Often considered to be the great American spirit, whiskey in all its forms is also a wonderful introduction to distillation science. We’ve put together a primer on the science behind it, and have included an awesome infographic our friends at Distiller made covering the subject.
Working With the Grain
Before whiskey production can begin, the producer must choose a grain or mix of grains as the base for the alcohol. The most common choices are rye, corn, barley and wheat, but some more experimental distillers are using quinoa, oats, millet, and other grains to play with taste.
To begin the process of fermentation, some grains must be germinated, then dried in a process called malting. Malted barley is the most common, and the drying portion gives Scotch whiskey its signature smokiness. Here, the sprouted barley is dried by a peat fire that imbues its flavor to the grain. But don’t try mashing oats or rye at home. If performed incorrectly, this process can foster toxic bacteria.
Once the grains are dried, they are then milled into a coarse meal called grist. Hot water is added to preserve enzymes and break down complex proteins and starches into amino acids and sugars. This mixture is then heated to specific temperatures in a vessel called a mash tun. During its time in the tun, enzymes in the grains begin breaking down starches into glucose and maltose.
After this step is completed, the mixture is filtered. Known as wort, the resultant sugary liquid is allowed to ferment after yeast is added (though fermentation without the addition of yeast is possible, it takes a lot longer). Called wash, the resultant coarse beer is the basis for distillation.
Distill Thy Heart
At its purest, distillation is the process of purifying or separating liquids using heat. Here, alcohol and water boil at different temperatures—approximately 173°F and 212°F respectively. As the wash is heated, more alcohol than water will be evaporated. The vapor is collected as it condenses in an externally cooled pipe.
What is collected is broken into three parts: the heads, heart, and tails. The heads is the first liquid out of the still. As it was produced at the lowest temperature, chemicals like acetone and methanol are part of this cut. Needless to say, it’s discarded for the drinker’s health.
The heart is the product that will become whiskey and is put aside. Normally, this booze rings in at about 70% ABV. As the temperature continues to increase, the concentration of water vapor increases while the alcohol concentration decreases. The last segment, or tails, of the distillate contains a lot of aromatic compounds that are often used in small quantities to flavor the spirit.
After the distillation process is through, most whiskeys are then stored in casks to age. The regulations on several types of American whiskeys require that they be stored in new American white oak barrels. Whatever the wood, the whiskey leaches aromatic and flavorful compounds from the barrel over time.
To Blend or not to Blend
Producers must now face the question of whether to bottle a single barrel of their hooch or to blend multiple casks to create the ideal flavor and color. In the case of blended whiskeys, the age on the bottle represents the youngest whiskey in the mix.
Once blended or selected, the whiskey is usually diluted to between 40% and 46% ABV. Some producers will also release “barrel proof” or “cask strength” editions that are around 60% ABV. However, this process is not quite as simple as it sounds. Many of the aromatic and flavor compounds in whiskey aren’t soluble in water and might cloud the liquid. To improve its appearance, it's often cold filtered before it's bottled.
Years of aging and crafting went into the whiskeys in your home bar. Next time you’re drinking, take time to appreciate the appearance, flavor profile, and scent of your beverage—just as you would for a fine glass of wine.
To experience the whiskey’s full range, add a drop or two of water. How has it changed? What new scents and flavors do you pick up?
[Infographic via Distiller]