It's a hot-button issue among wine lovers: Should you purchase wine that's sealed with a cork or a screw cap? Before we get into the pros and cons of each, it's important to understand the history behind the former, plus why the latter has become such a popular alternative.
Since the 1400s, cork was the best way to seal a bottle.
Cork became the traditional wine bottle closure in the 15th century because it was the only available substance that was malleable enough to effectively close a glass bottle soundly. Wine corks are made from the bark of the cork oak tree, which can be peeled away without actually harming the tree itself. Cork is a renewable resource, but it does take the tree eight to nine years to produce bark that can be harvested again. A cork oak tree doesn't start producing the level of quality needed for a wine cork until it's about 43 years old, and trees can be harvested until they're 150 years old. Wine bottle closures are the main use of natural cork today, and they can be repurposed into everything from shoes to yoga blocks to craft projects.
For 500 years, cork had no competition when it came to sealing a bottle of wine. Not only was cork the best way to keeping bottles from leaking, but natural corks allow a little bit of oxygen into the bottle which can help the wine age and evolve. Exactly how much and how quickly oxygen permeates a cork is referred to as OTR (Oxygen Transmission Rate).
In 1964, we saw the advent of the screw cap.
There's a big misconception that screw caps were invented simply because they are cheaper, and therefore the wines that use them are of cheaper quality. The real reason screw caps (also called Stelvin caps) came into popularity is because natural corks that hadn't been properly sanitized started picking up a chemical called TCA (an abbreviation for the compound 2,4,6-trichloroanisole). Corks contaminated by TCA give a musty smell and flavors of moldy cardboard to the wine... so when sommeliers say a wine is 'corked', they are talking about the presence of TCA (TCA it's not harmful if consumed, but it's not pleasant to drink). Screw caps were a great alternative for wineries that wanted to avoid the risk of TCA in their wines.
Screw caps didn't become popular with wineries until the 1990s. At that time natural cork quality was declining and winemakers were tired of having their hard work in the vineyard and winery ruined by shoddy corks. Screw caps eliminated these issues—and today 4.5 billion bottles a year use screw caps, according to trade publication The Drinks Business.
Which is better for the wine?
The answer isn't so simple. The common argument is that while screwcaps preserve the integrity of the wine inside the bottle more consistently, wines with corks allow for better aging. However, technology is advancing every day on both sides. Screw caps are now being engineered to be "breathable" and they offer four different oxygen transmission rates, so winemakers have more options if they decide to use one. Technology has been developed to detect TCA in corks, so it's getting faster and more affordable for wineries to test the cork for bacteria before they use them for bottling.
There are several studies currently underway to determine the ageability of screw caps, but since the technology is so new it's a little too soon to tell whether corks or screw caps are better long-term. However, the overwhelming majority of wines at your local shop are intended to be consumed within one to five years. Unless you're starting a wine collection and investing a good amount of money in building a cellar, the aging potential of a wine won't really be a factor in deciding which bottle to open this weekend.
Which is better for the planet?
There are environmental benefits to both corks and screw caps. Cork forests improve soil's organic matter, are great barriers for fires and desertification, and are home to over 200 species of wildlife (the cork forests of Portugal are a UNESCO World Heritage Site, for their beauty and biodiversity). Plus, each natural cork stopper retains 112 grams of CO2: that's equivalent to the annual energy savings from 17 solar panels per 1,000 cases of wine. The cork industry is powered by the wine industry, so purchasing wines bottled with cork is an eco-friendly choice. Screw caps, however, are much lighter to ship so the carbon footprint is greatly reduced; the small amount of aluminum used makes very little environmental impact and is 100% recyclable. What you should stay away from are plastic or synthetic corks: they provide no environmental benefits and are by far the least effective kind of seal for a bottle of wine.
Which is best for you?
Weighing all of the quality, taste, and environmental factors, it probably comes down to something as simple as the actual usage: Do you prefer the ceremony of pulling the cork, or the convenience of cracking a twist-off cap? They both have a place in the landscape of wine today. After all, the beauty of innovation is that there's still a place for tradition. Just as e-readers and tablets haven't totally replaced books and magazines, MP3s haven't replaced vinyl, and credit cards haven't made cash obsolete—screw caps are just another option. With such a wide array of wine packaging solutions (even premium box and can wine), there's no better time to be a wine lover than right now.