Juan Cacho

Quantitative determination of the odorants of young red wines from different grape varieties.

Fifty-two young monovarietal red wines made with Grenache (17 samples), Tempranillo (11 samples), Cabernet Sauvignon (12 samples) and Merlot (12 samples) grapes have been analysed by HRGC–MS to obtain quantitative data on 47 odorants previously identified as potential aroma contributors by olfactometric techniques. Thirty-three odorants were present in the wines at concentrations higher than their corresponding odour thresholds. These include ethyl octanoate, β-damascenone, ethyl hexanoate, isovaleric acid and isoamyl acetate as the most important, which together with isoamyl and β-phenylethyl alcohols, fatty acids, 2,3-butanedione and ethyl butyrate are always found at concentrations higher than their odour thresholds. In some cases the ethyl esters of isobutyric and isovaleric acids, β-ionone, methionol, isobutyric acid, ethyl cinnamate, ethyl dihydrocinnamate, γ-nonalactone, eugenol, c-3-hexanol, geraniol, guaiacol, 3-isobutyl-2-methoxypyrazine, 4-ethylguaiacol, acetoin and t-whiskylactone were at a concentration high enough to be odour-active. There were 30 compounds that were found to differ significantly between varieties. These include 3-isobutyl-2-methoxypyrazine, isoamyl acetate, isovaleric acid, ethyl isobutyrate, ethyl isovalerate, fusel alcohols, c-3-hexenol, methionol, eugenol, guaiacol and γ-nonalactone. © 2000 Society of Chemical Industry

Determination of minor and trace volatile compounds in wine by solid-phase extraction and gas chromatography with mass spectrometric detection

A new method for the quantitative determination of important wine odorants has been developed. The wine (50 ml) is extracted in a 200 mg solid-phase extraction (SPE) cartridge filled with Lichrolut-EN resins from Merck. The elution is carried out with 1.3 ml of dichloromethane. These extracts are directly analyzed by GC-Ion Trap-MS without further concentration. Twenty-seven important wine odorants, such as volatile phenols, vanillin derivatives, aliphatic lactones, nor-isoprenoids, minor esters and terpenols, can be quantitatively determined in a single gas chromatography-mass spectrometry (GC-MS) run. The recoveries in the SPE isolation are in good agreement with those expected from the calculation of breakthrough volumes from solid-liquid distribution coefficients and are higher than 90%, except for guaiacol, vanillin, 2,6-dimethoxyphenol and 4-vinylphenol. In most cases, precision is below 10%. Method linearity is satisfactory, with r2 higher than 0.99 in all cases. The analysis of spiked samples has shown that there is good agreement between the real mass of compound added to the wine and that determined by analysis. In all cases detection limits are below the odor detection threshold of the compounds, and the calibrated interval covers the natural range of occurrence of the compounds in wine.

Fast analysis of important wine volatile compounds Development and validation of a new method based on gas chromatographic-flame ionisation detection analysis of dichloromethane microextracts

A method for the simultaneous determination of major (10-200 mg/l) and minor (0.1-10 mg/l) volatile compounds from wine has been optimised and validated. A 3-ml volume of wine is diluted with water (7 ml), salted with 4.5 g of ammonium sulfate and extracted with 0.2 ml of dichloromethane. The extract is injected in the split mode in a GC system, separated on a Carbowax 20M capillary column and detected by flame ionisation detection. Volatiles from wine are divided into four groups according to their behaviour in the extraction, and a specific internal standard has been selected for each group. The method allows satisfactory determination of more than 30 volatile compounds of wine. Compounds analysed include acetaldehyde, diacetyl, acetoine (3-hydroxy butanone), fusel alcohols and their acetates, and fatty acids and their ethyl esters. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine and extends from at least one magnitude order to more than two, with typical r2 between 0.9938 and 0.9998. Reproducibility ranges from 3.1 to 10% (as RSD) with 5.5% as the average. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance.

Identification of impact odorants of young red wines made with Merlot, Cabernet Sauvignon and Grenache grape varieties: a comparative study

An Aroma Extract Dilution Analysis (AEDA) has been carried out on three monovarietal young red wines plus a mixture of wines aged one year. The aromograms contain 85 odour-active regions classified in four categories of intensity. The 11 most powerful odorants, 14 out of the 17 second-most powerful, and 34 of the rest could be identified using a HPLC prefractionation method and standard HRGC-MS-olfactometric techniques. The most active odorants of the monovarietal wines were isoamyl and β-phenylethyl alcohols, the ethyl esters of butyric, isobutyric, 2-methyl butyric and hexanoic acids, γ-nonalactone and eugenol. Some others worth mentioning are ethyl isovalerate, isoamyl acetate, hexanol, c-3-hexenol, linalool, geraniol, guaiacol, ethyl cinnamate, ethyl dihydrocinnamate, β-damascenone, δ-decalactone and wine lactone. Compounds with less aromatic intensity but also present in some of the wines were sotolon, isopropyl- and isobutylmethoxypyrazines and 4-mercapto-4-methylpentan-2-one. Data show that there are no impact compounds characteristic of only one variety, and that differences between varieties are quantitative rather than qualitative. © 1999 Society of Chemical Industry

