The bouquet of wine is best revealed by gently swirling the wine in a wine glass to expose it to more oxygen and release more aromatic etheric, ester, and aldehyde molecules that comprise the essential components of a wine's bouquet.
Pausing to experience a wine's bouquet aids the wine taster in anticipating the wine's flavors and focusing the palate. The "nose" of a wine - its bouquet or aroma - is the major determinate of perceived flavor in the mouth. Once inside the mouth, the aromatics are further liberated by exposure to body heat, and transferred retronasally to the olfactory receptor site. It is here that the complex taste experience characteristic of a wine actually commences.
The human nose is sensitive about 10 000 different smells. Émile Peynaud distinguishes ten classes of smells: animal, balsamic, woody, chemical, ethereal, spiced, aromas from distillation, floral, fruity, and vegetable.
Practically, you first smell the wine and after a time of oxygenation by swirling the wine in the glass, you take a deliberated sniff.
For me, smelling the wine in two step is the best way to appreciate its expressivity.
Because the aromas are volatile molecules, dont forget the good service temperture of the wine.
We distinguish three various categories of aromas:
• Primary aromas: these are varietals aromas that come from grapes. These flavours are observed immediately without swirling the wine in a glass (the first nose). They correspond to the substances which are easily vaporized and released by the evaporation of the wine's alcohol. They are influenced by climate, soil, the vintage.
• Secondary aromas they come from the fermentation (vinous character). These flavours observed for 10-20 minutes after shaking circular glass (2nd nose). They depend on maturity of grapes but also the wine making process decided by the wine maker.
• Tertiary aromas: These are more complex flavours which come from the evolution (oxidation / reduction) of the wine during the storing in bottle according the quality of the "terroir". These flavours are observed a certain time after opening depending of the age of the wine. (When you smell your empty glass, the aromas that remain).