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Walking the Wilderness Trail, Part III: How Bourbon is Made

Bourbon’s legal definition varies somewhat from country to country, but many trade agreements require that the name “bourbon” be reserved for products made in the United States. The U.S. regulations for labeling and advertising bourbon apply only to products made for consumption within the United States; they do not apply to distilled spirits made for export. Canada and the European Union also requires bourbon to be made in United States, but in other countries, Products labeled “bourbon” may not adhere to the same standards.

According to the Federal Standards of Identity for Distilled Spirits, bourbon made for U.S. consumption must be:

  • Made from a grain mixture that is at least 51% corn

  • Produced in the United States and Territories (Puerto Rico) and the District of Columbia

  • Aged in new, charred oak containers

  • Distilled to no more than 160 proof, which is 80% alcohol by volume

  • Entered into the container for aging at no more than 125 proof, or 62.5% alcohol by volume

  • Bottled at 80 proof or more, which is 40% or higher alcohol by volume

  • Cannot have added coloring, flavoring, or other spirits

  • If a bourbon has added coloring, flavors, or other spirits, it’s called a bourbon whiskey, which has no aging requirement

Most bourbon has no minimum specified duration for its aging period. Products aged for as little as three months are sold as bourbon. The exception is straight bourbon, which has a minimum aging requirement of two years. In addition, any bourbon aged less than four years must include an age statement on its label.

Bourbon that meets the above requirements, has been aged for a minimum of two years, and does not have added coloring, flavoring, or other spirits may be – but is not required to be – called straight bourbon.

Some other facts about bourbon:

  • Bourbon that is labeled as straight that has been aged under four years must be labeled with the duration of its aging.

  • Bourbon that has an age stated on its label must be labeled with the age of the youngest whiskey in the bottle

  • Bottled-in-bond bourbon is a sub-category of straight bourbon and must be aged at least four years.

  • Bourbon that is labeled blended (or as a blend) may contain added coloring, flavoring, and other spirits, such as un-aged neutral grain spirits, but at least 51% of the product must be straight bourbon.

  • Bourbon that has been aged for fewer than three years cannot legally be referred to as whiskey (or whisky) in the EU.

  • “High rye bourbon” is not a legally defined term but usually means a bourbon with 20–35% rye. High wheat bourbons are described as more mild and subdued compared to high-rye varieties.

On a side note, the high rye content may have been why I wasn’t a huge fan of Wilderness Trail’s bourbon and why I tend to favor bourbons that are sweeter. When I looked back at my notes I realized that Wilderness Trail is a high rye bourbon. Now, to each his own: there are some palates who will love the “bitter” or “biting” quality of the rye (I’m not a sommelier or steward, so I don’t know what technical terms would apply to these flavors; it’s just how I’ve chosen to describe them). I also have nothing against Wilderness Trail. You can look back at Part I of this and see that. I just prefer a different bourbon.

The Process

As I noted earlier, to be legally sold as bourbon, the whiskey's mash bill requires a minimum of 51% corn, with the remainder being any cereal grain. A proposed change to U.S. regulations will expand allowable "grains" to include amaranth, buckwheat, and quinoa.

So here’s what happens, first the grain is ground and mixed with water. Presumably, Kentucky bourbon is known for having the best bourbon because of the limestone spring water used in our bourbons. Usually mash from a previous distillation is added to ensure consistency across batches, creating a sour mash. Finally, yeast is added, and the mash is fermented. This brew is distilled to between 65% and 80% alcohol using either a traditional pot still (called an alembic) or the much less expensive continuous still. Most modern bourbons use a column still and then are redistilled in a "doubler" (also known as a "thumper" or "retort"), which is basically a pot still.

The resulting clear spirit, called “white dog,” is placed in charred new oak containers for aging. In practice, these containers are generally barrels made from American white oak. The spirit gains its color and much of its flavor from the caramelized sugars and vanillins in the charred wood.

As mentioned earlier, straight bourbon must be aged at least two years, and blended bourbon must contain at least 51% straight bourbon base. The remainder of the spirits in a blended bourbon may be non-aged neutral grain spirits. If a product is labeled merely as bourbon whiskey rather than straight or blended then no specific minimum aging period is required. The only requirement is that the product has been "stored at not more than 62.5% alcohol by volume (125 proof) in charred new oak containers.”

Now it’s not just as simple as dumping the brew over into a barrel. The barrels have been charred on the inside. Now, you know I’m gonna have to do a blog on charring barrels at some point. So many content ideas, so little time.

