Whisky is an aged spirit made from grain. On the face of it, it’s really rather simple. But dig a bit deeper and the materials that go into whisky are rich and varied – with different production requirements.
The grains used in whisky are generally determined by two factors: the choice of the whisky-maker depending on desired flavour, and geography. The latter is impacted by both availability and also the law. Many whisky categories produce according to legislation that requires them to use certain grains.
Globally four main grains are used in whisky production: barley, corn, rye and wheat. Experimental producers are using others, too.
The malting process
Malting is a commonly used term, but often misunderstood. It’s a technique associated with barley, although producers are now innovating and malting other crops, too. Simply put, the malting process is all about tricking the grains into growing.
The grains are placed in a warm location, repeatedly soaked, and then eventually start to germinate. Shoots and roots start to grow, and the grains are turned to stop them matting together. Once the enzyme-rich sprout reaches a certain length, growth is stopped by using heat. This process is known as kilning. Most maltsters use a clean fuel that won’t impart any flavour at all. Others choose to use peat for this process, resulting in a smoky, earthy whisky.
The whole point is to make the enzymes in the plant available to turn its own starches into sugar. After this point, the whisky-maker will mill and mash to produce a sugary liquid that goes on to fermentation and eventually distillation. For unmalted grains, exogenous enzymes are added to the raw materials. By malting barley (and occasionally other grains), the whisky-maker lets the raw materials do the work.
The malting process is so effective that even around 5% malted barley in a mashbill – or grain recipe – provide enough enzymes for the entire batch.
Whisky made using barley
In whisky-making terms, malted barley has long been associated with Scotland and Japan. But today, distilleries all over the world are producing single malt whisky.
100% malt whiskies are typically full of character. Flavours will vary enormously, but generally there’s a big, round mouthfeel with fruity, toasty, citrus notes. Whiskies made with 100% malted barley can feel a bit thicker than some other styles.
It’s also worth noting that some countries, especially Ireland, make some whiskies with unpeated malt. This tends to have a greener, oilier quality and is quite distinct.
There are many different barley strains. Modern distilling has relied on a few commercial types known for their high yields. Increasingly, smaller and craft producers are experimenting with older, heritage barleys which don’t produce as much alcohol, but do offer distinct flavour profiles.
Whiskies made using corn
Corn whiskies have strong associations with the US. Bourbon is made across the whole country, with mashbills containing at least 51% corn. The rest can be made up of any whole grain, but producers will usually include some malted barley for its enzymes.
A separate and important category in the US is corn whiskey. These spirits must have a mashbill made of at least 80% corn.
Typical flavours from corn whiskies include vanilla, cinnamon, popcorn, coconut, honey and a nuttiness. While it feels sweeter than other categories, no sugar is ever added. Corn whiskies can have a softer mouthfeel.
Whiskies made using rye
Another quintessentially American whiskey category, rye has become known for its robust, spiky texture and its excellence as a cocktail ingredient.
Ryes made in the US must have a mashbill of at least 51% rye. Whiskies made further afield using the grain don’t have the same restrictions.
Scandinavia has emerged as a major rye whisky producer, and distilleries in Scotland are even experimenting with the grain.
Rye whiskies can feel quite ‘hot’ in the mouth and many have a distinct green, almost menthol note to them.
Whiskies made using wheat
Wheat is often used as a component part in bourbons and other whiskies, but it is possible to find 100% wheat expressions. In the US, they must have a mashbill of at least 51% wheat.
Wheat whiskies can be quite aromatic in flavour, offering soft spices, cinnamon, cooked fruits and bread-like notes. They can also have a softer mouthfeel than other grain varieties.
Other grains
The rules on whisky raw materials state whole grains must be used. There are producers out there experimenting with all manner of mashbills to see what flavour components they can create.
Recent innovative examples include whiskies made from quinoa, buckwheat, oats and millet. Each one will bring their own flavour characteristics to a whisky.