The easiest way to decribe the aroma of wine is the sensation which we are detecting with our noses. Different varieties of vines containing different aromatic substances. Until today, scientists have defined about 1300 different compounds in grapes, must and wine, and about 1,000 of them belong to the aroma compounds. Those 1000 aromatic compounds occupies only about 1% of all substances in wine, but regardless that content is so small, the impact on the sensory evaluation is huge. Part of these aromatic compounds are derived from grapes, and some of them are generated by processing grapes, and finally, the ageing of wine.
Scents of wine that originate from grapes are called the primary, and scents that arise in the period between harvest and fermentation are called secondary aromas of wine. Bouquet in a wine dictionary is a common designation for tertiary (aroma that is due to fermentation) and quaternary aroma of wine (also called a bouquet of maturity and aging). As wine is maturing, the initial flavors are degraded and transforming into a quaternary bouquet of wine. Wine loses fruity scents, freshness and varietal characteristics and gets a separate bouquet of age.