Brettanomyces bruxellensis

Brettanomyces bruxellensis (the anamorph of Dekkera bruxellensis) is a yeast native to the Senne valley near Brussels, Belgium.

Beer production
Brettanomyces bruxellensis plays a key role in the spontaneous fermentation of typical Belgian beer styles such as Lambic, Gueuze or Kriek.

Wine production
In the wine industry, Brettanomyces bruxellensis is considered a spoilage yeast and is often referred to as brett. Its metabolic products can impart "sweaty saddle leather", "barnyard", "burnt plastic" or "band-aid" aromas to wine. Some winemakers in France, and occasionally elsewhere, consider it a desirable addition to wine, but New World vintners generally consider it a defect. Some authorities consider brett to be responsible for 90% of the spoilage problems in premium red wines.

One defense against brett is to limit potential sources of contamination. It occurs more commonly in some vineyards than others, so producers can avoid purchasing grapes from such sources. Used wine barrels purchased from other vintners are another common source. Some producers sanitize used barrels with ozone. Others steam or soak them for many hours in very hot water ,or wash them with either citric acid or peroxycarbonate.

If wine becomes contaminated by brett, some vintners sterile filter it, add SO2, or treat it with dimethyl dicarbonate. Both knowledge and experience are considered helpful in avoiding brett and the problems it can cause.