Fermentation Process in Making Beer

A number of steps must take place before the fermentation of beer begins. A barley malt is added to water and boiled to make a mash, then hops are added to provide the exact blend of bitterness and flavor. The mash contains sugars extracted from the malt, which are converted to alcohol during the fermentation process. Only after the hops are added and the mixture is allowed to boil for some time can the fermentation process properly begin.

Fermentation takes place in a specialized container called a fermenter. It allows the proper biochemicals to undergo fermentation, while keeping the mixture sterile and removing unwanted byproduct such as carbon dioxide.

When the brewer is ready to begin fermenting, he puts the beer mixture in the fermenter, then adds yeast. He often stirs the mixture to help oxygenate the yeast, which is a vital part of the process. When it's all stirred, he seals the fermenter and stores it in a cool, dark place to allow the beer to properly ferment.

The fermentation itself involves a reaction between the yeast and the sugars and starches in the rest of the mixture. The yeast consumes them, and in return creates alcohol and carbon dioxide. The fermenter slowly releases the carbon dioxide through its airlock while the fermentation continues. The process takes a fair amount of time-- anywhere from a week to several months, depending upon the type of beer. It all depends on how long the yeast takes to absorb the sugars, which depends on how strong the yeast is and the precise recipe of beer being brewed.

Fermentation requires careful watching to ensure that the process proceeds smoothly. Most important, the fermenters must be regularly checked to make sure they maintain a cool temperature. In commercial brewing, a certain amount of carbon dioxide is retained in order to give the beer its carbonation (home brewing and specialty brewing operations will carbonate the beer during a subsequent step). In such cases, the brewer will cap the airlock and allow the beer to remain under pressure after a certain time until it's ready for the final few stages.

In some cases, the first round of fermentation is followed by a second round. The beer is removed from the first fermenter and placed in another one. That helps strain out the yeast (which settles during the first fermentation process) and fortifies the beer when it's going to be stored for a significant period before being bottled. Secondary fermentation also helps makes beer clearer: desirable for certain recipes, but not at all desirable for others.