Distillation & Whiskey Production: Notes from the Kentucky Bourbon Trail

By Denise Gardner, Extension Enologist dxg241@psu.edu http://extension.psu.edu/enology In March 2013, I visited the heart of American bourbon production to evaluate the standard for whiskey

production practices. The rise of craft distilleries in Pennsylvania and the use of bourbon barrels for wine

products demand a better understanding of how production can influence the final product. Distilleries

ranged in size from small family-owned businesses to large multi-million gallon production facilities. Yet

quality standards and love for the product remained in every distillery visited.

Below is an explanation of bourbon production: facts that may be of interest to those considering using

bourbon barrels, starting a distillery, or looking to produce distilled spirits. At the end, I will also note a

few points that I found incredibly valuable as a tourist through The Kentucky Bourbon Trail, and things

that could be considered for the Pennsylvania wine industry. For more information on The Kentucky

Bourbon Trail, please visit http://kybourbontrail.com/.

What is Bourbon? Bourbon, like Scotch, is a form of whiskey that is defined by the area in which it is produced and a series

of strict regulations for production. While there are many similarities between whiskey and bourbon

production, bourbon producers are required to adhere to several guidelines throughout production to

ensure product purity and quality. The Code of Federal Regulations (CFR) specifies bourbon with the

following requirements:

Grain mixture (of the mashbill) containing at least 51% corn

Cannot exceed 160 proof (80% alcohol) in the distillate

Cannot be barreled for aging at more than 125 proof (62.5% alcohol)

Must use new, charred, American white oak barrels for aging

Must be bottled at or above 80 proof (40% alcohol)

Bourbon Production Bourbon and whiskey production, like wine, is a blend of science, art, and tradition. Although the

expression of the final product is left in the hands of the master distiller and proprietary to each

bourbon house, production is state-of-the art and includes a series of routine quality control measures.

Incoming raw material (e.g. the grains), water, fermentation, and sanitation practices are standardized

and monitored regardless of the size of the production facility. The flow chart below illustrates the

general production of bourbon.

Although some could argue that the distillate lacks flavor, the initial blend of the mash bill will

contribute to the final aroma/flavor and mouthfeel of the bourbon after it is aged in barrel. Corn is

typically sourced within a 100 mile radius of the distillery, and must be received at no more than 14%

moisture content. Other quality control protocols include:

Organoleptic analysis for mold, mildew, and musk

Screening for foreign objects

Evaluation for dried or split grains

Sample of raw grain to be held until each batch has matured

Corn that does not meet this quality parameter is rejected from the

distillery and commonly sent to a feed lot. As the quality of the

incoming raw material affects the quality of the final product, such

check points are essential.

After the grains are received and quality is ensured, they are milled at

the distillery and mixed into the appropriate proprietary blend. For

bourbon production, the distiller’s beer, or mash bill is a blend of at

Another

Distillation? Second

Distillation

Barrel Filling Barrel Aging

Bottling Shipping for Retail

Grain Milling Mash Distiller’s Beer

Fermentation

First

Distillation

Incoming Raw Material:

Corn, Wheat, Malted Barley, & Rye

Yes

No

least 51% corn mixed with wheat, rye, and/or malted barley. From here, making the distiller’s beer is

similar to brewing. The grains are mixed with water and sent to open-top tanks for primary

fermentation. Tanks were traditionally made of red cypress wood (sourced from Florida), but as this

tree is now listed on the Endangered Species list, replacement tanks are being made with Douglass Fir

trees. Both woods are considered neutral in flavor and can be in use for about 50 years. Other bourbon

houses conduct the primary fermentation in stainless steel open-top fermentation tanks.

The mashbill is then inoculated with a yeast strain, which is highly proprietary to each bourbon house.

Although some distillation houses use commercial yeast strains, many maintain their own yeast cultures

which have been used to make distiller’s beer for several decades. Others add a different yeast strain to

individual fermentation tanks, which ultimately produce a series of final whiskeys that vary in their

aroma and flavor profile. [NOTE: Essentially, these nuance flavors are also noticed in wine production.]

Fermentation progresses over a three to five day time period.

