The brewer's first step in making a beer is to wet the kernels of grain, promoting their germination, or sprouting. During this process, the germ or embryo of the grain breaks down slightly, releasing the enzymes that turn starches, complex sugars, into simple sugars. The brewer allows the grain to germinate for a short period and dries it quickly in a kiln. Dried, malted grain is very durable and easily stored.
The brewer next mixes the dried malt with water to create a porridgy substance called mash. During this phase, the mash is brought to a temperature of around 150°F (66°C) and is kept there a number of hours. The starchy components of the grain break down during mashing, and are converted into simple sugars, which yeast will be able to digest during the fermentation phase.
The brewer now adds more water to the mash and rinses out a watery sugar solution called wort, which is heated to a boil. At this point, the brewer adds hops, the flower of the Humulus lupulus vine, which give beer its characteristic bitter flavor and aroma.
When the wort has cooled to the temperature most friendly to yeast (50–60°F [10–16°C]), these organisms are added and go to work consuming the sugars in the wort, growing to be as much as five to ten times their original weight. They fuel their growth with the sugar and in the process, change it from carbohydrate to ethanol, a form of alcohol, and carbon dioxide, the gas that is responsible for beer's foam and bubbles.