Each year, we conduct cork trials at Fess Parker to try to determine the specific lot of corks to use for our higher end wines for the next twelve months. Here is the protocol we use:
We work with 3 or 4 suppliers whom we’ve done business with in the past, or have been highly recommended by other winemaker friends.
We do a ‘visual’ assessment first, asking each producer to send us approximately 100 corks from a few select lots based on the price parameters we set.
After cherry picking those lots we feel ‘look best’, we then ask for 250 cork bags to be sent to us, with at least three different sub-lots from each of the lots requested.
We then randomly pick 100 corks out of each 250 cork bag and place them in 100 ml glass jars, fill each jar to the top *and make sure each cork is submerged) with a ‘generic’ chardonnay that is not overly aromatic, put the tin-lined lid on each jar, and place these in a dark room. We fill two extra jars with the same wine as ‘standards’.
After 48 hours, we empty the content of each of these jars sans the cork into clean wine glasses and go around the room, assessing each glass to see if any detectable TCA exists. In addtion, we note ‘muted’ glasses, glasses that have ‘medicinal’ or ‘smoky’ or any other characteristic that is radically different than the standards.
I know that many on this board continue to talk about the apparent irradication of TCA from the cork industry, but if our latest results are indicative of where it stands, I would have to say that this is simply not the case. We are not going out of our way looking for TCA, and you have to believe that IF cork producers COULD easily tell if their corks had TCA or not, it would behoove them NOT to include them with the corks sent KNOWING that we are conducting trials, right?
4 or 5 of us walk around the table each time, and note if their are any signs to note. We then corroborate and ensure that a majority feels the same about each ‘incident’ cork.
We still have a few rounds to go, but I can tell you that the best cork lot had about a 3% TCA rate - quite quite good. We had another that had a 4% one and another that had about a 5% one. But then we had one that had about a 12% TCA rate, and the worst yet was well over 20%.
Thanks for the insights.
Do you pay for the samples or is your anticipated purchase large enough that they would offer up such samples gratis? If you had to pay, I wonder what the impact would be for a smaller wine maker to go through a similar test.
What’s the reaction of the purveyor who hits the 20% fail rate? Is it “TCA happens” or “you must be mistaken?”
Pretty scary results. I hope you’ll publish which producers had the 12% and 20% TCA rates. Data like that might force changes. I know the Jean Marie Fourrier believes that there are similar variations in performance among cork producers from an oxidation perspective.
Since the US Cork Quality Council [which includes the major cork producers] has claimed through ETS or Scott Labs using GC-MS testing that they had got their average TCA levels in the cork bales they use below 1ppt by 2008 [from 4 in 2001] it would interesting to know whether your suppliers come from within that body and if so what response they make or have made to these latest tests.
Of course your general results are interesting but without putting names to the suppliers it is difficult to know whether they can be extrapolated to the general population of cork-closed wines. It is also interesting that they seem to contradict the general direction of reporting in all the major forums - including the major critics.
You imply that your results are achieved by the nose [and taste?] alone and I wonder whether you do any GC-MS checks on any of your results with e.g. ETS or Scott Labs? You will know from previous ‘cork’ threads that such tests have revealed a significant number with no TCA even when called by expert panels in tests such as yours.
But I guess you are saying that customers should expect at least a 3% TCA rate on your high end wines - unless of course your final lots reveal a much better supplier.
We do not pay for any of these corks - they are donated by the producers in order to try to get our business . . . a small price to pay in all honesty.
These are not the ‘highest grade’ corks where you are likely to pay over $1 or more per cork. These are above average corks in the $.60-.80 range. Hope that helps.
We do not send the corks out for further testing. All trials are done by nose alone - I have a feeling if we did it by taste, we might find a couple more out there in each batch. Those going around and smelling are either trained winemakers or production folks who are trained in TCA detection. Everyone’s detection levels are different, so one may pick something up where others will not . . .
One thing to consider is that we are dealing with only one variable here - the corks themselves. The standard wine is just that - the same wine in a glass. When you deal with finished wines that have been in bottle for a long time, along with the cork, you certainly can get oxidative, aged, or other characteristics that may make it more difficult to accurately detect TCA. We are also not dealing with ‘bottle variation’ due to the potential of ‘unfiltered wines’ that may lead to bacterial growth and thus emit other aromas.
I understand what the Cork Council is stating, but I have to trust the numbers we are getting . . . .
Larry,
Thanks for the feedback which I understand. Using a ‘standard’ low aroma white wine is the best medium for TCA detection in wine since similar tests/studies have indicated a threshold difference of around 2:1 between white and red wine i.e. people were on average sensing TCA in white wine at roughly half the ppt versus red.
So my comment about 3% TCA in your high[er] level wines could be factored downwards substantially if these were [primarily] red wines which I am guessing they are.
Of course your consumers will also be drinking wines that have been in the bottle for some time and will be exhibiting much more complex aromas and tastes than low aroma Chardonnay and given the huge individual range in TCA thresholds and [importantly] experience, the percentage actually noticed will diminish still further. Another factor is that the whole cork immersion makes more TCA available to the wine than a cork inserted into a bottle which might also reduce the strike rate even further.
However you do seem to be saying that at least 3% of your higher level wines are still likely to be closed by TCA affected corks if that’s the best result you get from your cork suppliers.
