Each grape variety is characterized by a special aroma. However, it has not yet been conclusively clarified how the aroma is formed. Scientists from the Technical University of Munich, the Hochschule Geisenheim University and the University of Bonn recently made a contribution to clarifying this secret – with “possibly far-reaching consequences for the development of new grape varieties.” Ui.
It was already known that the so-called terpenes – a large group of chemical compounds – are responsible for the respective aroma profile, i.e. the varietal taste, of a wine. The composition and proportion of terpenes therefore determine whether a wine tastes more fruity or more spicy , for example. Incidentally, terpenes are also the main component of the essential oils produced in plants and an essential component of many cosmetic products.
Help, my wine tastes like turpentine
Bad puns aside, let’s continue with the hard facts: In the collaborative project funded by the German Research Foundation, the scientists say they have identified the mechanism for aroma formation in grapes : According to this, two specific enzymes are responsible for how high the terpene content – i.e. the Flavor Intensity – in grapes is. The terpene compounds are mainly found in the skin of the grapes, where they increase with increasing degree of ripeness. How much terpene accumulates in the grapes depends to a large extent on external factors, such as the length of sunshine or the soil conditions.
But there is a “problem”: terpenes are only aroma-active when they are free. This means that they can only contribute to the aroma if they are not bound by the plant, as Prof. Wilfried Schwab from the TUM Department of Biotechnology of Natural Substances explains: “During the plant’s metabolism, the terpenes undergo biochemical changes – usually through the accumulation of terpenes Sugar molecules ‘glycosylated’. In this bound form, however, the terpenes are no longer aroma-active.”Prof. Schwab refers to the Riesling grapes, in which only 20 percent of the terpenes are found in a free state. The researchers took a close look at the biochemical basis of terpene glycosylation, i.e. the binding and inactivation of aromatic substances – and discovered the two enzymes mentioned at the beginning that transfer the sugar groups to the various terpenes.
Breeding of new grape varieties with more aroma conceivable
Enzymes, terpenes, university… unambitious wine lovers can of course forget these confusing terms right away, as they play no role in everyday life and in party small talk you tend to get on others’ nerves with such knowledge. Nevertheless, the results and the consequences they may have are interesting: According to the scientists, the new findings could play an important role in the further development of grape varieties.
According to Prof. Schwab, the group has thus “found a fundamental mechanism that could be relevant for the breeding of new or the refinement of known grape varieties . ” Genetic profile expected a high proportion of free terpenes . Prof. Schwab: “The sugar-transferring enzymes are an important factor here. If the plant produces little enzyme, this also means low activity. The result: the aroma-active terpenes accumulate in the grapes.” Now the genetic profiles of the known grape varieties have to be determined – and off we go…brave new wine world.