Oktoberfest Begins in Munich, and the drinks will flow thanks to this brewing process.
People throughout the world have been producing and enjoying beer for thousands of years. “The key process that occurs during brewing is the fermentation by yeast of an aqueous solution of sugars and amino acids extracted from cereals to produce an aqueous solution of ethanol and other components,” Stewart says. The extracted sugar solution, known as wort, is a nutrient medium for yeast cells. “During the fermentation process, the yeast cell population increases by feeding on the sugars and amino acids,” he explains.
At the same time, the yeast excretes ethanol, carbon dioxide, and, in smaller amounts, other fermentation products.
Highly soluble, fermentable sugars such as maltose, sucrose, glucose, and fructose are rarely encountered in a free form in nature, notes Ian S. Hornsey, founder of the Nethergate Brewery in Suffolk, England, in his book “A History of Beer and Brewing” (Cambridge, U.K.: Royal Society of Chemistry, 2003). One of the obvious reasons is that much of the animal kingdom, including people, would be frequently inebriated if such sugars were widely available.
Five distinct processes, he says, are involved in beer production: malting of cereal (usually barley), mashing, boiling, cooling, and fermenting.
The quality of beer relies on a number of characteristics, including color, smell, the foam that forms the head on beer when it is poured into a glass, and particularly its taste. A typical ale or lager may contain more than 800 compounds that are capable of affecting flavor. They include esters such as ethyl acetate, short-chain fatty acids, various alcohols, aldehydes, and sulfur compounds.
Visit “What’s That Stuff” to learn more about the production of beer.
Excerpted with permission, Chemical & Engineering News
Copyright © 2006 American Chemical Society