The image of a glass bottle sealed with a cylindrical stopper punched from the bark of the Cork Oak tree Quercus suber is iconic; it's what people think of when they think of wine. The "pop" of a cork from a bottle, whether its contents are still or sparkling, is one of the most universally welcoming and celebratory sounds we have that isn't produced by the human larynx.
Sadly all is not well in wineland: natural corks, for all the effort we may put into preventing it, are prone to contaminating the wine whose wellbeing was the very reason for their pressure into service. Figures vary widely, I suspect by affiliation with or against the use of natural corks, but I've heard a low of around one percent and a high of ten percent of all wine bottles are "corked," or suffering from "cork taint." I myself have been bitten by cork taint a few times (not nearly one bottle in ten, but far too many times for my comfort). The most recent was this past Friday. The wine wasn't destined to be great in any event, but it was foul, and the cork showed the reason why: dark veins rain through its lower third, and told the nasty-tasting tale.
Hardly anyone who has bought a middle-to-low-end bottle in the past few years is unacquainted with one variety or another of synthetic cork, from the often colorful, obviously injection-molded plastic SupremeCorq, to the odd, extruded homage that is Nomacorc with its inner granular cells and outer sealed layer, to the Betacorque (which I have yet to see, or perhaps, yet to notice) which is fully synthetic, but nearly indistinguishable from a good agglomeration of natural cork bits.
The jury is still out on whether synthetic corks impart any sort of plastic "notes" to wines over time (I've never noticed, but my palate is young and still learning), and they're known for being slightly more difficult to extract from a bottle than natural corks, and most models are difficult or impossible to reinsert in a bottle after opening. The major benefit they offer outside of protection from cork taint is that they preserve the experience and simple theater of corkscrew extraction: that old squeak-and-pop. Oh, and manmade corks never disintegrate and leave bits in the wine, either.
Then there are screwcaps, the sad red-headed stepchild. The sight of a screw-top bottle of wine brings all sorts of associations with it: skid row; a cheap, paper-bag-wrapped, low-quality wine. Which is a shame, since it's becoming clear that a screwtop (the most famous is the Stelvin Closure) may just be the best way truly to seal a bottle of wine. There is some debate about whether allowing some oxygen to pass a bottle's closure is necessary to age a wine properly, but wine experts seem to be coming to the conclusion that wines age perfectly well when isolated from the outside world entirely, citing the examples of fortified wines sealed with wax, and wines retrieved from shipwrecks (article--search for "Closures in practice"). So even though there's a version of the Stelvin that allows some transfer of oxygen, that's likely to be gilding the lily.
What I've enjoyed most about learning about this topic is the amazing amount of introspection that the wine industry seems to be undergoing as regards the simple cork. Cork taint seems to be one of those things that has simply been accepted for the vast majority of the cork's life, possibly lending the opening of a bottle a certain element of mystery and risk. With wine maturing into an industry like any other, however, with the requisite drive to provide the consumer with a high-quality, uniformly consistent product, the vagaries of natural corking seem to be tolerated less and less.
Possibly the most telling quote I found was from George Fistonich, of the New Zealand group Villa Maria, near the bottom of a fascinating Wine of the Week article:
...the over-riding business rationale in changing from cork to screwcap is that we could prove that under cork closure, we were UNABLE to deliver on our mission statement [based on wine excellence].Fistonich has also declared that all of his wineries are now "cork free zones."
My guess is that sometime in the next 25 years we're likely to see natural cork relegated to the sidelines, and the landscape will be dominated by screwcaps, followed by a boggling variety of synthetic cork-esque stoppers.
Screwtops Prove a Winner