What Is Bourbon Made From? A Kentucky Distiller Breaks It Down

What is bourbon made from? If you’ve ever wondered what actually goes into that glass, the answer is simpler than most people think. Bourbon is made from grain, water, yeast, and time spent inside a charred oak barrel. That’s it. No artificial flavors, no coloring, no added sweetness.

We’re going to walk you through the ingredients and the process. And we’re not pulling this from a textbook. We make bourbon every single day at our distillery in Burkesville, Kentucky. So this is straight from the source.

The Grains: Where Bourbon Starts

Every bourbon begins with a grain recipe called a mashbill. By law, the mashbill has to be at least 51% corn. That corn is what gives bourbon its natural sweetness. Most distilleries land somewhere between 60% and 80% corn, depending on the flavor they’re after.

The rest of the mashbill is made up of what the industry calls “flavor grains.” These are usually rye, wheat, or malted barley, and they shape the character of the finished bourbon.

Here’s how those flavor grains break down:

• Rye adds spice, pepper, and a little bit of bite. Bourbons with more rye tend to be bolder and more complex.
• Wheat softens things out. It creates a smoother, gentler flavor with hints of bread and honey.
• Malted barley helps with fermentation and adds a subtle nutty, biscuit-like note.

At Southern Kentucky Distillery, we use two main mashbills. Our RB22 mashbill is 69% corn, 21% rye, and 10% malted barley. That’s what goes into our high rye bourbons. Our WB21 mashbill swaps the rye for wheat (69% corn, 21% wheat, 10% malted barley) for a smoother, softer profile. Both use locally sourced grain and purified water harvested right here in Cumberland County.

What Grain Is Used to Make Bourbon?

Let’s be direct about this. Corn is the primary grain used to make bourbon. That’s the legal requirement, and it’s what separates bourbon from other types of whiskey.

Rye whiskey, for example, has to be at least 51% rye. Scotch is typically made from malted barley. But bourbon? It’s a corn-based spirit. Always has been.

The type and amount of grain in the mashbill is really what sets one bourbon apart from another. A bourbon with 21% rye in the mashbill (like our Long Ridge High Rye) is going to taste noticeably different from a wheated bourbon (like our Turby’s Cherrywood). Same distillery, same water, same barrels, but the grain changes everything.

The Barrel: Where Bourbon Gets Its Flavor

Here’s the thing most people don’t realize. A huge percentage of bourbon’s flavor actually comes from the barrel, not the grain. Some estimates put it at 60-70% of the final taste profile.

Federal law requires that bourbon be aged in brand-new, charred white oak barrels. That’s not optional. You can’t reuse barrels and call it bourbon. The inside of each barrel is charred with an open flame, creating a layer of caramelized wood sugars and activated carbon.

What the barrel does to bourbon:

• Color: Bourbon goes into the barrel as a clear liquid. The amber and caramel color you see in the glass? That all comes from the wood.
• Vanilla and caramel notes: These come from compounds in the charred oak called vanillins and lignins.
• Tannins: These add structure and a subtle dryness, similar to what you’d find in red wine.

Here in Kentucky, the temperature swings throughout the year are pretty extreme. Summers get hot. Winters get cold. That forces the bourbon to push into the wood grain and pull back out, over and over again, for years. Every cycle extracts more flavor and color. It’s one of the reasons Kentucky has been the center of bourbon production for over 200 years.

The Legal Requirements for Bourbon

Bourbon isn’t just a name. It’s a legally defined product. Here are the rules a whiskey has to follow before it can be called bourbon:

If the bourbon is aged for at least two years and produced in Kentucky, it can be labeled “Kentucky Straight Bourbon Whiskey.” That’s the gold standard, and it’s what we produce at Southern Kentucky Distillery.

Water and Yeast: The Unsung Ingredients

Water

Kentucky sits on massive limestone deposits. When water filters through that limestone, it strips out iron (which would turn bourbon black and make it taste metallic) and picks up calcium and magnesium. The result is naturally clean, mineral-rich water that’s perfect for distilling.

We use purified, locally harvested water at our distillery. The water source matters more than most people think.

Yeast

Yeast converts the sugars from the grain into alcohol during fermentation. Different yeast strains produce different flavor compounds. Some create fruity esters. Others bring out spicy or floral notes. Our fermentation process is overseen by Dr. Patrick Heist, one of the most respected fermentation scientists in the industry.

From Grain to Glass: The Process

Here’s how bourbon actually gets made, step by step.

Milling and mashing: The grain is ground and mixed with hot water to create a mash. This converts the starches in the corn into fermentable sugars.

Fermentation: Yeast is added to the mash. Over the course of several days, the yeast eats the sugars and produces alcohol. The result is basically a beer (called “distiller’s beer”) at around 8-10% ABV.

Distillation: That beer runs through our 18-inch column still, which strips away impurities and concentrates the alcohol. Our still creates a particularly clean distillate. It’s a balance of old tradition and modern science.

Barreling: The clear distillate (called “white dog”) goes into new charred white oak barrels. This is where the aging process begins.

Aging: The barrels sit in our bonded warehouses for years. Time does the heavy lifting here. As the bourbon ages, it gets smoother, more complex, and more flavorful.

Bottling: When the bourbon is ready, it’s pulled from the barrel, proofed down with water if needed, and bottled.

Want to see this process in person? Here’s a look inside our distillery:

What Our Bourbon Tastes Like

So now you know what bourbon is made from. But knowing the ingredients and actually tasting the finished product are two very different things. Here are two bourbons we make that show how the same basic ingredients can produce completely different results.