This study covers some of knowledge already acquired about the chemical nature of wine. One of the key points is the surprising buffer effect of alcohol and other volatile components on aroma perception. This type of medium can hinder the perception of numerous odours, and in particular odours with fruity characteristics. The capacity of different aromatic molecules to overcome this buffer effect and consequently give different aromatic notes in the wine, can be used as a criteria to classify these molecules. Up until now, 14 chemical compounds have been identified which can overcome the buffer effect at natural concentrations which can be found in healthy wines. The actions of a group of molecules which share chemical and aromatic properties can represent another way to overcome the buffer effect. At least nine families of this type have been identified. In certain cases, the aromatic effect of the family only manifests itself in the presence of a third molecule which acts as an aroma exhauster. The third way to overcome the buffer effect is through the coupled action of several chemical molecules which share some of their basic descriptors. Evidently, the buffer system can also be negatively overcome by numerous molecules which can result in aromatic defects either individually or conjointly. It is the way in which this buffer system is overcome which determines the wine complexity and hence the aromatic characteristics of the wine. Study presented at Enoforum 2009, 21-23 April 2009, Piacenza, Italy

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