Most people don't realize that their bodies contain scores of types of alcohols even if they've never taken a drink.
To an organic chemist, an alcohol is any compound with a hydroxyl group attached to a saturated carbon atom.
A "saturated" carbon atom is one which is attached to four other atoms; a hydroxyl group is the organic chemist's name for an "almost molecule" consisting of one oxygen and one hydrogen atom.
By this chemical definition, cholesterol is an alcohol; so are glycerol (a key part of triglycerides), Vitamin A, lactic acid (which builds up in your muscles following intense exercise), methanol (highly toxic, also known as methyl alcohol and wood alcohol), and sorbitol (which tastes sweet and may be marketed as a sugar substitute).
But what concerns us here is ethyl alcohol, also known as ethanol. It takes its name because a hydroxyl group is added to a saturated, two-carbon configuration which organic chemists call an ethyl group.
Ethanol is inescapable because all it takes to get fermentation started is sugar and yeast -- both of which are ubiquitous in our environment and food supply.
Take a molecule of glucose, add yeast and very quickly you get two molecules each of alcohol and carbon dioxide.
Primitive people never heard of Chardonnay or Miller Time, but they discovered that if they ate fruit, especially grapes, that was left too long in a warm spot, it would do funny things to their outlook on prehistoric life. All the yeasts necessary to ferment grapes actually grow on the skin of each grape. It's as if each grape wears a "Born to Ferment" tattoo.
The same fermentation will happen to apple juice, orange juice or other fruit juices and fruit left in your refrigerator. In fact, laboratory samplings of commonly consumed fruit juices and sugar-based soft drinks purchased from a supermarket (and tested right from the carton the day they were put on the store shelf) all showed measurable amounts of ethanol, up to 0.1 percent.
The amount of ethanol in some of the samples doubled or tripled after only three days in the refrigerator.
The fermentation used to produce wine, beer and spirits is much more carefully controlled and the particular species of yeast (called strains) are selected for their ability to produce desired tastes and other characteristics.
Fermentation and production methods vary greatly even among makers of each type of beverage, but each of the three main categories has its basic technique.
Wine is the easiest. The grapes are crushed and the juice drained into a container. Fermentation then begins with the natural yeasts or others added by the winemaker. Fermentation stops naturally when one of two things happens: (1) all the sugar is converted to alcohol, or (2) the alcohol content reaches a level (usually around 15 percent by volume) that kills the yeast.
The intense natural grape tastes and the minimum amount of manipulation required to make wine makes it the most intensely flavored of the three main categories of alcoholic beverages.
Fortified wines, dessert wines, ports and madeiras are usually made by adding grape brandy to partially fermented (and thus sweet) wines to increase alcohol content up to about 22 percent. However, some "late harvest" wines start out with very high sugar levels in the grapes and, with special strains of yeast, can be naturally fermented to produce both sweetness and higher alcohol. Beer and distilled spirits made from grain and other starches are much more complicated. Starches are made up of long chains of sugars and must be "pre-digested" before yeast can ferment the sugars. Most grains used in beer and other liquor are allowed to germinate slightly to produce enzymes that liberate the sugars which are then converted to alcohol. American beer is usually about 3.5 percent alcohol; ales, stouts and malt liquors are usually higher -- normally up to about 8 to 10 percent.
The brewmaster helps impact flavors to the beverage by adding hops and by various methods of toasting the grain. The resins leached from the hops also act as a preservative.
Distilled spirits are just that -- concentrated solutions of alcohol heated to a point where the alcohol boils off and is collected by a condenser. Some spirits are distilled more than once, thus increasing the alcohol content and further concentrating the faint flavors which survive the distillation process.
Spirits made with starches, which have little taste at all (like vodka) are infused with flavors by aging in wood or by adding other substances (like juniper berries in gin). The wood also helps take some of the rough edges off the high alcohol content which can run to 50 percent or more. Brandy and cognac are distilled from wine.
In general, the higher the alcohol content of a beverage, the more stable it is (that is, unlikely to spoil).