Chromatography Finds the Secret to Tennessee Whiskey

There are certain processes, ingredients or geographical regions that are special to specific foods and drinks. Champagne has to come from grapes grown in a specific region of France, Melton Mowbray Pork Pies have to be made in Melton Mowbray and Blue Mountain coffee beans have to be from coffee plants grown on a certain mountain side in Jamaica.

To be called Tennessee whiskey, a whiskey has to legally undergo a process known as the Lincoln County Process (LCP). At the American Chemical Society Spring 2019 National Meeting, researchers at the University of Tennessee discussed how they have investigated what makes the LCP give Tennessee Whiskey its unique flavour.

Lincoln County - original home of Jack

The Lincoln County Process is a filtration step that uses charcoal from Sugar Maple trees. The wood from the tree is made into planks, stacked and burned to make charcoal. Freshly distilled whiskey that has not yet been aged is then passed through the charcoal to filter it. In a press release, one of the researchers Trenton Kerley said:

‘Although Tennessee whiskey and traditional bourbon both have to be made from 51 percent corn and aged in charred oak barrels, the distinction is really this filtration step.’

Whiskey production is still an art form to a certain extent. Despite all the instrumentation, the final taste and flavour of the finished whiskey is still decided by the taste buds of an experienced distiller. And until now, no one has studied the effect of the LCP step in the whiskey manufacturing process. Researcher John Munafo said that: ‘by probing the fundamental chemistry of this process, his team could help distilleries achieve the flavor profile they desire and reduce product variability.’

Chromatography analyses the flavour profile

To see what effect the LCP had on whiskey, the team first established a flavour baseline by identifying and quantifying the aroma active molecules in unfiltered whiskey provided by a distillery. To carry out this analysis they relied on gas chromatography-olfactometry and gas chromatography-mass spectrometry. GC-MS is a powerful analytical technique that is not confined to the laboratory as discussed in the article, Employing the Power of Gas Chromatography/Mass Spectrometry in the Field.

After determining which compounds were important for the flavour of the whiskey, they filtered the whiskey with some sugar maple charcoal. Afterwards, they analysed the samples to see which of the flavour important compounds had been removed or reduced. Kerley said: ‘I was expecting it to have an effect, but I wasn't expecting as large of an effect as we saw in some of the compounds. For example, levels of some compounds declined by up to 30 percent after LCP.’

The researchers plan further trials using a more realistic filtration process. The aim is to help distillers understand more about the process - so producing even more Tennessee whiskey.