Why does your wine smell like…“barnyard”? If you ever encounter this descriptor, you’re most likely tasting the effects of Brettanomyces. A genus of yeast, Brettanomyces (pronounced BRETT-ANNE-OH-MY-SEES), or simply “brett,” can grow both aerobically and anaerobically in a wine, leaving a series of flavor compounds in its wake. Brett can find its way into a wine by way of unclean equipment, contaminated barrels, fruit flies and other vectors. Brett’s influence can be tempered with sulfur additions and sterile filtration, although once in bottle, brett can continue to multiply as a wine ages. Tasting notes associated with brett are some of the most colorful, ranging from “sweaty saddle” to “bacon” to “Band-aid.” While brett can be traced in white wines, it is almost exclusively associated with reds. Brett is perhaps the most controversial wine flaw because, unlike cork taint or premature oxidation, not everybody perceives it as a negative. Some of the great wines of the world are not absent of brett, and some would even argue their character in part derives from its presence. While brett may prove particularly deleterious in a fine Burgundy , just south in the Rhône it may be considered typical and even welcome. The same holds true for beer. While in most circumstances brett proves a nuisance for brewers, some styles – such as lambic and gueuze – rely upon the inoculation of brett as part of the beer’s recipe. So, when is brett “brettastic” rather than tragic? The exact threshold when brett crosses from a contributor to complexity to a fatal flaw cannot be defined. Instead, the answer lies in the palate of each and every taster.