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The cellar environment harbours a consortium of microorganisms on the material surfaces and in the air. Among these microorganisms, the spoilage yeast Brettanomyces bruxellensis can colonise surfaces due to its specific bioadhesive properties. In this study, air and surface samples were collected in several wineries during the winter period. B. bruxellensis was detected in the cellar environment either in the air or on the surfaces of various materials, including in tartaric acid precipitates. Difficult-to-clean tank equipment (taps, wall angles, valves) were identified as critical areas where B. bruxellensis was frequently detected. To confirm that surfaces contaminated by B. bruxellensis could be involved in wine contamination, yeast growth and volatile phenol production were monitored in wine in contact with stainless steel harbouring biofilms. The presence of bioadherent cells and biofilms in contact with the wine resulted in significant cell release into the wine, leading to population growth and the production of volatile phenols at concentrations above the olfactory detection threshold. This study demonstrates the possibility of wine spoilage by resident and adherent populations of B. bruxellensis and confirms the need to pay special attention to the hygiene of hard-to-reach areas such as valves.

Since the 1980s, red winemaking practice has been geared towards wines rich in phenolic compounds. However, this phenolic material is not always stabilized and conserved, and many finished wines in bottle do not match up to their initial, and wished-for, character. Inadequate aging in relation to the extracted compounds, and the presence of certain colloids, contribute to poor stabilization of the phenolic fraction, which is not sufficiently taken into account during the different stages before bottling.

Aims: To study the impact of soil-type, grapevine variety and rootstock on grape yield and wine quality in prestigious estates located in the Bordeaux area (France). Methods and results: High-resolution soil maps (scale: 1/3000th) were created for seven prestigious red wine-producing estates in Bordeaux, covering a total area of approximately 400 ha. Soil-type, rootstocks and grapevine varieties were recorded for each vineyard block. A Quality Index was created by considering the destination of the grapes produced in each block, whether they were integrated in the first, the second or the third quality wine produced by the estate. Quality Index was averaged over five vintages. Yield was also measured for each vineyard block and averaged over five vintages. PEYROSOL (gravelly soil) was the most frequent soil-type in these estates (45% of the total mapped area). Soils with temporary waterlogging (REDOXISOL), heavy clay soils (PLANOSOL) and sandy-gravelly soils (BRUNISOL) covered around 10% of the mapped area each. Highest quality was obtained on PLANOSOLS, ARENOSOLS (sandy soils), BRUNISOLS and PEYROSOLS. Quality was low on COLLUVIOSOLS (deep soils on colluvium), LUVISOLS (leached acidic soils) and REDUCTISOLS (soils with permanent waterlogging). Cabernet-Sauvignon was the dominant grapevine variety (59% of the mapped area), followed by Merlot (32%), Cabernet franc (8%) and Petit Verdot (1%). On average, the Quality Index was higher for Cabernet-Sauvignon and Merlot compared with Cabernet franc and Petit Verdot. Riparia Gloire de Montpellier (RGM) was by far the most used rootstock. It covered 45% of the mapped area. Including 3309C and 420A, these three rootstocks covered 75% of the total acreage planted in these estates. Highest quality wine was produced with 420A, RGM, 3309C and Gravesac. Highest yields were obtained with 161-49C, 101-14 MG, RGM, SO4 and 420A. Conclusions: Soil, grapevine variety and rootstock have a major impact on yield and wine quality in prestigious Bordeaux wine producing estates. Significance and impact of the study: Assessment of a Quality Index by soil-type, cultivar and rootstock can indicate which combinations of soiltype, cultivar and rootstock would best optimise quality performance in Bordeaux vineyards.

Aims: This work reviews the latest knowledge concerning the role of Brettanomyces bruxellensis in red wine alteration. Results and conclusion: The origin of this yeast species and its place in the wine microbial consortium are discussed as well as microbial equilibriums with the other species, notably Saccharomyces cerevisiae and lactic acid bacteria. As a consequence, fermentations are described as key steps in Brettanomyces development management. Furthermore, the influence of ageing through the use of traditional winemaking practices is explained. Significance and impact of study: Finally, this paper emphases the need for a better understanding of chemical and microbial analysis together in order to better control this undesirable yeast and prevent the production of volatile phenols.

