Chemical Nature of Varietal Aromas
For many years, the different aromas of wines were chalked up to mystery. With the advancement of chemical isolation techniques, we can now attribute a particular aroma with a chemical present in that wine.
The Role of Varietal Aromas in Wine Chemistry
The aromas we smell when wine tasting are from volatile compounds; which are molecules that can take the gaseous state at room temperature. These molecules will leave the surface of the wine, enter your nasal passages and deposit on your olfactory bulb.
Varietal aromas arise from these volitile compounds; For example, the molecule mercaptan 4-methyl-4-pantan-2-one is found in Chenin Blanc and gives wines made from this varietal a “guava-like” smell.
Mercaptan 4-methyl-4-pantan-2-one has a specific chemical structure (which we will not get into) that is very unique. By the glory of nature, the olfactory bulb in our noses has a receptor that fits this molecule. So when it binds to our receptors, a signal goes to our brain, and we associate that smell with guava, which probably has a very similar volatile chemical.
So the presence of these volatile chemicals gives the wine its characteristic aromas. So how does this relate to varietals?
Each varietal is genetically distinct from others. Because of this, it produces chemicals in different concentrations. Some produce chemicals that are unique to that varietal, some produce chemicals that are in different proportions to other varietals.
Therefore, there are chemical differences between varietals, and these are what distinguishes one varietal from another. Have you ever wondered why you love Cabernet Sauvignon, or what gives Chardonnay apple like flavors? The volatile chemicals produced in the Cabernet Sauvignon and Chardonnay vines are the reasons.
Most varietals do not have specific aromas. But several do, and these are the defining aromas that characterize wines made from those grapes.
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