Science News takes appreciation of American whiskeys to a whole new level – a teeny-tiny one. Researchers publishing in Physical Review Fluids found that bourbons, unlike other spirits, leave unique web-like traces when evaporated, which can be used to identify each whiskey:
Researchers at the University of Louisville in Kentucky discovered these “whiskey webs” by evaporating bourbon droplets diluted with different amounts of water and examining the dregs under a microscope. Bourbons with alcohol concentrations of at least 35 percent left uniform residue films previously seen in experiments on Scotch whisky, while bourbons with alcohol concentrations of about 10 percent left markings similar to coffee rings.
To the researchers’ surprise, almost every American whiskey diluted to around 20 percent alcohol left behind a unique, weblike microstructure. Fluid dynamics researcher Stuart Williams and colleagues suspect that compounds that leach into the whiskey while it ages in charred oak barrels create these webs. “A lot of [those compounds] do not like water,” he says, so diluting the bourbon forces those particles to flee toward the surface and form a skin over the droplet. As liquid evaporates away, that film contracts and buckles to create a network of wrinkles.
“We think each brand leaves a different pattern because each [surface film] has a different chemical composition,” Williams says.
Williams’ team couldn’t create similar webs using Canadian or Scotch whiskies, suggesting that whiskey webs are vestiges of flavor compounds specific to American whiskey distillation….
You can read the original study here.