How is beer made?

The four ingredients

Most beer is made from water, malted grain, hops and yeast. Barley is the main grain because its husk acts as a natural filter and its enzymes convert well, but wheat, rye and oats are also malted. Some brewers add adjuncts such as rice, corn or sugar to lighten body or cut costs. Water makes up about 90 to 95% of the finished beer, and its mineral content shaped regional styles such as the soft-water pilsners of Plzeň and the sulfate-rich pale ales of Burton upon Trent.

Step 1: Malting

Malting usually happens at a specialist maltster, not at the brewery. Grain is steeped in water for one to two days until it starts to germinate, then left to sprout for four to six days while it develops the enzymes that will later break starch into sugar. The green malt is then dried in a kiln. Light kilning gives pale malt for lagers; higher temperatures or roasting give caramel, chocolate and black malts used in amber and dark beers.

Step 2: Milling and mashing

At the brewery, malt is milled to crack the husks and expose the starchy interior. The grist is mixed with hot water in a mash tun, usually at 62 to 72 °C, for about an hour. Enzymes called beta-amylase and alpha-amylase cut starch into fermentable sugars such as maltose. A lower mash temperature favors fermentable sugars and a drier beer; a higher one leaves more dextrins and a fuller body. German and Czech brewers also use decoction mashing, boiling part of the mash and returning it.

Step 3: Lautering

Lautering separates the sweet liquid, called wort, from the spent grain. The mash is moved to a lauter tun or left in place, where the grain husks settle into a filter bed. Wort is drained from below while hot water is sprayed over the top, a process called sparging, to rinse out remaining sugar. The spent grain, rich in protein and fiber, is commonly sold as animal feed.

Step 4: The boil and hopping

The wort is boiled in a kettle, often called a copper, for 60 to 90 minutes. Boiling sterilizes the wort, stops enzyme activity, concentrates it, and drives off unwanted compounds such as dimethyl sulfide. Hops added early release alpha acids that isomerize into bitterness; hops added late or in a whirlpool after the boil keep more aroma. After the boil, solids are removed in a whirlpool and the wort is cooled quickly through a heat exchanger to fermentation temperature.

Step 5: Fermentation

Cooled wort is aerated and yeast is pitched into it. The yeast consumes the sugars and produces ethanol, carbon dioxide and flavor compounds. Ale yeast works at about 15 to 24 °C for several days; lager yeast works at about 7 to 13 °C for one to two weeks. A thick foam called krausen forms on top during active fermentation. Some styles, such as lambic, rely on wild yeast and bacteria from the air instead of a pitched culture. See ale vs lager for the difference.

Step 6: Conditioning

After primary fermentation, the young or green beer is matured. Lagers are held near 0 °C for weeks, which clarifies them and lets yeast reabsorb diacetyl and other off-flavors. Ales may be conditioned more briefly, dry hopped for aroma, aged in wooden barrels, or blended. Many Belgian and British beers are refermented in the bottle or cask with a little added sugar and yeast, creating natural carbonation.

Step 7: Filtration and packaging

Most industrial beers are filtered or centrifuged to remove yeast and haze, then carbonated to a target level. Many are pasteurized, either in the bottle or can (tunnel pasteurization) or before filling (flash pasteurization), to extend shelf life. Beer is then filled into bottles, cans, kegs or casks while excluding oxygen, which would stale it. Unfiltered styles such as kellerbier and many German wheat beers keep their yeast.

• Malting: steep, germinate and kiln grain (about 1 week)
• Milling and mashing: convert starch to sugar at 62 to 72 °C (about 1 hour)
• Lautering and sparging: separate the wort from the grain
• Boiling and hopping: 60 to 90 minutes
• Cooling and fermentation: 3 days to 2 weeks
• Conditioning: days for ales, weeks to months for lagers
• Filtration, carbonation and packaging