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Deeply Nerdy Stuff About Jack Daniel's Production - Charcoal, Souring, Fermentation

B6B63D48-56B5-4613-BA53-9DA2107BE960I just attended an amazing talk by Kevin Brent Smith (Micro-Biologist & Distillery Manager - Jack Daniel's Distillery). I wasn't planning on doing a blog post about it but I learned so much I wanted to write it down! 

Kevin B. Smith authored the chapter on "Yeast practices in the production of American whiskies" in The Alcohol Textbook.

First up, you may want to review my notes on my visit to the distillery from 2012 to see the production process in general and in order



  • According to Smith, if your fermentation doesn't finish and you still have sugars in your mash, these can burn and stick in your still, lending off  flavors to the final whiskey. 
  • Whiskey isn't made from grain, it's made from the seeds of grain. (not his point, but my observation)
  • When grinding grains before fermentation, the grinding process can release heat and damage the quality of the grain, but a hammer mill works well and doesn't have an impact. 


Souring In Two Places

  • "Souring" is not like sourdough starter in that the process' job is to remain consistency between batches. "Souring" means lowering the pH, making it more sour/acidic. "Sour mash"ing is adding backset (stillage) from the previous distillation run to the next one. The stillage contains lots of dead yeast that is food for the new yeast, but also it is acidic and lowers the pH from about 5.6 to 5.3. 
  • They use about 30% backset in each distillation. 
  • There is another place where they used soured mash, in the production of "lactic soured yeast mash." This is used in yeast propagation. 
  • Yeast is started from a lab-preserved copy, then propagated in several steps. It grows on a medium for the first couple of rounds, then it's transferred to a grain mash - the lactic soured yeast mash - to propagate further. 
  • In essence, lactic soured yeast mash is propagating yeast with lactic material (lactobacillus; not from the stillage) to lower the pH to about 5.0. 
  • Not all distilleries do this, but Smith says it's a traditional process. All Brown-Forman distilleries use lactic soured yeast mash. 
  • This lactic soured yeast mash will have flavor impacts on the whisky. 





Enzymes, Fermentation, and Rye Grain

  • Rather than, or in addition to, using malted barley (whose job in American whiskey is to provide enzymes that break down long chain carbohydrates into fermentable simpler sugars), commercial enzymes (not from the barley) can be added to whiskey. This has become common.
  • Jack Daniel's does not use commercial enzymes, and in fact most Brown-Forman whiskies do not. This is because commercial enzymes produce less maltose in the conversion process, which they feel leads to less flavor in the whiskey. 
  • (However they keep some enzymes around in case of emergencies, for if a batch of mash didn't convert all the way they could add some enzymes rather than trying to throw away a huge vat of basically sticky grain pudding.)
  • Rye as a grain is notoriously viscous/sticky and tends to gum up the process. At Jack Daniel's they do use a type of enzyme (different from the standard one for conversion) to help make it less sticky; but not to convert its starches into sugars. 
  • Another thing that helps rye not be so sticky is that it is added to the mash later in the process than the corn is. Corn is mashed at a hot temperature which is necessary for gelatinization, but if you leave rye with the hot water for very long it gets stickier. So it's added just before the malt is added at the end of the mashing process just before fermentation. You can see this on the graph below. 
  • After fermentation, their beer is at a pH of 4.6, while companies that don't use the soured yeast mash have a more acidic 4.0 beer.




Note that the next three charts are the same, with added information each time. 




  • Charcoal mellowing (aka the Lincoln Country Process) was needed in the olden days because distillers didn't have a good handle on consistent fermentation; charcoal filtration was needed to remove some off flavors in whiskey.
  • Running the newly-distilled spirit through charcoal is not a purely subtractive process, which is what I thought until today.
  • Sugar Maple trees are used to make the charcoal because it's an abundant but not terribly useful wood generally, and it doesn't impart much flavor. The wood is burned and then the fire put out. The larger pieces of charcoal are broken up and filled into vats. 
  • The charcoal production does not make activated charcoal. However the charcoal does do some adsorptive filtration of the whiskey to remove certain components. 
  • The additive quality of the charcoal is that minerals in the charcoal are extracted by the whiskey. The whiskey comes off the still at around 5.5 pH, and after charcoal filtration it goes up to a pH of 7.5 -  8.0!  So this has lowered the acidity of the whiskey substantially and probably adds to the perceived "mellowness" of the whiskey. FASCINATING. 
  • Why is this exciting? Because it makes me think about either running spirits/cocktails through a Brita to raise the pH for certain purposes, and or taking the direct route of "mellowing" spirits (or just de-acidifying them) by adding minerals to them.
  • (I've done lots of work on how the minerals in water affects how whiskey tastes, would be curious to try things with just minerals and whiskey.)
  • For example, most spirits are a bit acidic so if we filtered them or added minerals that will raise the pH. Butterfly pea flower tea usually starts out blue in water (neutral pH) but purpleish in spirits. If we want it to start out blue in spirits, maybe we just alter the pH first? 

Charcoal Practicalities

  • In olden days, the charcoal vats were used until the charcoal was no longer effective, as measured by taste. Then (I think in the 1980s-ish) they standardized it so that vats were used for 6 months then the charcoal was replaced. However in recent years they did chemical analysis and found that this was excessive, so now they use the charcoal for one year before replacing it. [When I last visited the distillery in 2012 it was 4-5 months.]
  • When the whiskey is poured over new charcoal it comes out watery (as the charcoal starts out wet) and they cannot use it until it comes out the bottom of the vat at the same 140 proof that it went in. Also, at the end of the year before they replace the charcoal they run water through it and the resulting water has lots of whiskey in it. So these watery "heads and tails" of the charcoal mellowing process are redistilled. [I'm not sure if the redistilled parts are used for whiskey or, more likely I'd guess, refined into neutral spirit for other products.] 
  • To make sure all the whiskey comes through the process tasting the same, their many different vats are spaced out in the freshness of their charcoal so that there is an average age of 6 months age on the charcoal being used, rather than having all whiskey from one vat change over time and be barrelled tasting different. 


Thanks to Jack Daniel's for a wonderfully nerdy session. 




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Suzanne Long

Thanks for writing this up - this was an amazing presentation and I'm so excited to have been there!

Larry Swindle

This is exactly why I like your blog BEST! Give us more information like this.
Well done. Excited about the possibilities for experimentation.

Camper English



Are you sure they distill up to 140 proof? That would be a pretty big revelation since everyone had always claimed JD is technically bourbon. But if they distill to higher proof than 125 they can't be.

Camper English

Bourbon can be distilled up to 160 proof, barrel entry proof is max 125. So it gets watered down after filtering before barrel entry.


That was awesome. Thanks so much for sharing. I'm a huge fan of JD because I'm so impressed by its consistency of product. I especially like their Single Barrel Rye - one of my faves.

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