Gin is a juniper berry-flavored spirit. "Gin" is the shortened English version of "genever," which is Dutch for juniper. It's distilled in largely the same way as other grain spirits. Spirit distillation is essentially the separation of alcohol from other compounds, such as water, as a result of different compound's boiling points. For example, water boils at 212 degrees F, while ethanol boils at 173.1 degrees F. Said differently, alcohol has a lower boiling point than water, and can be vaporized and separated from the cooler, non-boiling water. The alcohol vapor can then be collected and condensed, leaving a result of much higher proof liquid. This process takes place in a still.
The different still types, and the corresponding affects on flavor profile, is a subject for another posting. But, whether or not gin is distilled using a pot still or a continuous still, the basic science and operation are the same. Simply put, gin is vodka flavored with juniper berrier and other botanicals. So, before you have gin to bottle, you have to first distill vodka, and vodka is really just neutral grain spirit. So how to you make a neutral grain spirit?
The grains used in gin distillation are usually wheat or rye. First, the grains are added to water, called a mash, and heated. This releases the starches in the grains. After the starches are released, yeast is introduced to the mash. The yeast eats the starch, leaving carbon dioxide and alcohol by-products. So, you now have a low-alcoholic porridge, which is pumped into a still where the alcohol undergoes separation, discussed above. After the first distillation, the resulting distillate still contains non-ethanol compounds. To get as neutral a spirit as possible, the distillate may undergo several rounds of distillation, with each round producing consecutively higher concentrated alcohol. Unlike whiskey, where some of the non-alcoholic compounds add to the flavor of the final product, the idea behind gin distillation is to produced a relatively pure and light-bodied spirit that will combine favorable with the botanical flavorings.
After the grains are distilled, and the clean neutral spirit is produced, you have your vodka. You're also now ready to add the juniper and other herbs and spices to make gin. Each gin company has its own secret recipe for juniper and botanicals, and there a few ways in which these ingredients are introduced to the grain spirit. Lower-quality gins are made by mixing the grain spirit with the botanical's extracts. Mainstream gins are made by soaking the botanicals in the neutral spirit and the re-distilling it. High-end gins are made in a different manner: During the final distillation of the base spirit, the alcohol (in its vapor form) goes through a chamber containing dried botanicals. The botanicals' flavors are extracted from the vapor before it is condensed.
While the distillation of many different gins are in many ways the same, the results are tremendously varied. The nuanced differenced in distillation make a substantial impact on the final product, creating complex flavor profiles. The distillation of gin, like other spirits, is truly a combination of science and art.
