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The professional assessment of the quality of a wine by tasting requires a lot of experience and yet seems to be highly subjective. Yet, it is still hardly valid to replace it by scientific methods. This, at least, was the result of an ambitious research project of the renowned Max Planck Institute for Molecular Plant Physiology with the Universidad Técnica Federico Santa Maria, Valparaiso in Chile, which was dedicated to the so-called "chemical fingerprint" of a wine, i. e. the analysis of its complex chemical components. The institute pursued the question which parameters determine the quality of wine and whether these could then serve as biomarkers for wine attributes, in order to be able to determine objective criteria for the evaluation of wine. So, it was hoped for substances as measurable parameters for grape variety, origin, wine quality and vintage. It is known that every single step of the wine development leaves traces in the form of characteristic ingredients in the wine. Although many wine constituents are known, most studies have so far been limited to the analysis of specific groups of molecules, such as volatile or phenolic substances, anthocyanins etc. Some authors have at least succeeded in determining some reproducible parameters, e.g. for grape variety and origin.

Industrial viticulture off the peg for the discounter shelf (Photo: M. Kössler)

This research project aimed to find universal parameters for the entire spectrum of wine quality. For this purpose, highly complex analytical, but also mathematical methods were used. A surprisingly small number of common constituents were discovered in the red wine varieties tested. Only 9 percent of common substances could be detected. Nevertheless, about 30 percent of the substances found turned out to be characteristic biomarkers for one wine variety, the remaining 60 percent could be detected in several, but not in all wine varieties. On the other hand, up to 6,400 different ingredients were discovered in the pure varietal wines examined, more than half of which had not been known as ingredients of wine so far! This leads to the conclusion that a part of the positive effects attributed to wine could be due to these so far unexplored ingredients. In any case, with all the available analytical methods it was not possible to analytically define qualitative differences between medium and high wine qualities. This separation was only possible when the wines of a winery were compared with each other. Universal quality criteria could not be determined in the qualitative peak as chemical or physical parameters. Therefore, one is still dependent on the sensory evaluation of experienced tasters.

Chemical war in the vineyard% as it is still common (Photo: M. Kössler)

During the evaluation of a wine, a good taster draws on his extensive detailed knowledge of the work in the vineyard and the vinification. He knows every single building block that leads to the finished whole and is well aware of its influence on colour, aroma, taste and wine quality - from pruning, which is crucial for yield and thus for the concentration and inner density of a wine, to soil cultivation, which is crucial for water balance and thus for stress factors such as bitterness etc., to leaf control and vine training, which are decisive for phenol and tannin quality. He connects every detail in the vineyard and cellar with the corresponding taste and smell components in the wine to be judged and thus analyses it technically and sensorially.

Classic agro-chemical viticulture of the winemaker around the corner (Photo: M. Kössler)

Thus, a sensitive and experienced taster, without knowing the vineyard and cellar of a wine, can smell and taste whether it was harvested by machine or by hand, whether it comes from high yield, poor harvest and unambitious technical development in the cellar and therefore may taste quite "delicious", but has no soul; he can judge whether a wine comes from old vines, was pressed from healthy harvested, perfectly ripe grapes, whether the must was fermented spontaneously and then stored for a long time on the yeast and thus delivers a wine full of character with mouthfeel and charisma.

Committed organic cultivation (Photo: M. Kössler)

The most important criterion for wine evaluation is therefore the vineyard. This is where quality characteristics and sensory "parameters" are created in the wine, which can neither be replaced nor manipulated in the cellar. All it takes is one look for the expert to know whether the winemaker is working as he claims to be. It is in the vineyard that it becomes clear whether the winegrower understands his craft in harmony with nature and puts his heart and soul into his work in order to press must from perfectly ripe grapes, which he does not have to do much about in the cellar, or whether he sticks to recipes and spraying plans of agricultural chemistry in order to produce grapes which he has to process in the cellar into what he wants to have in the bottle afterwards. The difference between bad and good wine is more than taste judgment. It is based on hard visible and tangible facts. The vineyard does not lie... you just have to recognize it!

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