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International audience; The contamination of grape berries by Botrytis cinerea can drastically damage wine quality, in particular causing colour degradation. In musts obtained from botrytised grapes, SO2 addition is the main means of avoiding oxidation damage due to laccases excreted by the pathogen. However, consumers are becoming increasingly reluctant to accept SO2 addition to wine. Oenological tannins are used for fining wines because of their colloidal properties, and for wine colour stabilisation due to their ability to condense with anthocyanins. They are also known for their antioxidant and antioxidasic properties. They were thus investigated in the present study for their potential as an alternative to SO2 against laccase oxidation.The impact of various types of oenological tannins on musts and wines was studied once added to musts obtained from the Merlot cultivar, comprising 20 % and 50 % botrytised grapes. Laccase activity, antioxidant capacity, composition of phenolic compounds, spectrophotometric and CIELAB colour parameters were assessed in the musts and wines. Sensory analyses were also performed on 3-month-old wines to evaluate the visual, olfactory and gustative consequences of tannin addition. At a 50 % botrytisation rate, the addition of any type of oenological tannins (at a concentration of 100 g/hL) had no effect on laccase activity and did not protect phenolic compounds. However, at the same concentration and at a 20 % botrytisation rate, proanthocyanidin tannins from grape skin were found to be the most promising tannins with simultaneous protective effects, such as an inhibitory effect on laccase enzymes, protection of colour from complete degradation and preservation of some procyanidin compounds.Oenological tannins are promising candidates for protecting wines from Botrytis damage and they induce a differential effect according to their origin and structure. They could be used to reduce the amount of SO2 that is added during vatting. More research is needed to confirm and better understand the mode of action of various tannins at levels lower than the 20 % botrytised rate tested in the present study.

International audience; Grey mould caused by Botrytis cinerea is one of the most serious diseases affecting grapevine (Vitis vinifera L.) in temperate area. It induces chemical changes that have damageable effects on wine quality, especially color degradation. Indeed B. cinerea excretes enzymes like laccases able to turn phenolic compounds from grape berries into quinones leading to a possible oxidasic casse, unacceptable in terms of product quality. Even a low contamination degree (5%) can lead to a perceptible loss of wine sensory quality [1]. Beside manual selection of healthy grape clusters, few eco-responsible alternatives to SO2 are proposed to treat laccases. Commercial tannins, already authorized by OIV for fining, are interesting candidates as they have also antioxidant and antioxidasic properties. However, very few scientific or technical papers are available on the subject [2]. Therefore, we studied here commercial tannins as a possible alternative to SO2 at the vatting.Five tannins were chosen from different vegetal sources: procyanidins from seed (TPA) (low mPD) and skin (IE) (high mPD) of grape berries, profisetinidins from quebracho tropical tree (T), ellagitannins from oak tree (Q) and gallotannins from nutgall (G). Musts with 20 % and 50% botrytization rates were obtained from healthy and botrytized grapes (strain 213) from Merlot cultivar. High contamination degrees were chosen to reveal contrasted effects. The impact of commercial tannins addition at the vatting (100 g/hL) on musts and wines protection against laccase damages was studied with regards to the laccase activity, antioxidant capacity, phenolic compounds composition and CieLab color parameters. Sensory analyses were also performed on 3 month-wines to evaluate visual, olfactory and gustative impacts of tannins additions. Results showed that at 50% botrytisation rate, the addition of any type of commercial tannins at 100 g/hL seemed to be ineffective on laccase activity and phenolic compounds protection. Laccase activities > 5 U/mL were found in 3 month wines leading inevitably to oxidasic casse. Despite this high botrytisation rate, calculated color differences (E) and sensory analyses showed differences between tannins: wines obtained with IE and G tannins were darker than the control wine whereas wine with Q tannins was lighter. At a 20% botrytisation rate, differences between tannins addition were more evident. Procyanidic tannins from IE or TPA showed an inhibitory effect on laccase activity and protected color against complete degradation. Moreover, wine with IE tannins appeared to be darker and perhaps more qualitative with regards to olfactory and gustative aspect than the control wine.

