Less than 1% of wines corked?

Haven’t seen my new issue of Vineyard & Winery Management yet, but apparently there is an article in it written by Christian Butzke on the incidence of cork taint in the Indy Wine Competition. WS article here (subscriber limited, sorry):

Study Claims Less Than 1 Percent of Corks Are Noticeably Tainted | Wine Spectator" onclick="window.open(this.href);return false;

Doesn’t sound like a particularly scientific study, and no analysis - merely reporting by judges.

I’ll keep my thoughts to myself since, well, what’s the f-ing point? Everyone disagrees on the number anyway, with those who use cork trying to minimize it and those who don’t grinding their own axe (unfortunately, we all need to either use cork or don’t, and justify that accordingly).

Interesting to me was this tidbit:

Yet research into the science of cork taint indicates that the two results may not be mutually exclusive. The explanation for that paradox revolves around TCA itself. According to Ron Jackson, author of Wine Science: Principles and Application, a person’s ability to detect the presence of TCA varies so widely that the percentage of bottles identified as corked could swing wildly depending on who was doing the tasting.

“For 99 percent of people to detect TCA, you’re talking a concentration in the range of 200 to 300 parts per million,” said Jackson. “For 50 percent or more of people to detect it two-thirds of the time, the value is in the range of 5 to 7 parts per billion. But some people can detect concentrations as low as single parts per trillion.” Unfortunately, even when TCA levels are too low to detect, they can ruin a wine—at low concentrations the chemical deadens a wine’s fruity flavors and aromas.

So, threshold varies from 2 ng/L to 300,000,000 ng/L? Are we including anosmics?

I have been running about five percent in the past few months.

My personal experience has been around 1-2% … then again, there’s probably a handful of other “kinda corked” wines that I don’t identify as “kinda corked,” but rather just “not that great of a wine” because that’s the only bottle I’ve ever had of that wine (no baseline to compare against).

For the periods I’ve kept tallies, I’ve had between 2% and 8% of cork sealed wines turn up with closure-related faults (TCA, oxidation, mould, cork flavour). I’ll still buy some wines under cork (Italians, Spaniards, bubbles mainly) where I don’t have a choice of closure, but wish it were a better seal.

I unfortunately seem to be very sensitive and have been running about 8 %. I do feel that it is coming down some. I seldom go through a week without finding some corked wines. I have been impressed with this Diam cork that some people are using. They say maybe 1 bottle in a million. My count is now up to 201 bottles with that closure and no hints of TCA. I still love those Stelvins for lots of wines.

I started tracking this only about 13 months ago and I am running at approx. 4%. The corked wines are coming from several sources but mostly direct from the wineries.

This is just BS. The human threshold is several parts per trillion. The idea that is takes 200-300 parts per million for 99% of people is just ludicrous. Not only that, the second sentence totally contradicts the first. If 99% require 2-300 PPM to detect, how can half of the people detect it 2/3 of the time at 5-7 PPT???

I am cursed with being very sensitive, my guess is in the 4-5 PPT range, and know one or two people that are probably more 2-3 PPT. For me, approximately 5-8% of wines are corked. Interestingly enough, in the past week, a 2000 Ramonet Montrachet, a half btl of 98 Beaucastel and a bottle of Scotch sealed with a T-top were all corked.

Hogwash . . . the darned article is hogwash, I tell you!!!

Seriously, as Nate points out, it is FAR from a scientific study . . .

We just did cork trials at Fess Parker with a very well respected cork producer, and our best lot had about 4% TCA and about 6% ‘other off aromas’ . . . .

The worst lot - and understand that the cork co. KNOWS we are testing for TCA and it would therefore behoove them to get the best darned lot to us . . . if they COULD - had over 15% TCA and another 10-15% ‘other off aromas’ . . .

Are things ‘getting better’?!?!? Maybe, but from a winemaker’s perspective, it REALLY SUCKS to put 2 years of work into a wine only to see it ‘ruined’ quite quickly by a 2" piece of cork . . .

Just another data point . . .

Cheers!

So you guys soaked and tested individual corks for TCA? How many? Or are you self-reporting on sniff tests as well?

Had a mildly corked bottle last night. Considering the number of wines in the past month both here and in Napa, I am running at 0.2% or so for August.

At my 76 seat restaurant/wine bar, 75%+ of the wine we sell is BTG.

Our corked rate is about 1.5% of those with corks. Our bottles with corks are down to less than 75% now, with screw caps, vino locks, etc. constantly increasing.

