The term “sour mash” on Michter’s US*1 Original Sour Mash Whiskey’s label refers to the process in which some of the fermented mash is held over from one batch of whiskey to start the fermentation on the next batch. A cost saving and consistency measure that is also said to make the whiskey sweeter and more complex, but also not uncommon, as majority whiskeys and bourbons are made using this process. Michter’s US*1 Original Sour Mash Whiskey is labeled a whiskey instead of a bourbon because according to the company, “the mashbill has a fair amount of rye grain in addition to a fair amount of corn and some barley malt.” This likely means the whiskey has less than 51% corn in its mashbill, the minimum required for it to be called bourbon. Michter’s US*1 Original Sour Mash Whiskey is also filtered.
