Bourbon mash bills explained
A mash bill is simply the recipe of grains that goes into a whiskey. In bourbon it decides much of what you taste, from sweet corn to peppery rye. This guide explains the rules and the common recipes in plain language.
What a mash bill is
The mash bill is the list of grains in a whiskey's mash, usually given as percentages. A bourbon might be 75% corn, 13% rye and 12% malted barley. Distillers grind the grains, cook them in hot water to release the starch and let enzymes turn that starch into sugar. Yeast then ferments the sugar into alcohol.
Each grain brings something. Corn gives sweetness and body. Rye adds spice. Wheat gives a softer, rounder feel. Malted barley provides the enzymes that convert starch and adds a light biscuit note. Our guide to grains in whisky covers each grain in more depth.
The rules that make it bourbon
Bourbon has a strict legal definition under US law. It must be made in the United States from a mash of at least 51% corn. It must be distilled to no more than 80% ABV and go into the barrel at no more than 62.5% ABV. The barrel must be a new charred oak container. It must be bottled at no less than 40% ABV.
Nothing in the rules says how much rye, wheat or barley goes into the rest. That freedom is why bourbons taste so different from each other, even though they all share corn as their main grain.
The traditional rye recipe
The most common style of bourbon uses corn as the main grain, rye as the flavouring grain and malted barley for its enzymes. A typical traditional mash bill sits somewhere around 70 to 80% corn, 10 to 15% rye and 5 to 12% malted barley.
In the glass these bourbons are sweet and full, with vanilla and caramel from the new charred oak. The rye shows as a gentle spice at the back of the palate, a bit like clove or black pepper. If you are new to bourbon, this is the style most bottles you meet will follow.
Malted barley is in most bourbon mash bills for one main reason: its enzymes. Without malt or added enzymes, the starch in corn, rye and wheat would not turn into sugar. Distillers often use around 5 to 12% malt, which is enough to do the job. Some use commercial enzymes alongside it so they can keep the malt share low.
Malt adds a light biscuit or cereal note, though it is rarely the star of the glass in bourbon. Compare that with single malt Scotch, where malted barley is 100% of the grain.
High rye bourbons
Push the rye share up, often to somewhere between 20 and 35%. That gives you a high rye bourbon. Corn is still the majority grain, so it is still bourbon, but the spice moves to the front. Expect more pepper, mint, dill or rye bread notes alongside the sweetness.
These are popular in cocktails such as the Manhattan and the Old Fashioned, where the spice stands up to sugar and bitters. Above 51% rye the whiskey is no longer bourbon at all. It becomes a rye whiskey.
Wheated bourbons
Swap the rye for wheat and you have a wheated bourbon. A typical recipe might be around 70% corn, 15 to 20% wheat and the rest malted barley. With no rye spice, the corn sweetness and the oak come through more clearly. Wheated bourbons often taste softer, with bread, honey and toffee notes.
Our guide to wheated bourbon covers the style in detail, including how to taste it side by side with a rye recipe.
What the label tells you and what it does not
Most bourbon labels do not print the mash bill. Some distilleries publish theirs on their website or in tasting notes. Words like high rye or wheated on the label give a clue. The term straight bourbon means it has been aged at least two years in new charred oak with no added colour or flavour. If it is under four years old, the age must be stated.
Bourbon labels do not have to say where in the US the whiskey was made, though many proudly do. It does not have to come from Kentucky.
Tasting mash bills side by side
The fastest way to learn mash bills is a small side by side tasting. Pour 15 ml each of a traditional bourbon, a high rye bourbon and a wheated bourbon into identical glasses. Nose them in that order. Then taste, adding a few drops of water to each. Notice where the spice sits and how soft or sharp each one feels.
Keep the measures small, drink water between them and have food on the table. Never drink and drive after a tasting. Our guide to ex-bourbon, sherry and wine casks explains where those bourbon barrels go next, which matters to anyone who also drinks Scotch.
A first step for your own palate
Write one line of notes on each bourbon you try: the grain style if you know it, the main aroma and where you feel the spice. After a dozen bottles you will start to pick out rye from wheat without looking at the label. That is the start of a trained palate. It carries across to every spirit and beer you taste.
Common questions
What is a bourbon mash bill?
It is the recipe of grains used to make the bourbon, given as percentages. Bourbon must contain at least 51% corn, with rye or wheat and malted barley making up the rest.
What is a high rye bourbon?
A bourbon with a larger share of rye than usual, often around 20 to 35%. Corn is still the main grain, but the rye spice is more noticeable.
Does bourbon have to come from Kentucky?
No. Bourbon must be made in the United States, but it can be made in any state.
Why do bourbon recipes include malted barley?
Malted barley supplies the enzymes that turn starch from corn and the other grains into fermentable sugar.
