Brettanomyces
/bret-an-oh-MY-seez/A spoilage yeast producing barnyard and medicinal aromas.
Full Definition
Brettanomyces is a genus of yeast that produces 4-ethylphenol and 4-ethylguaiacol, compounds smelling of barnyard, horse sweat, Band-Aid, and smoke. It ferments residual sugars in finished wine and lives in wood barrels. Controversial: some regions traditionally accept low levels as terroir character; modern winemaking typically strives for brett-free wines.