Panorama Et Synthèse Du 8Ème Symposium International D Œnologie De Bordeaux

PALLAS, PANORAMA AND SYNTHESIS OF THE 8TH INTERNATIONAL ŒNOLOGICAL SYMPOSIUM OF BORDEAUX, PG.1

PANORAMA AND SYNTHESIS OF THE 8TH INTERNATIONAL OENOLOGICAL SYMPOSIUM OF BORDEAUX- JUNE 2007

By Sophie PALLAS, Oenologist

Close to 200 communications, of which 42 were selected for the event extending over 2 days and a half, further completed by some twenty workshops: due to this extent, it is not possible to be exhaustive! It starts off with the preliminary selection completed by the scientific comity of the Faculty of Oenology of Bordeaux for the oral presentations and continues with my vision as an oenologist; this panorama will therefore be subjective. Furthermore, joint to this is the vocation of Infowine, which is to diffuse scientific information of immediate or medium term interest for the economic and qualitative progression of the industry. The report follows the chronological order of the symposium with a grouping of the subjects by theme. Each communication is further referenced by the code attributed to the corresponding poster. The details of the communications and posters can be consulted online on the Symposium web site.

1st day Theme I- Viticulture and grape quality Viticulture naturally found its place in the opening of this oenological symposium due to its implication in problems which have a determining impact on the final quality of the wine. Beyond the foliar application of Nitrogen on white grapevines, in order to favour the synthesis of aromatic precursors, notably thiols (F.CHARRIER et col., I.10, ITV France), we also have the notable presence of the stilbene family in three articles. These are cardio-protective, anti-cancerous, neuro-protective, anti-inflammatory, anti-fungal, anti-bacterial agents… implicated in human health as well as in phytopathology, for example, resveratrol has been recognized for some 5000 years in Chinese and Japanese medicine. Causing a decrease in the use of phytosanitary products (resveratrol increases the plant’s resistance to cryptogamic diseases) and bringing true health benefits are without a doubt a good start for the promotion of the image of the wine industry within the current accusing social context. The first hypothesis of over-expressing the gene of the stibene synthase presented by P. JEANDET et col. of the University of Reims (I.28) seems to be the most efficient, but rises from being transgenic. The identification by the same authors of chitosan, derived from the deacylation of chitin (the constituent of mushroom cell walls), as a stimulator of the synthesis of resveratrol in the vine is an alternative (I.27). Finally, the observation of the effect of the application of ethylene on grapes after harvesting – implicated in the cellular metabolism during the maturation- demonstrates a positive effect on the synthesis of trans-resveratrol as well as on the extractable anthocyanins (F.MASSIMO RIZZINI et col., I.42, University of Padova, Italy).

The phenolic compounds and their evolution during the maturation are not forgotten. They are the subject of new approaches within the publication by VICENS ANYSIA et col. (I.44, INRA of Montpellier): the accumulation of tannins before véraison, the mild degradation of the cell walls or the evolution of polysaccharides across the maturation observed on the Syrah grape variety are further topics to be developed.

The formation of earthy-mouldy flavours is a significant concern in European vineyards. Numerous studies have been conducted on this subject and demonstrate advancements in the understanding of the various biological mechanisms which are implied: by putting forward the role of Botrytis cinerea and of complexes formed with Penicillum ( V. LEMPEREUR , I.35, ITV Villefranche et de S. LAGUERCHE, I.31, Faculty of Bordeaux) and by studying the growth factors of moulds in the vines C. CHARPENTIER, I.09, ENSBANA). This last study underlines the role of temperature (adaptation to temperatures of the magnitude of 30°C seem to be acquired for some strains of Botrytis cinerea) and of CO2 in the atmosphere; the climatic changes (see Words of expert N°7 Infowine on global warming) foreshadow the presence of still more prosperous days for moulds… Methods of treatments are proposed by V. LEMPEREUR with the use of lipidic

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Finally, to end this vision on the viticultural subjects, high resolution aerial imagery for the intra-“parcelle” management according to vigor (A.M COSTA FERREIRA, I.43, ENITA of Bordeaux) is without a doubt a tool to consider for the optimization of the final quality (selective picking of grapes, reasoned work during the vegetative stages,…) when the planted surfaces do not allow for a simple visual assessment.

