Scotch vs Bourbon: what's the difference?

Bourbon vs Scotch: what's the difference?

Scotch whisky is the biggest selling category of whisky in the world with Bourbon in second place. But what’s the difference between Scotch and its American cousin? This guide looks at the differences between Scotch whisky and Bourbon in terms of production and flavour profile.

To explore the differences between other types of whisky, check out The Whisky Club's guide to whisky definitions.

What is a Bourbon?

A Bourbon is a type of American whiskey made from a minimum of 51% corn. It is aged in new oak barrels for a minimum of 2 years if labelled as a "straight Bourbon". A Bourbon can be made anywhere in America, with the most famous brands originating in Kentucky.

What is a Scotch?

A Scotch whisky is a whisky that has been distilled and matured in Scotland. It must be matured for a minimum of 3 years in an oak cask. It will be made from a mash bill containing malted barley. There are 3 main categories of Scotch whisky:

• Single malt whisky - a Scotch made from 100% malted barley and distilled in a batch process in pot stills from a single distillery. Check out The Whisky Club's in-depth guide to single malts.
• Single grain whisky - a Scotch made from a mash bill of malted barley and a mix of other grains, usually distilled in a continuous still from a single distillery.
• Blended whisky - a mix of different Scotch whiskies from more than one distillery.

History

There are many similarities between Scotch whisky and Bourbon, as well as many differences.

The art of distillation no doubt hit the American continent with the first European settlers. Among them the Irish, Scottish and Dutch will have brought distillation know-how and equipment. Barley was a tough crop to grow on American soil, but the native Americans had been harvesting corn successfully, making it the grain of choice for American whiskey.

The term Bourbon came from the naming of a county in Kentucky. It was named in honour of the French royal family for helping fight the Brits. Whiskey made in this county was henceforth labelled Bourbon. This mark of quality was defined nationwide in the Bourbon act of 1964.

Scotch whisky was first mentioned in the Exchequer Rolls of 1494. Friar John Corr asked for 8 bolls of malt with which to make Aqua Vitae. 8 bolls of malt is enough to make a few hundred bottles, so we can safely say that whisky making knowledge had been around for a while before 1494.

From then on, the industry continued to evolve and change with the times. 1823 saw the licensing of distilleries; 1831 saw the emergence of bulk distilled grain whisky; 1850 saw the emergence of blended Scotch and the ability to marry whiskies for consistency; 1909 saw the first Scotch whisky industry definition. This was followed by a minimum age statement in 1915 and the emergence of the whisky definitions we recognise today in 1933. Since then the SWA has watched the category and ensured the history and traditions are kept alive whilst allowing the distillers to continue to innovate.

Both categories have evolved in separate ways: they use abundant and affordable local grains; they are distilled using distinct methods; and they mature in different environments in different types of casks. When you add all of this together, you realise that a Bourbon and a Scotch will taste very different in a glass.

Geography

Whisky can be made anywhere in the world, but Scotch and Bourbon have strict rules about where they can be made.

• Every drop of Scotch whisky must be distilled and matured in Scotland.
• All Bourbon must be distilled and matured in the USA. It doesn’t need to be made in Kentucky, but over 90% of Bourbon is made in Kentucky.

For a deeper dive into Scotland's regional differences, check out The Whisky Club's guide to the Scotch whisky regions.

Mashbill

All whisky is made from cereal grain, water and yeast. Deep dive into the whisky making process with The Whisky Club's guide to making whisky.

The recipe of grains used is known as the mash bill.

• Scotch whisky will contain a proportion of barley in its mash bill. This is because the enzymes present in barley are used to convert starch to sugar later in the process and it is illegal to add extraneous enzymes to the process.
  • Single malt whisky will be 100% malted barley
  • Single grain whisky will usually be made with ~90% corn or wheat and about 10% malted barley.
• The mash bill for Bourbon must be at least 51% corn. Many Bourbons will also contain barley for its enzymes, but the legal requirements for the Bourbon mash bills are defined by corn. In addition wheat can be added for softness and rye for spiciness.

