Live Better with Science: The Chemistry of Whiskey

Periodically we feature the research of an LAS faculty member, with an eye towards applying their science to our everyday lives. Janel Owens, Associate Professor in the Department of Chemistry and Biochemistry, describes here some recent research, and what it might mean for you…

Let me start by acknowledging Dr. Kevin Landis, Associate Professor in the Department of Visual and Performing Arts, for initiating this research direction by requesting that I participate in the lecture series Prologues in January 2014. I co-presented with Michael Myers, Managing Member of Distillery 291, by speaking of the chemical analysis of the flavor profile of Michael’s whiskeys. By the end of this collaboration for Prologues, Michael asked if I would become a certified distilled spirits chemist through the TTB. To this request, I very eloquently replied with: “Huh?”

Working with two other chemists in my Department (Dr. Keith Oppenheim and Luis Lowe) and with the help of Google, we set out to achieve certification for the analysis of distilled spirits through the Alcohol and Tobacco Tax and Trade Bureau (TTB, formerly ATF). In these proficiency tests to become a certified chemist, the TTB mails two bottles of different distilled spirits to the applicant for determination of several reportable compounds including: proof (by a variety of methods), caramel agent furfural, and fusel oils. Fusel oils, also called fusel alcohols, are higher boiling point alcohols often found in the “tails” cut of the distillation process. At high concentrations, they may have a negative and unpleasant sensory impact with flavors of solvent or antiseptic notes while at low concentrations of generally less than 50 parts-per-million, they add essential flavor and aroma to a mature whiskey.

The TTB asks for analysis of only a few compounds, but mature whiskey is incredibly complex from a chemical perspective even though it starts with such simple ingredients of malted grain, yeast, water, a still, and a barrel for aging. There exist thousands of chemical compounds in grain and yeast even before we add them together in the presence of heat, which drives many chemical reactions. Additional chemical complexity is achieved through the process of malting the grain and fermenting the simple sugars with yeast to produce ethanol prior to the distillation process and aging in a wooden barrel. By the 1960s, scientists had identified potentially 1300 compounds that may be of significant sensory impact including the following: 1) aldehydes (green, fresh, fruity, sweet), 2) volatile acids (sour, pungent notes), 3) fatty acids from the barrel (sour, musty, soapy, grainy notes), 4) esters from the yeast (floral, fruity, apple, honey, or butterscotch flavors), and 5) phenolics and lactones from the barrel (sweet, coconut, vanilla, peach, toast, caramel flavors). It is this chemical complexity that is of research interest to me.

Using some relatively new green chemistry techniques that we adapted from the literature or that were developed in my laboratory, we have now been profiling distilled spirits including whiskey, rum, and tequila to determine the important compounds responsible for complex flavor that make these distilled spirits unique in taste and aroma. Whiskey compounds including phenolics and furans are also antioxidants and the duration of aging in oak barrels adds to total antioxidant capacity of whiskey. We recently published a method for determining total antioxidant capacity of distilled spirits using silver nanoparticles. Determination of this antioxidant capacity is of interest because previous studies have determine that certain whiskies have higher antioxidant levels compared to white or rosé wines.

So why is this work of interest or important? Colorado is now home to over 70 craft distilleries and by achieving TTB certification and developing methods for profiling distilled spirits, we hope to help these businesses develop a better product and a better tasting experience for the consumer. So next time you take a sip of a locally made spirit, think of the many hundreds of compounds you’re ingesting that make for a unique tasting experience.

For Further reading:

Owens JE, Zimmerman LB, Gardner MA, and Lowe LE. “Analysis of Whiskey by Dispersive Liquid-Liquid Microextraction Coupled with Gas Chromatography/Mass Spectrometry: An Upper Division Analytical Chemistry Experiment Guided by Green Chemistry.” Journal of Chemical Education, 2016, vol 93, pgs 186-192.

Bukovsky-Reyes SER, Lowe LE, Brandon WM, Owens JE. “Measurement of antioxidants in distilled spirits by a silver nanoparticle assay.” Journal of the Institute of Brewing, 2018, DOI 10.1002/jib496

Written by Janel Owens, [email protected]

Submit ideas for a”Live Better with Science” feature to Mike Kisley, [email protected]