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Controversy mounts over best way to seal wine bottles

Will screw tops replace corks in wine bottles?

Date published: 9/7/2005

LET'S GET SOME closure. One of the most controversial topics in the wine industry is the use of natural cork to seal a bottle. There are many alternatives being researched, with varying levels of success.

Cork is harvested from the bark of a variety of oak tree, Quercus Suber L. The bark is usually harvested every nine years. More than 50 percent of the world's cork production comes from Portugal, where the soil and the climate enable the trees to live longer.

As a natural product, it is environmentally sound. The problem with cork is that it is subject to mold. This is caused by a chemical called TCA (2,4,6-trichloroanisole for you technical people out there).

TCA results from the reaction of natural mold in the bark combined with the chlorine used to sanitize the cork. Unfortunately it is impractical to detect this fault before bottling.

So, you may ask, what effect does this mold have on the wine?

Unfortunately there is a lot of bad information about the use of the term "corked." A corked wine isn't one that has a crumbly cork, or pieces of cork in the glass. "Corked" means that the mold has affected the cork and this affects the taste and smell of the wine.

I should add that this particular mold is invisible, so if you see mold on a cork, this is more than likely caused by seepage and is harmless.

So what's the solution? Therein lies the rub.

Many wineries have tried synthetic cork. Some are better than others, but one of the problems with synthetic cork appears to be a difficulty removing it from the bottle.

Australia has given us the Zork. It's a polyethylene cap and plunger, with welded aluminum foil to provide an oxygen barrier. So far, it appears effective, but the long-term effects on the wine remain to be seen.

Then we have the Stelvin closure. Yes, it looks like a screw cap to the untrained eye. It looks like a screw cap to the trained eye, too! That's because it is a screw cap.

Industry reports claim that this type of closure is effective. Indeed, many fine wines are now being sealed with Stelvins.

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Date published: 9/7/2005