What Does "Sour Mash"� Mean?

People usually associate "sour mash" with a certain flavour or type of whisky. However, the actual meaning of "sour mash" is a process in the distillation industry for distilling some whiskeys.  

Mash, as we know is a fermented starchy blend from which alcohol and spirits are distilled. It is a concoction of grain, yeast and hot water. Sour mash is prepared by adding a part of the old mash to aid in fermenting each new batch in the same manner as a part of sourdough starter is added to each new batch of sourdough bread.

The "sour mash" is done to perk up the quality and consistency of the liquor in a manner which makes every bottle taste almost the same. Another beneficial part of the "sour mash" process is that it restricts the growth of harmful bacteria in the whiskey. Two of the popular forms of sour mash whiskey are Jim Beam and Jack Daniel's. The sour mash process was pioneered by the Scottish chemist Dr. James C. Crow, the Old Oscar Pepper Distillery in Woodford County, Kentucky.