Impact of the rate of spirit distillation on floral aromas in single malt whisky

Why was the work done: The distillation rate in pot stills shapes the aromatic profile of single malt whisky. Floral notes are prized for their contribution to complexity and elegance, yet the impact of natural reflux in Charentais stills and modulation of flow rate during the second distillation remains poorly understood. This study considers how variations in distillate flow rate affect the floral aroma of new make spirit and assesses the effect of a stepwise distillation process on aromatic complexity. Also, the role of floral-related volatiles (monoterpenes, C13-norisoprenoids, and esters) is evaluated in floral perception together with potential synergistic interactions. How was the work done: Five distillation profiles were tested, varying heating power during foreshots collection to influence reflux and applying stepwise flow rate changes during heart distillation. Here, 'reflux' refers to passive condensation of vapours in the swan neck and head, induced by temperature gradients and inferred from operational conditions rather than being directly measured. Sensory evaluation assessed the aromatic complexity and intensity of floral, fruity, and solvent notes. Targeted GC–MS quantified floral-related compounds, while sensory reconstitution in a model spirit examined interactions between monoterpenes, C13-norisoprenoids, and esters. What are the main findings: Reduced natural reflux during foreshots, combined with gradual, stepwise heart distillation, significantly enhanced the floral intensity and aromatic complexity. Optimised conditions increased the levels of linalool, β-citronellol, β-damascenone, and some esters. Sensory reconstitution confirmed the synergism between esters, monoterpenes, and β-damascenone, amplifying floral perception beyond individual contributions. Why is the work important: The results show that modulation of distillation rate can be strategically applied to refine the aroma balance and improve whisky quality, while highlighting the importance of aroma-aroma interactions in enhancing floral expression.