Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

2 General Certificate in Brewing

 Introduction.

The General Certificate in Brewing (GCB) gives international recognition of a basic, under-pinning knowledge and
understanding in the principles of brewing operations.

The GCB has been designed for candidates who may have little or no formal academic or technical qualification. Typically a
candidate will be employed as a senior operator or team leader in a brewery or packaging plant, however the scope of these
examinations will enable candidates from smaller brewing operations to obtain this recognised qualification. This examination
is open to anybody with interest in brewing or beer packaging. They are a measure of basic knowledge (theoretical and
practical) underpinning brewing, packaging and associated operations.

o The GCB can be an end in itself, or the start of professional development, leading to the Diploma in Brewing
(Dipl. Brew) and, potentially, the Master Brewer (M. Brew) examinations. It counts as Recognised Prior Learning for
the Diploma in Beverage Packaging Module 2 Unit 2.5 Brewing.

o The GCB takes the form of one multiple choice paper of two hours.

Candidates can register to sit the exam on-line instead of using the traditional paper format. Candidates sitting within the
brewery or examination centres will be encouraged to take the on-line version.

The pass mark is set at 66% (40 correct answers from 60 questions) for General Certificate exams. Candidates attaining 90% or
more achieve a Distinction pass and 80 - 89% achieves a Credit pass.

Learning Material 2016 3

 The full list of sections in the GCB syllabus is as follows:-

1. Beer types; their raw materials; sweet wort production.

2. Sweet wort production (methods and plant).

3. Wort boiling.

4. Wort clarification, cooling and oxygenation (aeration).

5. The basic principles of yeast fermentation.

6. Fermentation practice.

7. Yeast management.

8. Beer maturation and cold storage

9. Specialist section –

Either 9A Bright beer preparation (for Mainstream brewery option A)

Or

9B Cask and craft beer preparation and packaging (for Craft beer option B)

10. Beer quality and process control.

11. Beer quality – Flavour.

12. Beer quality – Dissolved oxygen.

13. Beer quality – Microbiological contamination.

14. Quality management.

15. Plant cleaning – Detergents and sterilizing agents.

16. Plant cleaning – Cleaning in-place (CIP) and general cleaning.

17. Engineering basics and maintenance.

18. Utilities – Water and effluent in brewing

19. Utilities – Process gases.

20. Brewing and the environment.

4 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 5

Section 1 Beer types and their raw materials; sweet wort
production.

1.1 Definition of Beer

In its basic sense, beer is an alcoholic beverage produced by • The use of a malt that is relatively undermodified and
the fermentation of sugars derived from malted barley and lightly kilned.
flavoured with hops. There are some minor differences • A relatively low bitterness.
where malt is supplemented with adjuncts or where the • The use of a bottom fermenting yeast, probably
hops are replaced by other flavours, but this definition selected by the extended cool brewing storage
would be recognised by the majority of people round the processes.
world. • Cold maturation.

The manufacture of all alcoholic beverages utilises the Note however that there are also dark lagers brewed, using
ability of yeast to ferment sugar into alcohol. darker malts for stronger flavoured beers.

Ales are produced traditionally in the United Kingdom and

the Republic of Ireland, though increasing volumes are now
SUGAR YEAST ALCOHOL produced around the globe, principally in micro-breweries.

Their flavours come from:-

• The use of a well modified and biscuity flavoured malt
Wine is made from grapes, cider from apples, whereas in which is sometimes highly coloured, leading to malty
the case of beer, the sugar is derived from malted barley, and toffee characteristics and rich amber or dark
and flavour and character comes from the addition of hops. colours.
• Sometimes they are very bitter.
The full process also involves preparing the immature or • The use of a top fermenting yeast, though again, many
green beer for consumption. beers are now produced using bottom fermenting
yeasts.
• Fermentations which are warmer and quicker than
lager fermentations, leading to higher levels of fruity
flavours.

Ales come in various forms, bitters, pale ales and mild

beers.

Wheat beers were originally produced in Belgium (Wit

Beers) and Germany (Weiss Beers) using large proportions
of malted wheat instead of malted barley. They are usually
brewed using a top fermenting yeast. The beers are often
served unfiltered or bottle conditioned with noticeable
yeast content and cloudy appearance.
Beer types: Stouts are very dark in colour and richly flavoured from the
use of highly coloured malts or roasted barley. Other
Different types of beer. characteristics include
Different areas around the world have developed their own
• The use of top fermenting yeasts.
types of beer.
• Warm, fast fermentations.
• Possible burnt and or bitter aftertaste, due to the malt
The variations have come about through a combination of
or roast barley.
the materials available for its manufacture and the tastes of
• Traditionally, high alcohol content, though more
the consumers.
recently stouts usually have alcohol levels similar to
other ales.
Lager. The German for “store”. This beer type forms by far
the largest proportion of beer sold. The beer is typically
Low alcohol / alcohol-free beers are produced by several
light yellow / gold in colour, with the delicate flavour due
different processes and their definition varies in different
to:-
countries.

6 General Certificate in Brewing

Usually alcohol-free means less than 0.05% (vol/vol) alcohol seed is germinating. Usually the starch is locked away or
and low alcohol means less than 0.5% (vol/vol) alcohol (less protected until it is needed.
than 1.2% in UK). The exact definition is set by individual
governments. Close up of the
starchy 'endosperm'
• Often produced by removing alcohol from standard
strength beers (for example, by evaporation or reverse Starch granules
osmosis methods). BARLEY
• Can be produced by limited fermentation processes CORN Gum cell wall
either by using wort with a very low fermentability or by
Protein
exposing wort to yeast at cold temperatures and/or for
a short time. Husk
Shoot
Low alcohol and alcohol free beers must not be confused Aleurone layer
with malt drinks, which are essentially unfermented wort.
Endosperm
Germ
Low-carbohydrate beers are brewed by producing wort that
is more fermentable than in “standard beers” by several
techniques. This could be by extending the malt mashing Root
time to create more fermentable sugar, but could also be
by adding additional enzymes to convert more of the non- The diagram above illustrates the key features of the barley
fermentable sugars into fermentable sugars. These corn. It shows the location of the starch granules which are
enzymes may be produced from unboiled wort and added the main carbohydrate food reserves.
to conventional wort, or from commercial suppliers derived
from fungal and/or bacterial sources and added during wort Starch is present as granules which are embedded in a
production or during fermentation. protein matrix. This matrix is surrounded by cell walls
containing a gum called β-glucan. The starch granules are
The overall objective by making the wort more fermentable therefore inaccessible and protected from attack by the
(or “super-attenuated) than standard is to brew products amylase enzymes that are produced during germination.
that have lower carbohydrate content in the finished beer.
During the malting process however, the cell walls and the
protein will be dissolved by other enzymes which are
produced naturally as the seed grows.
1.2 Malt and Barley
Barley is the principal grain used in brewing for a number of
Apart from water, malted barley is the main raw material reasons:-
used in the brewing of most beers. Malt provides the sugar • The plant can be grown in many parts of the world
that will be fermented into alcohol in the brewing process. ranging in latitude from near the polar circles to the
equator.
Barley is a cereal traditionally grown in mild maritime • Its uniform and convenient size makes it easy to handle
climates and for centuries it has been used in the on an industrial scale.
production of beer. • The grain contains 60 – 65% by dry weight of starch.
Together with proteins, enzymes, vitamins and minerals,
Malting Barley the grain provides a complete package for yeast
nutrition.
• It contains sufficient lipids for yeast metabolism under
anaerobic conditions, in some other grains excessive
levels of lipids can have deleterious effects on beer
processing or quality.
• The husk is relatively tough, and can form a filter bed in
the brewhouse.

The barley selected for processing into malt must meet

certain specific requirements:-
• It must be capable of germination, with a minimum of
95% of the barley corns ready to grow. The key stage
of the malting process is germination when the barley
All cereals contain carbohydrates in the form of starch seed starts to grow. Barley that is not ready to grow,
which is the source of food for the growing plant when the sometimes referred to as ‘dormant’, is not suitable for
malting.

Learning Material 2016 7

• It must have an acceptable balance between protein Steeping:
content and carbohydrate content, the balance struck Barley is soaked in water to simulate the conditions that
to be determined by the beer type being brewed and start germination or growth. This is carried out in a steep
the brewhouse processing equipment being used. tank.
• The grains should be of an even size. That way they are
more likely to grow evenly. STEEPING
• The grains should be consistent colour, helping indicate
the same barely variety and lack of damage due to for
instance, moisture. Water
• The grains should be large. Large corns are easier to
process when the malt gets to the brewery. Barley
• The barley must be of a ‘malting variety’. Malting
barleys are low in protein and the cells containing Steep Tank
starch as described above, are easier to break down.
• The corns must be undamaged, free of split or pre- During steeping the grain is aerated, (normally by draining
germinated grains and free of disease or pests such as and drawing air through the wet grain bed, before
beetles or moths. resoaking) to reduce the numbers of grains dying off due to
• They must be free of other cereals, or other barley “drowning” and to increase the rate of water uptake. The
varieties. barley is usually steeped and aerated a number of times - at
• The moisture level must be suitable. If freshly the end of steeping the moisture content of the barley
harvested, not more than 18%, and suitable for drying should be around 45%, dependant on the type of malt
to 12% prior to storage at the maltings. being produced.

The Malting Process Germination:

On completion of steeping, the barley seed is allowed to
The purpose of malting is to:- grow. During germination two major changes occur:
• Make starch readily available during the mashing
process to be converted to a range of fermentable and Firstly, hormones stimulate the production of enzymes in
unfermentable sugars. the aleurone layer.
• Provide a source of amino acids and proteins for the
yeast to be able to grow healthily during fermentation. Secondly, these enzymes start to act. During malting they
Note that some of this protein breakdown may take will break down the gummy cell walls and break down the
place in the brewhouse, depending on the beer type, protein matrix inside the starch containing cells. This
malt type and brewhouse equipment. breakdown releases the starch granules making them
• Develop desirable colours and flavours which are not accessible for conversion into sugar. The changes taking
present in barley itself. place during germination are called ‘modification’.
• Produce a final product which is stable, capable of
storage and transport to the brewery. The maltster can influence the degree of modification
• Produce a food product which is wholesome and meets during malting by controlling the moisture content of the
food quality criteria. grain, its temperature and the time allowed for
germination.
The malting process:
During germination the seed grows rootlets and a shoot.

STEEPING GERMINATION KILNING Close up of the effect

The seed is The barley The malt is of enzymes on the
endosperm.
soaked in grows under dried out GERMINATING
water to controlled and colour BARLEY
Cell walls dissolved.
start it conditions and and flavour
growing the 'changes' are Protein dissolved.
occur inside the developed
seed Starch granules
released
Shoot

There are three stages in the process of converting barley

into malt:-
• Steeping Enzymes released from
• Germination the aleurone layer
• Kilning. Roots

8 General Certificate in Brewing

Germination usually takes place in a chamber or vessel The malt kilning process is manipulated so that the malt is
where air is blown, or more normally drawn through the dried at a relatively low temperature (around 50°C) using
growing malt to prevent it suffocating in the CO2 produced, high flows of air. When the malt is dry, with a moisture
and to control its temperature and moisture content. content of around 10%, the kilning temperature is
°
Turners mix the malt to prevent the growing roots from increased (up to 90 C) so that the malt develops colour and
matting together and creating masses of grain impermeable flavour.
to the air. The time required for germination is typically
around 4 days. At the completion of kilning, the malt’s moisture content
will be 3 - 5%. The finished malt is normally allowed to rest
GERMINATION for at least two weeks before use as this produces a more
consistent final product for the brewer to use.
Malting 'Box' Turner

Growing Barley

Plant
Air Conditioning
KILNING

Kilning:
During this stage of the malting process, water is removed
from the green malt. The malt then becomes stable and can
be stored without deterioration. The malt may also be
slightly roasted to give it colour and flavour.
Burner
Some of the enzymes, for example those required later in
the brewing process for starch and protein conversion must
be preserved. The combination of high grain moisture and
high temperature would normally destroy the enzymes The table below details the changes that occur during the
developed during germination. malting process:-

Parameter Barley Germination Malt

Moisture About 12% after drying on the About 44 - 48% after steeping. 3 - 5% after kilning.
farm or maltings.

Extractable Virtually zero because the starch Very high because the starch granules Kilning does not change the level of extractable
carbohydrate is protected. have been released. They are now carbohydrate but it does fix it by reducing moisture
accessible to enzymes that convert and stopping germination.
starch into sugar.

Colour Very low. Very low. Colour is produced when sugars and soluble protein
react together at high temperature.

An increase in colour occurs depending on the degree

of kilning and the levels of sugar and soluble protein
present.

Protein Malting grade two-rowed barleys The overall level of nitrogen does not Kilning temperatures will reduce some enzyme
for pale ale malts have nitrogen change, but a lot of the protein is activities by denaturing the protein.
Calculated from total contents of about 1.4 – 1.6% (8.8 converted into a more soluble form
nitrogen (TN) content – 10% protein). by enzymic action during Lighter kilned malts (lower colour) tend to have higher
TN x 6.25 = % protein Two-rowed lager malts may have germination. enzyme levels).
more nitrogen, typically 1.5 – The important parameter is the ratio
1.8% (9.4 – 11.3% protein). of the Total Soluble Nitrogen (TSN) to Dark malts (see Section 2.2) have no enzyme content.
Some brewers use six-rowed the Total Nitrogen (TN) in the malt.
barleys, which have much higher There are several ways of measuring
nitrogen contents, typically 1.9 – this parameter, based on the type of
2.2% (12 – 13.5% protein). mashing system used for the analysis.
Soluble nitrogen (protein) includes all
the malt enzymes.

Learning Material 2016 9

The extent to which the barley endosperm cell walls, Typical analysis of ale malt using IoB methods
proteins and to a lesser extent the starch granules
themselves are broken down is termed the ‘Degree of
Modification’.

Lager malt contains enzymes from the aleurone layer, but

without extensive breakdown of the cell walls and proteins,
and the malt grain remains comparatively hard and is not
very friable. Lager malt is termed ‘undermodified’.

Ale malt normally has extensively broken down (modified)

cell walls and intracellular proteins. The malt grain is softer
and friable compared to lager malt. Ale malts are generally
described as ‘well modified”. Malt checks at malt intake
The brewer should always check the quality of the malt
Because of the lack of protein breakdown in lager malt, prior to intake into the brewery malt handling system.
beers brewed using lager malt may require some additional Checks typically include
processing, to enable further protein and β glucan • Verification of type and batch against delivery plan -
breakdown during mashing in the brewhouse. This may ensure load/delivery details match the delivery
require the use of decoction mashing (requiring mash schedule prior to unloading.
kettles), rising temperature infusion mashing (mash vessels • Visual assessment to ensure the malt is free from pests
with heating and stirring facilities) and/or additions of such as beetles, weevils or moths.
enzymes produced by bacteria or fungi to the mash to • Visual assessment to ensure the grains are of uniform
ensure appropriate breakdown of the starch granules into and adequate size. This may be backed up by a
sugars. screening test where a sample is checked using a
shaker with fixed slot sizes of a number of sizes to
Beers brewed using ale malts may be brewed in simple check particularly for undersized grains. Large corns
mash tuns, with no additional mixing or heating, although yield more extract. A range of corn sizes indicates
modern larger breweries typically use mash mixers with poorly screened barley or uneven germination and will
heating and mixing facilities, and heat up from the mash also result in extra brewery screenings or poor milling.
°
temperature to circa 77 C prior to wort run off. • Visual assessment to ensure the grains are free from
broken grains and missing husk, which can create
Coloured malts may be used with any mashing system. unnecessary dust and losses.
• Visual assessment to ensure the grains are free from
Adjuncts used in addition to malt may also need specific other seeds, stones, metal, string etc.
processing equipment or conditions in the brewhouse to • Visual assessment to ensure the grains are not
enable their use (see section 1.3). different colours (‘magpie effect’) – due to uneven
kilning conditions
The principal constituents of malt • Visual assessment to ensure the grains are free from
mould. Malt infected during germination can cause
Constituent % content of malt gushing. Post kilning mould infection has mycelium
Starch 58 over the surface which tends to bind corns together
Sucrose 3–5 and smells mouldy. Such mould aromas are easily
Soluble Gum 2–4 transferred to beer.
Hemicellulose 6–8 • Cut or bite. Well modified malt is friable. A longitudinal
Protein 8 – 11 or horizontal cut will reveal steely (hard, unconverted /
Amino acids/peptides 1–2 undermodified) parts of the grain or, in the case of
crystal type malts any non-glassy (undermodified)
Typical analysis of lager malt using Analytica-EBC methods areas.
• Flavour malt grains are sucked, not chewed - husk has a
high silica content and is abrasive. Pale malts should
have a slightly sweet, biscuity flavour and as colour of
the malt increases so the biscuity nature increases until
in chocolate and darker malts, distinctly acrid flavours
predominate. No off notes should be detected.
Notes.
Draw a flow diagram of the malting process. Make notes of
the inputs and outputs.
Why can kilned malt be stored and green malt not be
stored?
Why is it easier to mill (crush) malt than barley?

10 General Certificate in Brewing

1.3 Adjuncts and Coloured Malts

Adjuncts are solid or liquid brewing raw materials that are Amber malt is produced by roasting almost fully dried malt
used to supplement the malt in the grist. (the level prior to final kilning) in a drum to give it a slightly
higher colour and biscuity flavour. Colour typically 90 – 190
O
They are used for a number of reasons:- EBC. This can be used as an alternative to crystal malt,
giving a drier finish to the beer than crystal.
• To change the character of the beer by altering its
colour or flavour. Brown malt is produced from standard malt that has had
• To improve the quality of the beer, for example extra kilning, usually by wood burning fires. It is used to add
improve the head stability, increase (or decrease) wort a lot of colour and an oaky character to the beer. Colour
O
fermentability or reduce the potential for haze typically 140 - 160 EBC. Often used in porters and stouts.
formation.
• To increase the capacity of the brewhouse by the Black malt and Chocolate malts are produced by roasting
addition of liquid adjuncts to the wort boiling vessel finished malt in a drum. Both malts have a very high colour
(copper/kettle). and a dry bitter flavour. They are used in stouts to give a
• To reduce production costs. very dark and highly flavoured beer. Very small quantities
• To increase brewhouse capacity. may be used to add colour to bitter type beers, without
• To improve brewhouse yield by, for example, replacing adding the flavour that crystal or amber malt would give.
O
some malt with sugar syrups. Colour typically 1200 – 1400 EBC.

Roasted Barley is used to contribute colour and the

Categories of Adjunct. distinctive burned coffee flavour to stouts. Colour typically
O
900 – 1500 EBC.
There are four major categories of brewing adjunct:-
Wheat
• Malted cereals that are used in the grist along with the Wheat is a cereal like barley and it can be malted in the
malted barley. same way. It does however, have different characteristics.
• Processed cereals that are also used in the grist. For example it has a very thin husk and its starch is less
• Unprocessed cereals that require additional processing protected. The flavour it produces is different and the
in the brewhouse. nature of its protein is different from barley protein,
• Sugars or syrups which are added to the copper/kettle increasing head stability, but it will not clarify on the
or later in the process. addition of finings.

Coloured Malt Malted Wheat is used as the main carbohydrate source in

Coloured malts are used to increase beer colour, and or to Munich Weissbier. It contributes to the beer’s distinctive
modify flavour. Because of their nature they produce a appearance, colour flavour and outstanding head stability.
more stable beer. During the extra kilning used for coloured It may in extreme cases be used at up to 50% of the grist.
malts, the proteolytic and amylolytic enzymes will have
been destroyed. Torrified Wheat is produced by heating the moistened but
unmalted grain to rupture the internal structure and
Crystal malt is produced by a different kilning procedure. release the starch so that it is accessible when mashed in
Un-kilned germinated (green) malt, or kilned pale malt the brewhouse. Torrified wheat is used at up to 10% to
rewetted to achieve high moisture content is heated on the improve the beer’s head stability and because it is cheaper
kiln and is ‘stewed’ before it is dried and kilned (again). This than malt, to save costs.
produces a high colour and a distinctive toffee flavour.
Crystal malt is used in ale brewing to provide a rich red Wheat Flour is produced by milling wheat, the process
colour and a distinctive flavour. Colour typically 140 - 170 releases and separates starch from the embryo and the
O
EBC. protein that is present at high levels. It is used at up to 10%
to improve the beer’s head stability, to reduce protein
Carapils and Munich malt are similar to crystal malt but levels in the grist and to save costs because it is much
they have a lower colour and a more delicate flavour from cheaper than malt.
using undermodified malt followed by less kilning.
Maize
Carapils and Munich malt are used to add colour and Maize (or corn) is a common crop grown in warm and
flavour to lagers. Munich malt has a colour of temperate climates. It is a cheap source of carbohydrate.
O
approximately 17 – 30 EBC. Carapils has a colour of 15 – 30 The starch is readily accessible but it must be ‘gelatinised’
O
EBC. at high temperature before it can be converted into
fermentable sugar. Maize is typically used at up to 20% of
the grist in lager to reduce malty flavours and produce a
clean delicately flavoured beer.

Learning Material 2016 11

Maize grits are produced by milling the maize and at the Sucrose can be added to the beer after fermentation as
same time removing the germ which contains protein and ‘primings’ to provide sugar to encourage conditioning or to
oil. Maize grits must be cooked in the brewhouse to increase sweetness.
gelatinise the starch. Maize grits are cheaper than malt and
can reduce costs. Invert is produced by hydrolysing sucrose and it can be
liquid or solid. It is added to the copper/kettle and is used
Maize flakes are produced by processing grits through hot for the same reasons as sucrose although it has a more
rollers which gelatinises the starch and makes it accessible distinctive flavour.
to the malt enzymes.
Glucose is produced from starch and is used in liquid form
Rice in the same way that sucrose is used. Its fermentation
Rice is a very common crop and a major source of characteristics are very similar to sucrose.
carbohydrate. Rice is used in brewing for the same reasons
and in the same way (up to 30% of the grist) that maize grits High Maltose and Maltotriose syrups etc. are produced
and flakes are used. Both grits and cold rolled flakes require from starch and are used in liquid form in the same way
cooking with temperature stable enzymes before being that sucrose is used. Their fermentation characteristics
added to the mash. Steam treated rice, rolled into flakes depend on the sugar type so that they can be used to
may not require cooking if the heat treatment has been modify the fermentability of the wort and therefore the
adequate. character or alcohol content of the beer.

Oats Lactose is produced from milk whey and is used to

Although not widely used, oats can be added in flaked form contribute body and a creamy mouthfeel to milk stout. It is
to the mash tun or mash conversion vessel, where the malt normally added to the wort copper / kettle, but may be
enzymes can work on the starch in the oats. Typically oats added as priming sugar after fermentation. It is
are added to stouts in a style associated with those unfermentable.
traditionally brewed in Scotland. They give a smooth silky
mouthfeel and creaminess to stouts and porters. Caramel is extremely dark and has a burned toffee flavour.
It is produced from sugars and is used to contribute colour
Rye and flavour to beers like stouts and dark milds. It may be
Associated with German Roggenbier and made popular by added in the wort copper / kettle or post fermentation,
North American micro brewers, rye can be added as malted typically to adjust the beer colour, though some brewers
rye, or unmalted to the mash conversion vessel / mash tun, look for the distinctive caramel flavour to be evident.
or as whole grains to a cereal cooker at 10 – 20 % of the
total grist. The rye increases palate fullness, and a crisp Use of Adjuncts
slightly spicy flavour.
Malted cereals are used in the grist in varying proportions
Sorghum along with the malted barley.
Barley is not able to grow in semi-arid regions of the world
whereas sorghum grows well. It is possible to malt this Un-malted cereal adjuncts are typically used in the
cereal and use as a replacement for barley malt. However it brewery or distillery in one of three ways.
has a high gelatinisation temperature and therefore a
unique mashing process, involving heat stable enzymes, has Cereal cooker – in a cereal cooker the unprocessed
to be used. Like wheat, it is a ‘naked’ grain, which means adjuncts generally contain starch in their unrefined forms,
that its husk is thin and lost during handling. Consequently such as grits, flour, dry grain or starches. These adjuncts
it is best used with a mash filter. need to be gelatinised (to allow the starch molecule to be
enzymatically converted to fermentable sugars) and
Sugars liquefied to allow solubilisation and pumping to the main
Sugar can be grown naturally as in the case of sugar cane or malt mash in a second vessel where the malt enzymes can
beet. It can also be produced from starch, often from maize. now be used to modify the starch from the adjunct and
The method of production will dictate the type of sugar - create fermentable sugar.
sucrose from cane sugar, glucose or maltose from starch. A
range of fermentabilities and flavours are available. Sugars Mash conversion vessel – if the starch gelatinisation
are used at up to 30% of the grist, though most brewers use temperature is lower than that of the malt conversion (or
a considerably lower rate. saccharification) temperature required, or when the
adjunct has been pre-gelatinised by flaking or torrification,
Sucrose is mostly used in liquid form. It is highly or pre-refining (syrups), then the adjunct can be added
fermentable and is usually added to the wort copper / directly to the malt in the single mashing vessel.
kettle. It is used to supplement the malt where malt
processing plant (storage, mills, mash tuns etc.) is a limiting Brew kettle – liquid brewing sugars are usually added
factor. directly to the wort kettle, where it is readily dissolved in
the boiling wort.

12 General Certificate in Brewing

As well as un-malted cereals such as maize, rice, and wheat The production of fermentable sugars from starch is a
being used by brewers as adjuncts, the use of un-malted complex biochemical reaction starting with ‘gelatinisation’
barley is also common as it gives a rich and grainy flavour to of the starch by heat. This is where the spiral configuration
the beer (as well as being typically cheaper than the malted of the starch molecule is unwound so the enzymes can
equivalent). It will help improve foam retention at the attack.
detriment to physical stability due to the higher level of
nitrogen and proteins.

In order to improve the abilities of a malted cereal (such as

malted barley) to convert an un-malted adjunct to
fermentable sugar there are a number of techniques
available in the mash. High enzyme malts are available
which deliver the enzymes required to convert gelatinised
un-malted cereals into the highest amounts of fermentable
sugars. These malts are produced using specialised barley
varieties and processing regimes and are commonly used in
the grain distilling industry. The modern use of separately
produced enzymes in the mashing process - for starch
liquefaction in a cereal cooker, for saccharification in a mash
cooker, for mash separation improvement - or for
fermentability improvement, for beer filtration
improvement, or for optimal beer stabilisation downstream
of the brewhouse, has changed the range of a brewer’s
abilities over recent years as development and availability of Conversion follows and the diagrams below illustrate how
these enzymes has continued. the enzymes in the malt attack the long chains of sugar
units that make up the starch molecule and convert them
into fermentable wort:-
1.4 Mash Conversion

Mashing is the process where the grist of crushed malt or

crushed malt and suitable dry adjunct is mixed with water
under specified conditions so that enzymic action can take
place to convert the starch into fermentable sugar and in
certain cases break down proteins into more soluble forms.

Milling, Mashing and Conversion

Beer production starts in the brewhouse where the malt is

processed to release fermentable sugars.

MILLING MASHING CONVERSION

The malt Crushed malt The starch is
is crushed is mixed with converted into
water to start sugar by the
the conversion malt enzymes
process

First the malt is milled to grind the starch into flour while
protecting the malt husk because undamaged husk is
required later.

Then the milled malt or grist is mashed in with controlled

quantities of water of specified mineral composition and pH
at specific temperatures. This process brings the enzymes
present in the malt into action and they convert the malt
starch into sugar. If necessary, this starch degrading stand is
preceded by a proteolytic stand to break down the cell
protein content and release the starch granules.

Learning Material 2016 13

 temperature and pH (mash acidity), and mineral ions
The range of sugars produced during conversion present, particularly calcium which reacts with phosphates
determines the fermentability of the wort. If the enzyme from the malt, and results in a reduction in pH. They take
attack is complete, the wort will be very fermentable. If the time to work, so the length of time that is allowed for mash
enzyme attack is incomplete, the wort will be only partially conversion will affect the degree of conversion.
fermentable.
There are optimum conditions for mashing and these are
Enzymes are sensitive to the conditions that they work in. illustrated in the table below:-
They are affected by how much water is present,

Condition Low Optimum High

°
Temperature Low temperatures do not adversely 60 - 65 C High temperatures inactivate enzymes
affect the enzymes much, but the starch including α-amylases and β-amylases.
must be gelatinised first. The action of amylases is stopped at
°
Gelatinisation temperature for malt temperatures over 70 C.
°
starch is between 60°C and 65 C,
dependant on barley variety.
pH Acidic conditions kill the enzymes. 5.4 High pHs slow enzyme action, but it does
Enzyme action is stopped if the pH is continue at pHs of 7 or above.
below 5.0
Water Enzymes are more sensitive to heat in a Between 2.5 Enzymes are less sensitive to heat in a
(mash thickness) thin mash. and 3.5 litres of thick mash. There is a higher
The enzyme is degraded more quickly in water per concentration of enzyme and starch in a
thin mashes, and because there is a kilogram of dry thick mash.
lower concentration of enzyme and grist.
starch in a thin mash, contact between
the starch and enzyme is not so easily
achieved.
Thicker mashes also have higher
viscosity and results in slower sugar
extraction, particularly in wort runoff.
Time Enzymes take time to attack the starch. 30 minutes Conversion will be virtually complete
Conversion will be incomplete in less after 30 minutes. A longer time will not
than 30 minutes. increase the yield of sugar but may make
it more fermentable.

14 General Certificate in Brewing

Proteolysis is the term used to describe enzyme action that Rising temperature infusion mash – lager
breaks down proteins into simpler soluble forms. The action
of proteolytic enzymes is very similar to that of the starch
breakdown enzymes except that their optimum
temperature is slightly lower at 50 - 54°C and pH 5.5.

• It becomes necessary for proteolysis to take place

during mashing when the malt is undermodified and
the proteins surrounding the starch granules have not
been completely broken down during malting (see
section 2.1).

• Mashes with undermodified malt, for example lager

malt, will allow for this by having a low temperature
stand for the proteolytic enzymes to work, followed by
a ‘saccharification’ stand for the starch enzymes to
work. °
The temperature rise to 77 C at the end of the
• Mashes with well modified malt only need a amylolytic stand is to improve filterability in the
saccharification stand. wort separation system by reducing the viscosity,
and to stop any remaining enzymatic activity which
Amylolysis is the term used for the breakdown of starch would affect wort fermentability.
into sugars of varying degrees of complexity. α-Amylase,
which randomly attacks the starch chains has an optimum Monitoring starch breakdown
temperature of 67°C, and pH of 5.2. β-Amylase, which
attacks the ends of the starch chains has an optimum At the end of the saccharification process it is
temperature of 62°C, and pH of 5.25. The amylolytic stand advisable to check that the starch has been fully
temperature is therefore a compromise of the two optima broken down into sugars, and no starch remains.
to achieve the desired fermentability. This is quickly carried out using the “iodine” check.

β-Glucanase, which breaks down the β-glucans in the The iodine colouration with starch and higher
endosperm cell walls has an optimum temperature of 56 °C, dextrins only occurs in the cold mash, so the mash
and pH of 6.0, which is why it is sometimes considered sample must be cooled. The cold mash sample is
necessary (where permitted) to add additional β-glucanase then brought into contact with a drop of tincture of
to the mash. 0.02N iodine solution in a porcelain dish or block. No
dark blue / black colouration of the yellowish iodine
These principles are illustrated in the examples below:- solution, which would indicate the presence of
unconverted starch, must occur.
Ale mash with final temperature rise -

1.5 Grist Composition and Extract

Performance

The components of a brewing grist: The ingredients

used in a brewing recipe determine the brew’s
volume and the beer’s alcoholic strength and
flavour. Complex calculations are required to
ascertain how much of each component is needed
to end up with the desired beer.

The following example illustrates the principles of

the calculations to produce 50,000 litres of wort
with a specific gravity (SG) of 40 degrees.

Learning Material 2016 15

Malt - 95% • All materials that contribute to the carbohydrates in
the brew have an extract value. This may be stated in
Contribution – from a malt with extract value of 300 litre litre degrees per kilogram: this means that one
degrees per kilogram. kilogram of the material will contribute ‘300 litre
degrees’ to the brew. A litre degree is one litre at one
50,000 litres X 40 degrees X 95% = 6,333 kg degree. Our brew needs 50,000 litres times 40 degrees
300 litre degrees per kilogram = 2,000,000 litre degrees.

• Note that different materials have different amounts of

Coloured malt 5% available extract. For instance, pale ale and lager malts
have an available extract of around 300 - 310 litre
Contribution - Extract value of 250 litre degrees per degrees / kg. Coloured malt such as crystal malt has an
kilogram. available extract of around 270 - 275 litre degrees / kg.
High maltose syrup used for addition to the wort
50,000 litres X 40 degrees X 5% = 400 kg copper (kettle) has an available extract of around 310 -
250 litre degrees per kilogram 315 litre degrees / kg. Note that the values used in the
calculation have been adjusted for simplicity.

Water for mashing and sparging • The quoted malt extract values are always for ‘best
case’ and refer to laboratory values or ‘100% Extract
Contribution - Volume of water used for mashing and Efficiency’ (see below). Most brewhouses will not be
sparging. able to recover 100% of the available extract, and this
will have to be factored in to the grist calculation. This
Approximately 8 litres of water per kg of dry grist simplified calculation assumes that 100% of the
(6,333 + 400) X 8 = 53,864 litres available extract in the malt is extracted into the wort.

Compensation for losses is made below.

Brewing Water:-
Product water (brewing water and water used in the
Make-up water production of beer, i.e. it will eventually be consumed by
the customer) makes a major contribution to the quality of
Contribution – To dilute the boiled cooled wort to the the beer that is produced.
required specific gravity.
Salts dissolved in the water affect the beer’s flavour, they
Approximately 0.75 litres of water per kg of grist is influence the pH (acidity/alkalinity) of the process and the
left in the spent grain. final product and they provide essential trace elements for
yeast growth.
(6,333 + 400kg) X 0.75 = 5,050 litres.
For more details of brewing water see Section 18.
Approximately 8% of water is lost through
evaporation during boiling.
Measurement and control of extract yield and efficiency
(53,864 litres – 5,050 litres) X 8% = 3,905 litres.
Malt is an expensive raw material and achieving good
Water from mashing and sparging – 53,864 litres extract levels is therefore very important.
minus spent grain 5,050 litres
minus evaporation 3,905 litres Extract Yield is a measure of how much of the available
44,909 litres material in malt and adjunct has been converted to useful
extract for the production of beer.
Water required to make up to 50,000 litres, with a specific
gravity of 40° = 50,000 – 44,909 = 5,091 litres. Extract Efficiency is a measure of the effectiveness of the
brewhouse in its use of malt and adjuncts. That is how
Explanations:- much material from the malt and adjunct has been
• The specific gravity is measured and as a true SG, converted, as compared to the total amount of extract
would read for example, 1.0400. However, for available to the brewer.
simplicity, the whole digit is removed, and so the SG is
specified as 40.0 (termed Brewer’s Degrees).

16 General Certificate in Brewing

Extract Yield is calculated as follows:- The malt supplier will normally perform this laboratory
analysis, expressed as the fine grind laboratory extract, on
Total amount of dissolved material in the wort divided by each batch of material produced. It is normally expressed
the total weight of raw materials used. ‘as-is’ (or as supplied to the brewery) or on a ‘dry’ basis, in
which case it can be corrected for the moisture content of
the material supplied.
Using Specific Gravity:

Volume collected X specific gravity = litre degrees / kg Example –

Weight of malt + adjuncts
Fine grind extract (as-is) – 310 litre degrees per kilogram.
Example - 10,000 litres of wort at a S.G. of 60° are collected
from 2000 kilograms of malt. The extract is:- Brewhouse extract yield – 300 litre degrees per kilogram.

10,000 X 60 = 300 litre degrees / kg. Extract Efficiency = 300 = 96.8%

2,000 310

300 litre degrees of extract was obtained from

every kilogram of malt used. Example –

Fine grind extract (dry basis) – 320 litre degrees per

Or using degrees Plato and EBC extract units: kilogram

The relationship between degrees Plato and specific gravity Malt moisture – 3%
(SG) is not linear, but a good approximation is that 1° Plato
equals four “brewer’s degrees”; thus 12° Plato corresponds Fine grind extract (as is) =
to an SG of 48.
320 x (100-3) = 310 litre degrees / kg
Example - 10,000 kg of wort at a S.G. of 15° Plato are 100
collected from 2000 kilograms of malt. The extract is:-
Extract Efficiency = 300 = 96.8%
10,000 X 15 = 75%. 310
2,000

75 % of the weight of the malt has been converted By calculating extract efficiency, a brewer can compare the
to extract. performance of the brewhouse equipment and procedures
and, unlike the calculation of extract yield, the variable
nature of the raw materials will not affect the result.
Both of these calculations are based upon the total weight
of raw material being used, and represent the brewhouse By knowing the typical extract efficiency of the brewhouse,
yield. a brewer can compensate for this factor when calculating
the components of a brewing grist.
Remember that a large percentage of the malt or adjunct is
insoluble, such as malt husk which is removed with the Note that most, if not all, brewhouses do not achieve 100%
spent grain, and does not contribute to brewhouse extract. extract efficiency. Potentially available extract from the
raw materials is lost for a number of reasons, including:-
A yield of between 285 and 300 litre degrees per kilogram,
or between 74% and 79% would typically be expected. • dust and grain losses in the malt intake, handling
and milling systems.
Extract Efficiency is calculated as follows:- • the wort separation system. Simple mash tuns
recover less than lauter tuns, which in turn recover
Total amount of dissolved material in the wort divided by less than modern mash filters.
the theoretical maximum amount of dissolved material • wetting losses throughout the brewhouse and
available from the malt and extract used. wort transfer system to the fermenting vessels
(FV).
By obtaining a theoretical maximum extract yield for each
of the malt and adjuncts using laboratory conditions, it is It is common practice therefore to calculate the brewhouse
possible to compare the extract obtained in the brewhouse extract efficiency based on extract actually achieved in the
with the maximum extract available in the malt and adjunct FV compared to the theoretically available extract.
used.

Learning Material 2016 17

Practice question (B) EBC/ASBC Method (° Plato)

Calculate the yield of malt extract, and the extract efficiency °Plato is % weight/weight, or kg extract / kg wort.
of the following brew :-
Given that we have a volume of wort (200hl), and not a
3,000 kilograms of malt supplied at 300 litre weight of wort, we need to perform a simple conversion
degrees / kg (78.4% available extract) are used. using specific gravity.

200 hectolitres of wort is collected. 200 hl = 20,000 litres of wort

The original gravity is 1.044° SG (44° brewers 20,000 x 1.044 = 20880 kg of wort
degrees or 11° P)

Now we can use 11°P to convert to kg of extract within the

Answers: mass of wort (11°P is equivalent to 11 kg extract per 100 kg
of wort). So,
200 hl = 20,000 litres of wort at specific gravity of 1.044
20880 kg wort x 11 kg extract
100 kg wort
(A) SG Method:
= 2296.8 kg extract
Potential available extract = 3,000kg x 300 ldk

= 900,000 litre degrees Dividing by the mass of malt gives us:

Actual extract achieved = 20,000 litres x 44°

Extract yield = 2296.8 kg extract x 100
= 880,000 litre degrees 3000 kg malt

= 76.56 %
Extract yield = 20,000 x 44 = 293.3 litre degrees per kg.
3000
Extract efficiency = % actually extract x 100
% potential extract
Extract efficiency = % actually extract x 100
% potential extract = 76.56 x 100 = 97.7%
78.4
= 880,000 x 100 = 97.7 %
900,000 Notes.

Write down the ingredients used in a brew that you are

familiar with.

What is the theoretical (potential) extract of each of these

materials?

What is the volume of wort produced?

What is the gravity of the cooled wort before fermentation?

Carry out the above calculations using the material

quantities and extract potential of each of them.

What adjuncts, if any are used, and why?

18 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 19

Section 2 Sweet wort production (Methods & Plant)

2.1 Brewing process overview

Overview of the brewing process

The sequence of events from raw material intake to the kieselguhr free filter systems and stabilizing processes
production of wort for fermentation all occur in the up to and including bright beer tank.
brewhouse, as summarised below:- • If beer is to be packaged in cask, or as naturally
• Malt is taken into the brewhouse and stored until conditioned beer in bottle, after maturation, the beer
required. If small volumes of beer are being brewed, is normally filled into casks or bottles without
the malt is likely to be received and stored in sacks. filtration. Sometimes, beer is filtered first and yeast
This can be as whole malt, or pre-ground malt if the added back to allow in package conditioning.
brewery does not have a malt mill. In larger • Packaging of filtered beer in bottle can or keg is
operations, malt is normally received in bulk covered in detail by the General Certificate in
deliveries of a number of tonnes at a time, and Packaging.
transferred to malt silos.
• Adjuncts such as flaked maize, rice or wheat flours Brewery process overview diagram
may be received and stored, again in sacks or in bulk. The following diagram shows an example of the typical
Sugar adjuncts may be received in granular form, or stages of production of a brewery with a milling system, and
as syrups. final package into a variety of package types.
• The majority of breweries have their own mills. Malt
is taken from the malt storage area, screened to Bulk Malt

remove unwanted debris, including stones and metal, Malt Store Malt Silo
weighed and milled into a grist case.
Sack Malt Screening
• The malt and where used, adjuncts are mixed with
De-stoner
warm water (mashing) to allow release of
fermentable sugars (conversion). Weigher

• The wort is then separated from the grains, normally Magnetic

Separator
using a mash tun, lauter tun or mash filter. The sweet
wort extracted from the malt is boiled with hops (or Malt Mill

occasionally other ingredients) to stabilise the wort by Grist Hopper

inactivating the enzymes, to sterilise and concentrate Mash

the wort, and to extract the desirable flavours from Conversion

the hops or other ingredients. See section 3, wort Mash

boiling for details. The unwanted solid material, the Separation

spent grains are normally used for animal feed, but Wort Kettle

occasionally for biofuel. Whirlpool

• The boiled wort is then clarified to remove the bulk of Wort Cooler
the solids entrained in the wort, cooled to a suitable
Wort Aeration
temperature to allow the yeast to grow and aerated
to allow the yeast to grow healthily. See section 4, Yeast
Storage
Yeast
Pitching
Yeast
Propagation
wort clarification, cooling and oxygenation for details.
Yeast
• The cooled wort has yeast added (pitching) and is Recovery
Fermentation
Racking Tank Cask Beer

then allowed to ferment under controlled conditions Maturation

to produce green beer. See sections 5, 6 and 7 for
Cooling /
details. Chillproofing Filtration Dilution /
• The green beer is then matured, to remove the bulk Carbonation

of the yeast and allow the final desirable beer flavours Filtered Beer Pasteurisation
to develop, and undesirable flavours to be removed.
See section 8 for details. Bottle / Can / Bottle / Can /
Keg / Bulk Keg
• If beer is to be packed in bottle, can or keg, the beer is
normally filtered to remove the remaining yeast and
haze forming materials. See section 9 for details of
filtration processes including kieselguhr and

20 General Certificate in Brewing

2.2 Plant operation – grain handling &
milling ASBC analysis – 6 sieves
Sieve Mesh width Characteristic
The purposes of milling mm
The purpose of milling is to prepare the malt for mashing 1 2.0 Coarse husk held
and starch conversion by making the centre of the malt 2 1.4 Medium husk held
corn accessible. Where a wort separation system like a 3 0.5 Coarse grits and small husk
mash tun or lauter tun is used, milling must crush the starch held
into fine particles while preserving the husk so that it can 4 0.25 Medium grits held
be utilised as an effective filter during separation. Water 5 0.18 Fine grits held
may be added to the malt prior to milling to reduce the 6 0.15 Ordinary flour held
damage to the husk, either as a small percentage Base - Fine flour collected
(conditioning) or with the entire mashing water (wet
milling). Where a mash filter is used, the preservation of The husk volume retained by the 2.0 and 1.4 mm sieve may
the husk fraction is less important and a mill that crushes be weighed separately, the volume measured separately,
the whole dry grains into fine particles can be used. and the result converted to volume per 100 grams grist. It
is useful to be able to calculate these fractions separately
Malt must be screened before milling to remove unwanted and together. They provide a good guide to the lautering
material such as straw, stones or dust. The stones in capability of the grist. It has been found that when there is
particular are likely to damage roller mills used for lauter a husk volume of 600 mls / 100 gm of material retained by
tuns and mash tuns. Malt must also be screened using the 2 and 1.4 mm sieves, efficient extract recovery and total
magnets for hard ferrous objects as these can cause sparks, turnaround times can be achieved when using a lauter tun
which may lead to explosions or fire. or mash filter.

