In the past few years, there has been a growing debate on the type of plug or cap that should be used to seal wine bottles. We hear lots about the advantages of using natural cork, rather than synthetic plugs or screw caps, but, in reality, in the majority of cases, the specific characteristics and advantages of each one are not completely known.
Plugs made out of natural cork allow the wine to breathe. This way, the wine’s oxygenation happens slowly, little by little, which ensures that the wine can evolve inside the bottle.
Until recently, cork was the only material that satisfied all the optimal conditions needed to seal a wine bottle. Cork plugs have the ability of limiting the entry of oxygen into the inside of the bottle, delaying the natural oxidation process of wine. These features make it the most suitable type of cap for crianza, reserva and gran reserva wines.
However, the growing tendency towards the use of more ecological products, as well as the high economic costs, have favoured the consideration of alternatives to this type of cap. Amongst these we find plugs made out of synthetic cork, which has been fabricated using plastics and silicon; as well as metallic screw caps.
If we analyse these part by part, we can identify the differences between these types of cap.
In first place, let’s consider the cork plug. Natural cork is extracted from the trunk of an oak tree, specifically from the bark, therefore not damaging the tree. This type of cap impedes wine from leaving the bottle, but is very permeable and lasts for very long. For these reasons, natural cork is the most appropriate material for wines that are meant to ageing the bottle. That is any wines which are kept in the bottle for long periods of time, where we expect them to improve and keep evolving.
Wine bottles capped with cork must be placed tilted in order to prevent the cork from drying out. When the cork is wet, it expands. This way, the cork fully seals the bottle and limits the entry of atmospheric air to the bare minimum, but naturally delivering to the wine the oxygen that is stored inside the cork.
Furthermore, the synthetic plugs are elaborated using plastic materials which have elastic properties. Amongst their advantages, we find that they come in a wide range of colours, that they maintain the uncorking rituals, and that these caps do not cause any trichloroanisole (TCA) problems. This is a wine fault characterised by undesirable smells and tastes of cork, which can sometimes happen with natural cork. However, the main inconvenient in these caps has to do with the conservation of wine, as these plugs barely allow the passage of oxygen through them. Thus, wines are prevented from evolving inside the bottle.
An example of this type of caps are silicone caps. These plugs close the bottle hermetically, preventing any air from entering the bottle. For this reason, these caps are ideal for young wines which we don’t expect to evolve much more and are usually consumed quickly – usually within the first two years after the wine was bottled. The danger, however, is that wines can become oxidised faster and there can be a slight absorption of the wine’s scents, which makes it lose some of its aromatic intensity.
This kind of caps were, initially, totally airtight. However, manufacturers now are coming up with new, diverse ways to allow the entry of oxygen into the wine bottle. The main problem here is that, as the years go by, the cap starts to reduce in volume, losing its capacity to fully seal the bottle.
Finally, the screw caps are the easiest and most convenient caps to open, as there is no need to use a corkscrew. In the same way as synthetic plugs, these caps are used for young wines of immediate consumption. Its efficacy has also been tested in white wines, as it maintains their freshness and, in the same way as plastic plugs, they allow wines to be stored vertically.
The habit of using screw caps is settling down mainly in the hostelry and catering services. This is because these caps have a very economical price and their use is very practical, allowing people to very quickly open and close bottles and serve and sell wine by glasses. However, this kind of cap makes the wine lose a lot of its elegancy, lose its uncorking ritual and, in addition, it does not allow the wine to breathe.
The emergence and rise of the last two types of caps – synthetic and screw – has been mainly widespread by wine producers in Australia, New Zealand and South Africa. These countries of Anglo-Saxon influence are becoming new wine producers at a worldwide level and have ignored and by-passed the use of cork as a closing device. However, Spain, Portugal and France, natural cork producers, are still opting for traditional plugs made out of cork.