At any rate, the quick explanation is that new barrels are exposed to flames for a determined amount of time to create a char level between 1-4. Level one char is a 15-second burn; level 2 char is a 30-second burn; level 3 char is a 35-second burn; and level 4,the deepest char, which is also known as Alligator Char because it looks like alligator skin, is a 55-second burn. Levels 3 and 4 are the most common for American bourbons and bourbon-whiskeys. The level of char is important because it affects the flavor and color of the distillate. Bourbon uses these barrels only once while other whiskies re-use their barrels or purchase used bourbon barrels.

Bourbons gain more color and flavor the longer they age in wood and since changes to

the spirit also occur due to evaporation and chemical processes such as oxidation, Kentucky’s hot summers are wonderful for assisting in the aging process. In the rickhouses (or rackhouses), the rarer bourbons are stacked at the top, because heat rises. In the summer, the barrel wood expands, soaking in the distillate. This is where the flavors and colors from the oak collect into the bourbon. In the winter, the barrel wood contracts, pushing the colors and flavors into the bourbon. However, the heat also causes the alcohol to evaporate some, too, producing less of the bourbon in a barrel. The evaporate is known as the angels’ share. So THAT'S what happens in Heaven! (Just joking).

At any rate, the play of the environment with the number of years a bourbon is aged is what makes a bourbon rare—and expensive. This is why 23 year Pappy Van Winkle, often called “Pappy,” goes for thousands of dollars per bottle. And this is why if you’re picking up a bottle of 2-4 year old Woodford Reserve or Buffalo Trace at the local liquor store, it’s probably going to cost between $25-$40. But the aging process is a fine balance because over-aging a bourbon can negatively affect the flavor, making it taste woody, bitter, or unbalanced.

After maturing, bourbon is taken from the barrel and is filtered and diluted with water. It is then bottled at no less than 80 proof (40% alcohol content). Although most bourbon whiskey is sold at 80 proof, other common proofs are 86, 90, and 100. All “bottled in bond” bourbon is 100 proof. Some higher-proof bottlings are marketed as “barrel proof,” meaning they haven’t been diluted or have been only lightly diluted after removal from the barrels. Bourbon whiskey may be sold at less than 80 proof but must be labeled as “diluted bourbon.”

After processing, barrels remain saturated with up to 10 gallons of bourbon, though 2–3 gallons is the norm. Since they can’t be reused for bourbon, most are sold to distilleries in Canada, Scotland, Ireland, Mexico, and the Caribbean for aging other spirits. Some are employed in the manufacture of various barrel-aged products, including amateur and professionally brewed bourbon-barrel-aged beer, barbecue sauce, wine, hot sauce, and others. Since 2011, Jim Beam has employed barrel rinsing on a large scale to extract bourbon from its used barrels, mixing the extract with a 6-year-old Beam bourbon to create a 90-proof product that it sells as “Devil's Cut.”

The bottling operation for bourbon entails filtering, mixing together straight whiskey from different barrels (sometimes from different distilleries), diluting with water, blending with other ingredients (if producing blended bourbon), and filling containers to produce the final product for consumers. By itself, the phrase “bottled by” means only that. However, if the bottler operates the distillery and produces the bourbon then “distilled by” can be added to the label. As noted earlier, only whiskey produced in the U.S. can be called bourbon.

Kentucky is the largest producer of bourbon and provides about 95% of the world's bourbon, and there’s more than 11 million barrels of bourbon currently aging in our rickhouses all over the state. We also have a few distilleries listed as National Historic Landmarks: Buffalo Trace, Maker’s Mark, and Woodford Reserve. A small town in Kentucky, called Bardstown is known as the Bourbon Capital of the World and hosts the annual Bourbon Festival each September.

Buffalo Trace
Buffalo Trace

Maker's Mark
Maker's Mark

Woodford Reserve
Woodford Reserve

Then, of course, there’s the Kentucky Bourbon Trail which boasts at least 41 distilleries that have met at least the minimum criteria to apply for membership to the Kentucky Distillers’ Association. The bare minimum for craft distilleries to join the Bourbon Trail is to have an inventory of between 1,000 to 10,000 barrels; the second tier Proof members have 10,000-49,999 barrels; the third tier Heritage members have more than 50,000 barrels each year.

I recently toured a couple of other distilleries, Evan Williams in Louisville and Lexington Brewing and Distillery in Lexington, so I’ll be sure to post about those soon to round out my bourbon “tour” here on the blog. Then I promise I’ll move on to other topics. Maybe I’ll explore a historical figure? But then a good mystery would be great, too! Or—in the best of both worlds—maybe I can find a good historical mystery!


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