I would like to find out what my TCA sensitivity tresshold is
(wouldn't you also, by the way)?

I have read that some folk are sensitive to concentrations as low as 1
ng/l (nanogram per liter), or possibly even lower, and that others
couldn't detect TCA unless they were swimming in a vat of the stuff.

Wondering where I can get some ready-made TCA solutions of different
concentrations in the range found in corked bottles.

Alternative, I guess we can start with, say, a 1000 ng/l solution and
dilute it by half, then by half again, etc. I am just concerned that
the serial dilution approach increases the error as one goes on, which
could be significant if doing it with bad equipment.

While we are at it, would the serial dilution be acceptable if done
using a 100 ml volumetric flask and a 200 ml volumetric flask?

I would take 100 ml of concentration X, put it in the 200 ml flask and
fill to volume, resulting in 0.5X. Then, take 100 ml of 0.5X, put it
in the 200 ml flask and fill it to volume, resulting in 0.25X, etc.,
etc.

First things first, where can I get a solution of known concentration
of TCA (in water and suitable for human sipping and spitting)?

Thanks.


--
================================
Check out the MiamiWine blog.
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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.


On Fri, 10 Nov 2006 15:47:54 GMT, Leo Bueno
> wrote:

>
>I would like to find out what my TCA sensitivity tresshold is
>(wouldn't you also, by the way)?
>
>I have read that some folk are sensitive to concentrations as low as 1
>ng/l (nanogram per liter), or possibly even lower, and that others
>couldn't detect TCA unless they were swimming in a vat of the stuff.
>
>Wondering where I can get some ready-made TCA solutions of different
>concentrations in the range found in corked bottles.
>
>Alternative, I guess we can start with, say, a 1000 ng/l solution and
>dilute it by half, then by half again, etc. I am just concerned that
>the serial dilution approach increases the error as one goes on, which
>could be significant if doing it with bad equipment.
>
>While we are at it, would the serial dilution be acceptable if done
>using a 100 ml volumetric flask and a 200 ml volumetric flask?
>
>I would take 100 ml of concentration X, put it in the 200 ml flask and
>fill to volume, resulting in 0.5X. Then, take 100 ml of 0.5X, put it
>in the 200 ml flask and fill it to volume, resulting in 0.25X, etc.,
>etc.
>
>First things first, where can I get a solution of known concentration
>of TCA (in water and suitable for human sipping and spitting)?
>
>Thanks.

--
================================
Check out the MiamiWine blog.
http://MiamiWine.com
================================

Leo Bueno wrote:
> I would like to find out what my TCA sensitivity tresshold is
> (wouldn't you also, by the way)?

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?).


> Wondering where I can get some ready-made TCA solutions of different
> concentrations in the range found in corked bottles.

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).

>
> Alternative, I guess we can start with, say, a 1000 ng/l solution and
> dilute it by half, then by half again, etc. I am just concerned that
> the serial dilution approach increases the error as one goes on, which
> could be significant if doing it with bad equipment.
>
> While we are at it, would the serial dilution be acceptable if done
> using a 100 ml volumetric flask and a 200 ml volumetric flask?

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.

>
> I would take 100 ml of concentration X, put it in the 200 ml flask and
> fill to volume, resulting in 0.5X. Then, take 100 ml of 0.5X, put it
> in the 200 ml flask and fill it to volume, resulting in 0.25X, etc.,
> etc.

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.

>
> First things first, where can I get a solution of known concentration
> of TCA (in water and suitable for human sipping and spitting)?

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

In article >,
says...
>
>
>I would like to find out what my TCA sensitivity tresshold is
>(wouldn't you also, by the way)?
>
>I have read that some folk are sensitive to concentrations as low as 1
>ng/l (nanogram per liter), or possibly even lower, and that others
>couldn't detect TCA unless they were swimming in a vat of the stuff.
>
>Wondering where I can get some ready-made TCA solutions of different
>concentrations in the range found in corked bottles.
>
>Alternative, I guess we can start with, say, a 1000 ng/l solution and
>dilute it by half, then by half again, etc. I am just concerned that
>the serial dilution approach increases the error as one goes on, which
>could be significant if doing it with bad equipment.
>
>While we are at it, would the serial dilution be acceptable if done
>using a 100 ml volumetric flask and a 200 ml volumetric flask?
>
>I would take 100 ml of concentration X, put it in the 200 ml flask and
>fill to volume, resulting in 0.5X. Then, take 100 ml of 0.5X, put it
>in the 200 ml flask and fill it to volume, resulting in 0.25X, etc.,
>etc.
>
>First things first, where can I get a solution of known concentration
>of TCA (in water and suitable for human sipping and spitting)?
>
>Thanks.

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

On 11 Nov 2006 04:34:54 GMT, (Hunt) wrote:

>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.
>
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.

>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.
>
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.

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

Agreed.

Vino

Leo Bueno wrote

> I would like to find out what my TCA sensitivity tresshold is
> (wouldn't you also, by the way)?

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.
--
Vilco
Think pink, drink rose'

On Sat, 11 Nov 2006 15:04:02 +0100, "Vilco" >
wrote:

>Leo Bueno wrote
>
>> I would like to find out what my TCA sensitivity tresshold is
>> (wouldn't you also, by the way)?
>
>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

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


>and corked wines to pour down the sink.

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.

>The
>drinkable ones are those where the TCA hasn't already demaged the
>wine, killing most of it's aromas,

See earlier comment

>and the undrinkable ones are those
>who just smell TCA and alcohol.

I'll drink to that.

Vino

Vino 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

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

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.
--
Vilco
Think pink, drink rose'

On Sun, 12 Nov 2006 22:36:07 +0100, "Vilco" >
wrote:

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

On Fri, 10 Nov 2006 11:12:11 -0500, Mark Lipton >
wrote:

>
>> Wondering where I can get some ready-made TCA solutions of different
>> concentrations in the range found in corked bottles.
>
>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).
>

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.

--
================================
Check out the MiamiWine blog.
http://MiamiWine.com
================================