The difference in mash bills mean that Bourbons will tend to be much sweeter than a Scotch whisky, even as a spirit. Whereas a Scotch will tend to have a malty backbone.

Mashing and Fermentation

These mash bills will have hot water added to them. This hot water will dissolve the fermentable sugars in the mash. The resulting run-off or slurry will then be cooled and have yeast added. This yeast will work like a catalyst turning fermentable sugars into alcohol.+

• Scotch whisky will run off a sweet liquid called “wort” from its mash bill. This liquid is all but saturated with sugar and is fermented into a beer known as “wash” at 8-10% alcohol by volume. The leftover grains (known as “draff”) will be removed before fermentation and fed to local livestock.
• Almost all Bourbon will be fermented all grains in. This means the whole mash bill will be transferred to a fermenter where yeast and “backset” (the American whiskey equivalent to “draff”) is added. It is low pH (high acidity) and helps control the bacteria in the fermenter. When you see the term “sour mash” on a Bourbon label, it is talking about the addition of “backset”. 15-30% of the backset is added to the next fermentation. The rest will be fed to local livestock. The resulting alcoholic slurry is known as “distillers' beer”.

The difference in mashbill and fermentation processes will impact fruitiness, spiciness and floral aromas to the final product.

Distillation

Distillation is the process of concentrating the alcohol from the wash into a spirit. The types of still and how they are run will all have a profound effect on the flavour of the final product.

Pot stills are traditional batch process stills. You load them with an alcoholic liquid, apply heat to the base. The alcohol evaporates up the still, leaving the water behind. The vapor then hit a condenser where it concentrates back into a liquid with a higher alcohol level. This process can be carried out multiple times to achieve a spirit of around 70-80% ABV.

Column stills are columns that have steam pumped into the bottom and wash pumped in higher up. The steam takes the alcohol molecules up the column and the water drops to the bottom. These can be run as a batch process, or continuously. If run continuously, as long as there is beer being pumped in with steam, then spirit will leave the other end. The height of these stills and number of plates will determine the purity and alcohol content of the final spirit. The most efficient column stills can take alcohol above 96% ABV.

Single malt Scotch whisky must be distilled in pot stills made from copper. It will be distilled at least twice and occasionally three times. The distiller will then select the “heart” of the run or the flavours he wants to capture for ageing on after the final distillation. His spirit will come off the still at about 72% ABV.
Single grain Scotch whisky is mainly distilled in column stills. The versions we have in Scotland are 4 storeys high with lots of plates. And the final ABV will be a maximum 94.8% ABV. There is a flavour difference between different grain whiskies in Scotland, but the high ABV means there is less complexity and mouthfeel. These whiskies are often used as the base for blended whiskies. This means more flavourful malts are added to grain whisky to build a complexity and unique flavour profile.
Bourbon can be made from both pot stills and column stills. The majority will use a column still first. This will result in a spirit that is about 50-70% ABV. The second distillation will then take place in a pot still, enhancing the spirit to a legal maximum of 80% ABV. Interestingly, the entire mash slurry from the fermenter will enter the first still. The resulting slurry at the bottom is used as the backset. This will not contain any alcohol.
So both Scotch and Bourbon distilleries will use pot and column stills, but they way they use them differs dramatically.

The Bourbon industry will use a column still to strip alcohol from the beer, then use a pot still to add weight and unique flavour.

The Scotch industry will use the stills separately, and blend the resulting liquids after maturation.

Casks

For both Bourbon and Scotch whisky, oak is the only wood that can be used for maturation. For more information, have a look at The Whisky Club's guide to casks.

In Scotland, whisky must be:

• aged in oak casks no larger than 700L
• for a minimum of 3 years.

In America, Bourbon whiskey must be:

• aged in brand new oak casks
• if classified as a “straight” Bourbon, it must be aged for a minimum of 2 years
• if aged for less than 4 years the bottle must carry an age statement
• In Scotland, the industry can use brand new casks (virgin oak); casks that have been seasoned with other products (most famously Bourbon whiskey and Sherry wine); and casks that have been used for maturing Scotch before (refill casks).

