Through a process of heat and condensation, alcohol can either be removed from alcoholic beverages or fortified by glycerin. It's a complex process that allows for alcohol-free beer and fortified wines. Glycerin or glycerol (essentially the same) is naturally sweet (about 26 times more sweet than sugar) and can also be used in liqueurs as a thickening and sweetening agent.
What is Glycerin
Glycerin is a sweet-tasting, colorless, thick liquid which, when frozen, doesn't end up like an ice cube. It freezes into a gummy paste. It also has a relatively high boiling point. Glycerin can be dissolved into water or alcohol, but not oils. On the other hand, many things will dissolve into glycerin easier than they do into water or alcohol. So it is a good solvent.
Where Glycerin Comes From
Glycerin is a natural by-product of the soap-making process using oils, fats and lye. Most commercial soap makers remove the glycerin to use it in other more-profitable lotions and creams. Handmade soap, usually more expensive than regular soap because of its glycerin content, keeps the glycerin in its soap as a skin softener and marketing tool.
Glycerin's Affect on Alcohol Content
Through a complex process of condensation and cooling glycerin can be used to boost the alcohol content of liquor or reduce it to nothing, depending on where the condensation and cooling process is stopped.
How Does It Work?
Glycerin is an extremely complex chemical that possesses the interesting property of being highly hygroscopic, which is a complicated way of saying that it is very water absorbent. It will suck water right out of the air. For example, if you would leave an open bottle of glycerin sitting on your counter exposed to the air, over a relatively short period of time it would end up 80 percent glycerin and 20 percent water. That's part of the principle--a very small part--behind how beer companies can “brew” non-alcoholic beer.
Liqueurs
Glycerin is also a thickener that can be added to after-dinner cordials to enhance their already-thick characteristics brought out in the distillation process. It can also be used to increase the density of certain other liquors that allow them to be layered into a colorful alcoholic drink.