Brettanomyces
Study of red wine contamination by Brettanomyces yeast
Conclusions
We have known for a long time about the presence of Brettanomyces yeast in wine ; however, the damage it can do has only recently come to light (Hereszyn's studies in 1986). This yeast has been deteriorating wine for a long time; it certainly didn't wait for micro-oxygenation to be invented to make its presence felt. The results of our study show that Brettanomyces can develop in the presence of, but also in total absence of oxygen.
What is interesting to note is the fact that weak doses of oxygen have no significant effect on Brettanomyces growth, and only excessive doses encourage its development. It seems obvious that one should be more wary of Brettanomyces than of a properly carried out micro-oxygenation; it is dangerous to think that only wines upon which micro-oxygenation has been carried out are subject to contamination. In fact, oxygenation methods, like racking or cliqueur usage would appear more risky and can considerably enhance Brettanomyces growth. The risk of contamination is even higher with racking, through transferring and pumping the wine.
From a gustatory point of view, it seems that the flaws due to the presence of Brettanomyces are first perceived by the nose, but do not bother the taster. However, from the stationary phase onwards, the olfactory "flaws" are predominant, and become apparent when tasting. At this point the sensations are particularly unpleasant.
We have also noted that the presence of this yeast in wine considerably diminishes the effect of oxygen, whatever the type of elevage.
This is why regular monitoring of all wines and early detection of Brettanomyces presence before the stationary phase are essential, and can save a wine that otherwise would have lost all its aromatic qualities. Unfortunately, the solutions available today are costly and very often testing is carried out when the defect is perceptible (too late). Only residual populations can be detected at this stage.
Gilis J-F., Cabri C. et Ducournau P.
A joint study carried out by the Oenodev Research & Development Team, along with Professor Stréhiano's Fermentation and Bioreactor Team at the ENSIACET* at Toulouse.
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