Bourbon is a type of American whiskey predominantly made in the southern United States and has been produced since the 18th Century. It is made of a blend of different grains, with the bulk of the grain alcohol coming from corn, and grains such as malted barley, rye, or wheat making up the rest.
Once distilled, the high-proof alcohol is aged in white oak barrels for at least two years, though often much longer, before being bottled. The bottled alcohol is usually altered so that it is 80 proof, in order to allow it to be sold in states, which have a proof limit on the sale of spirits. Higher proof bourbons, often as high as 125 proof, are sometimes bottled, in which case they are usually referred to as cask strength – as they are bottled at the proof at which they come out of the cask. Cask strength bourbon tends to be available only from higher-quality manufacturers and often fetches a premium price.
The name bourbon comes from the original territory name of a large swath of the old south, named after the French royal family of the time. The whiskey coming out of this region was predominantly corn whiskey, which was a novelty to many people, and so they started referring to it as bourbon in reference to its place of origin.
Nearly all bourbon produced comes from the state of Kentucky, and many people hold that only corn whiskey from Kentucky can truly be referred to as bourbon – Popular Kentucky bourbon manufacturers include Jim Beam, Old Crow, Maker’s Mark, Wild Turkey, and Heaven Hill. Some bourbon manufacturers outside of Kentucky include Triple Eight of Massachusetts, Ezra Brooks of Missouri, Rebel Yell of Missouri, and Virginia Gentleman of Virginia. It should be noted that Jack Daniel’s, which many people think of as quintessential bourbon, is in fact a Tennessee whiskey, not a bourbon at all.
Grains– The main ingredient in bourbon is corn which varies from 51% to 79% depending on the brand. The other ingredients are rye, malted barley (10-15% each), and in some cases red winter wheat (10%). Distilleries are meticulous about selecting their crops, and once approved by quality control, the grains are stored in silos. The grains are ground in a hammer mille into a fine flour.
This mixture is called the mash, is fermented through a process called sour mash fermentation in which yeast from previous fermentations is added to induce the new batch to maintain a consistent flavor and quality.
Mashing– The grain is placed in a mash cooker with iron-free water and cooked for approximately 30 minutes. The corn is cooked the longest at a temperature of 220 degrees Fahrenheit (F), the rye at 170F, and the barley 150F. The mix is then transported to a fermentation tank and it is called mash. The result is then distilled to produce a clear spirit.
Fermentation– At this stage, the yeast is prepared by placing a nutrient solution below a pear or apple tree. Once the solution has collected the yeast, it is placed in an oven, bred, and then left in stasis at around 95-100F. Only a small amount is removed (a few grams) and added to a malt extract. A mixture of approximately two cups of yeast is added to a large storage container called the “Dona Tub”. Once the mash has been cooled to 75-85F, the yeast is added to the fermentation tank. The yeast breaks down the sugar in the mash converting it to alcohol and carbon dioxide over a period of three days. The alcohol is actually beer which is 10% alcohol/volume (20 proof). It is drained from the fermenting tube into a beer well.
Distillation– To separate the whiskey, the beer is moved to the bottom of a still where it is heated at 200F. The liquid boils at the bottom and moves to the top in the form of a gas. The gas is filtered to a tank called a “thumper” where it is condensed. The liquid is called “low wine” and it is 45-65% alcohol/volume (90-130 proof). The liquid is then condensed again to further refine the flavor and it is now called “White Dog” or “high wine” (50-58% alcohol/volume or 100-116 proof). The White Dog is often sampled and then put in a barrel to mature.
Cooperage- Bourbon must be stored in new, white oak barrels. The wood is cut into staves which are super heated and bent into ovular form. The barrel is then “toasted” by sending it through a small fire for about 12 minutes to caramelize the sugar in the wood. Next, it is applied to a larger fire for 6 to 12 seconds to burn out the inside and produce a charcoal layer. The charring must cover the barrel evenly so the whiskey has a consistent flavor. Finally the barrel is closed by a “Bung” and transported to the distilleries. Once the barrels have been used, they are often re-sold to age Scotch.
Maturity– The barrels are transported to warehouses where they are placed using a series of elevators and moveable joints. Each barrel must stay for at least two years, and sometimes more depending on the position in the warehouse. A year consists of one cycle of expansion and contraction. When the temperature rises in the summer, the bourbon expands, and with lower temperatures in the winter, it contracts. This movement gives the bourbon its amber color and oak flavor. After a designated period, someone will open the barrel and taste if the whiskey is ready. If it meets the brand’s standards, the barrel is opened, bottled, and shipped. which is what imparts color onto bourbon. Consequently, bourbons that have been aged longer are generally darker in color.