Whiskey ‘webs’ could be used to spot counterfeits

The pattern left behind when spilled whiskey evaporates could provide a way to distinguish genuine drinks from cheap imitations, according to researchers in the US.

Writing in the journal ACS Nano, the team from the University of Louisville in Kentucky – the state arguably most closely associated with American bourbon – note that diluted whiskey droplets form characteristic ‘webs’ that are “a function of the intrinsic molecular constituents of the liquor.

Using time-lapse scanning electron microscopy (SEM), the researchers examined droplets of diluted American whiskey as the liquid evaporated.

Interestingly, the patterns were not evident with Scottish or Canadian whiskeys, providing an immediate way to separate drinks from different regions, and also did not occur with American whiskeys that were not aged in charred oak barrels.

Similar structures were however generated with other whiskeys under different conditions. American whiskeys are generally aged in new, rather than reused, barrels, and that may allow more web-forming compounds to leach from barrels into the whiskey.

The team think that non-volatile organic compounds, such as phenols, aromatics and esters, cluster together and are driven to the surface of the droplet, where they formed monolayers as it evaporates.

As the surface area of the droplet decreases, the monolayers collapse, creating the strands of the web.

The researchers showed that different American whiskeys showed unique web patterns that could be correctly matched to unknown samples more than 90 per cent of the time using digital image analysis.

The webs were distinct to a particular whiskey and were also reproducible, meaning the same brand would behave the same way on re-testing. The findings suggest it could be feasible to develop a smartphone camera and app to carry out the analysis.