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Introduction
Cork
is a remarkable natural substance. Because of its cellular wall
composition and structure and it has elastic and compressible qualities
that make it ideally suited to sealing wine bottles. A decent cork will
provide a good seal on a wine bottle for thirty years, possibly longer,
allowing the wine to develop and mature into something special. And
despite corks providing a good seal, it’s relatively easy to extract
them using one of a wide array of different designs of corkscrew. Added
to this, taking the cork out has become a valued part of the tradition
of wine. It may sound silly, but there’s something special about
uncorking a bottle. So
what’s the problem? The dirty secret of the wine trade is that one in
twenty bottles of wine is ruined as soon as it is bottled by problems
with the cork. Chief among these is what is known as ‘cork taint’.
This is when a wine takes on a musty odour caused by a chemical called
2,4,6-trichloroanisole (TCA) that is present in some corks. TCA itself
is produced by microbes that live in the small pores, called lenticels,
that run throughout cork bark. In extreme cases it’s hard to miss a
‘corked’ wine: the mustiness can sometimes be overpowering. In other
situations the taint is more subtle, reducing the fruitiness of the
wine, giving it a subdued aroma, usually with a faint whiff of damp
cardboard or old cellars in the background. The
problem with TCA is that it is incredibly potent: most people can detect
it at concentrations as low as 5 parts per trillion, which makes it hard
to eradicate. To give you a better idea of this figure, it’s
equivalent to one second in 64 centuries. Where good data have been
collected, the frequency of cork taint hovers around 5% of bottles
sealed this way. The other main problem with corks is that because they
are a natural product, they are variable, and some fail by letting
oxygen in which then spoils the wine. Cork
taint hasn’t always been such a big issue. In the past it is likely
that many people weren’t as aware of the problem and happily drunk
corked wine. But with the increasing quality of cheap wine (which makes
any taint more likely to be spotted) and the fact that consumers are now
generally better informed, a vocal body has sprung up who have decided
that they’re not going to put up with this situation any longer.
So
what are the alternatives? Surprisingly, modern science hasn’t been
able to come up with a synthetic substance that shares cork’s
properties of elasticity and compressibility. While there are a number
of synthetic corks on the market, they’re really only suitable for
wines destined for immediate consumption (that is, within a year or
two). The problem has been that the plastics used can’t provide a seal
equal to that of real cork without being impossible to extract from the
neck of the bottle. The result is that plastic corks tend to be
permeable enough that the wine tends to oxidise after a couple of years,
although they are fine for everyday wines that are usually drunk on
release. Of course, it should be pointed out that some makes of plastic
cork are more efficient than others, and product development is
occurring all the time, so we may yet see serious plastic alternatives
to corks (they may already exist, although I haven’t yet seen good
data indicating this). For now, then, the leading contender to cork is
therefore the screwcap. Screwcaps
provide a pretty good seal—better than cork, in fact. And they are
easy to open: you don’t need a corkscrew, you just twist them off.
Because they are manufactured and not a natural substance, they provide
a much more uniform seal than corks. Added to this, there are plenty of
reports of 20 year old screwcapped bottles being opened and the wine
tasting fresh and lively. So
how come all wines aren’t sealed with screwcaps? This is what a vocal
element in the wine trade are calling for, after all. There are three
main problems. First, screwcaps have a ‘cheap’ image in the minds of
many consumers. People associate screwcaps with bargain basement plonk.
Some markets, particularly those in traditional European wine producing
countries, are highly resistant to alternative closures such as
screwcaps, whereas others, such as Australia and New Zealand, are more
accepting. Second, people like corks. They’re natural, they look and
feel right, and the ritual of getting the corkscrew out is part and
parcel of the wine drinking experience. Thirdly, while most experts
agree that the screwcap is the closure of choice for fresh white wines
and easy drinking reds, there’s some debate about whether they are
suitable for red wines destined for long ageing. The
reason for this doubt is that people like the way that fine wines evolve
over time when they are closed with a fault-free cork. Screwcaps provide
a better seal than cork. The question is, is this seal likely to be so
good that it prevents the wine from ageing properly over, say, 20 years?
Wine ageing is a complex process that takes place largely in the absence
of oxygen, in what is called a ‘reductive’ environment. But could it
be that the trace amounts of oxygen that get through the seal provided
by the cork are an intrinsic part of the ageing process? The scientists
don’t know for sure, and as yet no one has done the proper experiments
that will settle this issue once and for all. However, it is worth emphasizing that only a very tiny fraction of the wines made worldwide will require extended cellaring. For almost all other wine styles, the screwcap is likely to be the optimum closure. It’s likely for one reason and another that cork will always be with us, but unless someone comes up with a cure for the curse of cork taint, expect to see screwcaps gaining ground over the next few years. ©
Jamie Goode, 2004 This
article is a modified version of a piece written for Hong Kong Tatler,
January 2004 |
Have
you noticed the increasing number of wine bottles sealed with screwcaps,
and wondered why? It’s because of a small war that is taking place.
Over the last few years, the wine trade has been embroiled in a
conflict. You wouldn’t have thought that the rather boring-sounding
issue of bottle closures would inflame passions, but it has, and to a
remarkable degree. One the one hand we have the traditionalists who feel
that cork is the only decent way to seal a wine bottle; on the other we
have the screwcap crusaders who are on a mission to eradicate cork and
have all bottles sealed with alternative closures. Who’s right?