Have you heard people talking about 'brett' in wine and are confused about whether it's good or bad?
What are the benefits of brett? – ask Decanter
Jim Stokes, New Zealand, asks: Could you please explain when brett is a good thing in a wine and also when it is a bad thing?
Justin Howard-Sneyd MW replies: Brett is the abbreviation of a spoilage yeast family called brettanomyces, of which there are at least four strains (B. lambicus being important in making lambic beers).
As the yeast metabolises sugars left in the wine, or on the barrel, it produces aromas such as 4-ethylphenol (which smells of bandaids/plasters), 4-ethylguaiacol (cloves and smoked bacon) and isovaleric acid (leather and cheese).
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The extent to which having notes of brett in wine is desirable is a matter of personal opinion, rather than a fact.
While many (often New World) winemakers view any hint of brett characteristics as evidence of spoilage, others with a more traditional heritage accept – and appreciate – low levels as adding complexity and personality in the wine.
If the wine is filtered so as to remove the brett yeast completely, then no further aromas will develop, and the wine can be stable; however, unfiltered wines with brett can rapidly evolve and lose their fruit.
Justin Howard-Sneyd MW is a wine consultant and winemaker.