Georgia Lytra

Impact of Perceptive Interactions on Red Wine Fruity Aroma

A preparative HPLC method was applied to aromatic red wine extracts. Twenty-five fractions with various flavors were thus obtained, and several aromatic reconstitutions were produced by mixing some of these fractions. Discriminative tests revealed that the omission of some fractions from the mixture of fruity fractions or the addition of others affected the overall expression of fruity aroma. Sensory profile analyses identified significant differences among aromatic reconstitutions in terms of intensity of black-berry, as well as fresh-, and jammy-fruit descriptors. A fraction with a very low fruity note (fraction 17) had an additive effect on the fresh fruity aroma, while fractions with caramel and lactic notes (fractions 3-5) had a masking effect on this aroma and an additive effect on the jammy-fruit aroma. Further analysis revealed that ethyl 2-hydroxy-4-methylpentanoate was eluted in fraction 17, while diacetyl, acetoin, acetic acid, and γ-butyrolactone were eluted in fractions 3-5. Omissions tests established that ethyl 2-hydroxy-4-methylpentanoate was responsible for enhancing black-berry and fresh-fruit aroma and that a combination of diacetyl, acetoin, acetic acid, and γ-butyrolactone, at levels between 2 and 40% of their perception thresholds, had the same hypoadditive effect on the overall and fresh fruity aroma as fractions 3-5.

Identification of Piperitone as an Aroma Compound Contributing to the Positive Mint Nuances Perceived in Aged Red Bordeaux Wines

Although a sensory definition of the aging bouquet of red Bordeaux wines was recently established, its chemical transcription has only partially been elucidated. A multiple-step approach, combining sensory evaluations of red Bordeaux wines and aromatic reconstitutions of wine extract fractions, was used to identify the molecular markers involved. One wine with a high aging-bouquet score and a mint nuance has received particular attention. Various reconstitution and omission tests highlighted the contribution of two specific fractions to the intensity of the perception of mint aroma. Gas chromatography coupled to olfactometry and mass spectrometry was applied to the targeted fractions to identify molecular marker(s) responsible for the mint nuance in fine red Bordeaux wines. A similar analytical process was applied to selected fractions of essential oils presenting mint odors to characterize them and interpret the mass spectrometry data. This approach resulted in the detection of piperitone, a monoterpene ketone that, to the best of our knowledge, was reported for the first time as a contributor to the positive mint aroma of aged red Bordeaux wines.

Distribution and Organoleptic Impact of Ethyl 3-Hydroxybutanoate Enantiomers in Wine.

Enantiomers of ethyl 3-hydroxybutanoate were assayed in 87 commercial wines from various vintages and origins, using chiral gas chromatography (β-cyclodextrin). Generally, ethyl 3-hydroxybutanoate levels were higher in red than in white wines of the same age. The average S/R enantiomeric ratio of this compound in red wine was approximately 75:25 (± 13), with an average total concentration of ∼ 450 (± 150) μg/L. In red wines, R-form levels increased gradually during aging, but no variations were observed in S-form concentrations. To our knowledge, no previous research had determined the enantiomeric distribution of this compound in wine. The olfactory threshold of the S-form in dilute alcohol solution was 21 mg/L, one-third that of the R-form: 63 mg/L. The S- and R-forms had different aromatic nuances. The olfactory threshold of their mixture (85:15, m/m) was 14 mg/L, indicating a simple additive effect in this binary mixture. Furthermore, the concentrations found in red wines were considerably below the olfactory threshold under the same experimental conditions. Sensory analysis revealed that ethyl 3-hydroxybutanoate (S/R, 85:15, m/m) had an enhancing effect on the perception of fruity aromas in the matrices studied. Sensory profiles highlighted the contribution of ethyl 3-hydroxybutanoate to red-berry and fresh-fruit descriptors, despite its subthreshold concentrations.

Influence of lactic acid bacteria strains on ester concentrations in red wines: Specific impact on branched hydroxylated compounds

This research investigated the influence of lactic acid bacteria (LAB) strains on ester levels in Bordeaux red wines. These wines were made in five Bordeaux areas in two vintages, using three yeast strains. Malolactic fermentation (MLF) was carried out using industrial starters or indigenous strains, each in triplicate. Ester concentrations were determined by liquid-liquid-extraction- or HS-SPME-GC/MS at various stages in the winemaking process. The levels of most compounds were slightly impacted by LAB, depending on grape variety. Nevertheless, branched hydroxylated esters, such as ethyl 2-hydroxy-3-methylbutanoate and ethyl 2-hydroxy-4-methylpentanoate were the only compounds to be strongly influenced by the bacteria strain, regardless of matrix composition or the yeasts used for alcoholic fermentation. Moreover, the effect observed after MLF persisted over time, for at least 12months. These esters are apparently important markers of LAB esterase activity. To our knowledge, this was the first time they had been identified in this role.

2-Methylbutyl acetate in wines: Enantiomeric distribution and sensory impact on red wine fruity aroma

Enantiomers of 2-methylbutyl acetate were assayed in red and white commercial wines from various vintages and origins, using chiral gas chromatography (γ-cyclodextrin), revealing the exclusive presence of the S-enantiomeric form. Results also confirmed that (S)-2-methylbutyl acetate levels were generally higher in red than white wines of the same age, and that acetate levels increased gradually during ageing. Olfactory threshold of (S)-2-methylbutyl acetate was evaluated at 313µg/L in dilute alcohol solution (12% v/v) and 1083µg/L in a fruity aromatic reconstitution, reflecting its presence in wines at subthreshold concentrations. At concentrations considerably lower than its olfactory threshold, 2-methylbutyl acetate was associated with blackberry-fruit and banana notes. It was also revealed that, even at subthreshold concentrations, this compound had a modification on the perception of fruity aromas in the matrices studied. Sensory profiles highlighted, for the first time, its specific contribution to black-, fresh-, and jammy-fruit notes, despite its subthreshold concentrations.

Correction to Olfactory Impact of Higher Alcohols on Red Wine Fruity Ester Aroma Expression in Model Solution.

Published: February 1, 2016 Figure 2. Detection probability of fruity reconstitution in different matrices: aromatic impact of higher alcohols at (a) low, (b) medium, and (c) high concentrations added to fruity reconstitution in dilute alcohol solution. ∗, expressed in milliliters of total fruity reconstitution (FR) diluted in 50 mL of matrix. DAS, dilute alcohol solution; HA, higher alcohols. The curves are drawn according to a sigmoid function. Addition/Correction