I am always asked what the difference is between Bourbon and Scotch whiskeys. The answer I give is always “All Bourbon is whiskey, but not all whiskey is Bourbon”. I follow this with a description of the regulations to make Bourbon, however I thought it might be bice to look at the two whiskeys through the six sources of flavor. Now I am not an expert on Scotch by any stretch of the imagination and I welcome any comments on this comparison from Scotch enthusiasts.
Bourbon: Bourbon has to be at least 51% Corn. It can be 100% corn if the distiller wishes, but it has to be a majority corn based beer. The distiller usually uses rye or wheat as a flavor grain and malted barley for conversion from starch to sugar, but low amounts of barley are allowed with the addition of manufactured enzymes for the conversion. This gives Bourbon distillers a large range of flavors they can produce for their Distiller’s Beer.
Single Malt: As the name implies, Single Malt Scotch is made from malted barley. There is not a lot of variation of flavor from distillery to distillery from the grain itself. Instead the Scottish distillers use the malting process itself to give variation in the grain flavor. They will use peat smoke in varying degrees to flavor the malt. I don’t know if any Scotch distillers are doing so, but they could use brewer malts such as chocolate malt to alter the flavor of their Distiller’s Beer.
Bourbon: Limestone water is the key to good Bourbon in Kentucky, but any iron free water will work. Many big city distillers are using RO or Reverse Osmosis water to make their beer because the ground water is too polluted to use for human consumption without treatment. Other distillers are using water from deep wells or springs.
Single Malt: Once again the fact that it is iron free is an important factor. Some Scottish distillers are getting their water from granite fed springs while others are getting it from peat bogs and the water looks like coffee and gives the beer a heavy peat flavor.
Bourbon: Bourbon distillers have always known that different yeasts make different flavors and made a point to keep their own yeast strain alive for future years. For some families this became a point of pride and a family secret as to where and how the yeast was first propagated. A prime example of yeast is the Four Roses distillery with their five different yeast strains that they keep and use with two different mash bills to create ten different Bourbons.
Single Malt: Up until a fairly recent time, Scottish distillers paid little attention to yeast and its flavor value. Michael Jackson wrote in the 1980s about Scotch and barely mentions yeast, but in his 2005 book “Whiskies of the World” he does mention that the Scottish distillers are beginning to pay attention to yeast and the flavor component derived from fermentation. To this day, you rarely see anything written about yeast and Scotch production.
Bourbon: Bourbon has a maximum distillation proof of 160 and the industry average is closer to 140. The lower distillation proof than that of other whiskeys allows more flavor to come through from the first three sources of flavor. Bourbon also uses the column still with a pot still doubler or a thumper with varying degrees of copper used in making the stills. Recent artisan distillers are often using hybrid stills that are a pot still with a small rectifying column attached. There is a huge variation in the stills used to make bourbon.
Single Malt: The traditional still for Single Malt whisky is a copper pot still. The only variation comes in factors such as the shape of the still or the length of the goose neck coming off the still. The maximum distillation proof is the legal high of 180 even though I doubt very many distillers go that high.
Bourbon: Maturation is a huge difference in these products. Bourbon has to be aged in new charred oak barrels with a maximum entry proof of 125 with only pure water added to adjust the proof. This leads to a lot of barrel flavor in a short time with Bourbon maturing in as little as two years, the time required to be a Straight Bourbon. The variations between distilleries comes in many forms that include char levels in the barrels, barrel entry proof, type of warehouse (iron clad or Masonry), number of floors in the warehouse, where the barrel is placed in the warehouse, whether the warehouse is heated in the winter, is the ware house palletized or are their barrel racks. Climate is important too as the hot summers and cold winters of Kentucky are very different from warehouses found in cooler climates such as upper New York State. Warehouses found in a city will age whiskey different than warehouses found on a hillside out in the country. There is a huge variation in the maturation process in the Bourbon Industry.
Single Malt: Single Malt can use a wide variety of barrels for maturing their whisky. Used cooperage is not only allowed but it is the most common cooperage found in Scottish warehouses. Indeed there are many used Bourbon Barrels being used to make Single Malt Scotch. Many Malts market the fact that they are using Sherry or Port or even Bourbon barrels to make their whiskey. They depend upon these used barrels to pass along flavor from their previous use to the whisky. There is no upper limit to barrel entry proof and indeed many that I have heard range in the mid 130s for entry proof. The weather in Scotland is much cooler and damper than in Kentucky causing the aging whisky to decrease in proof over the years. The warehouses usually don’t have the rack system found in the United States with only single story warehouses where the barrels are either stacked upon top of each other or palletized. The big variable for aging is location as there are many warehouses near the sea, allowing the whisky to get a hint of the salty brine from the sea in the maturing whisky.