Temperature is monitored and maintained through a cooling coil

placed inside the fermentation tank. It is essential to monitor

temperature during primary fermentation to avoid blowing off nuance

flavors or cooking the mash bill too high. This is especially important

when part of the mash bill contains rye, as it can cook more easily than

other grains during fermentation.

Following fermentation, the mash is sent to a still, which is typically a

column still. The mash enters the still at a lower unit of the column. As

the mash is heated, the vaporized products will rise to the top of the

column. The content of those vaporized products will depend on the

distillation temperature.

The initial vapors that rise to the column contain several impurities (including methanol). This fraction

of the distillate is commonly known as “the heads” and is condensed and separated into its own holding

tank. This is also true of “the tails” or the vapors that are emitted at the end of distillation. “The hearts”

(vapors in between “the heads” and “the tails”) contains the ethanol

product that is collected for the bourbon. This is the main concern of

most distilleries. Once ethanol rises to the top of the column it is

collected, funneled, and condensed into a separate holding tank.

However, the product is not refined enough to act as the distillate that

will be used to fill barrels.

Therefore, many distilleries re-distill the distillate through a second

distillation process and in a secondary still (column, pot,

tumbler/doubler). This extra processing step increases the proof of

the distillate and refines the distillate of impurities that were retained

in the first distillation step. This distillate is commonly referred to as

the “white dog.” Other regions may refer to this as “white lightening”

or “moonshine.” Essentially, this is a clear, high proof spirit. Quality control steps are usually taken here

to monitor quality and consistency of the distillate. Like with wine, much of this is accomplished

through sensory analysis by a panel of experts located within the

distillery.

Following distillation, the spirit is adjusted to a proof that is no

higher than 160 proof (80%) alcohol. It is then put into barrel.

Barrels are made of white American oak wood, and must be new.

Oak barrels can be charred to four different char levels: 1 through 4.

The level of char will contribute to how the whiskey ages in barrel,

the color of the whiskey, and the flavor profile imparted by the

wood. The greater the char, the further into the wood the ethanol

can penetrate into as it matures in the barrel.

Barrels are typically inspected for quality as they arrive at the

distillery. Each is labeled with the bourbon house identity, the char

level, the proof of the distillate, the date it enters the rick house, and capacity or volume. Most barrels

are also identified by a serial number. Once the barrels are filled, they are plugged with a yellow poplar

cork, which expands to create a tight seal and prevent any whiskey from dripping out of the barrel

during the aging period.

Barrels are stored in rick houses, which can be

anywhere from one story to several stories high.

Once a barrel is placed in a rick house, it is not

moved throughout its maturation. Recall that

bourbon has to age for at least 2 years prior to

being removed from the barrel. As these rick

houses are not temperature or humidity

controlled, the placement of the barrel in the rick

house will contribute to the final proof of the spirit

once it is fully matured. More water will evaporate in the barrels located higher up in the rick house

and, therefore, will contain a higher proof by the end of its maturation process. As the whiskey rests in

barrel, temperature fluctuations of the rick house will cause the wood to expand and contract over time.

This allows the ethanol to penetrate into the wood and extract flavor during the maturation process.

At the completion of maturation, the bourbons are analyzed for taste, aroma, and proof (alcohol

percentage). Several bourbon houses sell “single barrel bourbons”

which are selected based on these quality parameters. Single barrel

bourbons must contain a specific aroma/flavor and taste profile to be

selected. Single barrel bourbons are not blended and are bottled

independently of the other barrels. These products are usually

packaged in a specific bottle and labeled with detailed information

regarding the location of the barrel within the rick house and the

date the bourbon was bottled.

Other products that distilleries produce include the house bourbon

and small batch bourbon. Both products are blends of several

barrels, and carefully blended to maintain consistency that

consumers expect in the final product.

Distilleries also have the option of selling the “white dog:” the clear spirit that is produced directly off of

the still. This product offers immediate cash flow for the distillery. Compared to bourbons or other

whiskey products, the “white dog” does not require any maturation time prior to its sale.

Bourbon Barrels As barrels can only be used once by bourbon distilleries, many are sold to beverage producers in Canada

and Scotland for aging of other spirits (whiskey, Scotch, etc.). However, with the rise of craft distilleries,

craft breweries, and wineries, many bourbon barrels are sold to these small businesses. These smaller

operations utilize the barrels to impart spicy bourbon flavors and colorings in their final products.

