If you trace the lineage of the most popular spirits in the world far enough, you’ll invariably end up in Scotland somehow. Distilling has been a way of life in the region for centuries, and the techniques pioneered there have been adapted and re-used around the world (for example, in American and Japanese whiskey). While the distilleries have gotten a bit more modern over time, the processes they use have remained fundamentally the same.
In Scotland, the definition of a “scotch whisky” is legally defined and tightly controlled. But there are still some options that allow each distillery to forge their own path:
Nearly all spirits distilled in Scotland include malted barley (and we’ll get to the reason for that in a moment). In general, malted barley is simply barley grains that have been allowed to start to sprout. The grains are soaked in water and then laid out in a malting room for some period of time while the seeds inside the barley start to germinate.
Now, there’s a very important reason for that germination. Seeds are made up of complex carbohydrates, which are intended to be used as food for the new plant. But plants (and yeast, for that matter) can’t directly use carbohydrates — it needs to be broken down into simple sugars for the plant first in a process called “enzymatic hydrolysis.” When the new seed germinates, it releases natural enzymes that break down the complex carbohydrates into simple sugars that it can then use.
For Scotch Whisky, only natural enzymes are allowed to be used to convert complex carbs into sugar, which is why you’ll see malted barley used fairly universally.
The trick here is that we want this all to happen, but we don’t want the new plant to eat all the available sugar before the yeast can. That sugar is what our yeast is going to eat and turn into alcohol, so we need the barley to stop growing. This is accomplished by heating or “kilning” the malted barley, which raises the temperature of the seed and stops it from growing any further. Most malting facilities will use a clean, modern source of heat such as natural gas, but the traditional method of heating the barley is with peat — a natural fuel that creates a distinctive smoky aroma. Some distilleries still use peat smoke during the kilning process to impart that smoky flavor into their spirit.
For Single Malt Scotch Whisky, 100% of the raw materials must be malted barley. Adding smoke to the kilning process is optional for distillers.
The other kind of spirit that is commonly produced is Single Grain Scotch Whisky. In this case, the “single” refers to a single distillery producing the spirit (not that only one kind of grain is used). Most of these spirits also use malted barley in their mixture, as the malted barley will provide the enzymes needed to break down the starch in the other grains and make their sugar available to the yeast. There is no real restriction on the number or kind of grains that can be added, just that they are indeed grains.
For grains other than malted barley, typically they are milled or crushed and then cooked in a warm bath before moving to the next step.
Now that we have a soup of sugary liquid and grain remnants, it’s time to start the fermentation process. This is where yeast (a single cell organism) eats the sugar in the solution and produces ethanol (alcohol), carbon dioxide, and heat.
Typically, distillers will use cultured, lab grown yeast for their fermentation process. These cultured yeasts are grown and selected for their ability to create alcohol and for their specific flavor profiles, ensuring that the flavors are consistent from one distillation run to the next, but there is no restriction on using wild (ambient) yeast for distillers.
Fermentation will typically take a couple days, and once complete the fermented liquid (called the “wort”) is drained from the tank. Typically distillers will spray down the remaining solid matter in the tank to make sure all of the available alcohol has been extracted (called “sparging”).
With a traditional scotch whisky distillation, there are two distilling runs that take place. Sometimes distillers will use a single pot still for both processes, other times there are two or more stills used. Stills are usually constructed from copper, which is a component that reacts with the vapor and liquid in the still to remove unpleasant sulfur compounds that can taste pretty awful if not removed. The vapor produced in the still is commonly cooled in a “shell and tube” condenser, which is where pipes containing the hot gasses are cooled by a water jacket to force them to condense back into a liquid. This container is also usually made out of copper for even more sulfur reduction.
In the first distillation, pretty much the entire point is to strip out all of the water from the wort they got out of the fermentation process. This is sometimes called a “stripping run” and if a dedicated still is used it’s called a “wash still”. There isn’t much care or attention paid to isolating out specific components at this point, and the results are called “low wines”, as they have a lower alcoholic content than the final product. What’s left in the pot is called “pot ale” and is discarded.
The low wines are then put into a charging vessel, some other components from the second distillation are added (we’ll get to that in a second) along with some water to reduce the overall alcohol content in the mixture. This process causes some of the less desirable components (fusel oils) to fall out of solution and get stripped off before the mixture is added to the second still.
The final distillation (typically in a “spirits still”) is much more closely monitored. The first thing that comes out of the still is called the “heads” of the distillation run, which mostly contains highly volatile materials with a lower boiling point, things like solvents and other nasty components. At some point, the distiller decides that the heads are finished and what’s coming out of the still is the spirit they want to capture, which is called the “hearts” and they start capturing that liquid into barrels. When all of the alcohol they want to capture has been extracted from the liquid, they make one more “cut” to stop barreling the spirit and they let the rest of the mixture (called the “tails”) flow until the stream of liquid stops.
These two unwanted cuts — the heads and the tails — are what is added back to the charging vessel for the next distillation run. What’s leftover in the pot from the second distillation is called the “spent lees” and discarded.
Not all scotch whisky uses a pot still for their production. Some use a column still or a “continuous still” for their process, especially in grain whisky. But in either case, the legal maximum alcohol content for the spirit that they create is 94.8% alcohol by volume.
Once the whiskey has been created, by law it must be aged in oak vessels (less than 700 liters in size) for a minimum of three years. There’s a lot of options here, especially since scotch doesn’t have the same requirement as American bourbon to use a new barrel every time. In fact, the majority of barrels used for scotch maturation are previously used American bourbon barrels that have been disassembled and re-constructed to the distiller’s specifications.
Different distillers will have different opinions on the best way to age their spirits. Some will use American oak, others European oak. Some will only age a short period of time, while others will let their whiskey rest for decades. And the choice of location for the warehouse also has a huge impact on the final product, with hotter climates having a more pronounced impact than cooler climates.
Once the spirit has been aged, it is finally time to bottle. In general, most scotch whisky will be a blend of multiple different barrels to get the right flavor profile. By law, the only thing allowed to be added to the spirit is water (for proofing the spirit to the right alcohol content) and caramel coloring, specifically E150A caramel coloring.
- Single Malt Scotch Whisky will be a whisky made from 100% malted barley that is produced by a single distillery.
- Single Grain Scotch Whisky is a whiskey made from a mixture of grains, usually containing some proportion of malted barley, that is made from a single distillery.
- Blended Malt and Blended Grain Whisky is a blend of the respective types of whisky from multiple distilleries.
- Blended Scotch Whisky is a blend of anything from multiple distilleries.
- Whisky with an Age Statement will indicate the age of the youngest drop of spirit in that bottle, but often includes much older components for flavor.
By law, the bottle of whisky must have a minimum of 40% alcohol by volume, and a maximum of 94.8%.
Now that you can decipher what some of those words on the bottle mean, it’s time to start trying out the different varieties and find a favorite! Even with all the requirements there’s still a ton of variation and choices for distillers to make, meaning you can always find something unique and interesting in just about every brand you try. Check out our full list of reviews here — and happy exploring!