Long chain esters in the spotlight: analysis of the aroma between traditional whisky and analogous age-accelerated spirit

Why was the work done: Consumer interest in distinctive, high quality alcoholic beverages has driven innovation in whisky production, particularly in ageing techniques. While traditional oak barrel ageing is essential to the legal definition and flavour development of whisky, new approaches such as the Jensen Reactor - an accelerated ageing method combining ultrasound, temperature, oxygenation, pressure, and catalysis - aim to replicate the chemical changes of barrel ageing in one to two weeks. However, how such accelerated methods compare to traditional maturation lasting many years remains unclear. How was the work done: The study focused on the quantification of medium and long-chain fatty acid ethyl esters in malted rye and barley spirits comparing the new make spirit, accelerated-aged spirit and traditional whisky. Volatile organic compounds were characterised using stir bar sorptive extraction coupled with gas chromatography-mass spectrometry (SBSE-GC-MS). What are the main findings: Most C2–C12 ethyl esters increased in concentration during accelerated ageing, often surpassing their sensory thresholds and likely contributing fruity notes. Ethyl acetate, by contrast, was reduced to near or below threshold levels (25-30 mg/L) in accelerated aged samples, while present at 120-300 mg/L in traditionally aged spirits, which presumably contribute a solvent-like aroma. Long-chain esters (C14–C18), commonly linked to waxy characteristics, remained relatively stable across both ageing methods reflecting their initial concentration in the new make spirit. Additionally, ethyl linoleate decreased during traditional ageing, whereas ethyl tetradecanoate increased; the underlying mechanism for this is currently unknown. Why is the work important: These findings highlight the importance of understanding ethyl ester formation to improve aroma development and quality in whisky or spirit production and maturation.