The choice of a good cork for a bottle of wine plays a very important part in keeping the wine in good condition. A bad choice can bring great efforts to nothing, and more so if the wine is to be matured or cask-conditioned as a crianza.
Its principal function is to avoid any kind of external agent from entering the bottle: micro-organisms, smells and, above all oxygen.
Until quite recently, the only material for closing a bottle of wine has been natural cork. Over the last few years, however, it has become more common to find different materials when opening a bottle of wine. Here we describe the three most common.

Natural cork:
Not without reason is it defined by some as the sacred cork. It is natural, from the species of cork tree or cork oak known as Quercus suber. There are many different qualities, types and prices available on the market. The best quality corks can last up to 15 years in the bottle, always when well conserved. The biggest drawback is, as it is natural, it is prone to an infirmity, colloquially referred to as the wine being “corked”. This is when the odour due to the presence of trichloroanisol or TCA is given off. The best quality corks have the least possible number of pores and should be compact – the use of this type of cork is synonymous with quality wine.

Synthetic:
There are a number of materials on the market, normally polymers of plastic material. There are many colours, according to the taste of the wine producer. Its advantage is that it does not produce odours or tastes and it is used in rapid-consumption wines (young wines). Disadvantages: it is not as flexible as cork, in some cases difficulty being encountered on extracting this type of plug due to its rigidity and, particularly in the old winemaking world (Europe), it does not have a good reputation. Finally, and according to the latest studies, after 12 months in the bottle, the entry of oxygen (the greatest enemy of wine after being bottled) increases considerably.