By Sarah E Coleman
As all bourbon aficionados know, this tasty libation requires one very specific ingredient: corn. The Federal Tax and Trade Bureau, which defines and regulates all spirits, has only one grain stipulation for bourbon: it must contain least 51 percent corn. This opens up a realm of creativity and interpretation to what the other grains can be. Most distillers have traditionally used rye as the secondary grain and most distillers also use malted barley to help with fermentation, but neither of these grains are required to make bourbon.
Though distilleries must use at least 51 percent corn to create true, U.S. “bourbon,” the remaining ingredients can be left to the imagination.
All Bourbons Are Not Created Equal
American bourbon distilleries all use similar equipment to produce bourbon, and 98 percent of the world’s bourbon is produced in Kentucky, in the same climate. While these factors would, in theory, create a recipe for cookie-cutter bourbons, the exact opposite is actually true. As distilleries have at least 49 percent wiggle room with the grains in their bourbon, there is plenty of room for creativity and interpretation.
Many distilleries use the following grains to create a unique taste:
Corn: This grain gives bourbon its sweetness and provides the highest yield of alcohol per bushel. Though very prevalent-tasting in the “White Dog” phase of bourbon making (fresh from the still), the taste mellows over years of aging.
Rye: Rye brings about a spicy note to bourbon, including tastes such as pepper, clove, cinnamon and nutmeg. Rye provides bourbon with the “bite” it is famous for.
Barley: Barley produces enzymes that convert starch to sugar during the fermenting process. Though barley does produce some flavor (mainly malt and chocolate notes), it is mainly used as the workhorse in the bourbon-making process.
Wheat: Wheat has a much milder flavor than rye, allowing the sweetness of the corn to come through in the final bourbon product.
Some more unusual grains that are used in various bourbon distilleries across the U.S. include brown rice, soft red wheat, rolled oats, millet, quinoa and buckwheat.
Distillers are very particular about the quality of corn that is used to create bourbon, as it has such a heavy influence on the taste of the final product. Most of the corn used in Kentucky distilleries is sourced from farms in Kentucky and Indiana that have had relationships with the distilleries for many years.
Shipped to the distilleries in tractor trailers, each load of grain undergoes a series of evaluations, including a visual inspection for any abnormalities. The grain is then weighed to ensure that it adheres to baseline characteristics approved by the distillery. Finally, a sample is tested in the distillery’s laboratory to ensure that moisture standards and chemical balances are met.
Do the Mash
Once the grains are found to be satisfactory, they are milled into fine powder before being cooked to form a mash. Distillers have varying preferences for how the mill their grains, as even this small detail will affect the flavor of the bourbon; some distilleries press the grains with a hammer mill, while others pulverize them in the husk; still other distilleries choose a roller mill.
Distilleries that press their grains from the husk use a heavy roller, discarding the husk and retaining the grain. Pulverizing the grains smashes them in their husks, then the mix of husks and grains are used in the mash, which can create a more-bitter taste. The result, regardless of the chosen method, are grains that have been transformed into a fine powder that is ready to be cooked. All grains are stored separately.
Cooking is the next step in the bourbon-making process. To begin, the first grain is portioned out according to the distillery’s recipe. Water is then added. Geographically, Kentucky sits atop a massive limestone layer that readily filters impurities from the water. Many distilleries use spring water that is sourced from areas where the limestone layer is broken and water bubbles up. Distilleries located in more-industrial areas will use the local water supply, but will demineralize or deionize the water to purify it.
This grain and water mixture (now called mash) is then placed in a cooker, where it is exposed to high heat for a varying amount of time, depending on the grains involved and the distilleries’ individual bourbon recipe. Corn is typically the first ingredient to be cooked, and at the highest temperature. It is then cooled, followed by rye, barley and any other grains (if the distillery chooses) are added in. The mixture of grains used in creating each distinct bourbon is referenced on the “mash bill.” Pumps circulate the cooking mixture, making sure all the grains are cooked evenly. It’s of utmost importance that the grains are not overcooked, as this can break down their proteins and caramelize the sugars, resulting in a bitter taste.
Bourbon and the Yeast
Once finished cooking, the mash is then moved to a fermenter, where yeast is added. Yeast is integral to the bourbon-making process. Each distillery has their own particular yeast strain, some of which are tightly kept secrets so as to set a particular bourbon apart from its peers. During fermentation, which typically takes three to five days, the yeast converts the sugar in the mash into alcohol, carbon dioxide, and heat.
At this point in the bourbon-making process, distillation residue, called by a few different terms “stillage,” “backset,” or “sour mash” (which is formed at a later stage in the bourbon-making process), is added from previous bourbon batches. This added stillage is part of the sour-mash process for which American distilleries are famous. At the end of the fermentation process, the mash has become what is called a “distiller’s beer” and is about 12 to 15 percent alcohol.
