As Smooth as Tennessee Whiskey

Tennessee whiskey’s smooth flavor is the stuff of songs, but its production is a mysterious art form. Like Bourbon, Tennessee whiskey is made from 51
percent corn and aged in charred oak barrels, but Tennessee whiskey has to be filtered over sugar maple charcoal using the Lincoln County Process (LCP). Results presented at the American Chemical Society Spring 2019 National Meeting and Exposition (1) shed light on the effects of the LCP and could ultimately help distillers dial in the flavor profile their customers want.

John Munafo, leader of the study at the University of Tennessee, and student Trenton Kerley worked with the Sugarlands Distilling Company (Gatlinburg, Tennessee) to determine how the LCP affected the flavor of their Roaming Man Tennessee whiskey. First, Munafo and Kerley identified all the odorants in unfiltered whiskey using GC-MS and GC-olfactometry. Next, they worked out which ones were key to the unfiltered whiskey’s flavor using aroma extract dilution analysis and quantified these by stable isotope dilution. Analysis of whiskey that had been filtered by the LCP revealed dramatic changes in the levels of some of the odorants. After investigating different LCP parameters, Munafo says, “I was surprised by just how much leverage you have [ … ] and how changing the parameters results in different flavor chemistry in the distillate.”

To unravel the complexity of the samples, the researchers had to dig deep into the analytical toolbox. Munafo offers an example, “Labeled isotopes were used to quantitate the odorants in the distillate, using stable isotope dilution analysis (SIDA). Many of the deuterium- or C13-labeled odorants were not commercially available so had to be synthesized inhouse. In addition, we used a state-of-the-art high vacuum distillation technique, called solvent-assisted flavor evaporation (SAFE), which requires close attention and about half a day to prep one sample for analysis.” Ahead of the quantitative work, the team had to ensure that they were measuring the correct odorants in the distillate, for which GC-olfactometry was critical. “It is a laborious technique that requires a highly skilled technician,” says Munafo.

The ultimate aim? Munafo is confident that they will be able to advise distillers on what changes to make to the production process to obtain their desired flavor profile. And although water is Munafo’s beverage of choice, he likes whiskey a lot more now that he’s been studying it: “The flavor chemistry is fascinating,” he says. Controversially, Kerley prefers Bourbon (2)!