To Cork or Not to Cork? The Great Wine Closure Debate

Veritas Vineyard in Afton uses a variety of closures for its wines. (Photo: Clover Carroll)

“A meal without wine is like a day without sunshine” declares an old adage, attributed to 19th century French gastronomer Jean Anthelme Brillat-Savarin. And the soft “pop” of the cork leaving the bottle is a ritual sound enjoyed by many. But does the squeak of an aluminum screw cap inspire the same anticipation? Should a bottle of fine wine be served up the same way as a jar of pickles? As the use of screw caps and synthetic “corks” continues to increase, I began to wonder what effect these new technologies have on a wine’s quality and flavor. Not only did I discover that the answer is anything but simple, but I also stumbled upon one of the hottest debates in the wine world, with ardent proponents on both sides.

On one side are the European traditionalists, who have been using natural corks to close wine bottles for centuries. They prefer this natural, organic, and renewable resource—hand harvested from oak bark, mostly in Spain and Portugal— with its long-term, proven success in aging wine gracefully. On the other side are modern proponents—led by Australia and New Zealand—of various cork alternatives that are significantly cheaper, easier to use, and that reduce the risk of spoilage—synthetic closures that may be recyclable, but are not biodegradable. The burgeoning U.S. wine industry falls somewhere in between. “It’s time for a more modern and consistent way of doing things,” declares

As Andrew Hodson, owner of Veritas Vineyard in Afton, explains, wine production involves three stages: the primary stage of extracting the juice from the grape; the secondary stage consisting of fermentation with yeast, and the tertiary stage, when the wine is aged over long periods of time. The oak barrel—one of the most expensive elements in wine-making—is a semi-permeable membrane, which permits the exchange of oxygen that allows the wine’s more complex flavors and textures to develop and evolve. “Oxygen is what ages wine. Microscopic amounts of fresh air seep through the wood, allowing it to age slowly,” he observes. Almost all wines are aged at least six months before being bottled and sold—most far longer.

But the aging of wine continues in the bottle. The cork, like the barrel, is also a semi-permeable membrane that allows small amounts of oxygen to enter so the wine can continue to evolve over time. Red wine—which includes the skins of the grapes—is naturally more complex than white wine, partly due to tannins, which impart bitterness and astringency (a dry mouth feel) to the wine. As a red wine ages, oxygen acts as a stimulus for the tannins to polymerize (or “link up like Legos” as Hodson described it) which reduces their bitterness.

“The screw cap allows no oxygen to enter the bottle, so the aging process stops there,” explained Colleen Miller of the Blue Ridge Bottle Shop in Piedmont Place. “It is good for younger wines, but not for old reds that need to breathe.” Hodson agrees. “The aluminum screw cap is fine for wines costing less than $20/bottle,” he explained, “but not for premium or high quality wines costing $25 and up.” While the type of closure is more important with red wines, it matters for all “premium” wine, softening the tannins in red wine and reducing the acid in white wines to create a more mellow, buttery flavor. Aging also allows the various flavors in the wine to develop and stand out, resulting in “the nuances of a high-quality wine.” White wine is typically aged 1-2 years; red wine is aged 5 or more. For the same reason, Hodson argued, you do not need to aerate a red wine that is under 5 years old.

Traditional European winemaking methods were established in the 1400s, and closures did not change much until the 1950s. While the natural cork allows the wine to breathe, it can also lead to a condition called trichloroanisole (TCA), commonly known as “cork taint.” “TCA is a chemical compound of phenols, chlorine and mold…[that] will taint the aromas and flavors of the wine, resulting in musty odors…. Most wine insiders estimate between 3 to 5 percent of all wine is affected by TCA” ( During the 1950s and ’60s, wine makers began turning to various synthetic alternatives, primarily to reduce spoilage in their corked wines, but also because they were cheaper. While a natural cork costs 11-13 cents a bottle, an aluminum screw cap costs only 7 cents a bottle—about half as much. Screw caps are also easier, both in the bottling process and for the consumer to open. Australia and New Zealand have gone almost entirely to the use of screw caps to close their wines. Since the leading producer of these is Stelvin, the wine literature refers to these wines as being “under Stelvin.”

Cork and screw cap closures on wine bottles at the Blue Ridge Bottle Shop in Piedmont Place. The wine on the left costs $40; that on the right costs $13. (Photo: Clover Carroll)

Some say air-tight screw caps can “suffocate” wine, but screw cap manufacturers have answered this complaint with new technology: “Today you can buy screw caps with calculated levels of ‘oxygen ingress’ over time” ( Moreover, there is now a third alternative to the cork or screw cap: synthetic corks. While purely plastic cork acts the same as a screw cap, a French company has developed a hybrid of cork, beeswax, and vegetable polyols called “Diam,” that claims to allow natural aging and eliminate the risk of TCA. “Diam is opening the way because of how it looks—it is a processed cork and if you look closely, you can see the cork pieces that make up the closure that on first take looks like a natural cork” (

In other words, it is no longer possible to tell what is purely natural cork and what is not. “[When] you buy an affordable wine at the grocery, more often than not it won’t be a 100 percent natural cork. Instead, the bottle will be closed with a technical, agglomerated, and colmated cork, which are low quality alternatives to natural cork” ( Many prestigious vintners are now selling even their premium wines “under Diam.” Per a 2014 report from the University of California/ Davis, synthetic corks now close 60 percent of the top 500 wines (sold by volume) in the U.S. “The only thing holding back a total conversion to synthetic enclosures is consumer perception” (

While a natural cork allows a high quality wine to continue to mature, experts seem to agree that with a lower-cost wine that will be consumed within 3-6 months of purchase, the type of closure makes little difference. For a relatively low-budget wine consumer like me, screw caps are probably fine—and they are more acceptable on white than on red wines. But when I want a premium bottle of wine for a special occasion, I should look for a cork—if I can even figure out what is under that metal “capsule” that wraps the top of the bottle! As a hard core traditionalist, I found this research both eye-opening and disappointing. I admit it—I still don’t like screw caps. But with new technologies taking over, apparently I will need to spend a pretty penny to find a true, unadulterated cork closing my bottle of wine.

Want to know more about these and other issues related to wine? Hodson, who is credentialed by the nonprofit Wine and Spirits Education Trust (WSET), will be teaching a Level II wine class at PVCC on Monday evenings from 6 to 9 p.m. beginning Sept. 11 (as part of the Workforce Services Viticulture & Enology series). Level I will also be offered all day on Saturday Oct. 7, but is not a prerequisite. Cheers!


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