If you’re a lover of wine, then you know that there’s an age-long connection between wine, wine bottles, and corks. But why is cork used in sealing wine bottles? Is it responsible for some extra features or just an old tradition?
Corks are useful because they ensure that wines can experience a desirable level of oxidation during it’s aging process. Corks are designed to let in little amounts of oxygen to allow for the oxidation of your favorite wine. When wine is stored under anaerobic conditions, it would develop undesirable aromas that reduce the overall appeal of the entire bottle. Hence, the importance of using corks.
Most food and food products are actually at their best when fresh. There’s a special delight in plucking fruit and eating it on the spot. It would taste so juicy and would fill your mouth with bursts of flavor. What a great taste! However, an exception to this rule about freshness occurs when dealing with wines. Because many wines need to age for some time to give their best taste. Winemakers are aware of this fact and it’s their job to make sure that they control the aging process for each bottle. An essential part of this process is how they make their wine bottles.
What’s the importance of aging to a bottle of wine? Aging influences the interaction between fruity acids and alcohol. To put it simply, aging helps reduce the sourness and give you the best taste of wine. However, it extends more than that. Oxidation is a vital part of the aging process for wine. When oxygen interacts with the wine, it leads to several desirable changes. Usually, it creates a wine that has a nutty aroma. This is the reason for the great taste in many of the Sherry styles we’re used to.
You may have heard the saying, the older the wine the better it tastes. The oxidation is responsible for providing different benefits until anyone isn’t ready to drink the bottle of wine. Storing wine in anaerobic conditions can easily cause it to have an undesirable aroma. No one would enjoy drinking something like that. Little amounts of oxygen will break down the thiol compounds that usually have the smell of burnt rubber or rotten egg. The reaction of oxygen with red anthocyanin molecules found in grapes will also cause a stable pigmentation in red wine. The way a winemaker decides to seal a bottle directly affects how much oxygen can get to the wine in it. This will affect its aging and determine the best time to gulp down the contents of the bottle. This is where the corks come in.
Glass is a hermetic material which means that it does not allow the penetration of oxygen between its molecules. Therefore, anything stores in a glass bottle are going to be airtight if the top of the bottle is also sealed. Corks are designed to allow trace amounts of oxygen to pass through them. Usually, a cork allows one milligram of oxygen to pass into the bottle every year. This may sound like a little quantity but after some years, it will kickstart the oxidation process. Most times, the initial two or three years will allow enough oxygen to break down the sulfites that are preventing oxidation.
Basically, there are three types of corks namely; natural cork, screw caps, and synthetic corks. Natural corks have been in existence for about 250 years and were introduced to replace oiled rags and wooden plugs which were formerly used in sealing wine bottles. This made it easier to enjoy the concept of aging wine. Natural corks had been the only reliable option to deal with bottles until about 20 years ago. These corks are gotten from the bark of the tree and are harvested every seven years in the lifecycle of a cork oak tree. To harvest, a cork cylinder is cut from the outside to the inside of the tree’s bark.
Recently, a small fraction of corks (about 1 – 2%) ends up tainting the quality of the wine. They usually end up adding a moldy, smelly substance referred to as trichloroanisole (TCA). TCA is usually formed from a variety of chemical reactions that occur in the sealed wine bottle. Its aroma is quite potent and only a little quantity in the wine would give a smell of wet cardboard or affect the taste of the wine. Usually, in every eight cases of wine, there are one or two bottles tainted with TCA. This is why restaurants allow for a wine tasting before serving it to you – to let you determine if it’s tainted or not.
Recently, synthetic corks have become another option for winemakers. These corks are made from polyethylene which is also used in the manufacture of milk bottles or plastic pipes. These man-made corks perform the same function as their natural counterparts but only with three major differences; they don’t taint the wine, they let in a consistent stream of oxygen and give room for more oxygen passage. The consistent stream of oxygen which they offer is their best feature and a reason why a lot of winemakers are opting for them.
Synthetic corks make it easier to determine how a bottle of wine will taste after a particular period. Another great thing is that winemakers can make use of different synthetic corks to provide variable oxidation rates to their wine bottles.
A screwcap is divided into two parts: the metal cap and the liner inside the top of the cap that seals the bottle. The liner is the most important part of the screwcap because it controls the amount of oxygen that passes through. Some years back, screw caps had only two types of limers. Today, there have been numerous changes to the liner mechanism and the material it’s composed of. There are now liners that offer a variable amount of oxygen transmission to suit different winemaking purposes. Standard liners are designed to admit a bit more or lesser than natural corks. The stream of oxygen passage in most liners is also consistent.