There are about 2,200,000 hectares of
cork forest worldwide; 32.4% in Portugal, and 22.2% in Spain. Annual production
is about 300,000 tons; 61.3% from Portugal, 29.5% from Spain, 5.5% Italy.
Once the trees are about 25 years old
the cork is traditionally stripped from the trunks every nine years, with the
first two harvests generally producing lower quality cork. The trees live for
about 200 years.
The cork industry is generally regarded
as environmentally friendly. The sustainability of production and the easy
recycling of cork products and by-products are two of its most distinctive
aspects. Cork Oak forests also prevent desertification and are a particular
habitat in the Iberian Peninsula and the refuge of various endangered species.
As late as the mid-17th century, French
vintners did not use cork stoppers, using oil-soaked rags stuffed into the
necks of bottles instead.
Wine corks can be made of either a
single piece of cork, or composed of particles, as in champagne corks; corks
made of granular particles are called "technical corks".
Natural cork closures are used for about
80% of the 20 billion bottles of wine produced each year. After a decline in
use as wine-stoppers due to the increase in the use of cheaper synthetic
alternatives, cork wine-stoppers are making a comeback and currently represent
approximately 60% of wine-stoppers today.
Because of the cellular structure of
cork, it is easily compressed upon insertion into a bottle and will expand to
form a tight seal. The interior diameter of the neck of glass bottles tends to
be inconsistent, making this ability to seal through variable contraction and
expansion an important attribute. However, unavoidable natural flaws, channels,
and cracks in the bark make the cork itself highly inconsistent. In a 2005
closure study 45% of corks showed gas leakage during pressure testing both from
the sides of the cork as well as through the cork body itself.
Since the mid-1990s, a number of wine
brands have switched to alternative wine closures such as synthetic plastic
stoppers, screw caps, or other closures. In some countries, screw caps are
often seen as a cheap alternative destined only for the low grade wines;
however, in Australia, for example, the majority of non-sparkling wine
production now uses these caps as a cork alternative. These alternatives to
real cork have their own properties, some advantageous and others
controversial. For example, while screwtops are generally considered to offer a
trichloroanisole (TCA) free seal they reduce the oxygen transfer rate to almost
zero, which can lead to reductive qualities in the wine. TCA is one of the
primary causes of cork taint in wine. However, in recent years major cork
producers (Amorim, Álvaro Coelho & Irmãos, Ganau, Cork Supply Group, and
Oeneo) have developed methods that remove most TCA from natural wine corks.
Natural cork stoppers are important because they allow oxygen to interact with
wine for proper aging, and are best suited for bold red wines purchased with
the intent to age.
The study "Analysis of the life
cycle of Cork, Aluminum and Plastic Wine Closures," commissioned by cork
manufacturer Amorim and made public in December 2008, concluded that cork is
the most environmentally responsible stopper, in a one-year life cycle analysis
comparison with the plastic stoppers and aluminum screw caps.
