Application of white wine lees for promoting lactic acid bacteria growth and malolactic fermentation in wine.

In the context of ecological transition, the use of wine by-products for industrial applications is a major challenge. Wine lees, the second wine by-product in terms of quantity, represent a source of nutrients that can be used for stimulating the growth of microorganisms. Here, white wine lees were used as a stimulating agent for the growth of wine lactic acid bacteria (LAB) and to promote wine malolactic fermentation (MLF) driven out by Oenococcus oeni. By adding freeze-dried wine lees to wines under different conditions - including different wine lees at different concentrations and different O. oeni strains at various initial populations - it was observed that wine lees can enhance the growth of LAB and reduce the duration of MLF. The chemical composition of wines was also evaluated, proving that wine lees do not compromise the quality of the wines. In addition, wine lees did not seem to promote the growth of spoilage microorganisms like as Brettanomyces bruxellensis. Altogether, this work reports the possibility of recovering the lees of white wine to obtain a product favoring the MLF of red wines. More general, we propose a recycling strategy of wine by-products to obtain new products for winemaking.

Development of a New Method for the Quantitative Analysis of Aroma Compounds Potentially Related to the Fruity Aroma of Red Wines.

To determine the concentrations of aroma compounds involved in the fruity aroma of red wines, an analytical method was developed and optimized using liquid-liquid extraction and gas chromatography coupled to mass spectrometry (GC/MS). The aim was to reduce sample preparation and analysis time, with a single sample preparation and a single injection being needed to quantify 43 compounds. 19 esters, 13 monoterpenes, 5 C13-norisoprenoids, and 6 C6-aldehyde and alcohol compounds were quantified in 14 red wines made from different grape varieties grown in the Mediterranean basin. Samples were selected based on typical varietal aroma by a panel of experts, who produced 7 olfactory descriptors linked to desirable or non-desirable wine aromas. The instrumental analysis showed variations in concentrations of the quantified compounds among the wines. The wines described using positive fruity descriptors had higher mean total concentrations of esters, C6-alcohols, monoterpenes, and C13-norisoprenoids. Some non-ester compounds were positively correlated with the fruity descriptors. Sensory profile results obtained by a panel of 16 trained judges revealed that the addition of non-ester compounds (including 2 cyclic esters) to a red wine initially described as having cooked fruit aromas had a positive contribution to some fresh fruity notes. This study opens up new avenues for research on the potential involvement of non-ester compounds in the fruity expression of red wines.

Methyl Salicylate, an Odor-Active Compound in Bordeaux Red Wines Produced without Sulfites Addition.

Red wines produced without the addition of any SO2 are currently the source of a new consumer trend. The first characterization approaches regarding these specific wines were devoted to sensory studies that highlighted differences according to the use of SO2 during winemaking. The goal of this paper is to extend our knowledge of such aromatic specificities. Examining experimental wines produced with and without the addition of SO2, aroma fractionation, gas chromatography coupled with olfactometry, and mass spectrometry were applied to identify compounds at the origin of the specificities of these wines. Thus, we identified methyl salicylate as being impacted by the use of SO2 during the winemaking process. Studying a large number of commercial Bordeaux red wines, methyl salicylate was significantly quantified at a higher content in wines without added SO2. A sensory approach revealed a significant impact of methyl salicylate on wines without the sulfite aroma, particularly concerning fruity aromas and wine freshness.

Toward a Better Understanding of Perceptive Interactions between Volatile and Nonvolatile Compounds: The Case of Proanthocyanidic Tannins and Red Wine Fruity Esters-Methodological, Sensory, and Physicochemical Approaches.

The impact of commercial proanthocyanidic tannins on fruity pool of esters, representing the fruitiness of Bordeaux red wines, was assessed in model solutions. It was shown that the presence of tannins in the matrix significantly attenuated perception of fruity notes (p = 0.013). Physicochemical analysis demonstrated that the presence of proanthocyanidic tannins in dilute alcohol solution resulted in a decrease in ester partition coefficients and thus in a decrease in ester contents in the headspace (p < 0.05). This fact highlighted the changes that may occur in wines at a pre-sensory level, prior to sensory evaluation. Finally, a new sensory tool was developed, consisting in an ISO glass containing two compartments separated by a glass wall, providing a way to compare perceived odors according to whether or not the components of the odor mixtures were actually mixed in solution (p < 0.001). This new tool was used to demonstrate the impact and the only implication of pre-sensory level in the consequences of physical mixture between proanthocyanidic tannins and esters on their odor perception.

