Is a wine with a screw cap closure a cheap wine? It used to be. Is it now? No way, Rosé!
Why are wineries converting in droves to screw caps rather than corks? Most New Zealand wines are now in screw caps, and many Australian wines have them. Even some Bordeaux and southern France wines sport them. Hogue Cellars in Washington State has shifted to 100% screw caps. All are switching to prevent a wine spoilage called "cork taint."
Cork taint is a chemical called TCA (2,4,6-Trichloroanisole) that is produced from yeasts in cork and even in the hold of ships that transport the wine. The yeasts interact with any chlorine-based chemical that might have been used in cleaning either the corks or the bottles (chlorine such as in Clorox® is a commonly used sterilizing agent). TCA produces a musty smell like wet cardboard. It has been estimated that anywhere from 1.5% to 7% of wines are "corked." Thus, wineries have a vested interest in avoiding wine recalls due to cork taint ruined wine.
The aroma threshold for detecting TCA is usually a few parts per trillion, but it can vary by several orders of magnitude depending on each person's sensitivity. My own sensitivity is blunted for TCA, while my wife can more easily sense and identify it. What's worse is that everyone quickly habituates to TCA , making the smell less obvious on each subsequent sniff. Therefore, one person's "corked" wine may not be another's. If it's not there on your second and third sniff, is it really a fault?
The Stelvin® wine cap made of aluminum and now with a plastic lining, is currently the most recognized screw cap wine closure. It has been commercialized since the 1970's. Tests have been conducted with even famous wines such as Chateau Haut-Brion, using the Stelvin closure. Those tests showed no difference in taste after at least 5 years with screw cap closure versus cork. In fact, the current caps close so well that some people have noticed that the wine has not seemed to age at all . Natural corks allow a small amount of micro oxygenation over years, which strongly contributes to the aging process and bouquet development. Screw caps do not allow in any new oxygen. In fact, sometimes they can prevent the natural leaching of hydrogen sulfide (burnt rubber odor) from a wine imperfectly made.
Synthetic corks are the other main alternative wine closure to natural corks. They also evolved in order to get rid of "cork taint." They have the problem that they are too sticky for easy removal from the bottle or the corkscrew. Also, injection molded synthetic corks allow very high levels of oxygen permeation in, when compared to natural cork and screw caps. Wines with synthetic corks are more likely to become oxidized over time than are wines with natural corks or screw caps.
What, then, are the pros and cons of screw caps on wines. As best I can tell, they are these:
Screw Cap Pros
o Lower incidence of "corked" wines
o Lower incidence of oxidized wines
o Preserves original taste very well for at least 5 years
o Can and should store the bottle upright rather than lying on its side
o It is more secure to carry home an unfinished screw capped wine than one with a cork
Screw Cap Cons
o Some bottles may leak if stored on their sides
o The wine will not age the same as wines with cork closures
o Occasionally may lead to burnt rubber smells in wines with excess hydrogen sulfide
It is unlikely that the great Bordeaux or Brunello houses are likely to switch from natural cork to screw caps since it would take a 30-year experiment to see how long term aging of a wine is affected. However, since over 90% of wines are meant to be drunk within a few years of bottling, we are likely to see a higher and higher percentage of wine bottles with screw caps -- that is, if we don't see more fine wines in bulk bags first! Life is a-changin', isn't it!
Rick Jelovsek is a retired physician, a Certified Specialist of Wine and a member of the Society of Wine Educators. He is also author of a book available from Amazon on "Wine Service for Wait Staff and Wine Lovers. you may contact him with wine questions at firstname.lastname@example.org .