[NOTE: Bourbon barrels will not age or mature wines the same way that wine barrels will. Variations in

char/toasting levels, as well as barrel size and the previously held spirit will alter the wine product.]

Distillation Sanitation Although bourbon, whiskey, and distilled spirits are high alcohol and low-risk food products, sanitation is

still an important part of production. Much like brewing, the distillation process is primarily automated

and maintained through clean-in-place (CIP) processes. Most winery operations do not quite function in

this way.

Cookers, yeast tubs, and fermenters are typically

pressure washed and steam cleaned for several hours in

between each batch. Some houses also discussed the

use of the “heads” or “tails” for pre-rinses after

cleaning steps.

Bourbon and whiskeys tend to have some wood residue

in their final product. Removing particulates by

filtration makes a smoother product and ensures a

transparent product for consumers, but this is not

accomplished for all bourbon products. Some bourbon

houses also reported using a chiller filtration system to bind up fatty acids and amino acids that are left

in the bourbon after maturation. Additionally, during bottling, bottles are typically pre-rinsed with

bourbon prior to filling, which ensures product purity.

The Bourbon Trail, as a Tourist The Kentucky Bourbon Trail located outside of Lexington, Kentucky is surely a place where tourists can

relax, enjoy good food, take tours of distilleries, and, of course, taste some bourbon! Below are some

notes as to what I found interesting and impressive as a tourist on The Kentucky Bourbon Trail. Two

“trails” have been created in Kentucky to maintain marketing and awareness of bourbon production:

1. The Kentucky Bourbon Trail, which includes the largest commercial bourbon houses.

2. The Kentucky Bourbon Trail Craft Tour, which features a series of smaller distilleries, some

which do not produce bourbon, but do make distilled spirits on a smaller scale.

At each registered distillery, a “Passport” can be picked up by tourists. As one travels from one distillery

to the next, tourists get their “Passport” stamped. If one of the “Passports” is stamped by each distillery

within the booklet, tourists can mail in their “Passport” and receive a free commemorative gift. I

thought this to be a clever idea to encourage consumers to visit each associated distillery.

Additionally, most distilleries are adorned with merchandise at varying price points that appeal to a wide

array of individuals. I was always surprised at how each tasting room gave me a different feeling upon

entering the building. Each tasting room was eye-appealing and staff members were always up front,

greeting new guests, stamping “Passports,” and explaining what their distillery had to offer visitors. The

look of these tasting rooms really emphasized how important it is for visitors to have an overall positive

experience. I especially enjoyed the varying glasses, food products, clothing items, and Bourbon Trail

memorabilia that captivated each retail area.

Heaven’s Hill Distillery had a particularly interesting display. One side

of the tasting room was designated as a “self-guided” tour complete

with explanations on how bourbon is made, the history of bourbon,

and several 30-second videos showing bourbon production. On the

other side of the retail area was a sniffing machine in which guests

could smell different levels of aging bourbon. This was such a fun and

creative experience for guests that emphasized the sensory-nature of

bourbon. Although this individual unit may have been expensive, it is

definitely something that many wineries could include as part of their

experience when people visit a tasting room!

Finally, all distilleries that I visited had tours of the distilleries. Some

tours were free of charge, but on a routine schedule. Others included

a fee, some of which would include a tasting glass with the tour.

None of these tours disappointed. Oddly enough, although processing was similar from one distillery to

the next, there was a lot of variation among each of the bourbon houses. Some had technical staff

available to answer production questions while others had a guided script. Some of the tours included

mash tastings while others did not. Tastings of the bourbon itself were limited (for obvious

consumption reasons), but all tours included a small tasting of their products. Tours brought to life how

bourbon was produced and many were captivating to their audience.

One bourbon house was even in the process of creating a Bed and

Breakfast on-site so that guests could be a part of the production

experience.

As a tourist to the area, I really felt like I got a taste of the bourbon

experience. This point is often emphasized when talking about

visitors to the winery: sell the experience. On the long drive back to

Pennsylvania, I had to admit to myself that I felt an overall positive

energy in the heart of American distillation, and truly enjoyed all that

I had learned in addition to what I had set out to discover when I

took the trip. For more information on the Kentucky Bourbon Trail,

please visit: http://kybourbontrail.com/