In America, the Bourbon industry need to use brand new (virgin oak) casks for the initial period of maturation. This ensures that Bourbons carry much more of an intense oak profile than Scotch. More vanilla, cherry, toasted oak and rich citrus notes.

Whereas a Scotch can use refill casks as part of their recipe to soften the intensity of oak influence.

Maturation Conditions

For those of you lucky enough to have visited Kentucky and Scotland, you will know the weather and climate are quite different.

Maturation conditions in Scotland are quite humid and temperate. This means the evaporation (or angels' share) from the casks is mostly alcohol. This leads to a Scotch decreasing in strength over time.
In Kentucky, the conditions are much hotter and drier. This means mostly water evaporates from the casks. This leads to a Bourbon increasing in strength over time.
These differences will affect the flavours a whisky will remove from the oak over time. Therefore the development of a Bourbon and the development of a Scotch during maturation are different.

Maturation Time

To call anything a whisky it must spend some time in oak casks.

• Bourbon has no minimum ageing requirements.
• Straight Bourbon must be aged for a minimum of 2 years in an new oak cask in America. If the whiskey is younger than four, it must feature an age statement on the label.
• Scotch whisky must be matured for a minimum of 3 years in an oak cask in Scotland

The warmer and drier conditions in Kentucky coupled with the much more active new oak casks cause the Bourbon to extract much more colour and flavour from their casks in the same time as a Scotch whisky. The conditions will also cause much more evaporation in a Kentucky warehouse compared to a Scottish one.

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FAQs

What is the legal definition of Bourbon?

According to U.S. law, Bourbon must be:

• Made in the USA
• Contain at least 51% corn in the mash bill
• Distilled to no more than 80% ABV
• Aged in new oak barrels
• Bottled at no less than 40% ABV
• If labelled “straight Bourbon,” it must be aged for at least 2 years

What is the legal definition of Scotch whisky?

Scotch must be:

• Made in Scotland
• Distilled from water, malted barley (and optionally other grains)
• Distilled to no more than 94.8% ABV
• Matured in oak casks no larger than 700L for at least 3 years
• Bottled at no less than 40% ABV

Is Scotch whisky always smoky?

No. The majority of Scotch distilleries don’t make smoky whisky. As part of the drying process when malting barley, a minority of Scotch distilleries will use peat smoke to add flavour. The rest use hot air or smokeless fuel. So, peat is an outlying flavour for some Scotches that is not used in Bourbon production, but it is not present in all Scotch.

For examples of smoky Scotch, we've written The Whisky Club's guide to the best peated whiskies and The Whisky Club's guide to Islay whisky

What are the main differences between Bourbon and Scotch.

Bourbon is made primarily from corn and aged in new oak barrels, giving it a sweeter, oak-forward profile. Scotch is made from malted barley and mostly aged in used or seasoned casks, resulting in a more complex, integrated and malty flavour. Occasionally Scotch will be smoky or peaty.

Does Bourbon need to come from Kentucky?

No, Bourbon can be made anywhere in the USA, but over 90% is produced in Kentucky.

What does sour mash mean in Bourbon production?

Sour mash refers to the addition of “backset”. Backset is a portion of spent mash from a previous batch. It can help control fermentation, acidity and maintain consistency.

Why is Bourbon often sweeter than Scotch whisky?

Bourbon’s high corn content and use of new oak barrels contribute to its sweeter flavour profile, with notes of vanilla, caramel, and toasted oak.

Is Bourbon stronger than Scotch?

Not necessarily. Both can be bottled at various strengths, but Bourbon often increases in ABV during maturation due to drier climate conditions, while Scotch typically decreases in ABV. Both will have water added before bottling to achieve consistently unless labelled Cask Strength or Barrel Strength, so the majority of Bourbon and Scotch are the same strength, often 40-43% ABV.

Does The Whisky Club feature Bourbon whiskies?

Yes! The Whisky Club offers curated releases of both Bourbon and Scotch, including exclusive bottlings created just for our Members.

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