In general terms, the less well modified the malt, the finer it Typical critical grist fractions for a lauter tun where a six
needs to be ground, and the faster the extraction process, sieve laboratory analysis set is in use are as follows:
the finer the malt has to be ground.
• Top three sieves: Husk
Grist fraction analysis • Middle two sieves: Grits
The quality of the grist or crushed malt that leaves the mill • Bottom sieve and pan: Fines
has a major effect on subsequent performance in the • The husk fraction for conditioned malt should be >
brewhouse. 600 ml / 100g husk
• If it is too coarse, the starch will remain protected • The fines fraction for conditioned malt should be 10 -
from mash water and the enzymes will not be able to 15 % w/w.
convert it into sugar. The extract efficiency is also
likely to be low due to incomplete conversion and EBC analysis – 5 sieves
due to slow extraction of the sugars out of the large Sieve Mesh width Characteristic
particles during wort run-off. mm
• If it is too fine, wort separation will be slow because 1 1.27 Coarse husk held
the filter bed will become choked. Considerable 2 1.01 Medium husk held
quantities of fine solids from the malt are also likely
3 0.547 Coarse grits and small
to be washed out with the wort.
husk held
4 0.253 Fine grits held
Grist quality can be judged by ‘eye’ or by sieve analysis.
5 0.152 Ordinary flour held
• To the eye, the grist for mash tuns and lauter tuns
Base - Fine flour collected
should contain large pieces of empty husk and small
pieces of white grist and a little flour.
Note that in practice, the sieve sizes for both these sets of
• A sieve analysis is more objective and the mills
sieves often use values slightly different from the nominal
settings should be adjusted to give the required
values according to the manufacturer. However, the
(optimum) performance, in terms of extract
percentages obtained from each value vary little.
efficiency, run-off time and wort clarity for plant.
“Ideal” ratios of husk, grits and flour are specified by
Examples of grist analyses for mash tuns, lauter tuns and
the suppliers, and the actual grist is likely to be close
mash filters are shown in the following table. In practice the
to, but not exactly matching this ideal, due to
target percentage for each depends on whether emphasis is
variations in associated plant and the malt being
on extract or throughput (or these days both), malt quality,
milled. There are two widely used sets of sieves,
lautering and control capability, so there is no one optimum
each with a number of accurately manufactured
value.
mesh sizes set one above the other, EBC and ASBC.

Learning Material 2016 21

 Grist analysis EBC Typical 4 roll mill with screens only
Mash Lauter Mash filter
tun tun
Sieve 1
30 % 20 % 1%
> 1.25 mm
Sieves 2 & 3
24 % 45 % 9%
1.25 – 0.5 mm
Sieves 4 & 5
40 % 25 % 55 %
0.5 – 0.125 mm
Bottom
6% 10 % 35 %
< 0.125 mm

Malt mill operations

Brewhouse mills are designed to meet the requirements of
different types of malt and the different mashing and mash
separation systems in use.

Four roll mills

Four roll mills are often used for milling well modified ale
malts where the starch is readily accessible and a mash tun
will be used for mash separation. Because the malt is well
modified, and friable, the malt does not need to be broken
into fine particles for effective wetting and enzyme action.

A four roll mill is therefore generally considered adequate

for mash tun operations. The following describes the Six roll mills
actions of a 4 roll mill with beaters and screens. Six roll mills are often used for milling less well modified
• The feed roll controls the flow of malt into the mill. lager malts where the starch needs to be finely ground to
• The first (upper) pair of rolls crack open the malt to allow rapid wetting in the mash vessel. The husk has to be
release most of the endosperm. protected as complete as possible to allow rapid lautering
• The beaters and separation screens send fine and good extracts. The malt may be “conditioned” with
particles and the husks straight through to the steam or warm water prior to milling to help soften the
discharge and coarse particles through to the second husk, so making it less likely to break up into small pieces.
pair of rolls.
• The second pair of rolls crush the coarse particles. • The feed roll controls the flow of malt into the mill.
• The first (upper) pair of rolls crack open the malt to
Typical 4 roll mill with beaters and screens release most of the endosperm.
• The first (upper) screen sends flour straight through
to the discharge, grits to the third pair of rolls, and
coarse particles through to the second pair of rolls.
• The second pair of rolls crush the coarse particles.
• The second (lower) screen sends flour straight
through to the discharge, husk straight across the
screen to the discharge, and grits to the third pair of
rolls.
• The third pair of rolls crush the grits to produce fine
grits.

5 roll mills
This design of mill is very similar to the 6 roll mill. In effect,
one of the rolls of the first pair is used as one of the rolls of
the second pair, as indicated below. These are less
commonly used than 6 roll mills, as there is little real
financial gain.

22 General Certificate in Brewing

 Wet milling system

Steep hopper where the malt is

soaked.

Feed roll controls malt flow

Mash water supply.

Mill rolls crush the malt, the

husk being protected because
of its moisture content.

Mash mixing chamber.

Mash transfer.

Hammer mill
Typical 6 roll mill A hammer mill may be used if the mash is to be separated
in a mash filter. Here the filter bed is very thin and husk
protection is not necessary. A hammer mill produces a very
fine grind, giving good wetting and subsequently enzyme
activation, and rapid extraction of the sugars from the
particles.

Hammer mill

Malt inlet.

Rotating wheel with

hammers.

Screen only allows small

particles through.

Flour out.

Grain handling and safety

Typical 5 roll mill

Two roll mills

Two roll mills are most commonly used by smaller brewers.
The grist composition cannot be as accurately controlled
compared to those produced by four or six roll mills.

Wet mill
A wet mill may also be used for lager production. In this
system the husk receives extra protection because it is
steeped in water before milling proceeds. Typically these
only have a single pair of rolls.

Learning Material 2016 23

Storage It is usual to carry out further screening and dressing after
The different types of materials (grains, flakes, grits, and silo storage at the brewery, prior to milling.
flours) must all be stored separately until required for
processing. Magnets
It is essential that pieces of metal that may be in the malt
Most storage silos are normally constructed from steel but should be removed before they reach the mill, because
they can be made from concrete. Silos must have smooth such metal can cause a spark and start a fire or explosion.
walls with hopper bottoms to ensure easy grain withdrawal. Separation is effected by placing permanent magnets either
The malt and cereal adjuncts are stored at their delivery in the malt chute to the screening machine (dresser) or
moisture levels to:- across the feed to the mill.
• Discourage the growth of pests such as insects,
moulds, fungi and bacteria. Malt should flow over the magnet in a thin layer and at the
• Prevent alteration to the biochemical structure of same rate as it is being ground, thus allowing the magnet to
malt/adjunct prior to use (i.e. turning slack). extract any ferrous metal that may be in the malt.
Malt and adjuncts should be delivered and stored in
Dressing
sufficient quantities to defend against unforeseen
The malt dresser was usually a cylindrical screen revolving
shortages that could halt production. However, storage
inside a wooden casing that has detachable doors on either
should not be excessive – providing for only a few days’
side for easy access. The last part of the screen consists of
requirements. Otherwise money becomes unnecessarily
a mesh large enough to let malt pass through to a small
tied up in expensive storage capacity and the materials
hopper feeding the weigher or the mill. Any foreign matter
themselves.
such as pieces of wood, metal, or stone, which are too large
Weighers to pass through this mesh, is carried forward to the end of
The location of the weigher(s) varies depending on the the screen where it is rejected via a spout into a bag.
history of the design / build. Ideally, all malt (and adjuncts)
should be weighed after the malt has passed through the In modern installations there is a separator/dresser to
destoners, screens and magnets, so that only clean, usable remove foreign material based on size, and separately, a
malt is weighed. In the example shown, based on a de-stoner that separates material according to density. In
brewery, the weigher has been located at the silo this way small stones of the same size as the malt grains
discharge, to improve the accuracy of the charge of grist. can be removed.
Conveyors should only be stopped and started when empty
under normal conditions. The amount of malt a long Dust Removal
conveyor system holds can vary considerably, and can Dust is a dangerous substance because of the risk of
affect the volume / gravity of wort collected due to variable explosion and also irritation to the lungs. It is now covered
amounts delivered whilst emptying out the conveyors etc. by COSHH (Control of Substances Hazardous to Health Act)
when milling has been completed. regulations (and similar legislation outside the UK) and it is
extremely important that dust is not allowed to
Different sized weighers may be used for different malts accumulate. If a film of dust appears, measures must be
and adjuncts. For instance a brewery may use a 25 kg taken to eliminate the source of dust and any deposits
weigher for white malts, but a 2 kg weigher for coloured cleaned up. The presence of dust indicates a failure in the
malts. Each weigher requires dedicated feed conveyors and dust extraction system or leak in the plant.
cleaning systems. The discharges are normally merged
prior to the mill, but again, separate mills may be used for Fans suck the dust through metal ducts or pipes from
coloured malts and white malts. various points such as the elevators, dresser and weighing
machine. It is normally blown into a cyclone from which it
Screening and dressing drops down into a bagging point. A regular system of
To ensure uniformity of milling, it is necessary to have a emptying the dust sacks or containers is necessary to allow
reasonable consistency in the size of corns and the degree the plant to operate efficiently. Periodic examinations must
of modification. To obtain such consistency, prior to be made of the pipe ducts to and from the fan to avoid
despatch from the maltings batches of malt are often build up and blockage by dust.
mixed. To obtain consistency of size, the malt is screened.
To minimise unwanted material, it is “dressed” by passing Even if there is good housekeeping, it may not be possible
through screens to remove foreign objects by passing to completely eliminate the risk of explosions in hoppers
through magnetic separators to rotating, cylindrical, and conveying equipment. For this reason, explosion vents
oscillating or flat-bed screens. Not only are corns of are provided to allow an explosion to pass harmlessly into
unwanted size rejected (these are sold for animal feed the atmosphere without damage to equipment and people.
wherever possible), but foreign matter such as straw,
stones, string, sacking and metal particles are removed.

24 General Certificate in Brewing

Malt handling – key risks 2.3 Plant operation – mashing & conversion
Risk Potential Effect Prevention
Damage  Poor  Gentle Mashing Objectives
Brewhouse. handling. Ground malt and solid adjuncts (grist) are mixed with a set
performance.  Mechanical volume of water to achieve a specified temperature. The
 Excessive dust conveyors not mash is then allowed to stand for a period of time, typically
generated. pneumatic. around an hour, during which the enzymes in the malt
convert the starch to sugars to produce a sugary liquid
Moisture pick-  Biochemical  Keep system called wort. Depending on the type of malt, it may be
up change. dry. necessary to heat the mash to specified temperatures so
 Infestation.  Intake under different enzymes work close to their optimum
cover. temperature. During mashing:-
 Good • Cell wall components may be broken down to release
housekeeping the starch (non-isothermal mashes only, where the
endosperm has not been fully broken down during
Contamination  Damage to  Magnetic malting).
(stones, mills. extractor. • Proteins are broken down to amino acids.
metal)  Explosion risk.  Screens/ • Starch is broken down and converted to sugars.
explosion • The pH drops.
vent/ dust
extraction. The enzyme reactions are dependent upon:-
• The substrate and the enzymes available as they are
Environmental  Food safety.  Pest control. specific to each other, e.g. a proteolytic enzyme will
hygiene  Infestation.  Cover intake only breakdown proteins, not fats or starch.
hopper. • The duration of the temperature stand(s). This will
influence the level of substrate degradation and brew
house throughput.
Safety
• The pH of the mash. The activity of the different
Malt dust is hazardous, fine dust in the atmosphere is
enzymes will change according to the mash pH. pH is
explosive and breathing in the dust can cause respiratory
controlled mainly through the composition of the
problems.
brewing water. Additions of calcium and magnesium
• Malt mills are designed to prevent explosions. ions lower the mash pH. Bicarbonate salts from the
Magnets fitted to collect any steel or iron debris that liquor raise the mash pH by reacting with hydrogen
could cause a spark. Stone separators are also (H+) ions. It may also be necessary to reduce the
installed to prevent sparks and to protect the rolls bicarbonate (temporary hardness of the brewing
from damage/wear. water) and to add mineral salts to regulate the pH for
• The modern mill and malt handling plant is fitted with brewing. The final pH of the mash is a compromise
explosion doors which would direct a blast safely between the best pH for the different enzymes
outwards should an explosion occur. present.
• People working on the malt plant need to wear dust • The temperature. Enzyme activity changes with
masks to avoid breathing in any dust. temperature. Each has its own specific optimal
• Safe systems of work (permits to enter confined temperature. Destruction will occur at high temps,
spaces) are required for people entering malt silos. above the optimum for each specific enzyme.
• The milling plant and local environment must be kept • The grist to liquor ratio – will affect activity and rate
clean, accumulations of dust being particularly of degradation of the enzymes. This also affects the
hazardous. concentration of dissolved products. Generally
• Malt handling equipment is a noise hazard. The speaking, thicker mashes help protect enzymatic
design of the equipment and buildings can help, but action.
hearing protection in the vicinity of working
equipment is essential. At the end of mashing, most enzymes become inactivated
during the sparging process. Deactivation is completed
Notes during heating to boiling point.
Draw a diagram of the mill used in the brewhouse you are
familiar with. The wort should contain:-
• A range of sugars suitable for fermentation, leaving
Why was that specific design of mill chosen? sufficient unfermentable sugars to contribute to the
desired mouthfeel of the finished beer.
What safety features are incorporated into the malt • Proteins which will help form foam, essential to
handling and milling system in your brewery? presentation in most finished beers.

Learning Material 2016 25

 • Amino acids, to allow healthy yeast growth. wort / sparge flow through the bed as there are no rakes to
• Lipids and fatty acids, to allow healthy yeast growth. help break up a compacted bed.
• Mineral salts and vitamins, to allow healthy yeast
growth. After mashing in, typically to a depth of 0.9 to 1.2 metres,
but often considerably more, and sometimes somewhat
Mash conversion systems and their operating differences less, the mash is simply left to stand for a fixed period,
There are several different mashing systems and these before starting to run off the wort.
depend on the type of malt and adjuncts used and the type
of beer being produced.

Isothermal mash tun

The (isothermal) mash tun is a combined mashing in,
conversion and wort separation vessel. Well modified malt
is needed because there is no facility for mixing and
heating the mash, and so only isothermal (single
temperature) mashes can be made. They can only use well
modified malt, normally comparatively coarsely ground.
Poor quality malts or malts requiring a protein stand
cannot be handled. They are not particularly suitable for
large batch production. Brewhouse extracts are
considerably lower than obtainable from lauter tuns or
mash filters, though their simplicity makes them ideal for
small operations.
Mash conversion vessel
Prior to mashing in, the plates must be covered with hot The mash conversion vessel (MCV) is a vessel fitted with
water to pre-heat the mash tun and to reduce the amount heating and stirring facilities which can be mixed to ensure
of solid material from the mash blocking the plates, or homogeneity, particularly whilst heating, and to ensure
dropping through the slots or holes in the plates. good heat transfer. Less well modified malt can be used
here because different temperature stands can be used.
In larger operations, mashing in is then carried out using a However the mash has to be transferred to a lauter tun or
Steele’s masher. This is a rotating screw into which the mash filter for recovery of the wort.
grist drops. Water at the correct temperature is run into
the screw at the same time to achieve the required mash In many installations, the entire mash is mashed into, and
temperature. The screw “mashes” the grist which then converted in the MCV, prior to transfer to a lauter tun or
runs into the mash tun. It is rare for weak worts to be mash filter. However, the MCV may also be linked with a
added back to the mashing liquor. separate mash cooker, or a cereal cooker as described
briefly here:-
In smaller operations, the mash tun may simply be flooded
with the correct volume of hot water, and then the grist is • The mash conversion vessel with separate mash
added, simultaneously stirring in rapidly to wet the grain, cooker. This is the traditional decoction system which
and ensure there are no hot or cold spots in the mash. was in use before thermometers were readily
available, though is still used with vastly improved
Because no heating jackets are fitted, it is therefore not accuracy since the development of accurate control
possible to heat using external heat if the initial mash systems. The MCV in this case does not need heating,
temperature is low. Because of the lack of mixing facilities, but is simply insulated to reduce heat loss. Correct
it is very difficult to add extra hot (or cold) water and stand temperatures are achieved by transferring
ensure the mash temperature is consistent after addition, specified volumes of mash from the MCV across to the
particularly in larger tuns. The spent grains discharge cooker, boiling this portion of the mash up, and
rakes, if fitted will not ensure mixing, and may knock air returning it to the main mash. The mash has to be
out of the mash, so making run off more difficult. There transferred to a lauter tun or mash filter for wort
are also no cutting rakes similar to those fitted to the separation.
lauter tun which might be used to help mixing.
• The mash conversion vessel with separate cereal
The mash is then simply allowed to stand for a period to cooker. This decoction system is similar to above,
allow the enzymatic action to take place. During the except that the cooker is used to boil a mash of maize
period, the mash gradually rises due to air entrained in the or rice. The maize or rice is nowadays treated with
grist particles, so the bottom of the mash may be several enzymes which are stable and active at 80 C plus.
cm above the false floor plates. It is essential to maintain Maize and rice have high gelatinisation temperatures
the entrained air as this also helps to keep the mash and cooking is required if their starch is to be made
porous during wort run-off to allow consistent available for enzymatic action to convert the starch

26 General Certificate in Brewing

 into sugars. This process is avoided in many A mash rate of between 2.1 and 2.5 hl / 100 kg is generally
breweries by using pre-gelatinized maize or rice in used, though it may be up to 3.0. The false floor loading,
2
the form of flakes. The flakes may then be added expressed in terms of kg dry grist / m is typically around
2 2
directly to the MCV. 500 kg / m , though can be up to 800 kg / m .

The diagram shows an MCV with grist top entry, though in Decoction mash grist : water ratio
many newer installations, the grist enters at the bottom of A mash rate of between 2.2 and 3.5 hl / 100 kg is generally
the vessel to reduce oxygen pickup. used, though this can be higher. This applies to all
variations of decoction mash. The exact ratio is
determined by the wort extraction system and the amount
of pumping / mixing required. Thinner mashes use less
energy to mix and transfer than thick mashes, though the
more water added to the mash, the less can be used for
sparging, with subsequent risk of poorer extracts.

Triple decoction mash

The following is an example of a triple decoction mash, as
developed when accurate temperature control of heating
was not available. The temperature control is by means of
transfer of portions of mash into a mash cooker, followed
by transfer back to the mash vessel. Note how long this
process takes. Largely for this reason, triple decoction
mashing has been replaced by rising temperature infusion
mashes, where the heating, mixing and stands all take
place in a single vessel. See next paragraph for an example
temperature profile.

The basic design of a mash cooker is as above, though

without the facility to mash in, but with connections to
allow transfer from and back to the MCV. The design of a
cereal cooker is as above, but the transfer is to the MCV,
not directly to the lauter tun or mash filter.

Typical mashing parameters

Isothermal infusion mash

The following is an example of the temperature profile of a
simple infusion mash, as used in a mash tun. The
Rising temperature infusion mash
temperature rise as a result of sparging is shown.
Due mainly to the cost of equipment and the time taken to
carry out a traditional decoction mash, rising temperature
infusion mashes are the most commonly used method of
handling poorly modified malt. Note that this profile does
not allow for use of adjuncts such as rice or maize, which
require the use of a cereal cooker.

The following example shows the regime for

undermodified malt, which traditionally would have used a
decoction mash system. If using well modified malt, a
simpler process may be used, perhaps as simple as a single
o o
65 C stand, followed by heating to 77 C prior to transfer
to the lauter tun or mash filter.

Learning Material 2016 27

 2.4 Plant operation – wort separation

When conversion is complete, the mash will consist of a

sugar solution called wort and the husks and endosperm
residues of the malted barley. The purpose of wort
separation is to separate the sugars in the wort and malt
residues from the husks etc.

The husks and other particles contain tannin which is bitter

and will make the beer unstable after packaging. They also
contain fatty substances like lipids which will reduce head
stability and will also make the beer go stale.
Adjunct mash / double mash The objectives of effective wort separation are the removal
Adjuncts with higher gelatinisation temperatures than of unwanted material while at the same time extracting all
barley must be pre-cooked before addition to the main the available wort.
mash, and hence the double mash system. The maize or
rice grits are boiled up in the cereal cooker to gelatinise the Effective wort separation means:-
starch. Once gelatinised, the adjunct is added to the main • Maximising extract recovery.
malt mash. The two mashes are carried out concurrently in • Absence of particles in the wort.
separate vessels and combined to give a single temperature
• Absence of starch in the wort.
rise. Generally, other temperature rises if required are
made by heating the mash vessel, rather than transferring a
To achieve these objectives, wort separation systems use
portion back to the cooker. The following diagram shows
some common principles:-
an example of an adjunct mash requiring gelatinisation of
• Filtration using the husk as the filter bed
maize grits.
• The filter bed is supported by the slotted base of a
mash or lauter tun or a filter sheet in the case of a
mash filter.
• The wort flow is controlled to ensure wort clarity and
maximise filtration efficiency.
• The strong worts (containing the sugars dissolved
during mashing) are extracted first followed by
sparge water to wash out remaining extract.
• The grain bed is then sparged (washed) with hot
water to extract the maximum amount of soluble
extract as weaker worts.
• On completion of filtration, the spent grain (waste
husk and endosperm) must be removed and disposed
of.

Assessment of starch conversion Wort separation methods

At the end of the conversion stand(s), there should be no There are many systems in which wort can be separated
residual starch. This will result in loss of extract. In from the mash, the most common being:-
addition, any residual starch may be washed out during • The mash tun.
sparging, and carried through to the wort kettle. Here it • The lauter tun.
can be gelatinized, and then be carried through the brewing • The mash filter.
process to form hazes in the final product.
Other types of plant, for example the Strainmaster, may be
It is important to regularly check mashes for residual starch used but are less common and will not be discussed here.
immediately prior to raising the mash temperature, starting
transfer or run-off. The normal quick method is to use a The operation of different wort separation systems are
weak solution of iodine in potassium iodide. A small illustrated in the diagrams in the following sections.
quantity of the mash is put on a white tile or similar, and a
few drops of the solution added. Any residual starch shows Mash tun
up as blue black particles or possibly even as a blue/black The mash tun acts as conversion vessel and wort separation
colour of the liquid. vessel. Filtration gives very bright wort through a deep bed,
but it is slow and extract recovery is moderate.
It is normally too late to affect that particular mash, but
changes can be made to subsequent mashes, and the The wort is run-off through one or more discharge pipes,
affected mash monitored throughout the rest of the each pipe serving approximately the same area of the base.
process, and corrective action taken.
28 General Certificate in Brewing
The wort may be recycled on top of the mash until clear, to The different lauter tun suppliers all control their lauters
remove the fine solids below the mash, but this is differently in terms of run-off rates, sparge rates and raking
frequently not carried out due to the tendency to blind the depth and speed. The run-off control has also changed
bed. somewhat as lauter tun physical design has changed, and as
improvements have been made in automated control
The rate of run-off is typically controlled by a variable systems. However, there are a number of common
height “weir” system (valentine), or a single flow control operations as follows.
valve, or a series of valves at different heights.
For all malt brews, a mash rate of between 2.5 and 3.5 hl
Strong wort is run off slowly because it is more viscous than per 100 kg is generally used. The false floor loading is
2
weak wort and initially the mash bed must not settle onto expressed in terms of kg dry grist / m , and varies according
the plates. Once some of the strong worts have been run to the milling regime and the turnround time required. In
off, but before the mash has settled on the false floor and general terms, to achieve the same extract efficiency, the
started to compact, the sparge is started. The rate of higher the bed loading, the fewer brews can be processed,
sparge must match the rate of wort run-off so that the bed ranging from 6 up to 12 (for a modern lauter tun) brews per
does not rest on the false floor and compact excessively day. Bed loadings are lowest for dry milling which tends to
2
until the final drain down. The diagram below shows a produce most fine husk material (130 to 180 kg m ), slightly
2
typical run-off profile for flow rate and gravity. higher for conditioned milling (140 to 190 kg m ), and even
2
higher for wet milled malt (190 to 250 kg m ).
Once a fixed volume of sparge has been added, the tun is • At the start of the cycle, the lauter false floor is
allowed to drain down. Spent grain is removed through a flooded with hot water and the rakes moved to their
port in the base either manually or by using sweeper arms highest position.
similar to those used in many lauter tuns. • The converted mash is transferred from the MCV to
Mash tun the lauter tun. Modern vessels are filled from the
Sparge water base to avoid aeration and damage to the husk.
supply to rotating When the transfer from the MCV is almost complete,
sprinkler.
the recirculation of cloudy worts (vorlauf) can be
started. The rakes may be used to help spread the
mash evenly across the lauter floor, but are
subsequently raised to the highest position.
Slotted • The recirculation is to remove the cloudy wort from
plates Deep bed of mash Spent under the bed and some of the very fine material in
through
which the
which 'floats' above grain the bottom layers of the bed so the material is not
the plates. out.
wort is transferred into the wort kettle. It also transfers the
filtered. underlet to the top of the bed which can then be
used more effectively to extract the sugars from the
malt material.
Wort flow control. • Run-off starts normally without the rakes running or
being lowered into the bed.
• The rakes are then operated continuously with height
Example of wort gravity and flow rate during run off from and speed varied to maintain a constant differential
mash tun. pressure (DP) across the bed. Increases in intensity
(depth, speed) can cause the wort to go cloudy for a
significant period of time. The wort flow rate may
also be varied to achieve the fastest flow rate
possible whilst maintaining the DP.
• When some of the strong wort has been run-off, and
before the grain bed is exposed, sparging commences
at a rate to match the run-off rate. This may take the
form of continuous sparging, or batches at high flow
rate. The bed must never be allowed to dry out, to
prevent bed compaction and oxygen pickup.
• The volume of sparge water is fixed, and when the
required amount has been added, the bed is allowed
to drain down without restriction.
Lauter tun • The spent grains are then removed through a port in
The lauter tun is will give good wort quality and extract the base by discharge gear attached to the rakes (e.g.
recovery. However its effectiveness does depend on Huppman, Steinecker) or reversing the raking
balancing turn round time against wort quality and extract direction to form a sweeping action (Briggs).
recovery.
Learning Material 2016 29
The increased complexity of a lauter tun compared to an The diagram at the end of this section shows an example of
isothermal mash tun can be seen in the following simplified a lauter tun sparge and run-off profile, and demonstrates
drawing. how much more complex lauter tun operations are than
mash tuns.

This is for a lauter tun capable of a four hour turnaround

time, but forms the basis for up to 12 brews / day.

Mash filter
The mash filter is becoming more popular worldwide due to
the rapid turnaround times and high extracts achievable.
The mash filter’s numerous plates and frames, which
overall form a very large area of very thin beds rather than
a single smaller area of deep bed enable a very fast run-off
of wort and effective sparging.

In a mash filter, all the chambers need to be filled

completely and consistently. Consequently it has to
Example of rakes in lauter tun (Huppman) operate with a standardised size of mash.

The basic principle of operation of a mash membrane filter

is described here, with sparge in a single direction. Please
note that some filters alternate the direction of sparging
every alternate fill (e.g. Ziemann).

Some filters, (e.g. Meura 2001 and later) have membranes

built into the plates which allow the cake to be squeezed
and thus obtain a slightly higher yield and drier cake than
non-membrane presses, and allow variability in capacity of
from -20 % to +10% of the nominal throw. Two membranes
are fitted to alternate plates in the original 2001 filters.
More recent ones have a single membrane fitted to every
plate.

Modern filters have polypropylene plates as opposed to the

The position of the rakes is such that the track of one does cast iron or stainless steel of the classical filter making them
not overlap with another track, as shown here, the lighter and easier to handle.
individual rakes being indicated by the black arrows.
The filter is constructed of alternate frames to hold the
mash and plates to channel wort run-off and sparging, all
separated by filter cloths which either hang over the plates
or are hung from the individual plates, depending on the
design.

The general operating principles of a mash filter are

explained below:-

• The filter is first pre-heated and flushed with hot

water before the converted mash from the mashing
vessel is transferred into the mash frames. In the
early mash filters, this is through a top central
channel which by-passes the wort collection plates.
In later designs, this is from the bottom of the plates
initially, to reduce oxygen pickup.

• Wort is run off as the filter fills.

30 General Certificate in Brewing

• When the filter is virtually full, mash is transferred
• When sparging is complete, in membrane mash
into the filter via the top and bottom ports, and later
filters, the expandable membranes are then inflated
the top ports only. Wort drains from the mash into
in order to extract much of the remaining weak wort.
the collection chambers in the adjacent plate or
This also gives a much drier spent grain cake with a
frame and into the wort collection channels (top and
lower effluent loading. If no membranes are fitted,
bottom) to the collection buffer tank, and from there
the filter is simply allowed to drain down whilst
into boiling copper/kettle. The wort run-off rate and
emptying the buffer tank.
mash transfer rate are balanced to ensure consistent
solids loading throughout the chambers.

• In membrane mash filters, the frames are fitted with • To wash out all the wort from the mash, water is run
an expandable membrane which once the mash has into the plate on the other side of the layer of mash
been transferred, is inflated with compressed air to (using a separate sparge plate, or run-off port as
squeeze the grain bed, extracting much of the shown here), across the mash bed and then through
entrained wort, so improving the extract yield (not wort channel.
shown in this series of drawings).

Learning Material 2016 31

 Cycle times
The efficiency of the mash separation process is measured
by:-
• Turn round time, which is the time to process a
complete brew from the end of grain out for one
brew, to the end of grain out for the next brew.
Generally a modern brewhouse would process 8 to
10 brews every 24 hours with a lauter tun; 12 brews
per day with a modern mash filter, though 14 can
now be achieved.
• Extract efficiency, which is based on a direct
comparison of the total extract (gravity x volume)
collected in fermentation vessel against the
laboratory extract and weight of brewing materials
used. Generally a lauter brew house will recover 98%
of laboratory extract, but a modern mash filter can
achieve greater than 100% extract recovery.
• The spent grain is dropped from the filter at the end
of the cycle when the filter is opened. When considering a new brewhouse, or major
modifications to an existing system, it is necessary to
Summary of the principal differences between wort consider a number of factors before deciding on the most
separation systems appropriate solution, including the following, not listed in
any order of priority:-
Mash Tun Lauter Tun Mash Filter • Length of working week.
Milling 4 roll dry 6 roller dry or Hammer • Brewlength required (or current constraint where
system wet mill mill retro fitting).
Grist Coarse Medium/fine Very fine • Wort clarity required.
Mash • Extract achievable from each system.
1 vessel 2 vessels 2 vessels • Cleaning cycle times.
system
• Cleaning frequency.
Liquor to
• Cleaning material costs.
Grist ratio 2 to 2.5 2.5 to 3.5 3 • Engineering maintenance costs (including
(litre / kg) replacement parts / frequency / downtime).
Sparge • Operator maintenance costs (e.g. sheet changing,
volume 4.5 3.8 2.5 plate manual cleans).
(litre / kg) • Space available.
• Use for spent grains.
Total water
7 6.8 5.5 • Grain bill (cannot use sorghum for instance in a lauter
(litre / kg)
tun).
Filtration • Brewlength variability.
2
area (m / 2.5 4.5 3.5 • Utilities requirements (water, electricity).
tonne)
Bed depth Wort clarity
1000 400 50 Wort separation also aims to achieve consistent wort
(mm)
quality. This can be difficult to measure but typical
Bed loading
2 400 200 28 parameters would be:-
(kg / m ) • Wort haze - should be < 50 EBC 10 minutes after the
Run-off rate start of run off. This can be measured with an in-line
2
(litre / m / 1 0.6 20 hazemeter.
min) • Suspended solids - no more than 10 to 15 ml as
Typical sediment after 2 hours stand in an Imhoff cone.
extract High hazes in wort can lead to a number of problems either
97 98 101
recovery in the brewhouse, or in the process downstream, including
(%) • Run-off problems.
Brews / day 5 6 to 12 12+ • Excessive volumes of trub / high hazes.
• Flavour problems.
• Fermentation problems (e.g. due to smothered yeast
in extreme circumstances).

32 General Certificate in Brewing

 • Variable yeast flocculation. Notes:
• Poor filterability. Draw a diagram of the mashing system that you are
• Potential shortening of shelf life due to haze familiar with.
formation.
Why was that system chosen?
Brewhouse manufacturers have placed a lot of emphasis on
reducing mash and wort oxidation, and whilst it is generally Draw a diagram of a wort separation system in a brewery
accepted that undue oxidation is undesirable, it is has not that you are familiar with.
been established that the total elimination of oxygen is
beneficial. A small amount of mash oxidation is probably Why was that system chosen in your brewery?
inevitable and may even be desirable.
What extract yield is obtained from this system?
Spent grains
The waste husk after the wort has been removed is a If extract yield is below expectation, how could it be
valuable by-product because it can be utilised as animal improved?
food, typically for cattle. Where used as animal feed, it is
necessary to maintain hygienic conditions for the storage List the key operational and process parameters relevant to
and handling of the spent grains, and to ensure no the milling and mashing systems in the brewery that you
contamination by foreign materials such as oils. are familiar with.
Traceability is typically also required.
What quality parameters are monitored during milling,
In some breweries, the grain is used as biofuel. To be mashing and wort separation?
suitable for this it often has to be further dried using
relatively high pressure belt presses and dried further using
the hot exhaust gases from the furnaces.

Learning Material 2016 33

LAUTER TUN

MASH TUN

34 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 35

Section 3 Wort Boiling

3.1 The purposes of wort boiling

The terms “kettle” and “copper” are used interchangeably • To dissolve oils that contribute to hop aroma in the
throughout this document. Although the term “kettle” is final product, though these generally only remain if
used predominantly, if the user normally uses the term the hops are added late, and the oils are not given
“copper”, then this may be used instead in any answers. time to be boiled off.

• To denature and coagulate some of the protein

The description of the kettles / coppers has been restricted derived from the malt. Protein has the potential to
to “traditional” wort boiling systems, and methods such as make packaged beer go cloudy as it ages. Its removal
wort stripping and high temperature boiling will not be at this stage will help protect the beer’s stability.
discussed. The underlying principles of the boiling process
and desired end results remain the same. • To develop wort colour and flavour through the
action of heat on sugars and amino acids (the chemical
Introduction reaction between sugars and amino acids is known as
When the wort has been separated from the malt husk, it is the Maillard Reaction).
boiled. There are several reasons for doing this:-
• To increase the strength or concentration of the wort.
Wort concentration is a factor in ensuring that the
• To sterilise the wort. Brewing raw materials such as
chemical changes described above actually occur. It is
malt, hops and occasionally brewing water itself are
also important in the production of strong beers
infected by micro-organisms. These contaminants are
whose original gravity is higher than that of the wort
washed into or added to the wort and remain viable,
coming from the wort separation system. The amount
and therefore have to be killed during the brewing
of water removed during the boil is directly
process to prevent wort and beer spoilage.
proportional to the rate of evaporation (and hence the
•
o
To stabilise the wort. Above 50 – 80 C, enzyme amount of energy supplied). The efficiency is affected
structure is broken down and the enzymes lose their by the design of the wort kettle, particularly the
activity. Thus a small quantity of enzymes that heating surface area.
converted the starch into sugar and the protein into
• Wort pH continues to fall during wort boiling. The
amino acid may not be fully denatured by the final
drop in pH is mainly due to the reaction of calcium
higher temperature stages of mashing, and sparging.
compounds with phosphates and polypeptides. These
Some brewers add external enzymes, such as +
form insoluble compounds releasing H (hydrogen
thermostable beta-glucanase or alpha amylase,
ions) so reducing the pH. This is an extremely
intended to help with wort filtration or adjunct
important reaction as lowered pH :-
degradation (e.g. rice or maize). These enzymes are
• Improves protein coagulation.
more heat stable and are active throughout mashing
• Improves beer flavour stability in particular VDK
but will be de-activated during wort boiling. It is
(diacetyl) reduction.
important that all enzymes are destroyed by boiling,
• Encourages yeast growth.
otherwise they would continue working, which would
change the profile of the beer. • Inhibits the growth of many other contaminating
organisms.
• To evaporate away unpleasant aromas associated • Results in less colour formation.
with the wort. DMS, the sulphury character found in • Results in poorer hop utilisation.
lagers is generated on the malt kiln and during boiling.
This is volatile and is boiled off in the wort kettle. Other raw materials and process aids may be added to the
Aldehydes derived from the malt, substances that give wort:-
beer an unpleasant straw/grassy aroma are also
volatile and evaporated off. Evaporation rates as low • Sugar can be added here because it needs to be
as 2% of the initial wort volumes are sufficient to dissolved, thoroughly dispersed and sterilised.
produce good beers after a 60 minute boil.
• Kettle finings are additives which enhance the
• To dissolve the bittering resins from the hops and to coagulation of proteins during the boil to form ‘break’.
stabilise them. Hops or hop extracts are added These flocs help form the trub which settles out and
because the bitter resins (alpha acids) dissolve better can be easily removed from the wort. Kettle finings
in hot wort. These alpha acids need to be modified by are discussed in more detail in section 4, wort
‘isomerisation’ reactions which are heat induced to clarification.
stabilise the bitterness that is typical of beer flavour.

36 General Certificate in Brewing

Factors affecting wort boiling effectiveness • They can be added directly to the kettle making
additions for any of the above reasons comparatively
The principal factors which will affect the evaporation of easy.
volatiles include:-
Where crystal or block forms are used, special dissolving
• Duration of the boil. vessels may be required, whereas syrups can be dosed
• The temperature of wort. directly into kettle without further processing.
• The intensity of boil (the more steam vapour
bubbles formed per unit volume of wort the more Sugar additions may be derived from:-
intense the boil resulting in more evaporation). • Malt, in which case the carbohydrate and nitrogen
• The design of any spreader plate system and spread content is like to be similar to the brewhouse wort.
of wort from it, affecting the surface area for the • Other grains such as maize, wheat or barley, typically
volatiles to flash off. mixtures of glucose or other simple sugars.
• The circulation currents within the wort kettle. Poor • Sugar cane or beet.
circulation (and hence “dead spots”) is liable to lead
to poor evaporation of the volatiles.
• Condensation of volatiles in the vapour stack if 3.2 Wort boiling systems
allowed to run back into the boiling wort.
Operating principles of wort boiling systems
The kettle design will have a major influence. It has been
found that more late-hop character persists in poorly Kettles are designed to provide a vigorous or ‘rolling’ boil
agitated wort. and to be energy efficient. Wort boiling is the most energy
intensive part of the brewing process. The main task is to
Purposes of solid and liquid sugar addition provide sufficient energy input to ensure adequate
turbulence and evaporation. A number of different designs
There are a number of reasons why sugar adjuncts, in have been made to achieve this.
liquid, crystal or block form, may be used. They can affect
beer flavour by: Direct fired
Traditionally, wort was boiled in a direct fired kettle, often
• Diluting the flavour to give a lighter, smoother beer made of copper which has particularly good heat transfer
in the case of bland adjuncts. properties, hence the widely used term “copper”. Because
• Contributing their own distinctive character to the the heat source was localised at the bottom of the vessel, it
beer in the case of flavoursome adjuncts. restricts the volume of wort which can be boiled at any one
• Altering the carbohydrate and nitrogen ratio of the time with a maximum is around 330 hectolitres. Direct fired
wort, thus affecting fermentation products in the kettles are still being installed in the micro brewing
case of adjuncts low in nitrogen. industry, though many of them use heating coils near the
base of the kettle for improved heat transfer.
Dark coloured sugars and caramels can be used to add
colour and or distinctive flavours to a beer. Light coloured
sugars will dilute malt colours to produce lighter coloured
beers.

Sugar additions can be used to increase kettle gravity as

they normally have a very high extract value. There are a
number of possible benefits to the brewer:

• Better extract recovery than malt, because there is

no loss of extract due to the mashing and separation
stages.
• Producing high gravity beers such as barley wines
which would otherwise require extended boiling
times or non-recovery of weaker worts.
• Production of wort for high gravity brewing, with no
changes to the mashing or separation procedures,
thus increasing brewery capacity.
• Increased brewhouse output without investing in
additional mash vessel and or separation plant
• Lower lauter tun loadings and hence faster run off
for the same wort volume. The above drawing shows a traditional direct fired copper /
kettle – poor recirculation.

Learning Material 2016 37

 (a) Kettle with “horizontal” internal heating coils – poor
recirculation.
The above drawing shows a typical installation for a small
brewery, using a gas or oil burner, with heating via internal
heating coils – poor recirculation, but better than
traditional direct fired kettles.

The use of steam and internal heating systems enabled the

designers to provide a larger heating area, more consistent
heating temperature, and use of larger kettles. The heat
transfer is more efficient because it was surrounded by the
wort (this aspect is also utilised in more recent direct fired
kettles, as shown above).

There are two main types, those with the heating element
inside the vessel and those with it outside. Internally
heated kettles may use simple spiral looped internal
heating coils (see drawing (a) below).

In other kettles the heaters were upright and located in the (b) Kettle with vertical internal heating coils for improved
centre to give improved recirculation currents. Some kettles recirculation
also included base steam coils for preheating the incoming
wort, and to minimise dead spots (see drawing (b)). This
was developed further by the introduction of a “chimney”
and “spreader plate” giving greatly improved recirculation
and a greater surface area for evaporation (see drawing
(c)).

The disadvantage of kettles with internal heating tubes is

that the heaters tend to be difficult to clean with
conventional CIP due to blind spots and are prone to
corrosion. This can result in steam leaks into the boiling
wort which are difficult to detect and repair. Wort
circulation relies on thermal currents within the kettle and
the turbulence over the heating surfaces is limited. This
results in high levels of fouling, and will require more
frequent cleaning to ensure effective heat transfer is
maintained.

(c) Kettle with vertical internal heating elements, chimney

and spreader plate for vigorous recirculation

38 General Certificate in Brewing

 External calandria with indicative flows during wort boiling.
The low level of natural turbulence and high fouling is
improved by use of forced recirculation.

The use of a chimney and spreader plate forms the basis for
most modern systems, some of which use pumps to
improve the recirculation, at least whilst the wort is heating
up, and some without (diagram of example not shown as so
similar to (c), but without bottom “horizontal heating coils).

However, heating elements with the wort surrounding the

elements have now been superseded by use of shell and
tube heat exchangers. In these, the steam supply is
contained within the shell, whilst the wort passes through
the tubes. This design minimises the problem of the
heating surfaces become fouled quickly.

