G. de Revel

Interactions between Brettanomyces bruxellensis and other yeast species during the initial stages of winemaking

Aims:  Wine is the product of complex interactions between yeasts and bacteria in grape must. Amongst yeast populations, two groups can be distinguished. The first, named non‐Saccharomyces (NS), colonizes, with many other micro‐organisms, the surface of grape berries. In the past, NS yeasts were primarily considered as spoilage micro‐organisms. However, recent studies have established a positive contribution of certain NS yeasts to wine quality. Amongst the group of NS yeasts, Brettanomyces bruxellensis, which is not prevalent on wine grapes, plays an important part in the evolution of wine aroma. Some of their secondary metabolites, namely volatile phenols, are responsible for wine spoilage. The other group contributing to wine aroma, which is also the main agent of alcoholic fermentation (AF), is composed of Saccharomyces species. The fermenting must is a complex microbial ecosystem where numerous yeast strains grow and die according to their adaptation to the medium. Yeast–yeast interactions occur during winemaking right from the onset of AF. The aim of this study was to describe the interactions between B. bruxellensis, other NS and Saccharomyces cerevisiae during laboratory and practical scale winemaking.

Growth and volatile compound production by Brettanomyces/Dekkera bruxellensis in red wine.

Aims:  Brettanomyces/Dekkera bruxellensis is a particularly troublesome wine spoilage yeast. This work was aimed at characterizing its behaviour in terms of growth and volatile compound production in red wine.

Methionine catabolism and production of volatile sulphur compounds by Œnococcus œni

Aims:  During malolactic fermentation (MLF), the secondary metabolisms of lactic acid bacteria (LAB) contribute to the organoleptic modification of wine. To understand the contribution of MLF, we evaluated the capacity of various wine LAB to metabolize methionine.

Determination of lactic acid bacteria producing biogenic amines in wine by quantitative PCR methods

Aims:  To develop rapid methods allowing enumeration of lactic acid bacteria producing biogenic amines in wines and to analyse wine samples by the methods.

Role of botrytized grape micro-organisms in SO2 binding phenomena.

J.‐C. BARBE, G. DE REVEL, A. JOYEUX, A. BERTRAND AND A. LONVAUD‐FUNEL. 2001.

Vanillin production from simple phenols by wine-associated lactic acid bacteria.

Aims:  The ability of lactic acid bacteria (LAB) to metabolize certain phenolic precursors to vanillin was investigated.

Pathways that produce volatile sulphur compounds from methionine in Oenococcus oeni

Aims:  Determination of pathways involved in synthesis of volatile sulphur compounds (VSC) from methionine by Oenococcus oeni isolated from wine.

Explicit Sensory Training Improves the Olfactory Sensitivity of Wine Experts

Wine quality is first assessed by experts who evaluate the sensory characteristics of the product using sensory skills. Several studies have shown considerable variation in chemosensory human capacities, including wine tasting experts. Some of them show high olfactory detection thresholds for some key compounds of wine. In addition, several authors have observed an induction of sensitivity in subjects with odor-specific hyposmia and increased sensitivity in persons without specific olfactory disorders after repeated exposure to a substance or practice fragrance smell tests. Given these observations, adapted training for professionals in the wine industry may be appropriate. On this basis, we tested a simple sensory training session, that is to say repeated short-term exposures to odorous wine key compounds, with the hope of improving the detection capabilities of wine professionals who need it. Our results show that the sensitivity of these experts can be changed: the olfactory detection thresholds are reduced in the experts trained. This improvement was limited to the odorant used in the training: learning was not generalized but was odorant specific.

Masking of Several Olfactory Notes by Infra-threshold Concentrations of 2,4,6-Trichloroanisole

IntroductionAmong wine defects, 2,4,6-trichloroanisole has a specific impact on wine perception. In addition to giving to the wine an unpleasant odor, 2,4,6-trichloroanisole has a masking effect on notes. In this study, the specificity and efficacy of the masking effect of 2,4,6-trichloroanisole was tested at infra- and supra-threshold concentrations. A simplified model of a binary mixture was also studied for in-depth analysis of this phenomenon.MethodsTechniques used included sensory analysis (odor profiling), psychophysical tests (threshold measurement and triangle test), chemical analyses (GC-MS), and a mono/dichorhinic stimulation paradigm, to test the hypothesis of peripheral interaction.ResultsThe results revealed that TCA had a masking effect on a range of aromatic notes, even at infra-threshold concentrations. However, they also showed counteraction of odorant specificity by 2,4,6-trichloroanisole. The origin of this masking effect was also discussed. The results suggested that this interaction can be assumed to take place at receptor level.ConclusionThis study provided experimental confirmation of the widespread idea that constituents in non-perceptible concentrations influence the perceived quality of mixtures of odorous compounds.ImplicationsMoreover, this type of olfactory model may improve our understanding of combinatorial olfactory encoding at the peripheral level.