Cork has not long been available as a method for keeping oxygen and other unwanteds out of wine. Not long in the larger and longer history of wine, anyway. One of the many ways that we once preserved the life of our favorite ferment was by adding salt or salt water. Take a moment to imagine that flavor as we dive into – and develop a deeper appreciation for – the various options we have today for sealing bottles. Even though each winemaker makes this choice without consulting your preferences, it’s fun to understand how each can affect your experience – and the wine over time.
Natural Cork “The OG”
It is very possible that we owe the entire fine wine industry to the use of natural cork, which began on a large scale in the 1700’s. It’s structure helps keep a nearly air-tight seal, allowing tiny bits of oxygen into the bottle over time. This “micro-oxygenation” is what allows wine to develop notes of age or tertiary aromas. These can include leather, nuttiness and tobacco (and so many others!) and have come to be the identifying marks of great aged wine. As a quality measure for juice that is intended for decades of aging, producers may choose to use longer corks in order to control that precious balance of oxygen influence and aroma development. It can be said with confidence that if we had not discovered the complexities that these tertiary aromas lend to the experience of imbibing, all wine would likely be table wine.
A fairly magical product, natural corks are punch-cut out of the bark of the cork oak tree (Quercus suber) which will regrow and can be stripped again in about nine years. Once cut out, they go through a series of sanitizing,bleaching and curing processes before being thrust into a bottle. But, even after all that, they are not without a score of problems. As a natural resource, they can be expensive and environmentally detrimental to harvest, and they can lead to financial loss at every level of distribution. Today, around 70% of winemakers choose to hold on to the pomp and ritual of cork, albeit increased expense and risk.
Natural cork has one very serious drawback that most wine drinkers are all too familiar with. If you’ve ever heard of a wine being “corked” or, more accurately, having “cork-taint,” you may already understand the benefits of using synthetic or alternative materials. In the 80’s we discovered that anywhere from 5-8% of bottles sealed with natural cork carried the microbe TCA (trichloroanisole). Though cork is naturally antimicrobial, TCA is a byproduct of fungi that are present on the cork tree. Not only does it make every wine that it infects smell of moldy basement and wet cardboard to some degree, it also robs the wine of some (or all) of its fruity flavors.
Another, decidedly less tragic, issue with natural corks is that all bottles sealed this way must be stored on their side for their entire life. In order to remain “air-tight,” the corks must be swollen with liquid. If they are stored upright for long enough for the cork to dry, it will lose its seal and allow oxygen to freely enter. Unfortunately, you often cannot be sure until you open the bottle that it has indeed been stored properly. One of the reasons a server hands you a cork upon opening a bottle in a restaurant is so that you may inspect it for proper swell.
Thank Bacchus – alternatives exist!
Agglomerate Cork “The Frankencork”
Agglomerate or composite corks are made from natural cork that has been uber processed – ground up, chemically cleaned and reformed into the shape of a cork. This usually solves the TCA problem (but not always) and is less expensive overall as imperfections in the bark will not show in the final product. In fact, they were originally invented to utilize the waste after high-quality corks were cut out of the bark, not for cleanliness sake. A downside: as with most of the synthetic options below, these are not biodegradable as they use synthetic polymers to bind the ground-up bits of cork.
Synthentic “The Cool Kid”
Synthetic corks are the last of our options that mandate tools and tableside awkwardness ceremony. They are made with petrochemicals and are absolutely not biodegradable. These are cheap to make and easy to customize. Unfortunately, drawbacks keep them out of the running for ageable wines. They can “rob” wine of flavor by binding to some of the more delicate components that later would contribute to complexity. With synthetic corks, you should probably not worry too much about “later” though. They tend to allow too much oxygen in, aging the wine faster than other closure options. If you find a wine with this style, make sure its current vintage and meant to be drunk quickly. These are great for marketing and branding as they can be entirely customized with colors and logos.