Some of the latest designs use an external heater (external

wort boiler). The wort is taken out of the kettle and passed
through a shell and tube or plate heat exchanger for
heating. The heat exchanger may be primed during the pre- Combined kettle/whirlpool with indicative flows during
boil stage, using a small circulation pump. In some wort boiling.
installations when boiling starts, the circulation pump is by-
passed. The wort then circulates using the natural Energy consumption
“thermosyphon” effect. Circulation starts because hot The wort boiling process consumes a large proportion of
liquid rises, cools down and therefore sinks again, etc. the heat energy used in the brewery and so boiling vessels
o
Incoming wort to the boiler is at 100 C and the outlet wort (kettles/coppers) are designed to be as energy efficient as
o
and superheated vapour from the boiler is around 105 C. possible. Features include:-
So the hotter liquid rises out of the boiler to the kettle. This
saves pumping energy and limits the potential for damage • Levels of evaporation reduced from traditional levels
to the "flocs" which would otherwise have to pass through circa 10% to as low as 4% (with energy recovery) or
a recirculating pump. 2% (without an energy recovery system).
• High levels of insulation.
The better heat transfer and turbulent conditions improve • Easy to clean and designed to avoid the build-up of
self-cleaning of the tubes. This allows between 8 and 16 soil, particularly the heating surfaces.
brews (more in most recent designs) to be processed • Heat recovery from the vapour evaporated from the
before a clean. wort to generate hot water for brewery use.
• Heat recovery from the vapour evaporated from the
By reintroducing the wort at a tangent, it is possible to use wort to preheat wort from the lauter tun or mash
the vessel as a combined kettle/whirlpool. This eliminates filter. Below 4% evaporation energy recovery is not
the transfer time between a separate kettle and whirlpool. economically viable using current technology.

Learning Material 2016 39

Typical boiling times and hop addition practices The hop develops very bitter resins and oils around the
seeds of the cone which is the fruit of the plant. These are
Boil times seen as the yellow powder obtained when a sample of
Boil times using the equipment discussed are typically 60 to whole hop cones are broken open, or rubbed between the
90 minutes. Traditionally, boil times were often palms of the hands.
considerably longer, but with improvements in wort runoff Resin (alpha acid)
control, particularly with modern lauter tuns and mash
filters, long boil times are not normally required specifically
for evaporation. Due to the high energy costs, any Cone
reduction has a beneficial effect on reduction of energy leaf
usage & costs. With improvements in malting and boiling
technology, it has also proven less important to boil for long
periods to achieve DMS production and evaporation. Seeds
Cone
It has been demonstrated that extended boil times do not
offer improvement to hop isomerization and thus utilization
(see section 3.4). These resins are dissolved when hops are added to the
process and remain as a strong flavour component of the
Modern wort boiling systems typically aim for about 4% finished beer.
evaporation, with boil times of 60 minutes or slightly less.

Hop additions The main resin, whose technical name is α-acid (alpha acid),
Bitterness hops are generally added at the start of the boil, is modified during the boiling process when it is changed to
though where beer is to be packaged in clear (flint) glass, isomerised-α-acid, which is both more bitter and more
stabilized extracts only may be used to give bitterness, and soluble than the original α acid. The isomerised form is
no hops will be added at all during the boil. more stable and it survives in the finished beer to give the
beer its bitter flavour. It can be measured as milligrams per
When brewing with whole hops or pelletized whole hops litre (mg/l) of iso-humulone, expressed as an International
(i.e. not hop extracts), the principal hop volatiles lost during Bitterness Unit (IBU), internationally recognised as a
wort boiling are the hop oils. If these are present at too measure of the beer’s bitterness.
high a concentration they may contribute a bitter,
vegetable, grassy flavour to the beer. Most of the hop oil Hop oils are the aromatic fraction of the resins and give
volatiles are lost during the first 20 minutes of a boil. beer its hoppy ‘nose’ and character. They are, however very
volatile and will be distilled off along with the other
Where late hop character is required in beer, quantities of volatiles in the kettle unless added late in the boil. Beers
selected aroma hops can be added to the kettle shortly with a strong hop aroma are likely to have been late
before or at the end of the boil. The quantities of hops hopped, dry hopped (that is hops added to the FV shortly
added and the timing vary from brewer to brewer after completion of fermentation, or into cask beer) or have
depending on the desired flavour and aroma characteristics had hop oil added at an appropriate stage in beer
desired. For example, a lager may have:- processing.

• A first addition of bittering hops made at the start of Hops are generally classified as belonging to one of two
the boil. main usage groups:-
• A second bittering and flavour addition about • Bittering hops.
halfway through the boil. • Aroma (flavour) hops.
• A final addition 5 minutes before the end of the boil
to impart later hop aroma / flavour. However more recent agronomic developments have
developed a number of hop varieties which are considered
suitable for either or both uses.
3.3 The nature of hop bitterness
Bittering hops have been bred specifically for high alpha
The nature & origins of hops and hop products
acid content. These can then be used for preparing
Hops are essential to the brewing process in that they extracts, when any undesirable aromas are lost, or may be
impart both flavour and bitterness to the beer. Up to the added at the start of the boil, when any undesirable aroma
years 1400/1500, 'ale' was brewed in England without hops, characteristics are boiled off.
but often with other herbs as the flavouring ingredient.
Hopping of beers grew in popularity, not only because of Aroma hops have been bred primarily for the desirable hop
the flavour but also because of the plant's antiseptic oil content, though the nature of modern breeding
properties. Their use is now almost universal. techniques and agronomic practices mean that these often
also have quite high alpha acid contents.

40 General Certificate in Brewing

Isomerization during wort boiling • Pellets from milled and compressed hops after
Isomerisation is a relatively rapid reaction with production removal of vegetable matter (e.g. hop cone leaves,
of over 90% of the wort bitterness occurring within the first seeds), concentrating the resins to standard alpha
30 minutes of boil. Complete extractable bitterness occurs acid values, e.g. type 45 and type 90 pellets.
within 60 to 70 minutes. • Pellets from milled and compressed hops following
stabilisation of the hop resins to make them less
The isomerisation reaction is faster at higher temperature. susceptible to oxidation damage.
Results from high temperature wort boiling show that the • Extracts of the resins, typically extracted using liquid
rate of isomerisation of alpha acid is directly related to CO2, concentrated to standard alpha acid values, e.g.
temperature. 30 %.

Alternative or supplementary hop additions Isomerized hop products

Isomerised hop products are made by processing hops or
Hop products hop extract in a specialised plant so that the isomerisation
Hops may be obtained from the supplying merchants in a that normally takes place in the wort kettle during boiling is
number of forms:- carried out before the hops are added.

• Whole hop cones, normally compressed into bales or The advantages of using pre-isomerised pellets are the
pockets. same as those for the use of non-isomerised pellets but
• Whole hop pellets. with added savings from better hop utilisation. Pre-
• Isomerised hop pellets. isomerised hop extracts allow the beer to be hopped at the
• Non-isomerised kettle extract. end of the process avoiding the losses that occur during
• Isomerised kettle extract. brewing.
• Hop oils.
• Post fermentation bittering extracts. Products include:-

Whole hops • Isomerised hop pellets.

Traditional brewing practice uses whole hop cones, which, • Isomerised kettle extracts.
after picking, have been dried and then compressed into • Isomerised hop extracts for use as post fermentation
bales or pockets for transport. However, there are a bittering addition.
number of problems associated with using this form of • Reduced (stabilised) hop extracts for use as post-
hops. fermentation bittering addition, for example in beers
to be packaged in clear (flint) glass bottles.
• The density is low, the bulk high, and transport costs
are therefore high. Hop oils
• Handling in the brewery is difficult, and they cannot Hop oil products are used to impart hop aroma to beers.
easily be used with external calandria and whirlpools The bittering components are not an essential part of these
for example. products. These include:-
• The entrained air degrades the hop resins rapidly. It • Hop oil emulsions
is not practical to vacuum pack whole hops. They • Pure hop oils
have to be refrigerated for storage, which adds
costs. Miscellaneous hop products
There are also some hop products which are not used for
Whole hops tend to lose their brewing value during storage, bittering beer or adding aroma but used instead to reduce
even when dried and kept in cold storage, but extracting over-foaming in the wort kettle or FV. They are most
the brewing value, either as α-acid or hop oil overcomes widely used when brewing beers for package in clear (flint)
this problem. glass, when foam generation during wort boiling and
fermentation is not suppressed by the presence of hops.
Non-isomerised hop products
Non isomerised hop products retain the α-acids unchanged Hop pellets - preparation
after processing, and have to be added at the start of boil. Hop pellets are made by removing the bulk of the
They include extraneous matter such as stalks and leaves, grinding the
hop cones and then pelletizing. The pellets are then
• Pellets from milled and compressed whole hops. vacuum packed, or packed in an inert gas to help preserve
the brewing value. Hop pellets contain the essential
material from the original hops including the aromatic oils
and their use is widespread. The advantages that hop
pellets have over whole hops are:-

Learning Material 2016 41

 • The pellets have a known α-acid content so control Bitterness potential of hops
of bitterness is more accurate. Both α and β isomerised acids contribute to the perceived
• Storage is easier and cheaper because the packs are bitterness of beer as noted above, and in fresh hops, the
smaller than pockets or bales of whole hops. potential is based on the α-acid content of the hops only, as
• All the brewing value of the hops (α-acid and hop expressed in mg α-acid / unit weight – normally as a
oil) is present after the pelletisation process. percentage.
• The hops deteriorate much more slowly during
storage. Calculations of hop addition rates
• Processing to produce pellets is cheaper than When preparing a recipe for a new beer, it is necessary to
extracting. consider a number of factors:-

• Target bitterness.
Hop extract - preparation
• The type and intensity of hop aroma in the final to
Hop extracts are made by dissolving the α-acid in either
be derived from late addition kettle or whirlpool
ethanol or more commonly, liquid carbon dioxide.
hops. Although the brewer is primarily interested in
Bitterness hop extracts may not contain much of the
the aroma obtained from these hops, because they
aromatic hop oil. However when added to the wort kettle
always contain some α-acid, the α-acids contained in
they the following advantages over whole hops:-
these hops must be accounted for, particularly
• The extract has a known α-acid content so bitterness where large amounts of aroma hops are used to
control is more accurate. obtain an intense hop character.
• Storage is easier because the extract occupies a • The length of boil after each addition.
much smaller space than the large bags (pockets) of • The length of time after the boil is completed that
whole hops. the hops remain in contact with hot wort.
• The hop extract does not deteriorate as it gets older. • The likely utilisation of each addition.

A disadvantage is that there is no filter bed formed by the As an example, we wish to brew 500 hl beer with a final
spent hops if a hop back is used during wort production. bitterness of 35 IBU, using a single addition of bittering
hops with an α-acid content of 8%.
Pre-isomerised hop extracts
Pre-isomerised hop extracts are prepared from hop extracts 500 hl of beer is 500 x 100 = 50,000 litres.
and may be used to adjust low beer bitterness after
fermentation. Weight of alpha acid required in the final beer = 50,000
litres x 35 mg per litre = 1,750,000 mg.
Ultraviolet light normally penetrates clear or green bottles
but not those made from brown glass. If beer is to be
The hops contain 8 % α-acid, i.e. 1 kg hops contains
packaged in clear glass, it is preferable to use only post-
80,000 mg α-acid
fermentation bittering as pre-isomerised extract in a
‘reduced’ form (for example tetra-hydro iso-α-acid, or
Therefore, assuming 100 % of the α-acid is converted to
‘tetra’), because it is not affected by ultraviolet light. No
iso-α-acid, we require
“normal” hops or non-reduced hops must be allowed to
come into contact with the beer in this case – sunlight
1,750,000 / 80,000 kg hops = 21.9 kg hops.
reacts with the iso-α-acid to produce compounds with a
‘skunky’ or “light-struck” flavour. An added benefit of beers
However, because only approximately 30 % is expected
treated with ‘tetra’ is that they also exhibit enhanced foam
to be isomerised and pass through to the final beer
stability.
(30% Utilisation), we need 21.9 x 100 /30 = 72.9 kg of
Hop oils are made by distilling off the aromatics from hops. hops to achieve our target bitterness.
They are added to fully processed beer to impart a ‘hoppy’
character. Note:-

1,000 mg = 1 g
3.4 Hop calculations 1,000g = 1 kg
1 kg = 1,000,000 mg
How bitterness is expressed
As discussed earlier, beer bitterness is expressed in the
arbitrary unit IBU (International Bitterness Unit). One IBU is
usually assumed to be equivalent to 1mg of iso-α-acid in 1
litre of water or beer in the range 15 to 35 IBU, although
the isomerised α-acid actually only contributes about 0.7
units per mg/L with the balance being other bittering
compounds including β-acids.

42 General Certificate in Brewing

Calculation of hop utilization Hop Type Typical Utilisation
Whole hops 25 – 30%
Hop utilisation is a measure of the efficiency of hop use. Pelletised hops 25 – 30%
The calculation is made by comparing the amount of α-acid Isomerised pellets 50 – 60%
added to the beer in mg/L to the level of measured Isomerised kettle extract 50 – 60%
bitterness in the final product in IBU (mg/L of Isomerised post-fermentation
isohumulone). extract 70 – 85%
Hop utilisation in the brewery is affected by a number of
factors, including:- In the following example, α-acid is added from hops which
contain 8% α-acid. Only a proportion of the added α-acid
• The timing of the hop addition. Additions at the ends up in the beer as iso-α-acid.
start of the boil will have much higher hop
utilizations than those added later in the boil, getting
500 hl of wort is boiled with 35 kg of hops with an α-
progressively less the later the addition, and thus the
acid content of 8 %.
less the contact time.

• The pH of the wort or beer. Isomerisation and The available α-acid is = 35 kg x 8% = 2.8 kg =
solubility are greater at higher (more alkaline) pH 2,800,000 mg
values.
The laboratory analysed the beer, finding it has a
• The vigour of the boil and the type of boiling system. bitterness value of 15 IBU.
• The amount of bitterness absorbed by the trub. The
higher the protein & carbohydrate trub volume, the 500 hl beer at 15 IBU means that the beer contains
lower the utilization.
500 x 100 = 50,000 litres
• Particularly for late hop additions, the length of time
the boiled wort stays in contact with the hops in the 50,000 litres at 15 mg/l = 750,000 mg iso α-acid
hop separation system (e.g. whirlpool).
Therefore the hop utilisation =
• The amount of bitterness absorbed by the yeast.
Different yeasts adsorb different levels of bitterness, (750,000 / 2,800,000) x100 %
though these variations are quite minor compared to
the variation due to time of addition. More yeast = 26.8 % Utilisation
(from yeast growth) will absorb more bitterness.
Knowing the likely hop utilisation value from your boiling
Again, as an example, if hops are added :- system it is possible to make a good calculation of a hop
addition rate (above).
• At the start of a 60 minute boil might typically give
30% utilisation.
• 45 minutes before the end of the boil might give Notes
29% utilisation. • Draw a diagram of the copper / kettle in a
• 30 minutes before the end of the boil might give brewhouse that you are familiar with.
27% utilisation. • What type of heater does it have?
• 15 minutes before the end of the boil might give • What raw materials are added to the kettle in the
15% utilisation. brewhouse that you are familiar with?
• 5 minutes before the end of the boil might give 8% • What effect do they have on the wort and beer
utilisation. produced?
• What process aids are added to the wort in your
The higher the concentration of α-acid in the hops added, brewery? At what stage are they added and why?
the poorer the hop utilisation. • What effect do these process aids have on the worts
and beers produced?
The higher the strength, or SG, of the wort, the poorer the • What types of hops or hop products are used in the
hop utilisation. brewery that you are familiar with?
• At what stage of the boiling process are they added?
Different types of hop products will give different • What level of hop utilisation is achieved in the
utilisations, with pre-isomerised hops having the better brewery that you are familiar with?
utilisation values.

Learning Material 2016 43

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

44 General Certificate in Brewing

Section 4 Wort clarification, cooling and oxygenation (aeration)
4.1 Wort clarification

Introduction
At the end of the boil, the wort will be bright but there will by taking a sample of hot wort (hot break sample) and
be large particles floating in it. These particles or flocs allowing it to cool below 80ºC. The flocs can be seen
contain:- forming and settling out.

• Coagulated protein or ‘break’. The more vigorous the boil, the better the coagulation.
• Tannin material from the malt husk and from the hops. Because the protein is no longer dissolved it can be
• Lipids or fatty material, mainly from the malt. removed fairly easily by physical methods.
• Spent hops or debris from hop pellets.
Many brewers simply rely on the use of wort separation
These can all have a deleterious effect on finished beer procedures such as whirlpools to remove the haze forming
quality, and as much as possible must be removed prior to proteins. However, where permitted, many brewers add
transfer to the Fermentation Vessel (FV). kettle finings to improve the formation of cold break.

The quantity of hot break formed (not including hop Kettle finings are made from seaweeds (often known, not
vegetable matter) is around 0.2 - 0.4 % of the hot wort. The always correctly as “Irish moss”), the active fining
difference of the density of hot break and hot wort is very ingredient being known as carrageenan. The use of this
low. material also improves the effectiveness of isinglass finings,
Cold break is formed at temperatures lower than 70 - 80 °C. where used post fermentation, and helps reduce the
The composition of cold break is around 52 % proteins, 21 amount of protein material to be removed during beer
% carbohydrates and 25 % polyphenols. At lower filtration.
temperatures there is more cold break formation.
The principal fining action is the result of direct electrostatic
Effect of ‘break’ on wort quality interaction of negatively charged carrageenan molecules
with positively charged protein flocs, making them bigger
• The coagulated protein, forming the bulk of the hot and so they settle faster.
cold “break” will, if allowed to remain, cause haze and
may also result flavour problems in the finished beer. The use of pellets of refined seaweed, rather than powder
• The tannin materials are very astringent and if allowed eases handling of the product and dispersion in boiling
to remain in large quantities can pass this character on worts. Kettle finings of this type contain approximately
to the beer. Tannins also combine with proteins, causing 50% of their weight as a dispersant, usually as sodium
haze and, in sufficient quantities, sediments. bicarbonate and a suitable acid, (e.g. citric acid), to make
• Lipids or fatty material will destroy the head stability of them self-effervescent.
the beer. It also makes the beer taste stale (often
described as papery or cardboard) as it gets older. New materials are semi refined seaweeds of the genus
• Spent hops or hop pellet debris, which can simply Eucheuma. The seaweed is simply harvested and washed in
smother yeast and prevent it fermenting as well, but if alkali to slightly purify and clean it without major
not separated, can make it difficult to achieve the refinement and turned into dust free granules, so reducing
optimal pitching rate. Large quantities can also the cost of refinement and pelletisation.
adversely affect the flavour of the beer and the haze
stability by allowing additional flavour and haze forming The clarity of the wort produced is affected by a number of
materials to dissolve during fermentation. factors including:-

Kettle finings • Finings addition rate.

• Time of addition.
Malt contains some protein material. Most of this protein • Wort pH.
material is not wanted as it can cause haze in the final • Malt variety and degree of modification.
product. It is considered desirable to remove as much • Wort gravity.
protein as possible at each stage of the brewing process.
During boiling, much of the larger protein molecules clump Although added to hot wort, kettle finings have no
together, or coagulate in the same way that the white of an significant effect on hot wort clarity, their main effect being
egg curdles when it is heated. This coagulation can be seen

Learning Material 2016 45

the production of bright cold wort. The sole reason for
adding kettle finings to hot wort (normally the kettle shortly
before casting) is to solubilize the carrageenan which does
o
not dissolve below 60 C. The kettle finings must therefore be
added early enough to be fully dissolved, although
sufficiently late to avoid thermal denaturation. The actual
time and rate of addition will depend upon the type of
product chosen and the process conditions. The rate in
particular should be optimised on a regular basis.

Break & hops removal

It is necessary to remove this ‘break’ to protect the beer’s

quality. There are four main ways of doing this depending on
the type of hops used and the requirement for absolute wort
clarity:- Start of wort transfer to a coolship.

• Filtration through the spent hops typically using a hop

back. Wort kettle hold back
• Separation of whole hops using a hop separator. The hot break may be sedimented in the wort kettle
• Sedimentation in a whirlpool. (copper). If a thimble or strainer is installed in the casting
• Centrifugation. outlet, when wort boiling is stopped, the hot break can be
• Filtration using kieselguhr or other filter aid, though this allowed to settle down. After that, the wort can be pumped
method will not be discussed further as it is so rarely to the wort cooler system.
used.
• The break and spent hops collected from any of these Hop Back
processes are waste material that has to be disposed of. Hop backs are used by traditional brewers who still use
whole hops. Hot wort is transferred to the hop back either
Wort clarification onto a bed of fresh whole hops used for late addition of
hop aroma, or simply to the hop back. The wort is then
Cool ship recirculated so that a hop bed is formed from kettle hop
For many years the cool ship was the principal means of additions. The protein solids are retained in the hop bed
cooling wort. It provides almost complete removal of hot and the clear wort runs off for cooling. When drained, the
break and partial removal of cold break. It is a flat open hop bed is usually sparged with fresh hot water to recover
vessel and the wort is pumped into it directly after boiling any residual extract.
with a temperature of nearly 100 °C. The height of the wort is
only around 15 cm so there is a large surface area, the wort
cools down very quickly and the break particles have a short
distance to fall.

The main disadvantage is the microbiological risk. The wort is

without any yeast in an open vessel for some hours. There
may be fans to circulate the air over it. It is possible to install
sterile filters, but the risk of contamination is much higher
than in closed vessels. Another disadvantage is the size of a
cool ship because most other systems need less space.

Sedimentation tank
The traditional sedimentation tank is a simple open or closed
vessel where the wort is pumped in after boiling, to a depth
of around 1 – 1.5 metres. After a rest of at least one hour the
hot break and the spent hops settle down and the wort can
then be pumped to the cooler. There is little cooling in the
tank itself, so the disadvantages of long stand times at high
temperatures occur.

46 General Certificate in Brewing

Hop separator (or strainer)
Whole hops can also be removed using a hop strainer. The
wort containing the kettle hops is transferred to the strainer.
The hops are conveyed by a screw conveyor to a waste tank,
whilst the wort drains into a wort receiver. The strainer is
often used in combination with a whirlpool tank.

In some breweries, the functions of the wort kettle and the

whirlpool are combined into a single tank system. On
Whirlpool completion of boiling, the wort is recirculated through a
The whirlpool is probably the most widely used process for pump to create a whirlpool, and thus settling effect in the
hot break separation. Whirlpools are used with hop pellets kettle.
and extracts and not whole hop cones. It is a cylindrical vessel
with a flat bottom into which wort, while still hot, is pumped Centrifugation
through an inlet, laterally and tangentially. The inlet pipe is A disc or decanter centrifuge can be used to remove hops
tapered so that the velocity of the wort increases. This and break from hot wort. The centrifuge is also often used
configuration puts the wort in the whirlpool into rotation. to recover the wort from settled break in the whirlpool to
The rotational movement causes the so-called “teacup be added back into the brew.
effect”, i.e. the same effect that can be observed when one
stirs a cup of tea that still contains residues of tea leaves. The Please see section 7, yeast handling for a brief description
tea residues collect in the middle of the cup. The same of the flow through a centrifuge.
phenomenon is observed in the whirlpool. After some time, a
break cone forms in the middle of the whirlpool. After the
whole wort has been pumped into the whirlpool, a whirlpool
rest takes place, usually taking 10 to 15 minutes, depending
on the whirlpool design. The whirlpool rest should not be
prolonged too much as the stability of the break cone might
suffer. Disintegration of the break cone might be promoted.
When the rotational movement has died down, the clarified
wort can be removed from the whirlpool and sent to wort
cooling. Whirlpools are used with hop pellets and extracts,
but not with whole hops.
Typical decanter centrifuge operation
The difference between the inflow velocity of the wort and
the peripheral velocity should not be too high. Traditionally,
velocities of 12 - 15 m/s, sometimes 20 m/s were used.
Nowadays, the inflow velocity is not generally higher than 5 4.2 Wort cooling
m/s. Some breweries work with only 2.5 m/s. The
disadvantages of high values are high turbulence and high Purpose of wort cooling
shear forces which adversely affect particle coagulation and The wort ex clarification system, e.g. whirlpool is typically
settlement. at a temperature circa 97 °C, which is too hot to support
brewery yeasts. The optimum temperature for the start of
Different bottoms have been used to try to improve the fermentation, depending on the yeast strain, will be
compaction of the cone and thus losses of entrained wort, between 6°C and 20°C. The clarified wort must therefore
but the most common nowadays is flat bottomed with a be cooled to the fermentation temperature before the
gentle slope towards the floor outlet. yeast can be added.

A number of outlets at different levels are normally used to It would be uneconomic to use glycol or similar refrigerant
runoff the wort, starting at the highest, to reduce the amount on its own to cool the wort. The wort contains
of tub carried over into the FV.

Learning Material 2016 47

considerable excess thermal energy, much of which can be
recovered to produce hot water, usable for a number of
purposes including:-

• Mashing and sparging

• Cleaning
• Preheat wort from the mash separation plant to close to
boiling point, so less heat energy is required to boil the
wort.
As part of the wort cooling process, the wort is invariably
oxygenated, either by addition of pure sterile oxygen, pure
sterile air, or sometimes a mixture of both. This is
discussed in more detail later in this section.
Normally, the flow is diagonally across the plates, as
Effects of cooling on wort constituents follows:-
On cooling, wort proteins interact with polyphenols to
precipitate as cold break. This material consists of very fine Hot wort in
particles that are slow to settle and consequently are likely
to survive into maturing beer. In combination, boiling and
wort cooling remove 17 - 35% of the total protein content, Hot water out
depending upon the malt variety and hop product/variety
used. Cold break formation is temperature dependent,
o
only forming in significant quantities below 20-30 C, and Cold
increasing dramatically in quantity as the temperature is water in
further decreased. The removal of cold break can be
enhanced by use of kettle finings.
Cold wort out
Wort cooling methods
The traditional form of wort cooler was the coolship
followed by a trickling cooler. Cold water passed through
horizontal pipes and wort was fed over the pipes from the
top. The wort was cooled by the cold water and, in
addition, more water evaporated from the wort film after
the coolship, again contributing to cooling. An open
collection tank was placed at the bottom end of the series
of pipes, allowing the wort to be runoff to FV and pitching.
• In general 100 hl of hot wort at around 98 C will be
The large surface area allowed considerable wort
cooled to say 16 C by around 110 hl of incoming brewing
oxygenation, but this system is prone to contamination
water at 10 C which in turn will be heated to around
pickup.
85°C.
Nowadays the plate heat exchanger is almost exclusively • This makes wort cooling a very efficient process
used for wort cooling. This is because:- recovering most of the excess heat from wort boiling
which can be used for brewing.
• Plate heat exchangers are very efficient and can cool the
wort down in a short time. There is a large plate surface • In ale breweries with relatively high pitching
area for wort/coolant and the thin films of water / wort, temperatures above 15°C, cold well or town's supply
and high levels of turbulence mean the heat transfer is water may be used as the coolant. The hot water
very rapid. generated is then used for brewing and cleaning.
• Nearly all the excess heat from the wort can be • For lager brewing, with lower pitching temperatures of
recovered to generate hot water for brewing and other typically 8 - 12°C, an additional cooling stage is usually
production uses. added. The coolant in this stage is a refrigerant such as
brine, ethanol solution, glycol etc. Some breweries chill
• They are enclosed and are easy to clean in line.
the cooling liquor, so that only a single cold water stage
Therefore they maintain heat transfer efficiency and
is required.
keep the wort sterile.
• The plates of the heat exchanger are as thin stainless
Operating principles of plate heat exchanger wort coolers steel as possible (0.5 mm) to maximise heat transfer.
The principles of how the plate heat exchanger works are Surface area and turbulence are increased by embossing
illustrated in the diagrams below. The hot wort is cooled in or rippling the plates.
a counter current direction against the brewing liquor.

48 General Certificate in Brewing

4.3 Wort oxygenation / aeration System Advantages Disadvantages
Hot wort Air is sterilised by the Wort colour increase.
aeration / hot wort.
Purpose of wort oxygenation Flavour change.
oxygenation
(in-line) Air is dissolved
The absence of sufficient oxygen in the wort for the yeast effectively as it passes
through the cooler.
to make these sterols and fatty acids can lead to number of
problems including:- Cold wort Virtually no effect on Need to provide sterile
aeration wort quality. air / oxygen and injection
• Sluggish fermentations - high final pH and other flavour (in-line) system.
changes. Need to increase
solubility by injecting
• Early finish to fermentations resulting in high final small bubbles or ensuring
gravities. vigorous mixing and
injecting when wort
pressure is high.
• Poor yeast growth – insufficient for repitching.
Pumped Can be used to Prone to pick up
• Unhealthy yeast (normally seen as low viability) which is rousing via disperse flocculent contamination from
not suitable for repitching. “fishtail” over yeasts. atmosphere.
top of
fermenting Can be used to add FVs have to be built with
• Possible ability of contaminating bacteria to grow faster additional oxygen this facility to allow
wort
than the yeast and spoil the beer. from the atmosphere effective cleaning etc.
if the fermentation
starts to slow. Cannot be used on
Different yeasts and/or differing wort gravity require enclosed vessels,
different amounts of oxygen. Wort oxygen levels of particularly conicals.
between 8ppm (air saturated wort) and 30 ppm (oxygen
No accurate control over
saturated wort) may be required depending on the wort amount of oxygen
gravity and yeast type used. dissolved.

Pumped Can be used to Gas used must be sterile,

Wort oxygenation methods rousing with air disperse flocculent otherwise liable to pick
/ oxygen yeasts. up contamination.
The wort cooling stage has proven to be the best time for injection
Can be used to add FVs have to be built with
controlling dissolving oxygen. This can be achieved through additional oxygen this facility to allow
the use of air or from pure oxygen to a repeatable and from the atmosphere effective cleaning etc.
measurable level. if the fermentation
starts to slow. Difficult to clean.

It is usual to inject air or oxygen into the wort stream in- Can be used on Poor / difficult to control
line. The amount of dissolved oxygen in the wort affects enclosed vessels, amount of oxygen
yeast growth so much that some form of control is required including conicals. dissolved.
to guarantee consistency. The control can be achieved in a In deep vessels,
number of ways as discussed later. rousing part way
through fermentation
may result in excessive
The accuracy and repeatability of the control can be CO2 breakout and
measured by using a dissolved oxygen meter. However, “boiling over”.
particularly in older breweries, wort may be aerated only
Bubbled Can be used to Gas used must be sterile,
once the wort is in the FV, where accuracy of addition (and aeration / disperse flocculent otherwise liable to pickup
measurement) is much less well controlled. oxygenation yeasts (though this is contamination.
not main purpose)
FVs have to be built with
Aeration can take place before or after cooling on wort Can be used to add this facility to allow
transfer, or whilst the pitched wort is in the FV. The main additional oxygen effective cleaning etc.
advantages and disadvantages of each choice are listed in from the atmosphere
if the fermentation Difficult to clean.
the following table:-
starts to slow.
Poor / difficult to control
Can be used on amount of oxygen
enclosed vessels, dissolved.
including conicals.

In deep vessels,
rousing part way
through fermentation
may result in excessive
CO2 breakout and
“boiling over”.

Learning Material 2016 49

Aeration versus oxygenation Example maximum dissolved oxygen levels in water and
40° SG wort whilst air in contact with water at atmospheric
Use of aeration or oxygenation is generally dictated by the pressure.
level of dissolved oxygen required in the unpitched wort.
Temperature Max DO2 in water Max DO2 in wort
It is not possible to dissolve more than about 10 ppm oxygen
in cold wort when using air as the gas supply in a simple O
10 C 11.3 ppm 9.8 ppm
aeration system. However, it is possible to dissolve up to
approximately 30 ppm oxygen in cold wort if using pure
oxygen. Both these values are affected slightly by the cold O
wort temperature and wort gravity. The higher the wort 15 C 10.1 ppm 8.8 ppm
specific gravity, the less oxygen will be dissolved. The higher
the cold wort temperature, the less oxygen will be dissolved. O
20 C 9.1 ppm 7.9 ppm
Typically, sales gravity beers need no more than air
saturation i.e. about 9 ppm dissolved oxygen. High gravity
beers may need oxygenation, up to 30 ppm. Very high In theory, it should be possible to achieve the following
gravity beers (e.g. SG of 80° +) may require additional dissolved oxygen levels if using pure oxygen instead of air,
oxygenation / aeration during fermentation to allow the though brewers do not normally require these levels in a
wort to be fermented successfully. single dose. However, a number of breweries use DO2
levels around the 30 ppm in cold wort.
Different yeasts need different levels of oxygen for adequate
yeast growth. Since yeast growth has a direct effect on the
Temperature Max DO2 in water Max DO2 in
level of higher alcohols and esters produced during
wort
fermentation, different beers will need different levels of
dissolved oxygen to provide the correct (desired) amount of O
10 C 53.8 ppm 46.7 ppm
esters and alcohols. Some brewers use additional
oxygenation / rousing during early fermentation to suppress
the production of excessive levels of esters. O
15 C 48.1 ppm 41.7 ppm
In practice, levels of dissolved oxygen are finely tuned by
each brewery for each quality to give fermentations that
O
ferment on profile, give an acceptable flavour match and 20 C 43.3 ppm 37.6 ppm
minimise excessive yeast growth and losses.

Air injection - advantages Air injection - disadvantages Operating principles of wort oxygenation systems
Compressed air is inexpensive. Air must be sterilised.
The following discussion only relates to in-line wort
It will saturate to approximately The large volume of N2 oxygenation / aeration.
the level required by many yeasts, introduced with the air is very
although dissolved oxygen should difficult to fully dissolve and will
still be measured to ensure pass through the fermenter, Factors that promote gas absorption include:-
consistent fermentations. causing thick top foams.
• Low temperature.
Aromatic flavour compounds can
be sparged from the wort by • High pressure (e.g. by use of a back pressure control
these bubbles. valve).

• Small gas bubbles at point of injection, to give very high

O2 injection - advantages O2 injection - disadvantages surface area by using, for example, a venturi system or
a sintered stainless steel candle.
Cylinder oxygen is free from Extremely high levels of dissolved
microbes. oxygen are possible unless a
feedback control system from a
• High levels of turbulence, which can be achieved by
Only the quantity of oxygen dissolved oxygen analyser is high flow rates, in-line mixers or plate heat exchangers.
required for the fermentation used.
needs to be injected, to reduce
costs.
Brewers using air may add it to the hot side of the wort
cooler thus ensuring sterility, without the complication of
No large “nitrogen foams” will be additional gas sterilisation equipment. Because aeration
created in the fermenter.
on the hot side of the wort cooler may cause some colour
Concentration levels are adjusted pick up due to oxidative browning reactions with wort hot
easily and accurately. side aeration is predominantly used by ale brewers, where
Since oxygen is very soluble, usage
a slight colour pickup is less noticeable than in say a pale
costs are very low. coloured lager. Brewers adding it to the cold side must
ensure the air is adequately sterile-filtered, usually by a

50 General Certificate in Brewing

membrane cartridge filter system which can be steamed Here, the gas is being injected after the wort chiller. The
sterilised as part of the entire injection system. There is no wort flow rate is known. In simple systems this will simply
point in having a sterile filter if the rest of the gas injection be as a result of using a fixed speed pump. More
system is not equally sterile. sophisticated systems will have a flow meter in the wort
main (not shown). The wort flow rate is controlled to a
Brewers using oxygen invariably add it to the cold side of setpoint, and the gas injection rate set according to a fixed
the wort cooler. The mass of pure oxygen required is only flow rate.
approximately one fifth of the mass of air required, and so
the risk of it not dissolving is much lower than the A more sophisticated system (shown at the bottom of this
equivalent mass of oxygen added as air. page) will incorporate computer control of the gas injection
to be able to achieve a constant addition rate in response
In order to dissolve oxygen up to about 10 ppm, a slight to the measured wort flow rate. The back pressure control
excess of air needs to be added. Shallow FVs in particular valve will maintain the pressure at a suitable constant
will allow the excess to flash off, but with the risk of value, say 4 bar to increase the rate at which the gas
creating considerable foam. dissolves. Finally, a dissolved oxygen sensor can be used to
monitor the actual dissolved oxygen levels. The system can
If using oxygen, or requiring a very accurate DO2 of less then incorporate alarm handling to warn the operator the
than about 10 ppm when using air, then it is necessary to process is out of control, or to shut it down, and to provide
introduce some form of control system such as that shown management information to allow validation of oxygen
below:- addition compared to fermentation performance.

Notes
• What type of cooling system is used in the brewery that
you are familiar with?
• How is the wort aerated?

Learning Material 2016 51

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

52 General Certificate in Brewing

Section 5 The basic principles of yeast fermentation

5.1 Brewing yeast

The relationship to other organisms

Yeasts are eukaryotic (cells containing complex structures
enclosed within membranes) microorganisms (organisms Saccharomyces cerevisiae Saccharomyces pastorianus
too small for the individual cell to be seen with the naked or or
eye) which form part of the kingdom Fungi. Lager Yeast
Ale Yeast
Yeast is a single celled fungus. It is capable of growing
anaerobically (i.e. in the absence of air) and breaks down
sugars to release energy, producing carbon dioxide, The ‘top’ yeast used for The ‘bottom’ yeast used for
alcohol and water. fermenting ales. fermenting lagers.

Top & bottom fermenting yeasts

It floats to the top of the It sinks to the base of the
vessel at the end of vessel at the end of
Brewing yeasts may be classed as "top-cropping" (or "top- fermentation because the fermentation because it has
fermenting") and "bottom-cropping" (or "bottom- carbon dioxide bubbles a different kind of cell wall.
fermenting"). Top-cropping yeasts are so called because stick to the yeast’s cell
they form a foam at the top of the wort during walls.
fermentation. An example of a top-cropping yeast is
Saccharomyces cerevisiae, sometimes called an "ale yeast” It thrives on relatively high It likes low fermentation
fermentation temperatures, for example
temperatures, for example 10 °C and fermentations are
Bottom-cropping yeasts are typically used to produce
20°C and consequently slower, for example 7 days.
lager-type beers, though they can also produce ale-type
fermentations are fast, for
beers. These yeasts ferment well at low temperatures. An
example 3 days.
example of bottom-cropping yeast is Saccharomyces
pastorianus, (known as S. carlsbergensis in the 1970's).
Ale strains cannot grow Lager strains cannot grow
In addition to behaving differently and producing different
above 37 °C. above 34 °C.
beer types, ale and lager yeast are genetically very
different. S.pastorianus is unusual in being a natural
hybrid of two yeasts, S. cerevisiae and a low temperature
The system used for The system used for
wine yeast, S. Eubayanus.
cropping the yeast at the cropping the yeast at the
end of fermentation, that end of fermentation, that is
Top- and bottom-cropping and cold- and warm-fermenting
is skimming the yeast off collecting from the base of
distinctions are largely generalizations used by non-
the top of the beer, the vessel is not selective
brewers to communicate to the general public.
naturally selects the best and usually a pure culturing
yeast for repitching. system is in use to maintain
Within each type of yeast there are numerous strains, with
yeast purity.
each strain performing differently in terms of which sugars
it can ferment, how effectively it settles out after
Beer containing this yeast Beer containing this yeast
fermentation, and what flavours it produces. There are
can be clarified by the cannot usually be clarified
numerous strains of yeast used in brewing, many having
addition of finings. by finings.
characteristics that create unique flavours during
fermentation.
It cannot ferment a sugar It can ferment a sugar called
For this reason, many beer brands have their own specific called ‘melibiose’. ‘melibiose’.
pitching yeast. Some breweries deliberately have more
than one strain in their pitching yeast in order to provide
characteristics that just one of the yeasts alone would not
provide.

Learning Material 2016 53

Microscopic appearance Subcellular structures
Yeast is a single celled micro-organism, which is larger than
any bacteria. • Each yeast cell is bounded by a rigid cell wall (made
of protein and polysaccharides).

• The cell wall encloses the cell membrane

(plasmalemma), which regulates the wort materials
that are taken into the cell.

• Inside the cell membrane lies the cell cytoplasm

which is permeated by internal membranes such as
the endoplasmic reticulum (which is involved in
protein synthesis) and Golgi body.

• Within the cytoplasm are:

o the nucleus, which contains all the cell’s genetic

material as DNA; the nucleus divides each time
the cell buds, so that the bud has the same
genetic material as the mother cell.
Yeast cells normally reproduce asexually. That means that
o the vacuole, which is a main storage organelle.
they do not “mate” with another cell. They bud new
daughter cells from a mother cell. Bud scars occur when
o the mitochondria, which are involved in many
daughter cells separate from their parents. The greater the
enzyme reactions, especially energy production
number of scars, the higher the number of generations, and
during aerobic respiration (which does NOT
the older the parent cell. There is a limit on the number of
operate during fermentation) and synthesis of
daughters a yeast cell can have and hence the age of a
key lipid compounds (fatty acids and sterols).
yeast cell.

(It is possible to induce most yeasts to reproduce sexually. o the cytoplasm itself contains many enzymes,
including all enzymes involved in fermentation.
They normally only do this under stressful conditions. It
seems to be a survival mechanism. The resulting spores are
Bud formation
very tough and can survive long periods without suitable
Yeast cells multiply by ‘budding’ as shown in the diagrams
growth conditions, but these conditions are never met
below:-
within brewery operations).

Under the microscope, the appearance of the cells gives

information about the yeast. 1. 2. 3.

• Bud scars indicate its age; older cells have produced

more buds.

• The shape and size of the vacuole changes with age.

It becomes bigger as the cell ages. This is strain
dependent.
New bud
New cell scars
• The size of the cell gives an indication of the strain.
They generally grow larger as they grow older.
Nutritional requirements of yeast
• The presence of chains of cells indicates the class of
yeast. These chains encourage flocculation and When oxygen is available (aerobic conditions) to the yeast
forms one of the methods of classifying yeast. sugars are mainly converted into carbon dioxide and energy
is created to produce new cells. Some unpleasant by-
• Yeast is classified depending on how it performs products are also produced.
during the fermentation, including flocculation as
noted above.

54 General Certificate in Brewing

When there is no oxygen available (anaerobic conditions),
the yeast primarily utilises the sugar to produce alcohol
(ethanol), carbon dioxide and a range of aromatic
substances (esters and higher alcohols). While under
anaerobic conditions new cells are not produced in large
numbers.

Yeast has nutritional requirements other than just sugar

including:-

• Protein or nitrogenous compounds in the form of

amino acids. These are derived from the barley Anaerobic conditions – increased
protein during malting and mash conversion. Aerobic conditions – increased growth
alcohol production.
rate.
• Lipids or fatty material. This is also supplied by the
This equation summarises the many metabolic reactions
malt.
occurring during fermentation, all controlled by a variety of
• Vitamins from the malt. different enzymes in the yeast cell. The main purpose of the
breakdown of glucose to alcohol and carbon dioxide is to
• Trace metals. Calcium is usually present in the generate energy necessary for the yeast cells to survive and
brewing water, if not it must be added as described grow. However, many of the metabolic reactions carried out
in module 6.1. Zinc may be present in hop products, by the yeast, such as making proteins and fats for new cells,
if not it can be added to the wort. Copper may also also produce by products, which can be very important to
be present in hop products, but if stainless brewing beer flavour. (see section 11 – flavour, for further details)
plant is used, may have to be added to the wort.
These by products, such as esters, higher alcohols, diacetyl
• Oxygen is usually dosed into the wort. Oxygen is and sulphur compounds, can make major contributions to
essential for healthy yeast growth and a large yeast beer flavour and various fermentation conditions can
population is required to ensure that the influence the amounts of these compounds.
fermentation is healthy and fast.
Beer Flavour Compounds

5.2 Fermentation theory

The production of alcohol & CO2

Most living organisms respire aerobically. They use oxygen

to convert sugars to carbon dioxide and water. This releases
the energy. Some micro-organisms, including yeast, are
able to metabolise anaerobically. They do not need to use
oxygen to breakdown carbohydrate. However the process,
known as fermentation is inefficient and instead of CO2,
water and energy, it converts those sugars into alcohol and
carbon dioxide plus considerably less energy.