Sensory and chemical changes of young white wines stored under oxygen. An assessment of the role played by aldehydes and some other important odorants

Abstract The aroma of young white wines altered by oxygen was described by a sensory panel which defined the terms: cooked vegetables, liquor, woody, cider and pungent. Twenty-seven young white wines stored under oxygen for 1 week were analyzed by the sensory panel and were further analyzed by gas chromatography (GC)-Ion trap mass spectrometry (MS) to determine their contents in hexanal, 4-hydroxy-4-methylpentanone, 2-nonanone, 2-buthoxyethanol, t -2-octenal, 1-octen-3-ol, furfural and 5-methylfurfural, benzaldehyde, t -2-nonenal and eugenol. The degrees of aroma degradation induced by oxidation and the acetaldehyde concentration of the wines were measured before and after the oxidation process. The sensory analysis showed that wine aroma degradation is primarily caused by the appearance of a cooked-vegetable odour nuance. The acetaldehyde content of the wines did not vary significantly during the oxidation process, and thereby, cannot be related to the appearance of any of the aroma nuances. Regression data confirm the important role played by eugenol in the woody aromatic nuance, but suggest that important odorants, responsible for the other aromatic nuances, remain unidentified. Some of the compounds analyzed may be used as chemical markers for wine oxidative deterioration. The cooked-vegetable odour nuance can be satisfactorily predicted with quantitative measurements of t -2-nonenal, eugenol, benzaldehyde and furfural.

The aroma of Grenache red wine: hierarchy and nature of its main odorants

A young Grenache red wine from 1995 harvest was continuously extracted with Freon-11 and the extract cleaned up with aqueous NaHCO3 in order to remove fatty acids. An Aroma Extract Dilution Analysis was carried out with that extract in a Carbowax 20M capillary column with simultaneous MS and olfactometric detections. The AEDA analysis showed that there are 43 flavour active regions in the chromatogram whose aromatic intensities ranged from less than 16 to more than 1000 arbitrary flavour dilution coefficients. To isolate the odorants, the extract was further washed with propylglycol, concentrated, and then fractionated by normal phase HPLC with UV detection at 220 nm in order to obtain 29 fractions. All the fractions were concentrated and analysed in the same HRGC-MS-olfactometric system in which the AEDA experiment was performed. The strategy allowed to isolate most of the odorants, and 30 of them, among which were the most important, could be clearly identified. Some others could not be identified but their mass spectra are given. Among the most important odorants there are some well known fermentation esters but, surprisingly, the role played by some minor esters, such as the ethyl esters of isobutyric, isovaleric and 2-methylbutyric acids, seems to be very important. Equally important could be the role played by some volatile phenols, terpenols, lactones and some nor-isoprenoids.

Quantitative determination of sotolon, maltol and free furaneol in wine by solid-phase extraction and gas chromatography–ion-trap mass spectrometry

A method for the analytical determination of sotolon [4,5-dimethyl-3-hydroxy-2(5H)-furanone], maltol [3-hydroxy-2-methyl-4H-pyran-4-one] and free furaneol [2,5-dimethyl-4-hydroxy-3(2H)-furanone] in wine has been developed. The analytes are extracted from 50 ml of wine in a solid-phase extraction cartridge filled with 800 mg of LiChrolut EN resins. Interferences are removed with 15 ml of a pentane-dichloromethane (20:1) solution, and analytes are recovered with 6 ml of dichloromethane. The extract is concentrated up to 0.1 ml and analyzed by GC-ion trap MS. Maltol and sotolon were determined by selected ion storage of ions in the m/z ranges 120-153 and 79-95, using the ions m/z 126 and 83 for quantitation, respectively. Furaneol was determined by non-resonant fragmentation of the m/z 128 mother ion and subsequent analysis of the m/z 81 ion. The detection limits of the method are in all cases between 0.5 and 1 microg l(-1), well below the olfactory thresholds of the compounds. The precision of the method is in the 4-5% range for levels in wine around 20 microg l(-1). Linearity holds at least up to 400 microg l(-1), and is satisfactory in all cases. The recoveries of maltol and sotolon are constant (70 and 64%, respectively) and do not depend on the type of wine. On the contrary, in the case of furaneol, red wines show constant and high recoveries (97%), while the recoveries on white wines range between 30 and 80%. Different experiments showed that this behavior is probably due to the existence of complexes formed between furaneol and sulphur dioxide or catechols. Sensory experiments confirmed that the complexed forms found in white wines are not perceived by orthonasal olfaction, and that the furaneol determined by the method can be considered as the free and odor-active fraction.