Another option that is new-ish to the market is a “cork” made out of sugarcane polymers. Totally recyclable and biodegradable, these are a great option for wineries like Agricole Basile, (who just introduced their new vintage of Vermentino with sugarcane) that are conscious of their environmental impact and carbon footprint. The effects of age with sugarcane corks are still unknown.
Stelvin Closure A less stigmatized way of calling it a screw cap
Stelvin is actually one of many brand names in this category, but as popular sentiment on the quality levels indicated by screw caps shifts, you’ll often hear Stelvin as a general term. Screw caps are predominantly utilized for wines that are meant to be drunk when they are young and fresh as they tend to keep a very tight seal. They are made of a recyclable metal (usually aluminum alloy) capsule and an inner portion called “wadding”. The wadding is usually made of a polyethylene foam and is responsible for creating the seal that keeps oxygen out. A part of the wadding, and the most influential component, is the film (called a liner) that goes between the foam and the bottle. The purpose of the film is to create a barrier between the synthetic parts of the cap that may lend their own flavors to the wine or interact with it chemically.
Depending on the material chosen (often tin, but alway inert), the seal may be intentionally less air-tight. This offers micro-ox options for a screw cap. Many high end wineries have been experimenting with long term aging in this fashion, which is one of the factors for changing opinions. The most convenient feature of a screw-capped wine is that it does not require a tool to open. This makes them ideal for picnics, hikes or beach days and for waiters who forget to bring their corkscrews to work. Helpful hint: if you ever struggle to open a screw cap – twist the neck of the capsule, breaking the seal before twisting the cap.
Glass Stopper “The Bouncer”
Glass stoppers let in, like, zero oxygen and are completely inert. This preserves freshness like nothing else which is why you’ll often see these used for delicate and aromatic whites. Winemakers choose this style when they want to present a wine to you in almost exactly the condition that it leaves the winery. These are expensive to produce, as they need to be inserted by hand, but offer an elegant alternative to screw caps. Pitfallss include the fact that it’s not always obvious that the cork is made of glass, which can make for a confusing first encounter, sometimes (at least once for me) resulting in a flying glass knob. Also, should you have leftovers (only once for me) the cork reseals completely, but can be less reliable without the capsule to keep it in place. Store open bottles standing up, and keep an eye on the one in your purse.
Champagne Closures “Pressure! Pressing down on me, pressing down on me….”
Sparkling wine requires a very specialized set of equipment – in production and in storage. Not only are the corks responsible for keeping out all the usual suspects (oxygen, debris and a whole host of microbes), they also have to keep the bubbles in. Which is a tremendous amount of pressure, literally – between 70 and 90 pounds per square inch! It wasn’t until glass technology evolved to be able to form very thick-bottomed (Queen again!) bottles that sparkling wines had the chance to evolve into what we know and love today.
As for the closures, generally you will see a fatter cork used, which creates a super tight seal and can hold up better against the pressure. Then, as an added protection, there is a wire “cage” fastened over the cork, which keeps everything in place during transport and (heaven forbid!) temperature changes. What you often don’t get to see is the temporary crown cap (made of metal, often seen on beer and soda bottles) which is used to seal the wine in the cellar phase, as we patiently wait for the secondary bottle fermentation to perform its enchantmentc. Once the wine is ready to go to market, the crown cap is replaced by the more expensive and traditional champagne cork and cage. Some modern bubbles are coming to market with this crown cap still on. It is not an indicator of low quality, but may allow for a better value as the winemakers can pass on the thrift to the consumer.
It’s a lot to consider; but, luckily your only job is to enjoy the final product. Whether you are popping a cork, cracking a seal or using a bottle opener – Cheers!
An Alaskan-New Yorker, Raven Adrian is an adult with a propensity to play. She is driven by all things that inspire laughter and curiosity which brings her very naturally to a career in wine and hospitality. She is a Certified Sommelier (CMS) and has spent 18 years knee-deep in the restaurant industry of NYC. Raven is a currently part of the sales team at Golden Ram Imports. You can follow her on instagram @grapenutter.