The process starts when yeast is pitched into the wort and
finishes when most of the sugar has been converted into Not all of these flavours are desirable. Ethanol (alcohol)
alcohol and carbon dioxide. itself only makes a minor contribution to beer flavour, other
than having a warming effect.
The overall reaction for fermentation is:
Esters
C6 H12 O6 -------► 2 (C2 H5 OH) + 2 (CO2) + Energy Esters are very important beer flavour compounds and
Glucose Ethanol Carbon several hundred different compounds can be found in beer,
(sugar) (alcohol) Dioxide although only a few are present in sufficient amount to
contribute significantly to beer. The flavours generated by
esters are described as “fruity” and “tropical fruit”. These
compounds are essentially formed by combination of
alcohols with organic acids, so that those present in the

Learning Material 2016 55

highest quantity, such as ethyl acetate (which contributes This character is often acceptable, and may even be
“boiled sweet”, almost “solvent” flavour character), are considered desirable in ales at low levels, but is usually
derived from ethanol (since this is by far the most abundant unpleasant in lagers. Lager processing is designed to
alcohol). Another very flavour active ester is iso-amyl reduce the level of diacetyl to below its flavour threshold of
acetate, which is usually present in high enough levels to approximately 25 ppb or micrograms / litre (µgm/ litre).
taste (i.e. above its “flavour threshold”) and tastes of
“bananas” or “pear drops”. Diacetyl is produced during fermentation, but yeast will
reabsorb it (and so convert the diacetyl to less flavoursome
Esters are formed during fermentation by esterification of compounds) during a warm conditioning stage.
fatty acids with alcohols. The amounts of individual esters Consequently, it is very important (especially for lager
and the total produced are affected mainly by the same brewing) to monitor, by chemical analysis, the level of
fermentation factors that affect yeast growth. diacetyl towards the end of fermentation and during
maturation to ensure that the beer is not chilled before the
Especially important is the strength of the original wort (i.e. level of diacetyl has reduced to achieve the final beer
wort gravity). Stronger worts usually produce very high specification.
levels of esters and so, strong beers taste very fruity. In
fact, it is the proportion of fermentable sugars to the The desired beer diacetyl specification determines when
amount of assimilable nitrogen (mainly amino acids derived the beer may be moved from fermentation vessel to the
from malt proteins during mash conversion) that is the conditioning phase, or chilled, or centrifuged or filtered.
main driving force in determining the levels of ester
production. Factors affecting diacetyl production (and removal by yeast)
are:-
Other factors that encourage yeast growth, such as • The yeast strain.
increased dissolved oxygen at the start of fermentation,
reduce ester formation. • Wort composition.

Increased fermentation temperature encourages ester • The type of fermentation vessel (open or closed).
production.
• Fermentation conditions favouring yeast growth
However increased pressure during fermentation tends to rate, such as high temperatures and pitching rates,
decrease yeast growth and thus reduces ester formation. and an increased level of wort oxygen.
This means that fermentations in very tall vessels produce
lower levels of esters, because of the increased hydrostatic Sulphur compounds
pressures. Sulphur compounds make a significant contribution to beer
flavour. When in excess, they can give rise to unpleasant
Higher alcohols off-flavours. The fermentation should be managed with the
Higher alcohols (also known as Fusel Alcohols) are measures described below to make sure the amount
produced as by products from protein synthesis and have remaining in the final beer is below the flavour threshold.
aroma and flavour effects such as “alcohol” and “winey”. This is especially important for the more volatile
The main examples are iso-butanol and iso-amyl alcohol. compounds such as hydrogen sulphide (H2S), which smells
of bad eggs and sulphur dioxide (SO2) which smells of burnt
The total concentration of higher alcohols produced during matches. Both of these sulphur compounds are produced
fermentation is directly related to amount of yeast growth, by yeast from sulphate and are by-products in the synthesis
so that factors increases yeast growth also favour increased of sulphur-containing amino acids.
production of higher alcohols:-
The control procedures include:-
• Increased level of wort oxygen.
• Ensuring sufficient evolution of CO2 to purge these
• Higher levels of wort FAN (free amino nitrogen). volatile compounds from the beer.

• Increased fermentation temperature. • Extended maturation time (to allow these sulphur
compounds to escape).
Increased pressure during fermentation tends to decrease
yeast growth and thus reduces higher alcohol formation • More vigorous fermentation processes result in
(like ester synthesis), so that fermentations in very tall lower levels of the volatile sulphur compounds.
vessels produce lower levels of higher alcohols, because of
the increased hydrostatic pressures. • Not allowing settled yeast to remain the
fermentation vessel for too long. If settled for too
Diacetyl long yeast may break down and release other
Diacetyl gives a “toffee” or “butterscotch” flavour to beer. unpleasant sulphur flavours (“cooked meat”,
“autolysed yeast”).

56 General Certificate in Brewing

One other sulphur compound often found in beer, but acids and by the amount of oxygen added to the wort. The
principally derived from malt is Dimethyl Sulphide (DMS), specific gravity drops rapidly during the fermentation
which smells and tastes of “cooked vegetables” or “tinned phase. The fermentable sugars are quickly converted into
sweetcorn”. alcohol, large volumes of carbon dioxide are produced and
heat is generated. The pH of the beer also drops during
This compound is rarely detectable in ales, because it is fermentation.
usually removed during kilning to produce ale malts, but Because specific gravity drops so rapidly and alcohol
may be intentionally present at tasteable levels in some content increases so rapidly, this phase of the fermentation
lagers, although others are designed to have specification is often referred to as the Logarithmic (Log) or Exponential
levels of DMS below flavour threshold (approximately 30 phase.
ppb or micrograms /litre or µgm /litre).
Retardation phase
The level of DMS surviving into beer is very much The growth phase is followed by a retardation (late
determined by the amount of DMS (and its precursor) fermentation) phase which is limited by one or more of the
surviving in malt after kilning and then how much remains following:-
after wort boiling. Those lager brewers who specify a
tasteable level of DMS in the finished beer will specify • Available fermentable sugars.
desired levels in malt and will design the wort boiling
conditions so that a controlled level of DMS will remain in • Free nitrogen (amino acids).
the finished beer. Otherwise malt specifications and boiling
conditions will be designed to ensure sufficient removal of • The increase in alcohol level.
DMS to achieve the required low level in beer.
• Settling or flocculation of the yeast.
One important point is that some yeasts can produce a
small amount of DMS during fermentation, which may be and to a certain degree, by lack of recirculation currents
significant, although it is usual to control DMS levels in beer keeping the yeast in suspension.
by malt specification and boiling conditions.
Stationary phase
Main phases of a fermentation There is a balance between the number of newly formed
Four different stages of fermentation are normally cells and the cells which die. In the latter stages, sometimes
described. called the declining phase, the rate of cell death exceeds
the rate of new cell formation.
Lag phase
Nothing happens to the wort specific gravity until the yeast The final stages of fermentation are slow and it is where the
has been pitched in. Yeast growth/ reproduction and yeast tends to "mop up" available nutrients that are
fermentation do not start immediately. The yeast cells available. Other biochemical reactions continue, the most
metabolism becomes active following a period of relative important being the removal of diacetyl. Top fermenting
inactivity during storage. The length of this phase depends yeast may be cropped at this stage. The beer may be
on the type of yeast, the pitching rate, its health, in many reduced in temperature.
cases including the age (number of times it has previously
be repitched), and the conditions within the wort. The lag Example of an ale fermentation profile
phase is caused by the yeast re-adjusting to the new
environment and beginning to absorb and combine the
nutrients and oxygen to give them everything required for
growth and reproduction. The phase ends with the first cell
division.

Growth (logarithmic or exponential) phase

The lag phase is followed by a rapid growth phase, starting
between 6 and 12 hours after pitching. During the first part
of this phase, the rate of cell division continuously
increases. The specific gravity drops slowly at first whilst
the yeast is growing and dividing. How long the
accelerating growth lasts largely depends on the
temperature. After about 24 hours the growth rate is
constant and at a maximum. The cell numbers can double
every 90 to 120 minutes. The conversion of sugars into alcohol can be tracked by
measuring the specific gravity of the liquid. Alcohol is less
Growth is only limited by physical parameters such as dense (lighter) than sugar and CO2 is lost, so specific gravity
temperature and the availability of nutrients such as amino drops as the fermentation progresses.

Learning Material 2016 57

The significance of oxygen The various fermentation conditions that are important in
this respect include:-
Oxygen is required in sufficient quantities to allow the yeast
to synthesise sterols and unsaturated fatty acids which are • Selection of pitching yeast.
not available in the wort, and which cannot be synthesised
in anaerobic conditions. Under anaerobic conditions • Pitching rate (the amount of yeast added to the
brewers yeast strains require both pre-formed sterols and wort). The amount of yeast in suspension can be
unsaturated fatty acids as they are critical for cell measured by ‘yeast count’.
membrane function and integrity. o Ales are typically pitched at approximately 9
million cells per ml.
Inadequate growth of a brewery yeast culture will result in o Lagers (typically) at 14 million cells per ml, but
poor attenuation, altered beer flavour, inconsistent possibly higher when beers are high gravity
fermentation times and recovered pitching yeasts which brewed.
are undesirable for subsequent fermentations.
• Wort dissolved oxygen (the amount of air/oxygen
Perhaps unexpectedly, over-vigorous aeration of added to the wort).
fermenting worts can lead to increasingly sluggish
fermentations characterised by longer lag phases, a slower • Initial temperature (wort temperature before the
fermentations and/or residual sugar remaining in the final yeast is added).
beer.
• The rate of temperature increase during the growth
Factors affecting the phases of fermentations phase.

As noted before, the key factors are:- • Top heat (the maximum temperature during
fermentation).
• The pitching rate of yeast.
• Final temperature (what temperature the beer is
• The yeast strain – including flocculation
reduced to at the end).
characteristics.

• The age of the yeast – older yeasts tend to produce • Fermentation vessel design / shape.
more sluggish / abnormal fermentations.
Consistent application and tight control of these
• The wort oxygenation level. parameters is required to produce a fermentation of
consistent speed so that the beer produced has consistent
• The wort temperature – including the control of the quality and flavour characteristics.
temperature rise.

• The wort composition in terms of nutrients – Notes

minerals, vitamins, amino acids. • Describe the yeast used in the fermentation of a beer
that you are familiar with.
• The sugar concentration. • Observe your brewery’s pitching yeast under the
microscope and draw a diagram.
• The amount of alcohol produced associated with the
• Draw the temperature profile of fermentation you
alcohol tolerance of the yeast strain used.
are familiar with, and identify the key parameters of
• The vigour of mixing in the FV. temperature, gravity against time.
• Identify when key processes take place (e.g. cooling,
Factors affecting the speed of fermentations yeast cropping) and relate to the stage of yeast
growth.
The yeast used for brewing beer is carefully selected
because it influences fermentation performance and the
beer’s eventual flavour, by influencing the amounts of
various flavour compounds.

58 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 59

Section 6 Fermentation Practice
6.1 Fermentation vessels and their
control

The basic requirements of fermenting vessels Some brewers may also require the following:-

A fermentation vessel has a large number of functions, • Gas washing to remove unwanted volatiles
including those listed below:- (purging).

• Its prime function is to contain the fermenting • Wort aeration / oxygenation during fermentation
wort. (e.g. for barley wine production).

• It must protect the fermenting wort against ingress • Storage of yeast (under beer) for pitching
of foreign micro-organisms which could subsequent fermentations.
contaminate the fermentation.
• The use of the fermenter for cold conditioning of
• It must allow fermentation of wort at a controlled beer at temperatures of 0 ºC or below (Unitank or
temperature by having provision for cooling. dual purpose operations).

• Sometimes it is considered essential to ferment at • Final culture stages of yeast.

a constant pressure to control production of esters
and to a lesser extent foam. • The use of a vessel for a number of somewhat
different brewlengths, to suit the sales of different
• It must allow CO2 produced during fermentation to beers.
escape or be collected sufficiently pure for re-use.
In all cases the materials should ideally be:-
• It must allow, and preferably actively encourage • Non-toxic or staining.
mixing of the vessel contents to avoid layering and • Easily sanitised.
to disperse the yeast. • Corrosion resistant.
• Easily fabricated using a wide range of forming &
• It must be insulated (either directly or indirectly in
welding techniques.
a constant temperature atmosphere) to minimise
• Readily available.
influence of the ambient temperature affecting the
• Cost effective.
wort temperature.
• Strong over a broad range of conditions (pressures /
• The control must allow for elevation of the temperatures).
temperature of the fermenting wort to a desired • Pleasing appearance.
value for warm maturation to allow effective use • Scratch proof.
of the heat generated during the latter stages of • Non porous.
the fermentation (free-rise, mainly for diacetyl • Finished internally allowing high standards of
control). hygiene, being free from crevices or surface
roughness which could harbour micro-organisms.
• It must uniformly chill the contents to 1-3 ºC for
maturation and/or yeast sedimentation. Vessels have been made of the following materials, and
generally, where they do not meet the above criteria have
• The design and control must allow / encourage been superseded by materials and construction that do:-
sedimentation of the yeast and easy removal from • Wood.
the vessel while it is full. • Copper.
• Carbon steel lined with an epoxy resin.
• It is normally required to allow / encourage the
• Plastic, either as a lining or in small vessels, as
solution of CO2 produced during fermentation in
standalone tanks.
the beer, but not to excess.
• Fibre impregnated resin, either as a lining or in small
• It must be easy to clean, preferably using CIP vessels, as standalone tanks.
techniques. • Aluminium.
• Stainless Steel.
• It must retain sterility after cleaning, normally by
enclosing.

60 General Certificate in Brewing

Modern large vessels are invariably made of stainless steel though cropping only the best portion of the yeast for
due to the strength, hygiene factors (scratch resistant, repitching is not possible.
chemical resistance, non porous etc.), though some small
brewers use plastic or fibre impregnated resin tanks, mainly Fermentation – key activities
due to purchase costs.
All fermentations, irrespective of FV design, or the yeast
Operating principles and diagrammatic representation of used have a number of key activities:-
FVs, reasons for choice, advantages & disadvantages
• Collection (transfer of wort at the correct
Older vessels were often rectangular, usually not enclosed, temperature, gravity and wort oxygen level in the
and made of wood or copper. They typically had internal FV).
pipes to carry cooling liquids. Control was simple and very
variable, generally manually controlled. • Pitching (either into the transferring wort, or directly
into the FV).
Improvements were made by enclosing vessels to improve • Attemperation (cooling to a specified temperature
sterility, combined with basic in-place cleaning systems. profile).
Ultimately the conical fermenter was developed.
• Rousing (if required).
Current systems in use
• Traditional ale fermentations are carried out in • Gravity monitoring to ensure fermentation is
shallow open vessels (wood, slate, stainless steel, proceeding to specification).
copper or epoxy lined) with top cropping of yeast -
• VDK (diacetyl) control - mainly by a period of warm
“squares”.
maturation / late fermentation.
• Burton Unions and Yorkshire stone squares are
elaborate ways of collecting pitching yeast and • Cooling to transfer temperature.
regulating the amount of yeast left for cask • Yeast removal (may follow beer transfer in some
conditioned beer. vessel designs).
o
• Flat/sloped (12 angle)-bottomed rectangular,
• Green beer transfer.
enclosed vessels, usually stainless steel or mild steel
with an epoxy lining, sometimes known as Asahi • Cleaning / sterilisation.
tanks. These were developed in Japan and the
United States. Sizes can range from 300 hl to 3,000 Open & closed squares
hl. They are used normally as fermenters, but These are the traditional fermentation vessels, though
sometimes as maturation vessels, occasionally as recent ones, as shown in some of the following photos are
combination vessels for fermentation, maturation manufactured using stainless steel. Note that “squares”
and cold conditioning (unitanking). come in all sorts of different shapes and sizes, including
round and oval FVs. Insulation is not shown on the
• Spherical fermenters. Optimum geometry in terms
drawings.
of surface area to volume. In 1970 large numbers of
vessels were installed in Spain with 3,000/5,000 hl
capacity each. They may also be used as unitanks.
However for good yeast settlement and cropping, it
is necessary to fit them with conical bottoms.

• Continuous fermentation. This method followed

considerable R&D in 1960’s and early 70’s. The
process was discontinued except in New Zealand.
There was renewed interest with immobilised
systems in the 1990’s.

• Cylindro-conical vessels for use as fermenters,

maturation vessels or unitanks. Probably the most
popular vessel currently employed in brewing world- The yeast may be pitched into the wort stream, but is
wide. commonly pitched in as slurry or as pressed yeast cake
directly into the FV.
The major influence on the design of a fermenting vessel is
the behaviour of the yeast, whether it is top or bottom The wort is allowed to rise to top temperature and is then
cropping and whether or not it settles out (flocculates) cooled using wall cooling panels, or internal coils or
readily. It has proven possible to use bottom cropping suspended panels. The formation of a yeast head largely
yeasts in covered squares and other flat bottomed vessels prevents contamination by non-brewing yeast and bacteria.

Learning Material 2016 61

Wort rousing Disadvantages
• Risk of airborne infection pickup (or other organisms
such as flies).
• Difficult to clean and sterilise – especially if open
vessels. Open vessels usually cleaned manually –
safety implications due to confined working space.
Closed-in vessels can be fitted with CIP.
• High labour costs, particularly where vessels are
manually cleaned.
• Poor CO2 recovery / extraction – safety concern and
potential increased costs due to purchased CO2.
• Flat bottoms can lead to high losses from settled
yeast. Difficulty recovering yeast settled on bottom
due to lack of access and normally virtually
horizontal bottom.
• Generally small volume, with large footprint, so
Example of internal cooling coils space / cost considerations.

Yorkshire squares
A Yorkshire Square vessel consists of a shallow fermenting
vessel above which is a walled deck. The wort is fermented
in the lower part of the FV, while the yeast head is collected
on the deck above. During the first stage of fermentation,
the fermenting wort is periodically pumped from the
bottom of the FV over the top deck, to keep the yeast
mixed in with the wort. Later, the mixing is stopped and the
green beer in the lower FV allowed to settle and to cool
gently. Most of the yeast rises onto the deck, and is left
behind when the beer is drained from the lower FV.

If necessary, the wort is roused to mix the wort, to re-

suspend settled yeast and or to introduce additional air to
ensure the fermentation progresses as required.

An upstand (thimble) is frequently fitted in the outlet to

retain the yeast and trub which has settled on the bottom
of the vessel, preventing it being dragged into the beer as it
is transferred. The thimble is then removed for yeast
recovery and vessel cleaning.

Enclosed vessels are fitted with equipment for CIP rather The advantages and disadvantages are virtually identical to
than manual cleaning. Removable covers and portable CIP those of conventional “square” FVs.
equipment can be used to clean older vessels rather than
cleaning manually. Modern vessels are fitted with equipment for CIP rather
The following section identifies some of the advantages and than manual cleaning.
disadvantages of “squares”, both open and closed.
Burton union
Advantages Wort is half fermented in conventional squares, and then
• Shallow, so low retained CO2 content and thus transferred to casks (8-10hl each) for further fermentation.
suitable for cask beer without degassing. Yeast is forced through swan necks to a yeast back where it
• Can be used for a multiple of different brewlengths separates naturally from the associated beer. The beer is
when low level internal coils are fitted. Less allowed to flow back into the casks. The yeast is a non-
flexibility with cooling panels. flocculent strain.
• Top cropping yeast tends to be self-selecting, so
many brewers do not regularly culture new yeast.
• Great for PR purposes.
62 General Certificate in Brewing
 All the yeast is removed before the beer is transferred,
unlike square FVs.

Advantages
• Full flavoured beers can be produced.
• The beer when racked off has a comparatively low
yeast cell count and is suitable for cask racking
without further settlement.
• Great for PR purposes.

Disadvantages
• Requires conventional fermenter for first stage, and
union system for second. Expensive.
• The union is complex, and difficult to clean.
• The casks cannot be cleaned with detergents or
sterilants – hot water only. The large number of
casks and the open trough create a significant
microbiological risk.
• The casks require a cooper to maintain in good
condition.
• High losses due to large numbers of small vessels.

Spherical tanks
The vessels are used as unitanks, and use highly flocculent
yeast. Typical layout of cylindroconical FV

Because it would be difficult to crop yeast from an entire Key

sphere, a conical base is fitted. Cooling is provided by wall PRV = pressure relief valve
jackets arranged in four rings around the spherical part of AV = anti vacuum valve
the vessel, plus a cone cooling jacket. These are large TTx = temperature transmitter
vessels, the ones installed having a capacity of 5,000 hl
each. The diameter is 10 metres, height 12 metres. In the majority of breweries the attemperation is via wall
and cone cooling jackets, which are surrounded by thermal
None have been installed recently due to construction insulation. A number of breweries have the vessels
costs, and the foot print required, which is considerably installed in a thermally insulated room which is cooled
higher than similar volume cylindroconical vessels. using dried air. The vessels have individual cooling jackets,
but do not have individual thermal insulation. Adequate
Cylindroconicals (conicals) insulation is provided by the air. Some breweries use
The vessels are stronger and lighter, and require a smaller insulated vessels and rousing loops containing in-line
footprint than rectangular vessels of the same capacity. The chillers instead of wall jackets. The loops may also contain
shape of the vessel causes a vigorous fermentation. facilities for post collect aeration / oxygenation or
Fermentation is completed more quickly than in shallower carbonation.
rectangular vessels.
CO2 bubbles generated during fermentation cause strong
The advantage of the conical fermenter is primarily circulation currents. This ensures consistent yeast
economic. A large volume of wort can be stored in a concentration throughout the wort, and improves the
relatively low ground surface area. Bottom cropping yeasts growth rate of yeast. It also gives more effective cooling as
which settle after fermentation is complete and the vessel the wort passes over the cooling surfaces.
has been cooled are used.

Learning Material 2016 63

Cylindroconical FV – circulation currents during Cylindroconical FV – circulation currents cooling below
o
fermentation (simplified) approx. 4 C (simplified)

The conical fermenter is ideal for bottom cropping yeast. Advantages

The cone makes it easy to collect yeast. There is also a • Stronger/lighter than rectangular vessels.
small, but significant saving in the "loss" of bittering • Slender shape occupies little ground area, reduced
materials by yeast adsorption with bottom settling yeasts. capital costs.
• Fermentation completes faster than rectangular
The totally enclosed design makes it easy to incorporate in fermenters.
place cleaning using either sprayballs or high pressure • CO2 emission causes strong circulation currents
cleaning heads. However enclosure also makes it necessary resulting from long bubble path.
to incorporate pressure and vacuum relief devices. These • This improves the growth rate of yeast and thus
are essential to prevent explosion or collapse. The design of faster fermentation.
the vessel, the quantity of CO2 remaining after emptying, • It also gives more effective cooling.
and the type of cleaning reagents and temperatures used • Ideal for bottom fermenting yeast (cone collection)
for cleaning must all be considered when preparing a • Easy to collect CO2.
cleaning regime. See the sections 15 & 16 for further • Greater hop utilisation (absence of top crop which
details. absorbs hop resins).
• Improved cleaning and reduced beer losses resulting
CO2 from the fermentation can easily be collected with
from the excellent draining and rinsing
minimal wastage of impure gas due to the effective
characteristics of the vessel.
headspace purging.
• Improved product flexibility (lagers and ales can be
produced in the same vessel) and consistency.
Thermometers are required at different heights, to
• Low cross sectional area at the top of the vessel
accommodate the different density of wort / beer at
makes it easier to apply a top pressure in order to
different temperatures. During fermentation, convection
contain the fermentation head, assist in the purging
currents are created in the FV, with the wort in contact with
of air prior to CO2 collection and venting during
the cooling panels becoming denser, and falling, with the
maturation/ageing (unitank operation).
warmer beer in the centre rising. So the coldest wort is
towards the bottom of the vessel. The temperature probe
The reasons for temperature control
therefore measures wort at its coldest, and will stop cooling
Under brewery conditions yeast metabolises sugar by
if below the temperature setpoint. At the end of
o fermentation:
fermentation, when cooling to less than 4 C, when the beer
o
is colder than 3.5 C, the density decreases, and the cold
beer rises to the top of the vessel alongside the cooling
C6H12O6  2(C2H5OH) + 2(CO2) + Energy
jackets, and back down the centre of the FV. A high level
Glucose ethanol carbon dioxide
probe is therefore required to prevent ice formation at the
top of the vessel.

64 General Certificate in Brewing

When an energy rich substance, such as glucose, is broken • The temperature of the fermentation affects the
down to form a compound with a lower energy content (for time taken, which in turn affects the pH of the beer.
example, ethanol), the excess energy (originally derived Slow (perhaps due to being cold) fermentations
from photosynthesis when the barley grew) is released. produce beer with high pH’s. Time also affects
Depending on whether the glucose is respired or fermented flavour because sluggish yeasts can release
the amount of energy released is different. Approximately unpleasant sulphur compounds into the beer,
25 times more energy is released during the respiration of especially at warmer temperatures.
glucose than during the fermentation of glucose by yeast.
It is important therefore, that the following temperature
During fermentation under production brewing conditions, related elements of the fermentation are under strict
the amount of heat is approximately 586.6 KJ/kg of control:-
fermentable sugar. • Initial temperature (wort temperature before the
yeast is added).
Wort is usually 70% fermentable. One hl of wort may • The rate of temperature increase during the growth
o
contain 12 kg (12 P or 1048) of extract. Of this, 8.4 kg is phase (phase two).
fermented during the primary fermentation. Consequently • Top heat (the maximum temperature during
586.6 x 8.4 = 4927 kJ are produced by every hl of wort. This fermentation).
heat generated must be removed during fermentation by • Final temperature (the temperature that the beer is
cooling in order to:- reduced to at the end).

• Ensure that the fermentation temperature is Consistent application of these parameters will help
maintained at the set level which prevents the produce a fermentation of consistent speed and a beer with
formation of unwanted flavours. consistent quality and flavour characteristics.
• Ensure yeast viability.
Temperature has an effect on the metabolism of yeast (as
• Reduce fobbing.
in any organism). Simply put, the higher the temperature
the faster the reactions and vice versa. However this effect
Key criteria include:-
on the rate of yeast respiration has other effects, such as
high ester production and the pattern of yeast growth. Thus
• If cooling is applied early, the yeast will be unable to
it is essential to control the temperature curve so that it
grow and the fermentation will stick.
complies as closely as possible with your standard
• If cooling is not put on whilst yeast is actively fermentation as set by your local specification.
fermenting the fermentation temperature will rise to
an unacceptable level causing damage to the yeast. Procedures for the temperature control of fermentations
• Crash cooling during the active stage of yeast growth
tends to stop the fermentation. The supply of coolant, e.g. chilled liquor, I.M.S. (Industrial
• Attemperation should be carried out gently using Methylated Spirit) or glycol, is important and frequent
feedback control. checks should be made on the supply and temperature.
• The process today is normally controlled Slowing or insufficiently fermented brews may be revived
automatically by setting the required temperature, by allowing a higher temperature before the end of
measuring the beer temperature with a probe in the fermentation. This may however create undesirable by-
vessel, and allowing this to control the flow of products.
coolant to the vessel.
• Where an automatic system is not used, the checks This stops any further fermentation and also prevents any
(thermometer reading) must be carried out potential yeast autolysis (yeast break down). The green
frequently and regularly, and the coolant applied by beer is typically cooled by 1°C per hour, so preventing ice
manually opening a valve. formation on the cooling jackets / coils, and ensuring the
beer is cooled consistently. There is also less risk of thermal
The fermentation conditions determine many of the flavour shock to the yeast, which might lead to autolysis.
characteristics of the final beer:-
Cooling too early can result in green acetaldehyde and
diacetyl flavours. Cooling too late can result in yeasty off
• The initial temperature and ‘top temperature’ of the
flavours from yeast autolysins. The end of fermentation is
fermentation affect the amount of aromatic volatile
decided by the specific gravity reaching the preset
substances produced. For example, more esters are
attenuation value for the brand. Other indicators are a drop
produced at high temperature. Fermentation itself
in CO2 production and the flocculation of the yeast. In
generates a lot of heat which must be removed to
many breweries the start of cooling is initiated after
avoid production of excessive quantities of esters.
analysis has confirmed that diacetyl levels have dropped
below the level stipulated as maximum for the brand.

Learning Material 2016 65

Typical maximum levels for diacetyl are 25 ppb or micrograms 6.2 Health & safety
/ litre (µgm/ litre) for lager, or 100 ppb or (µgm/ litre) for
some ales. The evolution of CO2 from fermentations

Example of a top fermenting ale fermentation profile During fermentation CO2 gas is produced. However, in
FVs, virtually all CO2 is produced as a result of
fermentation.

C6H12O6  2(C2H5OH) + 2(CO2) + Energy

Glucose ethanol carbon dioxide

Some of the CO2 remains dissolved in solution, but most

is released as gas bubbles, also helping the mixing of the
fermenting wort. The FV must be designed to allow the
release of the gas into the atmosphere, or in larger
plants, into a collection system where it may be
recovered for re-use in the brewery.

Example of a bottom fermenting lager fermentation profile The hazards associated with CO2

During fermentation CO2 gas is given off as noted

previously. Breweries produce large volumes of the gas.

CO2 Effects and Symptoms

concentration
by volume of
air
1% Slight and unnoticeable increase in
breathing rate – this is the level
commonly used to evacuate an
area.
2% Breathing rate increases (increase
to 1.5 times normal rate), and
The progress of fermentation is measured by the fall in the prolonged exposure over several
value of the specific gravity using a Saccharometer. Since hours may cause headache and
alcohol is less dense than the sugars which have been feeling of exhaustion
fermented its production results in falling gravity. 3% Breathing becomes deeper
(increase to twice normal rate).
The gravity of the fermenting wort should be measured Hearing ability reduced, headache
regularly, typically at least every 12 hours. This gravity is experienced with increase in blood
measured using a saccharometer/hydrometer or pressure and pulse rate
densitometer. The gravity readings (Present Gravity or PG), 4–5% Breathing becomes deeper and
and the temperatures are best plotted on a graph and more rapid (increase to four times
compared to a standard profile to monitor the progress of the normal rate). Signs of intoxication
fermentation, and to help determine if cooling needs to be after exposure for half an hour, with
started or stopped. slight choking feeling.
5 – 10 % Characteristic pungent odour
Automation allows the cooling to be applied to maintain the
noticeable. Breathing very laboured
temperature of the wort / green beer, typically to within 0.5
leading to physical exhaustion.
deg C of the setpoint. The use of a target attemperation
Headache, visual disturbance,
(temperature / time) profile reduces the amount of manual
ringing in the ears and confusion,
input required. Automated sampling for specific gravity may
probably leading to loss of
also be used, though is not common due to complexity of
consciousness within minutes.
design and difficulty in maintaining good hygiene. The simpler
10 – 100 % Loss of consciousness more rapid,
method is to use two pressure transmitters a known vertical
with risk of death from respiratory
distance apart and calculate the gravity according to the
failure. Hazard to life increases with
apparent distance apart – the greater the apparent distance,
the percentage concentration, even
the greater the density.
if there is no oxygen depletion.

66 General Certificate in Brewing

 • It is toxic over 5% v/v. Continuously running gas detectors linked to alarm
• When pure, it is odourless – the smells normally systems with audible and visual alarms should be installed
noted being the result of impurities and the tingle as wherever possible in the FV rooms as there is a risk of CO2
CO2 dissolves in the nasal passages etc. to form accumulation.
irritating dilute carbonic acid.
• It is heavier than air and can accumulate in a Where this is not possible, then regular checks should be
fermentation room if inadequately ventilated. made and recorded using hand held devices. These may
• Large amounts remain in the vessel itself after it has be chemical reaction tubes, or more usually nowadays,
been emptied. portable electronic devices, capable of measuring both
CO2 and oxygen content simultaneously.
• It kills by asphyxiation rather than poisoning.
• It is moderately difficult to detect, special electronic All monitoring equipment must be regularly serviced and
equipment or calibrated chemical reaction tubes calibrated.
being required for accurate assessment.
• The first evidence of high atmospheric levels is Note that all sample points must be at low level, because
shortness of breath. CO2 is denser than air and will settle under calm
conditions.
CO2 rapidly dissolves in caustic CIP solutions.
2 NaOH + CO2  Na2 CO3 + H2O Fermenting vessels and maturation vessels are classed as
Sodium hydroxide Sodium Carbonate confined working spaces and CO2 and oxygen levels must
be checked as being OK before anyone can enter the
Na2CO3 + CO2 + H2O  2 NaHCO3 vessel. The atmosphere must then be continuously
Sodium Carbonate Sodium Bicarbonate checked whilst anyone is in the vessel. See below for
This creates two problems:- further details.

• Firstly, the reaction can cause the caustic detergent Safe working practices for fermenting room operations
to be significantly reduced in strength and
effectiveness. Large amounts of carbon dioxide are produced during
fermentation. Many fermenting rooms have facilities for
For every hectolitre of pure CO2 remaining, this will the safe extraction of CO2 out of the working area and in
react with approximately 200 g sodium hydroxide. some breweries the gas is collected directly from the FVs
Assuming a 2% w/w solution, this is approximately for further use. Because CO2 is heavier than air and can
10 litres. A 2,000 hl FV, with 400 hl head space as accumulate in a fermenting room or in the base of a tank
pure CO2 could completely neutralise approximately this creates a safety hazard.
40 hl of detergent.
Precautions for fermenting rooms include:-
• Secondly, if the vessel is closed in, but is not fitted • CO2 collection from fermentations – to remove the
with adequate anti vacuum devices, as can be seen CO2 safely.
from the volumes of CO2 that could be mopped up • Gas detection systems, with associated alarm
by the caustic, this could cause a sealed vessel to handling. It is essential to be familiar with your
implode. own sites emergency and evacuation procedures.
If the alarms (normally set to => 0.5% CO2 and
The monitoring / checking of atmospheres for safe <19% O2) are set off leave the area at once, open
working. windows and doors if possible, switch on extraction
fans if necessary.
The following are typical figures quoted. Note that
• Low level CO2 extraction systems. These are often
although this section refers mainly to CO2, it is necessary to
linked to the gas detection system, so the fans are
check for other gases. In a fermenting vessel or room, this is
only run when CO2 is detected, or less likely, high
normally limited to oxygen and, by implication, the nitrogen
oxygen levels, thus saving energy (particularly
level.
environmental heating). Therefore it is crucial that
Carbon Oxygen the ventilation equipment is kept in good working
dioxide order.

Long term 0.5 % Minimum Maximum Confined working space – vessel entry
exposure oxygen level level –
– 19 % 23.5 % Confined working spaces are areas not intended for
continuous occupancy and where there is a risk of serious
Short term 1.5 % Minimum Maximum personal injury from: Asphyxiation by gas (including CO2 &
exposure oxygen level level – nitrogen), flowing solids (e.g. grain), drowning, fire /
– 19 % 23.5 % explosion, unconsciousness from heat stress.

Learning Material 2016 67

Confined spaces also have limited access / egress making Vessel CIP
entry / exit difficult. In the event of emergency, rescuing is If using acid detergents and sterilants, it is not normally
therefore made more difficult. necessary to remove any residual CO2. However, if using
caustic based detergents exclusively:-
Beer fermentation / maturation vessels, and enclosed
rooms following a gas leak are classified as confined spaces. • it is necessary to ensure that the vessel has
sufficient ventilation to deal with any vacuum or
All confined space entry must be covered using a permit sudden expansion that might occur during the CIP.
system or robust Safe System of Work (SSoW).
or
• The confined space must only be entered if it is not
reasonably practicable to complete the task without • The vessel must be purged to remove CO2 before
entry, e.g. manual FV cleaning where no CIP exists. CIP.

• If entry must be made, a risk assessment is required,

with the key points detailed in a comprehensive Notes
SSoW. • Draw a diagram of the type of fermenting vessel
used in a plant that you are familiar with.
• Adequate emergency arrangements must be put in • How is fermentation temperature controlled?
place before entry. • Why was that type of vessel chosen?
• Describe the fermentation of a beer that you are
• The space should be ventilated to ensure the gases familiar with.
are maintained at safe levels. • Draw a graph of the fermentation profile including
• Collection temperature.
• The space must be tested for appropriate gas levels • Top heat temperature.
before entry. Personal monitors and emergency
• Duration of fermentation.
escape sets to be used at all times whilst inside
• What problems occur and what action is taken to
confined space.
resolve problem fermentations?
• Personnel working in the confined space should
wear a personal gas meter & escape set.

• The standby person must remain outside confined

space while person inside.

• The main role is to observe activities carried out

within confined space.

• If an emergency situation occurs, the standby man

raises alarm to summon assistance - first aid /
ambulance / rescue team – as identified in risk
assessment.

• The stand-by man must not enter confined space.

And finally, when the work is completed.

• Ensure the permit to enter is signed off.

68 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 69

Section 7 Yeast Management

7.1 Yeast propagation, storage and handling

Introduction

The yeast population grows by about five times during the Periodically, normally defined by the number of times the
fermentation process and a large proportion is cropped yeast has been re-pitched, the yeast is to be replaced with a
from the beer at the end of the fermentation. fresh batch of yeast grown from a single yeast cell (a new
culture).
The yeast crop has to be carefully looked after otherwise its
health and performance will deteriorate with each Brewing yeast must be cultured, cropped and stored in such
successive generation. a way to ensure:-

A healthy crop is maintained by aerating the wort, by • The use of the correct strain.
always selecting the best of the yeast crop for re-pitching
and in most breweries, by periodically generating a new • The consistency of the characteristics of the selected
pure yeast culture using specialised plant. strain, e.g. flocculation, metabolism, age
(generations).
Brewery yeast cycle
• Freedom from contamination by wild yeast, other
brewing yeasts and bacteria.

• High viability.

• The fermentation performance is “normal”.

• The yeast cropping is “normal”.

• Ensuring the yeast is fed OK (micro-nutrients,

oxygen).

Main processes involved in yeast handling

• Introduction of replacement yeast strains – yeast

propagation.
Yeast must be stored carefully under hygienic cold
conditions to keep it healthy and reduce the risk of growth • Addition to wort – yeast pitching.
of microbiological contamination.
• Separation from fermented wort (green beer) – yeast
Requirements of yeast handling cropping, including centrifugation and beer recovery
Yeast is the only living organism which should be found in from yeast slurries.
most beers (there are a few notable exceptions which are
not covered by these notes). • Storage of pitching yeast between brews.

At the start of the fermentation it has to be added and • If required, yeast sanitisation (acid washing).
mixed with wort which is at a suitable temperature for the
strain of yeast & style of beer, is sterile, and has been • Disposal of surplus yeast – waste yeast handling.
oxygenated or aerated sufficiently to allow the yeast to Excess yeast is typically sold on for yeast extract,
grow. health tablets, animal feed or the biochemicals
industry, though of course it may simply be sent to
At the end of fermentation sufficient yeast must be liquid effluent systems or landfill.
separated using hygienic processes from the fermented
wort (green beer), allowing the yeast to be re-pitched if • Effective cleaning and sterilisation of all yeast
necessary. The excess yeast (i.e. yeast not required for re- handling plant.
pitching) may be disposed of in a number of ways.

70 General Certificate in Brewing

Reasons for yeast propagation • Changes in nature (e.g. flocculation characteristics)
due to mutation.
Yeast is usually collected at the end of a brew for
subsequent re-use in the following brew(s). It is essential to • Changes in proportions of mixed strain yeasts.
use a supply of good healthy yeast in order to:-
The way that the yeast is cropped will often influence the
• Maintain consistently good fermentation degree of deterioration. Top cropping can be very
performance. selective, based on the condition of the yeast head at the
time of cropping, whilst bottom cropping is far less. For this
• Maintain consistent beer quality. reason lager breweries invariably operate yeast
propagation plants with frequent yeast propagation cycles.
• Ensure the economics are maintained. Increasing numbers of ale breweries now do as well.

The quality of pitching yeast can deteriorate for a number However, some brewers have used the “same” yeast for
of reasons, including:- years and have little idea of its provenance. Any
catastrophic failure in the past would have been accounted
• Contamination by bacteria. by another delivery from the same source. Typically, even
these breweries have backup in the form of dried or deep
• Contamination by other brewing yeast strains (e.g. an frozen cultures maintained at specialist culture centres.
ale yeast with a lager yeast used in the same
brewery). Pure yeast culturing procedures

• Storage for excessively long periods without re- In most modern breweries, to maintain the yeast purity and
pitching, allowing autolysis or general loss of viability. the consistency of fermentations, yeast is typically
propagated from a starter culture every 8 to 12
• “Contamination” with an enzyme used for “lite” beer generations. Propagation starts in the lab and continues in
fermentation. The yeast slurry is then not suitable special vessels with yeast count increasing between 5 and
for normal beers, as it almost certainly contains some 10 times at each stage. Finally the yeast is pitched directly
residual enzymatic activity, is liable to cause over into the fermentation vessel.
attenuation.
The principle of culturing yeast is to grow up a population
• If the yeast is required for production of light struck of yeast from a single yeast cell. Because of the way that
flavour resistant beers because it will be packaged in yeast multiplies (cells forming buds which break off and
clear glass bottles, the beer must only contain develop into new cells) each cell is a ‘clone’ of its parent.
suitable stabilized pre-isomerized hop extracts. The
slurry of “normal” beers contains normal hop isomers Consequently, a population grown from a single cell
from whole or pellet hops. “Contamination” with the consists of identical cells known as a ‘pure culture’. Yeast
normal hops are likely to lead to the development of only grows well when it is in the presence of the sister cells,
the undesirable light struck flavour in the beer, thus and so culturing is carried out in stages where the volume is
must be strictly avoided. However, it is possible to increased at each stage.
use yeast from a “light struck resistant” beer in non-
light struck resistant beers. The key guidelines for yeast propagation are as follows:-

• Changes in performance, e.g. sedimentation or • Stepped volume increase.

cropping characteristics, fermentation speed, growth
rate and mass, beer flavour changes. Yeasts do suffer • Stepped temperature decrease – avoidance of
increasing levels of contamination over time and it is temperature shocks.
usual to not keep yeast over 8 to 15 generations,
particularly in bottom cropping yeasts where the • Oxygenation / aeration level and method according
distinction between desirable and non-desirable to the step.
portions of the yeast mass is not easy to determine.
• Transfer to the next stage during the yeast growth
• Loss of fermentability – particularly maltotriose, one phase.
of the principal fermentable sugars.
• Avoidance of contamination by other yeasts or
• Yeast cropped from high gravity fermentations (circa bacteria.
8% +) is generally not considered suitable for re-
pitching as it tends to have reduced viability and
vitality, and so is best discarded.

Learning Material 2016 71

Yeast culture sequence The diagram illustrates a yeast propagation tank with
steam/cooling jackets. In this design, the air or oxygen is
The following diagram shows a typical lager culture injected into the culture through a long lance extending
sequence in a large brewery using cylindroconical vessels. through the spray head to the bottom of the tank. This
allows effective cleaning, (no shadows) and steam
sterilisation of the air injection lance and the vessel. Other
designs of oxygenation / aeration system use recirculation
loops or simple sinters in the base of the vessel.

Yeast propagation plant

Yeast culture plants typically have the following features:-

• Hygienic design and build, close to pharmaceutical The basic design of both small and large tanks is the same.
standards. The plant is steam sterilised prior to addition of wort. The
wort is re-boiled in the plant to ensure sterility. After
• Provision for sterilising the medium, usually wort cooling sterile air or oxygen is injected. The plant is then
boiling, though this is increasingly not required inoculated with a pure yeast culture. The yeast grows over
providing the quality of the CIP and sterilisation 1-2 days when it is transferred to the next stage. Following
sequences can be shown to be adequate and hot this stage the yeast culture is pitched into wort in a FV.
wort is transferred to the vessels. Note that in some modern systems, the quality of the CIP
and the incoming wort is such that the sterility of the
• Provision for very accurate cooling control.
cooled wort can be assured without steam sterilisation of
• Provision for intense aeration or oxygenation. the vessel or boiling the wort.

