The alcoholic strength of beer depends on the amount of malt relative to the water in the mash. For example, beer produced with 100 pounds of malt per barrel of water will be stronger than beer produced with 50 pounds of malt. Since the winemaker simply ferments the grape juice, the sugar content of the juice determines the strength of the wine, while the grape variety and growing conditions will affect the sugar content of the grape. Ideal sugar production occurs between 68 to 86 degrees F, provided sufficient sun strikes the vine’s leaves and grapes. Because excessive vine growth diverts nutrients away from the fruit and shades the grape clusters, soils and climates unsuitable for other crops create beneficial stress on the vines that limits vegetative growth and improves the quality of the grapes. Grapes that have not sufficiently ripened tend to be low in sugar and high in acidity. Rain before harvest may plump out the grapes and dilute the sugar content. For grapes naturally low in sugar or for the production of sweet wines (Trockenbeerenaulese), grapes may hang on the vine until evaporation shrivels the grapes to raisins, in order to concentrate the sugar.
Wine grapes range in sugar content from 15 to 25 percent by weight, typically resulting in alcohol levels of 8 to 13 percent by volume. The majority of beers, on the other hand, contain original extract of about 11 to 12 percent sugar by weight and alcohol of 4.5 to 5.0 percent by volume. However, brewers maintain the ultimate control over the strength of their beer by adjusting the quantity of malt. Not surprisingly, certain strong ales are called barley wines because their alcohol content resembles that of wine.
Brewers boil the sugary solution produced from water and malt (known as wort) before it ferments and becomes beer. Boiling sterilizes the wort and concentrates the sugar, which is another way to increase the alcohol content of the beer. Some brewers may add sugar to the wort to increase the beer’s strength. Strong abbey-style ales produced in Belgium are fortified with candy sugar for this reason. While adding non-malt adjuncts like sugar, corn or rice is often criticized (and even prohibited by the German Purity Law), these adjuncts have become accepted in many beer styles.
Wine drinkers may also frown on adding sugar to the must (the unfermented or fermenting juice pressed from grapes), but it is a useful way to increase the alcohol content of wine or balance its flavor. Adding sugar is known as chaptalization, which is particularly useful in years when the sugar content of the grapes is less than normal.
Alcohol is a waste product created when yeast metabolizes sugar to support growth and reproduction. At high levels, alcohol eventually becomes toxic to the yeast. For this reason, the concentration of alcohol produced solely by fermentation is limited to a maximum of about 15 or 16 percent alcohol by volume (ABV). Achieving higher alcohol levels requires some means to concentrate the alcohol by removing water. The most common method is distillation, and grapes and grain can both be the basis for distilled spirits. Brandy is distilled wine, and fortified wines like port and sherry have distilled grape spirits added to them. Scotch and bourbon are essentially spirits distilled from unhopped beer made primarily from malt and corn, respectively.