Large group of aromatic substances in wine, which are primarily perceived in terms of smell, but also in terms of taste, and which have a significant influence on character and quality. These are mostly volatile compounds which are initially still odourlessly bound in the grapes as glycosides (sugar compounds). They are therefore called aroma precursors, from which the primary aromas develop during ripening. Soil type, temperature, exposure (sunlight) and water content in the soil have a great influence on the formation of aromas during the ripening period. The ideal condition is when the grapes are at their optimum physiological ripeness. By means of the measuring method glycosyl-glucose assay the aroma precursors in the grapes can be quantified and a quality prognosis can be made.
During fermentation and ageing, new aromas (secondary aromas) develop differently depending on the container and the type of ageing. Further aroma substances are transferred from the barrel wood into the wine during barrique ageing. During bottle ageing or increasing ageing, the aromatic substances are slowly converted by hydrolysis and form the third aroma (tertiary aroma). Overseas there are attempts to accelerate the process by means of appropriate enzymes. Even the smallest amounts of a billionth of a gram in a litre of wine are enough to be perceived. Much smaller amounts of trillionths of a gram are still sufficient for analysis.
Wine contains around 7,000 different substances. The approximately 50 most frequent of these, together with their interaction, make up the composition or the very special quality of a wine. Especially the manifold aromatic substances characterize the aroma or bouquet of a wine and can be clearly identified and named by a professional taster (wine taster) during a wine evaluation. This can also be learned through appropriate practice. Even untrained persons can relatively easily recognise the aromas of bitter almond, butter, blackcurrant, strawberry, clove, yeast, coffee, cherry, coconut, nutmeg, paprika, pepper, vanilla, lemon and plum.
Aromatic substances or aromatic groups in wine are anthocyanins, carotenoids (and norisoprenoids resulting from chemical processes, such as damascenone and TDN), esters, eugenol, furfurale, lactones, lignin, linalool, megastigmatrienone, methoxypyrazines, nerol, phenols, sotolone, tannins, terpenes, thiols, vanillin and ethyl cinnamate. Some act like pheromones with aphrodisiac effects. Oenological enzymes and oenological tannins also have a taste-modifying effect. Where the limit for wine adulteration is exceeded by prohibited substances, it can be determined in some cases by Nuclear Magnetic Resonance (NMR) or mass spectrometry, even in the smallest quantities (0.001%) (see also under ADI).
The successful decoding of the complete grape genome by Italian and French scientists was announced in 2007. Among other things, some wine aromas were also genetically identified. The completely new analytical method, metabolomics, was tested at the Max Planck Institute. See on this topic under DNA and molecular genetics, as well as under the keywords aroma wheel (aroma circle), aroma set, aromatizing and Coca-Cola wines. Regarding the other ingredients in wine, see under total extract.
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