How is Bourbon Made?

Bourbon is a type of American whiskey. By law it's distilled from grains - known as a mash - made up of at least 51 percent corn, though most bourbons are made with over 70 percent. It’s the corn that gives bourbon its distinctive sweet taste. It must also be aged in new charred-oak barrels, as opposed to barrels that have been used to age other spirits, but how is bourbon whiskey made? Read on to find out.

Engineering How It’s Made
15 October 2022

Over 95% of bourbon whiskey is made in Kentucky and every year, the Bluegrass State produces around 420 million litres of the sweet, smokey spirit.

In fact it would be hard to find anything more uniquely American than bourbon whiskey, unless you saw Ronald McDonald in Disneyland wearing a New York Yankees baseball cap and eating a hot dog from Nathan’s.

When it comes to the question of ‘how is bourbon produced’, the answer has barely changed since the late eighteenth or early nineteenth century. Today, consumers spend billions of pounds on Jack Daniels, Jim Beam, Maker’s Mark, Wild Turkey and a host of bourbon brands and here, we’ll tell you how they make bourbon in a factory.

A Short History of Bourbon Whiskey

There doesn’t appear to be a time and a place where bourbon was invented, rather it evolved in and around Kentucky through the early European settlers from Britain, France, Germany and The Netherlands.

The Europeans brought with them a distilling culture that went back hundreds of years. Each group used a variety of grains to make their spirits. Almost unheard of in Europe at that time, corn had been cultivated on the North American continent for hundreds, if not thousands of years, and it was corn that became the bedrock of bourbon.

Two men have been often credited with the invention of bourbon – a Baptist minister called Elijah Craig and a distiller named Jacob Spears – but these tales have been largely scrutinised and are rarely told outside of the towns in which both men resided.

Similarly, the name bourbon also has conflicting origins. Some stick to the story that it was named after Bourbon Street in New Orleans, at the time a major port where Kentucky whiskey was cheaper than imported French cognac. Others maintain it was named after Bourbon County in Virginia, which became part of Kentucky when it split from Virginia in 1792.

Over the years, how bourbon is made became a very important part of the local – and subsequently national – culture, similar to Champagne in France, Stilton cheese in England and Parma ham in Italy. So much so that there are very strict laws governing the production of bourbon today.

One rule most people believe to be true is that bourbon can only come from Kentucky. Although 95 percent of bourbon is actually from Kentucky, it can be made in any of the other 49 states provided the rules are very strictly adhered to. Like a shot, let’s get neatly into how bourbon is made.

How Bourbon is Produced

Bourbon barrels (Photo: Matthew Liteplo via Getty Images)

Today, bourbon is enjoyed by millions of people all over the world. And while there are many different brands and styles of bourbon, they all have one thing in common: they’re all made with the same basic ingredients – a mash of corn, rye, and barley. The mash is then fermented and distilled to create the finished product. Bourbon must be aged in new, charred oak barrels for a minimum of two years, though most bourbons are aged for four years or longer. So how is bourbon produced in the step-by-step manufacturing process? Let’s take a closer look.

The Corn

The first step in the process of how bourbon is made is the core ingredient, the corn itself. Once the corn is harvested, it’s delivered to the processing plant where the first step is to sift out any cobs and foreign materials like twigs or stones.

The Grinding

The individual corn kernels are then sent to a grinding machine where rollers crush them to release the starchy flavours. This leaves the germ and the husk, which are often used as an ingredient in animal feed. In separate batches, the machine also grinds malted barley and a variety of wheat which varies from company to company.

The Mash

How is bourbon whiskey made? It’s the cooking that sets bourbon apart from other types of whisky. The corn is cooked with the malted barley, wheat, and limestone-rich, iron free Kentucky water, as well as a secret recipe yeast formulation. This is known as the grain mash.

The Cooking

The mash flows into open fermentation tanks made of cypress wood and after around eight to ten hours, the yeast has had time to work and the liquid is bubbling. This is caused by the release of carbon dioxide as the grain sugars ferment and are turned into alcohol.

The Distilling

After around three days, the liquid has thickened in what is known as ‘distiller’s beer’. It’s pumped into a column still which boils off the alcohol. The alcoholic vapour rises up and is condensed into liquid.

After a second distillation, the alcohol concentration is at an undrinkable 130 proof, or 65 percent alcohol, and it’s as clear as water. At this stage of the process of how they make bourbon in a factory the liquid is known as ‘white dog.’

Next, water is added to dilute the liquid down to 110 proof, or 55 percent alcohol, and a sample is taken and sent to the lab. There, a technician puts the sample through a gas chromatograph tester which analyses the flavour compounds and alcohol strength.

The Barrelling

Once the lab has given the thumbs-up, the liquid is pumped from the storage tanks into brand-new oak barrels which have been charred on the inside.

The reason the insides of the barrels are charred is that it caramelises the naturally-occurring wood sugars which adds a unique sweetness to the bourbon as it ages. In addition, it also turns the bourbon into its characteristic rich amber colour.

The barrels are stopped with a walnut cork and moved to a warehouse, where they’ll sit for a minimum of two years and often up to 10 years or more to mature. Part way through the ageing process they’ll be moved to another area of the warehouse due to temperature variations, albeit very subtle.

The Bottling

There’s just one more thing to do before we can finish answering the question ‘how is bourbon made?’ When it’s ready, the cork is taken out and the bourbon whiskey is poured into a trough, where it will have aged perfectly. More water is added to get it down to 90 proof, or 45 percent alcohol, and then it’s bottled, sealed and labelled. The final step is to dip the caps in hot wax. Not only does it look great, it seals the bottle so it can be kept for years. This is the final step in the process of how they make bourbon in a factory.

You May Also Like

Explore More