Modeling quality of premium spanish red wines from gas chromatography-olfactometry data.

The aroma compositions of 25 premium Spanish red wines have been screened by quantitative gas chromatography-olfactometry and have been related to the quality scores of the wines. The study has shown that up to 65 odorants can be present in the aroma profiles of those wines, 32 of which have been detected in less than half of the samples. One new odorant is reported for the first time in wine [(Z)-2-nonenal], and only 11 odorants, most of them weak and infrequent, remain unknown. Quality was not positively correlated with any single compound or with any olfactometric vector built by the summation of odorants with similar odors. However, an olfactometric vector built by the summation of the olfactometric scores of defective odorants, such as 2-methoxy-3,5-dimethylpyrazine, 4-ethylphenol, 3-ethylphenol, 2,4,6-trichloroanisole, and o-cresol was significant and negatively related to quality. Quality could be satisfactorily explained by a simple partial least-squares model (79% explained variance in cross-validation) with just three X-variables: the aforementioned defective vector, a second vector grouping 9 other compounds with negative aroma nuances, and the fruity vector, grouping 15 compounds with fruit-sweet descriptors. This result shows that the quality of these red wines is primarily related to the presence of defective or negative odorants, and secondarily to the presence of a relatively large number of fruit-sweet odorants. Remarkably, only in a few low-quality samples could defective aroma nuances be detected, which suggests that defective and negative odorants exert a strong aroma suppression effect on fruity aroma.

Quality and Aromatic Sensory Descriptors (Mainly Fresh and Dry Fruit Character) of Spanish Red Wines can be Predicted from their Aroma-Active Chemical Composition

A satisfactory model explaining quality could be built in a set of 25 high quality Spanish red wines, by aroma-active chemical composition. The quality of the wines was positively correlated with the wine content in fruity esters, acids, enolones, and wood derived compounds, and negatively with phenylacetaldehyde, acetic acid, methional, and 4-ethylphenol. Wine fruitiness was demonstrated to be positively related not only to the wine content on fruity esters and enolones, but to wine volatile fatty acids. Fruitiness is strongly suppressed by 4-ethylphenol, acetic acid, phenylacetaldehyde, and methional, this involved in the perception of dry-fruit notes. Sensory effects were more intense in the presence of β-damascenone and β-ionone. A satisfactory model explaining animal notes could be built. Finally, the vegetal character of this set of wines could be related to the combined effect of dimethylsulfide (DMS), 1-hexanol, and methanethiol.

HPLC-DAD methodology for the quantification of organic acids, furans and polyphenols by direct injection of wine samples.

This article proposes a simple and sensitive HPLC method with photo-diode array detection for the analysis of organic acids, monomeric polyphenols and furanic compounds in wine samples by direct injection. The chromatographic separation of 8 organic acids, 2 furans and 22 phenolic compounds was carried out with a buffered solution (pH 2.70) and acetonitrile as mobile phases and a difunctionally bonded C18 stationary phase, Atlantis dC18 (250x4.6 mm, 5 mum) column. The elution was performed in 12 min for the organic acids and in 60 min for the phenolic compounds, including phenolic acids, stilbenes and flavonoids. Target compounds were detected at 210 nm (organic acids, flavan-3-ols and benzoic acids), 254 nm (ellagic acid), 280 nm (furans and cinnamic acid), 315 nm (hydroxycinnamic acids and trans-resveratrol) and 360 nm (flavonoids). The RSD for the repeatability test (n=5) of peak area and retention times were below 3.1 and 0.3%, respectively, for phenolics and below 1.0 and 0.2% for organic acids. The RSDs expressing the reproducibility of the method were higher than for the repeatability results but all below 9.0%. Method accuracy was evaluated by the recovery results, with averaged values between 80 and 104% for polyphenols and 97-105% for organic acids. The calibration curves, obtained by triplicate injection of standard solutions, showed good linearity with regression coefficients higher than 0.9982 for polyphenols and 0.9997 for organic acids. The LOD was in the range of 0.07-0.49 mg/L for polyphenols (cinnamic and gallic acids, respectively) and 0.001-0.046 g/L for organic acids (oxalic and lactic acids, respectively). The method was successfully used to measure and assess the polyphenolic fingerprint and organic acids profile of red, white, rosé and fortified wines.