The malting
During 2 - 3 days the barley grains are moistened and dried
alternatively ("steeping") so as to rinse them and prepare them for
germination: moistened barley is laid on a thin layer at a temperature
of 15°C to 20°C, typically for 4 to 6 days. Germination
causes
the secretion of enzymes that will trigger the conversion of starch
into sugars. The germination is stopped by a sudden warming at around
65°C ("kilning"). The duration and the temperature
used for
kilning will affect the colour and flavour of the malt, hence of the
beer. Thereafter, germs are removed by frictioning the malt grains
before these can be used for brewing (this step is called "screening").
The brewing
"Mashing": grain is crushed and then poured into hot water at
55°C.
A mix of different types of malt is usually used, sometimes with wheat
or wheat malt, or other cereals. The temperature of the mixture
("mash") is subsequently increased to about 75°C to activate
the
enzymes that will convert starch into sugars and proteins into
amino-acids. The mash is then naturally filtered through the husks
sedimented at the bottom of the tank ("lautering"), resulting in a
liquid called "wort". The residual grain is often used for animal
feeding.
"Cooking": wort is transferred to copper tanks where it is boiled with
hops and sometimes other ingredients such as herbs or sugars. This
process serves to stop enzymatic activity, precipitate proteins, and to
concentrate and sterilize the wort. Cooking determines much of the
flavour, aroma and bitterness of the beer. The wort is then cooled and
oxygenated to optimize fermentation.
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"Fermenting" is the stage where sugars transform into carbon dioxide
and alcohol under the action of yeast. As far as brewing is concerned,
fermentation can be of 3 different types, involving different species
of yeasts: high fermentation, low fermentation, and
spontaneous
fermentation. Subsequently, there can be a second and even a third
fermentation.
"High" (or "Top") Fermentation: the yeasts involved, of the
saccharomyces cervisiae type, are active between 15 and 25°C.
During fermentation, the yeast floats on the surface, hence the name
"high fermentation". The majority of special and regional beers are of
this type, of which the "ale" type constitute the biggest family.
"Low Fermentation": the yeasts involved are of the saccharomyces
carlsbergensis type and act best between 6 and 10°C. The
fermentation takes longer and yeast sinks to the bottom of the vat,
hence the name "low-fermentation". Typical low fermentation beers are
of the "lager" type, of which the "pils" type is a sub-category.
Spontaneous Fermentation. Only the wild yeasts and bacteria existing in
the air are involved, no yeast is added. Spontaneous fermentation beers
are specific to the South-West of the Brussels region ("Pajottenland").
Lambic and the derived Gueuze and fruit beers (Kriek, Framboise, ...)
Aging and conditioning
After fermentation, brewers often add spices, fruit, syrup, candi sugar
or honey ... to give their beer a distinctive character. Then the beer
is set to mature for a couple of weeks, several months, or as long as 3
years. Then the beer is filtered (except for beers that will undergo
further fermentation within the bottle, such as gueuze and trappist
beers), sometimes pasteurized, and then tapped in bottles or in
barrels. |
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