Sour mash is a distillation process used in the production of whiskey and bourbon, and normally credited as the invention of Dr. James C. Crow. He may have designed the process in the 1820s and 1830s while working at the Old Oscar Pepper Distillery in Kentucky. Others credit the invention to Dr. Jason S. Amburgey, also an employee of the Old Oscar Pepper Distillery. Today, recognizable forms of whiskey that include sour mash include brands like Jack Daniels® and Jim Beam®.

If you understand how to use a chef or sourdough starter to make bread, then you can understand the principles behind the use of sour mash. Sourdough starter or a chef is fermented mixed yeast, flour, and water that are used with each new batch of bread. Some of the new bread is mixed in with the starter to keep it going, and sourdough starters can last for years. Because of the fermentation process involved in keeping a chef active, the bread often has a fine sour taste that many people enjoy.

In the making of bourbon or whisky, sour mash is a combination of the grain, brewer’s yeast, and water, which is removed from a batch of alcohol and allowed to ferment. Generally this fermentation process, as with a sourdough starter, grows healthy bacteria or fungi that prevents the growth of harmful bacteria. When a new batch of whiskey or bourbon is distilled, part of the fermented mash is added to the new batch. To keep the sour mash going, some of the newly made mash is added back to the fermented mash.

Bourbon and whisky fans may contend that the more superior spirits are made using the fermented grains process. Newer drinkers or those not expert in this field may think of sour mash only as a flavor. It is not in fact a flavor, but a process for making alcohol which results in a tangy, strong flavor to the resultant spirit. You generally can’t get that distinct flavor without employing sour mash while making alcohol.

Sour mash isn’t present in all forms of whiskey, only some. Those who favor it say that employing this alcohol starter maintains a consistency of flavor in every batch produced. This can be desirable from an economic sense, since people are often brand conscious when it comes to hard alcohols and may want the same flavor each time they buy the same brand. In other forms of alcohol like wine, flavor changes are expected; wine is unpredictable. Many don’t care for this unpredictability and want their Jack Daniels® to taste like Jack Daniels® every time.