Valérie Lavigne

Impact of Oxygen Dissolved at Bottling and Transmitted through Closures on the Composition and Sensory Properties of a Sauvignon Blanc Wine during Bottle Storage

This work outlines the results from an investigation to determine the effect of the oxygen dissolved at bottling and the specific oxygen barrier properties of commercially available closures on the composition, color and sensory properties of a Bordeaux Sauvignon Blanc wine during two years of storage. The importance of oxygen for wine development after bottling was also assessed using an airtight bottle ampule. Wines were assessed for the antioxidants (SO(2) and ascorbic acid), varietal thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol), hydrogen sulfide and sotolon content, and color throughout 24 months of storage. In addition, the aroma and palate properties of wines were also assessed. The combination of oxygen dissolved at bottling and the oxygen transferred through closures has a significant effect on Sauvignon Blanc development after bottling. Wines highly exposed to oxygen at bottling and those sealed with a synthetic, Nomacorc classic closure, highly permeable to oxygen, were relatively oxidized in aroma, brown in color, and low in antioxidants and volatile compounds compared to wines sealed with other closures. Conversely, wines sealed under more airtight conditions, bottle ampule and screw cap Saran-tin, have the slowest rate of browning, and displayed the greatest contents of antioxidants and varietal thiols, but also high levels of H(2)S, which were responsible for the reduced dominating character found in these wines, while wines sealed with cork stoppers and screw cap Saranex presented negligible reduced and oxidized characters.

Identification of volatile compounds responsible for prune aroma in prematurely aged red wines.

The premature aging of red Vitis vinifera L. wines is mainly associated with the formation of an intense off-flavor reminiscent of prunes. The compounds responsible for this deterioration in red wine flavor have not previously been identified. Sensory descriptive analysis associated with a gas chromatography-olfactometry (GC-O) technique was first performed to find characteristic odoriferous zones of 15 aged red wines with or without a marked prune aroma. Afterward, high-pressure liquid chromatography, gas chromatography, and multidimensional gas chromatography coupled with mass spectrometry (MDGC-MS) were used to identify the odorants reminiscent of prunes in prematurely aged red wines and in the dried fruit. Three compounds were detected with a strong odor of prunes: gamma-nonalactone, beta-damascenone, and 3-methyl-2,4-nonanedione. The perception threshold of the latter beta-diketone in a model hydroalcoholic solution is 16 ng/L. Identified for the first time in aged red wines, this very powerful volatile compound was also suggested to produce the characteristic prune aroma of prematurely aged red wines. The presence of 3-methyl-2,4-nonanedione was also detected in prunes for the first time.

Changes in the Sotolon Content of Dry White Wines during Barrel and Bottle Aging

GC-MS in electron ionization mode (EI) was used as a simple, sensitive method for assaying sotolon [4,5-dimethyl-3-hydroxy-2(5) H-furanone] in various dry white wines. The impact of barrel-aging conditions, that is, whether yeast lees were present or not, on the formation of sotolon in dry white wines was then studied. The sotolon content was highest in dry white wines aged in new barrels without lees, often exceeding the perception threshold (8 microg/L). These results demonstrated that yeast lees were capable of minimizing the formation of sotolon in dry white wines during aging. The sotolon and oxygen contents of several bottle of the same white wine were also compared 7 years after bottling. At the range of dissolved oxygen concentrations generally measured, between 5 and 100 microg/L, the sotolon content remained below its perception threshold in wine. The perception threshold was exceeded only in wines with oxygen concentrations above 500 microg/L. The presence of dissolved oxygen in the wine samples analyzed also resulted in a decrease in their free sulfur dioxide content.

Identification of a sotolon pathway in dry white wines.

Sotolon (3-hydroxy-4,5-dimethyl-2(5H)-furanone) is a chiral furanone, an aroma compound known to be responsible for premature-aging flavor in dry white wines. Sotolon generally results from mild oxygenation during bottle aging, and until now, its formation pathways had not been elucidated. The ability of the main precursors described in the literature under very different experimental conditions to produce sotolon was tested. In model wine solution maintained at 40 degrees C for 6 months, sotolon was produced by the oxidative degradation of ascorbic acid. By use of GC-MS, 2-ketobutyric acid, produced by the oxidative degradation of the ascorbic acid in the model wine solution, was identified as a potent precursor of sotolon in this pathway. Ascorbic acid is an exogenous compound, added before bottling, but 2-ketobutyric acid was found even in white wines that had not been supplemented. Consequently, this sotolon formation pathway is also valid in white wines with no added ascorbic acid. In addition, we showed that Saccharomyces cerevisiae strains were capable of producing variable concentrations of this ketone during alcoholic fermentation. In model wine solution, certain yeast strains released large quantities of 2-ketobutyric acid, similar to those found in oxidized dry white wines. In view of these results, the role of yeast strains in this premature-aging phenomenon of dry white wines is discussed. Finally, these investigations revealed that one chemical mechanism responsible for the low concentrations of sotolon found in prematurely aged white wines made from various grape varieties was an aldol condensation between 2-ketobutyric acid and acetaldehyde.

