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The Romans sometimes stored wine in bottles, using a layer of olive oil floated on top to protect it from the air. However, until the 17th century, the near universal way of storing and transporting wine was in barrels (or amphorae). Once a barrel was opened (tapped), it would need to be drunk fairly swiftly, as there was then no way of protecting it from the air. It's a subject which Maria Celeste mentions fairly often in her correspondence with her father Galileo, e.g. on 13th July 1633 she wrote "Already the cask that you had tapped before you left, Sire, from which the housemaid and the servant drink, has begun to spoil." Bottles did exist, but were used as a way of serving wine, rather than for storing it.

It was in the early seventeenth century (and therefore theoretically available to Galileo) that bottles sealed with cork were invented, at the same time as improvements in glass manufacture made the bottling of wine economically viable (and also at the same time as the invention of the cork-screw). This development allowed the creation of vins de garde, i.e. wines intended to undergo years of bottle aging before being consumed. Not long after, we have the first wines identified by the specific vineyard where they were made (rather than simply by generic names, as claret, burgundy, hock, etc): in particular, Château Haut Brion, listed as being in the cellar of Charles II and praised by Samuel Pepys, and still today one of the most prestigious wines in the world.

Between then and the end of the twentieth century, the technology did not change much (although the shape of the bottles did). It was in the 1990s, when I was first becoming interested in wine, that someone developed a synthetic cork, the purpose of which (as I understood it at the time) was to replicate the function of a natural cork, but without the risk of cork taint.

Cork taint is caused by a number of different chemicals, of which the most common is 2,4,6-trichloroanisole (TCA). TCA has a highly distinctive smell, variously described as being like a mouldy cellar or wet dog, and is detectable at very small concentrations - a few parts per trillion. However, the sensitivity of different tasters to TCA varies by several orders of magnitude.

If a bottle is clearly corked, then it's easy enough to return it, although it can be a bit of pain if it was a special bottle you wanted to drink on a specific occasion, and it can also be difficult to return bottles from online stockists. The greater problem, from the point of view both of producers and consumers, is when the level of TCA is below the detectable threshold, when it depresses the wine's natural aromas and flavours, which is only recognisable if you know how the wine is supposed to taste. If you buy a case of wine, and one bottle is corked, it's very obvious, but if you are trying a new wine, it's hard to be sure if the flavours are being suppressed by cork taint, or if the wine is simply bland.

Estimates of the incidence of cork taint vary widely. Malcolm Gluck, who was a passionate advocate of synthetic cork, estimated it at 10%, but I've never seen another estimate that high. The cork industry, unsurprisingly, cite studies suggesting that it might be as low as 1%, while a Wine Spectator blind tasting suggested an incidence of around 7%. From my own experience, I would estimate it at 5% - it's certainly not unusual for one bottle in a case of twelve to be corked. The situation is complicated by the facts that: (a) consumers probably sometimes think that a wine is corked when it in fact has some other fault, (b) although TCA is the most common cause of cork taint, it isn't the only cause, and other forms of cork taint have quite different smells, (c) the presence of TCA in wine is not always due to the cork, which explains why 'corked' wine is sometimes found in bottles without natural corks.

The cork industry have recently been making an effort to reduce the incidence of cork taint, by using alternative bleaching agents and so forth. It may be, in consequence, that the incidence of cork taint is now lower than it was in the past. Of the hundred odd bottles I've tasted so far in the wine tasting project, I identified only one as being corked. (I also identified two as being oxidised and one as having Brett (which is a rogue yeast).) Around 30 had natural corks, so one duff one is consistent with a 5% incidence, but also consistent with something slightly lower.

Getting back to the synthetic cork, the point was that it would replicate the aging potential allowed by the natural cork, while giving the consumer confidence that they were drinking the wine as the vintner intended. But of course the last point was highly doubtful, both because TCA can be introduced to the wine from some other source and because of the prevalance of other faults.

Boschendal Chardonnay is an interesting case in point. Until recently, they were using a synthetic cork. Nevertheless, we still got a duff bottle in May, which tasted very flat. Another reviewer on Ocado also reports having received duff bottles at about the same time, so it seems likely that there was a problem with a whole batch, perhaps from a contaminated vat. In the latest (2010) vintage, they've reverted to natural cork. I'm not sure whether there's any connection between these facts, but it does seem to be part of a wider trend against synthetic corks.

Mostly though, synthetic corks have been replaced by screw-caps. Even a decade ago, these were considered fit for only the most appalling plonk. New Zealand was the first place to buck the trend, and pretty nearly everything from there, even the grandest wines (but not sparkling wines), now has a screw-cap. Australia is going the same way, and even Rieslings which state that they will benefit from a very long cellaring period have screw-caps. Similarly, the South African Rustenberg John X Merriman 2009 has a screw-cap, not withstanding that the web-site indicates it should be drunk 10-15 years from the vintage (and despite the bottle pictured clearing having a cork!).

It seems a bit odd, as I understood the whole difficult of developing synthetic corks was to match the permeability of natural cork, so that the wine could mature properly. However, the New Zealanders argue that the screw-top is in fact superior, precisely because it eliminates oxidation. Château Haut-Brion (remember them?) did an experiment in the 1970s, when they found that screw-caps worked well for about 10 years, but then tended to fail. It may be that the screw-caps have got better since then. Or it may be, of course, since people only started using them a decade ago, that they've only just reached the point of failure.

Be that as it may, the usage of corks vs screw-caps seems to divide more or less geographically. In New Zealand and Australia, as previously mentioned, screw-caps are near universal. In Europe, they tend only to be used on wine intended to be drunk young. In Portugal (which is where most cork comes from) screw-caps are almost unknown (although I have seen one on a bottle of Vinho Verde). The Spanish occasionally use screw-caps, but mostly seem to prefer cork (and in some cases cork is mandated by their appellation rules). The South Americans also seem to prefer corks.

Given that most wine is probably drunk within a few weeks of purchase, the effect of the stopper on the aging process is only rarely going to be important. Probably what matters more to consumers is that drawing a cork feels very different from unscrewing a cap. The former seems like more of an event, whereas the latter is very casual. It may even be that the popularity of screw-caps in the Antipodes is a reflection of their generally laid-back and unstuffy approach to life. This wine, they say, is not giving itself airs. Conversely, a cork might be thought to signify a more traditional wine, that takes itself seriously, and expects you to take it seriously.


( 1 comment — Leave a comment )
Jul. 3rd, 2012 10:05 pm (UTC)
I don't think I've ever been sure of a corked bottle; I suspect this means I've marked a few wines as "dreadful" that were in fact corked, but didn't know that the fault was being corked.
( 1 comment — Leave a comment )


Robert Jones

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