MCB 405

PRODUCTION OF BEER

Beer is an alcoholic beverage that is produced industrially by the microbial fermentation of

wort (sugary solutions obtained by the dissolution of malted cereal grains). The process by
which wort is converted into alcohol by microbes such as yeasts is known as brewing. The
art of beer production (i.e. brewing) is an ancient practice known to mankind over many
thousand years ago.

The major raw materials for beer production in the industry include: barley, malt, water,
hops, yeasts, and adjuncts (which are usually added during beer production to increase and
improve the alcoholic content of the beer).

Barley is extensively used for beer production due to its unique properties. Barley contains
high amount of amylase enzyme (for starch hydrolysis); and this gives it a good enzymatic
composition. Barley yields the desired fermentable extracts, and its thick husks make the
brewing process (especially malting and filtration) much easier than when other cereal grains
are used. Barley has a gelatinization temperature (52-59oC) which makes the solubilization
and hydrolysis of its starch possible in one operation. The thick husks of barley prevent the
grain from possible fungal infection especially during storage. These features of barley make
it a benchmark against which other cereal grains can be compared.

Adjuncts also act as other carbohydrate sources for beer production; and they possess
properties that beneficially supplement the principal raw material (e.g. barley) used for the
brewing process. They act as cheaper sources of extract and starch to the brewing process;
and they also increase the production of beer especially in cases where there is limited brew
house capacity. Nevertheless, adjuncts are not always used by all brewing industries because
of some demerits that they bring along. Adjuncts may cause unusual or unwanted flavour
development in the beer; and complete saccharification is usually difficult with adjuncts.
There is also the issue of slower filtration of the mash when adjuncts are used for brewing.
Examples of adjuncts that can be used are rice, sorghum, maize, cassava, potatoes.

Hops are aromatic plants that give beer its flavour and bitterness; and they are naturally
sourced from the female flower plant known as Humulus lupulos. H. lupulos contribute to the
formation of a good froth (foam) and it also protects the beer against any possible microbial
contamination. Hops contain or produce both resins and essential oils. The resins provide the
precursors that impart bitterness to the beer while the essential (volatile) oils provide the
aroma associated with the plant, and which also imparts on the flavour of the beer.

Water for brewing processes can be treated through ion exchange, de-carbonation and by the
addition of acid or base to regulate the pH of the water. It is vital to treat water for brewing
processes because the pH, mineral and ionic content of the water may impact or affect the
beer being brewed. In general calcium ions lead to a better flavor than magnesium and
sodium ions. Some ions are undesirable in brewing water: nitrates slow down fermentation,
while iron destroys the colloidal stability of the beer.

Yeasts such as Saccharomyces cerevisiae and bacteria such as Zymomonas species are
responsible for alcoholic fermentation. Alcoholic fermentation is a metabolic process in
which microbes degrade their substrates to produce ethanol or alcohol. Alcoholic beverages
including beers, champagnes, wines and distilled spirits are produced through alcoholic
fermentation processes. Alcoholic fermentation extends the shelf-life and/or keeping quality
of food/beverage products; and it also improves on the physical features of the end-products.
Alcoholic beverages enhance the flavour of the end-product; and it is mainly used to change
the parent foodstuff (substrate) to a new and improved food product. These beverages are
mainly manufactured from locally available fermentable substrates which are sugar based.
These sugar based materials or substrates from which alcoholic beverages are manufactured
from include rice, sorghum, wheat, millet, maize and barley. The microbes involved in these
alcoholic fermentations are mainly strains of S. cerevisiae – that on their own cannot directly
ferment starch without a prior enzymatic hydrolysis of the substrate (starch) to simple sugars
(e.g. glucose). As aforementioned, rice, sorghum, wheat, millet, maize and barley are the
major source of carbohydrate substrates for beer production. The type of yeast used in beer
production impacts hugely on the flavor and texture of the drink depending on the type of
beer being brewed.

Brewery Processes

1. Malting
2. Cleaning and milling of the malt
3. Mashing
4. Lautering
5. Boiling
6. Fermenting
 7. Conditioning
8. Filtering
9. Filling.

Malting

The purpose of malting is to develop amylases and proteases in the grain. These enzymes are
produced by the germinated barley to enable it to break down the carbohydrates and proteins
in the grain to nourish the germinated seedling before its photosynthetic systems are
developed enough to support the plant. Not all barley strains are suitable for brewing; some
are better used for fodder. During malting, barley grains are cleaned; broken barley grains as
well as foreign seeds, sand, bits of metal etc. are removed. The grains are then steeped in
water at 10-15°C. The grain absorbs water and increases in volume ultimately by about 4%.
Microorganisms grow in the steep and in order not to allow grain deterioration the
steep water is changed approximately at 12-hourly intervals until the moisture content of the
grain is about 45%. Steeping takes two to three days. The grains are then drained of the
moisture and may be transferred to a malting floor or a revolving drum to germinate.

