The Complete Handbook of Beer

Chapter 1: Understanding Beer

Beer is a fermented beverage made from four basic ingredients: grain (typically barley), water, hops, and yeast. Those four things, combined in different proportions and treated in different ways, produce everything from a light lager to a barrel-aged stout. But the chemistry that happens between yeast and grain sugar is not incidental to beer—it is beer. Understanding that chemistry explains why beer spoils, why it tastes different at different ages, why storage matters, and why two beers that look identical in a glass can have completely different shelf-lives and price points.

Start with the grain. Barley is the dominant brewing grain because its starch converts efficiently into fermentable sugar when steeped in hot water, a process called mashing. A brewer soaks crushed grain in water heated to between 150 and 170 degrees Fahrenheit for 60 to 90 minutes. Enzymes naturally present in the grain break down starch into simpler sugars—glucose and maltose—that yeast can consume. The liquid that drains from the grain bed, called wort, now contains those sugars, minerals from the water, and proteins from the grain. This wort is bitter, flat, and undrinkable. It becomes beer only after boiling and fermentation.

The boil serves two purposes: it sterilizes the wort, killing any bacteria or wild yeast that might spoil the batch, and it allows the brewer to add hops. Hops are the dried flowers of a climbing vine; they contain resins and oils that provide bitterness (measured in IBU, or International Bitterness Units) and