Cork, the traditional closing method for wine bottles, is harvested from the cork oak tree (Quercus suber) and is elastic and watertight. It allows a tiny amount of air exchange, which is thought to prevent the development of reductive odours as the wine matures. Problems with cork hygiene from the 1960s when the wine industry was booming led to an increase in the frequency of cork taint.
True cork taint is due to 2,4,6-trichloroanisole (TCA), formed when certain phenolic compounds react with chlorine-containing compounds used as disinfectants. This need not result from the cork, as TCA is also found in barrels and other winery equipment.
If there is a high degree of cork taint, the wine smells musty (‘like wet cardboard’) and falls flat on the palate, without fruit or vibrancy. Some people are very sensitive to cork taint, others less so.
The increased frequency of cork taint prompted the development of alternative closures such as stoppers made from reconstituted cork, synthetic ‘corks’, aluminium screw caps, and glass stoppers with a plastic washer seal.
There continues to be a lot of debate and research into the ‘best’ closure. Some of the world’s most prestigious producers are carrying out longitudinal studies with a single wine under multiple closures. As the finest wines can take decades to mature, a definitive answer may have to wait a bit longer.
Meanwhile, the quality of cork is improving and instances of cork taint are less common than in the past. For many purists, the aesthetics of the customs, movements, and sounds associated with uncorking a bottle, and the quasi-Pavlovian association with care and quality, easily outweigh the small risk of cork taint.
Today more than ever, the presence of a true cork is an indication of a quality wine intended to improve with age.