The 'Gazette'
Beyond the simple taste experience, whisky tasting is an art in which every detail counts. Although frequently done, diluting whisky with water can often be a source of confusion. This article takes you to the heart of the scientific mechanisms that explain how this dilution can sublimate the aromas and influence the delicate balance of the whisky’s flavours.
Alcohol, mainly in the form of ethanol, is the key element that defines the personality of whisky. Not only does it influence the mouthfeel, but it is also responsible for releasing subtle aromas. The aromatic compounds present in the spirit, although highly concentrated, play a major role in the overall sensory experience. However, a too high concentration of ethanol can unbalance this harmony by altering the aromatic perception.
Many connoisseurs add a few drops of water to their whisky. This practice is not trivial and has a simple explanation: water interacts on several levels with ethanol and aromatic compounds. This allows certain aromas to be released more easily. Dilution also reduces the intensity of the ethanol, revealing aromatic nuances that are often masked. This enables the complexity of the whisky to be seen in a new light.
The volatility of a molecule is defined as its ability to transform into vapour, which is crucial for the aromas to reach your nose. In whisky, the light, volatile molecules escape easily, whilst the heavier compounds – responsible for the flavour – are left behind. The solubility of the molecules depends on their affinity for water (hydrophilicity) or for organic solvents such as ethanol (hydrophobicity). This is an essential factor in understanding the effect of dilution.
Ethanol is a so-called amphiphilic molecule, capable of binding to both water and organic compounds. This unique property enables it to dissolve a wide range of aromatic compounds, increasing the range of flavours perceived. Diluting whisky with water alters the interaction between ethanol and these compounds, which can enhance previously discreet aromas.
The partition coefficient (K) is an indicator of how a molecule is distributed between the whisky and the air above the glass, known as the headspace. A high coefficient means that the aroma is more concentrated in this space, intensifying the olfactory perception. By diluting, the partition coefficient of each molecule changes, modifying their distribution between the liquid and the headspace. This has a direct impact on sensory balance.
Schematic representation of the distribution of an aromatic molecule between the whisky matrix and the headspace.
Diluting whisky is a delicate art, enriched by an understanding of the underlying chemical principles. By mastering the nuances it becomes possible to sublimate your tasting experience, revealing hidden aromas and complex flavours. The science behind dilution is the key to fully appreciating the subtleties of your favourite spirit.
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Tasting | October 2024 | Dr. Magali Picard