It would of course be interesting to know what the actual level of TCA is in those individual samples that have been called as TCA although I accept it would be expensive to have them all GC-MS tested. I just wondered whether you might have tested a random sample to see what the actual ppt levels were.
You didn’t say whether any or all of cork suppliers were members of the US Cork Quality Council and, if they are, what response you get/have got from them in the light of these results, particularly the very high levels. I understand you may be reluctant to name your suppliers but is it possible for you to say whether they are members of the USCQC.
My final point concerns your comment that your studies contradict the apparently wide perception that most wine drinkers who know TCA are experiencing less of it. On the face of it your comment is perfectly logical but the reality would depend on in part on just how sensitive your panel is to TCA. I realise that they are trained but that cannot transcend the pure sensing ability.
If one or two of your panel are extremely sensitive, say to 1ppt and even below, it would be possible for them to keep picking TCA in low aroma white wine even though the levels generally had fallen from say an average of 4 to below 1ppt.
Meanwhile the considerable majority of experienced wine drinkers with a range of thresholds higher than the lowest in your panel would have gradually ceased to detect TCA as often as it increasingly fell below their individual thresholds and those of most of the people they drink wine with.
So I suggest that you and your panel’s experience may not be as contradictory as you have indicated even on the evidence.
Hi Nigel, do you know if TCA concentration is uniform thru a given cork, or if the TCA is scattered thruout the cork, like a salt shaker with a few specs of pepper mixed in?
If the former, Larry’s testing methodology would seem to be appropriate and the results meaningful. If the latter, the methodology would seem to greatly exaggerate the potential for corked wines. The odds of getting a spec of TCA pepper on the small perecentage of cork surface exposed to the wine would be much lower than that of the entire cork surface.
Peter,
While I am not aware of quantitative studies seeking to determine whether there is any sort of typical TCA distribution in affected corks there is plenty of evidence from various reports and studies that TCA is not uniformly present in infected corks. Its location would also depend on the source/location of the infection which also varies e.g. whether the TCA is created directly on/in the cork or comes from external sources.
You will be aware that there are even occasional reports of corks that have been tainted without the wine in the bottle being infected.
A study by the Australian Wine Research Institute [AWRI] using radio-actively tagged TCA showed that TCA placed on the top of a cork-closed bottle did not penetrate to the wine over the 36 month period studied - and that subsequent analysis of the corks indicated that it probably wouldn’t over longer periods.
In any case I think that Larry’s methodology seems to be an entirely reasonable approach to seeking to determine whether corks have any TCA infection and I only qualify it because I cannot precisely translate the methodology as described [specifically the original choice method and the subsequent numbers] and am also aware of trained panels calling TCA on some samples wine that were shown to be free from it by Gas Chromatography-Mass Spectrometry testing.
However my main point was to suggest that the actual level of TCA as opposed to its presence was a not an insignificant issue [along with its ‘availability’ in/on a cork when placed in the neck of a bottle as opposed to being entirely soaked in wine] in understanding in how it might be sensed by people with widely different thresholds.
And therefore, if TCA was being steadily reduced over time by cork producers, how fewer and fewer wine drinkers, even those who have experienced and recognise TCA, might sense it while very sensitive and experienced tasters e.g. Larry’s tasting panel might continue to do so - at least to some extent.
I’m assuming that all of the corks you are testing are bleached? If so, do you know what bleaching medium is being used by the cork producer? (Most use peroxide these days, but some use ozone. Both are of course highly oxidative if any residual remains in the finished corks.)
Have you ever included any unbleached corks in your trials? It would be very interesting to know the incidence of corked aromas in lots of bleached vs. unbleached corks.
I don’t have any quantitative data, but my experience is that the chances of a corked wine seem to increase with the age of the wine. So I wonder if this is because the wine comes into contact with more of the cork over time, as it slowly penetrates the cork and seeps around the edges, thus increasing the possibility of the wine hitting a pocket of TCA?
Larry thanks for the post. We don’t do any extensive testing like that but I do keep track of corked bottles we open in the tasting room and I have seen about .5% I have heard of numbers from some wineries around 4% which is scary. 20%, if it happened would be devastating.
Peter,
Studies have indicated that ‘available’ TCA transfers from cork to wine [and more obviously vice versa] pretty quickly so age is not generally a significant factor in the appearance of TCA in an otherwise soundly cork-closed wine although what you describe might explain a delayed contamination.
More usually the greater incidence of TCA in old[er] wines is due to the fact that TCA has only been substantially reduced and removed in the cork production process relatively recently [from storage of the raw bark through to finishing] through quality management systems, special treatment processes and state-of-the art testing. The US Cork Quality Council’s figures indicate an 80% reduction [2001 to 2008 and beyond] to below 1ppt over the last decade.
As a result wines from e.g. the 80s and 90s and early noughties will generally have a higher incidence and level of TCA than modern vintages with only the most recent showing the very large improvement so there will often be a perception of cork contamination being related to age. The seepage issue you refer to might explain some apparently age-related cases but IMO by far the larger part is explained by the improvement in cork quality.
The corks we use for the trials are not bleached (actual bleach, that is) - some have been peroxide washed but none have been bleached. I did have one non-peroxide washed sample as well - it did not fare well . . .
To tell you the truth, I’m not sure how many others in our area due this type of in-hosue testing. I know that some producers up North use third parties such as ETS or Vinquiry to do their testings, and some very large wineries have in-house testing done similar to ours.
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