Alcoholic beverages vary considerably
in their ethanol content and the foodstuffs from which they are
produced. Most alcoholic beverages can be broadly classified as
fermented beverages made by the action of yeast on sugar content,
or distillation and fermentation. The ethanol content of a beverage
is generally measured in terms of alcoholic content, which is expressed
either as a percentage or in proof units.
Beers are made from cereal grains and other starchy materials, wines and ciders from fruit juices, and meads from honey. Cultures around the world have been making fermented beverages from numerous other foodstuffs, and the names for the various fermented beverages abound. Alcoholic beverages may contain as much as 20% ethanol by volume; this limit is set by the yeast's tolerance for ethanol, or the amount of sugar in the starting material.
Broad categories of distilled beverages
include whiskies distilled from fermented cereal grains; brandies
from fermented fruit juices, and rum from fermented molasses or
sugarcane juice. Vodka and similar neutral grain spirits can be
distilled from any fermented material with grain or potatoes being
the most common; these spirits are so thoroughly distilled that
no flavors from the particular starting material remain. Numerous
other spirits and liqueurs are prepared by using distilled spirits
to extract flavors from fruits, herbs, and spices. A traditional
example is gin, an alcoholic extract of juniper berries.
In a few beverages, ethanol is concentrated by means other than distillation. Applejack is traditionally made by the process known as freeze distillation, where water is frozen out of the fermented apple cider, which leaves a more ethanol-rich liquid behind. Fortified wines are prepared by adding brandy or some other distilled spirit to partially-fermented wine. This kills the yeast and conserves some of the sugar in the grape juice; such beverages are sweeter and more ethanol-rich than other wines.