphenol, 200–1800 μg/l). Repeatability of the method was determined, and the relative standard deviation was about 10%. Limits of detection and limits of quantification were also determined, and the values found were 1 and 5 μg/l for 4-ethylguaiacol and 2 and 5 μg/l for 4-ethylphenol, respectively. All these values were under the sensory thresholds established for these volatile phenols. The presence of interferences due to the matrix composition implies the use of the standard addition technique for both compounds quantification.

Effect of maturation in small oak casks on the volatility of red wine aroma compounds

Wood maturation of red wine produces complex interactions between oak extracted compounds and pre-existing components in wine. Wood contributes with some aroma volatiles; but the whole volatile fraction, including the volatiles extracted from grape or produced during fermentation, could be involved in interactions with the non-volatile fraction. Samples of red wine with increasing time of wood contact, matured in 25 l casks of new American oak, were analysed on their volatile composition both in solution and headspace, and phenolic components. There was an increase of acetic acid and acetate esters as the time of wood contact increased. On the other hand, ethyl esters decreased as the time in wood increased. Some volatiles showed different behaviour when comparing their relationship between headspace and solution from two different casks, even though they were treated as replicates. This different evolution among casks was also consistent with different evolution of phenolic compounds, suggesting that there was an interaction among the volatile fraction and phenolic components.

Effect of macerating enzymes on red wine aroma at laboratory scale: exogenous addition or expression by transgenic wine yeasts.

The effects of a Trichoderma longibrachiatum endoglucanase and an Aspergillus nidulans endoxylanase on the concentration of free and bound volatiles, color, and phenolics during maceration in red wine vinification has been studied. Two different approaches have been considered for the utilization of these enzymes: (i) direct addition of the enzymes to must and (ii) inoculation of must with recombinant wine yeasts overexpressing these activities. An experimental design based on a Taguchi orthogonal array was carried out in order to evaluate the effects of the enzymatic treatments. The data show that these fungal activities are able to increase the concentrations of free and glycosidically bound flavor compounds, color, and phenolics to similar or greater extents as compared to a commercial pectolytic enzyme preparation. The effects of the two different ways of addition of the enzymes were not always equivalent. These enzymes could be considered to be of potential application in the red wine maceration process.

Comparison of polyphenols and aroma in red wines from Portuguese mainland versus Azores Islands

trans-Resveratrol ( trans-3,5,4′.trihydroxystilbene), piceid (resveratrol 3-O-β-D-glucopyranoside), together with their isomers and quercetin were measured in red wines from cultivars grown in Portuguese mainland and Azores Islands. Crude hydroxystilbenes and quercetin were extracted by solid-phase extraction-C 18 cartridges, and eluted with ethyl acetate. Recoveries of added trans-resveratrol and quercetin were between 90.2 to 101% (mean 96.8%) and between 95.2 and 97.6% (mean 96.2%), respectively. The precision measured by coefficients of variation (overall mean) ranged from 1.8 to 3.3%, and the calibration curves were linear with the mean correlation coefficients of 0.9997 and 0.9978 for trans-resveratrol and quercetin, respectively. The wine polyphenolic compounds were separated by reverse-phase C18 HPLC column and identified by UV fast scanning, retention times and HPLC/MS. The average content of total stilbenes was 4.75 and 6.33 mg/l, that of quercetin was 4.38 and 5.57 mg/l, and the trans/cis ratio was 8.32 and 10.89 for piceid and 5.2 and 4.09 for resveratrol in Portuguese mainland and Azorean wines, respectively. The Azorean wine (Basalto) was notable in having the highest trans-resveratrol concentration. The aroma profile of red wine samples from different regions were compared using SPME/GC-MS headspace methodology.

Red wine aroma: Identification of headspace constituents

AbstractGas chromatrography–mass spectrometry, using the special sampling technique described previously, revealed 39 components in the headspace of red wine. Nineteen of the components have not previously been detected by headspace techniques and two are reported for the first time in wine aroma: dehydroionene (1,1,6‐trimethyl‐1,2‐dihydronaphthalene) and 2‐(ehtoxymethyl)furan. The latter is one of the compounds formed on ageing.