Food & Drink - Wine Corks
A romantic candlelit dinner for two, a single rose adorning the table, soft music in the background. The impeccably attired wine waiter proffers the bottle and, receiving a barely discernable nod of approval, carefully removes the cork. It ‘quacks’.
It is not inconceivable that the romantic sound of a ‘popping’ wine cork will be replaced by the not-quite-so-endearing sound of a ‘quacking’ plastic one. The revolution has already started, and you may not have even noticed!
So, what are those cylindrical things that keep the wine in the
bottle and why do we use them? What is ‘corking’? Where does cork come
from, and what are the pros and cons of plastic corks?
The ancient Egyptians knew that wine must be stored in airtight and
waterproof containers and used wax or a resin-like substance to seal
their amphora jars. In the Middle Ages, wines were kept in casks and
wooden stoppers wrapped in cloth ensured a better seal.
With the introduction of the glass bottle in the 17th century, wine
producers were forced to become more imaginative. Glass stoppers were
used in some areas, but they were expensive and impractical. Then a
certain Benedictine Monk called Dom Perignon came up with the idea of
using cork to seal his bottles of sparkling wine and, slowly, corks
became the standard way to seal bottles and ensure the easy storage of
wine in glass.
What is cork?
Cork is the bark of the Cork Oak (Quercus suber), grown in plantations
in Spain, Portugal and Algeria. All Mediterranean cork is sold to
Portugal, where a small number of manufacturers produce about 80% of the
world’s annual supply of wine corks (13 billion or so) and this industry
accounts for roughly 3% of their GDP.
Why cork?
Natural cork is a material with an unusual property in that it does not
expand laterally when compressed. In other words, it stays more or less
the same width when it is squashed lengthways, thus making it possible
to push it into the neck of a bottle. Most other materials swell
outwards when compressed and would, therefore, jam in the neck. There is
just enough outward expansion in a cork to make a good seal. In
scientific jargon, cork has a Poisson's Ratio very close to zero.
How is a cork made?
The bark is stripped from the tree and used to make the corks. This
process does not damage the tree, in fact the trees become so accustomed
to it that they can have serious problems if the bark is not removed.
The bark re-grows, and after nine years it is ready to be stripped
again. A mature tree can produce about 200kg of cork every nine years
and for as long as 200 years. Normal corks are just cylinders cut from
the bark. It is first seasoned for six months or so, then boiled to kill
any mould and insects. The corks are dried for three weeks then sliced
into strips. From these processed strips, corks are punched out and
polished.
Sparkling wine corks, by the way, are much more complicated. They
need to be much stronger than normal wine corks in order to withstand
the pressure created by all those fizzy bubbles. They are still
cylinders, but appreciably wider. The cork is layered to provide extra
strength and compressed laterally before being inserted into the bottle.
What is ‘Corked’ Wine?
Traditionally corks are bleached in chlorine, both to kill bacteria and
to improve the cork's appearance. However, a special mould (trichloranisole
or TCA for short) can grow from the leftover chlorine. It obviously
doesn’t affect all corks, and the exact reason for this is still not
known, but it does affect up to 8% of wine bottles. I say ‘up to’
because there is some divergence of opinion on this matter. Wine critics
tend to suggest a ‘contamination’ figure of between 5% and 8%, whilst a
study by the Wine and Spirit Association came up with 1.2%. They also
suggested that more problems are caused by oxidization, air getting to
the wine. Be that as it may, it is the TCA tainted bottles that are
referred to as ‘corked’. Although the cork is the prime source of TCA
taint in bottled wines, it is not the only source. TCA contamination can
occur at all levels of wine production from harvesting the cork (fungus
in the pores of the bark) to wine storage to bottling.
Small amounts of TCA result in a flat, flavourless wine, larger amounts make the wine totally undrinkable. The taste has been likened to chewing a ‘wet carpet’, but not being into such things I can’t comment, except to say there are obviously some very strange people about.
Corked wine is the prime reason for the tasting ‘ritual’ in
restaurants. You will certainly know if your wine is corked and you
should never be afraid to send it back and request another bottle. It is
also one of the main reasons for the increase in popularity of the
plastic cork, as wine manufacturers have to bear the cost of the, up to
8%, ‘undrinkability’ factor.
Plastic corks
One solution to the problem of corked wine is to use corks made of
plastic. These are becoming increasingly popular with wine
manufacturers, since they do not suffer as much from the problem of TCA
and are cheaper.
Although they are slowly catching on, it will probably be quite some
time before the old-fashioned cork bites the dust. In general, one
bottle in twenty now has a plastic cork. In the UK, the world’s largest
wine importer, the figure is one in three! This came about, in the main,
when Safeways Inc UK and Marks and Spencer initiated a natural cork ban
and signed a deal with an American company to supply plastic stoppers.
Reaction from the cork industry
Portuguese cork manufacturers have responded by promoting cork's unique
properties and spending an estimated 400 million euros on improving
quality. They plan to invest a further 500 million in their attempts to
save the cork. There are now factories with more computers than workers.
