What's the Story With Wine Corks
Corks and several other types of stoppers have been used to seal wine bottles for centuries. However, cork has withstood the test of time and today is the near-universal closure of wine bottles globally.
The Wine Cork
The evolution of cork as a stopper started in the late 1600s when glass bottles of uniform design and shape appeared on the scene. However, the initial corks were cumbersome and impossible to unscrew. It was only in the 1700s when more refined corkscrews became available that the use of cork stoppers started to spread. By the 17th century, the cork had replaced glass and other exotic stoppers.
Another fascinating point is that corks are made from the cork oak tree, the majority of which are found along the Mediterranean (Portugal and Spain.) The cork trees are quite tall, reaching heights of up to 50-60 feet, and vary in thickness from 10-12 feet when fully mature.
The law is that the cork oak tree must be at least 25-34 years before the first harvest. The cork oak tree can regenerate the outer bark, which allows for the tree to be harvested once every ten years. To ensure that the same tree is not harvested repeatedly after the first harvest, the trunk is marked in white and dated, so that the farmers know when it can be harvested again.
After the harvest, the making of cork is a long process that includes drying and sterilizing the cork. Once the bark is soft, it is reshaped so that it can fit a wine bottle. Some corks are lightly coated with wax to ease the fit into a bottle.
Wine corks became popular in the 17th century as they were relatively cheap to manufacture and much easier to remove from the wine bottle compared to glass. Another positive about corks is that when they are used to seal the bottle, they retard the oxidation process and allow the wine to age with time. This is because corks permit only a tiny amount of air to enter the wine bottle. This is important because if oxygen enters the bottle, it will oxidize the wine and lower the quality.
Besides cork, other alternatives to close wine bottles include screw caps, which is a common practice in Australia. Other places to try screw caps include Napa Valley, the Bordeaux region, and the Rhone valley. Again, the screw cap fit must be perfect to prevent air from entering the wine bottle.
A bit more about wine corks vs. screw tops: The porous structure of the cork lets in minute amounts of oxygen to the wine, which can be helpful – in very small doses – to the wine. Screw tops, on the other hand, don’t let any oxygen in and many believe they should only be used with wines that should be drunk “young.” Even though natural cork closures have a long and varied history, there is still that potential TCA issue that can cause the aroma of the wine to be unpleasant.
Synthetic corks made from plastic are now being used to seal wine bottles. They look exactly like cork stoppers, but the problem is that the seal is not always perfect, which permits air to enter the bottle. Another issue is that these synthetic corks are known to release a minute amount of chemical or rubbery smell that can ruin the aroma of the wine.
So, wine corks do not always last forever. If the cork starts to degrade, it also leads to more air entry into the bottle, which results in premature oxidation of the wine. Many professional wine collectors who have expensive and rare bottles of wine regularly replace the old corks with new corks.
The lesson: if you open a bottle of wine and will not finish it, place the cork back quickly; otherwise, the air will oxidize the wine. Most wine bottles, once opened, will last 3-5 days if kept refrigerated.