Researchers gauge whiskey readiness using gold nanoparticles

In whiskey, the fingerprint of various flavor compounds is key to ascertaining if the spirit is ready for blending or bottling. Researchers at the University of Glasgow have found that these compounds react with gold salts to form distinctively colored nanoparticles , which could be used to indicate the whiskey’s maturity (ACS Appl. Nano Mater., 2022, DOI: 10.1021/acsanm.2c03406).

As they age in barrels, molecules in spirits react differently depending on factors like the wood they are stored in and the humidity and temperature of the warehouse, which means every barrel comes out slightly different. Currently, master blenders sample casks to gauge which are ready and which need to sit another few years.

The new test measures whiskey’s maturity by using the chemistry of the flavor compounds, says Jennifer Gracie, one of the authors of the study. When mixed with gold salts, molecules in the whiskey transfer electrons to the dissolved gold ions, which in turn begin to nucleate gold nanoparticles. The nanoparticles are invisible to the eye, but the color change they cause in the solution—to yellow or pinkish red—correlates with the spirit’s maturity.

Because the nanoparticles form within minutes, the researchers envision the technique as part of a quick and simple test to be used on the warehouse floor. They are also interested in linking the nanoparticles’ measurable properties, such as shape, size, and rate of formation, to the chemistry of the whiskey in a sort of fingerprinting tool based on the concentration of individual compounds in the sample. This, the researchers say, might give someone trying to blend a whiskey a clearer idea of which barrels are ready and which are not.

The nanoparticle test wouldn’t replace human master blenders, just make their work easier, says William Peveler, who also guided the research. “We can show how the wood and the spirit have interacted . . . but whether it tastes nice or not, that would be down to a person still.”