Ethylphenols are important aromatic compounds of red wines. These compounds are formed in wines by some yeast species belonging to the genus BrettanomyceslDekkera in the presence of hydroxycinnamic acids. These volatile phenols are responsible for the 'phenolic', animal' and 'stable' off-odours found in certain red wines. The results presented show that the synthesis of the high quantities of ethylphenols found in the 'phenolic' red wines can occur during the ageing of wines having normally completed their alcoholic and malo-lactic fermentations. This olfactory fault caused by BrettanomyceslDekkera is found more frequently than the classical 'mousy-taint' attributed to this yeast genus. In addition, the study of the mechanisms of biosynthesis of ethylphenols by BrettanomyceslDekkera has shown the sequential activities of two enzymes. The first, is a cinnamate decarboxylase (CD), which assures the transformation of certain cinnamic acids into the correspondent vinylphenols; the second is a vinylphenol reductase, which catalyses the reduction of vinylphenols into ethylphenols. The CD activity of BretfanornyceslDekkera is not inhibited by the polyphenolic compounds of red wines (procyanidins and catechins) while these compounds do inhibit the CD activity of Saccharomyces cereuisiue. On the other hand, the substrate specificities of the CD activities of BrettanomyceslDekkera and Saccharomyces are different.

<p style="text-align: justify;">L'élevage des vins en barriques modifie profondément leur expression aromatique.</p><p style="text-align: justify;">L'étude par chromatographie en phase gazeuse et spectrométrie de masse permet d'identifier plusieurs substances volatiles appartenant à la fraction phénolique des arômes.</p><p style="text-align: justify;">Les vins rouges présentent naturellement une composition complexe en phénols volatils alors que celle des vins blancs est plus simple. L'élevage sous bois entraîne une augmentation notable des phénols déjà présents ainsi que l'apparition de molécules spécifiques au bois dechêne brûlé.</p><p style="text-align: justify;">L'interaction des levures et des bactéries avec le bois est mise en évidence.</p><p style="text-align: justify;">Les vins rouges se caractérisent par une présence parfois abondante d'éthyl phénols, les vins blancs qui ne subissent pas la fermentation malolactique s'en différencient par l'abondancede vinyl phénols.</p><p style="text-align: justify;">L'étude sensorielle de chaque substance permet de démontrer le rôle négligeable de certaines : furfural, méthyl-5-furfural, alcool furfurylique et le rôle exceptionnel joué par d'autres : cis et trans β-méthyl-γ-octalactone, vanilline et dans certains cas éthyl-4-phénol et éthyl-4-gaïacol.</p><p style="text-align: justify;">+++</p><p style="text-align: justify;">Wood storage of wines changes profondly their aromatic expression.</p><p style="text-align: justify;">Several volatile substances from wines and oak woods phenolic fraction of aroma are identified by gas chromatography and mass spectrometry. Wood storage increases natural phenols concentration. Simultaneously specific burned wood molecules appear.</p><p style="text-align: justify;">Yeast and bacterial interaction with wood is demonstrated. Ethyl phenols are characteristic of red wines and vinyl phenols of white wines without malolactic fermentation.</p><p style="text-align: justify;">The sensorial analysis of each substance demonstrates the negligible intervention in wine aroma of furfural, 5-methyl-furfural, and furfuryl alcohol, and the important participation of cis and trans β-methyl-γ-octalactone, vanilin 4-ethyl-phenol and 4-ethyl gaïacol.</p>

In agricultural sciences, breeding strategies have historically been used to select new, optimized plant varieties or animal breeds. Similar strategies are possible for genetic improvement of wine yeasts. We optimized 11 relevant enological traits in a single clone using successive hybridization and segregation steps. A hybrid obtained by crossing two parent strains derived from commercial wine yeasts showed that some of the traits were readily optimized. Dominance/recessivity, heterosis and transgression were observed among 51 segregating progeny. On the basis of this information, all the optimal characters from both parents were combined in a single strain following two targeted sexual crosses. This article presents a powerful methodology for obtaining a single wine strain with numerous fermentative qualities that does not produce off-flavors.

