Re-Examining the Screw Cap
Copyright 2001 by Robin Garr. All rights reserved. Originally printed July 25, 2001. For more information go to www.wineloverspage.com.
Many serious wine lovers find it hard to imagine using anything but the traditional, natural cork as a stopper for fine wine. This little plug of spongy Portuguese oak bark has been the custom for 300 years or so, and the ritual surrounding its extraction has become an important part of the mystique that makes wine something special.
But the natural cork has a dark side, and it has prompted a growing wave of consumer frustration in recent years: As we've discussed here before, a significant proportion of wine closed with natural cork will be spoiled by a fungus that "taints" the wine with a musty, unpleasant chemical called tricholoroanisole (TCA, for short).
This is why we're beginning to see a fair number of wines closed with stoppers made of plastic and other synthetic materials. And, particularly in Australia and New Zealand, some respected wine makers are experimenting with a closure that would have been unthinkable for quality wines a few years ago: The metal "screwcap," which many people associate only with inexpensive wines that come in large jugs.
Last week, the Australian Wine Research Institute presented its first report in an in-depth effort to determine exactly how wines fare in bottles closed with a variety of stoppers. The early results, while not entirely conclusive, strongly suggest that the lowly screw cap may work better than any other closure - including natural cork - to keep wine fresh and protect it from oxidation and "browning."
The Institute is testing about 8,000 bottles of Clare Valley Semillon, bottled in May 1999 with 14 kinds of closure that include two grades of natural cork, screw caps, synthetic polymer corks and "technical" corks made from a combination of natural and synthetic materials.
The wines are stored in a temperature-controlled facility and individually labeled with random codes. Every three months, a selection of wines are subjected to both lab analysis and tasting and the results recorded.
This process will go on for 10 years, but in the early going, the screw cap is showing well, holding the wine closest to just-bottled condition. The wines using synthetic corks held up least well; natural corks and synthetics did better, but were subject to the objectionable "cork taint."
The Institute published its initial report in the Australian Journal of Grape and Wine Research. Its news release is available online (in Adobe Acrobat format). Click here to get the News Release. The news release contains information on getting copies of the full 41-page report.