All beer can be classified as either a lager
or an ale. The differences begin during the brewing process. Whether
the beer is an ale or lager is defined by the type of yeast used in
the brew and the temperature at which fermentation takes place. Ales
are brewed with top-fermenting yeast which allows for rapid fermentation
at warmer temperatures; lagers are brewed with bottom-fermenting yeast
which ferments more slowly and at colder temperatures.
Lagers
Lager means to store or put aside. This beer is
made with bottom yeast, so-called because it flocculates to the bottom
of the vat. Traditionally bottom yeast will ferment at cold temperatures
less than 10 deg C. Now fermentation takes place at 12 to 18 deg C.
This cold or deep fermentation allows the malt and hops to assert
their fine flavours. Lager tends to be paler, drier and less alcoholic
than ales.
Pilsener or pils beer originated in Bohemia
where brewers first found beer that was over-wintered or lagered improved
if stored in cool caves and kept on ice. German lagers, including
beers such as bock and marzen, are made according to the Bavarian
Purity Laws of 1516 to ensure the beer is all-malt (no sugar) and
hopped with bitter and aromatic varieties (noble hops). Some German-style
beers are described as "helles" meaning pale or blonde.
Pale beers grew in popularity following the adoption of the glass
for drinking in the 19th Century.
Ales
Ales are brewed
with top-fermenting yeasts at temperatures from 15 to 25 deg C. Ales
are matured for shorter periods and at warmer temperatures. Ales include
a wide range of beer styles from porters and stouts to pale ales and
wheat beer. Generally, ales are higher in alcohol, more robust and
complex than lagers.