Theme III- Processes and sensors Oxygen is a variable that is not well controlled in oenology and that interacts strongly with the compounds in the wine, even after bottling. Its effect was noted a long time ago on champagne wine, where strong disparities were noted between bottles of the same batch and capsule, this being linked to the unpredictable contribution of oxygen during the disgorgement. A simple solution proposed by M. VALADE (CIVC, III.34) is the « jetting » technique which consists of injecting diluted bisulfite to provoke the rising of the foam and an evacuation of the oxygen. Another solution is to limit the contribution of the oxygen by the use of a disgorgement device under a controlled atmosphere (P. JEANDET et col., III.19, University of Reims). In the context of red wines, M.BERTUCCIOLI of the University of Florence (III.02), speaks less about oxygen than about the Redox potential as a direct factor on the evolution and stabilization of wines during their development. The application of titanium electrodes, covered with platinum creates a controlled electric micro-current which allows for the providing of a better expression of the fruit, a significant decrease in astringency as well as a better combination of tannins and anthocyanins.

The second thematic which seems interesting to underline is the concern about a reasoned management during the production processes. The adoption of regenerative pre-layers of vegetal origin (C. BOITELLE, III.03, Faculty of Bordeaux), instead of diatomites, the wastes of which are responsible for 30% of the pollution generated by French agricultural exploitations, are to be considered with attention… however the process still remains to be optimized in terms of the regeneration and the impact on colour. Joining this thematic of sustainable development by management of energy expenditures, M. SABLAYROLLE et col. (I.33), propose a model of fermentation predictions in function of different parameters (sugar, nitrogen, temperature and ethanol). In the adjustment of one or another factor, the winemaker has the possibility to better mediate in terms of the immobilization of tanks and of the cooling expenses.

The communication of P. NOILET et col. (III.26, BUCHER VASLIN and the Faculty of Bordeaux) addresses a particular question, which is that of the reduction of the sugar content of the must within the present context, which has caused a continual, gradual increase of alcohol degrees in the last 15 years (an average increase of 2 alcohol degrees over all the vineyards of the planet). The removal of alcohol on finished wines poses significant risks and can lead to a degradation of quality, P. NOILET favours the operation on musts by coupling two membrane units (ultrafiltration and osmotic). From the treated volume a given a quantity of 30% is bleed from the tank, the permeate of which, after successive passages across the two membranes, is reincorporated into the initial tank and hence lowers its global concentration of sugars.

This afternoon devoted to processes was completed with a presentation of the studies more specifically dedicated to the treatment of grapes and wines contaminated with Ocratoxin A. A statistical study on 80 viticulturists completed in the south of France clearly demonstrates the significance of the OTA phenomenon: 50% of the wines contained OTA and 4% of the wines surpassed the norms authorized and even very high levels were noted (L. BONVARLET, V.03, ITK et BAYER). Among the favourable factors for this contamination, the insufficient protection from grape worms is in a primary position. The treatments proposed during this symposium for contaminated lots unfortunately remains partial. The polymer chitin-glucan- extracted from Aspergillus niger – presented by M. TEISSEIDRE (A. BONNET et col., III.04, Faculty of Bordeaux) is an interesting option (up to a 30% reduction of the content of OTA on a heavily

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These studies which allow for a better understanding of the contaminations due to moulds on the vines and also the treatment options represent an important issue for the industry. The affirmation of Jean-Claude RUF of the OIV, invited to close the workshop on the subject, “the sanitary security of the consumer continually takes up a more important position”, sounds like an advertisement. The project of the reduction of the maximum authorized level of OTA (2µ/L) confirms this trend.

2nd day Theme IV- Microrganisms of grape and wine Notoriously monopolizing a lot of attention in these last years is Brettanomyces bruxellensis which is the topic of numerous communications. In the absence of definite advances, elements of knowledge on the population dynamics or the formation of volatile compounds can be useful for the winemaker: the studies of V. RENOUF et col., II.62, Faculty of Bordeaux and more experimental, those of P. TAILLANDIER et col. , II.04, Laboratory of Chemical Engineering of Toulouse. It is the evolution of early diagnostic methods that could offer a concrete tool for the control of the proliferation of Brettanomyces, knowing that the traditional culture in a Petri dish remains slow (one week). This problem was addressed in the workshop at the end of the day.

