The most important ingredient for Bourbon whiskey is grain. It is one of the main components, along with water and yeast cultures. At least 51% of the mash of a Bourbon must consist of corn. Other prevalent grains are rye, barley, and wheat. They are added to the Mash Bill in varying proportions depending on the recipe. The composition of the mash bill is one of the decisive factors for the character and taste of the whiskey.
What is Bourbon Whiskey made of?
No matter if Bourbon Whiskey, Rum, or Scotch Whisky – the mash is indispensable for the production of alcohol. The mash consists of an essential substance containing sugar or starch, for example, various grains in whiskey. The grain is mixed with water and yeast, fermented in this way and later distilled into a spirit. The mash is, therefore, the starting point of every alcohol, including American Bourbon Whiskey.
Not all mashes are the same. The composition of different types of grain has an essential influence on the later character and taste of the whiskey. That is why every distillery has its own Mash Bill recipe, which is strictly guarded and strictly adhered to obtain the most consistent spirit possible.
The composition of the Mash Bill in Bourbon Whiskey
Although each distillery has its own Mash Bill recipe, there are also legal requirements that whiskey producers must comply with. With Bourbon Whiskey, for example, the mash must consist of at least 51% corn. In most cases, however, the proportion of corn is even higher, up to about 80% corn in the mash.
The remaining composition of the Mash Bill can be freely designed by the master distillers. Bourbon whiskeys, for example, often contain the classic whiskey cereals barley and rye, and more rarely wheat, in addition to corn. Even oats are a possible addition. The distillers are relatively free to choose, but each grain brings its characteristics to the finished whiskey.
How the cereal varieties influence the bourbon?
As corn is the main ingredient in Bourbon Whiskey, it should be thought that it is also decisive for the later taste of the Bourbon Whiskey. However, this is only partially true. When the whiskey is freshly distilled (so-called New Make Whiskey), you can still clearly taste the corn characteristics, the other grain flavors are rather hidden.
However, the longer the whiskey is stored in oak barrels, the more the corn disappears. The other grains and the characteristics of the barrel wood become more apparent.
Corn makes the bourbon “buttery” and “nutty”.
Although the “corn taste” supposedly disappears during storage, it is nevertheless a contributing factor to the later Bourbon taste. Corn gives the Bourbon a subtle buttery note.
Together with the storage of the whiskey in American oak casks, vanilla and caramel aromas are given to the Bourbon. Along with the corn, this results in a nutty taste. Corn does not bring a real taste characteristic of its own into the Bourbon but instead supports the development of other flavors. Furthermore, corn is very starchy, so that a lot of alcohol can be produced from it. This is another reason why corn is so important for Bourbon whiskey.
The special enzymes of barley
By using malted barley in the mash, malty aromas and the taste of chocolate and pastry are added to the Bourbon whiskey. But that is almost irrelevant. Because barley is also of decisive importance for the function of the mash, the fermentation process, and the later whiskey for an entirely different reason.
Malting barley contains special enzymes that help to convert the starch contained in the mash into sugar. It makes it easier for the added yeasts to ferment the sugar into the so-called “Distiller’s Beer”, from which the whiskey is later distilled. Barley is not so much for its taste but rather for its enzymes that are decisive for the production of whiskey and is often used.
The flavor carriers rye and wheat
Since corn and barley are only used for the shell of the Bourbon, more cereals are needed for the taste. Thus, rye and wheat are often included in the Mash Bill. They are the ones who put their distinctive stamp of flavor on the Bourbon.
Rye is known from the Rye-Whiskeys ( at least 51 % Rye in the mash), which generally taste very spicy and intense. Aromas such as nutmeg, clove, cinnamon, and herbaceous notes can be attributed to rye. These flavors are further enhanced by storing the whiskey in freshly burnt American oak casks.
Even though wheat is now used less frequently in Bourbon whiskeys – in these cases, one also speaks of “Wheated Bourbon” – it is still one of the classic whiskey grains. Already in Mash Bills from the 19th century, there was a part of wheat.
Bourbons with a wheat share usually taste slightly sweeter. However, this is not because wheat is a sweeter grain. Unlike rye, it is only milder and less dominant in taste. More sweet aromas of the wood, such as vanilla and caramel, come through and make the whiskey seem sweeter. Well-known Bourbon whiskeys with wheat content in the mash are, e.g., Maker’s Mark and Old Fitzgerald.
