Of the different ingredients necessary to produce whisky, water is certainly the raw material that is the hardest to measure, whether it being the impact on the malted barley or on the whisky itself. However, depending on its mineral and organic ion composition, the water chemistry shapes the aromas and the taste. Often used as a communication and differentiation point by distilleries, the water consumed during the brewing and fermentation processes is a key component that determines the quality of the distillate that will then be matured in oak barrels.

As a matter of fact, the salts dissolved into the brewing water interact with the malts’ compounds, affecting, in fine, the wort’s flavour and aromatic profile. Furthermore, the salts influence the pH, and provide trace elements that are essential for the growth of fermentation yeasts that are responsible for the development of fruity aromas. Therefore, this article will explore the sensorial and chemical impact of brewing water in producing whisky, whether it being Bourbon, Scotch whisky or French whisky.

Due to its many essential qualities in barrel making, the main wood used in cooperages is oak, especially for spirit and eaux-de vie maturation as well as whisky maturation. Other than its mechanical properties (strength), it also has excellent thermal insulation and remarkable watertightness. Oak growth depends on multiple factors (genetics, geography, climate), that consequently affects the grain size and chemical composition. Depending on the growth conditions, the heartwood (or perfect wood) of the three main oak species used in cooperages (Quercus petraea, Quercus robur, and Quercus alba) has a specific polymer structure and specific aromatic molecules, that will influence the aromatic quality and sensory characteristics of whiskies aged in barrels that are revealed during tasting. 

Whether it is for the creation of single malts or blended whiskies, each distillery will choose their barrels depending on the aromas to achieve during maturation and sought after by connoisseurs: coconut aromas and smoothness for American whiskies (Bourbon), finesse and balance for Japanese whiskies, roundness, complexity, and fruity aromas for Scotch whiskies.

The barrel making process in cooperages involves a series of steps that influence the oenological quality of the wood. As we have seen previously, the geographical origin determines the structure and the chemical composition of the wood.

Once the selection has been made and after the transformation of logs into rough staves, the last crucial step is drying the wood. During this process, the oak wood will go through different stages: dehydration, rehydration, and finally it will balance with the ambient humidity. This natural seasoning, through various complex transformations modifies its physical and chemical properties, encourages wood maturation, reduces bitterness and astringency, and increases its aromatic properties.

This evolution in the wood’s structure is decisive for its future transformation into barrels.

Olfaction is one of the five human senses: it allows us to detect and perceive odorous molecules, through our nose but also through our mouth.

Olfactory receptors are the keystone to olfaction. Everything begins with a volatile molecule that travels to our nostrils to reach the olfactory receptors. Once bound to one (or several) receptors, the molecule activates a kind of switch that starts the creation of a mental image for the smell in the brain.

Depending on their chemical structure or their orientation in space, the odorous molecules can activate our receptors differently, altering our olfactory perception. But it is also the combination of the olfactory system with the trigeminal and gustatory systems that gives us more information about what we are tasting.

Finally, our sense of smell is subject to the complex phenomenon of molecular synergies: combined together, odorous molecules may interact and therefore intensify, reduce, or even create a new smell.