IMHO, many of the wines identified as corked are actually heat damaged. Yes, the wines are flawed, but not by the cork.

Since I’m very anal about storage/shipping conditions, we only purchase from the minute portion of importers/distributors who guarantee tempurature control throughout the shipping process.

This is why I believe our failure rate for returned bottles is less.

Cheers![/quote]
So you guys soaked and tested individual corks for TCA? How many? Or are you self-reporting on sniff tests as well?[/quote]

Nate-

We got 250 count sample bags; we randomly selected 100 corks from each 250 bag sample; we put these into jars with tin-lined caps and soaked each for approx. 36 hours; we then poured them into glasses and 4 of us walked around and smelled each glass; If at least 3 of us felt the sample showed signs of TCA, it was noted as having TCA . . .

We did NOT send any samples off to ETS or Vinquiry for further study, trusting our noses to determine what we wanted to do . . .

Curious to hear your feedback on our protocol and our findings . . .

Cheers!

Just curious.

You made it sound as though your problem was in the sniffing and self-reporting by wine judges who tasted 3,500 individual bottles and designated <1% of them as corked. How many were false positives? How many corked bottles slipped through the cracks? We’ll never know I guess. No analysis.

I don’t have all the answers, so no comment on your protocol. Each winemaker needs to do things in a way that makes them feel comfortable and confident in what they’re purchasing. One thing I always wonder when sniffing or looking at SPME of multi-cork soaks is what the breakdown is. One cork at sky-high levels? Baseline low level? In between?

One problem is the lack of feedback through the system. For this reason, I like to talk to high-volume tasting rooms who train and test their staff for sensitivity and have their supplier brand their corks and then track bottles opened by supplier and rejected bottles by supplier.

For another data point, I talked to one such winemaker recently who does this at his high-volume TR. His best supplier was 0.5%. His worst was 1.5%.

Tom, no doubt that your purchasing thru importers/distributors that temp control will result in fewer cooked bottles and therefore a lower return rate. But I take exception to your opinion that ‘many of the wines identified as corked are actually heat damaged’. I can easily distinguish between corked and cooked, and I still will tell you that 5-8% of the wines I try are corked. Then add the cooked and premoxed btls, and the bad bottles can easily exceed 10%. And I think most people are not confused between the two.

Chuck - thanks for the feedback.

For clarity purposes, I define “corked” as the moldy, musty smell that we all know. I’m not including bottle variation in my stats of 1.5% rate. Perhaps I should?

Interesting dialogue here- I had a question for those in tasting rooms, restaurants and private consumers citing their experience with rates of TCA-tainted wines: Is there any notable variation of TCA taint based on the age of the wine being tasted in the sampling? For most peoples’ posts, I do not see any mention of what is being tasted and how old the wines are that are part of the sample for which they are reporting their estimated percentages of tainted wines from cork. Some of the numbers being reported are very much in line with what I used to see a decade ago, when very clearly the cork industry had done little to address the situation of TCA taint and numbers were generally reported in the 5-8% range by many commentators.

But it is very clear to me from reviewing the literature and recently visiting Portugal that giant strides have been made in the last decade and the incidence of TCA taint is dropping dramatically today and is likely to get below the 1% threshold on a consistent basis in the coming years. Now this number includes all types of corks, and ironically, some of the lower level corks are better than the top of the line for avoiding TCA contamination, and if I were a winemaker I would be looking at aglo-corks for my own closures, rather than the top of the line, single punch long corks, as the manufacturing process for the aglos allows for much more certain TCA control than the single piece long corks. If you are a winemaker and running high numbers of TCA contamination during your pre-bottling runs, the question has to be asked what kind of corks are you using and why have you selected this type?

Most wineries that select the top of the line, single punch corks (which ironically run a higher percentage these days of TCA contamination than aglos) due so for aesthetic reasons, as the long, clean and well-grained cork adds a certain luster to the experience of pulling the cork for consumers and sends the message that the winery is committed to excellence in every aspect of the wine producing process. Of course a long, single punch cork also is impossible to inspect or treat for potential TCA contamination on the interior of the cork, so by definition it is a crap shoot what is going on below the surface of a single punch cork. With aglos, the ground up pieces of cork are treated and analyzed prior to being pressed into shape and glued, so the incidence of TCA in these corks is negligible, though the stigma of using a “pressed cork” with consumers cannot be discounted at the present time. I saw a very interesting cork design selected by one winery which was a “twin top” (an aglo cork wtih two slices of solid cork at each end) that had a lovely print design in the middle area of the cork that effectively hid the pressed cork section under the pattern and gave the appearence of being a single punch cork. A brilliant idea and their corks are likely to be virtually TCA free!