Impact of Whisky Lactone Diastereoisomers on Red Wine Fruity Aromatic Expression in Model Solution.

The impact of whisky lactone diastereoisomers on the typical fruity expression of red Bordeaux wines was evaluated by sensory analysis. The detection thresholds of cis- and trans-whisky lactone in a dilute alcohol solution (12% v/v) were 20 and 130 µg/L, respectively. Consequently, considering their average concentrations found in oak-aged red wines, cis-whisky lactone was present at supra threshold levels, whereas trans-whisky lactone was below its detection threshold. Adding these diastereoisomers to a red wine fruity aromatic reconstitution at these average concentrations led to a decrease in the perception of this last one, highlighting a masking effect. Sensory profiles of cis- and trans-whisky lactone confirmed that these compounds modified the perception of fruity aromas, decreasing the intensity of red berry fruit notes and increasing that of blackberry fruit and spicy descriptors.

Influence of must yeast-assimilable nitrogen content on fruity aroma variation during malolactic fermentation in red wine.

This study assessed the impact of must yeast-assimilable nitrogen (YAN) content and lactic acid bacteria (LAB) strains used for malolactic fermentation (MLF) on the formation of substituted esters, as well as the corresponding precursors (substituted acids), to investigate the modulation of fruity expression in red wines. In microvinification experiments, a Merlot must was fermented with an initial YAN content of 111 mg/L, or supplemented up to 165 and 220 mg/L. Two Oenococcus oeni LAB strains were used for MLF. Analytical methods were used to quantify substituted esters, as well as the corresponding acids, including, any enantiomeric forms. YAN supplementation of the must significantly increased concentrations of substituted esters of short- and branched-chain alkyl fatty acids produced during alcoholic fermentation (AF) (up to 67% in samples with the highest nitrogen content) and substituted esters of hydroxycarboxylic acids generated during MLF (up to 58% in samples with the highest nitrogen content). YAN supplementation in the must did not affect substituted acid formation during AF. After MLF, short- and branched-chain alkyl fatty acid levels increased in wines made from musts with the highest nitrogen content (up to 56% in samples with the highest nitrogen content), whereas concentrations of hydroxycarboxylic acids increased (up to 55%) independently of the initial YAN content, highlighting the important role of MLF. (2S)-2-hydroxy-4-methylpentanoic acid was only found in wines after malolactic fermentation, suggesting different pathways for each enantiomer and opening up new prospects for the study of bacterial metabolisms. Moreover, sensory profiles revealed a significant increase in black-berry- and jammy-fruit aromas during MLF and a strong positive correlation between these aromas and the production of substituted esters following must nitrogen supplementation and MLF. Aromatic reconstitutions revealed that variations in the concentrations of substituted esters after MLF impacted the fruity aroma of red wines.

Characterisation of mexiletine's translational therapeutic index for suppression of ischaemia-induced ventricular fibrillation in the rat isolated heart.

The 'translational therapeutic index' (TTI) is a drug's ratio of nonclinical threshold dose (or concentration) for significant benefit versus threshold for adversity. In early nonclinical research, discovery and safety studies are normally undertaken separately. Our aim was to evaluate a novel integrated approach for generating a TTI for drugs intended for prevention of ischaemia-induced ventricular fibrillation (VF). We templated the current best available class 1b antiarrhythmic, mexiletine, using the rat Langendorff preparation. Mexiletine's beneficial effects on the incidence of VF caused by 120 min regional ischaemia were contrasted with its concurrent adverse effects (on several variables) in the same hearts, to generate a TTI. Mexiletine 0.1 and 0.5 µM had no adverse effects, but did not reduce VF incidence. Mexiletine 1 µM reduced VF incidence to 0% but had adverse effects on atrioventricular conduction and ventricular repolarization. Separate studies undertaken using an intraventricular balloon revealed no detrimental effects of mexiletine (1 and 5 µM) on mechanical function, or any benefit against reperfusion-related dysfunction. Mexiletine's TTI was found to be less than two, which accords with its clinical therapeutic index. Although non-cardiac adversity, identifiable from additional in vivo studies, may reduce the TTI further, it cannot increase it. Our experimental approach represents a useful early-stage integrated risk/benefit method that, when TTI is found to be low, would eliminate unsuitable class 1b drugs prior to next stage in vivo work, with mexiletine's TTI defining the gold standard that would need to be bettered.

