Understanding what makes Tennessee whiskey unique

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The sugar maple tree yields autumn foliage, maple syrup and Tennessee whiskey. Wood from the tree is chopped into planks, stacked in piles and burned to form charcoal. Freshly distilled, un-aged whiskey is filtered over the charcoal in a mysterious, but necessary step known as the Lincoln County Process (LCP). By law, a product cannot be called Tennessee whiskey without it. Researchers now say they have some clues as to what the process imparts to the final product.

The researchers will present their results today at the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition.

"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," says graduate student Trenton Kerley, who performed the work.

Even in this modern age, whiskey making is still a bit of an art form. Distillers currently adjust their product empirically at the end of a long process of brewing, filtering and aging. They blend different batches to achieve a certain flavor. But until now, no one has systematically studied the effects of the LCP step, so named for the county where the original Jack Daniel's distillery was located. John Munafo, Ph.D., leader of the study at the University of Tennessee, says that by probing the fundamental chemistry of this process, his team could help distilleries achieve the flavor profile they desire and reduce product variability.

Munafo's group partnered with the Sugarlands Distilling Company in Gatlinburg, Tennessee, to figure out how LCP affected the flavor of their Roaming Man Tennessee whiskey. To do that, the researchers first established baseline values for its flavor. They began with unfiltered whiskey provided by the distillery. They identified all of the aroma-active molecules (odorants) of the beverage using a combination of gas chromatography-mass spectrometry and gas chromatography-olfactometry, a technique by which a scientist can smell the individual components of a sample as they are separated. They then determined which of these was important to the whiskey's flavor with a technique called aroma extract dilution analysis, in which aroma-active compounds are diluted until they no longer be smelled. Finally, the key odorants were quantitated by stable isotope dilution assays.

After identifying the compounds that contributed to the unfiltered whiskey's flavor, they exposed it to sugar maple charcoal also obtained from Sugarlands. Based on a procedure established by the distiller, they left the whiskey soaking in the charcoal from one to five days. Afterward, they analyzed samples by spiking them with known quantities of the odorants previously identified so they could quantify how much of each compound was removed by the LCP step.

Kerley says that based on the whiskey's smell before and after filtration, he was not surprised by the change in chemical composition, but he was surprised by how much some of the levels changed. "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," he says.

Now that Munafo and his student better understand how LCP changes whiskey chemically, they want to adjust some of the parameters of the filtration process. Munafo says they will run a series of experiments varying the time the unfiltered whiskey is in contact with the charcoal, and another in which the whiskey-to-charcoal ratio is systematically altered. He also wants to investigate the sensory impact of combinations of compounds that are present. "There are some 'strong' flavor compounds present in low concentrations, but then there are 'weaker' aroma-active compounds such as branched alcohols that are present at high concentrations," Munafo says. "Even though they might not be potent aroma-active compounds, they could have an effect like a perception of burning that our senses pick up."

Down the road, the data Munafo and his students collect could be used to advise distillers on exactly what changes to make to their to produce the best flavor for their unique brand. "We want to give them levers to pull so they are not blindly trying to get the target they want," Munafo says.

Explore further

Video: The chemistry of whiskey

More information: Changes in key odorants by the Lincoln County Process (Tennessee Whiskey), the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition.
Citation: Understanding what makes Tennessee whiskey unique (2019, March 31) retrieved 17 September 2019 from https://phys.org/news/2019-03-tennessee-whiskey-unique.html
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Mar 31, 2019
It's an old moonshiner trick to filter bad whiskey through activated charcoal to get rid of some of the off-flavors. Cheap vodka becomes slightly better by passing it through a common charcoal filter.

The difference between the spirits comes from the aging process: for vodka, you add water. For gin, you add spices. For whiskey, you put it in an oak barrel. For brandy, cognac, etc. you put it in a wine cask... etc. and you get the desired flavor from what you put in after the distillation. The dirty secret is that the best vodka, gin, whiskey, brandy etc. start off as just pure ethanol and water. Almost all of the other chemicals that pass through a bad still taste bad, peppery or like chemical solvents and soap. In some processes, the ethanol is made with industrial column stills that make very pure ethanol, and the fusel alcohols and oils are added in later for historical reasons, for that genuine rotgut flavor.

