21 December 2006

Wet dog in a damp wool jersey

Huh?  Well, that's about the best way I can describe the smell of 'corked' wine.  On the palate, it's perhaps slightly more moldy cardboard, but either way, it's not what you want to discover in a bottle of Very Expensive Wine.
The reason I raise the issue, is that there is a certain Very Expensive Wine here from which I have had some very disturbing encounters with the aroma of wet dog recently.  I won't name the wine because when it's good, it's breathtakingly good.
But of 5 bottles I have opened, numbers 1 and 5 were excellent.  Numbers 2 and 3 where noticeably flat in the fruit and showing some signs of TCA (2,4,6-trichloroanisole) taint, and number 4 was a total disaster area.  That record is seriously unacceptable.
There's a lot of nonsense talked about corks, not to mention an enormous amount of irrational emotion and plain superstition.  So at the risk of upsetting those who believe tree-bark has mythical powers, I feel the need following my recent experience with nearly US$150-worth of ruined wine to address a few issues head-on.
Fact number one, the sole purpose of a cork is to keep your wine sealed from the outside world so that the polyphenols can go about their business of polymerising into longer chemical chains in peace and quiet.  The only thing a cork is likely to do to change your wine is to ruin it, either through failing to form a decent seal and letting the wine oxidise (cork failure), or through introducing TCA from the surface of the cork into the wine (cork taint).
The results of cork failure can range from totally flat fruit through to disappearance of good acids and creation of vinegary smells when bacteria come into contact with trace acetic acid in the wine.  You can usually tell a failed cork because there will be a thin wine stain in a line down the side all the way to the top when you remove the capsule or pull the cork out for inspection.  A cork that has done what it was meant to, on the other hand, will only have the stain on the surface that was facing the wine.
TCA is more insidious.  The cork may have sealed well (although it may also feel unusually dry and hard), but an imperfection was introduced to the wine the second the cork was inserted into the bottle.  TCA forms on and in cork through the action of naturally occurring fungal spores and polychlorophenols, which are chemical contaminants.  They get onto or into the cork either while the tree is growing, or (more commonly) through cork processing, unwise winery cleaning practices or even from treated wood used in construction of winery buildings or wooden pallets or crates.  TCA-affected wines range from flat and lifeless, with all the fruit character erased, through to musty and moldy as described above.  They can be very, very hard to spot unless you have a 'good' sample to compare alongside, and since many people don't have that luxury, often results in the consumer simply concluding that they are drinking bad (not spoilt) wine.
Fact number two, the idea that micro-oxygenation through a cork is a critical part of bottle-aging is a myth.  The only significant oxygenation that is likely to occur through a cork is through a failed cork, and ruins wine.  Those who believe in bottle micro-oxygenation are likely clinging to a popular myth revived as a theory to explain bottle aging in a way that would head off uptake of the screw-cap, which had just been invented in France, in the 1950s. The theory was thoroughly debunked by science in 1976 (and had in fact been debunked as early as 1898, after the idea was first suggested, which goes to show some myths are hard to kill).
While I accept that worshippers of cork mysticism are seldom impressed by science and logic, that science supports the notion that aging of wine primarily involves chemical redox reactions of acids and polyphenols (tannins and other flavonoids extracted from skin and seeds) from short-chain polyphenols into longer-chain polyphenolic compounds.  This process accounts for the reduction in harshness (which is a characteristic of shorter-chain tannins, particularly wood tannins) and also the development of more complex aromatic polyphenols which give 'bouquet' and complexity of flavours.  Oxygen obviously plays a chemically important role in these reactions - but to the extent that oxygen is present during this process, it is oxygen that has been picked up the wine before or during bottling at levels of 0.2 to 1 gram per litre (1 gram per litre, for example, has been associated with development of undesirably high levels of 'toasty' aromas).  This level varies greatly from bottle to bottle even on the same bottling run.  Cork 'leakage' has been shown to allow around 0.018 grams per litre - an insignificant variation on oxygen already in the wine at the time the cork is inserted - though corks also absorb air during the pressure of insertion and release it into the wine afterwards, boosting the overall oxygen content of the liquid.
It may be a useful side-note here to think about the role of oak in making wine to keep: oak tannins imparted to wine are hydrolysable, which means (among other things) they oxidise first - effectively soaking up the oxygen content of the wine over time and thus protecting the more complex 'condensed' long-chain fruit tannins.  The better your seal, the slower oxygen needs to be mopped up, and the longer your wine will keep before the fruit flavonoids are all dead and gone.
That is not to say that corks may not add something to the character of fine wine that has been bottle-aged for a long time, other than a little more oxygen primarily at cork insertion.  That effect is understood to occur through the solvent effects of alcohol and acids on the cork itself, which leach trace molecular compounds into the wine, leading to subtle differences in the chemical evolution of the acidic and polyphenolic compounds in the wine over time.  The extent of the difference is impossible to predict and varies from bottle to bottle of the same vintage, making it, like the oxygen boost of cork insertion, a unique wild card that no winemaker can design for and the quality or 'benefit' of which no consumer can anticipate.
So what does all this mean?  Simple: cork taint and/or failure rates like that described in the opening, or even at the the rate generally shown in studies of about 5%, are unacceptable.  Such failure is not in the industry's interests, because it drives consumers away from their product - especially those who do not recognise the failure and take the obvious remedial action, which is to demand a replacement bottle.  The myths about the wondrous benefits of cork are nothing but myths, and any affect on a wine's character over a very long time is minuscule, random, of debatable value, and certainly does not make up for the very real and quantifiable costs to consumer and industry alike of bad corks.
Sure, I enjoy the romance of pulling a cork out of a bottle as much as the next guy.  But I also enjoy tasting superb wine the way it's meant to taste.  So as far as I'm concerned, the sooner the Argentine industry and the consumers who currently seem to prefer to suffer bad wine embrace screw-cap technology, the better.


At 1:09 am, Blogger Tim of Greytown said...


Suffice to say, I couldn't agree more.

However, if you open another one and it is (obviously) corked, try the following trick before deciding to throw it away.

Pour the wine into an open mouthed decanter (or just a big glass) and ... wait for it .... swirl a plastic supermarket bag, wrapped around some rigid object like a spoon, around in the wine.

After a very short time, you may find that a considerable amount, if not all, of the cork taint has disappeared and the wine is once again drinkable.

This works. I've done it!

However, the discovery isn't mine.

A oenologist at Roseworthy apparently discovered that the TCA related compound that produces the taint also polymerises, on contact, with (something in?) the kind of plastic that's used in supermarket bags.

Give it a crack. Even if it doesn't completely cure the wine, if it makes a $US30 wine drinkable - if no t exquisite - you've saved some of the 30 bucks!

At 4:15 pm, Blogger Tim of Greytown said...

Or you could pay money....



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