Aims: Microorganisms play an important role in winemaking. Most of their metabolisms are beneficial to the wine quality but several species have spoilage effects. Microbiological knowledge are crucial for improving species and strains identification and avoiding contamination by spoilage agents. Our objective was to follow wine microbial consortia at each stage of the process from grapes to bottles, and also on cellar equipment surface: barrels for the yeast analysis and tanks for the bacteria analysis. Methods and results: For a global microbial monitoring, molecular tools are particularly efficient. We chose the PCR-DGGE for direct analyses without cultivation step. We used the rpoΒ gene as target for the bacteria, and the 26S rRNA gene for the yeast. Species inventories were made during the whole winemaking process, which had never been done before. Conclusion: From the grape surface to storage in bottles, the microbial diversity decreased. Only the most resistant species were able to survive to the ethanol, SO2, low oxygen and low pH constraints. Among them, Pediococcus parvulus for the bacteria and Brettanomyces bruxellensis for the yeast were the most resistant. Significance and impact of study: The use of a molecular method independent of the culture stage of the microorganisms like the PCRDGGE has allowed to have a more exhaustive vision of the diversity of the bacteria and yeasts species and to follow their evolution during the winemaking and in the cellar environment . These follow-ups could be extended to other estates in order to study the causes and the consequences of certain variations. The detection of these two prejudicial species was an argument for the PCR-DGGE approach in wine microbial studies.

Yeast, bacteria, species and strains play a key role in the winemaking process by producing metabolites, which determine wine sensorial qualities. Therefore microbial population enumeration, species identification and strain discrimination from berry surface at harvest to storage in bottle are fundamental. The microbial diversity and significance of its variation according to the estate localization have not really been thoroughly considered in literature. This is the focus of this work. That should be of great interest because the spontaneous microbial population dynamics associated with a wine producing estate provide information on what might be considered as the method to obtain specific terroir typed wine. The both use of conventional microbiological methods like microbial population enumeration on nutritive selective media and efficient molecular tools of species identification like PCR-RFLP for yeasts and PCR-DGGE for bacteria and strains discrimination have demonstrated significant microbial differences between different estates localized in the Bordeaux area. Theses results appeared very interesting since certain microbial species are clearly specific of certain estates, in particular the bacterium Pediococcus parvulus, and also some strains of Saccharomyces cerevisiae, of Oenococcus oeni and Brettanomyces bruxellensis. Within an estate this specificity persists from one year to another. These differences observed suggest that the indigenous winemaking processes can contribute to the specificity of the wines produced on the various estates.. That concludes to the hypothesis of a microbial part in wines speficities.

The alcoholic fermentation is a crucial winemaking step. Its failure is problematic. In spite of several studies to understand and elucidate these problems wine global microbial ecology has never been considered. Using conventional microbiological methods and sensitive molecular tools we monitored the alcoholic fermentations of different red grape varieties in several cellars located in Bordeaux area. These observations were made during three successive vintages in different oenological conditions. The effect of the addition of commercial active dried yeast and of initial cold maceration was studied. All these factors were compiled and their effects on microbial changes were investigated. Some of them acted directly on the microbial population of berries surface at the harvest time and should have impact on alcoholic fermentation. They could modify the microbial changes which in some cases could lead to sluggish fermentation. In these cases, we focused on the Brettanomyces bruxellensis spoilage problem. The risk of further contamination was discussed according to the alcoholic fermentation development.

Winemaking is based on complex microbial interactions. They result in alcoholic and malolactic fermentation. In some cases undesirable micro-organisms pass beyond a limit and become prejudicial to wine quality. It is particularly the case of Brettanomyces bruxellensis which produces volatile phenols. Most of wine microbial studies have been focused on only one species and that can lead to incomplete and biased results by neglecting possible interactions between the populations. The aim of this study was to obtain a global survey of wine microflora and its quantitative and qualitative changes during the malolactic fermentation, the last microbial intervention before sulphur dioxide addition. The results were obtained by chemical wine analysis, conventional microbiological methods and molecular tools for microbial identification (PCR-ITS-RFLP, PCR-DGGE). In this study, conducted under cellar scale conditions, several oenological parameters were considered: two different cellars, three grape varieties, MLF in tank or in barrels, use of malolactic starters or indigenous flora. Interactions appeared, mainly between Oenococcus oeni and B. bruxellensis, but also between O. oeni strains. Some explanations are suggested and further investigations are proposed.

This study aims to understand the effect on micro-organism of racking when the wine is aged in barrels. According to the kind of micro-organism, the effects are different. Bacteria are stimulated by oxygen and their population increases. Yeasts are concentrated to the bottom of the barrel. Between two successive racking a yeast population gradient was established. Yeast cells which are larger and heavier than bacteria cells and they are deposited on the barrel bottom with other wine micro-particles. In some cases, the yeast population at the bottom was more than thousand times than at the wine surface. Moreover, the species identified at different heights in the barrel were different. Saccharomyces cerevisiae was the main yeast detected at the surface, whereas Brettanomyces bruxellensis was the main yeast lees. After racking yeast population decreases because they are eliminated with the lees during the operation. Among them, Brettanomyces bruxellensis was the majority. Since they are able to produce volatile phenols, their preservation in the barrel can lead to the alteration of the wine. Indeed, the ability of the lees to produce volatile phenols was clearly established. The importance of regular racking for microbial wine stabilization is evident. The risks of «sur lies» wine aging and sticking’s operations are underlined.