Mixing odorous molecules
Two types of mixture can be identified:
The 'Gazette'
When odorous molecules are mixed together, the smell does not always correspond to the sum of the two individual smells.
Two types of mixture can be identified:
– A heterogenous mixture, if the smell of at least one of the compounds remains after mixing.
– A homogenous mixture, if the odour of the mixture is different from that of one of the individual compounds.
Therefore, the mixture of several odorous molecules may lead to perceptive interactions, with changes in both the nature of the smell and its intensity. If the two molecules have very different smells and volatilities, they will both be perceived. However, if the volatilities are similar, it is possible to create a new smell in precise proportions, called “an accord ” by perfumers. For example, the smell of dianthus can be obtained by mixing in a specific proportion, eugenol with its clove smell, and benzyl salicylate with its balsamic smell.
The notion of concentration is also important. Certain compounds present at levels above their perception threshold can alter the aroma’s intensity in wine or whisky: this is known as a masking effect, or on the contrary an enhancing effect. This is the case for example of compounds that do not necessarily have a fruity aroma but may nevertheless have a significant impact on the overall fruity aroma.
The smell of a molecule is inevitably linked to its chemical structure. Depending on its layout, our olfactory receptors will not be stimulated in the same way and will send our brain a specific sensory message. The presence of certain chemical functions, for example, will influence the molecule’s smell: the phenol function will confer a more smoked or animal character, and the ester function a rather fruity character.
But we can also observe that there are molecules with similar chemical structures that confer either similar or on the contrary completely different smells, and molecules with different structures that give similar odours: finally, everything is possible!
As you will have undoubtedly understood, a smell’s pathway from the whisky glass to our brain is a true labyrinth! Initiated by our olfactory receptors and transformed by our brain into a kind of “QR code”, our olfactory perception is the source of a multitude of interactions that enable us to smell a wide variety of aromatic molecules.
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R&D | April 2025 | Dr. Magali Picard