Screw caps for wine bottles have been around for almost 70 years, but in many ways they are still a controversial closure. Screw caps are often associated with low-end wines that are not meant for aging, and seeing a high-end restaurant present an expensive, aged bottle with a screw cap can be shocking, particularly for U.S. consumers.
“There is a shock factor in approaching a table in a dining room like The Modern with a bottle with a screw cap,” explains Isabel Kardon, a sommelier at the two-Michelin-starred restaurant in New York City. “I think that it often rubs guests of a certain age range the wrong way.” That’s likely due to the limited presence of screw caps in the U.S. market over the last several decades. In a 2021 survey of North American wineries, 70 percent of respondents said that cork was the preferred closure type.
But these assumptions about screw caps and wine quality are just that—assumptions. In the 66 years since Stelvin (then known as Stelcap-Vin) first introduced screw caps for wine bottles, a lot has changed, and a lot more is known about how a wine is impacted when bottled under a screw cap versus a cork—both in the short term, and now, the long term.
This greater understanding of screw caps and their impact on wine is perhaps one reason that the tide is turning for screw caps in the U.S. In the same 2021 survey, screw cap usage by wineries jumped to 52 percent of respondents, up from an average of 30 to 40 percent over the past decade.
“[When] you taste the quality of what’s in the bottle, you start to understand that screw caps aren’t an indicator of quality,” adds Kardon. Indeed, just as with corks, a screw cap says little about the quality of the wine inside the bottle. But screw caps differ from corks in important ways, which has implications for how a wine ages.
With that in mind, SevenFifty Daily spoke with producers and researchers around the world to understand the science behind aging a wine under a screw cap, and what it means for the liquid when it eventually hits your glass five, 10, or even 25 years after bottling.
Corks and the oxygen transmission rate
It’s impossible to talk about screw caps without first talking about corks. Corks have been used to seal wine bottles for centuries, so our understanding of how a wine should age over a given time period is based on how it develops under cork. While some might argue that cork is not the best way to seal and age a wine, it is undeniably the standard against which we judge all other methods.
When most people judge the quality of a wine aged under something other than a cork, what they’re asking is, “does it taste like a wine that has been in a glass bottle with a cork for that period of time,” says Andrew Waterhouse, Ph.D, a professor of wine chemistry at UC Davis.
At the center of this question is a measurement known as the oxygen transmission rate (OTR), or how much oxygen passes through a material over a given period of time. It’s an important measurement because oxygen can improve or deteriorate a wine depending on the timing and amount of exposure. During aging, for example, micro-oxygenation can help stabilize color and soften tannins.
“The key performance criteria for any closure is how much oxygen goes through it,” confirms Dr. Waterhouse. “For natural cork—although natural corks are highly variable—on average about one milligram of oxygen goes through the cork [per year] when it’s new. What you see in the market is a lot of other closures trying to mimic that performance.”
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