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Dear Dr. Vinny,

I'm in a wine appreciation course in which my instructor insists that the cause of "cork taint" is due to a yeast called brettanomyces. However, I was under the impression that cork taint and brettanomyces were considered as two distinct problems, each associated with their own causes and distinctive aromas. His response to my question was "most winemakers agree that most of the problems called 'cork taint' are from brettanomyces." Can you help to resolve our argument?

—Daniel M., Grand Forks, N.D.

Dear Daniel,

I'll be happy to. And you're correct that cork taint and brettanomyces are two different things. For starters, one is a chemical compound and the other is a yeast.

A wine afflicted by cork taint—a "corked" or "corky" wine—is suffering from a compound called 2,4,6-trichloroanisol, or TCA, which results in musty, dank or moldy notes. It reminds many folks of wet cardboard, damp cement or the smell of old books. TCA is created by an interaction of mold, chlorine and phenols (which are organic compounds found in all plants). The compound can develop in corks themselves, which is why they are often linked to TCA. But it can be difficult to pinpoint a source of TCA, since it can also originate in cardboard cases or wooden pallets. Indeed, entire wineries have been contaminated with it.

Brettanomyces, or "brett," is a yeast, and since it can ruin a wine, it's generally considered a spoilage yeast. At low concentrations, some people find that it can add a pleasantly spicy component to a wine. At higher levels, it gives wine a barnyard, horse-stall or metallic note. Brett can develop at practically any stage of production, but it's more likely to be found in a winery than in a vineyard, often hiding out in barrels. When it takes residence in a cellar, it can be really tricky to get rid of it.

Thresholds of perception (and tolerance) for TCA and brett vary, so there are some people who don't notice these flaws, others who might mistake one for the other, and more sensitive tasters who find wines marked by these flaws undrinkable.

I have yet to meet a winemaker that believes TCA comes from brett, but your instructor is welcome to e-mail me if he or she knows of any.

—Dr. Vinny

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