The 'Gazette'

The complex marriage of water and alcohol in whisky


Whisky contains a plethora of flavours and aromas. These are often revealed by a simple action: adding water. This delicate operation is a complex process combining chemical reactions and physical phenomena. In this article, we explain the interactions between water and alcohol, and how they influence the whisky-tasting experience.

Understanding alcohol content

Alcohol content, or alcoholic strength, is an essential parameter for assessing the concentration of ethanol in a spirit. In the case of whisky, this concentration must exceed 40%, a threshold that plays a crucial role in the perception of flavours and aromas. In fact, ethanol does much more than induce intoxication. It is a keystone for whisky’s sensory experience. In France, the spirits industry, with sales of €9 billion in 2018, demonstrates the importance of this beverage, which accounts for 37% of sales.

The challenge of dilution

The quest for new sensations is driving consumers to explore whiskies with varied aromatic profiles, sometimes at low alcohol content. But lowering the alcohol percentage without compromising aromatic richness is a major challenge. Indeed, dilution is not a miracle solution, as it can disrupt the delicate combination of flavours. It’s a precise exercise where every drop of water can alter the aromatic balance.

Systeme olfactif

Physico-chemical interactions

Whisky is made up of a complex structure within which a multitude of chemical compounds interact. When an aromatic molecule is influenced by its environment, scientists refer to this as the matrix effect. In other words, this means that the presence of other molecules, the pH of the whisky and especially its ethanol content can alter the volatility of the aromas. The more complex the liquid, the more important these interactions become, altering the way we perceive whisky.

The volatility of aromas

The aromas in whisky are carried by volatile molecules, capable of evaporating quickly and diffusing into the air. The addition of water changes the volatility of these molecules, influencing the way the aromas manifest themselves on the nose and palate. Understanding this phenomenon not only allows you to enjoy a whisky in all its magnificence, but also to adjust your tasting to reveal new, unsuspected nuances.

Polarity

Schematic representation of ethanol trapping hydrophobic molecules and their release when water is added.

A question of polarity

Not all volatile compounds react in the same way when in the presence of water. In fact, hydrophobic aromatic compounds will see their aromatic power intensify with the addition of water, whereas hydrophilic molecules are only slightly affected. At high alcoholic strength, hydrophobic molecules will tend to be trapped in ethanol micelles (affinity with the hydrophobic part of ethanol), with a higher ethanol concentration.

Whisky is a complex spirit whose sensory quality depends largely on the balance between water and alcohol. The physico-chemical interactions between these two elements are crucial, as they modify the molecular structure and directly influence the perception of the aromas. Controlled dilution therefore makes it possible to optimise the volatility of the aromatic compounds, making the tasting experience richer and more precise. Understanding these scientific processes is essential for anyone wishing to fully appreciate the nuances of whisky, transforming a simple tasting into an in-depth analysis of its organoleptic properties.

Would you like to know more about diluting whisky during tasting?