As a wine writer I open a lot of bottles, and my incidence for TCA tainted wines is way down over the last several years for young vintages that I am sampling. I do not bother anymore to keep a log, but it has dropped dramatically from a decade ago, when 5% would have been a good number. I still see about 5% with older bottles that I open, and as I write a lot about mature wines, I still share the agony of a corked bottle of potentially great wine ruined by TCA. My own personal threshold for TCA taint is on the higher side, so I am not as sensitive to it as others, which was helpful a few weeks ago when a bottle of 1921 Chateau Montrose was declared mildly corked by two fellow tasters, but the rest of us at the table could not detect any TCA and happily drank the bottle!

The cork industry certainly deserved its vilification for its slipshod methods at quality control in the past, when little if anything was done to address the issues of TCA taint. However, a sluggish and disinterested past must be separated from the very real, aggressive and impressively successful steps that have been taken in the last decade in terms of research and quality control to address the TCA issue and to the best of their ability reduce TCA taint in corks down to a statistically much less significant number- they are not where they want to be yet, but from what I have seen and read, they are moving briskly in the right direction and have made profound progress in the last decade or so. Today I am much more concerned with the issue of wines ruined by permanent reduction under screwcaps than I am with TCA, as my incidence with wines ruined in this manner runs dramatically higher than TCA-tainted young wines, and I am sampling wines under screwcap in their infancy, when most issues of reduction are only in the most formative stages. From the data I have seen on reduction and screwcaps, my numbers would be really ugly if I was sampling SC wines at ages four or five, instead of wines removed from bottling by only 6-12 months.

Just a little food for thought.

John

Posted by John Gilman:

Today I am much more concerned with the issue of wines ruined by permanent reduction under screwcaps than I am with TCA, as my incidence with wines ruined in this manner runs dramatically higher than TCA-tainted young wines, and I am sampling wines under screwcap in their infancy, when most issues of reduction are only in the most formative stages.

John, Thank you for these insights. As you probably know, Paul White has expressed related concerns about screw capped- wine (http://www.winewriting.com/Screwcaps.htm" onclick="window.open(this.href);return false;). He also disclosed that some attempt to counter reductive wines by adding excess copper salts. For we amateurs, have you encountered any (many?) wines that tasted like they had had such a treatment? Just curious.

I open about an equal mix of young and old wines, and I find that for older wines, I run at about 5% (not counting wines where there’s a systemic problem, like the entire case of Mondavi '76 that went down the drain). For younger wines, say 2004 and newer, I honestly can’t remember the last time I found one that was corked. I don’t know if that’s because of better production methods, or that I’m less sensitive than some and it takes the TCA blooming in the bottle for a long time to reach my threshold of sensitivity.

John,

Interesting info. I guess my question re: screw caps and reduction - is this something you see immediately after opening and continuing in the wine after it’s been open awhile or just at opening? C urious to hear ;. . .

Cheers!

Hi Mitch,

I have read quite a bit of what Paul White has written on the issue and he was very instrumental in pointing me in the direction of the research that has been done by the Australian Wine Research Institute and others on issues of reduction and oxidation. I conducted an interview with Dr. White in one of the recent issues of my newsletter, which made for some pretty fascinating reading, and I would be happy to share it with anyone who might be interested in his research (just email me at jbgilman@ix.netcom.com). He has taken a lot of heat in some circles for his willingness to tackle this issue by questioning research and cross checking it with other scientists and the accepted literature in the field of chemistry, and from what I have seen, he has been spot on with all of his critiques.

So I am very aware of the standard operating procedure of adding copper sulphate to wines pre-bottling that has been in affect for several years now in Australia and New Zealand for wines that are destined to be bottled under screwcap. I am uncertain of how these now routine additions of copper sulphate to a wine affect their safety for human consumption (as residual copper is left behind in the wine), as there are no longer any regulations in Australia and New Zealand with respect to setting maximum levels of residual copper, given that the Australian Food Standards Code was changed a few years back abolishing any such maximum level for wine. Previously, the regulations in Australia and New Zealand (both countries operate under the same set of rules for wine) had prohibited residual copper concentrations in excess of 5.0 mg. per liter, which was the same as the maximum level currently allowed in the United States. But within the last few years the governments Down Under have scrapped this maximum level of residual copper in wine- “why” being a very good question to which I have not seen any answer.

