A special and increasingly popular type of closure (Screw cap, Twist or ROPP = Roll On Pilfer Proof Closure) of wine bottles as an alternative to the cork (natural cork) made from oak bark. These are made of corrosion-free metal (mostly aluminium alloy) with an internal sealing layer of polyethylene (PE), PVDC (polyvinylidene chloride) or tin foil. In the beverage industry this is also called MCA closure (MCA = metal closure aluminium). The emotional discussion as to whether this is associated with a "loss of culture" is countered by the relatively low-cost production and the fact that the problem of cork tasting with natural corks can be avoided. In addition, the often used pro-argument for the "plop" when enjoying wine as a sensual pleasure is not valid, because a bottle should be opened professionally as noiselessly as possible (this applies especially to sparkling wine).
In airplanes, for example, wine bottles have been available exclusively with a screw cap for decades. Nobody will find anything here, because the advantage of easy and unproblematic opening in narrow airplanes is obvious. A further advantage is that opened bottles can be closed again very easily. Also optically it was successfully tried to take into account the rejection of the cork friends against alternative closures. Externally, such screw caps as such are no longer recognizable as such. The first application for wine bottles was in Australia at the end of the 1970s, and the producers in the Clare Valley (South Australia) are regarded as pioneers. This was soon followed by many producers from New Zealand and California, before the boom also began in Europe.
In contrast to a cork, the empty space in the bottleneck of a screw cap is much larger. The volume is 15 millilitres, which means a relatively high oxygen content of 4.2 milligrams. Especially when bottling cold, air (and thus oxygen) remains in the empty space. For this reason, it is advisable to displace the air using inert gas or to seal the bottle under vacuum. A frequently voiced argument against screw caps is that due to the much better sealing than with natural corks, oxygen supply is only possible to a small extent (factor of three to four), which is, however, absolutely necessary for bottle maturation. However, this is rather an argument in favour of the screw cap. Because the oxygen in the bottle neck (nowadays often inert gas or vacuum) or in dissolved form in the wine itself is sufficient.
This was also impressively underlined at a Riesling-Tasting in Sydney-Australia 2003. A group of leading producers from all over the world were presented with a Riesling. The age was estimated to be between six and ten years, but in fact it was a 1982 Riesling, which was then closed with a screw cap. At least in this case, this indicates that maturation with such closures is slower, but the almost perfect sealing by the screw cap does not cause any loss of quality. Whether this is generally valid cannot be deduced from a single example, of course. However, there are numerous other examples showing that even with an absolutely tight closure, the maturing of the wine in the bottle is in no way negatively affected. This fact has also been fully confirmed by several test series in the German research institute in Geisenheim (Rheingau), for example.
Recent research (e.g. at the AWRI Australia) has shown that oxygen entering through the cap in the smallest quantities during bottle ageing can very well be beneficial for the development of the wine in terms of aroma and colour. Especially in Australia, the screw cap is very positively regarded. At the beginning of 2002 the Australian Multi Southcorp announced that all Rieslings (including Penfolds, Rosemount Estate and Wynns) of the 2002 vintage will be bottled with screw caps instead of natural corks. From the 2004/2005 vintage onwards, all Penfolds white wines will be sealed with this. This producer has also been very successfully experimenting with top red wines since 1995. No problems whatsoever could be detected, the wine matures completely evenly. In the year 2004 the Château Couhins-Lurton (Graves) followed as the first Cru-Classé-winery from Bordeaux, which closes its white wine, which belongs to the best in Graves, with a new screwdriver version.
More and more wine producers are switching to this technology. Especially in New Zealand with 90% and in Australia with 60%, the share of alternative closures is extremely high, with by far the highest share of screw caps. Significant growth was recorded in Germany (one third each of screw caps, plastic and natural corks), France, Austria, Italy and Spain, which leads in Europe with around two thirds of wines with screw caps, as well as Argentina and Chile. A very well-known brand is STELVIN, which has almost become a synonym for this closure type. VinPerfect offers a screw cap that contains microscopic holes in its cap through which air can pass. This supply of air in the smallest amount is called nanooxigenation (see Microoxigenation). See also under closures.