The Brewing
process
Beer production starts with high quality raw materials.
The basic ingredient of beer is
barley. Barley is transformed into
malt at the maltings by
steeping the grains in water and allowing them to germinate.
This breaks down the complex molecules of starch, cellulose
and protein inside each grain so they can be used in the
brewing process, the final result being a package of starch,
some sugar and the enzymes
(special proteins which act as catalysts for biological
reactions) to convert the starch to sugar. Germination is
stopped by heating the malt in an oven called a
kiln. This dries out the
malt so that it can be stored but also caramelises some of
the sugars. The longer malt is kilned, the darker the malt
becomes. This reduces the enzyme activity but increases
colour and flavour, and small quantities of these darker
malts are used to provide the colour and flavour of the
final beer. Other essential ingredients are water (known as
liquor in brewing) and
hops, the flowers of the
hop plant being used to provide bitterness, aroma and
flavour. Other raw materials can also be used to replace
part of the malt to impart unique characteristics of
appearance, aroma or flavour to the final beer. These are
called adjuncts and can
include materials such as maize, rice, wheat or liquid
sugars and syrups.
The brewing process begins with the malt being lightly
crushed into a coarse powder called a
grist. The grist is
transferred to a vessel called a
mash tun where it is mixed
or mashed with hot water.
This dissolves the starch and allows the enzymes in the malt
to convert the starch to sugars. The temperature and time of
mashing are critical in determining the quality and
characteristics of the final beer. When this process is
complete, the mash is transferred to a vessel called a
lauter tun where the sugary
liquid or wort is separated
from the grain residue. The wort from the lauter tun is
transferred to a wort kettle
where the wort is boiled and the hops are added. Hops are
added at the start of the boil to provide bitterness and may
also be added near the end of the boil to add aroma and
flavour. Boiling sterilises the wort, removes unpleasant
aromas and flavours and makes material which would cause the
wort to become cloudy, clump together or "flocculate". The
wort is transferred to a vessel called a
whirlpool which uses a high
speed swirling or vortex effect to remove the unwanted
solids. The wort is sent from the whirlpool via a
wort cooler or
paraflow to a fermentation
vessel. As the wort leaves the paraflow,
yeast is added, as well as
oxygen to allow the yeast
to multiply before fermentation begins.
During fermentation, the yeast converts the sugars in the
wort to ethanol, carbon dioxide and a range of other subtle
flavour compounds. Fermentation produces heat and the
temperature of the fermentation vessel is controlled by
using cooling jackets around the vessel to prevent damage to
the yeast and control the speed of the fermentation. As the
sugars are used up, the fermentation slows down and the
vessel cooling is used to stop the fermentation at the
desired strength or gravity.
Cask conditioned beer is
packaged into stainless steel or aluminium casks directly
from the fermentation vessel with finings added to clarify
the beer. Hops may also be added to the cask to add flavour
and aroma. Cask conditioned beer is not pasteurised and will
therefore still contain some live yeast. Because it has not
been pasteurised, cask beer only has a shelf life of four
weeks and requires careful handling to ensure that it is
presented to the customer in perfect condition. Beer not
destined for cask racking is conditioned in the brewery
either in the fermentation vessel or by transfer to a
maturation vessel where the
beer is held at a low temperature for a set period of time
with a small quantity of yeast to remove undesirable aromas
and flavours.
This rough beer is then
filtered to remove the
yeast and produce bright
beer which is carbonated with carbon dioxide (CO2),
pasteurised to ensure
sterility and guarantee shelf life and packaged in stainless
steel or aluminium kegs, aluminium or steel cans or glass
bottles. Because this beer has been pasteurised, it has a
much longer shelf life. Beer packaged in kegs will keep for
two months whilst beer packaged in cans or bottles will last
for up to nine months.
The beer is now ready for despatch to the consumer. The
beer will be transported directly from the brewery to
temperature controlled warehouses from where it will be
delivered to outlets such as supermarkets, shops and off-licences.
Beer destined for bars, pubs and clubs will be delivered by
drays, special vehicles that will deliver beer, spirits,
wine and soft drinks in a single delivery. The entire
process takes from six to seven days to produce ales to
three weeks for lagers.
