Bouquet is a French term for a wine’s scent. Younger wines have aromas, which are the smells associated with a particular grape and/or spice, its variety, region, or condition. Older ones have bouquet; the complex and deep aromas that develop with age. They are attributed to the process of fermentation, processing and aging, and largely develop after bottling.
You can tell 75% of what you want to know about a wine by the way it smells. Your sense of smell is much better than your sense of taste. You can smell as few as 400 molecules, but you can only taste 25,000 molecules or more. Your nose can distinguish between some 5,000 smells, but your palate can only register 4 tastes: sweet (this is the grape), sour (the acidity), salt (the rare saltiness), and bitter (this is the tannins). It is at the top of your nose that these 4 basic tastes are combined into thousands of nuances.
A finished wine has a mix of volatile organic compounds which cause its distinctive taste and smell, so they are partly responsible for whether you enjoy its bouquet. Scientists are interested in learning more about these volatile organic compounds so that they can help winemakers fine-tune their product.
In wine grapes, these volatile organic compounds tend to accumulate after the grape seed matures and as the flesh and skin of the fruit ripen. The balance of tart acids and sugars in the fruit changes over time too. The grapes trap volatile organic compounds by bonding them to molecules like sugars and amino acids, and winemakers release them by physically breaking those bonds (stomping grapes probably achieved this) and chemically breaking them with grape and yeast enzymes during fermentation. The grapes usually contain a variety of volatile organic compounds although one particular compound may dominate. The “grassy” taste of Sauvignon Blanc comes mainly from compounds called methoxpyrazines which are produced in unripe plant tissue and gradually disappear as the plants mature. The floral or fruity character of the sweet sparkling Muscat wines, comes from terpenoid compounds called geraniol and citronellol. People can detect very tiny amounts of these compounds; they sometimes respond to a flavor present at a few parts per trillion.
Wine consists of over 300 different chemical compounds. Many of these are similar or even identical to those found in fruits, vegetables, spices, herbs, etc. That is why a wine’s aromas are often described in terms of various fruits, vegetables, herbs and spices. A bouquet is formed when the primary grape smells, which are different depending on variety, are blended with the secondary smell characteristics such as fermentation and aging in bottles and especially in oak.
You can tell a lot about wine by the way it smells. Your nose is much more sensitive than your palate. The aroma of a younger wine, dominated by the smells associated with the grape, with the wine’s variety, region, and condition, blends with the smells associated with fermentation, processing, and aging (especially in oak barrels) to form a wonderful bouquet in an older one. Enjoy.