What Is Sour Mash Whiskey?

A bottle of Jack Daniels Sour Mash whiskey next to a candle

The whiskey making process has changed quite a bit over the years with the majority of whiskey experimentation taking place in the United States. This is because colonialists were forced to use different ingredients and processes to obtain a dram they were satisfied with.

One of the most exciting innovations to come from American whiskey makers is Sour Mash Whiskey. Sour mash is a whiskey-making technique that makes the whiskey production process more reliable and improves the quality of the spirits being produced. In this post, I’ll share everything you need to know about Sour Mash Whiskey.

What Is Sour Mash?

To understand how and why sour mash is used, it helps to know how whiskey is produced. Although making whiskey is a fairly simple process, it does involve several few steps:

  1. Malting (Optional) and milling – If you are making a malted whiskey, the first step involves soaking grains in water so they germinate — a process known as malting. This process changes the chemical structure of the grain. Once the grain is germinated, it is dried. The grain is then milled into a powder to prepare it for mashing.
  2. Mashing – Mashing consists of adding water to the grain and agitating it. The goal is to release the starches from the grains so they can be broken down into sugars. The solution produced by mashing is called a wort.
  3. Fermentation  – Bacteria is added to the wort to turn the sugars into alcohol. After this stage the the solution is called a wash.
  4. Distillation – The wash is placed into a copper still and distilled into a very strong spirit. Most distilleries will distill their whiskeys two or three times to produce a more refined product.
  5. Ageing – Finally, the solution is placed into an oak barrel to age for several years. During this time, the chemical compounds in the whiskey change dramatically and the alcohol content is reduced.

If a whiskey uses the Sour Mash process, some of the spent mash from a previous batch of whiskey to the new mash. This old mash consists of fermented and distilled mash with dead yeast in it.

The sour mash process is very useful to distillers because it gives them more control over the pH of their mash. If the pH of the mash gets too high (basic), it will cause unwanted bacteria to grow, which will ruin the flavour of the whiskey. The sour mash, with a pH of around 5.0 to 5.4, helps to keep the mash acidic, avoiding this problem.

Most American distilleries will use a 1 to 3 or a 1 to 4 ratio of sour mash to new mash. It’s also common for distilleries to let their mash sit for a few days to let the sour mash really work its magic.

Almost all Tennessee whiskey distilleries and American bourbon makers use the sour mash process as it helps them reliably produce a great-tasting whiskey. However, only a handful of distilleries market their whiskey as being “sour mash”.

Where did sour mash whiskey come from?

For many years, James C. “Jim” Crow was credited as creating the sour mash process. He was a doctor who moved to Kentucky in 1823 where he began working in a distillery.

However, the Kentucky Historical Society has found a recipe for sour mash whiskey that dates back to 1818. The recipe was written by Catherine Carpenter of Casey County. It is as follows:

“Out into the mash tub six bushels of very hot slop then put in one bushel of corn meal ground pretty course. Stir well then sprinkle a little meal over the mash. Let it stand 5 days, that is 3 full days betwist the day you mash and the day you cool off – on the fifth day put in 3 gallons of warm water then one gallon of rye meal and one gallon of malt. Work it well into the mash and stir 3 quarters of an hour then fill the tub half full of luke warm water. Stir it well and with a fine sieve or otherwise break all of the lumps fine then let stand for three hours then fill up the tub with luke warm water.”

Thanks to Catherine’s inventiveness, we get to enjoy American whiskeys that are reliably delicious!