The questionable aspect here to my mind is that residual copper cannot be tasted or noticed in a wine unless the level is sufficiently high enough to form a haze by the residual copper’s reaction with proteins that might still be in the wine after filtering. Without the “copper haze” formation, there is no way to tell how much residual copper one is consuming when drinking a wine from Australia or New Zealand that has been copper fined, as testing is no longer done for these wines with the abolition of the maximum level for safe human consumption by the good folks responsible for the Australian Food Standards Code. And thanks to GATT, wines produced in one country under regulations that make them safe for their domestic markets are not subject to regulations in the countries that import them, so our FDA maximum limits of 5 mg. per liter of residual copper are not applicable in regards to copper-fined wines from Australasia and are of no use in protecting consumers, just in case there happens to be wines on the market here that are above what is currently deemed safe for human consumption.

In affect, the changes of the Australian Food Standards Code for maximum levels of copper in wine effectively usurped the FDA’s ability to police the US market for wines with potentially hazardous levles of residual copper from Australia and New Zealand, assuming of course that the FDA had any interest in doing so. I had contacted a very nice gentleman at the FDA to ask him about this issue, and he was going to look into it and get right back to me. That was six months ago and I have still not heard from him. But to give one some idea of how potentially wide spread the issue is in Australasia today, the Australian Wine Institute published a paper in April of 2008 written by oenologist Geoff Cowey about the issue, entitled “Excessive copper fining of wines sealed under screwcaps- identifying and treating reductive winemaking characters,” which was published in The Australian & New Zealand Grapegrower and Winemaker. It makes for some pretty interesting reading, to say the least. I highly recommend reading the paper before opening up the next bottle of Australian or New Zealand wine sealed under screwcap.

The bottom line is that today one does not have to be wary of only of residual copper above safe levels for human consupmption, as in addition, one of the methods now often used to try and remove excess copper prior to bottling is what is called a “Blue Fining”, where the wine is fined with potassium ferrocyanide. To quote Mr. Cowey: "However, in most cases (of greater than desired concentrations of copper in the wine), fining with potassium ferrocyanide (PFC), an operation referred to as “blue fining”, is required to decrease the concentraton of copper to below the recommended “safe level”. (I should note that Mr. Cowey’s recommended “safe level” is the 5 mg. per liter that was formally the limit of the Australian Food Standards Code.) The goal of the paper is to give winemakers a firm blueprint for treating wines for potential reduction prior to bottling, so as to minimize the likelihood of excess copper in the wines and the need for blue fining, as Mr. Cowey continues, “over-fining and the retention of excess ferrocyanide in the wine” is not desirable, for “excess ferrocyanide, might, in time, liberate cyanide, thus rendering the wine unsaleable and possibly toxic.” Yum.

The bizarre thing is that all of this is done to allow wines sealed under screwcaps to prolong the period of fine drinking before they become liable to permanent reduction- all of the literature that I have read indicates that all of this addition of copper sulphate prior to bottling only pushes further out the onset of reduction in a wine sealed under an anaerobic seal such as screwcaps currently provide- it most emphatically does not prevent it. So the addition of all this heavy metal is to simply give a wider window for the wine to be consumed prior to the onset of reduction- if the wine is sealed under a screwcap. If the wine is sealed under a cork, then none of this- copper sulphate additions, fining with ferrocyanide- are necessary. Additionally, copper fining does not only target the sulfur molecules that are prone to reduction and the formation of thiols in an anaerobic environment, it targets all sulfur compounds in the wine- many of which are resonsible for the aromatic and flavor complexity that makes wine such a compelling beverage in the first place. The literature that I have seen on this issue is very persuasive. So in the end we add all this copper (or strip it out at the risk of adding cyanide), so that we can make the wine less complex from the start, and only push back the day of reckoning with permanent reduction, all so that we can use a specific type of closure! The whole thing is asinine in my opinion.

I should note that the screwcap industry is feverishly working to create better seals that allow a certain degree of oxygen ingress (trying to emulate natural cork’s performance in this respect), so that in the future all of this copper fining may no longer be necessary. I would be very curious to hear what winemakers here in the US or Europe are doing to address the potential impact of permanent reduction in wines sealed under screwcaps, as of course they are subject to the limitations on residual copper in wines as set out by the appropriate regulatory agencies in their home countries. But in the interim, I am a bit hesitant to not spit out that screwcapped wine from Australasia from the current vintage that I might be sampling, and needless to say, there are none of those potentially heavy metal wines in my cellar. I would love to see some research done on the safe levels of residual copper in wine for those of us that taste and spit the wines :slight_smile:

Best,

John