Natural Cork Closures for Wine

Natural Cork Closures for Wine

Natural cork wine have been used to seal and protect wine for the past three hundred years or so. Prior to that more crude methods were employed. Today we are seeing a thriving synthetic closure market crop up and the debate between whether to use natural or synthetic closures is thriving. This article is the first in a serries that will cover each of the different closure types available and what their benefits and drawbacks are. Where Does Cork Come From? Cork closures are made from the bark of the Cork Oak tree. This particular tree is native to Southwest Europe and Northwest Africa. As you can see from the cross section of a cork oak tree the bark grows very thick. Once it has reached an optimum thickness the bark is harvested by stripping it from the tree in large sheets. These sheets are processed and solid corks are drilled from it. The remaining cork is then shredded into small particles and used to create more cork closures or it will go into other cork products such as corkboards for displaying all those reminders we never look at. Unlike other trees the cork oak does not suffer from the removal of its bark. It simply regrows and can be harvested again and again as it reaches the proper thickness. On average it takes between nine and twelve years for the tree to regenerate its bark. The bark is usually harvested from cork oaks that are at least 25 years old. These trees can live to be between 150 to 250 years old even when the bark is harvested on a regular basis. So each tree goes through about twelve harvests in its lifetime. The Benefits of Natural Cork Closures Natural cork closures have been used for so long because there are many benefits to doing so. Previous methods for sealing wine bottles included soaking rags in oil and stuffing them into the neck of the bottle, while other cultures would pour a layer of olive oil over the free surface of the wine. The floating oil would prevent oxidation and microbial spoilage so long as the wine was not infected prior to pouring the oil. One of the main benefits of cork closures is that they are a product of nature. Many synthetic closures are made from petroleum based plastics that, some critics claim, leave petrol flavors behind. By in large natural corks do not impart any noticeable flavor on the wine. Due to the long history of using cork closures we have a much better understanding of how they hold up over time and how well the wine they protect develops. No one knows how well a synthetic closure and the wine it protects will fair after fifty years in the cellar because they just haven’t been around that long. The Drawbacks of Natural Cork Closures There are a few downsides to using cork closures. Because they are derived from a tree they, like any other plant based material, can dry out over time. So care must be taken when purchasing, inserting, and storing wine enclosed with...

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Cork Closures and Oxygenation

Cork Closures and Oxygenation

Natural cork closures have been around for hundreds of years. At first they were merely a more convenient way to seal a bottle of wine. Over time, however, we have come to understand that corks offer an incredible benefit over synthetic closures: micro-oxygenation. That’s right, natural corks allow your wine to get oxidized. While this may seem scary at first it is actually very good for wine in very small doses spread out over very long periods of time. The Key Feature of a Cork Closure Natural corks have pores that wine is able to seep into. This is what causes a cork to swell up and provide a tighter seal against the glass neck of the bottle. Oxygen too is able to penetrate these pores. Thus there is an interface for oxygen and wine to interact. Take a look at the picture on the right. You can see that the Shiraz I made almost a year ago has seeped about a third of way through to the outside world. After that the cork looks pretty much like it did the day I inserted it. It is where the red stops that my wine and oxygen from outside of the bottle are allowed to interact. The rest of the cork pores are full of oxygen. The wine has not seeped uniformly through the cork but it is making its way toward the end. It took nearly a year for the wine to get that far through the cork. In another year it may very well be approaching the end of the cork. As wine makers we try very hard to limit the exposure of our wine to oxygen. After all an oxidized wine turns colors and can pick up off flavors. However, in order for a wine to age properly it does need a very small amount of oxygen. Because the wine and oxygen are only permitted to interact within the very small pores the surface area of the wine is actually very small. This is why red wines are able to be stored for years or even decades and still improve. Storing Wine On Its Side In this second picture you can see how wine affects the swelling of the cork. I’ve just removed this cork from the bottle and the red portion of the cork where the wine has seeped in is a bit larger in diameter than the dry end where the cork screw entered the cork. By storing my wine on its side this cork was kept swollen for a tight seal. It also allowed for some interaction between the wine and oxygen. This is why I prefer natural corks and why wines that are aged any length of time in the bottle will have natural cork closures. There are some synthetic closures that allow for micro-oxygenation but in my opinion there’s no replacement for a natural cork. If you do not store a wine on its side the cork may dry out over time causing it to shrink. As it shrinks the amount of oxygen that is able to pass into your wine increases. Sometimes the...

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Bottling Wine

Bottling is the final step in the wine making process that requires any  effort on your part. After this time takes care of the rest. The major considerations when bottling are what kind of bottle to use, type of closure, and to add gas or not. Bottles The type of bottle you use is completely up to you. A bottle’s shape does not impact the taste or life of your wine in any way. Typically red wines are bottled in dark green bottles to prevent UV exposure which can accelerate the aging process. If you keep your red wines in a dark “cellar” like environment light will not be an issue and you can use whatever color strikes you as awesome. White wines are typically contained in clear bottles as they are not aged nearly as long as red wines are for the most part. More on this in the bottle aging step. Closures A closure is a fancy term for whatever you use to seal your bottles. Most wineries us a cork, synthetic cork, or screw cap. There has been a raging debate arguing the ups and downs of each type of closure. We’ll briefly touch on them here. Natural Cork Being both natural and the historical closure of choice natural cork is a good choice. A benefit to natural cork is its ability to let in tiny amounts of oxygen. The small amount of oxygen allows for “micro-oxygenation”, an essential part of long term bottle aging. Natural corks have a few drawbacks worth mentioning however. Poorly made corks can deteriorate and leave your wine “corked” (tasting like moldy cork). Even the highest quality cork producers wind up making a few duds. Once a wine is corked there’s nothing you can do about it. Another draw back is corks that leak. Some corks have a little channel that on the side of the cork that allows wine to leak out. You can’t always see these defects in a cork prior to bottling so it’s a risk you must take to use cork. Synthetic Cork Today’s synthetic corks are getting much more sophisticated than the old petroleum based ones you used to see in the 90’s. Synthetic corks don’t deteriorate, nor do they have a tendency to leak. Many synthetic corks do not allow for micro-oxygenation. They seal very well. This is fine for a wine you intend to consume within three years or so. Any longer and you’ll want natural cork. Some synthetic corks are designed to allow for micro-oxygenation but they haven’t been in use long enough to say for sure how they compare to natural cork. Screw Caps The latest closure on the scene is the screw cap. Largely thought to be a sign of cheap wine these closures are starting to take hold even in more expensive wineries. Proponents of screw caps site the lack of spoiled wine due to bad corks among their chief benefits. Screw caps also aren’t likely to let loose if checked in airline baggage as a cork can. On the other hand screw caps don’t allow for micro-oxygenation as a...

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