Mar 31, 2019
For my own persona; consumptiom, I prefer Rye Whiskey for the peppery aftertaste.
I do not like Bourbon style whiskeys because to me, those I've sampled have a gummy sweet aftertaste I dislike.

For products like vodka, my understanding is that it has to be filtered four or more times to remove the fusel oil taste.
Never really got into the other liquors. Icewine was interesting but I only sampled it once. Expensive as hell!

Applejack & Perry, no real opinion that I remember.

Mar 31, 2019
I generally prefer brandy, though I have had some pretty highbrow and expensive Scottish single malts.

My favorite brandy is an Armagnac that I was able to get a case of in the late 1990s. It's all gone now, but man, it was great stuff. Having had some very old Cognac I still consider the best Armagnac superior.

De gustibus non disputandum.

Mar 31, 2019
People turned off by traditional whiskey bitterness should try Tennessee brands like Jack Daniels. Gentler on the palate.

Mar 31, 2019
A lovely 55 degree perfectly clear evening with nice 12-year single-malt over an ice cube, top it off with a bong and a blintz. Tonight I am gonna be cantcomplain.

Mar 31, 2019
Oh, I'm not inveighing against whiskeys. I've had some of the smoothest of the Knockando, 50 years in the cask. And some really good Maker's Mark. But I still like brandies better. There are some really good alembic brandies from Napa and Sonoma, but still not as good as that armagnac.

Apr 01, 2019
People turned off by traditional whiskey bitterness should try Tennessee brands like Jack Daniels. Gentler on the palate.

Many consider Jack Daniels "footwash" becuse of the harsher tannins from the casks. Jack is only made in new barrels - the used barrels are sold over to Europe to make scotch, brandy, sherry... etc. which turn out much less woody and mellower after the casks have been washed out with bourbon.

On the other hand, Cognac and Armagnac are aged in fresh oak barrels from European trees, so the same effect happens there as well - the "best" spirits tend to be harsh until aged long enough that the tannins break down, while the second rate brands that recycle the used barrels come out smoother.

Apr 01, 2019
Interesting for those people who enjoy rockytop swill. I don't understand the appeal of a bad imitation of quality Kentucky bourbon!

Apr 01, 2019
Many consider Jack Daniels "footwash"

Love that!

Apr 01, 2019
From the Jack Daniels website:

All this precision and hands-on effort for a barrel we use once. Only new American White Oak barrels mature our whiskey. After the barrels are done imparting their flavor to our whiskey, we sell them to hot sauce makers, beer brewers, and Scotch whisky distillers who will reuse them several more times. And because these barrels were once home to our Tennessee Whiskey, we like to think we've done our part to help make these products just a little better.

Yes, and how.

The turpentine flavor is left with the Jack, so of course it makes the other spirits taste better!

Incidentally, this might be why the whiskey is filtered with charcoals before putting it in the cask: with a more traditional still, there's acetone and other lighter hydrocarbons towards the heads of the whiskey, and those tend to dissolve more tars and oils from the barrel, making for foul tasting whiskey. The charcoal absorbs them out.

Apr 01, 2019
How much of our persona; "taste/opinions/disagreements on this single subject?
Are shaped by personal experience? "Oh crap! I/m waking up in the drunk tank... Again!"

How much by stochastic biology? "I like a peppery aftertaste. I do not like a gummy sweet aftertaste."
Also, I got out of the habit of drinking red wines because my wife couldn't drink reds without raging headaches.
Did the tannin's really have a physiological affect or were there a psychological issues also? Or just habit?

By economics of what we can afford? Or to impress a date or employer?
By status & the need to display ranking in business or society?
By advertising & subliminal influence by celebrates?
Do you drink the same as your parents or did you rebel?

Save my comment & the next time you masochistically read an article of research in the Social Sciences or Psych?
With your usual kneejerk repulsion?
Think of how complicated this one subject is.

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