Quantitative PCR presented by J.COULON ( DELAHERCHE et col. , II.21, Faculty of Bordeaux) offers a rapid detection (2 days), which is early (<10 UFC/ml) and specific. A transferable method for all classic laboratories is flow cytometry (V. GERBAUX, II.26, ITV of Beaune). Based on laser lighting coupled with a computer, the result is obtained in 15 minutes, starting at a population size of 2000 cells/ml but it does not offer a specific identification of the yeasts. A pragmatic and not expensive method, flow cytometry could permit a regular follow up of each tank, once the alcoholic fermentation is completed, and is complementary to other more refined methods of analysis. In all cases, the importance of the sampling being at the bottom of the tank is emphasized, for the reliability of the results.

The second problem of interest for the industry : the yield of sugar/alcohol of Saccharomyces cerevisiae which varies only very slightly between strains (one can obtain at most a variability of 0.5% Vol). A significantly lower yield would however be a solution for the high alcoholic degrees, not only in terms of public health but also for balanced taste. M. EHSANI et col. (II.22, INRA Montpellier and Lallemand) explores a genetic approach which entails the deviation of metabolic pathways towards other products than sugar, all without affecting the yeast physiology and the organoleptic qualities of the wine. Amongst the few possible paths, it is that of glycerol which is retained. The accumulation of acetoine results determinate (by guided autogenesis), the team of the INRA obtained a strain which demonstrated a yield of alcohol of 17% less than a standard strain, with a production of glycerol in the order of 25g/L. A validation on natural musts would permit for the evaluation of the pertinence of these options and the impact of such a level of glycerol in the final wine (quid of its microbiological stability as was highlighted by M. STREHAIANO).

With regards to yeasts, the original studies by R.GONZALEZ et col. (II.30, Institute of Industrial Fermentation of Madrid, Spain) about autophagy which precedes the autolysis of the yeast, are of interest. This phase of autodigestion of the cytoplasm is a response of the yeast in order to extend its survival in an environment where the nutrients have been exhausted. Identified during

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To be observed also are the taxonomic evolutions of Bayanus which have kept the ink flowing for researchers (H. NGUYEN et col., II.52, CLIB) who noted a very close relationship to Uvarum. The more practical studies presented during the workshop were notably those of P. MARULLO et col. (II.43, Faculty of Bordeaux, LAFFORT) which put forward a temperature resistance genetic marker of the yeast, implied for the improving of current commercial strains (Only 4 strains of 9 complete the alcoholic fermentation at 28°C !).

The possibilities of mixed inoculations are also addressed with a promising coupling of Hanseniaspora occidentalis et S. cerevisiae for the de-malication (up to 70%) of dry white wines ( A. POULARD et col., II.54 , ITV) but also with the coupling of Torulaspora delbrueckii et S. cerevisiae which significantly reduces (up to 55%) the production of volatile acidity in the fermentation of botrytized musts (M. BELY et col., II.07, Faculté of Bordeaux).

In that which concerns bacteria, we retain that the studies of M. RITT et col. (II.64, ENSBANA) are a significant advancement in the understanding of the nutrition modes of O. oeni after alcoholic fermentation in an environment which is poor in nutrients. These put forward specific assimilation mechanisms of nitrogen compounds with the intervention of extracellular proteases and of a particular peptidase (PepI). The nature of the peptides present in the environment, influence the expression of genes encoding the peptidases. Consequently, a positive impact of the peptides of yeast origin on the growth of bacteria is observed.

P. LUCAS et col. (II.40-41, Faculty of Bordeaux) are interested in the identification and the enumeration of lactic bacteria which produce biogenic amines. The updating of a quantitative PCR technique permitted the evaluation to 97% the wines containing strains endowed with histidine decarboxylase (producers of histamine) on a sample of 264 red wines. These strains are present from the start of the vinification and multiply during the MLF. This is furthermore favoured when kept on lies. Finally, these studies confirm the efficacy of commercial yeasts to control these populations and their production of biogenic amines.

The theme of microbiology was closed on an original subject: the cellular aggregation of O. Oeni BR10 as a defense strategy in a stressful environment (F. FRACHETTI, II.76, University of Verona, Italy). A complex polymeric matrix enclosing the cells would be a wonderful protective environment for their survival and would provide an extra adaptation phase in the alcohol and pH conditions characteristic of the wine.