• Provision for efficient but gentle agitation to ensure The yeast mass requires vigorous oxygenation / aeration to
the yeast does not settle to the propagation tank increase the mass. The formation of alcohol is much lower
bottom. Some systems rely on the oxygenation / than in an anaerobic fermentation.
aeration system to achieve the rousing rather than
having a separate stirrer or recirculation system. Wort must have sufficient nutrients to build the required
• A number of tanks for the different stages, each one cell mass. Yeast must be fully viable and give a yeast count
being a larger volume than the previous one.

72 General Certificate in Brewing

at pitching as normal. Lower cell counts will lead to slower which may be considered unfit for blending back into the
fermentations and perhaps the need to blend away with main beer stream – with associated loss of revenue and an
beer from ‘normal’ fermentations. increase in effluent & disposal costs.

Each stage is carried out under sterile conditions thus The timing of yeast cropping is therefore to a large extent
ensuring contaminant free yeast. dependent upon the resistance of the yeast to autolyse
when in a settled mass. Cone cooling in itself is of little use
When the yeast population at each stage of propagation as the yeast is a very poor conductor of heat and will not
has grown and the wort proteins and fermentable sugars allow the centre of the yeast mass to be cooled.
have been depleted to the point where further growth is
about to be inhibited, the yeast and wort is transferred to Yeast removal processes
the next stage.
Yeast for re-pitching must be cropped only from
Yeast cropping – reasons & times fermentations which meet specification for attenuation
profile and diacetyl reduction. Wherever possible,
During the growth phase of fermentation the yeast microbiological status of fermentations should be available
population grows approximately five fold. This additional in time to prevent reuse of contaminated or cross-
yeast can be cropped and the best portions used for contaminated yeast.
pitching into subsequent brews. Yeasts of different strains
have different growth rates and this factor needs to be At the end of fermentation in a cylindroconical vessel, the
o
considered when selecting suitable pitching yeast. FV is typically cooled to around 4 C and the yeast settles
out. The first portion of cropped yeast contains break and
With top fermentations, the time of cropping can be used dead yeast cells and should go to waste / beer recovery.
to select the best yeast for re-pitching. For example the first
and last skimming can be discarded and the middle crop re- The next portion can be recovered if required for
used. Yeast selection like this has enabled some ale brewers subsequent re-pitching. Yeast can be stored as a slurry in
to maintain the same yeast strain for many years without beer or pressed to recover the beer, and then either stored
culturing. “dry”, as a cake, or re-slurried with water. Some breweries
store the yeast in the cones of the FV and pitch “cone to
With bottom fermentations, yeast selection is more cone”.
difficult, although selection of the most suitable yeast is
possible by careful cropping processes. For example, the Yeast can also be recovered from beer on transfer from FV
first purge from the cone can be discarded because it to MV using a centrifuge, though normally the yeast
contains trub and a large proportion of dead yeast, and the recovered is not used for re-pitching, but is sent to waste.
final purge discarded because it contains some dead cells This recovery process is discussed later.
and particularly low flocculence yeast.
Yeast cropping procedures must be optimised to target a
consistent ratio of yeast to liquid (beer) (% solids) as
possible.

The following storage conditions are important:-

• Low temperature, at say 2-4°C, with gentle agitation

of slurries to ensure the temperature is consistent.
Yeast deteriorates or autolyses when inactive, but
low temperatures slow this process down.

• Good hygiene. Micro-organisms will feed on the

medium surrounding the yeast. Contamination
during cropping or storage must be avoided.

• Time. Even in the best conditions, yeast will

deteriorate with time, so a storage limit of 2 to 5 days
is normally imposed.

Note that particularly with bottom cropping yeasts, if yeast Before yeast is re-pitched, it should be checked:-
is allowed to remain in a large mass without movement, the
yeast mass is liable to start autolysing, and heat up • The storage temperature must have remained
excessively. This will produce yeast of low viability and consistent.
vitality, and any beer recovered from the slurry is liable to
have distinct off flavours, typically described as “meaty”,

Learning Material 2016 73

 • The yeast must be free from microbial Centrifugation
contamination.
Centrifugation is a method of dramatically increasing the
• The yeast concentration, for instance, the number of rate of sedimentation, by artificially increasing the
cells per ml of slurry, or per gram of pressed yeast. gravitational force applied to the beer. This particularly
affects the rate of settlement of yeast, trub and large
• Yeast viability – (% live cells). compact protein particles.

There are two types of centrifuge used, disc bowl, and

Top fermenting yeast cropping – vacuum & parachute decanter, which both artificially increase the gravitation
system force, and particularly in the case of disc bowl centrifuges,
decrease the distance particles have to settle.

Decanter centrifuges tend to be used for separation of

larger particles such as trub from whirlpool residues, and
sometimes for beer recovery from yeast slurries.

Disc bowl centrifuges may be used to clarify green beer on

transfer from FV to MV and to remove solids from matured
beer immediately prior to filtration because they can
remove solids in seconds that would take weeks to settle
out naturally.

For a centrifuge to remove yeast and other particles, the

beer must have sufficient residence time in the machine for
Top fermenting yeast cropping – vacuum & overflow cells and flocs to fall through the path length under the
system applied “g” force. When smaller particle sizes are
considered, the flow rate through, the residence time, or
centrifuge speed become more critical.

Disc Bowl Centrifuges contain numerous conical discs plates

on which the deposited particles collect and then slide into
the solids holding area. They are spaced only a few
millimetres apart (compared to perhaps a few metres in a
tall cylindroconical vessel), so dramatically reducing the
distance the particles, particularly the yeast, have to travel
before settling out.

There are some drawbacks to the use of centrifuges that

must be considered when using them:-

• The beer may be subject to shearing, which can break

up suspended particles (typically protein) into smaller
particles, making subsequent clarification more
difficult. This is the main reason that centrifuges are
not used for recovering yeast to be used for re-
Bottom fermenting yeast cropping pitching.

• Beer temperature rises during the clarification.

• Unless well designed and maintained, the beer is

liable to pick up oxygen via leaking seals.

• Centrifuging is rarely sufficient to completely clarify

beer and is normally followed by filtration.

Beer must be kept separate from the atmosphere to

prevent oxygen pick-up by use of sophisticated seals.

74 General Certificate in Brewing

The rate of feed of beer into the centrifuge must be Decanter centrifuge
matched to the capacity of the machine and the solids load
in the beer. Usually, higher yeast counts are encountered at
the start and end of beer transfers. To allow the centrifuge
to handle the high yeast load, beer is fed to the centrifuge
slowly at first until a consistent feed is obtained. The
supply rate can then normally be increased. The supply rate
is often slowed towards the end of the transfer as yeast
slides off the cone walls.

Modern centrifuge discharge frequency, i.e. the removal of

settled yeast from the solids holding area, is controlled by
the turbidity of the beer being discharged, with time Separation takes place in a horizontal cylindrical bowl
overrides. The consistency of the supply beer solids equipped with a screw conveyor. The product is fed into the
content is improved by use of pre-centrifuge buffer tanks to bowl through a stationary inlet tube and is accelerated by
mix in “slugs” of high solids. an inlet rotor. Centrifugal forces cause sedimentation of the
solids on the wall of the bowl. The screw conveyor rotates
Infrequent discharge allows yeast cell damage to occur in the same direction as the bowl, but at a different speed,
(risking poorer beer quality and increased filtration thus scraping the solids off the wall and towards the conical
difficulty), whereas too frequent discharging increases end of the bowl. Separation takes place throughout the
losses. total length of the cylindrical part of the bowl, and the
clarified liquid leaves the bowl by flowing over adjustable
Flow through a disc bowl centrifuge plate dams into the casing. (Drawing courtesy of Flottweg,
description courtesy of Alfa Laval & Westfalia).

Beer Recovery

The yeast slurry skimmed off top fermentations or purged

from bottom fermentations contains around 50% usable
beer. Purges from maturation tanks may contain as much
as 80%. Many breweries have plants designed to recover
this beer, process it and return it to the mainstream
product.

The benefits of doing this are a reduction in beer losses

along with the avoidance of effluent charges from running
the waste beer to drain.

There are associated quality considerations because the

recovered beer may have a yeasty flavour and it may be
contaminated. However plant design and quality control
procedures can overcome these concerns.

The diagram below shows a beer recovery plant installed in

a large brewery.

Yeast Press
Yeast
slurry
from FV
Filter

Recovered Pasteurised
Beer Recovered
Beer

Purges
from MV Flash Pasteuriser

Centrifuge

Learning Material 2016 75

Monitoring yeast growth
Good practices for storage include:-
Methods for measuring yeast concentration or numbers • Maintaining the temperature at 2 – 4 °C.
include plate count, haemocytometer, turbidity, biomass
• Chilling to storage temperature rapidly.
measurement by electronic sensors (such as the Aber
Instruments yeast monitor), or more commonly for quick • Mixing to ensure homogeneous yeast slurries.
checks, the weight of yeast cells per unit of volume of liquid
slurry. The average weight of individual yeast cells varies • Avoiding aeration.
throughout the course of fermentation, and so using the
• Minimising storage times – 5 days maximum is a
weight to calculate the number of cells is not strictly
typical specification.
accurate, but discrepancy is slight and for most purposes
can be ignored. • Hygienic vessel and pipework design.

For less accurate determinations, it is convenient to • Efficient and effective CIP regimes.
measure the volume of packed yeast separated from a
• Thorough sampling & inspection regimes.
known volume (e.g. 15ml) of suspension in a calibrated
centrifuge tube.
Yeast pressing for storage
Another means of monitoring yeast growth is the
measurement of the specific gravity of the fermenting wort.
If the conditions are the same as previous fermentations,
including wort oxygenation, specific gravity vs. time, yeast
pitching rate, fermentation temperature profile, then the
yeast growth will be very similar to previous fermentations.
The chart below shows typical profiles of apparent specific
gravity and viable yeast mass during fermentation.

Yeast storage vessel

Yeast storage conditions

Yeast may be stored as a fairly dry cake of pressed yeast, in

a cold room. There are risks of cross contamination with
different generations of yeast, or with other yeast strains in
use, or contamination with bacteria. The stored yeast tends
to suffer from viability and vitality issues more rapidly than
slurried yeast.

Yeast is more commonly stored with the entrained beer

residues that it was cropped with, but sometimes may be
pressed and re-slurried with water. The vessels are either
individually cooled and insulated, or may be in a common
refrigerated room. The vessels must be fitted with low
shear mixers, and may be at atmospheric pressure, or
pressurised with sterile gas.

76 General Certificate in Brewing

7.2 Yeast selection, treatment & pitching Pitching yeast characteristics and assessment

Pitching yeast selection Pitching yeast has a number of key characteristics. A key
Pitching is the term used for adding yeast to the wort to one is the ability or otherwise to flocculate. The
start the fermentation. flocculation ability has greatly influenced the design of the
FV, and the cropping system associated with that FV. One
The choice of pitching yeast has a major influence on the definition of the flocculation characteristics is that of
performance of the fermentation and its outcome. The Gilliland, as follows:-
aims of selecting the correct pitching yeast are to:-
o C1 Permanently non flocculent - not commonly used
• Ferment the wort to the desired temperature and in breweries.
gravity profile.
o C2 Reversible loose flocs, head formers – used in top
• To achieve the desired flavour profile in the final cropping systems.
beer.
o C3 Reversible large, tight flocs – no head – typical
• To obtain sufficient healthy yeast for re-pitching, bottom cropping yeast.
typically
o Lager 15 – 20 million cells / ml o C4 Permanently flocculent, chain formers.
o Ales 5 – 15 million cells / ml

The criteria used to assess the suitability of a batch of yeast Yeast types are determined by a range of tests, including
include:- the following:-

• Is this the correct strain for the beer to be • Morphology – what it looks like under the
fermented? microscope.

• Is the yeast of the appropriate generation (i.e. less • The growth medium the yeast will grow in.
than the maximum specified generation, typically
somewhere between 8 and 12 generations)? • The flocculation characteristics.

• The previous history and fermentation performance • The fining ability.

of the yeast. Yeasts selected from a slow or sticking
• Heat resistance - autolysis due to heat.
fermentation are likely to repeat the problem.
• Fermentation by-products (e.g. esters, diacetyl).
• Growth rate / mass in previous fermentations.
• Whether spore forming or not.
• Is the yeast contaminated by any bacteria or wild
yeast? • DNA fingerprinting.

• Separation behaviour – was the flocculation true to

type?

• The previous wort gravity – very high gravity worts

commonly produce low viability / vitality / mutated
yeasts.

• Viability is ideally >95%, preferably >90%

• The storage time, temperature, etc.

Learning Material 2016 77

Acid washing Don’t
o
• Exceed 5 C at any time.
Bacterial contamination of brewer’s pitching yeast may lead
to undesirable off-flavours as well as potential increased • Treat (stand) for more than 2 hours.
levels of ATNC (nitrosamines) in the beer. It is therefore
good practice to minimise the numbers of bacteria in • Treat unhealthy yeast.
pitching yeast.
• Expect it to remove wild yeasts or mutated culture
This can be achieved by one of two methods:- yeasts.

• Very high standards of brewery hygiene to minimise • Store acid washed yeast.
pickup and growth of bacteria, associated normally
with regular introduction of fresh, contamination free • Use yeast from high gravity fermentations (> 8% ABV
yeast cultures, discarding contaminated (or ethanol). However, if all brewing is at high gravity,
potentially contaminated) yeast. the yeast slurry should be diluted with sterile water
prior to storage to reduce the effect on the yeast.
• Acid washing, normally with phosphoric acid, though
tartaric and citric acids have also been used. The acid washing tank (AWT) should be:-

Acid washing is the carefully controlled addition of an acid, • Insulated.

typically phosphoric acid, to the yeast and mixing
O
continuously at, typically, 2-4 C to prevent excessively low •
o
Temperature controlled 3 – 5 C.
and high pH portions of the slurry. The acid preferentially
destroys bacteria but the yeast remains relatively • Agitated.
unaffected. Acid washing will not destroy wild yeasts so
cannot be a substitute for good hygiene. Thus, in spite of • Calibrated.
regular acid washing, regular introduction of new pure
yeast cultures may still be required. • Large enough to contain all the yeast required to
pitch all the wort to be transferred into a single FV.
Acid washing may be carried out every pitching cycle, or as
determined necessary on an irregular basis due to high
• Only one AWT per FV should be used.
bacterial counts. Most breweries, if they carry it out, will
carry it out every cycle as it can be very difficult to
distinguish using microscope examination between low
Pitching methods
contamination levels and higher contamination levels, and
plating takes too long to be useful as a means of control.
Whichever pitching method is used, the systems must
ensure that:-
Do
• Ensure the yeast is adequately “diluted” in beer or
• Only the correct yeast strain is used.
water to allow good dispersion.
• The yeast is free from contamination.
• Use food grade acid, either phosphoric, citric or
tartaric acid.
• The appropriate pitch rate of viable and vital yeast is
o achieved.
• Chill the yeast slurry to < 4 C prior to addition of the
acid.
• The yeast is even dispersed throughout the wort in
the FV.
• Stir constantly whilst adding acid to eliminate
variation in pH, and regularly / constantly during
Dried yeast
stand.
Fresh quantities of dried yeast are used by many
microbrewers to pitch directly into the FV, and sometimes
• Ensure pH is in specification (typically 2.2 – 2.4)
by larger (international) brewers for either pitching directly
immediately after acid addition.
into FV or further growth in a propagation plant.
• Pitch as soon as stand complete.
In the case of microbrewers, typically the yeast is mixed
with a small quantity (a few litres) of warm wort or water
• Regularly check the yeast micro and viability both pre o
(commonly circa 25 C) and allowed to disperse evenly for
and post acid wash. 30 to 60 minutes, until no dried yeast “pellets” remain, and

78 General Certificate in Brewing

the yeast is starting to produce gas. The yeast slurry is then • FV utilisation is not considered efficient as yeast must
simply poured into the wort in the FV, and allowed to remain in cone until required, and excess can only be
ferment as required. removed after pitching complete.
• Process is complex due to need to dispose of trub and
In the case of the larger brewers, they will have their own dead cell portion at bottom of cone.
defined methods of “liquefying” the dried yeast, but the • Non ideal yeast storage – not stirred, so may have
basic principal of initial mixing as noted above remains. high levels of autolysis.
• Unable to acid wash effectively.
Recovered pressed yeast
Recovered yeast suitable for re-pitching may be pressed in Yeast pitching tank to FV
a sterile yeast press, and the yeast stored in trays in a Yeast from storage or propagation is pitched, in line into
refrigerated room, or less commonly, re-slurried the cooled oxygenated wort, or less commonly, directly into
immediately with sterile water and stored as slurry in sterile the FV.
refrigerated, stirred tanks.

If the yeast is stored as pressed yeast cake, it may simply be

weighed out and tipped into the FV whilst the wort is filling
the FV – a common method with older breweries with open
or covered square FVs.

If the yeast is re-slurried it may be acid washed or pitched

directly into the wort without washing.

FV cone to cone

• Additional capital and revenue costs.

• Yeast is normally transferred during wort transfer.
• Equipment used includes:-
o Positive displacement pumps for accurate
transfer of high viscosity slurry.
o Load cells on pitching or propagation vessels.
o Flow meters for simple volume measurement, or
o Mass flow meters for taking into account the
mass of yeast.
o Viable biomass meters (e.g. Aber) for measuring
viable yeast mass.
• Allows acid washing if required.
• Greater accuracy of pitching rate.
• This system has comparatively low capital costs – no • Improves FV utilisation.
separate yeast tanks and mains.
• Yeast may be transferred before or after wort
transfer. Pitching rate calculations
• The lack of additional tanks and mains means there is
comparatively low risk of contamination pickup as Typical pitching rates are
the mains, pump and meter systems can be sterilised
without breaking joints etc. • Lager 15 – 20 million cells / ml
• Equipment used includes:- • Ales 5 – 15 million cells / ml
o Positive displacement pumps for accurate
transfer of high viscosity slurry.
o Flow meters for simple volume measurement, or Pitching yeast is checked before use for viability &
o Mass flow meters for taking into account the contamination.
mass of yeast.
o Viable biomass meters (e.g. Aber yeast monitor) • Only viable yeast will ferment wort, so the mass of
for measuring viable yeast mass. non viable yeast cells only must be accounted for.
o Turbidity meters etc. used with simple flow rate
measurement to guard against yeast running out.
• If pitching is carried out on a weight basis the
• If suitable instruments are not used, then the pitching proportion of entrained beer must be accounted for.
rate control can be poor due to variability in yeast
slurry consistency.

Learning Material 2016 79

The viability is normally checked by mixing thin yeast slurry • The yeast slurry to be used contains 65% solids (as
with methylene blue stain. The viable cells metabolise the dye determined by laboratory test)
to colourless compounds. Dead cells are stained blue. It is
assumed under normal brewery conditions that the yeast • 96% viable yeast (methylene blue)
vitality is 100%, though the variation in required pitching rates
of different yeasts will allow for any consistent reduction. It is
not good practice to use yeast that has a viability of < 90%. The mass of yeast to be pitched = (500 x 0.7) x 100 x 100
(65 x 96)
To assess the solids content of yeast slurry, a small portion is
spun down in a laboratory centrifuge. = (500 x 0.7)
(0.65 x 0.96)
These two factors can then be used to calculate the mass or
volume of slurry that has to be pitched into a specified volume = 560kg
of wort to enable its subsequent fermentation to the required
specification.
Yeast as a co-product.
Normally, rather than convert back to cells / ml or wort, the
calculation keeps to a more practical level, for example, kg With an increase in the yeast stock with each fermentation, a
yeast / hl wort. For example, the standard pitch rate for a surplus is inevitable. Yeast is rich in vitamin B and is very
lager wort is defined thus:- flavoursome after processing so it is commonly sold as a co-
product to food manufacturers or to pharmaceutical
• Wort is to be pitched with 0.7 kg pressed yeast per hl. companies.

• Actual volume of wort to be pitched is 500 hL Alternatively, surplus yeast can be used as a food for livestock.

80 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 81

Section 8 Beer Maturation and Cold Storage

Introduction

The biochemical, chemical and physical mechanisms • Many particles in suspension, mainly yeast, which
involved in flavour changes occurring during maturation are make it cloudy or turbid.
intricate and complex. Maturation includes all
transformations between the end of primary fermentation • Constituents which have the potential to make the
#
and the final filtration of the beer . Classically fermentation beer go cloudy after packaging, known as haze
and maturation are considered separate steps in brewing precursors.
but in practice there is significant overlap.
• Usually, lower levels of carbon dioxide than those
The main difference between traditional maturation specified for the final product.
systems in ale and lager brewing is that ales are
conditioned by warm storage, holding the beer at 12 - 18°C, The “off” flavours are largely result of poor yeast growth
whilst lagers are conditioned at much lower temperatures due to poor oxidation, yeast viability or vitality,
(3 - 6°C). There are, of course, always exceptions to this temperature, nutrient status etc. The vicinal diketones,
traditional view. hydrogen sulphide and acetaldehyde are primarily
responsible for “green beer” flavour and an important
Under warm maturation conditions, residual sugars are feature of maturation is adjustment of their concentration.
rapidly metabolized and removal of “green” flavours is The adjustment (normally a considerable reduction) is
completed in 1-2 weeks (normally far less) depending on primarily completed by the remaining yeast, which acts to
the type of beer, yeast strain, wort composition and reduce the “green beer” flavours.
primary fermentation conditions.
During the maturation period, VDK (principally diacetyl) is
Maturation of lagers, particularly at low temperature, is reduced by the yeast to acetoin and 2,3 butanediol. Both of
significantly dependent upon the length of the lagering these compounds have far higher taste thresholds than
(ageing) period, the amount of yeast in suspension and the diacetyl and do not contribute adverse flavours to beer.
quantity of fermentable sugar in the young beer or added in The rate of diacetyl removal is temperature dependent, the
the form of actively fermenting wort (kräusening). rate being much higher at higher temperatures and higher
yeast concentrations – hence the increase in temperature
Brewery conditioned and filtered beers, i.e. most keg, can at the end of fermentation during some lager
and bottle beers, are matured in tanks where flavours fermentations. Because the rate is dependent on the
improve, the yeast is sedimented out (so aiding filtration), temperature and viable yeast cell concentration,
the beer is stabilised to ensure that it stays bright, and maturation takes place before chilling of the beer and
oxygen is purged / mopped up by the yeast to very low sedimentation of the yeast.
levels.
The removal of aldehydes is favoured by:-
#
Cask and bottle conditioned beers are matured in cask or
• Measures to promote vigorous secondary
bottle and are unfiltered. Here, the yeast settles out,
fermentation & maturation.
sometimes assisted by use of finings, flavour is improved
and CO2 levels are increased. • Higher temperature maturation.

• High yeast concentration during warm maturation.

8.1 Warm maturation
Hydrogen sulphide is very volatile, and much is removed by
the stripping effect of CO2 during late fermentation and
The purpose of warm maturation, and beer flavour
early warm maturation, particularly in shallow vessels.
changes post-fermentation

Beer at the completion of primary fermentation, sometimes

termed ‘green beer’, contains:-

• Unpleasant flavour compounds, for example –

acetaldehyde (green apples) and sulphur compounds
(bad eggs) and vicinal diketones (VDK’s) such as
diacetyl (rancid butter, butterscotch).

82 General Certificate in Brewing

During this maturation, the levels of carbon dioxide Vertical maturation tanks in a cold room
dissolved in the beer will increase, especially if the beer is
held under pressure. The evolution of CO2 bubbles will also
help to purge out any unwanted substances like oxygen or
unpleasant flavour compounds, though the effectiveness of
the CO2 “purge” is doubtful.

Typical times & temperatures

Ales are typically held at 12 – 18°C for 1 to 4 days, though

may be up to a week.

Lagers are typically held at 3 to 6°C for 4 days up to a few

weeks. Sometimes the warm maturation process involves a
slow reduction in temperature over a period of days or
even weeks, rather than a single rapid cool. There may Tanks have no cooling or lagging. Kept in refrigerated room.
even be a temperature rise towards the end of For best results, the beer is cooled on transfer to the vessel
o
fermentation for diacetyl removal followed by gradual to -1 C.
cooling to 0°C or below.
Horizontal maturation tanks in a cold room
Maturation systems

There are different types of maturation system. In a uni-

tank system, beer is matured in the same tank that it was
fermented in (FV). In a dual tank system, the beer is
transferred into a maturation tank (MV) and either cooled
in that tank or more usually, is chilled on transfer into the
tank. Some brewers use a three tank system, using a
fermenter, a warm maturation tank followed then by a cold
conditioning tank.

Maturation tanks can be cooled by external jackets or they

can be sited in a cold room as illustrated in the diagrams
below:-

Vertical maturation tanks with side wall and cone

Tanks have no cooling or lagging. Kept in refrigerated
cooling
room. For best results, the beer is cooled on transfer to
o
the vessel to -1 C.

8.2 Cold storage & stabilization

The purpose of cold storage

Improvements in beer flavour are achieved in two stages,

warm maturation and cold storage. Yeast must be present
for the improvements to occur. Cold storage takes place at
0°C or below and beer flavour continues to improve as the
unpleasant compounds are reduced, though the rate of
reduction is very much slower than at warm maturation
Each tank is individually cooled and lagged. temperatures.

May be used as uni-tanks or dual purpose, or as pure The raw materials from which beer is made, especially malt,
cold store vessel. contain protein material and tannins, which can combine
together to form particles large enough to create hazes.
This haze is termed non-biological haze because it is not
When used as non uni-tank MV, for best results, the caused by microbiological activity.
o
beer is cooled on transfer to the vessel to -1 C.

Learning Material 2016 83

Non-biological haze can also be formed after filtration and cold storage and takes around 12 to 36 hours to form.
packaging especially as the beer ages and in the presence of However the bonds are very fragile and almost instantly
oxygen. A ‘chill haze’ can be formed if inadequately break if the beer is warmed up.
stabilized beer is stored in a cold place like a refrigerator
because the remaining haze particles are less soluble at low Particles, for example yeast and insoluble protein particles,
temperature. will sediment out as long as they are heavier than the beer.
The rate of clarification depends on the size of the particles,
Other functions of cold storage include:- how dense the particles are and how far they have to fall.

• Oxygen reduction – by allowing residual yeast to The simplest but lengthiest way of removing the yeast and
mop up oxygen. haze particles remaining in the beer is to allow suspended
matter to settle. Stoke’s Law tells us the essential features
• Carbonation - by action of the residual yeast on of settling, namely that the rate of sedimentation is
increased by:-
any fermentable sugars, producing CO2.
• Increasing the diameter of particles.
• Stock holding – providing a buffer for periods of
high demand. • Increasing the density of particles.

• Blending – to improve consistency of final flavour • Increasing the gravitational force.

etc. Ideally to be a routine operation, rather than
• Decreasing the liquid viscosity.
as a need to bring out of specification beer into
specification. • Decreasing the distance the particles must settle.

• Process aid reaction time – to allow sufficient time Thus:-

for reactions and settlement to take place. • Larger particles settle very much quicker (the rate
increases by the particle diameter squared). The
Typical times & temperatures means of doing this are described under finings
o
Ales typically -1 C for 1 to 4 days, though may be up to a • Denser particles settle more rapidly.
week, particularly for small pack beers. Shorter residence
times are most easily obtainable when using beer stabilisers • Liquids that are less dense and less viscous permit
such as silica gels or PVPP. more rapid settling.

o
Lagers -1 C for 4 days up to a few weeks, particularly • Shallow vessels rather than deep vessels encourage
dependent upon the origins of the beer. Traditional style more rapid settling.
beers are more likely to use longer times than modern
• Increasing gravitational force (by centrifuging)
recipes. Again, shorter residence times are most easily
achieves rapid settling.
obtainable when using beer stabilisers such as silica gels or
PVPP (where permitted). • Decreasing liquid viscosity. However, this is not a
practical option, since this means allowing the beer to
General principles of stabilization warm up, which would allow potential haze material
to re-dissolve (the decrease in viscosity is minimal
On transfer from FV (or MV) to cold maturation/storage anyway).
vessel, the beer contains high levels of suspended solids,
mainly of yeast and proteins. However, it also contains The factors that the brewer can influence that will have the
large amounts of protein and polyphenol precursors. These greatest effect on time to clarify are:
need to be largely removed before filtration to allow
efficient filtration and the required shelf life. The period of • Particle diameter, which can be increased by causing
cold maturation allows much of the suspended yeast and particles to agglomerate, for instance by the use of
proteins to settle out. The settlement / removal may be finings.
aided by use of centrifuges (see section 7 – yeast handling)
or processing aids, as described later in this topic. • Gravitational force, which can be increased by
centrifugation.
o
At 0 to -2 C there is little yeast activity (although lager yeast
can grow very slowly at this temperature). The principal Haze precursors and their removal
changes are physical. Beer haze is formed during cold
The most common hazes are derived from protein
storage due to the combination of proteins and
fractions, chiefly polypeptides derived from the malt
polyphenols, which either settle out in the storage tank or
protein.
are removed during filtration. This occurs principally during

84 General Certificate in Brewing

The polypeptide material may be polymerised to form • Using adjuncts which are low or free from nitrogen
visible haze particles by polyphenols or tannins, also e.g. maize flakes or brewing syrups.
derived from malt (but also possibly from hops). These
polyphenols easily oxidise to become highly reactive so that • Using under-modified malts thereby reducing the
the level of dissolved oxygen in the beer is important in this amount of protein extracted.
context. Heavy metals (such as iron and copper, from
• Promoting proteolytic action during mashing
untreated brewing water) are also important as they link
where necessary, such as stands in the range 45-
oxidised polyphenols and polypeptides.
55°C.
Thus the building up of visible haze particles is particularly • Adding additional enzymes – proteases or
rapid in the presence of dissolved oxygen and / or heavy glucanases to the mash.
metals.
• In the brewhouse, efficient separation and
When beer from the primary fermenter is chilled to 0°C, it removal of proteins with the spent grains and as
usually becomes hazy due to the precipitation of material hot or cold break after wort boiling, during cooling.
which typically is mainly a complex of protein and The efficiency of separation will depend on the
polyphenols plus a small amount of inorganic substances. quality of wort, and where appropriate mash
boiling, boiling, and performance of the whirlpool.
When beer is warmed, the bulk of the haze disappears. The
• Improving the hot and cold breaks by use of kettle
portion of haze that has re-dissolved is called chill haze.
finings and if necessary appropriate hops / hop
The beer may be subject to a succession of alternating
materials. Some hop extracts contain little or no
periods (through transport and warehousing) of chilling and
polyphenol. The presence of the vegetable matter
warming, with the beer becoming hazy and then clearing
in whole or pellet hops also helps produce a more
again. Gradually, however, the haze formation ceases to be
compact trub and clearer wort.
reversible. That which is stable at 20°C is called permanent
haze. Typical ways of reducing the polyphenol content in beer
are:-
Chill haze represents such reversible association, the
material coming out of solution because of the decreased • The use of adjuncts to dilute the amount of
solubility at low temperature. Permanent haze is the polyphenols coming from the malt.
irreversible association, characterised by the more durable
covalent linkages. • Reducing the extraction of malt polyphenols by
avoiding running to a low gravity (less than 1004 or
0
Not all hazes are associated with protein and tannins. 1 plato) and keeping the sparge pH low (below 7)
Other hazes include those from:- (most malt polyphenols are extracted towards the
end of the runoff).
• calcium oxalate crystals, although these are unlikely if
there is excess calcium present during wort • Brewing with proanthocyanidin free malt, which is
production, particularly during the mashing process. now commercially available. (“Pro-ant” malt – bred
to be free of proanthocyanidins, the most reactive
• carbohydrates, especially β-glucan material, and less of polyphenol which, in beer, is derived 70-80%
commonly, residual unconverted starch. from malt, the rest from hops).
• filter powders (e.g. kieselguhr) or cellulose fibres
Other precautions include:-
which have passed through the filter systems.
• collapsed foam particles. Poor beer handling or over • Ensuring adequate levels of calcium ions in the mash
carbonation, particularly when using reduced hop and wort boil to ensure oxalates and phosphates
compounds, can result in particulates due to which can form haze are precipitated.
collapsed foam floating in the beer.
• Avoiding contamination of water and raw materials
• undissolved propylene glycol alginate foam enhancer
by heavy metals and avoiding their introduction from
(PGA) if used.
materials of construction of equipment.
To produce stable beer, it is also necessary to ensure the
• Removing any brown scum which appears during
other processes associated with beer brewing and fermentation (only realistic with suitable top
packaging minimise the risk of producing hazes. fermenting operations).
Typical ways of reducing the protein content of a beer are:- • Ensuring strong yeast growth. New cells adsorb
protein – polyphenol complexes onto their surfaces.
• Selecting low nitrogen malts (typically 1.6 to 1.8%
nitrogen), to give comparatively low nitrogen
worts.

Learning Material 2016 85

 • Reducing the dissolved oxygen content of the beer used. Usage rates need to be optimised both to ensure
post fermentation by carefully processing and economic cost is achieved and in order to gain the best
possibly the use of reducing agents (e.g. SO2 plus possible results. Over fining can cause hazes just as under
ascorbic acid – though these are increasing less fining can leave hazes.
widely used) or the enzyme glucose oxidase.
Auxiliary finings
• Keeping beer free of dissolved oxygen and heavy There are a number of different types of auxiliary finings.
metals in packaging. The most common is based on acidified silicates.
• Holding packaged beer in cold store. Polysaccharides (gums such as acacia, gum arabic) and
seaweed extracts - finings based on carrageenan or
alginates (carbohydrates from seaweed) and blends of part
THE NATURE & ACTION OF STABILIZING AGENTS silicate/part polysaccharide finings are also available.

Introduction Isinglass finings

Stabilisation, other than enhanced removal of yeast by Isinglass finings are made from the swim bladder of specific
centrifugation, or yeast and protein by long, cold storage types of tropical and subtropical estuarine fish. This
time to allow settlement, may be improved by a number of contains high levels of a protein called collagen which
methods. makes the yeast cells clump together by an electrostatic
effect.
Other than the use of long cold storage periods, the use of
finings is perhaps the most traditional method of reducing Proteins removal
storage times and increase beer clarity and shelf life.
Comparative recent stabilisation methods are aimed at Adsorbents – silica gels
reduction of the protein or the polyphenols which comprise Silica gels (acidified sodium silicate) remove proteins by
chill and permanent haze. adsorption into pores within the gel structure. The size of
the pores can be used selectively to remove proteins in
Finings terms of their molecular size (molecular weight). Silica gels
are not strictly additives because they are removed during
Finings act like electrostatic “glue” having the effect of filtration.
increasing the diameter of haze particles, so that in
accordance with Stoke’s law, the particles will settle more Hydrogels contain up to 60% w/w moisture and are easily
rapidly. Brewers may use two different kinds of finings – handled, quick dispersing and fast settling, whereas
auxiliary and isinglass finings on transfer from FV to MV. xerogels (with less than 10% w/w moisture) are more
adsorbent, but are more expensive and more difficult to
The use of the correct balance of auxiliary and isinglass handle due to the very low bulk density.
finings will rapidly clarify a beer containing:-
Silica gels are readily removed as tank sediments or at
• 0.5 to 2.0 million viable yeast cells per ml. filtration. Hydrogels can also be used as filter body feed.
• 1 to 3 million non-biological particles (mainly
Dosing rates are typically 40 – 60 g / hl on transfer from FV
protein) per ml.
to MV, and 40 to 100 g / hl when added at filtration, though
Finings systems will not adequately remove:- generally at the lower end of this range for domestic beers.
• Colloidal hazes caused by metallic contamination. Bentonite
• Bacterial contaminations. Bentonite (an aluminium silicate derived from certain clays)
• Dead yeast cells. is now rarely used for protein stabilisation in beer (although
• Wild yeasts. may still be used in winemaking as a protein adsorbent).
• Beers with particle loadings much higher or lower
than the optimum. Tannic acid
Tannic acid itself can precipitate protein but tends to
There are three principle objectives of beer fining:- produce a lot of loose solid matter which adversely affects
• Bright beer – important with unfiltered beer. losses. It is now rarely used because of this problem.
• Rapid speed of fining. Typical dosage rates are 5 to 8 g / hl of beer. Reaction time
• Tight and minimal cask bottoms. is 5 – 10 minutes, but the settlement time can be days.

The emphasis that any particular brewer will place on these Proteolytic enzymes
objectives will determine his assessment of the best type of Proteolytic enzymes such as papain, extracted from sap of
auxiliary and the optimum usage rate. This is especially the papaya plant, hydrolyse proteins, i.e. break them down
important when the beer is not going to be filtered i.e. for into smaller compounds which will not produce hazes. It is
cask conditioned. dosed typically at 2 to 6 ml / hl of beer.

Finings optimisation should be carried out on a regular It may be added on transfer from FV to MV though is not
basis, and certainly when the new season’s malt starts to be common nowadays as it is less effective than adding later at

86 General Certificate in Brewing

filtration, when there is less protein left in suspension for Dosing rates are typically 10 – 40 g / hl on transfer from FV
the enzyme to act on. It is more commonly added during to MV, and 20 to 70 g / hl when added at filtration as a
the filtration process, typically as part of the pre-filtration single use material or recovered material. Re-use PVPP is
additions, where the activity is carried through to bright considerably more expensive than single use PVPP, but the
beer and final packaging process. Most enzyme activity will additional cost of both material, recovery system and
occur during the warm up phase of tunnel pasteurisation regeneration chemicals etc. is outweighed by the reduced
O
(optimum circa 50 C), because cold storage temperature is usage.
too low. It is far less effective when beer is flash
pasteurised because the warm period during which the Combination treatment
enzyme is active is too short. It is liable to remain active if There is often a synergistic effect when removing both
the beer has been subjected to less than 20 PUs. The protein and polyphenol. To achieve this, the beer may be
denatured enzyme stays in solution in the final product. treated with silica hydrogel on transfer to maturation
Beer foam proteins may be adversely affected by other vessel, or at the infeed to the filter, and treated with PVPP
enzymes in the 'enzyme' preparation. after filtration. This double treatment can produce a beer
which is haze stable up to 18 months.
Polyphenol reduction

PVPP Notes
Polyvinyl polypyrrolidone (PVPP) is a nylon derivative and Describe the maturation process in a plant that you are
acts as a synthetic protein and is used to remove familiar with.
polyphenols and polyphenol-protein complexes. • How long is the cold storage?
• What agents (process aids) are added to the beer
PVPP is expensive and can be used either as single use (by to improve its stability?
addition to maturation/ cold storage tank, or dosed in on • What additional ingredients are added to your beer
transfer to filter and trapped on a filter mixed with the during processing?
kieselguhr), or it can be used in a stand-alone recovery filter • Where are they added and what are the rates of
(where the PVPP slurry is dosed in-line to bright beer after addition?
kieselguhr (KG/DE) filtration, and then trapped on a second
filter. The powder is then regenerated by hot caustic
°
solution (1 – 2 % at 80 C), neutralised and then recovered
for re-use.

Learning Material 2016 87

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

88 General Certificate in Brewing

Section 9 Bright Beer Preparation

Candidates should follow, and will be examined on,

either section 9A or 9B.

SECTION 9A – BRIGHT BEER PREPARATION

(MAINSTREAM BREWERY)

9.1. Chilling and Carbonation

The figure below shows the temperature profile in a beer
Beer Chilling chiller arranged to have co-current flows. Beer at +5°C and
coolant, for example glycol, at -5°C, are shown as entering
The final stage of beer maturation, prior to filtration and at the ‘Left-hand’ side of the diagram. The ‘red’ line
packaging, is cold storage, usually at less than 0°C and denotes the metal heat exchanger plate skin temperature,
usually for several days (see section 8). The most efficient which in this case reaches a minimum of –2.3°C and so
way to chill beer to low temperatures is to use a heat would not cause the beer to freeze.
exchanger, either on transfer from FV to MV, or if uni-
tanking, by recirculating through a heat exchanger. Most Temperature profiles in a co-current beer chiller
breweries use plate type heat exchangers (PHE) using glycol
or brine as the refrigerant, but some use shell and tube
types, using ammonia, glycol or brine.

Section 4 of the GCB notes describes how wort can be

cooled using a plate heat exchanger. The flow patterns
through a heat exchanger can be either counter-current or
co-current.

In the previous example of a wort cooler, counter-current

heat exchange is used. This is where the two fluids flow in
opposite directions to each other, separated by thin
stainless steel plates, i.e. the hot wort inlet is adjacent to
the hot water outlet. Such an arrangement is used to obtain
good recovery of heat and to minimise refrigeration loads.
By comparison, the next figure shows the same cooling duty
The alternative PHE flow arrangement is co-current where if the beer and coolant flows were in a simple counter
the two fluids flow in the same direction. In the case of the current arrangement. Again, beer is shown as entering the
wort cooler, this arrangement would fail to give adequate heat exchanger at the ‘left-hand’ side of the diagram, but
recovery of heat and consequently would place an being counter current, this is the position at which the
unnecessary burden on the refrigeration plant. However a coolant leaves the heat exchanger. This means that the
co-current heat exchanger is suitable for chilling beer by coldest coolant would be directly next to the beer at its
o
only a few degrees, from say 4 C to less than 0 °C, as there coldest.
is reduced risk of freezing the beer in the heat exchanger.
Temperature profiles in a counter current beer chiller
The beer is cooled to close to its freezing point (typically –
o
1.0 to –2.0 C, depending on the alcohol content) in a heat
exchanger, the temperature change coming from the use of
secondary refrigerant, such as propylene glycol solution, as
o
the coolant, at approximately -4 C.

In this way, passing beer through the heat exchanger will

safely chill the beer to just above the freezing point of the
beer.

The operating principle of a co-current beer PHE:-

Learning Material 2016 89

In this case, the minimum skin temperature is –3.6 °C which Cross section of plates and counter-current flow:-
is below the freezing point of most beers. With such an
arrangement, there is a severe risk of freezing occurring.

Modern beer plate heat exchangers often use a

recirculating loop of glycol (or other cooling medium) with
small quantities of fresh glycol being fed into the system,
Co-current PHE with partially recirculated coolant for
displacing the equivalent volume of warmer glycol. This
improved temperature control.
reduces the temperature difference between the glycol and
the beer, so reducing risk of freeze ups. Such recirculating
glycol systems may be configured as co-current, or counter-
current systems.

Plate Heat Exchanger (PHE) Design

The plate heat exchanger is by far the most widespread

type of heat exchanger in the beverage industries. For
brewery applications, a stainless steel frame is often
preferred to the coated steel frames for reasons of hygiene,
maintenance and appearance.

The PHE comprises a collection of plates assembled within a

frame. The two process fluids flow in the spaces between
the plates and are distributed along the length of the heat Shell and tube heat exchangers
exchanger by means of circular passages cut into the
corners of the plates. The flow channels between the plates Two fluids, with different supply temperatures (in this case
and the distribution passages are sealed by a gasket fixed to beer and the coolant, typically glycol, brine or ammonia)
the face of each plate. A seal is made between the gasket flow through the heat exchanger. The beer flows through
and the reverse face of the adjacent plate. the tubes (the tube side) and the other flows outside the
tubes but inside the shell (the shell side). Heat is
There is a high degree of turbulence in the fluids flowing in transferred from the beer to the coolant through the tube
the narrow passages, created by the high velocities and the walls. In order to transfer heat efficiently, a large heat
pattern embossed into the plates. Very good heat transfer transfer area is used, leading to the use of many tubes.
and a degree of ‘self-cleaning’ are achieved under these
conditions. There are a number of different configurations of shell &
tube heat exchangers. The following is shown to give the
Example of flows through a counter current PHE:- basic principle of such a heat exchanger.

Good flow rate across

plate surface

90 General Certificate in Brewing

Carbonation injected in the low pressure zone in the venturi and the gas
dissolves when, because of the increase in the pipe
The purpose of carbonation is to increase the level of CO2 diameter, the pressure increases and the flow velocity
dissolved in the beer to the required level for the next stage reduces.
of the process.

