We are blessed to have all four seasons here in Kentucky, but make no mistake… Kentucky’s natural resources are the No. 1 reason the state makes the best (and the most) bourbon in the world. There are more barrels of bourbon aging in Kentucky than there are residents—two barrels for every resident, in fact—and 95% of all bourbon is produced here.
Making a good bourbon requires corn, water, wood and the right climate. Kentucky has all four.
“Only the Bluegrass state has the perfect natural mix of climate, conditions and pure limestone water necessary for producing the world’s greatest bourbon,” says the Kentucky Distillers Association (KDA).
Corn
By law, bourbon must be at least 51% corn. Distilleries are the number one purchaser of corn, to the tune of 40%, according to the KDA.
There is a difference between the corn people consume and the corn used in bourbon. The corn we eat is in the milk phase, where the kernels are soft and the stalks are green. Bourbon corn is fully matured with dry kernels and brown stalks.
Many types of corn are used in bourbon, each with its own flavor profile, similar to grapes in wine. Some have a sweeter taste and others may have a spice profile.
The quality of the corn used can make or break a bourbon. It can be just as much of a source of flavor as other parts of the bourbon-making process.
For example, the Jeptha Creed Distillery in Shelbyville, Ky., used an heirloom variety of corn called Bloody Butcher for a batch of experimental bourbon.
“The corn has a distinctive taste with notes of vanilla and toasted pecans that shines through in its bourbon,” the distillery explained.
Water
Kentucky has more miles of running water than any other state, except Alaska, according to the Kentucky Department of Tourism.
Water is a vital ingredient in bourbon. And Kentucky distillers have long said the commonwealth’s unique limestone water distinguishes Kentucky bourbon from its competitors.
What is limestone water? It is commonly referred to as “hard water,” with high dissolved mineral concentrations. It forms when water percolates through limestone deposits.
The distillery’s allegiance to limestone water is deserved: The water has a higher pH level, which promotes fermentation. The limestone adds minerals and filters out impurities that can affect taste. Water is used in every part of making bourbon.
Maker’s Mark founder Bill Samuels Sr. specifically chose the company’s distillery site—later renamed Star Hill Farm—because of its limestone-filtered, 10-acre lake. Many distilleries do not have the luxury of having a lake or stream beside them. Old Forester uses Louisville city water which is treated by reverse osmosis before it is used.
Louisville Water has more than a dozen distillers as customers. President and CEO Spencer Bruce has said that the city water’s “great taste supports the flavor whether it’s a drop of water or a rock in the drink.”
Wood
All bourbon must be aged in new, charred oak barrels. The distinctive white oak is preferred by most distillers because of its filtering qualities, taste, color enhancement, and stability.
The white oak tree is not without its lore. Combined with other oak lumber, the Navy warship the USS Constitution, aka Old Ironsides, was built using white oak.
White oak goes through a very important and specific process before becoming a bourbon barrel. The oak must be dried, then toasted and charred. Some say that without white oak barrels, bourbon would never be as popular as it is now.
White oak filters sulfur compounds that give the bourbon its distinctive taste. The inside char allows the bourbon to penetrate the wood’s pores to retain flavor. While the flavor can be enhanced by other ingredients, the aging of the bourbon is enhanced by the oak. The profiles of vanilla, caramel and coconut come from the charred oak barrel.
Distilleries sometimes add oak chips, which alter the aging process. The oak tannins speed up the maturation along with oxygen.
With the popularity of bourbon growing worldwide, the white oak tree is in high demand and needs to be protected. Many distilleries have set aside land to grow and improve the numbers of the white oak tree.
The White Oak Initiative—whiteoakinitiative.org—was created in the fall of 2017 to protect valuable natural resources. Members of the White Oak Initiative include distillers, federal and state agency representatives, conservancy organizations, and traditional wood-use companies.
Brown-Forman, maker of Woodford Reserve and other fine bourbons, partnered with the White Oak Initiative. Brown-Forman also pledged to purchase 50% of its logs from sustainably managed forests by 2035.
Climate
Climate has always been important when producing bourbon. Kentucky enjoys all four seasons, but like the fairytale “Goldilocks and the Three Bears,” we tend to side with Baby Bear, who prefers everything is “just right.” Everything is just right to help the bourbon aging process.
The summer heat causes the whiskey to evaporate, which the industry calls called the “Angel’s Share,” pushing the bourbon into the wood during the day. The cool of the night air brings the liquid back out of the barrel with flavors in tow. This process is called the “aging cycle.”
As distilleries have grown, they noticed that warehouse design had an effect on the bourbon-making process. “Microclimates,” or multi-storied warehouses, were built. Bourbon that is stored higher has a higher proof; the lower you descend, the lower the proof of the bourbon. Temperatures can vary up to 30 degrees from top to bottom.
As Angel’s Envy puts it, Kentucky’s climate is “the engine that drives bourbon’s flavor.”
Climate affects all facets of the bourbon-making process: corn production, wood supply, aging and flavor. A year’s worth of aging in Kentucky is different than anywhere else.
“Too much of anything is bad, but too much good whiskey is barely enough.” – Mark Twain
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