The Brewing of Beer

Almost all beer contains only four ingredients: barley, water, hops, and yeast. Though the process of brewing beer is complex and varies considerably, the basic stages that are consistent are outlined below. There may be additional filtration steps between stages.

• MALTING: The first ingredient to come into play is barley, which is grain (or, in other words, a seed). The seeds are soaked in water for about two days and allowed to begin their development into plants. Enzymes are released that break down the proteins and starches in each grain into simple sugars meant to nourish the baby plant. However, once this process has begun, the barley is cooked in a kiln, arresting the growth process while the enzymes are at their peak of production. This is called malting.
• MASHING: In the mashing stage, the grain is actually transformed into sugar. The grains are crushed into a fine powder, or grist, and then soaked in water. Proteins are broken down; these eventually give the beer its body. Starches are broken down into simple sugars that nourish the yeast. Complex sugars remain to give the beer its malty taste. The mash is heated and strained to yield a substance called wort.
  Next, the wort is brought to a boil and the flowers of the female hop plant are added. Bitter resins and aromatic hop oils are released. The variety of hop, the amount added, and the point or points in the boil at which they are added all contribute to the flavor of the beer. They add bitterness when added early to the boil, flavor if added in the middle, and aroma when added at the end.
• FERMENTATION: The wort is then cooled and moved into a fermentation vessel. Yeast is added and allowed to consume most or all of the sugars in the wort. This is the fermentation process during which alcohol is produced. The process takes about ten days. Each brewery has its own strains of yeast, and it is the yeast that determines the character of the beer.
• STORAGE: The beer is then separated from the yeast (racked). Once the yeast is removed the beer is passed from fermentation to storage vessels. During transfer the beer is cooled to minus one degree centigrade. The beer stays in storage at this temperature, and any material which might impair the appearance, flavour and shelf-life of the beer settles out.
• FILTRATION: Following a set time in storage, carbon dioxide gas collected during fermentation is added to give beer its characteristic head and sparkling taste. The beer is then passed through a filtration system to remove surplus yeast and protein.
• PASTEURISATION: This is a process of heating and rapid cooling which prolongs shelf-life and destroys any bacteria or other organisms in the beer. Canned and bottled beers are pasteurised in their containers, while draught beer is pasteurised by means of a special heat exchanger called a flash pasteuriser.
• PACKAGING: The filtered and sparkling beer is packaged into bottles, cans and stainless steel casks, or kegs, ready for distribution.