What is Sour Mash?

Sour mash is a distillation process used in the production of some whiskey or bourbon whiskey. The term also is used to describe the mash used in this process — a combination of grain, yeast and water that has been removed from a batch of alcohol and allowed to ferment. This fermentation process grows healthy bacteria or fungi that prevent the growth of harmful bacteria. A sour mash whiskey is created when a new batch of whiskey is distilled using part of the fermented mash from a previous batch. Some whiskey fans contend that the highest quality spirits are made using the sour mash process, which results in a tangy, strong flavor.

Not all types of whiskey are made using the sour mash process. People who favor this type of whiskey say that using sour mash as an alcohol starter maintains a consistency of flavor in every batch produced. This can be desirable from an economic sense, because people are often brand conscious when it comes to hard alcohols and might want the same flavor each time they buy the same brand. In other forms of alcohol, such as wine, flavor changes are expected from one batch to another. Some people do not care for this unpredictability and want their whiskey to taste the same every time.

The principles behind the use of sour mash to make whiskey are the same as the reason why a sourdough starter can be used to make bread. A sourdough starter, also called the chef or mother dough, is a combination of fermented mixed yeast, flour and water that have been saved from an old batch of dough and is used to make dough for a new batch of bread. The new dough is mixed in with the starter, and another starter is preserved for the next batch. This can keep going from one batch to the next, and sourdough starters can last for years. The fermentation process involved in keeping a sourdough starer active often causes the bread to have a consistent fine sour taste that many people enjoy.

The origin of the sour mash process for making whiskey is not clear. Most people believe that it was invented in the early 1800s at Old Oscar Pepper Distillery in Frankfort, Kentucky. Many people credit Dr. James C. Crow with the invention of the process, but other people give the credit to Dr. Jason S. Amburgey. Both men worked at Old Oscar Pepper Distillery.