The Difference Between Bourbon Whiskey & Sour Mash

Updated February 21, 2017

As any whiskey maker will tell you, all bourbon is whiskey but not all whiskey is bourbon. And all sour mash is bourbon whiskey but not all bourbon is sour mash. These two refined types of whiskey are uniquely American spirits, descended from moonshine and produced primarily in the territories of the Old Dominion, now called Kentucky and Tennessee. Connoisseurs will argue over which process is superior and whether single-barrel or small-batch whiskey is better, but all will agree that bourbon and sour mash whiskeys are fine additions to the distiller's craft.


Bourbon whiskey is made in the United States, nearly all of it in Kentucky and Tennessee. Traditional methods use water from limestone springs and oak for barrels, both of which are abundant in these states.


Bourbon whiskey had its beginnings in territorial Kentucky in a county named for the Bourbons, the ruling family of France, the new nation's ally in the Revolutionary War. Farmers used leftover silage corn instead of wheat or rye, the customary grain used for mash. When the Whiskey Rebellion of 1791 took a toll on distillers in other western states, the distillers in the Blue Ridge Mountains of Kentucky and Tennessee were able to hide from the revenue agents successfully enough to build a thriving, unregulated industry. The moonshine whiskey that these mountain folk produced evolved into the refined whiskeys called bourbon and sour mash.


Bourbon's unique character comes from the 51 to 79 per cent corn in its recipe. The addition of water to crushed or rolled grain begins the fermentation process, and the fermented mash is distilled to produce a spirit that is no more than 80 per cent alcohol by volume. Bourbon may be double-distilled and aged at least two years in charred oak barrels. The result is a mellow, woody blend of flavours that may be bottled straight out of a single barrel or blended from a number of barrels in a small batch. Sour mash whiskey uses the bourbon recipe but starts the mash with leftovers from a previous batch, much like the starter in sourdough bread. The sour mash process gives a sweeter, deeper flavour to the final product. The alcohol by volume content of bourbon and sour mash is adjusted to between 40 and 50 per cent (80 to 100 proof) at bottling time.


The name "bourbon" has been legally controlled only since 1964, so makers exist in other counties. However, only bourbon made in Kentucky may use the name of the state on the label. Tennessee whiskey uses the bourbon recipe, but the distilled spirits are filtered through maple charcoal, adding a different overtone to the flavours. Makers will specify "sour mash" on the label if that process is used. Several societies are devoted to the study of these American spirits, and tours of distilleries are popular in the hill country of Tennessee and Kentucky.


Well-made bourbon (Kentucky, Tennessee whiskey or sour mash) is a rich, sweet whiskey better tasted straight and in moderation, hence the name "sippin' whiskey." As with any distilled spirits or other alcohol-containing drinks, overconsumption can lead to sensory impairment and damage to organs.

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About the Author

An avid perennial gardener and old house owner, Laura Reynolds has had careers in teaching and juvenile justice. A retired municipal judgem Reynolds holds a degree in communications from Northern Illinois University. Her six children and stepchildren served as subjects of editorials during her tenure as a local newspaper editor.