Oak Wood Volatiles Impact on Red Wine Fruity Aroma Perception in Various Matrices.

This research examined the impact of oak wood volatile compounds on the perception of red wine fruity aroma in several matrices. Several aromatic reconstitutions were prepared, consisting of 13 esters, representing the fruity pool of red wine, and 14 oak wood compounds at the various concentrations corresponding to the levels released by light, medium, and heavy toasting of barrels. These reconstitutions were prepared in dilute alcohol solution, dearomatized red wine, and commercial red wine. Sensory analysis revealed the impact of the addition or omission of some oak wood compounds. The "detection threshold" of the fruity pool was then evaluated. The presence of 2-furanmethanethiol individually and the oak wood compound mixture, at concentrations representing various toasting levels, had a significant masking effect on the fruity pool, whereas vanillin had a significant enhancing effect in model solution. Sensory profiles highlighted changes in the perception of fruity nuances in the presence of the oak wood compound mixture. The addition of compounds at concentrations representing different toasting levels led to a predictable increase in the perception of the oak wood descriptors (spicy, smoky, and toasty) in all of the matrices tested. The perception of fruity notes also varied depending upon the toasting level and the complexity of the matrix. In dilute alcohol solution and dearomatized red wine, light toasting preserved or intensified the fruity notes. Generally, in all matrices tested, fresh-fruit and red-berry-fruit notes decreased with the addition of wood at medium and heavy toasting levels.

Static Headspace Analysis Using Low-Pressure Gas Chromatography and Mass Spectrometry, Application to Determining Multiple Partition Coefficients: A Practical Tool for Understanding Red Wine Fruity Volatile Perception and the Sensory Impact of Higher Alcohols.

To evaluate the partition coefficients of volatiles between the liquid and gas phases, an analytical method was developed and optimized using static headspace analysis and low-pressure injection gas chromatography coupled to mass spectrometry (SHS-LP-GC/MS). Two different types of analytical columns were coupled for low-pressure chromatography injection: a narrow restriction microbore column on the inlet side and a mega-bore column on the mass spectrometer side. Coupling these two columns and static headspace analysis to gas chromatography and mass spectrometry resulted in a simple, fast, sensitive, and accurate approach. Several points have been optimized: time to reach the thermodynamic equilibrium in the gas phase, syringe filling rate, gas injection rate, and volume ratio between the gas and liquid phases. This new method was used to determine partition coefficients between the liquid and gas phases and study multicomponent mixtures for which particular perceptive interactions had previously been highlighted. The partition coefficients of 9 esters and 5 higher alcohols were determined in dilute alcohol solution (12% v/v) and dearomatized red wine. These partition coefficients revealed modifications in ester headspace release in the presence of higher alcohols for the first time in this type of matrix. The correlation of these results with sensory data highlighted the role of physicochemical, presensory effects on sensory modifications for the first time, suggesting that this type of interaction may partly modulate qualitative and quantitative fruity perception.

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.

Study of Substituted Ester Formation in Red Wine by the Development of a New Method for Quantitative Determination and Enantiomeric Separation of Their Corresponding Acids.

