🍷 Cork (stopper)

A cork (cork stopper) is what plugs the neck of a wine bottle. It stops the wine from leaking and limits how much air gets in. The best-known kind is cut from the bark of the cork oak, and Portugal and Spain supply most of that bark.

The tree is never felled for it. The bark is stripped and grows back. The first harvest comes when the trunk measures 70 cm round at 130 cm above the ground, which takes about 25 years. After that the tree is left alone: stripping it more often than every nine years is forbidden. APCOR puts Portugal at 46 % of world bark and Spain at 33 %.

There are many kinds of stopper. APCOR lists eight groups, from the one-piece Natural cork to Agglomerated cork pressed from granules and the Sparkling wine cork. Beside them stand the Synthetic cork, the Glass stopper and the Screw cap, and over the neck a Wine capsule is often fitted.

By the AWRI's estimate, cork-based closures hold about 70 % of the world market. Screw caps and synthetics split the rest almost evenly. In Australia, screw caps seal about 90 % of bottles. A screw cap lets through the least oxygen and does so steadily, while natural cork varies a lot with its grade.

Cork's best-known trouble is taint. The main culprit is trichloroanisole (TCA), formed when mould on the cork works on chlorophenols. Consumers reject a wine at 3.1 nanograms per litre. Yet the AWRI has shown TCA can form in oak too, so cork is not always to blame. For the wider picture of wine containers, see Packaging, vessels and serving of wine, and for the fault itself, Cork taint. See also wine.