This is normally determined by the customer palate, and

the beer foam required when poured correctly, but the
CO2
package types may also impose limitations, e.g. if beer CO2
is too high, then the cans may be damaged during
pasteurisation or bottle explode in a pasteuriser; if too low,
cans may not be pressurised sufficiently to withstand
secondary packaging and transport without damage.

Normally, carbonation is left as late during the beer

production process as possible because it improves the
accuracy and consistency of the final in package CO2
content. Where high gravity brewing is practiced, the
deaerated dilution liquor normally has quite a low CO2 Venturiisformed
Venturi formedbybyflattening
reducing athe
section
cross of 100 mm
sectional diaofpipe.
area pipe.
content, and carbonation has to be carried out post Lowpressure
Low pressurezone
zonecreated
createdatatpoint
pointofofmaximum
maximum velocity.& velocity.
restriction
dilution. Gasinjected
Gas injectedinto
intothis
thislow
lowpressure
pressurezone.
zone.
Absorptionoccurs
Absorption occursasasthethearea
pressure is recovered
increases, as the
the velocity decreases and
areapressure
the increases and velocity decreases.
rebuilds.
Carbonation is typically measured using one of two units;
the first being the metric grams of CO2 per litre of beer (g/l),
the second being the more traditional volume of CO2 per The venturi is made, for example, from a section of 100 mm
volume of beer (vol/vol, or vols). diameter pipe that has been reduced to say 40 mm, with a
section having a reduced flow area. As beer passes through
The following ranges are examples of CO2 (in g/l) content of the venturi, the velocity increases and there is a
beer in final package:- corresponding decrease in pressure. Carbon dioxide is
injected into the beer at this low pressure zone. Absorption
• Keg lager 4.3 – 4.9 is aided by the high degree of turbulence in this zone and
by the increase in pressure in the diffuser section
• Keg ale 2.8 – 3.2 immediately afterwards. In this section, the cross sectional
2.0 – 2.4 (nitro keg) area increases, with a consequent reduction in velocity and
increase in pressure.
• Bottle & can lager 4.8 – 5.4
(b) Sintered diffusers
• Cask ale 1.7 – 2.3 Sintering is a process where metal or ceramic particles are
pressed into a shape then heated to just below their fusion
The process of dissolving a gas in a liquid (such as carbon point. Partial fusion takes place to give a mechanically
dioxide in beer) is helped by a number of factors:- strong yet porous material. For gas diffusion, the sintered
material is made into a cylindrical shape, often referred to
• Solubility is increased at low temperatures. as a ‘candle’. The effect of passing gas through the candle
immersed in a liquid is the formation of a very many fine
• Solubility is favoured by high pressure. bubbles. Fine bubbles are absorbed readily by the beer.

• Solubility is favoured by a fine dispersal of gas as (c) Nozzles

micro-bubbles which give a very high surface area Many breweries still prefer the simplicity of a simple
/ volume ratio for rapid solution of the gases. injection nozzle for carbonation. The gas is forced through
a fine hole at the end of a nozzle and the result is a fine
Generally all 3 factors are observed when designing a stream of bubbles in the liquid. Nozzles have an advantage
carbonation facility of which there are several designs, such over sintered diffusers in that they are more easily cleaned.
as:-
Location of Carbon Dioxide Injection Points
(a) Venturi carbonator
The following is a diagram showing the changes in velocity Typically, carbonation is carried out either prior to filtration,
and pressure through a venturi carbonator. The gas is or if after filtration, immediately after dilution to sales
gravity (if high gravity brewing is practiced). Many older
breweries still carbonate on transfer between FV and MV,

Learning Material 2016 91

to reduce the work load of the filtration areas carbonator Modern systems also measure the actual addition rate to
and improve the accuracy of the final carbonation unit in give a calculated CO2 value and compare this to the
the filter area. It is also possible with modern control measured value to ensure the control system is working.
systems to adjust CO2 levels at the infeed to a packaging
machine, for example, immediately prior to the flash Automatically controlled carbonation system
pasteuriser of a keg filler.

In selecting the point in the process at which to inject gas,

consideration is given to the factors that promote gas
absorption, i.e. low temperature and high pressure.

Often a static mixer is incorporated after the injection point

to create turbulence and so aid solution.

For carbonating beer, the selection of an injection point is

dependent upon the ability of the injection system to
dissolve the gas fully. For example, if injection is made
immediately before a beer chiller, the turbulence through
the chiller will increase the transfer rate and the drop in
temperature that occurs through the chiller will also help
gas solution. Thus it is less necessary to have a very fine
stream of gas bubbles produced by the injector. If the
9.2 Beer Filtration
injector is after the chiller, then the gas bubbles need to be
much finer, to ensure rapid solution by ensuring a high
surface are to volume ratio of each gas bubble. Consumers have come to expect visually clear beer, free of
haze.
The figure below shows the arrangement for a typical
carbonation point. Note that this particular arrangement is Beer that is intended to be clear (bright) is often assumed
fitted with a sterile filter and a steam sterilisation/CIP to be of better quality and there is much historical evidence
connection. Although this may not be considered necessary to prove that this is often true. However, unfiltered,
for gas derived from cryogenic storage or of certified intentionally cloudy beer, including wheat beer, is still
quality, it is necessary to ensure that no microbiological produced and enjoyed in many countries.
growth can develop in the injection system itself.
Matured beer will still have particles in suspension, mainly
Note also that a sight glass is usually included (though not yeast but also smaller particles, mainly protein, unless it has
shown here). This gives a visual check on the gas injection. been fined. There are three types of filtration:-

Manually controlled carbonation system The purpose of ‘rough’ filtration is to remove all the
particles that would make the beer cloudy.

The purpose of ‘polishing’ filtration is to remove all yeast

and bacteria so that the beer is sterile.

The purpose of ‘stabilising’ filtration is to prevent non-

biological haze formation in package, which is the haze
formed by the protein/tannin particles described in Section
9.1.

Traditionally, beer has been filtered using filter aids,

predominantly kieselguhr (KG). More recently however,
new filter aids that are capable of being regenerated have
been developed. These reduce powder purchase costs,
waste disposal and improve safety aspects, albeit at the
The next figure shows a system for carbonation where the additional cost of a regeneration process. However, the
gas flow is controlled automatically by means of a CO2 in- underlying physical principles by which beer is filtered
line sensor, the signal from which is used to vary the gas remains the same as with KG.
flow by a standard process control loop. This system also
shows a static mixer. This may be included to agitate the Another more recent development is the use of cross flow
beer and un-dissolved gas to accelerate the absorption of membranes to filter beer, which will be discussed later.
gas into the beer.

92 General Certificate in Brewing

 Filtration uses one or more of the following three Diatomaceous earth (DE) or kieselguhr is made from the
principles:- skeletons of minute sea plants which have been kilned and
milled to various grades of fineness. This is the most
porous, rigid and effective filter aid. Kieselguhr can used for
both precoat and body feed, depending on the grade (i.e.
KG particle size). Kieselguhr is sometimes referred to by
trademarked brand names such as Celite.

Perlite is made from volcanic minerals which are heated in

a furnace to form minute glass bubbles. It has a less
complex structure than kieselguhr and is less effective.
Perlite is often used for pre coating. Some small breweries
also use it for the bodyfeed.

Cellulose fibres, usually mixed with other materials such as

kieselguhr, perlite starch or silica gel to give a product that
is less harmful but still provides good filtration properties.
Brands include Becofloc, Arbocel and Celtrox.
Kieselguhr (KG) and regenerative powder filtration.
Silica hydrogel or lucilite is less rigid but it also acts as a
Filtration using one or more filter “powders” uses the stabiliser (by adsorbing proteins and polypeptides) as well
principles of absorption and depth, the technique as as a filter aid.
follows:-
The handling of the unused KG requires considerable care,
A supporting medium (filter cloth or mesh) is pre-coated particularly the avoidance of, or provision of protection
with filter aid. The precoat forms a depth filter, but is against inhalation. The disposal of KG waste filter aid is
mainly required to bridge the gaps in the support medium also becoming more of a problem for environmental and
(wire mesh, wedge wire, or cellulose fibre sheet) and personal safety reasons. Handling systems include the
prevent the support medium being blinded or allowing supply of filter aids in big bags (e.g. 1,000 kg) instead of 20
filter aid, yeast or proteins to pass through into the final – 25 kg bags, and ventilation systems to suck dust away
filtered product. from the operator. The air drawn through the plant
carrying away the dust is filtered to remove the dust before
After pre-coating is complete, beer is introduced into the discharging clean air to atmosphere.
filter. To prevent the filter bed blinding with yeast and
protein, additional powder, known as body feed is dosed Types of rough beer filter
into the beer as it runs into the filter. The yeast and protein
particles are adsorbed by the body feed filter powder, Filters are designed so that the rough beer is delivered onto
gradually building up a layer of powder, yeast and protein the filter bed in as even a flow as possible. Both the
until the filter is filled. The filter does not ‘blind’ because particles being removed and the filter aid will eventually
the body feed continually creates a new filter bed. block up the filter by their sheer volume so filters are
designed for easy emptying and cleaning.
Body feed Precoat
Four types of filter are illustrated in the diagrams below:-
Yeast
1. Plate and frame filter

Rough beer Bright beer

Yeast absorbed
Yeast adsorbed
the filter
by the filter aid
aid
Support medium
(septum)

Filter aids
The common types of filter aid are:-

Learning Material 2016 93

2. Horizontal leaf filter

Horizontal
pressure leaf
filter Rough beer

Filter aid and yeast etc.

Plates spin Bright beer

to remove
filter waste.

Rough
beer in

Bright beer out

3. Candle filter
The candles in modern candle filters are formed from
spirally wound wedge wire, with much smaller gaps
between the wires than used in mash tuns and lauter tuns –
sufficiently small to hold back the precoat particles.

During filtration, the filter cake builds up around the

individual candles.

At the end of filtration, the filter is back washed with water.

The filter cake drops off into the cone and removed via
another larger outlet (not shown).

4. Cross flow filtration

Cross flow filtration does not use kieselguhr or similar filter

aids, but instead uses semi permeable membranes with
pores of approximately 0.5 micron diameter, with high beer
flow rates to help keep the membranes from blinding.

94 General Certificate in Brewing

 degree of automation are making this an increasingly
attractive proposition, particularly for larger brewers.
Increasing numbers are being installed around the world
instead of filter aid filters.

The membranes for bright beer production are typically

manufactured from PolyEtherSulphone (PES), the filter
modules consisting of bundles of hollow fibres in a housing.

Unfiltered beer contains solids, with particles which are

different in size, quantity and structure. These have to be
filtered from the beer to get a bright beer which meets the
expectation of the customer.

In cross flow filtration, these particles build up a fouling

layer on the membrane. Excessive layer build up is delayed
by use of high flow rates across the membrane, which helps
to keep the layer thickness down and slows down the Example layout of cross flow filter plant
blinding of the individual pores in the membrane. To
achieve the required high flow rates, the system needs
powerful pumps, resulting in high energy consumption.
This energy warms the beer up, resulting in the need for an
inline cooling system.

Comparison of filtrate flow rates from cross flow and dead

end filtration (no filter aid used). The high flow rates across
the membrane help to keep the pores clear, thus
maintaining the filtrate flow rate.

In the above process, the unfiltered beer is recirculated,

with a partial bleed off back to the unfiltered beer buffer
tank, and fresh supply of unfiltered beer is drawn in to
replace the volume of filtrate and bleed off.

Lenticular filters

Lenticular filters are used by some larger breweries for

polishing filtration or for removal of low particulate loads,
such as yeast and proteins after beer recovery, and by
In most systems, the beer is pumped through a buffer tank numerous microbreweries as the main form of primary
or so called feed and bleed tank where, after period of filtration. In all cases, these filters are used because of the
production, a quantity of beer remains with a high solid convenience of lack of powder handling systems, simplicity
loading, which is discharged for further treatment or of filtration operations, and ease of regeneration and the
disposal. flexible sizes of the installations.

A filter run is considered complete when the differential The filter sheets are of modular design, allowing for easy
pressure builds up due to blinding of the membrane pores fitment into the housings and use of spacer units in larger
and the filtrate flow rate reduces to an unacceptable rate. housings when filtering small volumes / low flows. The
The membrane is cleaned using caustic, normally hot, often filter sheets are supported and separated by polypropylene
with additives and an acid neutralization flush afterwards. support discs

In spite of the high energy and detergent costs, the savings

in filter powder purchases, effluent disposal, and the high

Learning Material 2016 95

Cross section of lenticular filter pack Trap filters are used to catch any small amounts of filter aid
leaking through. A cartridge filter consists of a chamber
which is fitted with filter elements housed in nylon supports
to form replaceable cartridges. These are designed to be
cleaned and sterilised a number of times before
replacement is required due to excessive blinding of the
filter material. The cartridges are often back-flushed at
high flow rates as part of the cleaning process.

Depending on the material the elements are made from,

they may use mainly depth filtration, or surface filtration.
They are ideal for sterilising purposes, both for liquids
(water, beer, cider) and for gases (e.g. oxygen, aeration air,
Flow through lenticular filter CO2). The typical pore size used in breweries for “sterile”
filtration is 0.45 micron. Note that this would not be
considered suitable for the level of sterility required for
pharmaceuticals for example, but is considered adequate
for the type of contamination experienced in breweries.

Stabilising filtration
Stabilising agents such as silica gel and PVPP can be dosed
into the beer on its way to the filter, either the KG filter, or
standalone filter systems. Alternatively, filter sheets can be
impregnated with a stabilising agent, for example, PVPP.
Due to the expense of PVPP, standalone filter systems
incorporating recovery and regeneration systems are used
in some breweries.
Lenticular filters are normally capable of being cleaned with
detergent and capable of being hot forward flushed, and Sterile Filtration
cold back-flushed to regenerate the filter medium.
Microbes are by definition very small, but they do have a
Similar filters are obtainable in pre-packed filter form, the finite size and they can be trapped or held back by a very
filtration medium consisting of a mixture of kieselguhr and fine filter. This is the principle of sterile filtration.There are
cellulose fibre, instead of simply cellulose or polypropylene three types of filter that can be used to produce sterile
fibre. These are also capable of being regenerated a beer:-
considerable number of times reducing the purchase or
rental costs. A kieselguhr filter with a very fine powder grade, although
it is usual and recommended to follow this with a final
Polishing filtration polish or membrane filtration. The KG filter is never
considered able to produce consistently sterile beer on its
The polishing filter utilises the depth filter effect with a fine own.
pore filter sheet or a fine filter powder to trap very small
particles including micro-organisms. Where high flow rates The sheet filter where the cellulose mesh of the sheet is
are required, a plate filter may be used to house and very fine and tightly woven / packed. This type of filter
support the filter sheets. traps the micro-organisms because the passages between
the fibres of the sheet are so narrow. There is also an
Trap filter (cartridge filter) electrostatic effect whereby the microbes adhere to the
fibres. The sheets may be held in plate filters or cartridge
filters.

Microbes
trapped in
the filter
Beer flow

Microbes

The membrane filter works on a slightly different principle,

96 General Certificate in Brewing

namely that of a very fine sieve where the particles are held • The trim chiller is used to maintain cold storage
back on the surface of the membrane which has extremely temperature and ensure that particles do not re-
small pores in it (usually 0.45 µm). dissolve before they can be filtered out.

Membranes may be as sheets or as fine tubes. Cross flow

• Buffer tanks are used to protect the filter from
filtration is capable of producing beer which is considered
pressure shocks.
almost sterile, and some companies using cross flow are not
using secondary sterile filtration prior to packaging.
• Filter aids are dosed into the beer via a dosing tank.

Microbes • The addition of blending water and carbonation to

trapped on high gravity beer on transfer from the filtered beer
the filter
Beer flow (bright) buffer tank to the bright beer tanks is shown
here as a typical installation.

Microbes • Trap filters are used to catch any small amounts of

filter aid leaking through. These are typically located
after the filtered beer buffer tank and also often after
dilution and carbonation if high gravity brewing.

There are some benefits derived from the use of sterile Filtration efficiency
filtration as opposed to pasteurisation.
The throughput of a filter system is influenced by both the
There is a significantly reduced risk of developing those
amount of solids remaining in the beer that the filter is
pasteurisation flavours (‘papery’, ‘cardboard’) that result
required to remove and the nature of the solids.
from pasteurising beer, particularly if the beer contains high
levels of dissolved oxygen or is treated with excessive
High levels of TSM (total suspended matter) will result in
numbers of pasteurisation units (PUs).
the need for higher kieselguhr addition rates, which can
NB - Beers with high levels of dissolved oxygen at packaging then fill the space between the filter elements very quickly.
will, over time, develop papery, cardboard and stale The presence of gummy material from the malt (β-glucan)
characteristics even if they are not pasteurised. increases the beer’s viscosity and slows down its flow rate
through the filter.
The very fine filter traps haze forming particles as well as
microbes so that the beer is more stable. The loading onto the filter (the amount of yeast and other
particles in suspension) can be reduced by:-
Example kieselguhr filter plant process overview
• Using long maturation times to allow good clarification
by settling (traditional process).

• Centrifuging the beer before it is filtered.

• Increasing the settling rate by addition of isinglass

finings on transfer from FV to MV.

Safety

Filter aids are considered dust hazards, some of them being

more hazardous (dangerous) than others.

Kieselguhr is the most hazardous especially when calcined

and ground to a fine powder. Hydrated silica gel is the least
hazardous. Filter aids are often delivered in bags which
have to be opened manually and the contents emptied into
a hopper.

Examples of safety equipment used when handling filter

aids:-
• Powder hoppers with negative pressure extraction
systems, where any dust created when bags are
opened is carried away from the operator, and

Learning Material 2016 97

 filtered out of the air before discharge into the • Increased brewing capacity due to more efficient use
atmosphere. These may continue to require of existing plant facilities.
manual slitting and emptying of the bags, or the • Reduced energy (heating, refrigeration, etc.), labour,
bag slitting and emptying may be automated. cleaning and effluent costs.
• Improved beer physical and flavour stability.
• ‘Big bag’ or other bulk systems, with automated • More alcohol per unit of fermentable extract because
transport and mixing with water of the powder of reduced yeast growth and more of the wort sugars
from the base of the bag. being converted to alcohol.
• High gravity worts may contain higher adjunct rates,
• Personal protection in the form of dust masks etc. and thus be cheaper to produce, or be less prone to
hazes (if low nitrogen adjuncts are used).
Notes. • Beer produced from high gravity worts are often rated
smoother in taste.
Draw the workings of the filter in a brewery that you are • High gravity brewing offers greater flexibility in
familiar with. product type. From one “mother” liquid a number of
Why was that design of filter chosen? products can be brewed as a result of dilution and/or
What filter aids are used and what are their usage rates? use of malt and hop extracts and syrups at the same
Describe a filtration operation that you are familiar with. time as dilution and carbonation.
Draw a flow diagram of the plant.
Describe the ‘start up’ and ‘shut down’ procedures. The disadvantages can be summarised as follows:-
What process control parameters are recorded?
Where are beer quality control samples taken? • Due to the more concentrated mash (increased rate of
carbohydrate to water), there may be a decreased
9.3 High Gravity Dilution brewhouse material efficiency and reduced hop
utilisation.
High Gravity Brewing
• Decreased foam stability (head retention).
High gravity brewing is a procedure where wort at a higher Hydrophobic polypeptides have been shown to be
gravity than is required to produce the final beer is important in foam formation and, therefore, their
fermented. It therefore requires dilution with water at presence in beer is essential. It has been shown that
some point during processing after fermentation. By both high and low gravity wort loses hydrophobic
reducing the amount of water employed in the brewhouse, polypeptides throughout the brewing process, with
increased production volume can be met without increasing the high gravity process suffering a more rapid loss. It
existing brewing, fermenting and maturation capacity. would appear that high gravity mashing does not
extract high molecular weight polypeptides, which
Dilution with water to achieve the final sales gravity & includes the hydrophobic polypeptides, as efficiently
alcohol can occur either entirely or in part at almost any as low gravity mashing. Also during fermentation,
stage in the process after fermentation but most commonly there is a disproportionate loss of hydrophobic
is after filtration, usually between the filter and bright beer polypeptides of high gravity wort when compared to
tank. However, it can take place in MV, or pre filter if the low gravity wort.
capacity restriction is before these stages, or post bright
• There can be a difficulty when changing to high gravity
beer tank.
brewing in achieving flavour match to the original
lower gravity beers. The effects of high gravity wort on
High gravity brewing has been progressively introduced into
ester formation during fermentation are most
breweries around the world for the past twenty-five years.
important. However, flavour problems with high
However, internationally it cannot be said that its use is
gravity worts have been exaggerated and adjustments
universal, because some companies have chosen, or are
to the process can be made (for example, yeast
compelled by product and or legal/taxation reasons, not to
pitching rate, fermentation temperature profile,
adopt this process.
dissolved oxygen at pitching and the spectrum of wort
sugars.
The legal and taxation issues are increasingly being
addressed to permit the production of high gravity worts • High gravity worts can influence yeast performance
without undue financial penalties. Nevertheless, the with effects apparent upon fermentation and
impact on flavour of brewing and fermenting certain flocculation. The increased osmotic pressure, elevated
product types at high gravity remains a concern and
challenge to some breweries.

There are a number of advantages and disadvantages to

this process. The advantages can be summarised as
follows:-
98 General Certificate in Brewing
alcohol concentration and modified nutrient balance, all • A de-aeration system that works by spraying the water
have a profound influence on yeast performance during through an atmosphere of inert gas (carbon dioxide or
fermentation. Stress tolerance during the fermentation of nitrogen) where the oxygen in the water is stripped by
the worts by brewer’s yeast is strain dependent. the inert gas.

Dilution of high gravity wort before or after fermentation • Sterilisation by U.V. light. (Chlorine sterilisation would
requires that the water employed be given special taint the water).
treatment. The specifics of the treatment procedure will
vary depending on the dilution point. • Temperature adjustment. (The water will eventually
be added to beer at low temperature).
Most breweries add the water to the concentrated beer
immediately after the final filter. The water for dilution at De-aerated water production methods
this point in the process requires treatment to ensure the
quality and stability of the finished beer. Water must be
• Vacuum de-aeration.
free from colour and flavour taints, and suitable pH.
• Gas stripping.
Treatment includes demineralisation, filtration for particle
• Packed bed gas stripping.
removal, pH adjustment and sterilisation using filters, UV
light or chlorine dioxide (ClO2).

Most importantly, the dissolved oxygen content of the Vacuum deaeration

water must be reduced to less than the final beer dissolved Water is sprayed into a chamber that has a partial vacuum -
oxygen spec, but typical levels aimed for are < 10 μg / l (or produced by a vacuum pump. Because of the low pressure
10 ppb, parts per billion). in the vessel the oxygen in the droplets of water 'flashes
off'. Vacuum deaeration can use either a hot or cold
Methods of producing deaerated water are discussed in the process. The hot system heats water to circa 77°C prior to
following section. flashing off. The dissolved oxygen flashes off faster than
with a cold system, but the water must be cooled
o
In all cases, the water is cooled to typically 4 C or less prior afterwards. Because the process acts to pasteurise the
to storage and use. water no further sterilisation is likely to be needed. The
cold system flashes water at a temperature of 3-4°C
Dilution Water through the vacuum deaerator.

It is most common when brewing beer at ‘high gravity’, to

dilute the beer to its specified alcohol content at the latest
stage, for example post filtration.

The de-aerated water plant is designed to supply water to

the required standard of sterility and dissolved oxygen:-

Pre-treated
Water
Dearation column

Fine U.V.
Coarse Cooler
Filter Steriliser
Filter

Dearated
Water supply
Tank

The plant illustrated above has the following features:-

• A filtration system that ensures that the water passing

through the Ultra Violet light steriliser is clear enough
for the UV to pass through kill any remaining micro-
organisms.

Learning Material 2016 99

Gas stripping Gas (nitrogen or carbon dioxide) is injected at the bottom
Deaeration by purging water with an inert gas such as of the column and as it passes the water falling downwards
carbon dioxide or nitrogen may use a batch process, a tank gas exchange occurs. Oxygen in the water is stripped out by
at a time, or a continuous process using a gas stripping the gas used. To make the process more efficient additional
column. gas can be injected into the water before it is sprayed into
the stripping vessel.
Nitrogen or carbon dioxide is injected into water using a
sinter. The water then passes through a series of holding As with sprayed water gas stripping (see previous point) the
tubes to ensure it is fully dissolved, before being sprayed gas used is selected on the grounds of cost and or the gas
into a stripping vessel. The level of inert gas in the water is targets of the final beer.
so high that on entering the stripping vessel / column, the
gas comes out of solution, causing the stripping of oxygen
along with the injected gas. The mixture of gas and oxygen
is vented through the top of the vessel by a pressure relief
valve. The deaerated water is pumped away from the
bottom of the vessel.

The gas used is chosen depending upon the gas targets of

the final beer. Nitrogen is often used because it is cheaper
to obtain from the air than to purchase the additional CO2
required. If low CO2 beers are required nitrogen will
invariably be used as otherwise some of the CO2 used for
gas washing will dissolve in the water until the water is CO2
saturated. This level of CO2 may cause the CO2 of the
diluted beer to be out of specification (high). By using
nitrogen, this problem is overcome. Increasingly, a small
quantity of dissolved nitrogen is seen as a useful means of
improving the head formed when a beer is dispensed.

Dilution control

Batch dilution
The volume of water required is calculated and is added to
the BBT either before or after a measured quantity of beer.
This requires very effective mixing in the tank and often
results in layering, i.e. the diluted beer may have different
ABVs etc. at different levels in the tank – this can be
avoided by a high enough flow rate of beer into the tank.
However, this is the simplest method, requiring no
automation other than an accurate liquid metering method
(and lab analysis) and can be used successfully for small
batches.

Flow ratio control

In this method the required dilution rate is calculated based
on the OG and alcohol in the high gravity beer. This is then
entered into a control system that measures beer flow rate
and controls water flow rate to give the required dilution.

Where installed immediately after a filter which produces

large interfaces, such as a plate and frame filter, the system
can be designed to take the volume of the filter into
Packed bed stripping account so that water in the filter can be pushed to BBT by
Water is again fed into a stripping vessel. The vessel the beer.
contains packing material often in the form of metal rings.
This packing gives an increased surface area for oxygen Diluted beer can be analysed off line and the dilution
stripping to occur. altered manually. Increasingly, the diluted beer is

100 General Certificate in Brewing

monitored by in line instrumentation, and the result is used Every time beer is moved from one tank to another, there is
to feedback to the blending system, which adjusts the the risk of the beer picking up oxygen or other
calculated dosing rate to improve the accuracy of measured contamination such as micro-organisms.
value.
Notes:-
Standardisation/blending procedures and calculations Calculate the alcohol content of a beer that results from
mixing 120 hectolitres of beer at 4% alcohol with 90
Dilution calculation hectolitres of beer with 5% alcohol.

500 hl of high gravity brewed beer at 7.5% alcohol by

volume (%ABV) can be diluted with:
9.4 Considerations for Other Package Types
250 hl of water to produce 750 hl of beer at 5.0%
Filtration and chilling to produce ‘bright’ or ’filtered beer’ is
ABV,
the most widely used production method to prepare beer
Or for packaging, either into bottle, can, or keg. Storage in
Bright Beer Tank (BBT) or Filtered Beer Tank (FBT) prior to
Original volume x Original %ABV = New %ABV packaging marks the end of the brewing process in this
New Volume General Certificate in Brewing, and from here the packaging
process takes over.
Blending beers calculation
Beer can also be packaged un-filtered as either pasteurised
Blending beer to meet quality requirements may be or un-pasteurised (live) product, and this is very common in
required. For example, a high colour beer may be blended some beer markets around the world.
with a low coloured beer to achieve a beer of a desired
colour. Cask Conditioned Beer
Traditional cask conditioned beer is still most commonly
The calculation below illustrates the effect of blending 100 found in the United Kingdom, but with increasing interest in
hectolitres of beer at a colour of 10 units with 50 hectolitres this style of beer dispense around the world. It is defined as
of beer at a colour of 8 units:- beer that:-
• Is not filtered.
(100 x 10) + (50 x 8)
• Is not pasteurised.
(100 + 50)
• Contains live yeast.
• Contains residual fermentable sugar.
Therefore the colour of the mixture = 9.3 units.

The same blending principles can be applied to bitterness, It is beer that is ‘racked’ into casks with the minimum of
alcohol content, dissolved gas content and specific gravity. treatment or clarification. The beer conditions and matures
in cask and is clarified by the addition of ‘finings’ to produce
The resultant pH of blended beers of similar types (e.g. two a bright product.
batches of the same brand, but with differing pHs) is
generally in proportion to the volumes and tends not to The beer is then sold without, or with minimal top pressure
vary much with the alcohol content of each beer. of CO2, using specialised pumps, or directly from a tap
fitted to the cask.
Note that if blending two or more beers of different alcohol
content, and then diluting with water to produce sales Purposes of cask conditioning:-
gravity beer, then the bitterness, specific gravity, dissolve
gas (oxygen / CO2) of each beer need to be converted to a The purpose of cask conditioning is to
standard value, (normally taken as the post dilution value) • Allow the beer to clarify to produce visually “bright”
to be able to calculate the final values of the blended and product (though rarely if ever as “bright” as filtered
diluted product. beer), which is acceptable to the customer.

The following points need to be considered when • If the beer has been dry hopped, extract oils from
attempting to blend beers in tanks:- aroma hops to give a specific characteristic aroma to
the beer.
The beer transfer and tank inlet systems may have been
designed such that good mixing in the tank simply relying • Increase the CO2 content as a result of the slow
on the infeed flow rate is unlikely, due to intentional low fermentation of the residual sugars, increasing the
inlet flow rates, and therefore mixing the beers thoroughly “drinkability”.
without for example gas rousing (not good practice) or
• Change flavour, such as diacetyl removal, mainly as a
mixers (hygienic design problems) will be difficult.
result of yeast metabolic activity.

Learning Material 2016 101

Candidates should follow, and will be examined on, Beer from the fermenter is run either directly into cask
either section 9A or 9B. (typically microbreweries) or, more usually in larger
breweries, by way of a racking tank.
SECTION 9B – CASK AND CRAFT BEER The brewer will tend to hold it in the fermenter until yeast
PREPARATION AND PACKAGING removal by skimming and /or sedimentation has reduced
values to a range suitable for cask racking. Additional
storage time in the racking tank may help in this respect by
9.1 Cask beer preparation for racking allowing further sedimentation.

Introduction It is essential that the correct amount of yeast is carried

Traditional cask conditioned beer is still most commonly forward into the cask. Too much and the beer will be
found in the United Kingdo, but with increasing interest in difficult to clarify on addition of finings, and may lead to off
this style of beer dispense around the world. It is defined as flavours due to autolysis of the yeast. Beer losses due to
beer that:- excess sediment may also become an issue in extreme
• is not filtered. cases. Too little may also result in the beer remaining
• Is not pasteurised. slightly cloudy, because the finings are not effective at
• Contains live yeast. removing proteins alone. Removal of suspended protein
requires a certain amount of yeast to be fully effective. The
• Contains residual fermentable sugar.
lack of yeast may also result in insufficient condition (CO2)
being developed. A yeast count of not greater than 2
It is beer that is ‘racked’ into casks with the minimum of
million cells per ml is usually adopted, although different
treatment or clarification. The beer conditions and matures
brewers will use different target yeast counts, but usually
in cask and is clarified by the addition of ‘finings’ to produce
not less than 0.5 million cells per ml. Should the yeast count
a bright product.
be too low, additional yeast can (and should) be added to
The beer is then sold without, or with minimal top pressure the beer before it reaches the cask.
of CO2, using specialised pumps, or directly from a tap Yeast concentration can be controlled by:-
fitted to the cask.
• Yeast strain selection (top cropping yeasts, which work
Purposes of cask conditioning:- well with finings are usually used).

The purpose of cask conditioning is to • Fermentation management, for example, allowing

• allow the beer to clarify to produce visually “bright” sufficient time for the yeast to settle out when cooling
product (though rarely if ever as “bright” as filtered the beer after completion of fermentation.
beer), which is acceptable to the customer
• Centrifuging the yeast out of beer ex fermenter, and
• if the beer has been dry hopped, extract oils from adding back a controlled amount of yeast. The yeast
aroma hops to give a specific characteristic aroma to added back is rarely the yeast removed by action of
the beer the centrifuge as this yeast will contain a large number
of atypical yeast and proteins. Freshly cropped, highly
• increase the CO2 content as a result of the slow viable yeast is used instead.
fermentation of the residual sugars, increasing the
“drinkability” Residual sugars for conditioning
It is important that there is some fermentable sugar left in
• change flavour, such as diacetyl removal, mainly as a
the beer at the end of fermentation. Secondary
result of yeast metabolic activity.
fermentation is desirable to augment the low level of
Yeast count control: dissolved carbon dioxide in the beer flowing from the
fermenters. As occurs in maturation tanks for beers
destined for filtration, the evolution of CO2 during
conditioning also helps to wash out small amounts of off
flavours.

Beer from tall enclosed cylindro-conical fermenters tends to

have a residual CO2 content which is too high for cask beer.
It is therefore usual to use fermenters which are
comparatively shallow specifically for producing cask beer.

However, too much sugar and the beer will over-condition

causing excess pressure in the cask and fobbing. Too little
and conditioning will not be effective. 2 degrees of
fermentable sugar (0.5 °Plato) is generally considered about
right.

102 General Certificate in Brewing

Secondary fermentation leads to the production of ethanol 5. Length and vigour of the boil
as well as carbon dioxide and heat energy. • Adequate boiling promotes protein precipitation.
• The effectiveness of any copper finings regime is
Fermentability is controlled by:-
fundamental to final beer clarity and fining ability,
• Fermentation management, for example, cooling
and is dependent upon the wort pH.
before the fermentation is complete, though this can
be difficult to control without accurate measurement 6. Break removal
of specific gravity to determine the required cooling • Excess break (nitrogenous compounds) allowed
start point, and good (rapid) cooling systems, or through to the FV can coat the yeast, leading to
• Adding a controlled quantity of fermentable sugar, poor fermentations, reduction in the final beer
known as primings just prior to filling the casks. stability and finings difficulties.
7. The yeast strain/s used
9.2 Cask beer clarification Yeasts may be very flocculent or powdery, or anywhere
between the two extremes. Some breweries use yeast
Particles, for example yeast and insoluble protein particles, which is a mixture of strains, a flocculent yeast which
will sediment out as long as they are heavier than the beer. rapidly settles out to improve fining performance, and
The rate of clarification depends on the size of the particles, a powdery yeast which remains in suspension to
how dense the particles are and how far they have to fall. provide those last few degrees of attenuation and
conditioning. Other factors include:-
If clarifying agents, for example isinglass finings or auxiliary • The yeast count at rack.
finings are added, they help the particles clump together to • Whether top or bottom fermenting yeasts.
form larger diameter particles, and thus sediment quicker.
• The continued presence of adequate calcium to
promote flocculation.
8. Conditioning
• The type of and design of vessel used for the
settlement after fining - FV, cold conditioning tank,
cask.
• Time and temperature - the colder the
conditioning temperature the more likely the
removal of potential chill haze forming proteins.
Brewers may have to use two different kinds of finings – • The attenuation limit of the beer - how much
auxiliary and isinglass. They may be added, either in racking fermentable sugar remains when the yeast is
tank or directly into cask at racking or a few days later, but o o
cropped and the cooling started. 2 SG (0.5 P) is
allowing time to settle prior to dispense. about right for a cask conditioned ale. Above this
the secondary fermentation process will be too
Factors affecting Beer Fining
vigorous, producing excess carbon dioxide and
The fining of a beer and the propensity of a beer to form
causing turbulence that reduces fining
hazes is dependent upon many factors.
performance.
1. Water composition • Beer pH and viscosity.
• Sufficient calcium to precipitate phosphates, 9. Quality of the finings used
proteins and oxalates. There are a number of different types of auxiliary
• Control of mash pH to consistently achieve best finings available, and not all isinglass finings are the
practice levels. same. One particular type may work better on a beer
• Absence of heavy metals, colloidal silica, etc. than another.
2. Malt quality Auxiliary finings
• Low ß-glucan levels are required. High levels of ß- There are a number of different types of auxiliary finings.
glucan lead to high wort and beer viscosities, The most common is based on acidified silicates.
slowing fining action (apart from the risk of hazes). Polysaccharides (gums such as acacia, gum arabic) and
3. Mash pH seaweed extracts - finings based on carrageenan or
• Controlled in part by liquor composition. alginates (carbohydrates from seaweed) and blends of part
• Lower pH values optimise proteolysis. silicate/part polysaccharide finings are also available.

4. Gravity of last runnings All of these systems are colloidal solutions. They carry a
• Excess sparging will leach undesirables from the high negative charge and react with positively charged
mash, leading to increase in haze forming potential proteins, including collagen and other positively charged
and fining difficulties. This is exacerbated by high materials to clump together to form flocs which can then
pH values, when extraction of tannins and silicates sediment. Auxiliary finings normally enhance the activity of
is increased. the isinglass finings. The treated beer is less liable to form a

Learning Material 2016 103

haze, thus improving saleability and shelf life. They are the positive charge of the collagen ensures the cells are
usually used in combination with isinglass finings, but must entrapped. Collagen also produces flocs with certain
be added and mixed with the beer before the isinglass negatively charged proteins, though most of the proteins
finings, never at the same time. are trapped by the mesh of yeast and collagen. The flocs
are large, and fairly compact, and settle comparatively
The best type of auxiliary finings used will vary dependent rapidly, so clarifying the beer. The greater the density of
upon the individual beer. The spectrum of proteins present the floc (known as “more compact”), the more rapid the
will usually react positively to a number of different finings settlement.
agents, but just occasionally one finds a beer that will
respond to only one particular type. Beers vary greatly in their reaction with collagen. The
flocculence of the yeast strain, the protein / polyphenol
The advantages gained by using an auxiliary fining agent concentration, pH, calcium and magnesium content can all
include:- have an influence.
• Reduced use of isinglass finings.
• Brighter finished beer. Another feature of isinglass finings molecules is that they
• Increased speed of fining. are sufficiently long for some negative groupings also to be
• Increased speed of re-settling. present, so that reactions may occur with limited amounts
of positively charged material, including fatty compounds
Silicated finings also give:- (so improving head formation).
• stabilisation against non-biological haze formation Finings storage
• a degree of protection against chill hazes
To reduce transport and storage costs, finings are often
Isinglass finings delivered in “triple strength” or paste form. They should be
Isinglass finings are made from the swim bladder of specific o
stored in a cooled room (ideally < 10 C), but not at freezing,
types of tropical and subtropical estuarine fish. This until ready to be used, when they are normally diluted with
contains high levels of a protein called collagen which potable water, to “ready for use” (RFU) strength. This is for
makes the yeast cells clump together by an electrostatic ease of measurement and where bulk finings are used, to
effect. reduce the viscosity and make pumping easier.
As the active component of isinglass, the collagen must be Sufficient RFU isinglass for about one week’s use can be
in solution and must be microbiologically stable. It is made up at a time. This can be prepared a day before the
prepared by cleaning and drying the swim bladders, then first intended use in order to allow time for any air
shredding and soaking them in dilute acid (either introduced to the finings to dissipate / be absorbed by the
sulphurous or tartaric to which metabisulphite (SO2) is metabisulphite.
added). This yields a viscous, translucent material, which is
In spite of the use of metabisulphite, it is essential that all
diluted to 0.5 to 1.0 % (w/v) for use. Additions to beer at
equipment associated with finings transfers and storage is
approximately 1.0 g/hl are usually required.
maintained to the same microbiological standards as say
The collagen fibres in the isinglass are teased apart by the fermenting vessels and associated mains.
dilute acids used to make finings. There are three strands
Finings have a limited shelf life and stocks must be
of collagen in each coil, which gently unwind in dilute acid,
controlled to ensure they do not go out of date.
and produce a lattice like structure. The turbid cloudy
solution consists of soluble collagen (active component) Finings addition rates
and gelatine (denatured product). There are three principle objectives of beer fining:-
The temperature of solution is critical, and solubilisation • Bright beer.
should take place below 10°C. Collagen is a protein and will • Rapid speed of fining.
denature above 25°C, so preparation and storage is also • Tight and minimal cask bottoms.
best below 10°C.
Dosing rates for both auxillary and isinglass finings should
Finings solutions also usually contain sodium be regularly checked, and optimised for every brand of
metabisulphite which restricts the growth of bacterial beer. When attempting to optimise the addition rate of
contaminants, notably lactic acid bacteria. auxiliary finings it is important to include a range of isinglass
rates as well to give a matrix of results. The brewer can
Generally speaking top fermenting brewing yeasts (includes then decide on the optimum clarity compared to speed of
most ale yeasts) have a negative electrical charge. As with fining, and volume of sediment, according to requirements.
magnetism, opposites attract, and the negatively charged For example, comparative clarities would be obtained using
yeast cells are attracted to the positively charged collagen the following addition rates, in pints per UK barrel, though
molecules in the finings. A number of yeast cells are the ranges of both products may be extended if none of
attracted to each collagen molecule because of the these results give satisfactory results.
enormous difference in size and charge, become physically
enmeshed within the long molecules which form a net, and

104 General Certificate in Brewing

 Finings additions systems
Auxillary finings addition rates
Pints / mls / 9 mls / pint mls / 500 ml The simplest method, commonly used in micro-breweries is
barrel gallon cask sample sample for auxiliary finings to be added to the FV and mixed in after
0.5 71 1 0.90 the yeast has been removed (skimming / settlement &
1.0 142 2 1.75 removal) and the beer cooled to racking temperature, and
for the isinglass finings to be measured out and added to
1.5 213 3 2.65
each cask immediately prior to filling.
2.0 285 4 3.50
Larger scale breweries may add auxiliary finings on transfer
Isinglass finings addition rates to the racking tank, or to the beer stream or on transfer
Pints / mls / 9 mls / pint mls / 500 ml from racking tank to the cask racker. If added to the beer
barrel gallon cask sample sample after the racking tank, sufficient time must be allowed for
2.0 285 4 3.50 the auxillary finings to mix in and react before adding the
isinglass finings.
2.5 355 5 4.40
3.0 426 6 5.30 Both auxilliary and isinglass finings should be dosed in
3.5 497 7 6.20 proportionally during beer transfer. Dosing all the finings
4.0 568 8 7.00 into a small portion, and adding the rest of the beer on top
will result in portions of over-fined and under-fined beer.
Note: rates quoted are for a UK barrel equivalent to 36 The high viscosity of the finings affects the design and
gallons (gallon = 8 pints, pint = 568 ml) or 164 litres. selection of equipment for automated finings dosing.
Positive displacement pumps are generally used for finings
The optimum rate of use of isinglass is determined by a dosing.
relatively simple method. This involves the addition of
various quantities of standardized isinglass liquid to beer in To ensure good mixing without excessive turbulence which
the appropriate state and assessing haze and sediments would result in small floc formation and thus poor fining
after twenty four hours. The optimum rate is that which action, addition should be made at a point of fairly high
gives clear beer together with low levels of compact turbulence such as a sharp 90 degree bend, before a static
sediment. mixer, or before a chiller (which acts as a highly effective
mixer).
Typical evidence that the addition rates are not optimised
The finings may be dosed into the common beer supply
include the following:-
from the racking tank to the racker, or into the flow to
Under dosed auxiliary Over dosed auxiliary individual heads.
slow beer fining bulky, loose cask sediments Dosing is controlled by measuring the beer flow using in
slow re-settlement unstable sediments - cloudy line meters and dosing proportional to the beer flow. It is
beer therefore simpler, requiring less equipment, to dose into
the main beer flow to the racker than into the flows to the
poor beer clarity
individual racking heads.

