An introduction to bourbon whiskey: America’s great spirit – Part 1

Bourbon whiskey is a uniquely American spirit that, along with my homebrewed cider, has become my go-to alcoholic beverage. If you just want a list of great bourbons to try, skip to my recommendations in Part 2.

What is whiskey?

Whiskey is any fermented grain beverage (aka beer) that has been distilled, which concentrates its alcohol and removes the sugars and many other flavors of the original product, but keeps enough of them to still have the distinctively sweet whiskey flavor. Fermented fruit beverages, such as wine or cider, that are distilled are called brandy or eau de vie. The latter is French for water of life, and that same phrase in Latin, ‘aqua vitae’, became uisce beatha in Gaelic, which eventually turned into the English word ‘whiskey’.

Similar to brandies like Cognac, whiskies today are almost always aged a few to several years in oak barrels. Oak happens to be an excellent wood for barreling spirits because it doesn’t leak or poison you, and aging in wood improves the flavor by contributing toasty, wood-y & vanilla-y notes. Charring the barrel, which is required for bourbon, also mellows and purifies the whiskey, removing harsher flavors over time, as well as adding unique flavors. Think of this charred inner layer of the barrel as a charcoal filter that also adds deliciousness. Mmmm….

Non-American Whiskies

Scotch, Irish, and Japanese whiskies are made principally of barley, which is also the primary grain in beer. Malt whiskies such as Single Malt Scotch are made entirely of malted barley, whereas blended whiskies can be made of neutral grain spirits (aka vodka, usually made from corn because it’s cheap) or other grain spirits. The ‘Single’ in Single Malt Scotch refers to the requirement that the spirit be made in one distillery over one distilling season (as opposed to combining whiskies from multiple distilleries or whiskies from different years of distillation.) Canadian whiskies are somewhat similar to American ones in the grains they use, especially their frequent use of rye, but they are often blended with tasteless neutral grain spirits, and thus not as characterful as American whiskies.

What is bourbon whiskey?

American whiskies include bourbon, Tennessee, rye, wheat, and malt whiskies. Depending on the style, they are made of corn (maize to those of you outside of the United States), rye, barley malt, and sometimes wheat. Bourbon is the most popular type of American whiskey, and it must be made in the US to be called bourbon (but not exclusively in Kentucky, where most whiskey comes from, which is a common misunderstanding.) Bourbon is required by law to be made of at least 51% corn, with the remainder being rye, wheat, or barley. In practice, most bourbon is made with 60 – 80% corn, 10 – 20% rye (sometimes substituted with wheat instead), and 10 – 12% malted barley. Malted grains convert the starches in the other grains into sugars during the beer brewing process so that the yeasts can turn those sugars into sweet, sweet alcohol.

Bourbon must also be aged in newly-charred oak barrels. Since these barrels can only be used once for bourbon, they are often sent to Scotland to be used to age Scotch afterwards. The fact that they are used barrels is why Scotch has a mellower wood flavor profile than bourbon.

There is no minimum aging period for plain ‘bourbon’, but most whiskey sold is ‘straight whiskey’ (or ‘straight bourbon whiskey’), and that must be aged for at least 2 years, and must display an age statement if it is aged for less than 4 years. So, if you see something like ‘Kentucky straight bourbon’ with no age statement such as Jim Beam white label, you’ll know it’s bourbon made in Kentucky that’s been aged for at least 4 years. (And probably exactly 4 years, since it’s expensive to age booze!)

You can think of bourbon as the ‘mostly corn’ American whiskey. Rye whiskey is essentially made by the same process, but with a minimum of 51% rye, and the remainder corn or barley. Wheat whiskey is 51% wheat, and so on.

The one quirky exception to this 51% rule is the rarely-found corn whiskey, which has to be at least 80% corn. Another quirk of corn whiskey is that it can be unaged, but if it is aged, it must not be aged in newly-charred barrels, but in used or uncharred oak barrels.

Bourbon must also be distilled to no more than 80% alcohol by volume (aka 160 proof), put into the barrels at no higher than 125 proof (62.5%), and bottled at no less than 80 proof (40%.) Distilling to a lower proof means that more flavor stays in the spirit, whereas neutral grain spirits like vodka are distilled to much higher proof (95%, say) which ensures that pretty much only alcohol is coming out of the still, and the majority of the grains’ flavor is left behind (sad.)