How important is the mash for the Bourbon taste?
The composition of the mash has an important part in the taste of the later Bourbon whiskey. It is estimated that about 20% of the flavor is due to the selection and composition of the grains in the mash. A further 10% of the taste properties are due to the yeast and the fermentation process, i.e., they are also indirectly linked to the grain.
But also the technical equipment, i.e., the selection of stills for the production of whiskey plays an important role with an estimated 20%. The most important influence on the whiskey taste, however, is the storage in oak barrels. The proportion is rated at up to 50 %.
But it is also true that the longer the storage in barrels, the higher the influence of the wood on the taste of the whiskey. The interaction of the spirit with the toasted or charred wood and with the air that comes into the cask from the outside helps decisively to bring the grain character to perfection.
Bourbon production: From the mill to the mash
However, before the mashing of the whiskey can be started at all, the grains have to be ground into a kind of flour, or previously (e.g., barley) malted. In malting, the barley is made to germinate to convert the starch it contains into sugar. The production process at all is quite similar to the way how single malt whisky is made.
Since the ability to grind grain is so crucial for whiskey production, it is not surprising that the German settler Jacob Böhm (the founder of Jim Beam) was originally a miller and not a whiskey distiller. One thing led to another in this case. And even today, this vital step is still carried out in the distilleries themselves, so it is an integral part of the whiskey industry.
After the grains have been processed into a coarse flour, they have to be boiled so that the sugars they contain are better available for fermentation by yeast cultures. For the cooking process, pure water is added to the mash tun, which has as little iron content as possible. As Kentucky has a lot of limestone underground, there is a lot of clear water here, which is suitable for Bourbon production. Also, for this reason, many famous bourbons come from this American state.
However, the grains are not merely thrown “into a pot”. Since corn is much harder than the other grains, it needs more time to be cooked. The different grains are therefore added to the Mashbill later.
Fermentation of the mash by yeast cultures
When the grain mixture has been filled into the huge fermenting vats, the yeast is also added. A small package with a few crumbs like for baking a cake is, of course, not enough. For a full fermenting vat, up to 30 kilos of yeast culture is quickly needed.
But not all yeast is the same. So every distillery has its yeast strain, which the Bourbon Master Distiller keeps like his SUV. Because the yeast strain plays an essential role in the later taste of the Bourbon, in some cases, the influence of the yeast on the taste is even estimated to be 10-15%. The loss or contamination of the yeast cultures would, therefore, be a bitter blow for the distillery, as the individual taste and character of the whiskey could no longer be produced.
Depending on the external conditions (e.g., season), it takes between 3 and 5 days until a massive vat with mash is completely fermented. During the fermentation, the processes in the vat change continuously. The surface of a freshly prepared fermentation vat is still cool. The yeast is hardly active (does not bubble), and the contents of the container taste sweetish. At the peak of fermentation, however, the vat bubbles very vigorously, and the yeasts produce noticeable heat (up to 100 Fahrenheit / approx. 38 degrees). At the end of fermentation, nothing bubbles anymore; the mash tastes sour and has an alcohol content of 8-12%. So about as much as a strong beer.
The distillation of the Bourbon whiskey
After the end of the fermentation process, the Bourbon whiskey is finally distilled. In the whiskey industry, a Column Still is almost exclusively used for this purpose, which can take on enormous proportions. In contrast to the pot stills of the Scottish whiskey industry, they can be used for continuous distillation. Distillation is carried out in two stages. With the first distillation process to the so-called Low Wines (with about 20%) and in the second distillation process to the High Wines (mostly 60-70%), Bourbon whiskey may by law not be distilled higher than 80%. After the distillation, the whiskey is finally transferred to the cask storage.
The storage of Bourbon in fresh oak barrels
Bourbon whiskey may only be stored in fresh charred American oak barrels. By law, the Bourbon may not be filled into the barrels above 62.5%, so it is diluted with water to the necessary level and then stored in the huge warehouses. The storage time of Bourbon-Whiskey differs a lot because there is no regulation for this.
If the new whiskey has seen an oak cask from the inside (and meets the other regulations), it is a Bourbon. However, there are other special features. A Straight Bourbon must be aged for at least two years. On Bourbons, under four years of age, an age indication must be given on the label. No period on the label, therefore, means that the bourbon has spent at least four years in a wooden barrel.