Corks are gauged by a dozen lasers and checked for flaws by electronic
cameras before being hermetically packed in sulphur dioxide to prevent
mustiness.
A German researcher has developed a process that essentially microwaves corks to kill internal moulds and a firm called Italcork claims its new cork-washing procedure results in a 99.9 percent taint-free product.
In the fields, great care is now taken to cut off the lower part of
the bark, a source of contamination by fungi and parasites that can
taint the wine.
The Cork Wars
There is a non-violent, but nonetheless voracious war raging between
proponents of ‘cork’ and ‘plastic’ wine stoppers. Environmentalists,
backed by cork farmers and the government of Portugal, have claimed that
cork farming is a sustainable industry in which the ‘art’ is passed down
from generation to generation, something that would be threatened if
plastic takes over. They also state that, in many cases, wine taint,
which is still not fully understood, is far too readily blamed on the
cork farmers and that it is no coincidence that the US plastics industry
is pushing hard for the replacement of cork as the US is the prime
producer of plastic stoppers. The multi-million-dollar industry leader
is a Seattle-based private firm called Supremecorq, which is rumoured to
have Microsoft monopolist Bill Gates as its star investor. A consortium
of California wine makers is backing Neocork, a plastic cork research
and development group headed up by the Dow Chemical Company, makers of
Agent Orange, pesticides and PVC plastics. Neocork expanded into Europe
in 2004, building a (plastic) cork printing and finishing facility in
Austria.
On the other side of the coin are claims by the pro-plastic lobby that this is all just ‘disinformation’ put out by greedy cork manufacturers who have brought about the present situation upon themselves. They say that the problems are being caused by the over-stripping of cork trees and the indiscriminate use of pesticides and chemicals at all stages of farming and production, especially during the 1960’s and 1970’s.
The biggest ‘coup’ for the plastics industry was almost certainly the
decision of Marks and Spencer and Safeways to instigate their natural
cork ‘ban’ in the UK. There are wine producers all over the world who
are now using plastic corks, even for some of their ‘vintage’ wines.
Whatever the truth, and both sides appear to have been guilty of ‘mis’
or ‘dis’ information in their efforts to win, the war will rage on for
quite some time to come.
The Pros and Cons
|
CORK |
PLASTIC |
|
Corks are more prone to TCA taint/contamination. |
Plastic reduces the risk of TCA to a minimum, although contamination can still occur from other sources in the wine making process. |
|
Corks made of natural cork are more environmentally friendly and degrade with time. |
Plastic stoppers are a by-product of the petroleum industry and their manufacture requires a large input of energy and creates pollution. They are not biodegradable and there are few, if any, recycling facilities for them. |
|
Cork is the natural product of a ‘tree’, and trees, naturally, have bugs, some microscopic, which can cause havoc without anyone ever knowing. Quality control of this ‘natural’ product is extremely difficult due to the random nature of flaws. |
Quality control is simpler with man-made products, although errors can still occur. |
|
Many flavours come from the known reaction between wine and cork |
Little is known about reactions, both short and long term, but there is a mounting body of evidence that plastic stoppers can react with wines to (adversely) alter the flavours. |
|
|
Wine experts' claim that plastic corks produce a very slight, but detectable ‘plastic’ taste to the wine. |
| The economy of Portugal may suffer, as 3% of its GDP comes from cork manufacture. |
The US economy will benefit as America is the manufacturer of plastic stoppers. |
|
|
Premature oxidisation and leakage are an issue, and can greatly reduce the shelf-life of the wine. |
|
The cork forests are home to many (up to 40) species of bird, some
of which apparently now only nest in these trees, and if these
forests are cut down there could be ecological consequences. |
Despite the fact that the wine is more likely to be drinkable, the wine-buying public are very conservative and ‘traditionalist’ in their attitudes, associating plastic with mass production, metal vats and other undesirable elements. |
|
The cork ‘pops’ when pulled from the bottle. |
The plastic cork doesn’t ‘pop’ when pulled from the bottle, it
‘quacks’. |
Some (polite) things to do with that pulled cork
1. Take it fishing! It can be used as an impromptu float, bite
indicator, holder for hooks so you don’t stab yourself.. and probably
numerous other things.
2. Use it as a pin-cushion.
3. Use it as a door-stopper.
4. Put it on the end of sticks and canes in the garden. How many people
manage to injure themselves because they don’t see the sticks once they
have put them in?
5. Have fun with the kids by making things like boats, animals, mobiles
etc.
6. Burnt cork is great (and cheap) make-up for Carnival, Halloween etc.
7. Use it to make old razor blades, Stanley knife blades etc safe by
pushing them into the cork before disposing of them in the rubbish bin.
8. Make a cork mosaic.
9. Hang them from your hat, like a real Oz, to keep the flies away! Bear
in mind, though, that if you are not actually an Australian or in
Australia, you will more than likely just be labeled a ‘prat in a hat’.
One final thought: if you are a regular wine drinker, and given that one
bottle in twenty now has a plastic cork, have you ever spotted one? And
does it really matter as long as the wine tastes OK? After all, the ‘box
of wine’ has been around for a long time.
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