Vintners have been sealing their bottles with corks since at least the 16th century, when English innovators started using them to seal their newly invented hard-glass bottles. Cork was the cutting-edge technology of the time, quickly displacing the old method of storing wine in casks and urns, writes Rajiv Seth.

But now traditional corks as the preferred seal for wine bottles have come under attack mostly for the reason that they could allow the wine to become "corked". That is, the wine reacts with a substance called trichloroanisole. This substance is formed when the chlorine, which is used to sanitize the cork, reacts with a mold that grows in some cork. Trichloroanisole, or TCA, causes a musty odor, and a flat, moldy flavor, an estimated 5-10% of wines on merchant shelves are "corked".

This problems has been around for centuries, but it took on new prominence after a Swiss chemist in 1981 discovered it was caused by corks, specifically those infected with a naturally occurring chemical compound called trichloroanisole (TCA). Around that time, world wine consumption also began to boom, driving up the prices of corks. As a result of both, winemakers began looking for alternative methods to close their bottles.

Natural corks are also not always easy to remove from the bottle. With the old spiral corkscrew, you have to put it in the cork just right, and not screw it in too far. And even if you get the corkscrew into the cork just right, pieces of the cork do crumble into the wine.

That isn't to say that cork stoppers are bad. They do allow the wine to breathe a bit. Their porous nature allow oxygen in the bottle and other gases out. Some experts say that this is what allows wine to age. Others, however, claim that it is the compounds in the wine that allow aging. One of the other goods things about natural corks, is the satisfying "pop" as it comes out of the bottle. A screw cap can't compare with the drama and romance of popping a cork out of the neck of the bottle.

You may have also seen synthetic corks in some bottles of wine. These stoppers, instead of being made from natural cork bark, are made from plastic. Synthetic corks are even harder to get out of the bottle than natural corks, and near impossible to put back into the bottle, if you need to put the bottle away after opening. Synthetic corks have also been known to allow the wine to oxidize, which causes flatness in the wine. It takes away some of the chemicals that form an important part of the wine aroma.

 Screw caps, on the other hand, seem to be the perfect solution for sealing a bottle of wine. Screw caps don't allow the wine to become "corked", like natural corks. They're easier to remove than both natural and synthetic corks. And they don't allow the wine to oxidize like synthetic corks. There is some argument about whether screw caps allow the wine to age, like a natural cork does. Since aging a bottle of wine may take 5-50 years, and the screw cap is a relatively recent development, it will take some time to determine whether or not the wine will age as well.

But for once, the old way of doing things turns out to be better for the environment. Cork is admirably renewable, recyclable, and biodegradable. It is made from the bark of cork oak trees, which is peeled off in huge strips about once every 17 years legally and then grows back. A typical cork oak can continue producing usable bark for up to 200 years.

The trees also help preserving the environmental aspects of the planet. Cork oak forests cover huge swaths of land in the Mediterranean countries of Spain, Algeria, Morocco, Italy, Tunisia, France and especially Portugal. They provide shelter to a range of plant and animal species, including endangered ones like the lynx, Barbary deer and the Imperial Iberian eagle, as well as jobs for more than 100,000 people. Almost 70 percent of their product is used to make the 15 billion bottle stoppers sold annually.

Synthetic corks and screw tops, by contrast, require a considerable amount of energy to manufacture- which equals carbon emissions and other pollution. They're also hard to recycle. All of which explains why environmental groups including the WWF and the Forest Stewardship Council are campaigning for cork.

In addition to their green appeal, corks have tradition on their side. Their centuries long association with wine and the elaborate ceremonies and paraphernalia that have developed around the act of uncorking have a powerful hold on many tipplers' minds. "You can't minimize the importance of that 'pop,'  "In many ways, that's the biggest hurdle for screw caps, along with its association with being cheap."

The cork industry is battling back, too. Major manufacturers have invested millions in recent years to screen their cork more carefully and upgrade their production processes to cut down on taint. As a result, the percentage of tainted bottles has dropped.

