Liquor is big business – international conglomerate-style big business. Your favorite American whiskey could be controlled by people in office buildings halfway around the world. But those people rightly saw something enormously valuable when they purchased that brand. Americans are superbly skilled at making whiskey. And bourbon is signature American whiskey, as American as anything gets.
By law, bourbon must be at least 51% corn. But bourbon isn’t really about corn. It’s about trees – oak trees, in particular. If the whiskey isn’t aged in new charred oak barrels, it isn’t bourbon. For whiskey barrels, white oak, native to North America, is the gold standard.
White oak (Quercus alba) grows up and down the eastern half of the United States. It has always been plentiful in the Central Mississippi River Valley, notably Missouri Ozark country, and in the Ohio Valley, where the Ohio River makes its way westward through Appalachia. When they select white oak, log buyers for the bourbon industry are interested in the location of the trees, the age of the trees, and what growing conditions the trees were in. But it’s white oak they want because it is the most leak-resistant of the oaks.
To digress a bit about trees in general: Sapwood is new wood that acts as a conduit for water and sap distribution. As sapwood matures its pores begin to fill with organic material such as resin, and it becomes drier and stronger to form heartwood – the central, strong pillar of the tree. The sap-conducting pores of white oak are naturally plugged with a water repellent (tyloses), making white oak heartwood virtually impervious to liquids – and a distiller’s dream.
Once loggers fell the trees, truck drivers transport the logs to sawmills where workers turn them into lumber. The companies that make whiskey barrels want white oak lumber to be quarter sawn, or cut at a 90-degree angle to the growth rings. This means less twisting, warping, and cupping, as well as even greater leak resistance.
Log buyers only want wood that is straight and knot-free, with good tannin content. The grain has to be tight and predicable. The selected lumber is seasoned for a number of months, and once cured, it’s ready to be turned into whiskey barrels at a cooperage facility.
A worker will cut each board into sections, creating the staves that will make up the body of the barrel. He narrows the staves at their ends and hollows them slightly on the inside, which will create that characteristic barrel shape. Once milled, the staves are placed inside a metal hoop that will act as an assembly jig. The hoop is lined with as many staves as it takes (usually about 32) to minimize gapping between the pieces.
Now it’s time to bend the pieces. In the traditional method, the staves go through a steam tunnel that moistens them into a flexible state. Held by the metal hoop and other temporary metal rings, the wood curves into the form of a barrel. Now that it’s moistened, the wood is going to expand, creating enough friction and pressure to meld the staves into a liquid-tight container that won’t need any glue, nails, or screws. The heads – the top and bottom of the barrel – will be added later.
Charring the interior is the next step. Barrels pass over a gas-burning conveyor belt that shoots flames into each barrel to toast or char the insides. This essentially cooks the wood, extracting its flavors so that the whiskey can absorb them in aging.
Charring breaks down the chemical bonds in the wood fibers, creating smaller molecules that will impart flavor to the whiskey. Heating lignin, for example, creates vanillin, the characteristic vanilla fragrance of good bourbon. Charring releases a lot of other volatile compounds in oak, including lactone, which adds a coconut note to the whiskey. It also caramelizes wood sugars that are going to leach into the maturing spirits.
In addition to imparting flavor and color to the spirits, char removes sulphur compounds and other impurities, making the whiskey less harsh and more mellow. Barrels are custom-charred to the specifications of each distiller.
The freshly charred barrels are extinguished with water and cooled. A worker replaces the assembly jig with stronger, galvanized hoops that are riveted in place; the new hoops will hold the barrel into its curvature. Grooves are carved into each barrel to slot the heads in place, and an opening is punctured into the center of the barrel and fitted with a stopper, or bung. The barrel is tested for water-tightness, and if it passes the test, it is shipped to the distillery to mature whiskey.
To be labeled straight bourbon, the whiskey has to be aged at least two years. But if you want to know the perfect age for bourbon, there is no answer. Bourbon connoisseurs will tell you that age is more about maturity and ripeness than a specific time frame – which makes whiskey production as much an art as science. It ultimately depends on the person tasting the bourbon.
Consumers generally believe that older is better. But not always. Some distillers and tasters prefer bourbon in the 8- to 10-year-old range; others like certain bourbons to be between 12 and 15 years old. One bartender says that after 12 years, bourbon tends to take on stronger oak notes, masking some of the “subtle intricacies” she enjoys. Another says he rarely picks the oldest in any selection, saying that many times the wood tannins have started to skew the flavor.
One thing almost everyone agrees on is that the whiskey has to be aged, period. You can drink “baby bourbon” that hasn’t been matured, if you insist, but it is nothing at all like bourbon. It definitely has its fans, but a lot of people who have tried it will tell you that it’s awful. “White dog,” or raw whiskey, is named for its high-alcohol “bite.” As writer Reid Mitenbuler otherwise stated:
My bourbon-appreciating father once artfully compared drinking white whiskey to getting stabbed in the mouth with a screwdriver that’s been used to pry open a gas can.
Bourbon is not only aged to be smoother, it is diluted with water and usually chill-filtered before being bottled. Bourbon contains vegetable solids, proteins, fats, and esters that will cause cloudiness when the bourbon is chilled. This cloudiness, or “flocking,” is due to these particulates settling out of suspension. Distillers filter bourbon because some customers notice this cloudiness in chilled bourbon and return the bottle or decide not to purchase the brand again, thinking there is something wrong with it.
But bourbon enthusiasts sometimes prefer unfiltered bourbon. To them, these solids and oils add extra flavor and a rich, buttery mouth feel. Some bottles even have a bit of charcoal sediment at the bottom. To many bourbon drinkers, this is the best part of the bottle.