CORK
Cork is an impermeable buoyant material, the phellem layer of bark tissue that is harvested for commercial use primarily from Quercus suber (the cork oak), which is endemic to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance. Because of its impermeable, buoyant, elastic, and fire retardant properties, it is used in a variety of products, the most common of which is wine stoppers. The montado landscape of Portugal produces approximately half of cork harvested annually worldwide, with Corticeira Amorim being the leading company in the industry. Cork was examined microscopically by Robert Hooke, which led to his discovery and naming of the cell
USE IN WINE BOTTLING
As late as the mid-17th century, French vintners did not use cork stoppers, using instead oil-soaked rags stuffed into the necks of bottles.
Wine corks can be made of either a single piece of cork, or composed of particles, as in champagne corks; corks made of granular particles are called "agglomerated corks".
Natural cork closures are used for about 80% of the 20 billion bottles of wine produced each year. After a decline in use as wine-stoppers due to the increase in the use of synthetic alternatives, cork wine-stoppers are making a comeback and currently represent approximately 60% of wine-stoppers in 2016.
Because of the cellular structure of cork, it is easily compressed upon insertion into a bottle and will expand to form a tight seal. The interior diameter of the neck of glass bottles tends to be inconsistent, making this ability to seal through variable contraction and expansion an important attribute. However, unavoidable natural flaws, channels, and cracks in the bark make the cork itself highly inconsistent. In a 2005 closure study, 45% of corks showed gas leakage during pressure testing both from the sides of the cork as well as through the cork body itself.
Since the mid-1990s, a number of wine brands have switched to alternative wine closures such as plastic stoppers, screw caps, or other closures. During 1972 more than half of the Australian bottled wine went bad due to corking. A great deal of anger and suspicion was directed at Portuguese and Spanish cork suppliers who were suspected of deliberately supplying bad cork to non-EEC wine makers to help prevent cheap imports. Cheaper wine makers developed the aluminium "Stelvin" cap with a polypropylene stopper wad. More expensive wines and carbonated varieties continued to use cork, although much closer attention was paid to the quality. Even so, some high premium makers prefer the Stelvin as it is a guarantee that the wine will be good even after many decades of ageing. Some consumers may have conceptions about screw caps being representative of lower quality wines, due to their cheaper price; however, in Australia, for example, much of the non-sparkling wine production now uses these Stelvin caps as a cork alternative, although some have recently switched back to cork citing issues using screw caps. These alternatives to cork have both advantages and disadvantages. For example, screw tops are generally considered to offer a trichloroanisole (TCA) free seal, but they also reduce the oxygen transfer rate between the bottle and the atmosphere to almost zero, which can lead to a reduction in the quality of the wine.[citation needed] TCA is the main documented cause of cork taint in wine. However, some in the wine industry say natural cork stoppers are important because they allow oxygen to interact with wine for proper aging, and are best suited for wines purchased with the intent to age. Stoppers which resemble natural cork very closely can be made by isolating the suberin component of the cork from the undesirable lignin, mixing it with the same substance used for contact lenses and an adhesive, and molding it into a standardized product, free of TCA or other undesirable substances. Composite corks with real cork veneers are used in cheaper wines.
The study "Analysis of the life cycle of Cork, Aluminum and Plastic Wine Closures," conducted by PricewaterhouseCoopers and commissioned by a major cork manufacturer, Amorim, concluded that cork is the most environmentally responsible stopper, in a one-year life cycle analysis comparison with plastic stoppers and aluminum screw caps
TYPES OF WINE CORK
A wide variety of types of wine corks and bottle stoppers exist to preserve wine. Some winemakers — especially those who mass produce value wines — are using metal twist off caps instead of corks. While cork type (or lack there of) in some ways affects wine flavor over time, as well as our perception of taste, it’s also critical in protecting wines as they age. Some corks are more reliable than others.
Natural Wine Corks
“Natural Cork” is an umbrella term for different grades and styles of cork made from natural cork tree bark. These corks are 100% natural, and can either be one-piece cut from one sheet of cork bark, multi-piece, where at least two pieces of cork are glued together, or colmated, where the tiny holes within a natural cork are filled in with cork dust and glue.
One Piece natural corks are ideal for the aging of wine long-term. They very naturally expand and remain strong over long periods of time. When removed from a bottle of wine, a one-piece natural cork will expand to 85% of its original size almost instantly, while regaining the rest of its original composure within the next 24 hour period.
Multi-Piece corks work well with wines that don”t need to be aged for long periods. These corks are often made with cork bark “scraps,” cut from cork bark areas that weren”t very thick to begin with.
Colmated corks are the middle ground for aging. Because a large portion of the tiny holes in the cork have been filled in, only small amounts of air are able to reach the wine. These corks are typically used for wines that shouldn’t be aged for more than 3 years.
Agglomerated Wine Corks
Agglomerated “Twin Top” Wine Corks with Natural Cork Ends
Also designated the “double disc,” these corks are a type of technical cork and are made up of two natural cork discs on either end, with the ”meat” or middle of the cork being completely agglomerated. These vary in quality, and are ideal for storing wines that require medium aging, since only small amounts of air can reach the wine.
Synthetic Wine Corks
Synthetic wine corks have only begun to be used on a large scale within the wine industry. They are most commonly made from oil based plastic, while certain synthetic cork manufacturers are also experimenting with utilizing plant based polymers from corn and sugar cane.
Synthetic corks can be advantageous to wine makers looking to achieve a scientific degree of oxygen transfer. Since these materials can be crafted are various densities and from various materials, they can have set air transfer rates. At this point in time, it seems there are more positives than there are negatives to synthetic corks.
Positives
Synthetic corks will last for long periods of time. Because the material used to make synthetic cork is not natural, wines will never be at risk of attaining cork taint.
Wine can be stored standing up, as opposed to being laid down, since they don’t require the moisture from the wine to keep up cork integrity.
Fixed and predictable oxygen transfer rates
Tight seal, anti-bacterial
Negatives
Since most synthetic cork material is comprised of petroleum based plastic, some argue that it adds a chemical odor and or flavor to the wine being stored.
Last but not least – it”s not a wine cork but it serves a similar function…
Metal Twist Off Screw Caps
Twist off wine screw caps are being utilized more in New World wine regions, rather than old, where tradition is less of an issue. These corks, for the most part achieve the purpose of storing a wine for medium to long term aging, as well as up-right. The biggest advantage of using a screw cap over a natural cork is that there is NO risk of cork taint over time.s
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