Condensed tannins and polymeric pigments are two families of macromolecules which play important roles on the organoleptic quality of red wine. Their oligo-polymeric structures and their evolutions during red wine aging are poorly known. The objective of this study is to deepen our knowledge of their structures and their evolutions during red wine aging. During our work, we characterized, for the first time in plant kingdom, a new family of condensed tannins named : crown condensed tannins, which have specific properties. They are more polar than B-type tannins. During red wine aging, the concentration of B-type tannins decreased while the crown tannins remained stable. Their concentrations are higher in Syrah wines than in wines made from Cabernet Sauvignon and Merlot grapes. From a sensory point of view, a strong correlation between the concentration of crown tannins and the intensity of astringency rated by the tasters was obtained. The first biologic activity assay of the crown tetramer showed an interesting inhibitory activity on aggregation of β-amyloid peptide involved in Alzheimer's disease. At the same time, a new quantification method of ethylidene bridge linked condensed tannins via a specific marker using fluorescence detection has been developed. Concerning polymeric pigments with different types of inter-flavonoids linkages, their acidic depolymerization mechanisms have been clarified for the first time and a quantification method using a UPLC-Q-TOF system has been developed. Oligo-/polymeric pigments contributed more to the color of old wine than mono-/dimeric pigments. The concentration of the pigmented oligo-polymers with A type linkages is more stable than that of polymeric pigments by B-type linkages or by ethylidene bridge during red wine aging. In addition, during our study of polymeric pigments, A-F(A type)-F(n) and F(n)-A-F(A type) structures as well as the acetylated form of trimeric anthocyanin and acetylated forms of dimeric anthocyanin linked by ethylidene bridge have been shown for the first time.; Les tanins condensés et les pigments polymérisés sont deux grandes familles de macromolécules qui jouent des rôles importants sur la qualité organoleptique du vin rouge. Leurs structures oligo-polymériques ainsi que leurs évolutions durant le vieillissement du vin rouge sont mal connues. L’objectif de cette étude est d’approfondir notre connaissance sur leurs structures et leurs évolutions durant le vieillissement. Durant ce travail, nous avons caractérisé, pour la première fois dans le règne végétal, une nouvelle sous-famille de tanins condensés nommés : les tanins condensés couronnes, qui ont des propriétés spécifiques. Ils sont plus polaires que des tanins condensés de type B. Durant le vieillissement, les concentrations des tanins de type B diminuent alors que celles des tanins couronnes restent plutôt stables. Leurs concentrations sont plus élevées dans les vins issus de cépage Syrah que dans les vins issus de cépage Cabernet Sauvignon et Merlot. Au niveau sensoriel, une forte corrélation entre la concentration des tanins couronnes et l’intensité d’astringence ressentie par les dégustateurs a été montrée. Un premier test d’activité biologique du tétramère couronne montre une activité inhibitrice intéressante de l’agrégation du peptide β-amyloïde impliquée dans la maladie d’Alzheimer. En même temps, une nouvelle méthode de quantification des tanins condensés liés par pont éthylidène via un marqueur spécifique en utilisant une détection par fluorescence a été développée. Concernant les pigments polymérisés avec différents types de liaisons inter-flavonoïdes, leurs mécanismes de dépolymérisation chimique en milieu acide ont été clarifiés et une méthode de quantification sur un système UPLC-Q-TOF a été développée. Les pigments oligo-/polymériques contribuent plus à la couleur du vin vieux que les pigments mono-/dimériques. La concentration des structures oligo-polymériques ayant des liaisons de type A est plus stable que celle des pigments polymérisés par des liaisons de type B ou par le pont éthylidène durant le vieillissement du vin. De plus, durant nos investigations sur les pigments polymérisés, les structures de type A-F(type A)-F(n) et de type F(n)-A-F(type A) ainsi que les formes acétylées d’anthocyane trimère et les formes acétylées des anthocyanes dimères liées par pont éthylidène ont été montrées pour la première fois.

Lors de l’élevage des vins avec le bois de chêne, plusieurs molécules d’intérêts organoleptiques comme les ellagitanins (vescalagine, castalagine, roburines A, B, C, D, E et grandinine), sont extraites. Leurs concentrations dans le bois et le vin sont très variables et leurs cinétiques d’extraction au cours de l’élevage ainsi que leurs propriétés organoleptiques dans les vins sont mal connues. Dans le but de classifier chaque douelle pour fabriquer des barriques avec des indices en polyphénols (IP) totaux significativement différents, un système proche infrarouge (NIRS), Oakscan®, a été mis en place par la tonnellerie Radoux. Notre objectif était d’étudier l’influence de ce mode de classifications des bois au niveau de la composition moléculaire et organoleptique des vins. Dans un premier temps, la classification NIRS des bois de chêne a été confirmée par quantification des concentrations en ellagitanins totaux et moléculaire par HPLC-UV-MS. Une forte variabilité des concentrations en ellagitanins des bois est observée entre 5,95 et 32,91 mg d’équivalent acide ellagique/g de bois. De plus, la classification NIRS des bois se corrèle avec les analyses chimiques (p < 0,02%). Cette nouvelle méthode permet donc de fabriquer des barriques avec un IP moyen différent (IP : 11 à 70). Dans un second temps, des vins de différentes origines et cépages sont élevés dans les barriques classifiées. La cinétique des teneurs en ellagitanins montre l’influence de la classification des bois de chêne (p < 5%). En effet, dès les premiers mois d’élevage, une augmentation en ellagitanins jusqu’à un maximum est obtenue. Plus les bois sont riches, plus le maximum de concentration en ellagitanins des