Distribution and Organoleptic Impact of Sotolon Enantiomers in Dry White Wines

The enantiomers of sotolon, a flavor compound typical of oxidized white wines, were separated by preparative HPLC to determine their perception thresholds and distribution in wines. The enantiomeric ratios of chiral sotolon were evaluated in several dry white wines using gas chromatography and a chiral column (beta-cyclodextrin) connected to a 2 m precolumn (BP20). The perception threshold of (S)-sotolon (0.8 microg/L) in model wine solution was 100 times lower than that of the (R) form (89 microg/L), indicating that (S)-sotolon contributes to the characteristic aroma of prematurely aged dry white wines. Both enantiomers are detected in white wines. Analysis of commercial dry white wines from various vintages and origins revealed three types of distribution patterns: the racemic form, an excess of R, and an excess of S. The proportions found in these wines may be partially explained by the slow racemization kinetics (20 months) of optically active sotolon.

Determination of 3-methyl-2,4-nonanedione in red wines using methanol chemical ionization ion trap mass spectrometry

A compound associated with oxidized flavor in red wines was recently-identified as 3-methyl-2,4-nonanedione (MND). In order to quantify it, positive chemical ionization (PCI) in an ion trap was studied using conventional liquid reagents such as methanol, acetonitrile, and acetone, as well as non-conventional liquid reagents such as ethyl acetate, diethyl ether, pentane, isohexane, and heptane. Under laboratory conditions, very different response factors were obtained with MND depending on the gas. We also compared the detection limit of conventional CI with hybrid chemical ionization (HCI). Finally, this compound was quantified in red wines by liquid/liquid extraction without any derivatization steps, followed by GC/MS-CI analysis, using methanol as the reagent gas. Coelutions of compounds with the same m/z were checked using methanol-d(4). The method we developed was linear in the 10-300 ng/L range of MND concentrations, with satisfactory repeatability. The detection limit was 4.3 ng/L, over 3 times lower than the olfactory perception threshold of this compound (16 ng/L). The suitability of this method for assaying this diketone in red wine was demonstrated by the analyzing many wines from different vintages.

Study of the contribution of massoia lactone to the aroma of Merlot and Cabernet Sauvignon musts and wines

Organic extracts of musts and red wines marked by dried fruit and cooked fruit aromas were analyzed by gas chromatography coupled to olfactometry and mass spectrometry. Thanks to this analytical approach we identified a fragrant lactone corresponding to an odorant zone reminiscent of coconut and dried figs as 5,6-dihydro-6-pentyl-2H-pyran-2-one (C10 massoia lactone). Using chiral GC-GC-MS, we show that only the (R)-C10 massoia lactone is found in musts and wines. Its detection thresholds were 10µg/L and 11µg/L in must and wine model solution, respectively. In Merlot and Cabernet Sauvignon musts marked by dried fruit flavors from overripe grapes, its concentration reached 68µg/L. In contrast, in wines marked by these flavors, it never exceeded 20µg/L. We show that (R)-C10 massoia lactone is reduced to (R)-δ-decalactone during alcoholic fermentation. In addition, we underline the contribution of temperature during the growing season on its level in old red wines.

Identification and analysis of piperitone in red wines.

The present study concerns the search for new aroma compounds associated with the flavor of aged and prematurely aged red wines. Sensory descriptive analysis associated with gas chromatography-olfactometry was first performed to find specific odoriferous zones. One of the zones, reminiscent of mint, was found in red wines with a prune flavor. Thanks to several analytical approaches including preparative gas chromatography, p-menth-1-en-3-one (piperitone), has been identified in red wines. The olfactory detection threshold of this terpene reminiscent of mint was 0.9μg/L in model hydroalcoholic solution and 70μg/L in red wines. Chiral multidimensional GC-MS was used to show that piperitone was present mainly in the (R) form in red wines. The concentration of piperitone in aged red wines ranged from a few ng/L to 435ng/L, but the level was not linked to the age of the wine nor to its premature evolution.

Toward a Molecular Understanding of the Typicality of Chardonnay Wines: Identification of Powerful Aromatic Compounds Reminiscent of Hazelnut

Chardonnay wines impart a unique complex aroma characterized by its buttery, yellow stone fruit, melon, bready, and woody notes. Among the terms used in the sensory analysis of these wines, this study investigated hazelnut-like attributes. Multidimensional gas chromatography coupled to olfactometry identified five pyrroles reminiscent of hazelnut: 1-ethylpyrrole-2-carboxaldehyde, 1H-pyrrole, 2-acetyl-1H-pyrrole (first identification in wine), 1-methylpyrrole-2-carboxaldehyde, and 1H-pyrrole-2-carboxaldehyde. Quantitative analyses demonstrated their significantly higher abundance in Chardonnay wines. However, they proved irrelevant in sensory terms, given the low amounts measured in wine compared to their olfactory detection threshold. Nevertheless, the presence of methanethiol derivatives from these pyrroles was investigated in wine. 1-Methylpyrrole-2-methanethiol and 1-ethylpyrrole-2-methanethiol were identified and exhibited hazelnut-like aroma. These compounds, which have not been observed in natural products to date, are potent volatile compounds with detection thresholds of 0.7 and 1.4 ng/L, respectively, in model wine. These findings open up promising perspectives concerning the interpretation of the typical aromatic nuances of some Chardonnay wines.