Science Fair Project Encyclopedia
Brewing is the production of alcoholic beverages through fermentation. This is the method used in beer production, although the term can be used for other drinks such as sake, mead and wine. The term is also sometimes used to refer to any chemical mixing process.
Brewing has a very long history, and archeological evidence tells us that this technique was used in ancient Egypt. Descriptions of various beer recipes can be found in Sumerian writings, some of the oldest known writing of any sort.
The brewing industry is part of most western economies.
1.1 Ale (top fermenting yeasts)
All beers are brewed using a process based on a simple formula. Key to the process is malted barley which has been allowed to germinate and is then dried in a kiln and sometimes roasted. Depending on the amount of roasting, the "malted barley" will take on dark colour and strongly influence the colour and flavour of the beer.
The malt is ground into a coarse powder, known as grist, which is mixed with heated water in a vat called a "mash tun" for a process known as "mashing". During this process, natural enzymes within the malt break down much of the starch into sugars which play a vital part in the fermentation process. Mashing usually takes 1 to 2 hours, and during this time various temperature rests activate different enzymes depending upon the type of malt being used, its modification level, and the desires of the brewmaster. The Mash Tun generally contains a slotted "false bottom" or other form of manifold which acts as a strainer allowing for the separation of the liquid from the grain.
A mash rest at 104 °F or 40 °C activates beta-glucanase , which breaks down gummy beta-glucans in the mash, making the sugars flow out more freely later in the process. In the modern mashing process commercial fungal based beta-glucanase may be added as a supplement. A mash rest from 120°F to 130 °F (49°C to 55°C) activates various proteinases, which break down proteins that might otherwise cause the beer to be hazy. But care is of the essence since the head on beer is also composed primarily of proteins, so too aggressive a protein rest can result in a beer that cannot hold a head. This rest is generally used only with undermodified (i.e. undermalted) malts which are decreasingly popular in Germany and the Czech Republic, or non-malted grains such as corn and rice, which are widely used in North American beers. Finally, a mash rest temperature of 149 to 160 °F (65 to 71 °C) is used to convert the starches in the malt to sugar, which is then usable by the yeast later in the brewing process. Doing the latter rest at the lower end of the range produces more low-order sugars which are more fermentable by the yeast. This in turn creates a beer lower in body and higher in alcohol. While a rest closer to the higher end of the range creates more higher-order sugars, which are less fermentable by the yeast so a fuller-bodied beer is the result, with less alcohol.
After the mashing of the resulting liquid is strained from the grains in a process known as lautering. At this point it is known as wort. The wort is moved into a large tank known as a "copper" or kettle where it is boiled with hops and sometimes other ingredients such as herbs or sugars. The boiling process serves to terminate enzymatic processes, precipitate proteins, isomerize hop resins, concentrate and sterilize the wort. Hops add flavour, aroma and bitterness to the beer. At the end of the boil, the hopped wort settles to clarify it in a vessel called a "whirl-pool" and the clarified wort is then cooled.
The wort is then moved into a "fermentation vessel" where yeast is added or "pitched" with it. The yeast converts the sugars from the malt into alcohol, carbon dioxide and other components through a process called Glycolysis. After a week or so, the fresh (or "green") beer is run off into conditioning tanks . After conditioning for a week or longer, the beer is often filtered to remove yeast and particulates. The "bright beer" is then ready for serving or packaging.
There are four main families of beer styles determined by the variety of yeast used in their brewing.
Ale (top fermenting yeasts)
Ale yeasts ferment at warmer temperatures of 65 to 75 °F (18 to 24 °C) and tend to collect on the surface of the fermenting beer. Because of this they are often referred to as Top Fermenting yeast. Ales are generally ready to drink within three weeks after the beginning of fermentation. Ales range in color from very pale to black opaque. England is best known for its variety of Ales.
Lager (bottom fermenting yeasts)
While the nature of yeast was not fully understood until Emil Hansen of the Carlsberg brewery in Denmark isolated a single yeast cell in the 1800s, brewers in Bavaria had for centuries unknowingly been selecting these cold-fermenting Lager yeasts by storing or "Lagern" their beers in cold Alpen caves. The process of natural selection meant that the wild yeasts that were most cold tolerant would be the ones that would remain actively fermenting in the beer that was stored in the caves. And over several centuries starting at very least in the 1553 when the King of Bavaria outlawed brewing in the summer months (simply because beer brewed in the winter tasted better), Lager yeast was born. It was in fact some of these Bavarian yeasts that were stolen and brought back to the Carlsberg brewery around the same time that Hansen did his famous work.
Lager yeast tends to collect at the bottom of the fermenter and is often referred to as Bottom Fermenting yeast. Unlike ale, lager is fermented and then stored for 30 days or longer close to the freezing point. During the storing or Lagering process, the beer mellows and flavours become smoother. Sulfur components developed during fermentation disipate. The popularity of lager was a major factor that led to the rapid introduction of refrigeration in the early 1900s.
Today, lagers represent the vast majority of beers produced, the most famous being a light lager called Pilsner which originated in Pilsen, Czech Republic (Plzeň in czech language). It is a common misconception that all Lagers are light in color but lagers range from very light to black opaque just like Ales.
Beers of Sponteanous Fermentation (wild yeasts)
These beers are nowadays only brewn around Brussels, Belgium. They are fermented by means of wild yeast strains that live in a part of the Zenne river which flows through Brussels. These beers are also called Lambic beers.
Beers of mixed origin (blends of sponteanous fermentation beers and ales or lagers)
These beers are blends of sponteanous fermentation beers and ales or lagers or they are ales/lagers wich are also fermented by wild yeasts
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details