Bourbon: Straight Bourbon has to be bottled at a minimum of 80 proof with nothing but pure water added to adjust the proof. The amount of filtration is the big variable in flavor other than bottle proof. It is possible to combine multiple bourbons to adjust the flavor such as Four Roses Yellow label which is a combination of all ten Bourbons made at the distillery, but this is not a common practice.
Single Malt: Single Malt has to be bottled at a minimum of 80 proof and to be the product of a single distillery. They can add caramel coloring to bottling and many do. There are a variety of levels in filtration as well.
There are a lot of differences in these two products. Both are fine whiskeys and deserve respect. I would say that neither are superior to the other as they are both very different. To me it is like eating steak or pork chop, it depends what you are in the mood for as to which is better on that day. I love Bourbon but I also like Single Malts. I never turn down a glass of Talisker in any of its variations. I advise people to enjoy a glass of both of these types of whiskey from time to time.
June 26, 2017 at 12:35 pm
You are correct, there isn’t a ton of variation in yeast selection as amongst most Scotch producers, although that trend seems to be growing. There are some grain variations, most notable Glenngoyne using the old “Golden Promise” barley. The big variations come from a combination of factors, mostly whether the grain is peated and to what phenolic range it is if it is peated at all (not all Scotches are smokey, lot of highland and lowland stuff is fruity!). The next factor is the length of fermentation, whether that fermentation is long 5-7 days or short 3-4 days determines whether the product will be more “fruity” or “meaty” (sulpherous, but in a good way). The stills themselves are the most important factor, unfortunately this is something most U.S. distillers miss out on, but the shape, height, width, and depth of the still all effect flavor dramatically depending on how much copper conversation and reflux is forced on the product. Shell and tube condensor vs worm/serpentine is a major factor as well and whether the condensor might be stainless or copper. Most Scotch stills are also paired off with one stripping still and one spirit still, designed to compliment one another, again, not often seen in the U.S.
June 26, 2017 at 9:15 pm
A few more notes from the Scotch whisky side:
Grain: Glenmorangie (and almost certainly others) have done some playing with brewers’ malt – one of the components of Glenmorangie Signet is a single malt made with some chocolate malt in the mix.
Water: Peaty water isn’t really peaty and doesn’t give the beer a peaty flavour, but I’ve mentioned that elsewhere 🙂
Yeast: It’s endlessly annoying to me that there’s not more written about yeast in Scotch whisky. However, fans of whisky from ye olden dayes are starting to make more noise about yeast and there are more distillers experimenting these days. Fermentation times are also picking up more notice, but again, it’s only the geeks and folks producing who are saying much, and generally not in public.
Distillation: The legal maximum is 189.6 proof (94.8% ABV), and most grain whisky (distilled in a column still in vast quantities) gets up to that sort of level – single malt made in pot stills doesn’t, as you said, get up that high. Especially not the cuts that are taken for maturation.
Maturation: Standard barrel entry proof across most of the industry is 127 proof (63.5% ABV), but some folks do fill at higher strengths – Bruichladdich famously fill at still strength because they ‘don’t want to mature water’.
Casks aren’t only palletised or stacked on top of each other, you also get racked warehouses, where rows of barrels are stored on their sides in racks. These can go very high, although generally not as high as multistorey bourbon warehouses.
The location is also not as big a thing as the marketers want you to believe. Nowhere in Scotland is that far from the sea and lots (most?) of the maritime whiskies are matured in warehouses in the central belt, far from the distilleries where they were made. Terroir almost certainly has some influence – move your distillery somewhere else and your whisky probably won’t taste the same – but not really in adding seaside flavours to your dram.
June 28, 2017 at 9:31 pm
Interesting article. One of the things I’ve always wondered about are the marketing terms “small batch” and “single Barrel “. I say marketing terms because the distillers are fighting a regulation to define small batch as less than 5300 gallons.
And since most single barrels taste pretty much like the next SB (within brand) I’m hesitant to believe that all the bottles of Single Barrel come from a Single Barrel. Particularly those of the 18-25 year old variety.
Just me not believing everything on a label. Like the bottle of Taylor single barrel, with no reference to Barrel number.
November 20, 2019 at 6:26 pm
I never really understood the difference between Bourbon and Scotch whiskeys, but your blog made it clear for me. Now I know what I need to get when I go out with my friends.