A new method was developed for quantifying substituted acids including, where applicable, their various unexplored enantiomeric forms. A new step was added to acids' usual quantification methods, consisting of extraction, derivatization to methyl esters, and gas chromatography analysis: preliminary extraction was performed at basic pH to eliminate ethyl esters, thus avoiding their transesterification during derivatization. Quantitation and enantiomeric distribution of some substituted esters and their corresponding acids were established in 31 commercial Bordeaux red wines from 0 to 20 years old. A strong positive correlation was observed between the age of wine and levels of ethyl 2-methylpropanoate, ethyl 3-methylbutanoate, ethyl 2-methylbutanoate, ethyl (3R)-3-hydroxybutanoate, both enantiomeric forms of ethyl 2-hydroxy-3-methylbutanoate, and ethyl (2S)-2-hydroxy-4-methylpentanoate, but not ethyl (3S)-3-hydroxybutanoate. However, the standard deviations of average concentrations for the corresponding substituted acids were so large that only few correlations between concentrations and age were observed. Concentrations of (2S)-2-hydroxy-3-methylbutanoic acid and (2S)-2-hydroxy-4-methylpentanoic acid increased slightly over time, while (2R)-2-hydroxy-4-methylpentanoic acid levels decreased slightly with the age. Variations in the ratio of substituted ethyl esters to their corresponding acids over time detected thanks to these analytical advances suggested that, in general, acids were continuously esterified during aging.

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.

How do esters and dimethyl sulphide concentrations affect fruity aroma perception of red wine? Demonstration by dynamic sensory profile evaluation.

Our study focused on variations in wine aroma perception and molecular composition during tasting over a period of 30min. In parallel, dynamic analytical and sensory methods were applied to study changes in the wines' molecular and aromatic evolution. Dynamic sensory profile evaluations clearly confirmed the evolution of the wine's fruity notes during sensory analysis, highlighting significant differences for red-berry and fresh fruit as well as black berry and jammy fruit, after 5 and 15min, respectively. Dynamic analytical methods revealed a decrease in ester and dimethyl sulphide (DMS) concentrations in the first few minutes. Sensory profiles of aromatic reconstitutions demonstrated that the aromatic modulation of fruity notes observed during wine tasting was explained by changes in ester and DMS concentrations. These results revealed that variations in concentrations of DMS and esters during wine tasting had a qualitative impact, by modulating fruity aromas in red wine.

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 (ß-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.

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

This study focused on the impact of five higher alcohols on the perception of fruity aroma in red wines. Various aromatic reconstitutions were prepared, consisting of 13 ethyl esters and acetates and 5 higher alcohols, all at the average concentrations found in red wine. These aromatic reconstitutions were prepared in several matrices. Sensory analysis revealed the interesting behavior of certain compounds among the five higher alcohols following their individual addition or omission. The "olfactory threshold" of the fruity pool was evaluated in several matrices: dilute alcohol solution, dilute alcohol solution containing 3-methylbutan-1-ol or butan-1-ol individually, and dilute alcohol solution containing the mixture of five higher alcohols, blended together at various concentrations. The presence of 3-methylbutan-1-ol or butan-1-ol alone led to a significant decrease in the "olfactory threshold" of the fruity reconstitution, whereas the mixture of alcohols raised the olfactory threshold. Sensory profiles highlighted changes in the perception of fruity nuances in the presence of the mixture of higher alcohols, with specific perceptive interactions, including a relevant masking effect on fresh- and jammy-fruit notes of the fruity mixture in both dilute alcohol solution and dearomatized red wine matrices. When either 3-methylbutan-1-ol or butan-1-ol was added to the fruity reconstitution in dilute alcohol solution, an enhancement of butyric notes was reported with 3-methylbutan-1-ol and fresh- and jammy-fruit with butan-1-ol. This study, the first to focus on the impact of higher alcohols on fruity aromatic expression, revealed that these compounds participate, both quantitatively and qualitatively, in masking fruity aroma perception in a model fruity wine mixture.

2-bromo-4-methylphenol, a compound responsible for iodine off-flavor in wines.