Cleaning and milling of malt

The barley is transported to the top of the brewing tower. At the top of the brewing tower, the
barley malt is cleaned of dirt and passed over a magnet to remove pieces of metals,
particularly iron. It is then milled. The purpose of milling is to expose particles of the malt to
the hydrolytic effects of malt enzymes during the mashing process. The finer the particles
therefore the greater the extract from the malt.

Mashing

Mashing is the central part of brewing. It determines the nature of the wort, hence the nature
of the nutrients available to the yeasts and therefore the type of beer produced. The purpose
of mashing is to extract as much as possible the soluble portion of the malt and to
enzymatically hydrolyze insoluble portions of the malt and adjuncts. Mashing may be
regarded as an extension of malting. In essence mashing consists of mixing the ground malt
and adjuncts at temperatures optimal for amylases and proteases derived from the malt. The
aqueous solution resulting from mashing is known as wort.
Lautering

Lautering is the separation of the extracts won during mashing from the spent grain to create
wort. It is achieved in either a lauter tun, a wide vessel with a false bottom, or a mash filter, a
plate-and-frame filter designed for this kind of separation. Lautering has two stages: first wort
run-off, during which the extract is separated in an undiluted state from the spent grains, and
sparging, in which extract which remains with the grains is rinsed off with hot water.

Boiling

Boiling the wort ensures its sterility, and thus prevents infections. During the boil, hops are
added, which contribute their bitterness, aroma and flavour compounds to the beer. Along
with the heat of the boil, they cause proteins in the wort to coagulate and the pH of the wort
to fall, and they inhibit the later growth of certain bacteria. Finally, the vapours produced
during the boil volatilize off-flavours, including dimethyl sulfide precursors. The boil must be
conducted so that it is even and intense. The boil lasts between 60 and 120 minutes,
depending on its intensity, the hop addition schedule, and volume of wort the brewer expects
to evaporate.

Fermentation

Fermentation, as a step in the brewing process, starts as soon as yeast is added to the cooled
wort. This is also the point at which the product is first called beer. It is during this stage that
fermentable sugars won from the malt (maltose, maltotriose, glucose, fructose and sucrose)
are metabolized into alcohol and carbon dioxide. Fermentation tanks come in all sorts of
forms, from enormous cylindroconical vessels which can look like storage silos, to five
gallon glass carboys in a home brewer’s closet.

Conditioning

When the sugars in the fermenting beer have been almost completely digested, the
fermentation slows down and the yeast starts to settle to the bottom of the tank. At this stage,
the beer is cooled to around freezing, which encourages settling of the yeast, and causes
proteins to coagulate and settle out with the yeast. Unpleasant flavours such as phenolic
compounds become insoluble in the cold beer, and the beer's flavour becomes smoother.
During this time pressure is maintained on the tanks to prevent the beer from going flat.
Filtering

Filtering the beer stabilizes the flavour, and gives beer its polished shine and brilliance. Not
all beer is filtered. Filters range from rough filters that remove much of the yeast and any
solids (e.g. hops, grain particles) left in the beer, to filters tight enough to strain colour and
body from the beer. Normally used filtration ratings are divided into rough, fine and sterile.
Rough filtration leaves some cloudiness in the beer, but it is noticeably clearer than unfiltered
beer. Fine filtration gives a glass of beer that you could read a newspaper through, with no
noticeable cloudiness. Finally, as its name implies, sterile filtration is fine enough that almost
all microorganisms in the beer are removed during the filtration process.

Filling/Packaging

Filling (also known as "packaging") is putting the beer into the containers in which it will
leave the brewery. The containers are usually bottles, cans, or kegs; sometimes bulk tanks are
used for high-volume customers. The beer is not allowed to come in contact with oxygen
during this operation; it is also not allowed to lose CO2, or to become contaminated with
microorganisms. To achieve these objectives, the beer is added to the tanks under a CO2,
atmosphere, bottled under a counter pressure of CO2, and all the equipment is cleaned and
disinfected regularly. Bottles are thoroughly washed with hot water and sodium hydroxide
before being filled. The filled and crowned bottles are passed through a pasteurizer, set to
heat the bottles at 60°C for half hour.