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Dr. Schmitt is head of the Bavarian State Institute for Viticulture and Horticulture, Würzburg - Veitshöchheim. The following article is an excerpt from his book "Das neue Buch vom Frankenwein" (1997 Echter Verlag Würzburg) and is published here with the kind permission of the publisher and author.

Almost every wine lover has encountered it: the troublesome cork spirit that can so abruptly end the pleasure of enjoying wine. Its occurrence is all the more annoying the more valuable the bottle contents in question are. A stopper made of natural cork is considered a sign of a good wine. Nevertheless, it is not the ideal bottle stopper; regularly it even contributes to spoiling the wine it is supposed to preserve in the bottle: namely through the "cork taste".

This defect cannot be clearly defined; it can have various causes. Externally visible causes are mould infestation or the invasion of the cork moth. This only occurs extremely rarely nowadays, and then mainly in very damp, old cellars. However, it can be effectively combated. Cork is a natural material. The cork fabric consists of membranes whose cell walls are made of cellulose (supporting substance), cork wax (largely impermeable to liquids and gases) and a lignified layer (gives strength). Cork (lat. cortex = bark) is obtained from the bark of the cork oak (Quercus suber), which for climatic reasons thrives almost exclusively in the western Mediterranean countries. Its cultivation area amounts to around 2.7 million hectares. The tree protects itself from drying out, heat and pests with the several centimetres thick, regrowing bark.

More than 50% of the bark is extracted in Portugal, about 20% in Spain. Other notable producing countries are Algeria, Italy and Morocco. In processing, i.e. in the production of the end product bottle cork, Portugal ranks far ahead with almost 80%. The trees grow to a height of eight to ten metres and have a useful life of about 200 years. The bark can be peeled off for the first time when the tree is 25 years old; however, this "virgin bark" may not yet be used for the production of bottle corks. Further harvests take place at intervals of 9 to 12 years. After harvesting, the bark is stored for a year or more, then boiled in water, pressed, cut into plates of manageable size and sorted according to quality. Then strips are cut from the slabs, from which the cylindrical plugs are finally punched out. These blanks still have to be smoothed on the front surfaces and ground round. This is followed by bleaching, sorting according to quality, impregnation with a waxy substance (to make the stopper slippery) and finally cork firing (today usually an imprint). The more precious the wine, the longer it is to be stored, the better the cork that closes the bottle must be. A high-quality cork must have only a few pores that are perpendicular to the annual rings. Even the best cork, however, can cause a "cork taste", the notorious "musty sound".

The prerequisite for the formation of the substances responsible for this is extremely complicated; both biological and chemical processes are involved. The storage conditions of the cork boards in the production facilities have a significant influence on the formation of such foreign notes. This is because they are covered with a layer of mould caused by micro-organisms. The presence of these different mould cultures can then lead to problems with the later bottled wine. This is because the chemical compound "trichloroanisole", which essentially causes the typical cork mustiness, can be produced by these same microorganisms during the storage phase and also later. Already at a content of 50 billionths of a gram of trichloroanisole (corresponding to

(corresponding to the solution of a lump of sugar in a quantity of water contained in 3000 tankers), a bottle of wine can be expected to become undrinkable. In addition, other compounds, which are only noticeable in terms of smell and taste at much higher concentrations, can have a negative influence on the taste of the wine.

Today, the cork is in competition with other closures in the wine industry, which fully meet the actual requirements, namely to protect the wine from evaporation losses and atmospheric oxygen and to be neutral in taste. These are the screw cap or screw cap and the crown cork.

By the way, it is a misconception to believe that the wine needs the natural cork to "breathe" or to develop. Just the opposite is the case, any access of oxygen to the wine via the closure is disadvantageous. Comparative storage tests have clearly confirmed this. They have also led to the realisation that viticultural experiments can only deliver credible results if the wines in question were sealed with a neutral closure, by no means with the natural cork.

It should be remembered that decades ago, high-quality wines with a high storage potential were covered with sealing wax on the cork to prevent atmospheric oxygen from gaining access. Here the wine could not "breathe" either, and how splendidly these wines developed!

Natural cork or screw cap? A question that immediately arouses emotions in the consumer. He does not want to accept the screw cap, especially not for the Bocksbeutel. For them, good wine and natural cork belong together, even if the "pop", which God knows cannot be associated with quality at all, has to serve as the main argument for "pro natural cork". Ratio fails here. That's all right, but... only if the problem of "cork taint" were not a problem. It is very fatal for the natural cork user to have to know that there are not enough first-class corks - nature does not allow for more - and that even the best (and most expensive) corks only guarantee a good seal, but are in no way inferior to the others in terms of cork smell. Another alternative

to natural cork of the conventional kind, the so-called pressed or agglomerated cork, which is made from waste products, is no alternative at all, because the risk of missing a sound is much higher here, is already pre-programmed, so to speak.

As long as wine bottles are sealed with natural corks, the wine drinker has to reckon with the cork taste. Even if greater care were taken during production, it could never be completely avoided.

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