This study focuses on an off-flavor in wines treated by an acidification technique involving ion-exchange resins. Applying reversed-phase HPLC on a C18 column to a contaminated wine extract resulted in 25 fractions in dilute alcohol medium, and only one, fraction 19, presented this off-flavor. Its composition was analyzed using gas chromatography coupled to olfactometry (GC-O) and mass spectrometry (GC-MS), leading to the identification of 2-bromo-4-methylphenol for the first time as a compound associated with an "iodine" aroma in white, rosé, and red table wines. Contaminated wines presented a wide range of levels, with maximum concentrations of 28900, 7556, and 48000 ng/L and minimum values of 260, 35, and 63 ng/L in white, rosé, and red wines, respectively. Sensory studies investigating 2-bromo-4-methylphenol gave very interesting results. Individual thresholds ranged from 0.15 to >77.4 ng/L in reverse osmosis water, from 0.4 to >193.5 ng/L in white wine, from 0.5 to >774 ng/L in rosé wine, and from 0.5 to >774 ng/L in red wine. The very wide distribution of individual thresholds suggested the presence of two populations, sensitive and nonsensitive, with a bimodal frequency distribution. The odor descriptions quoted by the more sensitive group characterized 2-bromo-4-methylphenol using terms with "iodine" connotations in both the reverse osmosis water and red wine matrices. The descriptors for commercial wines naturally affected by this defect were seafood, iodine, mud, and fish.

Distribution and organoleptic impact of ethyl 2-methylbutanoate enantiomers in wine.

The enantiomers of ethyl 2-methylbutanoate were assayed in several wines using chiral gas chromatography (ß-cyclodextrin). Analyses of 37 commercial red wines from various vintages and origins revealed the almost exclusive presence of the S-enantiomeric form. The average concentration was ∼50 µg/L, but the oldest samples were found to contain higher ethyl 2-methylbutanoate levels than the youngest wines. The olfactory threshold of a racemic mixture of ethyl (2R)-2-methylbutanoate and ethyl (2S)-2-methylbutanoate (50:50, m/m) in dilute alcohol solution was 2.60 µg/L, almost twice that of the S-form, which was 1.53 µg/L. Ethyl (2S)-2-methylbutanoate and the racemic mixture of ethyl (2R)-2-methylbutanoate and ethyl (2S)-2-methylbutanoate had different aromatic nuances: the former was mainly defined by fruity descriptors, such as green apple (Granny Smith) and strawberry, whereas the latter had an unspecific, caustic, fruity, solvent odor. Sensory analysis revealed an enhancing effect of ethyl (2S)-2-methylbutanoate on the perception of fruity aromas in the matrices studied: the "olfactory threshold" of the fruity pool, consisting of esters found in red wines, in dilute alcohol solution alone was higher than that of the same mixture supplemented with 50 µg/L ethyl (2S)-2-methylbutanoate. The sensory profiles of these aromatic reconstitutions highlighted the contribution of ethyl (2S)-2-methylbutanoate to black-berry-fruit descriptors.

Study of sensory interactions among red wine fruity esters in a model solution.

Our study focused on the impact of 12 red wine esters, in complex mixtures, on the perception of fruity aromas. Aromatic reconstructions were prepared in dilute alcohol solution at the average concentrations found in red wines, using pure commercial products. The impact of ethyl propanoate, ethyl-3-hydroxybutanoate, butyl acetate, and 2-methylpropyl acetate was detected by omission tests, although they were present at subthreshold concentrations in the fruity mixture. The "olfactory threshold" of the fruity pool, consisting of all of the esters excluding ethyl propanoate, ethyl-3-hydroxybutanoate, butyl acetate, or 2-methylpropyl acetate was calculated in two different matrices: dilute alcohol solution and dilute alcohol solution supplemented with each of the four compounds mentioned above. The presence of ethyl-3-hydroxybutanoate and 2-methylpropyl acetate in the mixture led to a significant decrease in the olfactory threshold of the fruity pool, demonstrating their synergistic effect in increasing the overall intensity. Sensory profiles revealed that besides ethyl-3-hydroxybutanoate, the omission of each of these compounds had a significant attenuating effect on blackberry and fresh-fruit aroma intensity. These compounds with similar chemical structures participate, both quantitatively and qualitatively, in modulating fruity aromas and, specifically, naturally enhancing blackberry and fresh-fruit aromas.