Under dosed isinglass Over dosed isinglass The following diagram shows the setup of a larger cask
racking operation, where both auxiliary and isinglass finings
slow beer fining bulky sediments are dosed into the beer on transfer from the racking tank to
slow re-settlement the cask racker filling heads.

poor beer clarity

Typical addition rates in commercial use are

• Auxiliary finings 1 pint / barrel
• Isinglass finings 2 pint / barrel

Note that finings will not remove effectively:-

• Colloidal hazes caused by metallic contamination.
• Bacterial contaminations.
• Dead yeast cells.
• Wild yeasts.
• Beers with particle loadings much higher or much The racking tank contains settled, but un-fined beer. The
lower than the optimum range. beer delivery pump is a centrifugal pump controlled to
develop a constant pressure (pressure feedback system not
Learning Material 2016 105
shown). The beer passes through a flowmeter, which feeds 28.3 grams, respectively) and are vacuum-packed in
back to the PLC system, which then controls the flow of laminated bags and inert gas flushed, in order to reduce the
auxiliary finings dosed in using a variable speed positive loss of essential oils.
displacement pump. This is mixed in using a static mixer, or
perhaps simply sufficient main to give approx. 30 seconds It is usual then to add one or more pellets or plugs to each
contact time. RFU finings are then dosed in based on the container at filling, depending on the desired hop character.
beer flow rate using a variable speed positive displacement Oil-rich Extracts
pump. One or more sharp bends are then installed Produced by liquid CO2 extraction of whole hops or pellets,
between the injection point and the racker filling heads to the enriched oil extracts can be added to unfiltered beer to
ensure thorough dispersion, without excessive turbulence. enhance hop character and substitute for dry-hopping
(leaving no hop residue in the casks, which has to be
PRIMINGS AND HOP ADDITIONS TO CASK removed at the start of cask washing prior to refilling).
Primings sugar In order to achieve rapid dispersion of hop oil in beer, the
Primings - sugar added to either promote secondary extract is usually dissolved in alcohol prior to addition to
fermentation (conditioning) or to make the beer sweeter, the beer. It can be added either on transfer to maturation
invariably added as syrup. tank, to racking tank or in-line on transfer to the cask
racker.
Instead of stopping primary fermentation in the FV (by
crash cooling) in order to ensure sufficient fermentable Hop oils can be further fractionated into separate, highly
extract, the brewer may add thin syrup (e.g. SG 1180) to flavour-active elements, which are described as “spicy”,
the beer either in fermenter, racking tank, or directly to the “estery”, “herbal”, “floral” or “citrussy”. These products are
cask. The syrup may be sucrose, inverted sucrose, or a normally available as 1% solutions in ethanol and be used
mixture of cereal starch hydrolysate plus inverted sucrose. separately or in various combinations to produce a wide
The degree of fermentability of the sugar is determined by and varied range of hop-related aromas.
the amount of secondary fermentation (conditioning)
required. Some colouring matter in the form of caramel, 9.3 Cask washing and racking
naturally coloured sugar (e.g. molasses) or extracts of
coloured malts may be present in this “priming sugar”. Cask preparation & inspection
Before the cask can be washed and sterilized, it is necessary
Additions vary in the range 0.35 - 1.75 litre/hl (0.35 – 1.75%
to remove the old shive and bung. The external washer
v/v, assuming an SG of 1.080), with sweet milds and stouts
does not guarantee that all labels will be removed, and it is
receiving the greatest sugar additions.
common for personnel to remove labels prior to the
Colour may be added, in the form of caramel or coloured washer, when removing the old shives and bungs, though
malt extracts, to adjust the beer’s colour. sometimes this may take place when carrying out the
internal inspection after cleaning.
Hop additions
The cask is generally inspected manually for:-
Dry hops, aromatic hop pellets or hop oil are added to give
• Damage, which might for instance cause the cask to
the beer a hoppy character and aroma. These add extra
leak when refilled.
bouquet to the beer derived from the hydrocarbon and
• Excessive weight of beer or other fluids in the cask.
oxygenated fractions of the essential oil. No discernible
The overfilled casks should be taken to one side and
increase in bitterness occurs.
emptied and carefully inspected before being returned
In some breweries pre-isomerized hop extracts may be if OK, to the packaging line.
added to a beer on transfer to the cask racking tank, or • Own brewery markings, or recognised breweries
even, very occasionally, en route to the racker itself. This is where for instance a marketing agreement has been
either to correct a low bitterness, or more commonly, to made.
create a distinctively bitter variation of another brand.
Cask Washer:
Types of hops & hop products used
Purpose: To clean both the inside and outside of the cask
Dry Hops and to present a ‘commercially’ sterile empty package to
The characteristic “hoppy” aroma in cask-conditioned beer the filler.
is achieved traditionally by adding compressed leaf hops
directly into the casks immediately before filling. Features: The casks are transferred to the cask washer
where they are cleaned externally, normally by rotating
These compressed hops are referred to as “hop plugs”, over brushes, but occasionally by using high pressure water
“whole hop” pellets or “Type 100” pellets. They are jets. They are then transferred to the internal washer on a
produced by breaking up baled hops and compressing moving beam or chain and positioned onto stations where
weighed amounts into a single very large pellet or plug. they are cleaned with internal jets, normally hot and
containing detergents.
The hop plugs are either ½ ounce (oz.) or 1 oz (14.2 and
106 General Certificate in Brewing
The final station is for steam sterilisation. Cask racking (filling) machine

Notes: The incoming casks will contain debris and possibly Purpose: To transfer beer into the cask to achieve the
dry hops. The drainings and in particular the hop debris following parameters:-
may be collected to prevent high effluent costs. • Filling with the specified volume of beer.
• Protecting the quality of the beer by minimising air
Detergents must never be used on wooden casks as the
pickup and avoiding fobbing.
detergent will soak into the wood and taint the beer. Hot
water and steam only must be used. Features: Racking machines consist of filling heads with
down tubes to fit the size of cask.
Wooden casks are very difficult to sterilise, even with a long
steaming time. The cask is counter pressured or simply purged with CO2
before the beer valve opens.
After cleaning, the casks should be internally inspected to
The beer may be metered into casks. Normally filling is
ensure there is no residual debris such as bungs, shives,
stopped only when the cask is full to reduce air pickup,
hops or insects stuck to the internal walls, which are
though it has to be accepted this is likely to result in filling
commonly found, particularly towards the end of summer,
with more than the nominal volume.
or that the casks are heavily scaled up and liable to be
harbouring microbiological contaminants. Excess beer is returned to a fob return tank
Cask Washing Machine Notes: A diagram of the cask racking system is shown
below.
External
wash Minor air pickup during filling is not so detrimental to
quality because yeast present in the beer scavenges oxygen
during cask conditioning.
However, it is good practice to minimise oxygen pickup
wherever possible to reduce off flavours and hazes
Hot
Rinse resulting from high oxygen levels.
Steam
Drain Rinse water/detergent
wash Cask Racking
Beer in
CO2 counter
Cask racking installations & practices pressure
Beer for cask racking can be supplied directly from the
fermenting vessel or from a separate racking tank. In the
illustration below, beer is run from the FV into a racking
tank and fob from the filling operation is returned to a fob Fill
tank. The settled fob is then run back into the racking tank. height

The temperature of the beer when racked will vary from

brewery to brewery, some filling as cold as 2°C, though
more typical temperatures in small breweries are around 7
– 9° C. However, the temperature should always be low
enough to have encouraged sufficient yeast and protein to Beer valve
have settled in the FV and racking tank, and so not overload
the finings, and to be below dispense cellar temperature.
Fining action and final beer clarity is better if the Full cask inspection
temperature rises slightly after finings addition. Purpose: To check that the casks from the filler are filled
with the correct volume of beer.
Beer supply to Cask Racking To ensure the cask is not leaking.
Fermenting
vessel The cask is usually labelled at this point, with beer quality
and other information required to allow tracking of the cask
Fob and the beer inside.
return
Features: Inspection is by eye as the shive is inserted
Racking immediately after filling.
tank
In larger installations, the filled casks will be individually
weighed as a check against gross short fill. Because of the
small size of even larger cask operations, the individual
casks are rarely tared prior to filling, but an assumed
average empty cask weight is used.

Learning Material 2016 107

Notes: The need for the cask racker to demonstrate due Before the addition of clarifying agents (finings) the beer’s
diligence in meeting the requirements of both the national condition (CO2 content) will continue to develop. The
taxation* and the regulatory authorities* means that presence of yeast helps to protect the beer quality by
inspection is essential. (* Will depend on country or region). scavenging oxygen.
Inspection is backed up with accurate volume After the addition of finings and when the beer has
measurement for individual packages. In the case of casks clarified, it is more vulnerable. It must be kept still so that
this means filling into specially tared (pre-weighed or the settled yeast is not disturbed and it must be sealed
standardised) containers (closed) to prevent the access of air.

Records of inspection are kept for the relevant authorities. Disturbance of the flocs in the final cask will lead to the
Correct filling procedures should conform to the beer being turbid, but resettlement / re-clarification is
appropriate codes of practice. usually possible up to five times (only once or twice in the
cellar, because it is likely to have resettled a number of
Safety times during distribution) without fresh finings being
There are numerous hazards associated with cask racking. added.
Some are listed below along with the normal procedures Use of soft and hard pegs
used to reduce or eliminate them:- Conditioning in cask is affected by both the temperature of
beer storage and the time that it is stored.
Hazard Safety procedure
Manual Plant designed for minimum manual Immediately after delivery, when the cask has been set in
handling handling. the final position for dispense, the cask should be vented
accidents for 3 – 6 hours to vent off excess pressure, usually by
Staff trained in safe working procedures.
replacing the hard insert in the “shive” (inserted at the end
Noise Plant designed to reduce metal casks of fill), with a soft peg. This is the conditioning / settling
colliding etc. period. The soft peg is cut from wood “with the grain” so
that gas can vent through the vertical “pores”.
Building designed to absorb noise.
Once the cask has “settled”, i.e. is not generating more
Use of ear protectors mandatory.
CO2, the cask should be hard spiled to reseal the cask. This
Slips trips Use of non slip materials for floors and maintains the condition of the beer by preventing any gas
and falls steps etc. loss (or ingress). In this case, the wooden peg is cut “across
Regular cleaning of floors. the grain” so that there are no pores or openings.

Machinery Permit to work procedures for The soft spile should be replaced during periods of
accidents maintenance. dispense, or if regular dispense occurs, the soft spile should
be loosened to prevent a slight vacuum developing, and
Guarding of machinery. lifting of the sediment due to CO2 bubble evolution.
Heat and Guarding of machinery. At the end of each period of dispense, the cask should be
chemicals resealed with a hard spile to maintain beer condition as
Staff training in safe working procedures.
much as possible.
Personal protective clothing & appropriate
handling equipment Shives (bungs) are traditionally made from beech wood, but
have been largely replaced by various synthetic plastics,
principally for improved hygiene.
Conditioning in cask
Storage temperature of cask beer
Conditioning in cask is affected by both the temperature of
beer storage (ideal is 12 - 14°C) and the time that it is
stored. Cask beer contains yeast and, therefore its flavour
is liable to change during its shelf life far more than filtered
beer.
Because cask beer is not filtered and /or pasteurised, the
shelf life is significantly less than keg or small pack beer,
being usually not more than 6 weeks. Once opened, cask
beer should ideally be consumed within 3 days, if dispensed
by a traditional beer engine and venting, when air is drawn
into the cask as the beer is drawn out. However, as with all
foodstuffs, stock control should ensure the minimum
storage time at point of sale, with ideally no more than one
week between receiving the cask and it being dispensed.
108 General Certificate in Brewing
Shelf life In this way, passing beer through the heat exchanger will
safely chill the beer to just above the freezing point of the
Dispense beer.
The beer is dispensed through a beer pump, some of which
can draw air into the drinking glass. The effect of this is to
create a foaming head on the beer because of the presence
of nitrogen although there is insufficient time for the beer
to be oxidised.

During dispense, unless a CO2 or nitrogen top pressure

blanket is applied, air is drawn into the cask to replace the
beer. The effect of this is to oxidise the beer and make it go
stale, but also to risk the introduction of potential spoilage
organisms, such as lactic and acetic bacteria.

Consequently once cask beer has been put on sale, it has a

very short shelf life, perhaps one or two days. As noted
above, this problem can be reduced by keeping a low Plate Heat Exchanger (PHE) Design
pressure of an inert gas (CO2 or N2) say 1 – 2 psi on the
cask. The plate heat exchanger is by far the most widespread type
of heat exchanger in the beverage industries. For brewery
The cellar applications, a stainless steel frame is often preferred to the
Beer must be stored in a clean environment: it is a food coated steel frames for reasons of hygiene, maintenance
and is perishable. The cellar is a food room and is subject and appearance.
to Food Hygiene Regulations and may be visited by the
Environmental Health Officer (or equivalent). The PHE comprises a collection of plates assembled within a
In perhaps the majority of cases poor product is caused by frame. The two process fluids flow in the spaces between
the plates and are distributed along the length of the heat
'in-house' problems. These can also be resolved 'in-house'.
exchanger by means of circular passages cut into the
Common causes of poor quality beer include incorrect
corners of the plates. The flow channels between the plates
storage temperature, dirty dispense lines, poor quality
glass washing and disturbing cask beer, for example when and the distribution passages are sealed by a gasket fixed to
the face of each plate. A seal is made between the gasket
tilting as the cask empties.
and the reverse face of the adjacent plate.
Notes
Describe a cask beer operation in a brewery that you are There is a high degree of turbulence in the fluids flowing in
familiar with. the narrow passages, created by the high velocities and the
pattern embossed into the plates. Very good heat transfer
How many times are the casks moved after fining before and a degree of ‘self-cleaning’ are achieved under these
the beer is dispensed? conditions.
What effect does this have on the beer’s quality?
The flow patterns through a heat exchanger can be either
counter-current or co-current. The normal PHE flow
9.4 Craft beer preparation for packaging arrangement for a beer cooler is counter-current where the
two fluids flow in the opposite directions.
BEER CHILLING
A co-current heat exchanger is also suitable for chilling beer
The final stage of beer maturation, prior to packaging, is by only a few degrees, where there is a risk of freezing if the
usually cold storage at less than 0°C and again, usually for control is poor, but with the improvements in control
several days. The most efficient way to chill beer to low systems, co-current chillers are rarely used nowadays. Only
temperatures is to use a heat exchanger, either on transfer a counter current heat exchanger is therefore described.
from FV to MV, or if uni-tanking, by recirculating through a
heat exchanger. Most breweries use plate type heat Example of flows through a counter current PHE.
exchangers (PHE) using glycol or brine as the refrigerant,
but some use shell and tube types, using ammonia, glycol
or brine.

The beer is cooled to close to its freezing point (typically –

o
1.0 to –2.0 C, depending on the alcohol content) in a heat
exchanger, the temperature change coming from the use
of secondary refrigerant, such as propylene glycol solution,
o
as the coolant, at approximately -4 C.

Learning Material 2016 109

 Good flow rate across
plate surface

Cross section of plates and counter-current flow:-

BEER FILTRATION
Consumers have come to expect visually clear beer, free
of haze.
Beer that is intended to be clear (bright) is often assumed
Modern beer plate heat exchangers may use a recirculating to be of better quality and there is much historical
loop of glycol (or other cooling medium) with small evidence to prove that this is often true. However,
quantities of fresh glycol being fed into the system, unfiltered, intentionally cloudy beer, including wheat
displacing the equivalent volume of warmer glycol. The beer, is still produced and enjoyed in many countries.
benefit of such a system is the reduction in temperature
difference between the glycol and the beer, so reducing Matured beer will still have particles in suspension,
risk of freeze ups. mainly yeast but also smaller particles, mainly protein,
unless it has been fined. There are three types of
Co-current PHE with partially recirculated coolant for filtration:-
improved temperature control.
The purpose of ‘rough’ filtration is to remove all the
particles that would make the beer cloudy.

The purpose of ‘polishing’ filtration is to remove all yeast

and bacteria so that the beer is sterile.

Traditionally, beer has been filtered using filter aids,

predominantly kieselguhr (KG). More recently however,
new filter aids that are capable of being regenerated have
been developed. These reduce powder purchase costs,
waste disposal and improve safety aspects, albeit at the
additional cost of a regeneration process. However, the
underlying physical principles by which beer is filtered
remains the same as with KG.

Shell and tube heat exchangers Filtration uses one or more of the following three
principles:-
Two fluids, with different supply temperatures (in this case
beer and the coolant, typically glycol, brine or ammonia)
flow through the heat exchanger. The beer flows through
the tubes (the tube side) and the other flows outside the
tubes but inside the shell (the shell side). Heat is
transferred from the beer to the coolant through the tube
walls. In order to transfer heat efficiently, a large heat
transfer area is used, leading to the use of many tubes.

There are a number of different configurations of shell &

tube heat exchangers. The following is shown to give the
basic principle of such a heat exchanger.

110 General Certificate in Brewing

 Kieselguhr (KG) and regenerative powder filtration. particularly the avoidance of, or provision of protection
against inhalation. The disposal of KG waste filter aid is also
Filtration using one or more filter “powders” uses the becoming more of a problem for environmental and
principles of absorption and depth, the technique as personal safety reasons. Handling systems include the
follows:- supply of filter aids in big bags (e.g. 1,000 kg) instead of 20 –
25 kg bags, and ventilation systems to suck dust away from
A supporting medium (filter cloth or mesh) is pre-coated the operator. The air drawn through the plant carrying away
with filter aid. The precoat forms a depth filter, but is the dust is filtered to remove the dust before discharging
mainly required to bridge the gaps in the support medium clean air to atmosphere.
(wire mesh, wedge wire, or cellulose fibre sheet) and
prevent the support medium being blinded or allowing Plate and frame filter
filter aid, yeast or proteins to pass through into the final
filtered product. Filters are designed so that the rough beer is delivered onto
the filter bed in as even a flow as possible. Both the particles
After pre-coating is complete, beer is introduced into the being removed and the filter aid will eventually block up the
filter. To prevent the filter bed blinding with yeast and filter by their sheer volume so filters are designed for easy
protein, additional powder, known as body feed is dosed emptying and cleaning.
into the beer as it runs into the filter. The yeast and protein
particles are adsorbed by the body feed filter powder,
gradually building up a layer of powder, yeast and protein
until the filter is filled. The filter does not ‘blind’ because
the body feed continually creates a new filter bed.

Body feed Precoat

Yeast

Rough beer Bright beer

Yeast absorbed
Yeast adsorbed
by the filter
filter aid
aid
Support medium
(septum)

Filter aids
Diatomaceous earth or kieselguhr is made from the
skeletons of minute sea plants which have been kilned and
milled to various grades of fineness. This is the most
porous, rigid and effective filter aid. Kieselguhr can used for
both precoat and body feed, depending on the grade (i.e.
KG particle size). Kieselguhr is sometimes referred to by
trademarked brand names such as Celite.

Perlite is made from volcanic minerals which are heated in

a furnace to form minute glass bubbles. It has a less Lenticular filters
complex structure than kieselguhr and is less effective. Lenticular filters are used by some larger breweries for
Perlite is often used for pre coating. Some smaller polishing filtration or for removal of low particulate loads,
breweries also use it for the bodyfeed. such as yeast and proteins after beer recovery, and by
numerous microbreweries as the main form of primary
Cellulose fibres, usually mixed with other materials such as filtration. In all cases, these filters are used because of the
kieselguhr, perlite starch or silica gel to give a product that convenience of lack of powder handling systems, simplicity
is less harmful but still provides good filtration properties. of filtration operations, and ease of regeneration and the
Brands include Becofloc, Arbocel and Celtrox. flexible sizes of the installations.
The handling of the unused KG requires considerable care,
The filter sheets are of modular design, allowing for easy

Learning Material 2016 111

fitting into the housings and use of spacer units in larger A cartridge filter consists of a chamber which is fitted with
housings when filtering small volumes / low flows. The filter elements housed in nylon supports to form
filter sheets are supported and separated by polypropylene replaceable cartridges. These are designed to be cleaned
support discs and sterilised a number of times before replacement is
required due to excessive blinding of the filter material.
Cross section of lenticular filter pack The cartridges are often back-flushed at high flow rates as
part of the cleaning process.
Depending on the material the elements are made from,
they may use mainly depth filtration, or surface filtration.
They are ideal for sterilising purposes, both for liquids
(water, beer, cider) and for gases (e.g. oxygen, aeration air,
CO2). The typical pore size used in breweries for “sterile”
filtration is 0.45 micron. Note that this would not be
considered suitable for the level of sterility required for
pharmaceuticals for example, but is considered adequate
for the type of contamination experienced in breweries.

Flow through lenticular filter Sterile Filtration

Microbes are by definition very small, but they do have a
finite size and they can be trapped or held back by a very
fine filter. This is the principle of sterile filtration.
There are three types of filter that can be used to produce
sterile beer:-
A kieselguhr filter with a very fine powder grade, although
it is usual and recommended to follow this with a final
polish or membrane filtration. The KG filter is never
considered able to produce consistently sterile beer on its
own.
The sheet filter where the cellulose mesh of the sheet is
Lenticular filters are normally capable of being cleaned with very fine and tightly woven / packed. This type of filter
detergent and capable of being hot forward flushed, and traps the micro-organisms because the passages between
cold back-flushed to regenerate the filter medium. the fibres of the sheet are so narrow. There is also an
electrostatic effect whereby the microbes adhere to the
Similar filters are obtainable in pre-packed filter form, the
fibres.
filtration medium consisting of a mixture of kieselguhr and
cellulose fibre, instead of simply cellulose or polypropylene
fibre. These are also capable of being regenerated a Microbes
considerable number of times reducing the purchase or trapped in
the filter
rental costs. Beer flow

Polishing filtration
The polishing filter utilises the depth filter effect with a fine Microbes

pore filter sheet or a fine filter powder to trap very small

particles including micro-organisms. Where high flow rates
are required, a plate filter may be used to house and
The sheets may be held in plate filters or cartridge filters.
support the filter sheets.

Trap filter (cartridge filter) The membrane filter works on a slightly different principle,
namely that of a very fine sieve where the particles are held
back on the surface of the membrane which has extremely
small pores in it (usually 0.45 µm). Membranes may be as
sheets or as fine tubes.

There are some benefits derived from the use of sterile

filtration as opposed to pasteurisation.

112 General Certificate in Brewing

 This variation can result in a very different drinking
experience for the consumer.
Microbes
trapped on
the filter For this reason it is recommended that beer is fully
Beer flow attenuated and fined (or filtered) prior to packaging. This
‘bright’ beer, in a racking tank or cask, is then re-seeded
with a known quantity of yeast and ‘primed’ with an
Microbes additional amount of fermentable sugar to a packaging tank
before being filled into bottle.

As well as improving consistency as described above, an

additional advantage of this method is that a yeast strain
There is a significantly reduced risk of developing those more suitable for bottle conditioned beer may be chosen
pasteurisation flavours (‘papery’, ‘cardboard’) that result for re-seeding. The yeast for bottle conditioning is often
from pasteurising beer, particularly if the beer contains high chosen over the primary fermentation yeast strain due to it
levels of dissolved oxygen or is treated with excessive having the following properties:-
numbers of pasteurisation units (PUs).
• More flocculent, resulting in a compact and stable
NB - Beers with high levels of dissolved oxygen at packaging sediment in the base of the bottle. If the yeast
will, over time, develop papery, cardboard and stale used for primary fermentation is too flocculent
characteristics even if they are not pasteurised. then yeast may not fully ferment and attenuate.

The very fine filter traps haze forming particles as well as • Better equipped to ferment low levels of sugar.
microbes so that the beer is more stable.
• May give the ‘base’ beer a different flavour during
the bottle conditioning.
9.5 Considerations for Other Package Types
The same ‘base’ beer can be re-seeded with different yeast
strain, or different amounts / types of priming sugars, to
Bottle Conditioned Beer
give different bottle conditioned beer products. For
example, using a Munich type yeast strain may give some
Bottle-conditioned beers may be either bottled unfiltered
wheat beer / cloves / good foam characteristics to a beer,
direct from the fermentation or conditioning tank, from
whereas a Belle Saison yeast may give smokey / vanilla /
cask, or even filtered and then re-seeded with yeast. The
fruity and sweet characteristics with poor foam
important differences to other bottled beers are that they
characteristics.
are unpasteurised and contain live yeast cells so that the
conditioning process can continue in bottle.

It is important when producing bottled conditioned beer

that a consistent and reliable preparation procedure is
followed prior to bottling, as variable product quality can be
seen in the form of:-

• Variable %ABV due to over or under

attenuatuation, or complete or incomplete
conditioning in the bottle.

• Variable beer foam characteristics and carbonation

levels.

• Variable amounts of yeast sediment at the base of

the bottle, and clarity of the beer.

• Variable beer flavour, due to a combination of the

above three effects.

Learning Material 2016 113

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

114 General Certificate in Brewing

Section 10 Beer Quality and Process Control

10.1 Process Specifications • The work of the people who are sampling and
measuring can be organised effectively.
The people who consume our beer expect and deserve a
An example of a sampling schedule is detailed in the table
consistently high quality product.
below:-
The key factors in maintaining consistent quality are the Stage. Frequency. Notes.
establishment of, and the measurement for comparison to, Raw materials Each delivery. Frequency
a set of process and product specifications. depends on
supplier reliability
There are a number of measurements that are taken during
and performance.
the process and at the completion of the process which
indicate whether the process is in control and whether the Brewhouse Each batch/brew. Corrective action
beer is of the right quality. operations can be taken
swiftly.
Examples of the most important of these measurements
are given below. Unfermented Each batch/brew. Corrective action
wort can be taken
The principle of controlling quality is based on setting swiftly.
specifications for each of these measurements, measuring
the process and taking corrective action if the product or Yeast Each batch for Only healthy
process is ‘out of specification’. use in pitching. contaminant free
yeast is selected
Having said that, there are some factors to be taken into for pitching.
consideration:
Fermenting Each vessel/tank. Process control to
• All measuring instruments have a degree of tolerance. beer monitor the
Every 12 hours. fermentation.
• The raw materials used in the brewing process are
naturally grown and therefore cannot be expected to Fermented Each vessel/tank. To monitor
always behave in exactly the same way. beer and beer quality and to
ready for prepare for action
• Errors can be made in sampling, especially when a small filtration in the event of
sample is taken from a large batch. problems.

Therefore it is usual to give specifications a ‘range’ to Beer ready for Each vessel/tank. To confirm
reflect the normal expected variation in values. packaging conformance and
therefore
Methods for Recording, Reporting and the Interpretation suitability for
of Data. packaging and
consumption.
Sampling Schedules.
Packaging Each delivery. Frequency
A sampling schedule is a plan specifying where, how and materials depends on
how frequently samples of the product in process and at supplier reliability
the end of process are taken. or ‘just in time’
agreement.
A routine sampling schedule is required so that:- Beer in Each code. To monitor
• Key measurements are taken without exception and the package packaging
whole of the process is covered. It is too late if the first performance.
warning of a quality problem comes from the consumer.
Plant A specified To monitor plant
• The quality picture can be seen from statistically number of tanks cleaning
presented data. A very useful quality control method is per week. performance.
to look at historical trends. Using this method, current
results are compared to those obtained in previous Cleaning A specified To ensure that
months/years. A sampling schedule makes sure that materials number of the plant is
there is enough data to make these comparisons. samples per cleaned
week. effectively.

Learning Material 2016 115

Collation and presentation of data. • The cumulative effect of deviation from the target and
the effect of any action taken.
It is likely that there will be a large number of results from a
sampling schedule like the one illustrated, especially in a This is a graph plotting the beer colours that were shown
large plant. The results must then be presented in a way above as individual results:-
that highlights the information as effectively as possible.
17

There are two main ways of presenting data so that 16

problems are highlighted and action can be taken:-
• Defect highlighting. 15
• Control charts.
14

An illustration of how defects can be highlighted is given 13

below:-
12
Sample Result for beer colour
11
number (Specification = 10 to 15) 1 2 3 4 5 6 7 8 9 10
1 13
2 13 The defect sample 8 stands out from the others. Also it can
3 12 be seen that there seems to be a trend of increasing
4 13 colours.
5 15
The next graph was prepared by plotting a three point
6 13
moving average of the same beer colour results. The first
7 14
point is an average of colours 1, 2 & 3 the second point is an
8 16 average of colours 2, 3 & 4 and so on.
9 14
10 14 15

It can be seen very quickly that sample number 8 is out of 14.5

specification.
14
This type of presentation is useful, if for example, a simple
decision is required as to whether the beer is passed as 13.5
suitable for packaging.
13
It does not however, assist in analysing results so that some
clue as to the cause of the problem can be discovered. 12.5
1-3 2-4 3-5 4-6 5-7 6-8 7-9 8-10

• It would be useful to know the average colour of these This method of presenting data evens out the highs and
beers. If that was high, then an adjustment to the lows and illustrates the rising trend very well. From this
process upstream could be made. graph, it can be seen that the beer colours have been
• It would be useful to know the range or spread of increasing steadily and that, unless something is done
colours of these beers. If the range is very wide, then about it, they will continue to increase.
the process may be out of control and action may be
required to resolve the situation. The next figure is a bar graph histogram that shows the
numbers of samples that have the same beer colour results,
In order to resolve these problems, statistical analysis in the that is how many beers have a colour of 12, how many have
form of control charts is required. Pictures in the form of a colour of 13 etc.
graphs have much more impact than simple tables. 5

Charts can be in different formats and can show:- 4

• Individual results plotted on a graph; the specifications 3

can be drawn in.

2

• Average results or ‘rolling’ average results plotted on a

graph. 1

• The range of results obtained. 0

12 13 14 15 16

116 General Certificate in Brewing

 In this distribution curve, a wide distribution indicates a 10.2 Process Control
very wide range and a control problem, a narrow Product and process specifications are based on a number
distribution indicates a narrow range with the process well of Quality Parameters and must take into account the
under control. factors affecting the brewing process and the analytical
results during the production of wort and beer.
The next graph below is called a ‘cumulative sum’ or
‘cusum’. It is designed to exaggerate very graphically, how a Wort and beer production involves a number of complex
trend is going and the effect of any action taken to correct a and interacting physical, biochemical and microbiological
problem. It is plotted by taking as a starting point, the processes.
target value which would normally be the middle of the
specification. (For our beer colours, the middle of the The table below lists the main quality measures taken
specification would be 12.5.) during beer production and packaging along with an
explanation why that measure is important.
The next step is to calculate the difference between the
target value and the actual colour. Then the differences are Parameter Relevance to beer quality.
added up cumulatively as follows. Alcohol content (ABV) Indicates the strength of the
beer and value to the
Sample Result difference from Cumulative consumer.
number target of 12.5 sum
1 13 +0.5 +0.5 Indicates the degree to
2 13 +0.5 +1.0 which a consumer can
3 12 -0.5 +0.5 become intoxicated.
4 13 +0.5 +1.0 Original Gravity (OG) Indicates the strength of the
5 15 +2.5 +3.5 beer and value to the
6 13 +0.5 +4.0 Present Gravity (PG) consumer.
7 14 +1.5 +5.5
8 16 +3.5 +9.0 Indicates the strength of
9 14 +1.5 +10.5 flavour of the beer.
10 14 +1.5 +12.0 pH Mash & wort pH affect
enzyme performance in the
14 brewhouse.
12
Wort & beer pH affect hop
10 utilisation and beer
8
bitterness.

6
Wort & beer pH affects
4 microbiological growth.
2
Beer pH affects its flavour.
0
1 2 3 4 5 6 7 8 9 10
Variable pH can indicate
contamination.
The ideal situation for a cusum graph is for it to run along Beer colour Beer colour is immediately
the zero line because that indicates that there is zero perceived by the consumer.
deviation from the target.
Beer bitterness (IBU) Beer bitterness has a strong
The graph above shows that beer colours were in control flavour effect.
until sample number 5 and from then on they were too
high. Trace flavour Trace by-products of
compounds fermentation give the beer
Many breweries enter the results of analyses into computer
its characteristic and
databases. This gives a number of benefits:-
(Diacetyl, DMS, distinctive flavour. Their
• Recording data is quick and easy.
acetaldehyde, esters) balance ensures that the
• It means that cumbersome paper records are not beer will be ‘true to type’.
required.
• Defects can be highlighted automatically. Excess of any substance will
• Records can be easily accessed from a number of points cause flavour problems.
on a network.
• The sort of graphs discussed above can be generated
automatically.

Learning Material 2016 117

 Dissolved oxygen (DO2) Dissolved oxygen is required Sterility Sterility is a key factor
in wort to encourage yeast (continued) because of the microbes’
growth and a healthy ability to grow at
fermentation. phenomenal rates, so a
small contamination quickly
Dissolved oxygen in beer becomes a major problem.
causes oxidation which
makes it taste unpleasantly O.G. or ‘Original Gravity’ is the specific gravity of the wort
stale and after before it has been fermented.
pasteurisation the beer may
also taste of wet cardboard. P.G. or ‘Present Gravity’ is the specific gravity of the sample
when sampled.
Dissolved oxygen in beer
will make it unstable and pH is a measure of the acidity or alkalinity of a substance.
hazes can form during Water is neutral with a pH of 7; acids are lower than 7,
ageing. alkalis are higher than 7.
Dissolved carbon dioxide Carbon dioxide gives beer
(CO2) its lively sparkling character.
Quality parameters are measured at each stage of the
High levels of CO2 will make process so that the performance of each stage can be
the beer fob or over foam. checked and the final outcome of beer quality can be
Dissolved nitrogen. Nitrogen gives beer a stable, predicted.
(N2) tight foam which clings to
the side of a glass as it is The tables below detail the stages where quality is
consumed. measured and the factors that determine each parameter:-
Beer flavour. Beer flavour is its most
(Trueness to type). important characteristic and Wort production and brewhouse operations
it is why people consume
Parameter Determining factors
the product.
Wort specific gravity • Amount of raw material
Customers expect a specific (malt) used per unit of
beer to have a consistent (PG and OG) water.
flavour, that is, it should be
true to type. • Efficiency of the extraction
Beer clarity. Customers expect the beer process.
(Haze, potential haze) that they drink to be Wort colour • Amount of coloured
‘bright’, it looks more material used.
attractive.
• Degree of wort boiling.
Cloudy beer indicates poor • Wort pH.
quality and perhaps Mash pH • Quality of brewing water.
contamination or
contamination. Wort pH • Liquor treatment.
Beer head stability, Most customers expect the
• Malt quality.
(Foam/cling). beer to have an attractive
foamy head and for that • Adjunct type and usage
head to cling to the sides of rates.
the glass. Wort fermentability • Enzyme activity affected
Sterility Microbiological by mash conditions (pH,
contamination is the most Wort attenuation time and temperature).
destructive form of quality limit (WAL)
defect. • Fermentability of different
types of raw materials
Wild yeasts, moulds and and/or adjuncts used.
bacteria will grow readily in Wort sterility • Wort chiller/mains
wort of fermented beer and sterility.
effect its flavour, aroma and
clarity to the degree that • Fermenting vessel sterility.
makes it undrinkable

118 General Certificate in Brewing

Pitching Yeast Analysis. Mature beer production and Maturation/Conditioning
operations.
Parameter Determining factors
Microbiological • Contamination from the Parameter Determining factors
contamination plant. Alcohol content • Conditioning
(ABV) degree/efficiency.
• Contamination from
previous yeast
generation. • Original gravity.
Final specific gravity • Conditioning
(OG & PG) degree/efficiency.
• Integrity of yeast strain
separation.
• Original gravity.
Yeast viability • Age of the yeast.
Beer pH. • Fermented beer pH.
(% dead cells)
• Condition of yeast
Yeast vitality • Health of previous Beer colour • Fermented beer colour.
fermentation.
Beer bitterness • Fermented beer
(IBU) bitterness.
‘Green’ Beer production and Fermentation operations.
Yeast count. • Yeast count from
Parameter Determining factors
(Yeast cells in Fermenting vessel.
Alcohol content (ABV) • Fermentation suspension)
degree/efficiency.
• Time of maturation.
• Original gravity.
• Yeast cropping and
Final specific gravity • Fermentation
purging operations.
(OG & PG) degree/efficiency.
Diacetyl • Length (duration) of
maturation.
• Original gravity.
Beer pH • Wort pH.
• Temperature of
maturation.
• Fermentation
Dissolved oxygen • Transfer-in procedure.
degree/efficiency.
(DO2)
Beer colour • Wort colour.
• Air levels in maturation
tank before transfer in.
Beer bitterness. • Hop additions in the
Dissolved carbon • Fermentation degree.
(IBU) brewhouse.
dioxide
(CO2) • Back pressure on transfer
• Hop utilisation.
in.
Yeast count • Yeast strain/flocculation
Beer flavour • Brewhouse and
(Yeast cells in characteristics.
fermentation operations.
suspension)
• Yeast cropping/purging
• Raw materials, quality &
operation.
usage rates.
Beer flavour • Brewhouse and
fermentation operations.
• Contamination.
Beer sterility • Fermented beer sterility.
• Raw materials, quality &
usage rates.
• Transfer main sterility.
• Contamination.
Beer sterility • Maturation tank sterility.
• Wort sterility.

• Yeast purity.

Learning Material 2016 119

 Bright beer production and Filtration operations. Product Specification - Key Packaged Beer Parameters.

Parameter Determining factors The table below lists the additional quality measures taken
Alcohol content (ABV) • High gravity beer dilution during and at the completion of beer packaging along with
performance. an explanation why that measure is important.
• Filtration/liquor flush
Fill level • The fill level determines the
operations.
amount of beer in the
• Original gravity. package. This is what is sold
Final specific gravity • High gravity beer dilution to the customer who
(OG & PG) performance. expects to get what is paid
for. It also is the volume of
• Filtration/liquor flush beer that is specified in the
operations. ‘contents’ statement.
• Original gravity.
Beer pH • Mature beer pH. Label quality • Customers expect to see an
attractive bottle.
Beer colour • Mature beer colour.
• Legibility.
Beer bitterness • Mature beer bitterness.
(IBU)
• Bitterness loss on • Conformance to local
filtration. regulations.
Diacetyl • Length of maturation.
• Temperature of • Labels correctly aligned
maturation. with no creases or tears.
Dissolved oxygen (DO2) • Transfer-in procedure. Bottle crown quality • The bottle must be sealed
so that beer cannot leak
• Air levels in the bright out or air leak in.
beer tank before transfer
in. Can printing quality • Customers expect to see an
• Filtration performance. attractive can.
Dissolved carbon • Mature beer CO2.
dioxide
• Back pressure on transfer Sterility • Microbiological
(CO2)
into bright beer tank. contamination is the most
• CO2 trimming during destructive form of quality
filtration. defect. Wild yeasts, moulds
Beer flavour • Mature beer flavour. and bacteria will grow
(Trueness to type) readily in beer and effect
• Contamination. its flavour, aroma and
Beer clarity • Time of maturation. clarity to the degree that
(Haze, potential haze) makes it undrinkable.
• Temperature of
maturation.
• Sterility is a key factor
• Filtration performance. because of the microbes’
• Stabilisation. ability to grow at
Beer head stability, • Brewhouse and phenomenal rates, so a
(Foam/cling) fermentation operations. small contamination
quickly becomes a major
• Raw materials, quality & problem.
usage rates.
• Beer handling.
• Contamination.
• Beer additions.
Beer sterility • Mature beer sterility.
• Filter & filter main sterility
• Bright beer tank sterility.

120 General Certificate in Brewing

Packaged beer production and Packaging operations.
Beer head stability, • Bright beer head stability.
Parameter Determining factors (Foam/cling)
Alcohol content (ABV) • Packaging/liquor flush • Beer handling.
operations.
• Contamination from
• Original gravity. plant/package.
Final specific gravity • Packaging/liquor flush
(OG & PG) operations. • Packaging performance.
• Original gravity. Fill level • Packaging performance.
Beer pH • Filtered beer pH.
Label quality • Packaging performance,
Beer colour • Filtered beer colour. labeller.

Beer bitterness • Filtered beer bitterness. • Label stock quality.

(IBU)
Bottle crown quality • Packaging performance,
Diacetyl • Filtered beer diacetyl. crowner.
• Microbiological
• Crown stock quality.
contamination from
plant/package. Can print quality • Can stock quality.
Trace flavour • Trace flavour compounds
compounds. in filtered beer. Can seam quality • Packaging performance,
(DMS, acetaldehyde, seamer.
esters) • Contamination.
Beer sterility • Bright beer sterility.
Air in headspace • Packaging performance.
• Packaging plant sterility.
Dissolved oxygen (DO2) • Transfer-in procedure. Fill level • Packaging performance.
• Air levels in the bright
Label quality • Packaging performance,
beer tank before transfer
labeller.
in.
• Label stock quality.
• Packaging performance.
Dissolved carbon • Bright beer CO2.
dioxide
(CO2) • Packaging performance, Action to be taken when parameters are out of
counter pressure. specification:
Dissolved nitrogen. • Nitrogen additions/dosing.
(N2) There are two points to consider when confronted with an
• Packaging performance, out of specification result:
counter pressure.
Beer flavour • Bright beer flavour. Firstly, what to do with the current problem.
(Trueness to type)
• Contamination. Secondly, what to do to prevent things going wrong in the
future.
• Beer DO2.
When handling any problem, it is best to start with some
• Pasteurisation form of investigation and not to jump to conclusions. The
performance. sort of questions to ask are:
Beer clarity • Bright beer
• Is it real? Are the results correct?
(Haze, potential haze) clarity/stability.
• What is the extent of the problem? Are other beers
• Beer DO2. affected?
• When did it happen? Where did it happen? What else
• Packaging performance. was going on at the time?
• What are the possible causes? What are the likely
• Pasteurisation causes?
performance. • What can be done about it?

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 This is an example of the action that could be taken to Instrumentation for in-line process control.
resolve the out of specification high colour beer discussed
earlier in this section. The brewing industry uses instruments to measure the
quality of the beer in process or the conditions of a process
Investigation and action:- so that the process can be controlled.

Are the results correct? Recheck the analysis. A typical control loop is illustrated below:-

-The result is correct

What is the extent of the Check other beer colours.

problem?
-There are no other defects.
Fermenting
When did it happen? Check the cusum graph. Vesel
Coolant
- Colours started to increase valve
at sample 5. Cooling
Jacket
What else was Check process activities that
happening at the time? could affect beer colour at Control
the time that sample 5 was system
brewed.

- A delivery of a new
coloured malt.
Temperature probe

What are the possible or It is likely that the new malt

likely causes? is causing high colours.

What can be done about For the current problem:- In this model, the temperature of the beer in the
it? “Isolate any affected stock, fermenting vessel is being controlled. The temperature
then either blend away, probe measures the temperature of the beer and sends the
with specially brewed information to the control system which compares it to the
product if necessary, or required value. If it is different, say for example that the
otherwise destroy the actual temperature is too high, then the controller sends a
affected stock. signal to the valve to open sending coolant to the jacket
For the future:- and lowering the temperature of the beer.

- Reduce the amount of Notes.

coloured malt added. Draw a control loop for a process that you are familiar with.

- Investigate the cause of

the high coloured malt. The table below details the principles of instruments in
common use in brewing and packaging:-

Notes.
Describe the action that was taken to resolve an out of
specification parameter in a brewery of your experience.

