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Mar 6, 2007 05:02 PM

The nefarious effect of subthreshold TCA

Was clearing some files off my hard drive and ran across this message, which I'd saved and which may have originally been posted to the old Wine Lover's Discussion Group. Since googling quotes from it turns up zero hits, I assume it has vanished into the Internet ether. That would be a shame, because it makes an important point about the nefarious effect of 2,4,6-trichloroanisole (aka TCA), the chief cause of cork taint.

Date: 12-Oct-2004 15:11
Author: Everett Bandman
Subject: The short answer is that no one really knows......
I am a Food Scientist at University of California at Davis and the answer to your question on how humans perceive TCA and why it effects our sense of taste and smell of wines is not really understood. We did an anecdotal experiment in our "academic" tasting group where we tasted blind a stelvin finished white wine that was doctored with varying levels of TCA. One of the most interesting results was that even at subthreshold levels of TCA for individual tasters (which of course vary), the palate impression of the wine was clearly altered. The most dramatic effect was on perceived acidity. At subthreshold levels where no one could smell TCA, the wine tasted flat. If you taste clearly tainted wines, this effect is pretty clear to most. It was surprising however to see the effect in the absence of any preceived TCA. Given the prevalence of subthreshold TCA in our wines, think about how many bleh wines have been dismissed, which may simply have been slightly tainted.

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  1. Ah, Everett . . .

    2,4,6-trichloroanisole is measured inparts per TRILLION -- even so, there clearly IS "sub-threshold" contamination. At very low levels, TCA will destroy a wine, yet so subtly that often there is no way of knowing, unless one has a second bottle of the same wine handy. The wine does indeed seem "flat"; the fruit seems "dull," or just AWOL. Yet a second bottle may be light-year's apart, *very* aromatic, *very* fruity and flavorful.

    Even though I consider myself fairly sensitive to TCA, this is why -- as a wine judge -- I will always defer to anyone else on the panel who may think the wine is corked, OR if the wine is unexpectedly flat/dull . . . we'll definitely ask that a second bottle be opened and poured.

    1. A follow-up question: Before dismissing a bleh wine, is there any way to determine -- short of running a chemical analysis or opening a second (hopefully untainted) bottle -- whether it is slightly tainted or just innately flawed?

      4 Replies
      1. re: carswell

        Well, I would respectfully suggest that "slightly tainted" IS "innately flawed," because the wine is decidedly "off" even at very low levels of TCA. The problem is not between "slightly tainted" and "innately flawed," as I see it, but rather it's more like an old Clairol commercial ("Does she, or doesn't she?"). "Is it, or isn't it?" is the question. Is the wine muted, dull and flat because that's simply the wine, period? OR, it is muted, dull and flat due to a low-level TCA contamination?

        Sadly, there is no hairdresser to ask, no way to tell for sure, short of either running a chemical analysis or opening a second bottle . . . at least no way that I know of.

        1. re: zin1953

          I chose my words carefully and considered both intrinsically and inherently before settling on innately. Innate because I'm distinguishing between a flaw that is present in the wine from before bottling, from "birth" as it were (the *nat* being the same root as in "nativity"), in contrast to an extraneous flaw, an introduced flaw, which TCA contamination by definition is.

          Seems like we've uncovered a marketing opportunity. If someone invented taint strips that, in the presence of minute amounts of TCA, changed colour like pH strips do, I'd be a buyer.

          1. re: Junie D

            Somehow, I can't see getting a glass of wine too close to my Bulldogs, even if they could detect TCA, I don't think that my wine would be drinkable, after they slobbered all over it! ;-}


        2. First, thanks to Carswell for posting those old notes. TCA is such a problem for the wine industry, that most will do all that they can to rid themselves of it. As Carswell noted, "Given the prevalence of subthreshold TCA in our wines, think about how many bleh wines have been dismissed, which may simply have been slightly tainted." Yes, how many wines are passed over as being "blah," when another bottle would possibly have sold many more to those consumers?

          Being supersensitive to TCA, I usually can nail it right off. However, I've had a couple exposures lately, where I had to pass the glass to my wife for a "second-opinion." As stated, the acidity and dull fruit are often key. It also helps if one has a taste memory of that particular wine. If it's a new varietal, a new region, or a new producer, one really has to delve deeply into it, to decide what the real problem is.

          Stelvin, or similar, seems to be one answer, and it will be interesting to see how these types of closures work out for wines made for long-term storage. The data seems to be coming in, and producers are starting to take notice. Not sure where the development of alternative closures will lead, but we should all benefit. That said, I will miss the cork, but will get over it.

          I was returning about 1 btl./case of my "house white," until they went to Stelvin. Over the last 3 years, I have yet to return 1 btl. and that's probably about 25 cases total.

          Again, thanks for the post,

          1. In Austria they call this slight amount of taint (i.e., when it just robs the wine of any fruit notes) as "Schleich Kork", or, "sneaky cork". It is the vintners worst fear as then the wine just seems no good, as opposed to being obviously flawed.