A young white wine that had undergone spontaneous oxidation and showed a strong off-flavor reminiscent of cooked vegetables was demixed by salting out to obtain an ethanolic extract that retained the off-flavor of the wine, as was demonstrated by sensory analysis. This extract, together with a second one obtained from a non-oxidized wine sample, were chromatographed into a reversed-phase HPLC column using a water/ethanol gradient. The column effluents were collected in 14 different fractions that were evaluated for smell. Four fractions were found to differ between oxidized and non-oxidized wine, but only one showed a clear cooked vegetables off-flavor and, when added to a non-oxidized wine, made it significantly more similar to the oxidized wine. The fraction was analyzed by GC-MS-olfactometry, which made it possible to identify methional as the single important odorant of the fraction. The odor threshold of methional in a synthetic wine was found to be 0.5 microg L(-)(1). The analytical determination of methional through GC-FPD in several oxidized and non-oxidized wines showed that, in the former, methional can reach more than 200 Odor Units, whereas in the non-oxidized samples, it was not possible to detect methional. The methional concentration was found to increase in wines spiked with both methionol or methionine, which suggests that it can be formed from direct peroxidation of methionol or via Strecker degradation of methionine mediated, probably, by o-quinones formed during wine oxidation.

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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

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The role played by ethyl esters of fatty acids and by acetates of higher alcohols on the aroma of young wines from neutral grape varieties has been investigated. The statistical methods used have been stepwise linear regression and principal components analysis. Very significant conclusions have been reached. The role played by these compounds depends on the type of wine. In white wines their main role is in the perception of tree fruit and tropical fruit notes. It has been demonstrated that the former notes are linked to ethyl esters, while the latter are linked mainly to acetates of higher alcohols. In rose wines the intensity of tree fruit aroma was correlated with ester content, however no clear conclusion was reached about the role of various compounds on the perception of quality. Finally, in red wines these compounds d o not determine the intensity of fruit aromas, and they only play a modulating role on aroma quality. This indicates that red grape varieties must have other aroma compounds which are responsible for the fruity characteristics of wines.