Theme V- Sensorial Analysis and Consumer Interface After a brief return on consumer health with the detection of moulds responsible for the production of OTA by quantitative PCR (A.ATOUI, V.27, ENSAT of Toulouse, EVIALYS), taste and olfactive perception was in the spotlight. We will learn that laser impacts at the bottom of the glass channel the degassing of sparkling wines and neutralizes the perception variability linked with its content: what a good intention, that of taming the bubble! (MARCHAL et col. , V.23, University of Reims). The objective evaluation of the organoleptic characters is also a question for red wines. One of the major difficulties is the measurement of the taste dimensions linked to the presence of tannins: astringency and bitterness. An electronic tongue, developed in Russia, comprises 15 potentiometric sensors. Applied to wine, it reveal some real perspectives for a rapid assessment and quantification of the tannin profile (H. FONTOIN ET col., V.13, Faculty of Bordeaux et LAFFORT). The tool permits the discrimination of the different concentration of tannins on model solutions but also of different grape varieties and this all with a good repeatability.

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3rd and final day Theme IV : Chemistry, biochemistry and wine constituents The themes are very diverse: polysaccharides, phenolic compounds, aromatic compounds, oxygen… The guiding leads are relatively diffused but we retain that the evolution of the analysis methods confirm the tendency towards a forevermore refined and reasoned oenology: the IRTF (infrared spectrometry) for the dosing of mannoproteins, arabinogalactanes and rhamnogalacturonanes ( J.C. BOULET et col. , IV.07, INRA Montpellier) ; or also the first quantitifications of ethyl bridged flavan-3-ols (J. DRINKINE et col., IV.40, Faculty of Bordeaux and Oregon State University, USA)… These flavan-3-ols, which are responsible for the astringency of wines, also are the subject of fundamental studies for the better comprehension of their interaction with the glycosylated proteins of saliva. (C.PASCAL, IV.34, INRA Montpellier). These studies extend even to the point of introducing a gene encoding the production of human saliva in yeast.

The aromatic compounds occupy a notable position in this morning. The trials of the characterization of the fruity notes in evolved red wines (A. ESCUDERO, IV.45, Portugal) confirm the importance of matrix effects and propose some paths that merit further investigation: the negative effect of ethanol on fruity notes, the synergetic positive interactions between IBMP and hexanol but also between the norisoprenoids (β-damascenone et β-ionone), esters and DMS (Dimethyl sulfur). DMS, an aroma that forms during the bottle aging and associated with truffle odours, seems to be a key in the positive evolution of a wine, notably as an exhauster of aromas. A better understanding of the viticultural and oenological factors which favour the potential DMS (PDMS) is the objective of the studies on Manseng of L. DAGAN et col. (IV.37, ITV et INRA Montpellier).

The thiol aromas are not forgotten where with a aromatic cartography of sauvignons we learn that on 50 wines of the world, the wines of Marlborough in New Zealand are distinguished by their very high concentration of 3-MH and MH (L. NICOLAU, IV.33, University of Auckland and Faculty of Bordeaux). Closer to our European vineyards, the aromatic secret of wines made from noble rot affected grapes is the subject of a communication which agreeably ends this symposium (E. SARRAZIN, IV.39, Faculty of Bordeaux). Accordingly, the compounds which explain the profile of these wines are identified, they are furanones and phenylacetaldehydes, at concentrations much higher than those which are characteristic of dry white wines, but likewise are three new volatile thiols (sulfanyl). In addition, B. cinerea seems to play a key role, not only in favouring the desiccation of the berries (concentration of the compounds) but also in the direct production of new compounds.

Conclusion Faced with such a diversity and abundance of studies, the words of the Dean, Donèche seem to be perfectly evocative: “The miracle of oenology has been accomplished”. The entirety of the information could not be re-transcribed in this short article… but we hope that it will spark the scientific curiosity of everyone. If some strong ideas should have been made clear in this symposium, they would be: - The evolution of the analysis methods providing tools which are continually more precise and sensitive for researchers and those practicing, - The inevitable role of genetic techniques in the improvement not only of the vegetal material but also that of the microorganisms used in oenology, - The immensity of the fields to be explored which regard the comprehension of aromas and phenolic compounds. Finally, the taking into account of technical problems with strong commercial implications is not unconventional and demonstrates the good interaction between the scientific community and the industry.

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