Why so few screwcaps in France?

Cork has been the traditional closure for wine bottles for hundreds of years. It works very well for the most part but it has a couple of disadvantages.

First, the cork can deteriorate in the bottle – sometimes disintegrating into dust and sometimes just becoming porous, allowing the wine to oxidise. Keeping the cork damp is the main way to reduce the chance of the cork deteriorating. This is why wine is traditionally laid down in cellars to keep the cork moist.

Second, cork can contain microbes which, when presented with chlorophenol compounds, can produce a chemical called trichloroanisole (TCA) which permeates into the wine and causes the distinctive smell of a mouldy paper that is known as cork taint. Such wines are said to be “corked”. As well as the unpleasant smell, the wine becomes unpalatable. TCA can spoil a wine at around four to six parts per trillion and even lower levels can make a good wine taste dull and lifeless.

The chlorophenols can come from certain pesticides used in cork forests, the presence of treated wooden pallets, and the use of chlorine as a cleaning product in wineries. In fact it is possible to infect a wine with TCA even without using corks if the TCA is allowed to form in the winery.

The cork industry reports an incidence of 0.5-1.2% of TCA whereas studies on wines have shown as high as 10% incidence of corked bottles. Cork can also vary widely in price and the general view is that cheap corks have more risk of TCA than expensive ones.

Alternative closures have been developed to remove these risks. They are mainly synthetic corks and screwcaps. They both have the advantage of not requiring the bottles to be laid down horizontally. However, they are not biodegradable like cork.

Synthetic corks are a simple replacement but have been thought to impart a plastic flavour to the wine. They are also only guaranteed for two years and can leak beyond that time. They tend therefore to be used for cheaper wines for early drinking.

Screwcaps have a much longer lifespan and do not appear to taint the wine, so they have been used for both low and high quality wines.

One argument for cork is that it is very slightly porous. The slow micro-oxygenation of wine has a beneficial effect on the texture of tannins and the development of bouquet in fine red wines.

Now, synthetic closures and screwcaps have been developed with slightly porous qualities although these are too new to the market to have sufficient track record and the vast majority of fine wine designed for ageing is still sealed under cork.

Another recent development is the DIAM cork. This is made from natural cork which has been broken down, treated with CO2 to kill the fungi that cause TCA and reformed using a neutral glue. DIAM corks can also be created with different levels of porosity.

One of the major decisions a winery must make about closures is perception in the market. Screwcaps were historically used on very cheap wines in both continental Europe and America.

So there is a prejudice against screwcapped bottles which deters producers from putting their better, more expensive wines in them. In the Southern Hemisphere and Britain, this prejudice has almost disappeared, although some traditionalists still prefer cork.

In upmarket restaurants, the ritual of opening a wine with a corkscrew is still seen as part of the experience and people have voiced objections to being charged a high mark-up on screwcapped wines.

On the other hand, a screwcap is much more handy for a picnic.

For the consumer, a screwcap should no longer be seen as a mark of an inferior wine, nor should a cork be a sign of quality and even the most expensive cork can have a risk of TCA, even though it will probably encourage the wine to age the most gracefully.

. Jonathan Hesford has a Postgraduate Diploma in Viticulture and Oenology from Lincoln University, New Zealand and is the owner, vigneron and winemaker of Domaine Treloar in the Roussillon.

www.domainetreloar.com