What determines the flavor of American whiskey?

Age and charred wood

The length of time spent aging in the newly-charred oak barrel makes a big difference in the flavor (and price) of bourbon. While Scotch can age for as much as 25 years or even longer in its used barrels, with some notable exceptions, bourbon generally gets too much wood flavor from the newly-charred barrels if left in them for more than 8 – 12 years. You rarely see any bourbon advertised as older than that.

Unlike wine or beer, distilled spirits do not really change once bottled, so you’re paying for the time spent in the wood, not the glass. Sugars and other flavoring compounds formed in wood when toasted and charred contribute to the vanilla, smoke, tobacco, oak, and some other flavors found in bourbon. Barrels can be charred to different levels of burned-ness, but most whiskey barrels are either a #3 or #4 char, which is the middle of the #1 – #7 scale used, #1 being the least charred.

Temperature variation

The environment that the whiskey is aged in also makes a big difference. Temperature change is key as hot summers and cool nights apparently press the whiskey in and out of the wood as the liquid expands and contracts, resulting is quicker/superior aging. Thus, the top and outer racks in the large whiskey barrel warehouses known as ‘rackhouses’ yield the most flavorful whiskey. This is why hot, dry places like Kentucky are well-suited to whiskey production whereas coastal location like Seattle or San Francisco are not. Plus, huge rackhouses require a big footprint, so cheap land is a plus.

Bourbon barrels aging in a Kentucky rackhouse


The type and proportion of grains used in the whiskey also make a difference, with corn giving a sweet flavor, which is either balanced with the spiciness of rye, or allowed to come through with the mellowness of wheat. Barley is a small component of bourbon, and thus probably doesn’t contribute too much flavor, but I would guess it’s a sweet flavor too like that of Irish whiskey. Rye whiskey is therefore generally ‘spicier’ and drier-tasting when compared to bourbon, and corn whiskey, which is often almost entirely corn, might be very simply sweet, but with little of the complexity found in bourbon or rye. Roughly 95% of the bourbons you find on the shelf will be corn + rye whiskies, and only a few, notably Maker’s Mark, Larceny, W.L. Weller products, and most famously, Pappy Van Winkle bourbon, will be corn + wheat whiskies. Some distilleries have recently experimented with ‘four grain’ bourbons, meaning they contain corn, rye, barley, AND wheat.


The yeasts used by the distillery to ferment the corn and rye-based beer also contributes a lot of flavor, and are closely guarded by each of the major distilleries. These yeasts have often been handed down over many years, similar to an heirloom sourdough or beer yeast. The distinctive spiciness present in Wild Turkey’s whiskies is apparently due to its spicy yeast variety.


Alkaline water like that which flows through Kentucky’s limestone caverns contains minerals that make for good fermentation of the beer. Distilleries like to emphasize how important their local water is for the quality of the whiskey, but that could be more because it’s a hard-to-reproduce marketing gimmick than a factor of major flavor importance.


All of the above factors, and likely others as well, make for myriad differences in the finished product. A Master Distiller and his panel of expert tasters are required to test all the barrels as they age, sometimes moving them around the rackhouse to age in a desired way. These skilled folks are responsible for combing whiskey from various barrels, or choosing specific barrels for ‘Single Barrel’ bottlings, to achieve a consistent flavor profile for all of a distillery’s products.

Whiskey producers generally use the same ‘juice’ (distilled spirit) for multiple brands (e.g.: Heave Hill’s Evan Williams vs the same company’s Elijah Craig) or product ‘line extensions’ (e.g.: Jim Beam, Jim Beam Black, Jim Beam Single Barrel). Since the yeast, grains, distilling apparatus & process, and barrels are all the same for a given ‘juice’ from a distillery, it is the age and rackhouse location differences chosen by the Master Distiller, and whatever other magic is going on post-distillation, that are responsible for the significant differences still found within a company’s brands or line extensions. This bourbon family tree gives an excellent visual representation of this. (Print it out and keep it near your whiskey stash!)

Now that you know all about what’s in the bottle, let’s start drinking it!