Many American distilleries utilize column stills for distillation, which allows for a continuous distillation process. (Some distilleries use pot stills or combination pot and column stills.) A column still is a vertical tube that is sectioned off using metal plates. The column is filled with the distiller’s beer from the fermenter and the bottom plates are heated. As the still heats up, alcohol vapors will rise through the column to the top while water, with the remnants of the grain particles will gather at the bottom (alcohol has a lower boiling point than water). This accumulation at the bottom of the column is called “stillage”; some of this is saved to be added to the fermenters of future batches and continues the cycle of the “sour mash” process.
At the top of the column, the alcohol vapors are cooled and then re-condensed back into liquid form. Typically, the liquid is distilled a second time through a copper pot still, called a doubler.
After the vapor goes through the condenser, where it liquefies and becomes raw whiskey, also called “white dog,” “moonshine” or “white lightening.” The first portion of this distillate that comes out of the still is known as the “heads” and the last part is known as the “tails.” In between the beginning and the end of the distillate is known as the “hearts,” the portion sought after by the distillers. Bourbon can be distilled at no more than 160 proof.
From here, the whiskey goes into new, charred white-oak barrels at no more than 125 proof to await its transformation into bourbon. The liquid gains both color and flavor from the caramelized sugars in the charred wood of the barrel.
In order to be called Bourbon, the product does not have to age for any certain time period. It could be aged for just one day, though it would likely not taste very good. To be labeled “straight” it must be aged for a minimum of 2 years. Any bourbon aged less than 4 years must be denoted with an age label.
Though the process of making bourbon may not seem overly complicated, it is heavily regulated by the Federal Standards of Identity for Distilled Spirits. This entity states that bourbon made for U.S. consumption must adhere to the following guidelines:
-Bourbon must be made in the United States; it is declared by Congress to be “America’s Native Spirit”
-Bourbon must have a mash bill of at least 51 percent corn
-Bourbon must be aged in new, charred, oak barrels
-Bourbon must be distilled at less than 160 proof and enter into the barrel at below 125 proof
-Bourbon can have no artificial coloring or flavoring added
-Bourbon must be bottled at 80 proof or more (40 percent alcohol by volume)
While all bourbons must follow these guidelines, many distilleries take creative liberties with their libation, using unique grain mixes to create unusual, delicious concoctions.
An Argument Over Origin
The history surrounding bourbon’s origin is a bit murky; some argue that it came from Bourbon Street in New Orleans, where bourbon was shipped down the Ohio and Mississippi Rivers for trade. Others (and don’t argue with a Kentuckian about this!) say it originated in Bourbon County, Ky.
Elijah Craig, a Baptist minister, is often credited as being the “inventor” of bourbon, aging corn whiskey in oak barrels that had been charred in a fire in 1789. Sadly, there are few historical facts to actually support this story; there were corn whiskey distilleries in Kentucky before 1789. Refutable for not, Craig came to lasting fame: Heaven Hill Distillery has two bourbons labeled with his moniker, Elijah Craig 18-Year-Old Single Barrel and Elijah Craig 20-Year-Old Single Barrel.
A combination of the two trains of thought converge in this theory: Distillers in Kentucky used to bottle their bourbon as “white dog” that was not aged and was clear. When shipping their product by boat to New Orleans, they had to wait for warmer months when there was no ice on the Ohio River. The bourbon sat in barrels for many months between waiting for clear rivers and the 3-month trek down the river, allowing it to age and absorb the sugars from the charred barrels. Kentucky distillers didn’t realize that their “white dog” had turned color until they opened the barrels in New Orleans. People began asking for the libation by name, calling it the “Bourbon Street Whiskey” then, shortened to “Bourbon.”
Happy Cows Live
Distillation residue, called stillage, accumulates at the bottom of the stills during the distillation phase of bourbon making. Though some of the stillage is processed into the sour mash that is reintroduced into the product at the fermentation stage, the rest of it is simply a byproduct.
In an effort to make this stillage useful, distilleries remove the accumulated water, fibers, and proteins that collect at the bottom of the still. The water is removed from the collected matter in large drums using steam. The solids are then taken out and given to farmers to use as a livestock feedstuff that is high in protein, fat, and trace elements.
The amount of stillage left over is nothing to sneeze at: it’s estimated that Kentucky distilleries alone gave away about $2.5 million worth of spent grains in 2014—enough feed 90,000 head of cattle per year.
A Kentucky transplant, Sarah Coleman got to the Bluegrass as quickly as she could, drawn by the equine industry and all that it entails. She has since become an avid fan of both bourbon and basketball.