All about Wine Corks

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We have been producing wine for thousands of years and the techniques of wine production, viticulture, vinification and conservation have developed continuously over the centuries. This is also the case for wine sealing techniques, wine conservation and therefore corks.

The cork has a decisive role on the evolution of the wine and its taste and a cork can destroy the work of the winegrowers, that is why it is essential to choose it well.

Today we use mainly 5 different types of corks to ensure the watertightness of a bottle of wine.

the traditional stoppers in cork

The cork stopper is used very early in the history of wine, we already attest to its use by the Greeks and Romans for sealing amphorae even if the use of leather, wax or clay is more frequently developed. An amphora containing traces of wine, found in Ephesus and dating from the 1st century BC, is evidence of their use.

Amphorae were replaced by barrels at the end of the Roman Empire, due to their ease of transport, and cork for wine-making was abandoned from that time onwards.

It was in the 17th century that cork reappeared and became the most highly regarded sealing material thanks to the invention and standardisation of glass bottles.

The cork stopper is made from the bark of the cork oak which is dried for 6 months before being boiled in clean water in order to clean the bark and extract certain substances (tannins and mineral salts). We then proceed to cut the bark, the “tubing”, to obtain the cylindrical cork.

Advantages :

– The cork stopper has several advantages for wine conservation and many technical qualities. It is made of a light, waterproof, elastic and compressible material with technical insulating qualities.

– Cork prevents air from seeping into the bottle and coming into contact with the wine (at least almost entirely) and therefore prevents oxidation of the wine!

– But it does not lack air: it allows a tiny amount of oxygen to enter, which is useful because it allows certain undesirable aromas to be expelled while the wine matures: the wines develop complexity and the tannins soften. This small amount of oxygenation also eliminates the sulphites that were added during the bottling process in order to keep the wine fresh and avoid oxidation.

– It is the charm of traditional wines.

Disadvantages:

– It can give the wine a corky taste due to the possible infection by TCA.

– The world production of cork is too low to meet the needs of the wine industry for corks. This is one of the reasons why other techniques for closing wine bottles have been developed.

Agglomerated or sealed stoppers based on cork

This technique retains the charm of the cork tradition while reducing the risk of TCA infection (cork taint).

DIAM or agglomerated cork is made from cork particles glued together to form a cork.

Advantages:

– The DIAM avoids the problems of oxidation of wines as well as the pre-moulding of the cork. It is the authenticity of the cork without the cork taste!

– It preserves better the evaporation of the CO2 present in the bottle than traditional corks and thus it allows to limit the contribution of CO2 at the time of the bottling while guaranteeing a similar protection.

Disadvantages:

– Most frequently used for wines with a shelf life of less than 6 months as it does not provide the same qualities of conservation and ageing as a traditional cork.

Screw caps

The screw cap is made up of a metal base with a liner glued to the inside of the cap. This lining ensures the watertightness by sticking to the edge of the bottle neck when the cap is screwed on. It is particularly used in Australia.

Advantages :

– a practical advantage for the consumer as it allows easy unscrewing and re-screwing.

Disadvantages:

– There may be problems with the application of the cap during bottling and this causes a lack of seal and therefore risks of overexposure to CO2.

– A cultural disadvantage could occur specially in France, where people enjoy the sound of the poping cork and will not leave the using of traditional cork soon.

Glass stoppers

The glass stopper was very common before the 17th century but it was used with a cloth as a seal and this caused problems when opening the bottle as glass stoppers were not easy to remove and there was a risk of the bottle breaking. Moreover, it was an expensive product and difficult to produce because, like the bottles, they were blown by hand. Today, this type of stopper allows a perfect seal inside the bottle, which they seal thanks to a ring-shaped synthetic seal that is glued to the neck of the bottle.

Advantages :

– It preserves the freshness qualities of wines with a short ageing period.

– A luxurious connotation and its elegance.

Disadvantages:

– This type of cork allows too much airtightness and this is harmful for the wine (yes, you have to find the right balance between too little and too much air). It does not allow any exchange of oxygen in the wine and therefore does not allow a long ageing, it will be used for a wine of fast consumption.

– A very high production cost (3€ on average).

Synthetic stoppers

This type of cap was developed about 20 years ago. It is made from polymer resins, which is a petroleum derivative.

Advantages:

– Significantly less expensive than other corks.

– With this process, unlike wine bottles with corks, it is not necessary to keep the bottle lying down because the cork material is not subject to dehumidification.

– It can be made in different colours and this can be a plus for the product packaging.

Disadvantages:

– Lack of airtightness: it lets in too much air and can cause the wine to oxidise.

– Denaturation of the wine’s aromas: they can damage the wine by transmitting a rubbery or chemical smell.

– Lack of glamour. This type of stopper is not a marker of quality in the mind of the consumer, on the contrary it is associated with wines of lower quality, even low quality.

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