For hundreds of years, cork has been the gold standard for "stopping" wine. But now plastic stoppers and screw tops are challenging the tradition, and the benefits are causing even prestigious vintners and snooty wine reviewers to change their attitude from dismissal to acceptance.
About 50 percent of the world’s cork supply comes from forests in Portugal and Spain, where farmers strip the bark off cork oak trees for the wine industry. The bark grows back over 10 years without harming the tree. Environmentalists worry that switching to alternative stoppers will doom biodiversity-sheltering ancient cork forests. "Cork extraction is one of the most environmentally friendly harvesting processes in the world," says Pedro Regato of the World Wildlife Federation.
Cork’s inherent permeability allows oxygen to slowly enter the wine, and the subsequent reaction ages and matures the wine’s taste and aroma. But two bottles of the same wine can taste identical when purchased, but will age differently due to cork irregularities. A more permeable cork will cause a wine to age faster. Cork is also the root of the dreaded "cork taint," a chemical reaction that leaves wine with a moldy, musty or medicinal flavor.
But the alternative synthetic stoppers were originally dismissed by winemakers. They thought that if the bottle was sealed too tightly, no oxygen would reach the wine and it wouldn’t age. These fears have proven mostly groundless.
Now, fear of cork taint, along with a desire for more predictable aging, is fueling the market for synthetic stoppers. Plastic corks and screw caps, once red flags that signified low quality, are becoming more popular with premier wineries. Boulton claims that synthetic stoppers can assure uniformity.
John Conover of PlumpJack Winery in Oakville, California says cork mold ruined five to eight percent of his bottles before he switched to screw top closures eight years ago. Conover partnered with wine researchers at UC Davis to determine differences in the way cork and screw-top wines age. "So far, we haven’t seen a difference," he says.
Synthetic stoppers now make up 10 percent of the market, according to the Rainforest Alliance, which is alarmed by the growing popularity of plastic corks and screw caps.