Corks & Cork Alternatives
The greatest enemy of wine is oxygen. It rots it—in short order and without fail. All those who make wine (and many who drink it) have known this for millennia. Accordingly, these same folk have sought to prevent the oxidation of wine.
In primitive times, they floated a layer of olive oil over wine. Or they sealed wine in animal skins, or in amphorae, the openings closed against the air with wooden discs or stoppers wrapped in pitch-soaked cloth or rung ‘round with wax.
Then … someone found cork, an ingenuity of nature unlike any other. Cork is formed of 14-sided, liquid- and gas-impermeable cells—655 million per cubic inch—which recover 85% of their initial volume immediately after compression and 100% within 24 hours.
Photo by Oscar Soderland on unsplash.com
Beginning in the 17th century, due primarily to advances in glass blowing that allowed for thin but durable and uniform bottlenecks, the bark of the cork oak, Quercus suber—peeled, washed, dried, cured, bleached and punched into cylinders—became the ne plus ultra of bottle stoppers. Nothing could beat it.
Where from
Quercus suber needs 15-30 inches of rain a year, delivered at an altitude between 330-1,000 feet, and in ambient temperatures never below 23° F—in effect, the western and central coasts of the Mediterranean and Portugal.
Portugal, Spain, Algeria, Morocco and Tunisia (and, to a lesser extent, Sicily, Sardinia and Corsica) farm and finish nearly the entirety of the world’s cork, with Spain and Portugal between them sharing 80% of total global production.
An Achilles heel
Turning cork bark into wine corks hasn’t changed much for centuries. One step uses bleach in order both to disinfect the cork and to give it a uniform look.
However, it’s now known that the most common bleaching agent, chlorine, encourages certain microorganisms in cork to produce an element that spoils wine. That substance is 2, 4, 6-trichloroanisole (or—blessed acronym—TCA).
TCA causes the wines that it taints to smell and taste musty or moldy, as in a dank, mildew-y basement. It also mutes wine’s flavors by half or more. When affected by TCA, a wine is said to be “corked.”
Current estimates of corked wine range from 2%-7% of all wines bottled (under natural cork). Approximations of the cost of wine spoiled by cork taint range from $100-$200 million dollars a year in the United States alone.
But cork is not alone. Scientists also have determined that TCA resides in other winery sources, too, especially wood, from barrels to ladders to tools.
While TCA poses no harm whatsoever to human health, and while TCA is ubiquitous—in wood products and paper, in other beverages such as common chlorinated drinking water, cider, bottled water, beer or orange juice, in foods such as olive oil, bananas, peaches and pre-peeled baby carrots—TCA definitively makes wine yucky*.
Of course, cork producers diligently have looked for new methods of disinfecting and whitening cork bark, such as steam or hydrogen peroxide. However, no method yet has enough of a track record to prove itself a profitable or aesthetic substitute for chlorine
Alternatives to cork
Winemakers have turned to other closures in order to avoid TAC taint—crown caps (as for soda pop bottles), agglomerated and plasticized corks, synthetic extruded “corks,” and the up-and-coming aluminum screw cap, the most popular brand of which is Stelvin®.
Just as natural cork bark has its plusses and minuses, so do these alternatives have theirs. Many consumers turn up their noses at non-cork stoppers. Some winemakers believe that synthetic closures prematurely age, or even “reduce**,” wines.
What’s ahead
In any case, non-natural wine stoppers (especially screw caps) are on the rise, spearheaded by the indefatigable Australians and New Zealanders who screw cap everything from $5 Rieslings and Sauvignon Blancs to their rare reds.
What is sure about the future of artificial wine bottle closures is uncertainty. Much depends on how wines age long-term under them. The amount of time sufficient to test that has not yet passed by.
* Perception of TCA varies, so that one person might recognize it at one level whereas another person might not. Science suggests that perceptible levels of TCA range from 4 to 6 parts per trillion. It’s interesting that some award-winning wines have contained TCA detectable by scientific instruments, though not by the human nose. Also, other variables such as the volume of alcohol can govern TCA perception in wine.
** The chemical reaction that is the opposite of oxidation, in which wine suffers a sort of “asphyxia” from being in an anaerobic environment and which can result in “dirty” or sulfuric aromas and tastes. Reduction is more common in reds wines than white and, in white wines, more prevalent in certain wines (Sauvignon Blanc, for example) than others (Riesling, say).