<p style="text-align: justify;">Au-delà de son action de cintrage, le chauffage du bois de chêne provoque une thermodégradation de certains de ses composants. Les auteurs étudient l'influence de l'intensité de brûlage du bois de chêne sessile <em>Quercus sessilis</em> sur certains composés extractibles. Afin de se rapprocher des conditions d'extraction par un vin, le bois brûlé à différents degrés est placé au contact d'une solution hydroalcoolique modèle.</p><p style="text-align: justify;">La thermolyse des principaux polymères pariétaux du bois, produit de nombreux composés volatils et odorants (aldéhydes furaniques, phénols volatils, aldéhydes phénols, phényl cétones). La concentration en β-méthyl-y-octalactone augmente notablement avec le chauffage du bois et simultanément les tanins hydrolysables sont en partie dégradés.</p><p style="text-align: justify;">La chauffe légère ne produit que de faibles variations. La chauffe moyenne correspond au maximum de synthèse de la majorité des composés aromatiques étudiés. A partir et au-delà de la chauffe forte, les réactions de thermodégradation, mais très vraisemblablement aussi une modification de la structure de la lignine vers une forme moins réactive, entraînent une diminution de l'ensemble des composés extractibles.</p>

Toasting changes both the quantity and the quality of the extractable substances in the oak wood of barrels used for the aging of fine wines and spirits. Mastery and repeatability of toasting are vital in the production of quality barrels to be used for the aging of wines and spirits. In this study, we show that it is possible for a given cooperage to differentiate barrel toasting levels by analyzing a certain number of volatile and semivolatile compounds resulting from the thermal degradation of oak. Toasted wood components, which can be extracted by the wines or spirits during the aging process, are normally analyzed after the wood has soaked in standard alcoholic solutions and can be used to control the intensity of the wood toasting. The results of the comparative analysis presented in this work show that headspace analysis with a microextractive method using a stationary polydimethylsiloxane type phase is a promising technique for analyzing toasted oak wood from barrels. It is easier to use than the traditional maceration and extraction method and provides similar information.

Grape rot is one of the major causes of degradation of many grape components and, thus, of deterioration in wine quality. In particular, the association of Botrytis cinerea with other, less visible, fungi frequently leads to the development of organoleptic defects in grapes and sometimes in wines. This study examines the nature of the volatile compounds responsible for mushroom, mossy, or earthy odors detected by gas chromatography-olfactometry in organic extracts of rotten grapes and musts. 2-Methylisoborneol, (-)-geosmin, 1-octen-3-one, 1-octen-3-ol, 2-octen-1-ol, and 2-heptanol were identified or tentatively identified. Their concentrations in musts were determined, and the impact of alcoholic fermentation by the yeast Saccharomyces cerevisiae was studied. The ability of fungi isolated from rotten grapes (Botrytis cinerea; Penicillium species including P. brevicompactum, P. expansum, P. miczynskii, P. pinophilum, P. purpurogenum, and P. thomii; Aspergillus section nigri; Rhizopus nigricans; and Coniothyrium sp.) to produce some of the identified compounds was evidenced.

Powdery mildew due to the fungus Uncinula necator is an important disease for the vineyard. The development of the fungus at the surface of the berries leads to the occurrence of a very characteristic and sometimes intense mushroom-type odor cited as an important default for grapes quality. Gas chromatography/olfactometry, gas chromatography, and multidimensional gas chromatogaphy/mass spectrometry techniques were used to investigate the most important odorants of grapes diseased by powdery mildew. Among 22 odorants detected, strongly odorant compounds were identified or tentatively identified in purified extracts obtained from grapes diseased by powdery mildew. Aroma extraction dilution analysis (AEDA) analysis revealed that 1-octen-3-one (mushroom odor), (Z)-1,5-octadien-3-one (geranium-leaf odor), and an unidentified odorous zone (fishy-mushroom like odor) were the most potent volatiles of the diseased grapes. In the presence of nonproliferating Saccharomyces cerevisiae yeast cells, and consequently during alcoholic fermentation, the enzymatic reduction of 1-octen-3-one and (Z)-1,5-octadien-3-one to much less odorant compounds, namely 3-octanone and (Z)-5-octen-3-one, was shown. Those results explain to some extent the disappearance of the fungal aroma specific to powdery mildew grapes during alcoholic fermentation.

Musty, earthy odors are highly detrimental to the aromatic quality of wines. A characteristic aroma of freshly tilled earth, damp cellar was studied in some red and white wines of different origins. The extraction and purification of the wines marked by this odor have shown after analysis by gas chromatography-olfactometry a unique strong odorous zone having the same odor as the one perceived at tasting. The compound responsible for this odorous zone was identified by gas chromatography-mass spectrometry as geosmin (trans-1,10-dimethyl-trans-9-decalol), which possesses a distinctive earthy odor. Geosmin may be present in wines at levels higher than the racemic geosmin olfactory perception threshold, thus suggesting its contribution to their off-aroma. Moreover, the presence of this compound in juice taken from freshly crushed grapes suggests that microorganisms that develop on the grapes may contribute to the presence of this compound in wines.