From Content to Cover. Corks and Bottles.

I have talked a lot about the content of wine bottles and will talk even more, but now let’s pay attention to the cover of the content, to the vessel, where ready-made wine awaits its admirer, since the content could be safely conveyed only with the cover that is close to ideal.

Let’s talk about a vessel filled with divine nectar.

The times of amphorae, pipes and wineskins had long been sunk into oblivion; modern visualization of wine shows primarily the image of a glass bottle, closed with a cork.

Nowadays, most of world’s wines are packaged in glass bottles. Glass is a perfect material for wine. It is inert, completely air-tight, cheap and esthetic. The main disadvantages are heavy weight and rigidity that increase the cost of transportation and its storage. Also, it is breakable.

Another disadvantage of a glass bottle is the difficulty of storing wine after the bottle was opened. To preserve wine from quick oxidation the half-empty bottle should be vacuumed or filled with inert gas. Of course, there is always an option to finish the contents of a bottle at onceJ

Nowadays, you can find wine in plastic bottle bags. They are lighter and not as easily breakable. Bag-in-box packs have one advantage: they collapse as wine has been consumed, that prevents air access to wine. Unfortunately, plastic is the material that’s not as inert as glass, hence, unwanted chemicals diffuse into wine slower but steadier. Also, plastic is slightly permeable to air and wine will degrade over a period of months. You don’t store wine in plastic, it is only appropriate for quick consumption.

Thus, as of now there is no real alternative to glass bottles.

The situation with bottle closures is different.

Cork remains a never-dying classic.

Even though corks look very natural in glass bottles, they were not always together. Frenchmen started using cork as bottle closure only in the XVII century. Before that, bottles were closed with oil-soaked rags. Cork innovation is very often attributed to Dom Perignon – the famous icon of winemakery. As a matter of fact, it is a myth as many others. Although, Dom Perignon gave to winemakery a lot, the cork closure doesn’t belong to his list. The name of an actual innovator still remains unknown.

Corks are made from a bark of cork oak – Quercus suber. The oak is native for southwest Europe and northwest Africa. Nowadays, oaks for cork production are mainly growing in Portugal and Spain. Once the tree becomes 25 years old, its cork layer becomes thick enough for harvesting. The bark is gently striped from trunks. The cork of the first harvest has poor quality. It is too rough and easily minced. It is not good for cork closures and is being used for different products of cork crumbs (flooring, shoe soles and so on). After the first harvest, the tree regrows new bark for nine years. The cork from the second harvest is good for cork closure. Every nine years an oak loses its bark and regrows a new one. Since cork oaks live for about 300 years, every tree can produce a huge amount of cork closures.

Why is cork so good for our purpose? It is light and elastic. A cork can be easily compressed and settled into a bottleneck, where it decompresses and fills all the space. The cork keeps its properties only when it is wet. Before the production, the bark is boiled to provide elasticity and then cut into corks. In the bottleneck the cork closure also should remain wet. When it dries out, it starts to crack and crumble, and you can say good bye to your wine.

If you keep a bottle of wine under the cork closure – keep it horizontally! so wine could wet the cork. It is not critical, if time counts in days or weeks, but several months (not to say years) can be critical.

Agglomerate cork closure is a cheaper version of cork closure. It’s not cut from the whole piece of cork, but is pressed from cork chips. The quality of agglomerate cork is lower than of normal ones, it dries quicker and cracks and crumbles easier. It is cheaper and often used for non-expensive wines.

What are the disadvantages of cork closure, except that you should have a corkscrew to open a bottle? The main problem is a cork taint. The source of this trouble is trichloroanisole (TCA), the substance that is produced by a mold after a treatment with chlorophenol compounds. Chlorophenoles are used for wood treatment as antifungal agents. If mold appeared on a treated wood, then TCA would be synthesized. If TCA from cork closure or through cork closure falls into wine, the wine gets the aroma of a wet cardboard. It is definitely not the right aroma for wine. Formerly, cork taint used to be a critical problem, now the wood treatment has significantly improved, and cork taint affects only 5% of bottles around the world.

Agglomerated cork closure becomes a source of cork taint more often than regular cork closures.

Nevertheless, even 5% of wastage seemed too much for winemakers, so they started to look for alteration in cork closure.

The most direct alteration is synthetic closure. It is cheap and easy to make, but is only usable for wines that would be stored no longer than a year. Synthetic closure poorly adjoins to a bottleneck and gives a good passageway to air, accordingly wine quickly oxidize. Additionally, plastic effuse inappropriate substances to wine.

Another alteration is a screw cup made from aluminum. It perfectly protects wine from air oxidation and doesn’t pollute wine with its compounds. Again, it is easily opened and closed. Screw cup is quite popular, especially in Australia and New Zealand, where it had practically replaced the cork closure.

In fact, screw cap is ideal for wines whose dominant flavor has fruity notes, in other words for a wine that wouldn’t age in a bottle.

But if a wine is made in such a way that its mature peak appears not in the first year after bottling but requires agening, the screw cap doesn’t work appropriately because of its complete air-tightness. Process of wine maturation requires some oxidation. An excess of oxygen will kill the wine, but a tiny amount still is necessary. Cork closure provides such a dosed amount.

Actually, wine maturation, from biochemical point of view, and the role of closure process are grey zones in winemakery. Much of it still remains unclear and requires further studying. Again, many things can be confirmed only empirically. However, the screw cap was used long enough to realize that it interferes with wine ageing. Australian winemakers, who had almost completely rejected cork closure, now return to its use for fine wines that require ageing. At present time, novelty screw caps, which allow some air flow, are being developed, but their effectiveness can be confirmed only some decades later. Ageing requires time, and result requires it too.

Finally, about glass closure Vin-lok or Vino-seal. Its properties are similar to screw cap’s, and it looks more esthetic, though, the price is a little higher.

The holy wars around the quality of wine closures go full speed at this time, but cork closure is still dominating around the world.

And as a bonus to this wine closure story – the truth about corks for sparkling wines. Why do they look like a young porcini? No, from birth they didn’t have such a shape. Unused cork for sparkling wine looks exactly the same as a regular cork, just a little longer. So, what happened? A cork was slightly pressed, stuffed into a bottle neck, and protected with wires. Remember that the pressure in a champagne bottle is about 5 atm, and all these atmospheres are trying to push the cork out of the bottle, but the wires prevent its outburst. In a such complicated situation cork exists at least half a year. Since cork is slightly elastic by its nature, it moves a little bit out under the pressure and fills the remaining space under the wire, thus forming a mushroom cap. When a wine lover opens up a bottle and releases all the pressure, the part of the cork that was compressed in the bottle neck relaxes and takes a form of a stipe. Couple minutes after opening the bottle we get a little porcini.

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