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What is a Mash Bill?

The mash bill of a whisky is the grain combination used when making multigrain spirits such as bourbons. Unlike single malt these do not consist of a single grain, but are instead produced using a mixture of different grains such as corn, rye, wheat and barley

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The mash bill of a whisky is the grain combination used when making multigrain spirits such as bourbons. Unlike single malt these do not consist of a single grain, but are instead produced using a mixture of different grains such as corn, rye, wheat and barley

If you’re a Scotch Single Malt fan, you won’t come across the term mash bill or grain recipe. The raw material on which this spirit is malted barley. Talking about a grain recipe here makes as much sense as saying “Warning, hot” on a coffee mug. It goes without saying, it is unnecessary.

This is different with Irish pot still whiskies, or with US whiskies such as bourbon, rye etc. which do not use a single grain, but instead leverage a mixture of different grains. The distillery specifies how much of each variety it uses in the so-called mash bill .

For example, a distillery in the USA is required by law to use at least 51 percent corn for its bourbon, but is free to choose any other variety of grain for the remainder. In addition to wheat and rye, some distilleries also end up with rice, oats and other varieties in the mash tun. However, most bourbon producers limit themselves to these 4 grains:

  • Corn : Gives the bourbon its distinctive flavour profile
  • Wheat : Provides a soft mouthfeel
  • Rye : The whiskey gets a spicy and fresh note
  • Barley : Its enzymes are considered a kickstarter for the mashing process.

While it is possible to produce 100% corn based bourbons this is unusual and would require the use of commercial enzymes. The proportion of grain in the mash or mash bill differs for each distillery and thus characterizes the typical character of the bourbon brand.

What is Mash?

The mash is a mixture of grain, water, and yeast that is initially fermented to produce alcohol. Whether making rum, bourbon or Scotch mash is the first stage in the production of alcohol.

Mash is not just mash. Because the composition of different types of grain has an important influence on the later character and taste of the whiskies produced. Therefore, each distillery has its own Mash Bill recipe, which is closely guarded and strictly adhered to in order to obtain a spirit that is as consistent as possible. Distillers are very careful to regulate the pH of their mash; if it gets too high (basic), unwanted bacterial growth can occur. One of the ways this is managed by american distillers is the sour mash method.

The composition of the mash bill for bourbon whiskey

Although each distillery has its own Mash Bill recipe, there are also legal requirements that whiskey manufacturers have to comply with. For example, for bourbon whiskey, the mash must be at least 51% corn. Most of the time, the corn share is usually 70% or more.

The remaining composition of the Mash Bill can be freely assembled by the Master Distiller. In addition to corn, bourbon whiskies often contain the classic whiskey grains barley and rye, and more rarely wheat. Even oats are a possible addition. The distillers are relatively free in their choice here, but each grain brings its own characteristics to the later whiskey.

How Grain Varieties Affect Bourbon

Since corn makes up the largest part of bourbon whiskey, one would think that it is also decisive for the later taste of the bourbon whiskey. However, this is only partially correct. If the whiskey is freshly distilled (so-called New Make Whiskey or White Dog), you can still clearly taste the corn characteristics, the other grain flavours are more hidden. However, the longer the whiskey is matured in oak casks, the more the corn disappears and the other grains as well as the characteristics of the oak wood emerge.

Corn makes the bourbon “buttery” and “nutty”

Although the “corn taste” supposedly disappears during storage, it is nevertheless characteristic of the later bourbon taste. For example, corn gives bourbon new-make buttery notes. The storage of the whiskey in American oak casks imparts the bourbon with notes of vanilla and caramel. Aromas that are very typical of the characteristic taste of bourbon. In combination with the corn, this results in a nutty taste. So it could be said that corn doesn’t really bring its own taste characteristics to the bourbon, but rather supports the development of subsequent flavours during maturation.

The special enzymes of barley

The use of malted barley in the mash brings malty aromas and the taste of chocolate and pastries to the bourbon whiskey however that’s actually almost irrelevant. Barley is also of crucial importance for the production of bourbon whiskey for a completely different reason. Malted barley contains special enzymes that help convert the starch contained in the mash into sugar. This allows the added yeast to ferment the sugar more easily into the so-called “Distiller’s Beer”, from which the whiskey will be distilled. Barley is less important in Bourbon for its taste than for its enzymes in the whiskey production. These enzymes are the reason for its inclusion included in almost every mash bill.

The flavour carriers rye and wheat

Since corn and barley only provide the raw material for the bourbon, additional grains are ofted added for flavour. Rye and wheat are often included in the Mash Bill. Rye is known from rye whiskies (min. 51% rye in the mash) which generally taste very spicy and intense. Aromas such as nutmeg, cloves, cinnamon and herbal notes can be traced back to the rye. These flavours are enhanced by maturation in freshly charred American oak barrels.

If the distillery is focusing on mouthfeel, or simply maximising yield with minimal cost then wheat is a popular choice. The spirit should be softer and creamier on the tongue and have a sweeter taste. While wheat is now used less frequently in bourbon whiskies (these are often referred to as wheated bourbons), it is still one of the classic whisky grains. Bourbons with a proportion of wheat usually taste a little sweeter. However, this is not because wheat is a sweeter grain. In contrast to rye, it is only milder and less dominant in taste, so that more sweet aromas of the wood, such as vanilla and caramel, come through and make the whiskey appear sweeter. Well-known bourbon whiskies with wheat in the mash are, for example, Maker’s Mark and Old Fitzgerald.

How important is the mash bill to bourbon flavour?

The composition of the mash has an important part in the taste of the later bourbon whiskey. It is estimated that around 20% of the flavour is due to the selection and composition of the grains in the mash. Another 10% of the flavour characteristics are due to the yeast and the fermentation process. The technical equipment, i.e. the selection of the stills for whisky production also plays significant role that should not be understated. However, the most important influence on the whiskey taste is the storage in oak casks. Bourbon barrels are used only once and are subsequently used extensively for aging Scotch whiskey.

In general the longer whisky is stored in the cask, the greater the influence of the wood on the taste of the whisky. The interaction of the spirit with the toasted wood and with the air that enters the cask from the outside plays a crucial role in bringing the character of the grain to perfection.

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