Amorim the leader in cork industry from Portugal is employing significant research and development practices and using the findings to improve its processing techniques. By offering the wine market a dramatically improved product, the company hopes to raise the cork industry standard at large, thereby forcing many of the 600 existing cork producers to follow suit. Though the industry maintains an 80-85% share in the wine closure market, producers that ignore the need for an improved product will most likely be swallowed up by consolidation among the larger companies such as Amorim, in a push for quality control across the industry.

New Innovative wine closures

Zork

Some new innovations are also making inroads in wine closure industry. One new closure teetering on commercial deployment is the Zork, developed by a group of South Australians. It aims to eliminate cork-related spoilage and seals with a foil membrane similar to that found in screw caps. It doesn’t require a special tool to open, as a plastic tap is wound off and the firm polyethylene stopper removed. There’s almost a popping sound to please diehard cork fans. It is replaceable to keep wine in the bottle and fits into standard glass bottles designed for conventional cork. Visually it looks a bit like a wine bottle stack hat.

Vino-Lock

Another new entrant in closure market of some particular interest will be Vino-Lock, a new "glass on glass" closure still in early trials, which uses a very thin synthetic coating on a glass topper that fits snugly in the bottle neck to provide a seal. It's actually quite attractive and has an aura of quality that is perhaps lacking in thin metal screw caps. However, this closure demands fine tolerances in the manufacturing process. I suspect that glass manufacturers won't like this, as it will shift the responsibility of closure integrity upon them. However, should this process eventuate, it will result in better bottle quality and provide a real bonus for the industry.

The Vino-Lok closure system fills a need in the wine industry, which has sought alternatives to natural cork that meets both the quality and aesthetic demands of connoisseurs."

The Vino-Lok closure looks like a decorative decanter stopper, and it is recyclable. Made with rubberized O-rings, the glass stopper provides a sterile seal, preventing contamination or oxidation. An aluminum cap over the bottle will ensure mechanical protection and temper evidence.

A one-year independent test recently conducted by scientists and wine experts from the prestigious Geisenheim Institute for Applied Enological Sciences and the Oppenheim/Rheinhessen State Teaching and Testing Institute indicates that Alcoa CSI's Vino-Lok closure system meets parameters for technical as well as taste performance compared to traditional wine closures.

Pro Cork

Another innovative wine closure offered by Australia and New Zealand, which is a recent development is offered by Vinpac International, Australia's largest bottling company, is the exclusive distributor of ProCork, a new wine closure that reduces oxidation and cork taint, using revolutionary technology that adapts to regular corks.

Developed by former CSIRO scientist, ProCork is a thin polymer membrane applied to each end of the cork to decrease the amount of taint entering the wine. The cork technology also controls the passage of oxygen through the cork and retains cork moisture to prevent breakage. "The five-layered membranes resemble contact lenses and have been proven to enhance the natural attributes of cork," informes Vinpac's marketing manager for wine solutions Lisa Roberts. Recent independent trials by the Australian Wine and Research Institute (AWRI) have found ProCork reduces oxidation experienced by a regular cork to levels that are comparable to a screwcap.

At last the future?

Cork is a wonderfully sustainable product with a low carbon footprint. The cork forests really are beautiful, and because wine stoppers are the most profitable use for cork, using cork this way sustains rural communities and helps preserve these ecosystems.

On the other hand Winemakers have a responsibility to source cork only from those companies that are serious about combating taint. A ROSA treated cork is advised to all wine makers.

It is largely because of the pressure put on cork companies by the success of alternative closures that these companies have started putting large investments on R&D to remove *** taint and this may prolong the use of cork as a leading source for wine closures.

Rajiv Seth

Rajiv Seth became the first Indian in the year 1987 to receive a gold medal from wine and spirit education trust, London. Presently he is making continues efforts in educating the lab assistants of a number of wineries on procedures of micro vilification through his manuals.