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"Therefore, it only becomes apparent in the finished wine that the vineyard was exposed to a fire and the final product is of poor quality," said Hartl.Aromatic substances are volatile and in nature are attached to sugar, for example in plants.During fermentation, however, the wine yeast added by the fermentation process once again separates the sugar molecules and the smell develops.As a result, the grape vine stores smoke aromas that are no longer volatile.Due resveratrol, a substance with a health promoting effect, is naturally contained in the grape vine and in terms of its structure resembles the smoky aroma molecules."The smell and taste of such a wine is then often described with the term ash or ashtray.It describes a series of chemical or enzymatic reactions, for example, in which carbohydrates are bound to small, hydrophobic compounds such as aromas. This leads to a strong reduction in the quality of the wine," said Katja Hartl, scientist at TUM. This process is called glycosylation. An enzyme called glycosyltransferase is pet bottle mould Manufacturers responsible for this.The study, published in the Journal of Agricultural and Food Chemistry, got to the bottom of this smoky taste and is now described by Professor Wilfried Schwab and his team from the Professorship for the Biotechnology of Natural Products at the TUM.In the plant, the off-notes are then linked with sugar molecules by a glycosyltransferase - a protein that acts as a biocatalyst.The findings may pave the way for growers to eliminate this degradation in quality. Only when opening a bottle of wine is a strong off-note perceived.Researchers at the Technical University of Munich (TUM) in Germany described the reason why the smoke aromas are stored in the grapes.The aromatic substance can then once again be detached from the sugar and released.The smell is different from the barrique-produced wines, which taste "smoky" to some people.In the case of wine production, it is not initially clear whether there was a fire near the vineyard from which the grapes come.Scientists have found why wine cultivated in areas where forest fires are frequent have aromas that make the alcoholic beverage unpalatable. The aroma can be retained or stabilised with this sugary compound."Actually, the job of glycosyltransferase is to process the resveratrol," said Wilfried Schwab, professor at the TUM.As long as the grapes have not been harvested yet, the stinking smoke molecules are bound and the ashy smell and taste can not be noticed. This link with sugar molecules makes the smoky off-notes more water-soluble.If grape vines are exposed to bush fires, as happens more often in Australia, Southern Italy and California, the grape vine absorbs the smoky aromas via its leaves and fruits