Do Screw Caps Stink?

For wine lovers who hatted to see the increased use of composite corks at the expense of natural cork, the massive wave of synthetic corks was unsettling. No sooner had they started to come to grips with plastic corks then they started to experience the rapid rise of the screw cap.

At several recent dinners in upscale restaurants I've seen guests give an odd glance as a waiter unscrewed the cap of a bottle of wine. Most of these wines have been whites from New Zealand and Australia, but producers of reds from California and elsewhere are turning to screw caps in massive numbers. We have all been assured that a screw cap does a perfectly fine job sealing a bottle of wine. Now a new study suggests that it might do too good of a job.

British researchers found that 2 per cent of screw cap bottles had a rotten egg odor when they were opened. The smell is produced by a chemical process called reduction that takes place in most wines in a bottle. The problem is that the screw cap apparently seals the odor inside the bottle, while natural cork is porous and allows some of the odor to escape and oxygen to dilute the smell.

The research was conducted on 9,000 wines using screw caps at the International Wine Challenge. The rotten egg or sulphidisation odor was present in 2.2 percent of the wines opened.