How to determine your TCA sensitivity threshhold

While we are at it, does anyone know of a lab that will analyse wine samples for TCA contamination for a reasonable price?

From time to time, I run into wine that feels contaminated to me but not to other folk. Thus, would like to test them to see whether the TCA sensation is on my nose and tongue or only in my head.

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I dunno. If I was still (blissfully) unaware of my TCA sensitivity, would I be any less happy than I am today? Sounds a bit like the old saw of the tree in the forest (or was that the Pope in the woods?).

Good question. I'd try a local hobby shop that deals in chemistry sets (if any still exist) or a good pharmacy. As a last resort, if you strike out with that approach, send me an email with a mailing address and I'll send you a bit (it's not trivial for me to send chemicals to private addresses, but it can be done).

Serial dilution is a staple of molecular biology labs, Leo. All it takes is an accurate measuring device for liquid volume. I'd do my dilutions by a factor of 10, BTW: twofold is overkill. I'd start with a 10 ppm solution and make 5 tenfold dilutions, giving you a concentration range of 10 ppm down 0.1 ppb. That should cover the full range of physiological response. Get yourself a 10 mL volumetric and a

100 mL volumetric.

That's the general idea; I'd just change the dilution factor and volumes. Keep in mind that you need all of about 10 microliters of each sample for your test.

Don't sip it. Just smell it. The "taste" of TCA is almost entirely due to retronasal olfaction anyway, so the smell is all you need to focus on. That also removes the need for USP grade TCA, which would cost you

1000 times as much as reagent grade. Also keep in mind when searching for TCA that it also is the abbreviation for trichloroacetic acid and you _do not_ want to conduct your trials with that!

HTH Mark Lipton

As far as one's sensitivity to TCA goes, it is an interesting situation/problem. Both my wife, and I, are very sensitive to it. We usually agree 100% on its existance. Maybe because of a great olfactoray ability, I can often pick it up, when a waiter passes by with wines b-t-g in a restaurant filled with other odors. However, there are times, that I am not 100% sure and ask for her validation. If I have detected it, she has always confirmed it.

On the palete, I usually find a higher concentration of acid, and very muted fruit. This is most often used as the confirmation to the nasal perceptions. This is less than perfect, if I do not have some reference for the particular wine. It also seems better suited for whites, than for reds. As many reds have a dusky, musty, earthy quality, I have to really concentrate with some of them to make sure that it is not "Rutherford Dust," or similar, that I am experiencing.

For a purely scientific standpoint, I think that Mark Lipton covered most bases.

As a total side-note, if I encounter a bottle, that I feel is "corked" at a tasting, I offer samples of it to my guests, so that they will come to know the characteristics next time.

I've got a bottle of Talbot Chard to return, because of TCA. This was one bottle out of six from the local Costco, plus one bottle of Meursault from K&L, again, one of six. Fortunately, I've only had a few reds, over the years, and unfortunately, most were acquired too long before to think about returning

- imagine finding the receipt for a bottle of whatever, six years down the pike.

Hunt

It has become second nature to me, when I first remove the cork from a bottle of wine, to smell the bottle. My rule of thumb is that, if I think I detect TCA, the bottle is probably corked. I will smell it several times over the next few seconds and often find that the smell has blown off to the point that I can no longer smell it. This may be at least partially due to some desensitization of my sense of smell. The next step is to pour some into a glass, swirl it around, and smell it again. If there is still uncertainty, I will take a sip and, if still in doubt, swallow a small amount. A corked wine will almost always be obvious on the finish.

I once opened a bottle of Sauvugnon Blanc, a label and vintage that I was familiar with. Unlike earlier experiences, this bottle seemed to have no fruit flavor. I tried and tried, but could never detect TCA, but there continued to be that lack of fruit. If it had been a wine that I was not familiar with, I would have concluded that it was just a lousy wine. I ended up taking the bottle to a respected wine professional who poured, swirled, sniffed, and tasted. For a while he was genuinely puzzled. Suddenly he had that aha! moment and pronounced the bottle corked. I respected his judgment but, hard as I might try, I could never smell TCA in that bottle.

I don't know that I have any opinion on the relative rates of corked wine between whites and reds. I agree with Hunt on the difficulties associated with detecting corked reds. OTOH, whites are always (for me anyway) opened when they are cold, which presents a different set of difficulties. These are worsened when the wine is one of the more aromatic varietals.

Agreed.

Vino

Leo Bueno wrote

Yes, I'd like to. One thing comes to mind: a good level of TCA perception starts when you are able to distinguish between corked wines who can be drank and corked wines to pour down the sink. The drinkable ones are those where the TCA hasn't already demaged the wine, killing most of it's aromas, and the undrinkable ones are those who just smell TCA and alcohol.

I don't believe such wines exist, unless your definition of drinkability is radically different from mine.

A bottle of corked wine should be taken back to where you bought it, if at all practical. If they won't take it back, find another place to buy your wine.

See earlier comment

I'll drink to that.

Vino

Vino wrote

I drank a bottle of Pignoletto some days ago, the nose was eprfect and the palate too, at first tasting. After a second sip I didn't notice anything and then smelled the cork: it smelled bad, so I tried the wine again, there was only a very far cork note in the mouth, while the aroma and taste of the wine were still presente. This wine was, I guess, in an initial stage of contamination, which left a very small trace of TCA and hadn't enough time to spoil the wine. The cork taste was very hard to feel, I had to concentrate on it and after this I could drink the wine wothout feeling cork. This is what I consider a corked wine which can be poured in glasses instead of sinks.

The wine in a corked bottle is never going to be as good as the same wine from a botle that is not corked. So you are not getting the wine that you paid for. That, to me, is reason enough to return the bottle (if that is practical).

Drinkability is a matter of personal taste. There have been times where I have gotten partway into a bottle before realizing it was corked. There is no way I could enjoy the remainder of the bottle. It's like getting an "off" taste from a piece of meat or fish. Maybe it's only one spot, but the rest of the piece won't taste the same after that.

vino

No need to go through the trouble.

Sigma Aldrich will sell a 1ml solution for about $45. I would prefer to pay less, but what the heck.

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