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Get a brief overview of cork basics with the Great Wines Online!
Corks have been used as bottle stoppers for as long as we have had wine. The Greeks in the
fifth century BC sometimes used cork to close wine jugs. Following their lead, the Romans
used corks as stoppers, adding a pitch to seal the closure.
Corks, however, did not predominate in those days. The most common closure for wine jugs
and amphora was a coating of pitch or gypsum over the opening of a vessel and a film of
olive oil floating on the surface of the wine (to minimize oxygen contact with the wine).
The use of corks was apparently abandoned completely in medieval times. Paintings from that
era depict twists of cloth or leather stopping a jug or bottle, sometimes with sealing wax
used to make a secure closure.
The marriage of cork and bottle took place during the first half of the seventeenth century.
The alternative closure of the time, stoppers (stopples) of ground glass made individually
to fit each bottle neck, held its own for a remarkably long time. As late as 1825, these
stopples were still the closure of choice. Eventually, these glass plugs were abandoned
because they were nearly impossible to extract without breaking the bottle. One thing
remained problematic in cork's widespread use as a practical bottle closure: an implement
that could be driven right into the cork and easily extracted along with the cork. The
first mention in print of the instrument now know as the corkscrew was in 1681. It was
described as a "steel worm used for the drawing of corks out of bottles." This handy tool
had been in use 50 years for drawing bullets and wadding from firearms (and was originally
called a bottlescrew.) "Corkscrew" was not coined until 1720.
The Source of Cork
Quercus suber is the botanical name for a kind of slow growing, evergreen oak that
flourishes only in specific regions of the Western Mediterranean world. This tree requires
a great deal of sunlight and a highly unusual combination of low rainfall and somewhat
high humidity. The quality and thickness of the bark vary according to a tree's specific
growing conditions.
Cork evolved as the tree's spongy protection and insulation from, in particular, fire.
Most trees die if their bark is removed, because bark helps to carry sap that is essential
to the tree's life. The cork oak, however, has two layers of bark. The inner layer is alive
and is the base on which a new inner layer grows each year. As the old layers move outward
and die, they serve as growing areas. The dead outer layer can be stripped away without
injuring the tree, but care must be taken not to penetrate the inner living bark.
The first harvest of cork cannot take place until the tree is 25 years old. Cork from the
first harvest is irregular in size and density and is not suitable for wine stoppers. It
is usually used for floor tiles or sound insulating materials. Nine years must pass before
the tree can be harvested again. Even cork from this second harvest is not good enough for
wine bottle stoppers. It is not until the third harvest -- when the tree is 52 years old --
that the regularity of size and density of cells renders the material acceptable for wine
bottle use. A cork tree generally yields between 13 and 18 useful harvests in its lifetime.
The cork bark is stripped by hand with the aid of small sharp axes, and the resulting cork
strips are then stacked and weathered. The tree itself is carefully marked and numbered so
future harvesters know when a particular tree can be harvested again.
Once in the factories of Portugal for processing, the cork is stacked and aged an
additional three months to let it weather and dry. Proper moisture content is crucial for
the elasticity and compressibility of the cork. After this drying period, the cork is
immersed in boiling water for at least 90 minutes to sterilize it and to enable it to
flatten from its original curved tree trunk shape. After boiling, the corks "ripen" for
three to four weeks in order to achieve the desired moisture level. Next, the material is
trimmed into strips, and holes that match the size and shape of the bottle cork are
punched into it. This stage of the manufacturing process requires a keen eye as the hole
punchers maneuver the strips for maximum quality. Next, the cork heads are polished so
that the cork will have a specific, uniform length. The body is also polished so it will
have a specific, uniform diameter. It should be noted that the width of the bark strip
forms the diameter of the cork, not the length. Thus growth rings of the tree are to be
found imbedded longitudinally within the cork. The corks are then washed and dried. Most
are bleached in either chlorine or hydrogen peroxide in order to disinfect it and rid it
of remaining impurities. Some are rinsed without bleach, depending on specific wineries
requests. Corks are graded for quality, and branded with the purchasing winery's name. A
final surface treatment, either silicone and/or paraffin or a resin, is sprayed or tumbled
onto the cork's surface. This treatment eases insertion into the bottle and improves the
seal against the glass. The corks are then bagged in plastic and shipped to their final
destination.
There's a Problem
Corkiness -- a condition that rears its ugly head when wine is tainted by the presence of
a chemical compound called 2,4,6- Trichloroanisole -- TCA for short. This compound appears
to be caused in the cork by interaction of moisture, chlorine and mold. From the harvest
of the cork to the bottling of the wine, the cork can be exposed tothese three elements,
and TCA can form. The human nose can detect this corkiness at concentrations as low as four
parts per trillion. A lightly corked wine may simply smell like cork, while a badly corked
one may smell musty, like damp carUser_ACB23Card or old newspaper. The usual rich aroma
and flavor of fruit and oak is stripped away by the musty odor. A corked wine poses
absolutely no health problems -- it just doesn't smell or taste good. The ultimate problem
lies in the fact that good money has been spent on a bad bottle of wine, and there is
absolutely no way of knowing this until the bottle is opened. A reputable vendor will
replace a tainted bottle.
Cork Alternatives
About six percent of the wines submitted for review to Wine X Magazine suffer cork-related
defects. So why does the industry continue to use a faulty closure device?
The revered tradition of cork as a wine bottle stopper will die hard and slowly. Even
though many find the use of cork an elitist holdover that renders opening a bottle a
difficult and esoteric process -- as is the intimidating ritual of cork sniffing in
restaurants -- the image of screw caps still conjures up images of "cheap wine." So what
is the answer? There are plastic, synthetic corks made of ethylene vinyl acetate,
trademarked as Cellukork. These closures look and feel similar to real cork and require a
corkscrew for removal. However, there are two drawbacks: one is that Cellukork often fits
so tightly in the bottle that it is very difficult to remove -- a problem sure to be
resolved through research. The other potential concern is whether the synthetic material
truly remains non-reactive and inert over long periods of time. Will it impart flavors to
the wine? There are obviously concerns for those who cellar wine over a long period of
time. Wineries experimenting with these plastic corks are deliberately aging wines to see
what happens, but it will be several years before outcomes are known.
So we turn back to the screw cap. It provides an excellent air-tight seal. It is very
consumer friendly – no more struggles if you forget the corkscrew. It also gives wine a
down-home feeling by removing the intimidating "elitist" image with which it is so often
associated. Thus screw caps can make wine more accessible, both figuratively and literally.
The problem? Again, aging. There is a question as to whether screw caps protect wine over
a very long period of time. As yet, no conclusive tests have been conducted. But the major
problem is that many quality wine producers -- sensitive to the fine wine market --
hesitate switching to a screw cap because they do not want their product to be perceived
as inferior quality. Again, this is only an image problem created by the industry itself.
The Answer
Because of worldwide concern with the perceived degradation of cork quality and the
tremendous impact it has on the cork industry, a group of U.S. cork suppliers founded
the Cork Quality Council (CQC) in 1992. Its mission is to improve the quality of corks
at the source, to build an educational program to assist wineries and to develop industry
standards for cork quality. And research with synthetic corks continues. Many wineries are
now experimenting with these plastic closures and, if no problems manifest, many more will
probably follow suit.
Regardless of what closure a bottle of wine contains, the ultimate experience should come
from the wine itself. Whether we pull a cork, twist a cap or access that wonderful nectar
through some other means, the most important thing is the quality and enjoyment wine
brings to everyday life.
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