How Bourbon Is Made: Inside the Bourbon Production Process

Bourbon is a type of whiskey made from a mix of fermented grains (typically, corn, barley, and rye). In America, bourbon whiskey has a few legal requirements surrounding the mash bill, barreling, additives, and alcohol content. The mash must contain at least 51 percent corn; the spirit must be aged in newly charred white oak barrels, making for a typically nutty flavor profile and a mellow, caramelized sweetness. The mahogany-colored whiskey variation must also have a minimum of 40 percent [alcohol by volume](https://www.masterclass.com/articles/learn-about-alcohol-content-in-wine-highest-to-lowest-abv-wines) (ABV) and cannot contain flavorings or any other additives. Popular cocktails featuring bourbon include the Mint Julep, the [Manhattan](https://www.masterclass.com/articles/the-classic-manhattan-cocktail-recipe), the Old Fashioned, Bourbon Eggnog, [Whiskey Sour](https://www.masterclass.com/articles/how-to-make-a-whiskey-sour), the Libertine, and the [Paper Plane](https://www.masterclass.com/articles/how-to-make-a-paper-plane-cocktail). Since the eighteenth century, the Bourbon has been distilled throughout the United States; however, it’s mainly associated with the American South, specifically Kentucky. Nine bourbon distilleries are located in Bourbon County, Kentucky, specifically to take advantage of the rich concentration of hard water (sometimes referred to as limestone waters) in the region. This prized water has a high mineral content that bonds with the alcohol’s carbohydrates during fermentation to create the spirit’s signature smoothness. The name “bourbon” is commonly considered a nod to Bourbon County, Kentucky, where an estimated 95 percent of all bourbon is produced. However, some origin stories suggest it refers to Bourbon Street in New Orleans, Louisiana, which is named for the House of Bourbon, a French dynasty that dates back to the thirteenth century. Bourbon is distinct from other types of whiskeys based on the way it is aged and manufactured. Here is the process for making bourbon: 1. __Determine the mash bill__. The master distiller first determines the recipe (or mash bill) of different grains to use for the bourbon’s creation. The American Bourbon Association requires that bourbon sold in the United States is distilled from a mixture of grains (or mash) that must be comprised of at least 51 percent corn. The remainder of smaller grains is malted barley, wheat, or rye. 2. __Combine the base ingredients__. To make a fermentable base, distillers will mix grains—corn, rye, and barley malt—with water and yeast. They then heat and stir the mixture (sometimes called “bourbon mash”) to ensure it’s well combined and ready to ferment. 3. __Ferment__. For the fermentation process, bourbon makers store their base mixture in a vat for a specified amount of time—from one to two weeks—to fully ferment the mixture. During this step, the compounds begin to break down and produce a simple, natural alcohol called ethanol or ethyl alcohol. [Yeast](https://www.masterclass.com/articles/fresh-yeast-explained) and sour mash are added to the mixture at this point. Sour mash is the leftover mash from a previous distillation, which reduces the mash’s pH to prevent bacteria growth. 4. __Strain the mixture__. Once fermentation is complete, distillers strain off the liquid from the fermented solids. They’ll discard the solids and use the liquid (ethanol) to make the bourbon. 5. __Distill__. Distillation is a process that purifies a liquid by heating and vaporizing it, then collecting the vapor as it recondenses into a liquid. The resulting liquid (distillate) is considered purer (since it leaves behind many impurities when it evaporates) and more alcoholic. A majority of bourbon is put through the distilling process twice. The first round involves distillation in a beer still. The second round involves distillation in heated copper pot stills, referred to as doublers or thumpers. These rounds serve to boost the alcohol content and remove impurities. 6. __Aging and barreling__. Once the bourbon reaches between 80 and 125 <a href='https://masterclass.com/articles/baking-101-what-is-proofing-learn-how-to-proof-breads-and-other-baked-goods' target='_blank' class='mc-text--link' data-mc-segment-trigger='true' data-mc-segment-event-type='Article Page Click' data-event-obj='{"textTag":"p","href":"https://masterclass.com/articles/baking-101-what-is-proofing-learn-how-to-proof-breads-and-other-baked-goods","linkCopy":"proof","category":"automated-link"}' automatic='true'>proof , distillers must age it in a new charred oak barrel for at least two years before it can be called straight bourbon. (The aging process is shorter than that of Scotch whiskey from Scotland, which must age for three years.). The charred layers of oak help caramelize the sugars, contributing to the spirit’s distinct flavor and color. Depending upon how a distiller wants the barrel to affect their bourbon, they can choose the degree to which the oak barrel or oak container is charred. 7. __Dilute__. To ensure the proper alcohol content, distillers test and dilute their product with filtered water before or after aging (sometimes both). Before bottling, distillers may chill-filter the bourbon to remove any long-chain protein molecules and impurities that may cause the spirit to become hazy or cloudy when stored at low temperatures. 8. __Bottle__. The final step is the bottling process, in which bourbon makers add the final product to labeled bottles. Once the spirit is bottled, it stops aging. Learn more about mixology from award-winning bartenders Lynnette Marrero and Ryan Chetiyawardana. Refine your palate, explore the world of spirits, and shake up the perfect cocktail for your next gathering with the [MasterClass Annual Membership](https://www.masterclass.com). Bourbon is a liquor featured in several classic cocktails, from the Old Fashioned to the Bourbon Smash. Here’s the process by which distilleries turn grain into this traditional spirit.