By William LyonsIN A TEMPERATURE-CONTROLLED cellar with little damp, a good cork will be able to protect wine for several decades. The problem arises on those rare occasions when it doesn’t. Anyone who has built up a collection of fine wines over, say, 40 years will know that perhaps the biggest factor in maintaining their quality is the longevity of corks. At what age does one wear out and have to be replaced?
The answer lies in the quality of the cork. There are three main types. Regular corks are made from bark that’s stripped, without harm to the trees, from the cork oak, found in Portugal and the western Mediterranean. They come in a range of lengths, with the finer wines opting for a longer cork. Second is the agglomerated cork, made of fragments of ground-up cork bound together, either by the bark’s natural resins, released by heating, or with some added adhesive. Thirdly there are synthetic corks, made of plastic foam: Like screw caps and glass closures, these are really only used for wines with a short life-span.
Cork is an excellent material for stoppering wine. The Romans knew a thing or two about viticulture, and cork was used to seal amphorae throughout the Roman Empire. It’s impervious to liquid, long-lasting and doesn’t rot. There is, of course, the problem of cork taint. This arises, usually, through the contamination of the cork with a chemical compound called TCA (2,4,6-trichloroanisole). TCA is produced in the cork when airborne fungi encounter chlorophenols (perhaps deposited by industrial pollution), and it imparts to the wine an unmistakable pungent, moldy odor that I have heard described as anything from mustiness to a dank swimming pool.
“ Although cork creates an almost airtight seal, in fact a little air seeps through every year ”
Fortunately this is becoming less of a problem. The Portuguese suppliers have had to introduce many improvements to satisfy their ever more demanding client base, and some top Bordeaux châteaux are collaborating with them on technology that can check for TCA in corks.
Paul Pontallier, wine director at Château Margaux, says via email: “We’ve been working for the past two years with a renowned Portuguese supplier on this issue. They’ve set up a technique allowing them to test the presence of TCA in each cork without changing either its chemical or physical qualities. It is a significant step we would not have dared dream of only a short time ago! We will most likely be able to check most of our corks for the 2012 vintage.”
Although cork creates an almost airtight seal, in fact a little air seeps through every year. Over time, with tiny amounts of evaporation even under immaculate storage conditions, wine will lose volume. If the space in the bottle that’s not filled by wine (known as the ullage) has got down to below the mid-shoulder—around an inch from the base of the foil—it will usually mean some deterioration, and the wine could be spoiled by oxidation.
For owners of Australia’s premium wine, Penfolds, help is at hand in the form of their recorking clinics. Since 1991 these clinics, hosted by chief winemaker Peter Gago, have been held in various cities around the world, with more than 120,000 bottles being successfully resealed. Anyone with a bottle of old Penfolds can sign up for a session. The level of the wine is assessed, if necessary the wine is tasted, topped up with a small amount of young wine, and resealed with a fresh cork.
I recently attended one of these clinics in London, and it’s an impressive level of after-sale service. I couldn’t help thinking that I wish more top estates hosted events like these. But in the meantime, if you have wines in your cellar that you are concerned about, there may be nothing else for it—you may just have to pull the cork.