GEOCHEMICAL AND PHYSIOGRAPHIC INFLUENCE ON THE LOCATION OF KENTUCKY BOURBON AND TENNESSEE WHISKEY DISTILLERIES

The locations of Kentucky bourbon and Tennessee whiskey distilleries in the pre-industrial era appear to be constrained by the geochemistry of natural waters, stratigraphy, geomorphology, and the average ambient temperatures of fermentation. Bourbon and Tennessee whiskey are made from primarily corn sour mash. To efficiently make whiskey from corn requires mash water to have dissolved iron content lower than 25 ppm, circumneutral pH, and cool temperature so that amylase enzymes that convert starch from corn into fermentable sugar are not denatured. Shallow groundwater and streams in these regions typically have dilute, Ca-Mg-bicarbonate-type compositions with circumneutral pH, which limits dissolved Fe and also promotes growth of bacteria involved in fermentation. These specific chemical characteristics would have been difficult to manipulate in pre-industrial, rural America and are a consequence of locations on the Ordovician and Mississippian bedrock of the Cincinnati Arch, specifically the Highland Rim physiographic region of the Nashville Dome and the Knobs and Inner Bluegrass physiographic regions of the Lexington Dome. The locations of pre-industrial distillery locations within these physiographic regions have similarities in topographic relief and hydrology. Annual average groundwater temperatures (~ 13 to 16°C) in both regions are beneficial for fermentation for whiskey using the sour mashing method. The question of why most American whiskey distilleries are confined to a small region of Kentucky and Tennessee, and not other areas of the southern U.S. with suitable climates for whiskey feedstock production, will be discussed.