Steps to Making Bourbon

Bourbon is the quintessential American liquor. Born of the Whiskey Rebellion in the late eighteenth century, bourbon’s unique qualities are now regulated by law and include that it must be made from a mash of at least 51% corn, distilled under 160 proof, and aged at least two years in charred new oak barrels. Although location is not regulated, most bourbon producers are in Kentucky, where they find the spring water has the ideal mineral balance for the taste of bourbon.

Bourbon begins with a mixture of ground grains known as a “mashbill.” Most bourbon is 60 to 80% corn, with smaller quantities of rye and malted barley. A few distillers use a small amount of wheat. The grains are ground into a very fine flour.

The grain is cooked into a mash. Each type of grain requires different cooking times and temperatures, and each grain is added to the cooker at a different point in the process. After cooking, the mash is cooled.

When water is added to the mash, the resulting mixture has a neutral pH, which doesn’t allow the yeast to work. To acidify the mixture, brewers add some of the stillage, the residue from the prior distillation, to the mash. The result is a slightly acidic mix where the yeast can work well. The acidic stillage is known as sour mash or backset.

Each distiller has its own yeast stock. Some of these yeast strains date back to before prohibition and are closely guarded secrets. Different yeasts produce different flavors, so each bourbon recipe has its own blend.

The cooled mash is placed in a fermenter with selected yeast. Yeast acts on the mash to produce alcohol and carbon dioxide. After a few days, a “distiller’s beer” of approximately 12 proof comes out of this process.

The “beer” is heated and pumped into the top of a column still. Steam is forced up from the bottom of the still. When the steam meets the beer, the alcohol portion vaporizes and rises to the top of the column, where it is caught and recondensed. This intermediary stage is known as “low wine.”

The residual mash left at the bottom of the still is called stillage. Most of it is sold as animal feed and a small portion is used in the process as “sour mash.”

Most bourbons are distilled twice. The second distillation is done in a smaller still, though it is exactly the same process, and results in a higher proof product known as “high wine.”

Bourbon is aged in American oak barrels that are first “toasted,” a process that caramelizes the sugar in the wood, and then charred on the inside to produce a layer of charcoal. Barrels may only be used once to make bourbon.

Once the bourbon has aged to the satisfaction of the distiller, the barrels are emptied, and the bourbon is filtered to remove any impurities, such as charcoal residue from the barrels. The filtered liquid is then bottled in various types and sizes of containers.

Beyond this basic process, the details of production are what give each bourbon unique taste. The exact mixture of grains, the yeast strains used, the rotation of barrels during storage – all these factors go into making that precise liquid that you pour in to your glass and enjoy.


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