Thirty years ago, pretty much all bottles of wines were sealed by cork. The ritual of removing the cork with a special tool – the corkscrew – with a gentle pop, has become part of the very fabric of wine appreciation. But of late, increasing numbers of bottles are sealed with screwcaps, or synthetic corks made of plastic. Cork is under threat.
Why is this? It is because a small proportion of bottles are ruined by what is known as cork taint. It's a musty, damp cardboard, old cellars sort of smell, and it affects around 1 in 20 bottles to a greater or lesser degree. In extreme cases, it makes the wine smell really horrible. In most cases, the mustiness is very subtle, but it's there, and it's a big distraction. Worse still, cork taint seems to rob the wine of its attractive aromas, sometimes without adding a musty edge: this is really bad, because drinkers won't realize what they are missing, and will just assume the wine isn't very good.
Where does cork taint come from? It's there because cork is a natural material, taken from the bark of the cork tree. In some bits of bark, there are fungi present that produce these musty taint chemicals, and because we are able to smell them at incredibly low concentrations, it's very hard for cork producers to clean the bark during the processing of cork to the degree that this taint is completely eliminated.
It was frustration with cork taint that led some wine producers to begin experimenting with alternatives. First they tried plastic corks, and then later they tried screwcaps. Both have benefits and both have drawbacks (we'll explore these in another blog post), but the great advantage is that neither taint the wine, and because they are manufactured they are consistent, eliminating the natural variation that comes with cork. Screwcaps, in particular, have really taken off in Australia and New Zealand, where most wines are now sealed this way – even expensive ones.
One of the benefits of alternative closures like these is that it has made the cork industry – based chiefly in Portugal – step up their act a bit and improve the quality of the corks they make. Cork taint still exists, but there's less of it than there used to be.