Boil
The wort is then boiled. Boiling the wort improves the beer in a number of ways. It kills any enzymes remaining from the mash that could later make the beer unstable. It sterilizes the wort reducing the chances of contamination. It reduces the amount of water which increases the concentration of fermentable and unfermentable material extracted from the grain. The fermentable sugars will be converted to alcohol during fermentation and the unfermentable sugars and proteins will contribute to the final beer’s color, head, aroma, mouthfeel, and flavor.Hops are generally added during the boil which extracts the resins and oils. Hops added early during the boil contribute a bitter flavor to the beer which is valuable because they add a balance to sweetness from the unfermentable sugars. Hops added to some beers during the final minutes of the boil contribute aromas and very little bitter flavor to the beer.
Fermentation
Next the wort is cooled to 46 to 55 degrees Fahrenheit for lagers and 60 to 78 degrees Fahrenheit for ales. It is then transferred to a sterile fermentation container where the yeast is added. Yeast is a living organism that feeds on sugar. The byproducts of the lifecycle of yeast are alcohol and carbon dioxide. At the top of the fermentation tank is an airlock that both allows the CO2 to escape and prevents foreign material from entering. It will usually take a day or two for active fermentation to become evident. Most fermentation is completed within seven to fourteen days.Aging
The beer is then drained off of the yeast sediment that collects at the bottom of the fermentation tank and transferred to a secondary lagering or aging container. Ales are usually aged in the secondary container for one to four weeks. During this time any remaining material drops out of suspension clearing the beer. Aging also blends and mellows the flavors. Lagers are similarly aged for months, some even up to a year, at very cool temperatures.Carbonation
The result is bright, or uncarbonated, beer. There are two ways to carbonate beer. Natural carbonation involves transferring the beer to it final container – bottles, casks, or kegs – and just before sealing it adding a small but measured amount of sugar. There is enough yeast that remains suspended in the beer that this little bit of sugar will be fermented. This will not significantly contribute to the alcoholic content of the beer but in the sealed container the second byproduct of fermentation, CO2, has no place to go and so is absorbed by the beer. This method of carbonating beer is popular among homebrewers that typically don’t have the equipment to force carbonate their beer. It is also the correct way to carbonate certain styles of beer such as hefe-weizen.Forced carbonation is the method preferred by many breweries. Before the beer is packaged it is filtered and pasteurized. This removes or kills any yeast that might have been in suspension. It results in a more stable product than natural fermentation. The CO2 gas is then forced into the beer container before it is sealed where the beer will absorb it.
This is a very simplistic explanation of the brewing process. For more information about brewing or for information about brewing your own beer check out the other resources in the basic homebrewing and advanced homebrewing categories.
