Bourbon: it’s as American as apple pie, with a history and production process as complex as its flavor profile. By law, bourbon is a distinctly American whiskey, and its defining characteristic is the use of corn.
So, what exactly is bourbon made of, and how does its creation differ from other whiskeys? That’s what we’re here to explore, from grain to bottle.
In this article, we’ll break down the specific ingredients that qualify a spirit as bourbon, the precise steps involved in its creation, and the legal requirements that bourbon distillers must follow.
Whiskey and bourbon: What’s the difference?
To understand what bourbon is made of, it helps to understand the broader category of distilled spirits called whiskey.
What is whiskey?
Whiskey is a distilled spirit made from fermented grain mash. To be considered whiskey, the spirit must have a minimum alcohol by volume (ABV) of 40%. Different grains and production methods are used around the world to make a wide variety of whiskeys.
You’ve probably heard of Scotch, Irish whiskey, rye, and Tennessee whiskey. There’s a lot of diversity within the whiskey category.
What is bourbon?
Bourbon is a specific type of American whiskey with a historical connection to Bourbon County, Kentucky. There are legal requirements that define what can be called bourbon.
To be labeled as bourbon, the whiskey must be:
- Made in the United States
- Made from a mash bill of at least 51% corn
- Aged in new, charred oak barrels
The Mash Bill: The Heart of Bourbon’s Flavor
The flavor of bourbon comes down to something called the “mash bill,” which is the recipe of grains used to make the spirit.
The Role of Corn
By law, bourbon has to be made from a grain mixture that’s at least 51% corn. Corn gives bourbon its distinctive sweetness. Some distilleries use a much higher percentage of corn, as much as 70% to 90%. A high-corn mash bill translates into a sweeter, less spicy bourbon.
Complementary Grains: Rye, Wheat, and Malted Barley
Besides corn, bourbon mash bills typically include rye, wheat, and malted barley.
Rye adds spice and complexity to the bourbon. A bourbon with a high percentage of rye will have a bolder, spicier flavor profile than one with less rye.
Wheat is used to create a softer, smoother bourbon. “Wheated” bourbons are often described as having a more mellow and approachable flavor compared to those made with rye.
Malted barley plays a crucial role in the fermentation process. It contains enzymes that convert the starches in the corn, rye, or wheat into fermentable sugars, which the yeast then turns into alcohol.
The Bourbon Production Process: From Grain to Barrel
So, you know what bourbon is made of, but how does it actually become bourbon? The process, while seemingly straightforward, is steeped in tradition and precision.
Step One: Grain Preparation and Mashing
First, the carefully selected grains—the corn, rye, wheat, and/or barley—are ground into a coarse meal called grain grist. Think of it as a rough, grainy flour. This grist then heads to the mash tub.
Mashing is where the magic starts. The grain grist is mixed with water and heated. The temperature is carefully controlled, usually ranging from 150 to 220 degrees Fahrenheit. This cooking process is crucial because it converts the starches in the grains into sugars. Those sugars are what the yeast will later feast on to create alcohol.
Step Two: Fermentation
Next comes fermentation. Yeast is added to the mash, now a sweet, watery mixture. Water quality is paramount here; many distilleries swear by limestone water, believing it contributes to the yeast’s health and the bourbon’s overall character.
The yeast happily consumes the sugars, turning them into alcohol and carbon dioxide. Distillers often use cultivated yeast strains, carefully chosen for their specific flavor profiles. This is where the “sour mash” technique comes in. Sour mash involves adding some of the spent mash from a previous batch to the new mash. This seemingly odd practice helps control bacteria and acidity, ensuring consistency from batch to batch. It’s like a sourdough starter for bourbon!
Step Three: Distillation
Distillation is the process of separating the alcohol from the water in the fermented mash. The mash is heated, and because alcohol has a lower boiling point than water, it evaporates first. The vapor is then collected and cooled, condensing it back into a liquid—now with a much higher alcohol content.
Bourbon distilleries typically use column stills, pot stills, or a combination of both. Column stills allow for continuous distillation, making the process more efficient. Copper pot stills, on the other hand, are sometimes used for a second distillation to further refine the spirit and impart specific flavors.
The resulting liquid is often called “white dog” or “new make.” It’s a high-proof spirit, clear as water, and lacking the color and much of the flavor we associate with bourbon.
Step Four: Aging
This is where bourbon truly becomes bourbon. The “white dog” is transferred to new, charred oak barrels. The use of new barrels is a legal requirement for bourbon, and the charring is essential. As the bourbon ages, it interacts with the wood, extracting flavors, colors, and aromas. The minimum aging time for “straight bourbon” is two years, but many bourbons are aged much longer.
During aging, some of the alcohol evaporates—this is known as the “angel’s share.” While it reduces the overall volume of the bourbon, it also concentrates the flavors and aromas, contributing to its complexity.
Step Five: Bottling
Finally, the aged bourbon is ready for bottling. The barrels are dumped, and the bourbon is filtered to remove any remaining solids. Then, it’s typically “proofed down” with water to reach the desired bottling proof. Different bottling proofs can significantly impact the flavor profile of the bourbon, with higher proofs generally offering a bolder, more intense experience.
Variations in Bourbon: Mash Bills, Aging, and More
While all bourbon shares a foundational recipe, distilleries play with variations in mash bills, aging techniques, and bottling processes to create unique flavor profiles.
Mash Bill Variations
The exact percentages of corn, rye, wheat, and barley used in a mash bill significantly impact the final taste. For example, a “high-rye” bourbon, like those from Bulleit or Old Grand-Dad, will have a spicier, bolder character. Wheated bourbons, such as Maker’s Mark and Larceny, are known for their softer, sweeter flavor.
Aging Techniques
The level of char inside the new, charred oak barrels also influences the bourbon. Heavily charred barrels impart more color, vanilla, and caramel notes. Even where the barrels are stored in the warehouse affects the aging process. Higher floors experience greater temperature swings, leading to more interaction between the bourbon and the wood.
Bottled-in-Bond and Single Barrel Bourbons
Bottled-in-bond bourbon must adhere to specific standards: it must be the product of a single distilling season, made at one distillery, aged for at least four years in a government-bonded warehouse, and bottled at 100 proof.
Single barrel bourbon comes from one individual barrel, offering a unique flavor profile that varies from barrel to barrel. Some bourbons also undergo secondary finishing in different types of barrels (e.g., sherry or port barrels) to add extra layers of complexity.
The Bottom Line
Bourbon is a uniquely American spirit, crafted with careful attention to detail. At its heart are a few key ingredients: corn, which must make up at least 51% of the mash bill, along with other grains like rye, wheat, and malted barley. The fermentation and distillation processes are crucial, but it’s the aging in new, charred oak barrels that truly defines bourbon’s character.
Making bourbon is an art as much as a science. The master distiller plays a pivotal role, overseeing every step to ensure the final product meets their exacting standards. They are the guardians of tradition, blending expertise with intuition to create a spirit that is both complex and satisfying.
So, raise a glass and explore the diverse world of bourbon. Experiment with different brands and mash bills to discover your personal preferences. Appreciate the craftsmanship and dedication that goes into every bottle. Cheers!