vins est élevé et décalé dans le temps. Puis, une lente diminution des concentrations en ellagitanins est observée. Les influences du grain et de la chauffe des bois ont également été analysées. La solubilisation dans les vins des composés aromatiques des bois de chêne classifiés par Oakscan® montre dans plusieurs cas que les teneurs en aldéhydes furaniques et en syringol impliqués dans les perceptions du fumé/grillé sont corrélées avec la classification NIRS et également avec l’IP des bois. Ainsi, un vin élevé au contact de bois riches en polyphénols possède des concentrations en arômes fumé/grillé plus importantes. Néanmoins, l’intensité de la chauffe a un rôle prépondérant sur les concentrations de ces arômes boisés. Parallèlement, les propriétés organoleptiques des vins élevés avec du bois de chêne à 6, 12, 18 ou 24 mois et testées par un jury entrainé, montrent des différences significatives corrélées à l’IP des barriques. Les vins élevés au contact des IP les plus importants sont significativement décrits comme plus boisés, fumés/grillés et épicé au nez. En bouche, l’amertume et l’astringence sont significativement plus importantes pour les vins élevés dans les barriques possédant les plus fortes concentrations en ellagitanins. A contrario, le fruité des vins, au nez et en bouche, est généralement noté comme moins important pour les vins élevés avec des barriques à IP le plus haut.L’influence de la classification des bois, en fonction de leurs grains et de leurs IP, sur la consommation en oxygène des vins rouges a été suivie grâce à une méthode innovante et non invasive. Les résultats montrent que 96% de l’oxygène dans le vin à T0 est consommé huit jours après entonnage. Des différences significatives (p < 0,01%), entre les vitesses de consommation de l’oxygène et l’IP ou le grain des barriques, sont observées. La vitesse de consommation d’oxygène augmente en corrélation de l’IP des barriques ou de la taille du grain. Ces résultats permettent d’envisager l’utilisation de méthodes de sélection non empiriques et fiables des bois de chêne en fonction de leurs grains ou de leurs concentrations en ellagitanins ce qui permet de fabriquer des barriques classifiées à l’aide de nos résultats conférant, au vin, des propriétés organoleptiques maîtrisées., During the wine aging with oak wood, some compounds with interesting organoleptic properties such as ellagitannins (i.e., vescalagin, castalagin, roburins A, B, C, D, E and grandinin) are extracted. The ellagitannins concentrations in oak wood and wine are highly variable and their extractions kinetic during the aging as well as their organoleptic impacts on wines are poorly known and still unclear. In order to classify each stave according to their polyphenolics index (IP) before making the barrels, an infrared system (NIRS), Oakscan®, was develop by the tonnellerie Radoux. Our aim was to study the influence of this wood classification on the wines molecular composition and organoleptic properties.In the first place, the NIRS oak staves classification has been confirmed by the determination of the total ellagitannins concentration as well as the specific levels of each ellagitannins molecule by HPLC-UV-MS. A high variability of the ellagitannins level in wood between 5.95 ± 0.30 and 32.91 ± 0.98 mg ellagic acid equivalent/g of dry wood was observed. Furthermore, the wood infrared classification is correlated with chemical analyzes (p < 0.02%) and allow the production of barrels with different IP (IP: 11, 12, 16, 21, 26, 30, 35, 36, 39, 40, 41, 50, 51, 53, 62, 67 et 70).In a second place, some wines were aged in the classified barrels. The ellagitannins levels show the oak wood classification influences (p < 5%). Indeed, the first months of aging, the ellagitannins concentration increased until a maximum was obtain . Indeed, this maximum concentration in wine aged in barrel manufactured with the wood richer in ellagitannins was higher and latter (2.30 ± 0.05 after 4 months and 11.56 ± 0.31 mg ellagic acid equivalent/L of wine after 12 months respectively for the IP 21 and IP 70 barrels). After this maximum, a slow decrease of the ellagitannins level was observed. The influences of grain and toasting were also analyzed. The aromatics compounds solubilization of classified oak wood by Oakscan® show that the furanic aldehydes levels (furfural, alcool furfurylique et 5-méthylfurfural) and the syringol involved in the smocked/toasted aromas were correlated with the NIRS classification and the wood IP. So, a wine aged in contact with wood richer in polyphenols compounds was describe as more smocked/toasted. Nevertheless, the toasting intensity (which formed these compounds by thermo-degradation of hemicelluloses and lignins) plays a major role on their concentrations. Moreover, organoleptic properties of the wines aged with oak wood (barrels, staves) at 6, 12, 18 or 24 month and tested by trained judges were significantly impacted by the IP barrels. In fact, wine with the highest ellagitannins level was significantly described with a higher woody, smoked/burned and spicy in nose. In mouth, the bitterness and the astringency were significantly higher in wine containing the highest ellagitannins level. Whereas, the wine fruity aroma, in nose and mouth, was generally descript as lower in wine aged with the barrel with the IP higher.The influences of wood classification, in relation with the grain and the IP, on the red wine oxygen consumption after being put into barrels were analyzed with a new no invasive method. The results show that 96% of the oxygen in wine at T0 was consumed after 8 days. Significant differences (p < 0.01%) between the oxygen consumption speed and the barrel IP or the grain were observed. The oxygen consumption speed increase with correlation of barrel IP or the size of grain. These results allows the utilization of method not empirical and reliable method to select oak wood regarding their grain or their ellagitannins concentration in order to be able to produce oak barrels classified by means of our results to give organoleptic properties controlled to the wine.