Identification of the molecules responsible for the odours
The laboratory identification of the molecules responsible for the odours detected in whisky can quickly become a true police investigation. Indeed, we may face the following situation:
In the detection of whisky aromas, analytical chemistry is a science that complements the sensory study. Its role is to chemically characterise the aromatic molecules responsible for one or several odours. To this end, the classic method used consists of 5 key steps: extraction, separation, detection, identification and quantification.
The laboratory identification of the molecules responsible for the odours detected in whisky can quickly become a true police investigation. Indeed, we may face the following situation:
The facts: an intense rose smell is perceived in an old whisky sample.
The witnesses: the smell has been confirmed by our panel of experts during the sensory analysis (see Master Notes #9).
The hypotheses: the rose smell is linked to the existence of one or several aromatic molecules present at higher concentrations in the sample.
To be able to solve such a case, our strategy is usually broken down into 4 main steps:
Step 1: the extraction
Amongst all of the whisky molecules, we wish to focus our attention on some of them. We will therefore extract them to form our group of suspects.
Step 2: the separation
To avoid them influencing or covering for each other, the suspects are individually questioned.
Step 3: the detection and identification
Each suspect molecule is asked for its identity card: its name, smell, molecular structure, and eventually any other physicochemical properties that might be of interest.
Step 4: the quantification
We determine their concentration in the sample, then we cross-check the different clues collected to identify the molecule(s) responsible for the rose smell in the said whisky.
The different steps of whisky aromas’ chemical analysis
At the different stages of the investigation, we will therefore use and combine several analytical techniques that will enable us to produce tangible evidence and in fine unmask the aromatic molecules responsible.
Analytical chemistry can be broken down into three main stages. Firstly, extraction, using a variety of methods, enables the targeted aromatic molecules to be recovered selectively. Next, the molecules in the aromatic extract are separated, then detected and identified in order to determine their chemical structure and qualify their concentration in the whisky. However, this breakdown into individual aromatic molecules and odours does not reflect the complexity of the aroma. It may therefore be appropriate to fractionate the whisky to see the synergies that occur on a molecular scale, and which truly reflect the sensory character of the final product.
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R&D | January 2025 | Dr. Magali Picard