5.4: Alcohol

Alcohol is a fermentation product of carbohydrate. Yeasts convert sugar to alcohol, using enzymes. In fact, the first enzymes were discovered in yeast; the word enzyme comes from Greek words meaning in yeast. Alcohol has about 200 calories per ounce (7 cal/g).

Yeasts use sugars—not starch—in fermentation. Thus, sweet liquids (e.g., fruit juice) are good starters. Starch must be first broken down to glucose or maltose (two glucoses linked together) before yeast can use it. One way to do this is called malting: Grain is allowed to germinate (sprout) for a few days. This produces enzymes that convert starch (the plant’s stored form of energy) to maltose and glucose (fuel for the seedling).

An interesting way to convert starch to sugar for alcohol production was used in Peru in the 16th century. Peruvians chewed corn that had been ground and soaked in water, thereby mashing it further while mixing it with an enzyme in saliva that breaks starch into sugar. It then was spit into a pot, where the enzyme action continued. Then the pot was boiled for several hours, killing microbes and concentrating the sugars by evaporating the water. The mixture was then filtered, providing a clear sugar-rich liquid ready for fermentation.

In making wine, sugar in fruit juice (usually grape) is converted to alcohol. For beer, malted barley is the usual sugar source. Wine and beer have a bit of the nutrients of grapes and barley, and have a limited alcohol content (yeast can’t grow once alcohol reaches about 15 to 20%). Wine is about 12% alcohol; beer about 5%.

To make high-alcohol drinks (hard liquor), alcohol is distilled (vaporized and condensed). Alcohol evaporates at a lower temperature than water. So when you heat a mixture of alcohol and water, alcohol vaporizes first, allowing alcohol to be separated and concentrated from liquids like fermented fruit (wine) and fermented grain (beer).

Doubling the percentage of alcohol in liquor gives its proof—100-proof liquor is 50% alcohol. Brandy (about 80 proof) is distilled from wine; whiskey (about 90 proof) from beer; and rum (about 90 proof) from fermented molasses.

Hard liquor is not only a concentrated source of calories due to its high alcohol content, but is essentially devoid of nutrients; even the small amount of nutrients in the original fermented product is left behind in the distillation process. Some people get more than half their calories from alcohol. Those who drink a lot are susceptible to both nutrient-deficiency diseases and the toxic effects of alcohol itself.