About corks
A winemaker makes a great wine, puts it in a bottle, but next needs to decide how to seal the bottle. Sealing the bottle is about more than stopping the wine from spilling out. The amount of oxidation which occurs is dependent on the type of closure used. And the way the wine is stored varies based on the type of closure. Ask most people what type of closure they associate with a bottle of wine, and they will probably say a cork.
The main benefit of using a cork is that while it is largely liquid tight, it is not 100% air tight. This means a small of oxygen can get through it, make contact with the wine, causing desirable oxidation. This adds some of the flavours we associate with aged wines. Flavour of dried fruit and nuttiness can come from oxidative aging.
Cork actually comes from a tree. These trees are very common in Portugal. It can also be found in other European countries and Northern Africa. The cork is essentially the bark of the tree. The pictures show a pile of the bark which had been harvested from a Cork tree. This was taken during a trip to Portugal, and a visit to a cork factory.
In order to harvest the cork, the workers will only collect is between May and August. Harvesting it during this times means the tree is not damaged during the collection of the cork. The traditional method of harvesting begins with making an incision into the bark. The axe is the twisted in order to get between the bark and the tree, splitting off the cork bark. Cork bark can only be harvested every 9-12 years and a typical tree will be harvested around 15 times. In this sense corks are very sustainable.
In order to get sheets of cork, the bark is pressed under concrete slabs to flatten it. It is then boiled to sterilise it. Not all cork is used to make corks, cork is a popular material for another of other purposes. In recent times, it has become popular for its sustainable credentials. The best cork (usually that from the third harvest onwards) is to make wine bottle closures. Corks are cut out from the flat sheets, with a typical tree producing between 3-5,000 corks.
The lower quality cork, can still be used to create corks. The cork broken into smaller pieces, like sawdust and then glued together. These corks are known as agglomerated corks. It is also possible to glue together larger pieces of cork to make a cork. With modern techniques, corks can even be designed to allow a certain level of oxygen to pass through.
What is a corked wine?
Many people believe a corked wine is when the cork has disintegrated into the wine a pieces of cork are found in it. In fact, a corked wine is one where the cork has become affected by a type of fungus. The fungus is known as 2,4,6-trichloroanisole or (TCA). You cannot, therefore really see a corked wine. But you can almost smell it. It will smell musty and of wet cardboard or ‘wet dog’. You likely won’t get as far as drinking it, but if you do it will taste of compost.
Despite the emergence of other types of sealant for bottles, and other types of vessels for storing wine, most wines still come with a cork. Around 70% in fact. And while cork taint (being corked) used to be a problem, now its actually quite rare, although not impossible to get a corked wine.
There is a bit of a stigma in some wine circles around screw top wine bottles. In many cases this is misplaced. The vast majority of wines are made for pretty much immediate drinking, and so do not really benefit from oxidative aging. A screw top in a white aromatic white wine is a good thing in my view, it keeps it fresh and vibrant.
While a lot of cheap wines have screw tops, so do a lot of very good ones, so a cork is rarely an indicator of quality. Perhaps only in as much as if a producer is prepared to shell out the extra cash for a cork, they probably aren’t cutting any corners on costs elsewhere either! However, most wines for aging likely have a cork. And many wines for aging are also the ones people tend to think of as high quality.
So now you know where the humble cork comes from, how corks are made, and why they are used. Of course, there is one advantage of a screw top, we’ve not discussed… You don’t need a cork screw to open the bottle! So next time, you’re removing a cork from a bottle, enjoy knowing that even if it splits, the wine is probably not corked! In the meantime, keep exploring this beautiful planet we live on, one glass at a time!