122 General Certificate in Brewing

 Value measured Instrument description Special points
Temperature • Glass thermometer. The signal from a transmitting
e.g. for mash temp, • Transmitting resistance thermometer (electrical thermometer may need checking.
fermentation temp. resistance ≅ temp).
Pressure • Pressure gauge. Pressure sensors are easily damaged
e.g. for filter pressure • Pressure sensor using a transducer. and need regular maintenance.
differential.
Flow rate • Rotary vane meter. Can be used to measure total volume.
e.g. for lauter tun run off • Magnetic flow meter (change in magnetic field ≅ flow).
flow rate. • Pressure differential across an orifice.
Alcohol (ABV) • Infra-red adsorption. Results usually backed up by
e.g. for dilution of high • Refractive index. laboratory analyses.
gravity beer.
PG • Weight of the liquid in a known volume. e.g. a ‘U’ tube
e.g. for automatic wort in line.
breakdown. • Vibrating ‘U’ tube in line.
(resonance ≅ density).
Haze • Light beam scattered by the particles in suspension is Regular calibration using a clear liquid
e.g. for filtration measured. (water).
monitoring.
Volume • Pressure sensors at strategic levels in the tank. It is useful to have an alternative
e.g. for measuring the • Flow meter on the tank inlet line. method of checking for example
contents of a tank. • Ultra sonic beam measures depth of liquid in the tank. dipping the tank.
Mass/weight • Counter balanced hopper with inlet/outlet gates.
e.g. for weighing the • Load cell on the supporting leg of a tank..
amount of malt
transferred out of a silo.
Dissolved oxygen • Gas transfer through a membrane where the increase The membrane is sensitive and is
e.g. for checking DO2 in pressure across the membrane is measured. easily poisoned (corrupted) by fouling
pickup during beer or damage.
transfer.
Dissolved nitrogen • Gas transfer through a membrane where the increase The membrane is sensitive and is
e.g. for monitoring N2 in pressure across the membrane is measured. easily
injection. poisoned (corrupted) by fouling or
damage.
Carbon dioxide • Gas transfer through a membrane where the increase The membrane is sensitive and is
e.g. for monitoring CO2 in pressure across the membrane is measured. easily
injection systems. • Infra red adsorption. poisoned (corrupted) by fouling or
damage.
Conductivity • Measuring the electrical differential across two Regular maintenance required
e.g. for measuring sensors located in the liquid. especially if the values control a
detergent strength in a system.
C.I.P. system.
pH • Measuring the electrical differential across a The membrane is sensitive and is
e.g. for monitoring water membrane between the liquid and a salt solution. easily
supplies. poisoned (corrupted) by fouling or
damage.

Notes.
List the instrumentation in an automatically controlled process in brewing that you are aware of.
What is the basis of their operation and how do they control the process?

Learning Material 2016 123

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

124 General Certificate in Brewing

Section 11 Beer Quality - Flavour

11.1 Flavour Evaluation - Terminology.

Candidates need to be able to define concisely particular Beer type: Bitter Stout.
beer styles in terms of their aroma, alcohol, colour,
bitterness and palate feel. Raw materials:
Well modified malt with additions of coloured malt and
The main differences between lagers, ales and stouts:- roasted barley.
High levels of hop additions
Beer type: Lager.
Brewing process:
Raw materials: Same as an ale.
Undermodified and very pale malt.
Possibly some cereal adjunct (e.g. maize or rice). Characteristics:
Delicately flavoured hops. Very dark colour with strong flavours of roasted barley.
Very bitter.
Brewing process:
Temperature staged mash. Beer type: Sweet Stout
Bottom fermentation.
Long, cold maturation followed by filtration. Raw materials:
Well modified malt with additions of coloured malt.
Characteristics: Possibly some caramel and sweet primings.
Light colour, delicate flavour.
Often dry and astringent with an ‘onion’ character. Brewing process:
Premium beers at 5% alcohol. Same as an ale.
Lower strength beers at 3-4% alcohol.
Characteristics:
Beer type: Ale - Bitter beer. Very dark colour with flavours of roasted barley. Very sweet.

Raw materials:
Well modified malt with rich flavour. Terminology.
Possibly some sugar adjunct.
Strongly flavoured hops. People sense the flavour of a beer in two ways, aroma and
taste:-
Brewing process:
Single temperature mash. Aroma:-
Top fermentation. Hoppy, Fruity, Floral, Yeasty,
Short maturation, possibly in cask Honey, Sulphury, Spicy,
Cardboard, Chlorine
Characteristics:
Pale colour, strong bitter flavour and hoppy aroma.
Normal strength 4-5% alcohol.

Beer type: Ale - Mild beer. Taste:-

Sweet
Salty
Raw materials:
Bitter
Well modified malt with rich flavour. Sour
Possibly some sugar adjunct. Metallic
Flavoured hops.
Possibly some priming sugar.
Another factor which influences taste is ‘mouth feel’ that is
Brewing process: how the liquid stays on the tongue and helps the flavour to
Single temperature mash. linger.
Top fermentation.
Short maturation, possibly in cask. The various characteristics of the flavour can be given
standard terms so that people tasting the beer can
Characteristics:
recognise and describe that flavour in a common language.
Pale or dark colour, slight bitter flavour and usually sweet.
Normal strength 3-4% alcohol.

Learning Material 2016 125

That way, a beer can be tested and analysed for flavour just This section summarises the known flavour effects of
as it can be analysed for other quality parameters like several of the more important components in beer.
colour or pH.
Non-Volatile Components
People need to be trained to taste and this is done by
exposing them to the tastes and aromas normally (a) Bitterness
associated with beer so that they learn to recognise them Bitterness flavour in beer is derived principally from iso-α-
and to judge their intensity. A common language has been acids from hops, although oxidation products of β-acids
devised to describe beer flavours and brewers throughout (also produced during kettle boiling) can also provide
the world have agreed on a terminology that is used for bitterness character.
beer.
(b) Residual Sugars
In this terminology, each of the recognisable flavours has Residual sugars impart sweetness and mouthfeel and body
been given a name and the flavour wheel is a pictorial to beer flavour. It is unlikely that there will be any
summary of the main flavour characters:- significant level of fermentable sugars present, especially in
a fully attenuated beer, but some may persist.
Alternatively, some beers have sugars added post-
fermentation, not only for active secondary fermentation
during maturation (or in final package for “traditional” cask-
conditioned or bottle-conditioned beers).
The bulk of the residual sugars will be dextrins as such will
not contribute much sweetness character, but will make a
significant contribution to perceived body.

(c) Malt Components

Components derived malt and speciality malts can make
significant contributions to beer flavour, in some cases
(such as Black Malt or Roasted Barley in very dark beers,
like Stouts) being the main over-riding character.

Differing levels of these colour and flavour compounds,

such as melanoidins, etc. can contribute flavour characters
such as: Bready, Biscuity, Malty, Nutty, Chocolate,
Toffee/Caramel, Roasted, Burnt, Astringent.

(d) Inorganic Ions

Several ions have direct flavour effects, in addition to
indirect effects (mainly by influence on pH) during wort
production and on yeast metabolism during fermentation:-

• pH (or hydrogen ion concentration) if low enough, say

less than pH 3.6, will progressively impart Acidic flavour
Beer Flavour Components
to beer.
Introduction • Sodium at low levels imparts Sweetness, but tastes
Appearance and taste are the two sensory attributes on Salty, Harsh and Sour.
which beer consumers judge the acceptability of the
product and they use them to critically evaluate every glass • Potassium will also taste Salty.
of beer they drink. The appearance, colour, hue, brightness,
foam quality and glass fullness are all qualities which can be • Magnesium will contribute Astringent and Bitter
physically measured and, thereby controlled. The taste or flavours.
flavour of the product, on the other hand, cannot be
• Iron notoriously tastes Metallic at very low levels.
adequately described in physical or chemical terms and we
have to rely on human taste senses to control and monitor • Chloride imparts enhanced Mouthfeel and has a
the product. Smoothing effect on beer texture.

However, it is a fact that we can analyse for several • Sulphate has a Drying/Astringent effect on beer palate
hundred components of beer which are known or are and can enhance perceived Bitterness.
expected to contribute to beer flavour in a meaningful way,
either directly alone or synergistically with other
components or even both.

126 General Certificate in Brewing

Many brewers pay particular attention to the balance (f) Dimethyl Sulphide and Other Sulphur Compounds
between Chloride: Sulphate to ensure consistency of beer DMS is a flavour character either regarded as a positive
flavour. character in some lagers or as a major flavour taint in
others. It is rarely detectable in ales.
Volatile Components
The perceived flavour is classically described as Sweetcorn,
(a) Hop Oil but also as Cooked vegetable.
The essential oils in hops are the source of aroma
compounds. These oils are volatile and will be almost Other sulphur compounds are usually regarded as flavour
entirely vaporised from the kettle if they are present from negative, such as hydrogen sulphide (Rotten Eggs), but
the start of a 60–90 minute boil, although some will be some compounds, like thiol esters derived from hops make
converted by heat or chemical reaction. To compensate for a positive contribution to some lager flavours.
this, many brewers who want beer with a hoppy character
add selected aroma varieties into the kettle between 5 and (g) Carbon dioxide and Nitrogen
20 minutes before the end of the boil. This gives sufficient CO2 can contribute to a flavour attribute described as Tingle
time to extract the hop aroma but ensures that all the oil is or Gassy.
not lost in the vapour.
N2 gas (as in so-called “widget” beers in can) at
Late hop character is often described as floral or citrus, but concentrations greater than 20 mg/l, will cause a palate
it can be unpleasant if present in too high a concentration. softening or smoothing effect, also often described as
The variety of hop, the timing of the addition, as well as the Creamy. It is also considered that the smoothing of the
kettle shape and the material of construction all have a nitrogen gas itself or as a consequence of the thicker,
major influence on the subtlety of the final beer aroma. tighter, creamier foam that is usually produced reduces the
perceived bitterness level.
Hops can also be added to beer after fermentation, to the
maturation vessel or to the cask to give beer a dry hop Flavour Evaluation and Tasting
flavour - this is often described as resinous, spicy and
citrus. As the α-acids are only slightly soluble in cold beer, Professional assessment of beer flavour is an important
there is hardly any increase in the bitterness of beer with analytical tool.
dry hopping.
Beers are given flavour profiles so that tasting by trained
(b) Ethanol
tasters can be carried out during and after the production
Ethanol has little direct perceived flavour contribution, but
and packaging processes and they can judge whether a
enhances the perception of other volatile flavour beer meets the required standards.
components, especially at higher (say, greater than 5.0%
v/v) levels.
Each beer brand will have its own unique flavour profile
The main flavour descriptor influenced directly by ethanol is which goes with its other unique specification values.
described as Alcohol warming. Trueness-to-Type.

(c) Higher Alcohols A beer that is ‘true to type’ matches the standard flavour
The concentration of individual higher alcohols (or fusel profile for that particular product or brand. Flavour profiles
alcohols) rarely exceeds flavour thresholds, but collectively are produced by specifying a beer’s typical flavours and
they all contribute to perceived Alcohol warming character intensities and documenting them, probably in a graphic
and Solvent like aroma and taste. form.

d) Esters A typical flavour profile in the form of a spider diagram is

Unlike higher alcohols, several esters exceed flavour shown below:-
thresholds and often are major contributors to perceived SWEET
flavours, especially ethyl acetate (ester, solvent) and iso- ALCOHOL BITTER
amyl acetate (fruity/bananas).

Collectively, they all contribute to fruity/ estery characters.

(e) Vicinal Diketones SOUR HOPPY

Usually regarded as an undesirable character in most
lagers, diacetyl can be regarded as a positive flavour
character in some ales, producing flavour effects, such as
Butterscotch, Buttery, Toffee/Caramel, Vanilla. By YEASTY FRUITY
contrast, 2,3-pentanedione rarely exceeds flavour
threshold, but can be regarded as synergistically enhancing FLORAL
the perception of diacetyl.

Learning Material 2016 127

Taste tests. The beers should be arranged in random order so as to
eliminate bias due to carry-over of flavours. (i.e. AAB, ABA,
Beer must be tasted as part of normal quality control, the BAA, etc.). After tasting has ended, the number of correct
specification being the ‘flavour profile’. answers is counted and compared with the number taking
the test and the statistical significance of the results is
Flavour profiling is described as a “Descriptive” Taste Test, determined.
requiring trained tasters to be able to analyse the flavour of
beer in considerable detail. Even the simplest tests should Common Flavour Taints in Beer
be carried out under controlled conditions or the results,
because of an inability to reproduce them, will be (a) Sulphur Compounds
worthless. H2S (Rotten Eggs) and SO2 (Burnt Matches) are usually
Because tasters – even trained and selected ones – vary in regarded as flavour taints, but sub-threshold levels of a
sensitivity to a particular flavour from ‘blindness’ to hyper- whole range of sulphur compounds.
sensitivity, it is necessary to use several tasters to assess Various hop-derived thiol esters can all contribute to an ill-
each beer. A suitable number for such a “Flavour Panel” is defined, so-called “Lager” character.
8, and 5 should be regarded as absolute minimum.

If problems are encountered, an investigation could include (b) Phenols

a ‘triangular taste test’ or three-glass test, where three One of the most flavour-intense group of substances
samples are tasted with one of the samples being different causing beer taint is the chlorinated phenols, such as TCP,
to the others. generating flavour described as Medicinal, Disinfectant.
The range of individual taster’s sensitivity to these
This is described as a “Difference” test and is used to compounds can vary by several orders of magnitude, so
answer the questions ‘Are the samples different?’, or ‘Do that some individuals are virtually “taste blind” to
the samples differ on a specific attribute?’ chlorophenols.

They may also be used in the selection and training of These compounds are usually generated by reaction
tasters and for monitoring their performance. between chlorine (such as Towns Water disinfected with
Cl2, or inappropriate use of hypochlorite in beer vessels and
If there is a notable difference between the samples, a mains) with phenols in water or beer (often contaminated
statistically significant number of tasters will pick it out. steam, used for plant or container sterilisation); prolonged
and excessive exposure of beer lines in draught beer
For statistically reliable results from a triangle taste test installations to beer line cleaner is also a classic source of
using untrained testers, it is usually recommended that a this beer taint.
minimum of 25 assessors should be used.
Control is achieved by elimination or tightly controlled use
The triangle test is recommended:- of hypochlorite and carbon filtration of all relevant water
supplies to remove any Cl2 residues.
• To detect slight differences between samples.
Related Phenolic taint can be due to wild yeast infection. In
• When only a limited number of assessors is available. this case the flavour taint is described as Medicinal or
Cloves and is usually due to the synthesis by the wild yeast
• For the selection and training of assessors.
of 4-vinyl guaiacol.
Some disadvantages of the test are that:-
(c) Chloranisole
• It is uneconomical for the assessment of a large This compound is associated with the flavour character
number of samples. described as Musty, Fungal or Wet Carpet. It is caused
usually by mould or bacterial infection in water supplies
• With intensely flavoured samples it may be more and is controlled by appropriate hygiene regimes.
affected by sensory fatigue than the paired
comparison test. (d) Metal Ions
Elevated levels of Iron and sometimes Copper and
• It may be difficult to ensure that the two samples that Aluminium can lead to flavour taints such as Metallic, Rusty
are supposed to be the same are in fact identical. and Astringent.

In the Triangle Taste Test the assessor is presented with Some filter aids (diatomaceous earth) contain high levels of
three beers, two of which are identical. The purpose of the Iron and poor quality or corroded stainless steel in vessels
test is to select the odd beer out of the three. The assessor and mains can also contribute.
is normally asked to express a preference between the
beers and to indicate which attribute(s) were perceived as Poorly lacquered cans and kegs can be a source of pick-up
different in making the choice. of aluminium.

128 General Certificate in Brewing

(e) Plastic
Incompletely polymerised plastic (e.g. PET) beer containers
(bottles or one trip kegs) or excessive plasticiser can be
sources of Plastic taint.

In addition poorly cured lacquer linings in aluminium cans

and kegs can contribute.

(f) Aldehydes
Oxidation of fatty acids and other lipids to aldehydes and
other carbonyl compounds, such as trans-2-nonenal, is
associated classically with stale flavour taints (Papery,
Cardboard).

Learning Material 2016 129

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

130 General Certificate in Brewing

Section 12 Beer quality – Dissolved oxygen

Introduction

The quality of a beer changes continually. Beer is not

completely stable in its final package even after packaging
to the highest standards. Generally speaking, fermented
beer will improve in quality during maturation, but will start
to deteriorate once the beer has been filtered or clarified.
The two major factors in this change are the absence of
yeast and the presence of oxygen.

• Yeast helps the beer to mature by absorbing some of

the unpleasant flavour compounds like diacetyl and
scavenging oxygen.

• Oxygen de-stabilises both the flavour and haze

stability of the beer.

12.1 The spoilage of beer by oxygen

Sensitivity to oxygen

A very small amount of oxygen will cause problems because

it only needs a small amount of protein/tannin to form a
haze and only a small amount of oxidised lipid is needed to
give an off flavour.

A DO2 level of 0.5 parts per million will cause problems. To

give a sense of scale, this is a thimble full of air in 500L.

Most brewers try to maintain DO2 levels below 100 ppb (0.1
ppm) in final package which means that oxygen levels pre-
package are considerably less to allow for oxygen pickup
during the packaging process.

Mechanisms of haze formation

The build-up of visible haze particles is particularly rapid in

the presence of dissolved oxygen and heavy metals.
Polyphenols (tannins), from malt and hops are firstly
oxidised. The oxidised polyphenols become linked with
polypeptides (mainly from malt, but some from hops) firstly
to create particles large enough to form haze and make the
beer go cloudy. Oxidation reactions, flavour compounds & their
descriptors
Chill haze occurs when the bonds between the two
compounds is reversible. The material comes out of Most of the chemical changes during storage involve
solution because of the decreased solubility at low oxidation and will be accelerated if beer is allowed any
temperature. contact with oxygen post fermentation.

Permanent haze is characterised by the more durable, The dissolved oxygen in beer rapidly disappears, although
irreversible covalent bonds. stale flavours may not develop immediately. However,
oxidative reactions will have been initiated which will
produce off-flavours subsequently.

Learning Material 2016 131

When oxygen has dissolved in beer, lipids (fats) derived be due to contamination, so presence of diacetyl in package
from malt are oxidised by enzymic and non-enzymic beer is not conclusive evidence of oxygen pickup.
reactions to a range of oxidised compounds, which
breakdown during the brewing process or in package to Oxygen as a constituent of air
form aldehydes. For example, in the presence of the Oxygen forms approximately 21% by volume of
enzyme lipoxygenase, and oxygen, linoleic acid is converted atmospheric air. The remaining constituents do not give
to trans-2-nonenal. These compounds have a very any real cause for concern as regards physical / chemical
unpleasant flavour. The flavour formed is often described degradation of beer.
as ‘stale, papery or cardboard’. This reaction is speeded up
at high temperatures. Thus the combination of high levels However, ingress of atmospheric air into beer also risks
of oxygen and pasteurisation is disastrous. microbiological contamination by airborne yeasts and
bacteria, giving a second reason for avoiding all forms of air
The development of “ribes” or “catty” off-flavours in beer is pickup.
classically associated with high dissolved oxygen content at
packaging (high headspace air). If the partial pressure of oxygen in the gas in contact with
the air is greater than the partial pressure of oxygen
In general terms, the rate of development of oxidised dissolved in the beer, oxygen will pass from the gas into the
flavours is inversely proportional to the strength of the beer beer in an attempt to equalise the partial pressures, up to
(alcohol content) and the content of coloured malts in the the maximum solubility of oxygen in water, approximately
original grist (higher level of reducing power). 10 ppm.
Consequently, strong stouts are much more flavour stable
than light coloured lagers. Lagers will develop sweet, It is essential that not only contact of beer with
papery/cardboard and metallic notes, whereas ales tend to atmospheric air is avoided, but contact with any other
develop molasses/toffee and dried fruit or sherry oxygen contaminated gas, typically CO2 or nitrogen, is also
characters. avoided, because the oxygen in these gases will also
attempt to reach equilibrium. Though the level of dissolved
Flavour Described as Approximate Typical Source oxygen reached will invariably be less than that attained by
term flavour concn in contact with atmospheric air, it can still be sufficient to
threshold beer
Diacetyl Butterscotch 0.05 – 0.2 0.01 - 0.4 By-product of encourage oxidation flavour changes and haze formation.
buttery mg/l mg/l amino
synthesis Typical points of exposure to air
Air, or air contaminated process gases (CO2, N2) contains
Caramel caramel, -------- -------- Oxidation with
/ Toffee treacle age
oxygen, so that any time the beer comes into contact with
air, or water containing dissolved oxygen, it will pick up
Contamination oxygen. The point of contamination is at the surface of the
of raw beer and this means that the larger the surface area, the
materials
more oxygen will be picked up. When the beer is agitated, a
Catty catty, tom- 15 mg/l -------- Oxidation with larger surface area is created and more oxygen can be
cat urine, age dissolved.
blackcurrant
leaves Contamination
of raw
• Impure process gases. This is a common problem
materials with old, or poorly run CO2 recovery plants. These
may be used as top pressure gas in tanks, or as
Iso- cheesy 1 mg /l 0.2- Old hops injected gas for carbonation or for nitro-keg products.
valeric 1.5mg/l
Lipid oxidation
• Pump seals, particularly the seal around the drive
Metallic tinny, blood- 1 mg/l <0.5 mg/l Contamination shaft.
like, inky
Oxidation
• Valve seals – again typically these draw air in when
Papery papery, 50-100 ng/l 50-0.2 µg/l Staling during on the low pressure, suction side of pumps, but leak
cardboard beer storage outward on the high pressure discharge side.
However, they can act rather like the fuel supply jet
Winey / Vinous, Oxidation
in a traditional carburettor, sucking air in through a
Sherry Madeira,
sherry small gap between the seal and the metal, or through
holes in the seals.

Additional note on diacetyl - may be apparent due to high • Joints, particularly between sections of main, or on
oxygen pickup post fermentation whilst still in presence of instrument housings on the suction side of transfer
active yeast, e.g. transfer from FV to MV. Alternatively may pumps.

132 General Certificate in Brewing

 • Non-deaerated water e.g. that used for CIP final The significance of sampling time
rinses. It is important to measure for DO2 immediately after
potential contamination by air, for example immediately
• Inadequately deoxygenated water used for flushing
after transfer into a tank. This is because oxygen is used up
out mains before and after transfers, or for diluting
in the oxidising process, so beer that has been transferred
high gravity beers.
then stood and allowed to oxidise could have a
• Poorly deaerated transfer mains or filters. If considerably lower dissolved oxygen level than freshly
insufficient time is given to flush out CIP rinse water, transferred beer.
or the flow rates are insufficient to achieve turbulent
flow, then pockets of gas or highly oxygenated water Tracking dissolved oxygen levels using in-line instruments
can remain. with suitable recorders allows quick tracing of problems, for
instance the oxygen spike that can occur when a valve
changes state or a pump is energised. These spikes can
make a large difference to the overall dissolved oxygen
12.2 Monitoring and controlling oxygen
level.
levels
It also allows alarm handling to be installed, so that no
Key control points product is produced out of spec.

DO2 levels will be zero in fermenting vessel at the end of Operating a dissolved oxygen meter
fermentation. All oxygen has either been used by the yeast
or purged out of the beer by the evolution of CO2 during Introduction
the fermentation.
There are two main types of oxygen meter now in use:
High DO2 levels in tank can be reduced by purging with an
inert gas like CO2 or nitrogen, but this could risk loss of beer • Electrochemical. This type of sensor has been in use
foam proteins by causing fobbing. since the mid 1970’s. Electrochemical cells consist of
a metal anode and a metal cathode dipped into an
Once the beer is in package, nothing can be done to electrolyte solution. When a voltage is applied,
improve out of specification DO2 levels. current flows between the anode and the cathode.
The electrodes and the electrolyte are separated
Thus it is useful to know on a regular basis, or at least have from the gaseous or liquid sample by a membrane
the ability to measure DO2 levels at the following points:- permeable to gas. Gas penetrating through the
membrane into the cell dissolves in the electrolyte. It
• In maturation tank. causes a measurable electric current to flow which is
• In the beer in line out of maturation tank (often at proportional to the amount of gas entering the cell,
the pre-filter buffer tank inlet). DO2 levels can rise at which in turn, is proportional to the amount of gas
tank changeover. dissolved in the sample.

• Pre filter – at the filter inlet. • Optical (quenching). This design has only been in use
in breweries since about 2008. An oxygen sensor
• Post filter at the filter outlet – to help determine
(sensor spot) is in contact with the liquid or gas for
effectiveness of the pre-filter run de-oxygenation
which the oxygen content is to be measured. The
flush, and oxygen pickup from any additives.
sensor spot is intensely illuminated by a blue light
• Post filter – again, often at the outlet of the buffer source for a short time. Depending of the oxygen
tank. content in the medium the sensor spot will give out a
red light signal. A detector measures the intensity of
• Pre and post dilution and carbonation. the light signal and from it the oxygen content of the
liquid or gas is calculated. Depending on the scan
• In bright beer tank.
frequency, accurate results from an optical sensor are
• At the inlet to the filler, especially if the supply obtained more quickly than electrochemical sensors.
system incorporates buffer tanks, pasteurisers etc.
Operating guidelines
• In final package – normally measure as TPO (Total in
Package Oxygen) as this measures the total of the Both may be used as in line or off line (typical hand held or
portion derived from the oxygen dissolved in the beer lab bench). Both types must be maintained and calibration
in the filler, and the portion derived from any oxygen checked regularly (cross check with other instruments),
in the headspace introduced as part of the filling though Optical sensors, which are a comparatively new
process. technology, appear to require less maintenance than
electrochemical sensors.
Learning Material 2016 133
In-line instruments should be installed in accordance with There are a number of ways of controlling DO2 pickup:-
the manufacturer’s guidelines.
• Flush plant and pipes through with de-aerated water
When not actively being used to measure oxygen content, before running the beer through.
the instrument must be switched off to reduce unnecessary
deterioration. • Maintain an inert atmosphere (CO2 or N2) in
maturation vessels and bright beer tanks.
When measuring the DO2 of a liquid, the liquid should be
flushed through the instrument at high flow rate to ensure • Ensure that any additions to beer are oxygen free. For
that any entrained air bubbles or rinse water is removed. example, use deaerated water to dilute beer and for
Once flushed through, the instrument should be switched mixing filter aid additions, and purge continuously
on. Typically, optical instruments will give an accurate with CO2 or N2.
reading as soon as switched on, and the first pulse of light
has been sent and measured. Electrochemical instruments • Ensure that recovered beer, yeast pressings etc. are
take longer, typically more than 30 seconds due to the time oxygen free.
required for the dissolve gas either side of the membrane
to reach equilibrium. Sometimes, it may be necessary to • Reduce the surface area where beer is in potential
leave the instrument on, flushing through with fluid for contact with air. Vertical tanks are best from this
several minutes until a stable reading is achieved. point of view than horizontal tanks.

After use, if they have been used to measure a liquid, the • Add oxygen scavengers to the beer. This may not be
instruments should be thoroughly rinsed out with cold possible, either due to legislation or due to customer
clean water (de-mineralised preferred, but not essential). concerns, and is an admission that other control
methods are not being effective.
Typical specified maximum levels
The following specs are based on current brewery good • Flush and counter pressure packaging containers with
practice, not necessarily the best achievable, as these are CO2.
generally only realistically achievable in large modern
• The presence of small amounts of air in cask
breweries. Note also that many (generally smaller)
conditioned beer is not so destructive because of the
breweries may not be able to achieve these specifications
activity of yeast.
either.
• Ensure plant is maintained to minimise risk of oxygen
Note that particularly at very low levels of dissolved oxygen,
pickup through pump, valve and other joint seals.
specifications must reflect the possible accuracy of the
instrument, and the sampling regime, so that although for • Design pipes and plant so that beer turbulence is
instance, zero ppb may be desired, to allow for instrument / minimised. This means graduated bends etc.
sampling error, a figure of say 10 ppb may be set.
• Fill tanks at a controlled speed (at just turbulent flow
• FV immediately prior to transfer not > 10 ppb through the mains – typically circa 1.5 m/sec) from
(often not even specified) the base.

• MV immediately after filling not > 100 ppb • Fill packaging containers with minimum beer
turbulence.
• MV immediately before transfer not > 50 ppb
• Monitor DO2 levels and take corrective action where
necessary.
• Bright beer tank (at high gravity) not > 100 ppb
The use of antioxidants / scavengers
• Bright beer tank (at sales gravity) not > 100 ppb
• Sulphur dioxide is added to products like finings.
• In final package (TPO) not > 150 ppb
• O2 scavenging materials can be incorporated into
• Deaerated water not > 10 ppb bottle crown seals, e.g. sulphite and/or ascorbate.

Good practices to avoid oxygen pickup Notes.

For a brewery that you are familiar with, write down details
Beer should be stored as cold as possible, ideally at 0ºC. of dissolved oxygen levels at the different stages of
The Arrhenius equation predicts that the rate of chemical production, and procedures for controlling them.
reactions double for every 10ºC rise in temperature.
Therefore to reduce the rate of deterioration, beer should
be stored as cold as possible (without freezing of course).

134 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 135

Section 13 Beer quality - microbiological contamination
13.1 Beer spoilage

Introduction

There are three main groups of contamination which can • Hoses, joint rubbers, gaskets, valve and pump
affect beer and the associated materials at any stage of the seals, and equipment used for manually handling
production process:- materials such as mineral salts must be made of
• Chemical. food grade material, resistant to scratching and
• Microbiological. breakdown by the materials being handled, or by
• Physical. the cleaning materials / temperatures.
• Allergens.
• Microbiological contamination, which is covered
There are a wide variety of sources of contamination, throughout the following sections.
including the following:-
Sources of microbiological contamination
• With the raw materials. Examples of this type of
Micro-organisms will thrive in the most inhospitable
contamination are:-
conditions. When they are deprived of their nutritional
o Pests such as weevils, moths or even rodents in
requirements, bacteria can often form spores which are
malt deliveries.
more difficult to destroy than the active live bacteria.
o Droppings from pests such as rodents.
Consequently, they can infect the beer from many different
o ‘Off flavours’ and aroma chemicals absorbed by
sources. The tables below identify the main sources of
filter aids.
contamination.
o Dust and debris in empty cans.
o Untreated surface water, nitrates or effluent in
Raw materials and packaging materials
the water supply.
o Loose or worn plant components. Source of Comment
o Allergens such as wheat germ for brewing grist. contamination
Water Brewing water in wort will be
These are monitored by identifying the most likely boiled as part of the process, but
contaminants and either inspecting the material additions later in the process (e.g.
before delivery or agreeing specifications with a dilution water), cleaning final rinse
reliable supplier and monitoring and reporting back water, pre and post beer transfer
that supplier’s performance. purging water, must all be sterile.

• Cleaning chemicals. Product may be contaminated Brewing materials All naturally grown material
by plant cleaning chemicals, such as CIP detergents (malt, hops & harbours micro-organisms. These
and sterilants, or chemicals used for adjuncts) are unlikely to be a problem where
environmental cleaning. added / used before wort boiling
as this kills all flora and fauna
• Oil or grease. Only a small amount of oil will spoil present in the wort run into the
a beer. It will taint the flavour and destroy the kettle (copper).
beer’s foam stability. Oil or grease can get into the
product via, for example, poorly maintained pump Pitching yeast Storage of yeast may allow growth
glands. Oil free gas including compressed air is of other micro-organisms already
essential for beer production and packaging. present in the yeast slurry. This is
a major problem because an
• The use of unsuitable material for plant or package contamination can proliferate
construction. Modern plant is generally throughout the brewery unless
constructed of stainless steel. However there are controlled by effective plant
different grades of steel available. Some of these cleaning and possibly acid
grades can corrode under certain brewing washing.
conditions (e.g. high chloride ion content in
brewing liquor tanks), and therefore may not be
suitable, even though classed as “stainless”.
Equipment manufacturing processes may also
make even suitable grades for stainless steel liable
to corrosion and creation of ‘bug’ traps.

136 General Certificate in Brewing

 Additives (filter aid The powders and liquids as Bright beer vessels Easy to clean because the beer in
etc.) supplied are unlikely to be the tanks is bright and is likely to
contaminated, but the additions be nearly sterile.
make-up and dosing process, and
the water used for mixing and Packaging plant Difficult to clean because of the
purging can be a source of complex pipework and the design
contamination. of the filler itself.

Packages New bottles and cans may

contain dust and debris.
Product
Returnable bottles, casks and
Source of Comment
kegs may be heavily
contamination
contaminated when returned
from the trade because they Wort Wort is a perfect medium for
contain small volumes of beer, micro-organisms to grown in.
which may have been in the However, it will be sterile after
container for a long time, boiling.
allowing any contaminants time
to grow on the remaining beer. Beer in process Beer will support micro-organisms
but in itself it is unlikely to be a
source of contamination. A more
Equipment likely source is the plant. Beer
from other breweries may contain
Source of Comment more, or different contaminants,
contamination and should be treated with
Brewhouse plant Wort chillers and wort mains are suspicion.
important because of the nature
of the wort, and high levels of Recovered beer Beer recovered from surplus
fouling experienced, particularly yeast can be a major source of
in the heat exchangers, which can contamination because often the
protect microorganisms if plant it has been processed in is
cleaning is inadequate. The wort not maintained to such high
is a rich medium for many micro- hygiene standards as say FVs. Any
organisms to grown in, rich in recycling operation needs special
sugars, proteins, minerals and care because of the possibility of
oxygen from the wort aeration / perpetuating an contamination.
oxygenation system.
Beer recovered from packaging
Fermenting Difficult to clean because of the operations is also a major source
vessels residue left by the yeast and of contamination.
hops. FVs are a major source of
contamination because of the
long time that the beer is in Environment
contact with them.
Source of Comment
Yeast handling This can be a source of contamination
plant contamination because of the Insects and other Storage areas for raw materials
nature of the yeast itself and the pests will encourage insects and other
complexity of the plant makes it pests such as rodents unless
difficult to clean. maintained in a hygienic
condition.
Maturation plant Easier to clean than FVs but there They will carry contamination and
is some yeast soil and again, the must be kept away from open
beer is in them for a long time. vessels.
Walls and floors Contamination can be picked up
Filtration plant Difficult to clean because of the from poorly maintained walls and
complex pipework and the design floors especially in open vessels.
of the filter itself.

Learning Material 2016 137

Aerobic growth
Stage
An aerobic organism or obligate aerobe is an organism that Unpitched wort
requires oxygen for growth, examples of which are: moulds
(malt, empty cans) and yeast ‘film formers’ (Pichia, Candida Infecting micro- Characteristics Effects on
Mycoderma, Hansenula) organism beer
Obesumbacteria. Grows along with Causes off
Anaerobic growth (Hafnia) the yeast in wort flavours
but dies off early (“parsnips”) in
An anaerobic organism or anaerobe is any organism that in the a very slow
does not require oxygen for growth. For practical purposes fermentation. fermentation.
there are three categories:
• Obligate anaerobes, which cannot use oxygen for Presence
growth and are even harmed by it. indicates
• Aero-tolerant organisms, which cannot use oxygen ineffective wort
for growth, but tolerate the presence of it. main or FV
• Facultative anaerobes, which can grow without cleaning.
oxygen but can utilize oxygen if it is present.
Very common in
Brewing yeasts are facultative anaerobes, requiring oxygen top-fermenting
for healthy growth, but metabolise anaerobically during yeasts but less
fermentation. Most contaminating micro-organisms in common in lager
breweries are either aero-tolerant or facultative. yeasts.

Spoilage products and effects on beer quality Escherichia Grows in wort or

partially
For convenience, these two sub topics have been included fermented beer.
in the following main topic. Is an indicator of
contamination of
water supplied to
13.2 Spoilage organisms brewery.

The principal categories of spoilage organisms Enterobacter They do not grow Can produce
below pH 4.3. DMS and
There are four main microbiological contaminants to diacetyl, and
consider:- They are flavours
generally unable described as
• Bacteria. Very small living organisms of which to grow in beer “herbal
there are many varieties. Fortunately only a but grow rapidly phenolic.”
limited range will grow in beer and ‘pathogenic’ in wort. Some
organisms (those that could give food poisoning) can metabolise Can result in
will not. nitrates to nitrites increase in
so increasing nitrosamines.
• Wild yeast. Small living organisms similar to, but nitrosamines,
different from the yeast that is used to ferment particularly in
the beer. The difference being that wild yeasts will lauter and mash
give quality problems, for example flavour or fining tun residues
difficulties.

• Fungi or moulds.

• Water born organisms. Usually bacteria associated

with contaminated water.

The following is a list of common contaminating micro-

organisms, the stage of the brewing process they are most
likely to be found, and the effects of contamination.

138 General Certificate in Brewing

Stage Wild yeast Abnormal
Pitching Yeast flavours
(possibly
Infecting micro- Characteristics Effects on beer acetic acid)
organism and cloudy
Pediococcus Will also use Produces lactic beer. May
any sugar left acid and diacetyl. form a film on
after Beer goes cloudy beer surface.
fermentation. and tastes sour, Over
and smells of attenuates.
sour milk or
honey. Beer may Stage
go glutinous and Maturation
“ropey”.
Infecting micro- Characteristics Effects on
Lactobacillus Will also use Produces lactic organism beer
any sugar left acid and diacetyl. Pediococcus Will also use any Produces
after Beer goes cloudy sugar left after lactic acid and
fermentation. and tastes sour, fermentation. diacetyl. Beer
and smells of goes cloudy
sour milk or and tastes
honey. sour, and
Wild yeast Abnormal smells of sour
flavours milk or honey.
(possibly Beer may go
acetic acid) glutinous and
and cloudy “ropey”.
beer. May Lactobacillus Will also use any Produces
form a film on sugar left after lactic acid and
beer surface. fermentation. diacetyl. Beer
Over goes cloudy
attenuates. and tastes
sour, and
smells of sour
Stage
milk or honey.
Fermentation
Wild yeast Abnormal
Infecting micro- Characteristics Effects on beer
flavours
organism
(possibly
Pediococcus Will also use any Produces lactic
acetic acid)
sugar left after acid and
and cloudy
fermentation. diacetyl. Beer
beer. May
goes cloudy and
form a film on
tastes sour, and
beer surface.
smells of sour
Over
milk or honey.
attenuates.
Beer may go
glutinous and Zymomonas Cloudy beer,
“ropey”. bad egg
aroma.
Lactobacillus Will also use any Produces lactic
sugar left after acid and
fermentation. diacetyl. Beer
goes cloudy and
tastes sour, and
smells of sour
milk or honey.

Learning Material 2016 139

 Stage Pectinatus Obligate Bad egg
Bright and Packaged Beer anaerobe. aroma,
Produces vinegary.
Infecting Characteristics Effects on beer considerable Cloudy beer.
micro- amounts of acetic
organism acid and H2S.
Pediococcus Will also use any Produces lactic
sugar left after acid and diacetyl. Wild Yeast
fermentation. Beer goes cloudy The table below lists the main wild yeasts encountered in a
and tastes sour, brewery and effects that they have on the product:
and smells of sour
milk or honey. Yeast Effect on wort or beer
Beer may go
glutinous and Pichia Grows rapidly in the presence of
“ropey”. air.

Lactobacillus Will also use any Produces lactic Forms a film on the surface of the
sugar left after acid and diacetyl. beer.
fermentation. Beer goes cloudy
and tastes sour, Candida Grows rapidly in the presence of
and smells of sour mycoderma air.
milk or honey.
Forms a film on the surface of the
beer.
Acetobacter Most common in Produces acetic
cask conditioned acid in presence Saccharomyces Continues to ferment all
beer. Grow very of air, and forms a diastaticus carbohydrates so there is no
quickly even at low skin on the control of attenuation.
pH. surface of the
beer. Beer goes Also causes off flavours.
cloudy and tastes Torulopsis Fails to sediment and causes
of vinegar. hazes.
Zymomonas Convert sugar into Beer goes very Brettanomyces Very slow growing but it
alcohol, cloudy and smells produces acid and causes off
acetaldehyde and of bad eggs. Beer flavours. Note that some beers
hydrogen sulphide. may go glutinous are intentionally pitched with
Grow quickly in and ‘ropy’. Brettanomyces cultures to
liquid sugars. produce specific desired flavours,
Sometimes but these flavours are not
associated with considered desirable in the
‘primed’ beers. majority of beers.
Megasphaera Obligate anaerobe “Baby sick” and Hansenula Grows rapidly in the presence of
that thrives in bad egg aromas. air.
extremely low DO Cloudy beer.
levels found in Forms a film on the surface of the
modern bright beers; beer.
often associated
throughout the
brewery with Cross contamination of pitching yeasts
biofilms. Produces Cross contamination of brewing yeast strains, for example a
considerable lager yeast contaminating an ale yeast, is normally
amounts of butyric considered as a wild yeast contamination, because quality
and caproic acids problems such as abnormal flavours or an inability of the
and H2S. yeast to settle or fine properly may be experienced.
Moulds/ Fungi
Moulds or fungi do not normally grow in beer because they
need air. However they can affect beer in a number of
ways:-

140 General Certificate in Brewing

 • The malting ability of barley can be affected by the
presence of mould.

• Some moulds which grow on / in barley can cause

gushing (explosive gas breakout when a highly
carbonated package is opened), e.g. fusarium, or in
other cases (rare) are poisonous (ergot).

• Moulds will grow in empty beer packages (e.g.

bottles) and in poorly cleaned plant. If this
happens and the mould is not completely removed
during washing prior to filling, the mould will
probably affect the flavour of the beer.

Mouldy surfaces in buildings like fermenting rooms are Lactobacilli

difficult to clean and visible growths will harbour beer
spoilage yeasts and bacteria.
Photomicrographs of wild yeast and contaminated culture
Water borne organisms yeast

Water borne organisms are not very common but can cause
serious problems.

Pathogenic bacteria that will not grow in beer will,

however, grow in water.

• The presence of Escherichia or Enterobacter may

indicate that the supply is contaminated with
untreated surface water or even sewage. Further
investigation is recommended.

• Both Escherichia and Enterobacter grow readily in Wild yeast

unfermented wort causing flavour problems when
in high numbers.

• Legionella can cause serious illnesses. Usually the

bacteria are transmitted when the water is in a
mist form, for example from cooling towers (see
Section 18, utilities).

Samples are examined using a microscope. The following

show a few examples of micro-organisms.

Photomicrographs of typical bacteria found as brewing

contaminants.
Brewing yeast contaminated with wild yeast

13.3 Detection and monitoring

Methods of sampling

It is important to know the microbiological condition of the

production plant, the product in process and of the raw
materials. It is difficult to detect micro-organisms since they
are not visible to the naked eye. Micro-organisms grow
very rapidly in the correct condition therefore only a very
small population of them is a potential risk. By the time
they are noticed as haze or flavour taints, the
contamination is already fully developed. But identifying a
Pediococci (note the commonly seen tetrads)

Learning Material 2016 141

small population is nearly impossible especially in a large • Forcing. This is where a bulk sample is taken, and
volume of beer. This knowledge that the beer is the growth of micro-organisms is accelerated by
contaminated can be used to improve the cleaning or culturing at relatively high temperatures, circa
o
production process as required. 30 C for 3 to 5 days, for rapid growth. The sample
may or may not have additional nutrients added
It is therefore necessary to develop methods of detecting prior to forcing, to encourage growth of the type
micro-organisms at a stage before they develop into a of microbe being looked for. The conditions may
problem. This is achieved by: be aerobic or anaerobic, according to the needs of
the microbe being looked for.
• Visual examination - samples can be examined
with the naked eye or viewed under a microscope. • API analysis. This is a commercially available
o Samples that have micro-organisms growing in method for rapid manual identification of yeasts
them will usually be cloudy and an experienced and Gram positive and Gram negative bacteria.
person can tell from this if there is a problem.
Also colonies can be seen on plates on which Beer for microbiological analysis can be sampled in a
micro-organisms are growing. number of ways. These are shown in the table below along
with the procedure’s advantages or disadvantages:-
• In order to carry out a detailed examination using
forcing / plating / microscopic examination, it is
necessary to take a suitable volume of Sample Sampling Comment
representative sample which must be obtained point procedure
using aseptic techniques to ensure it is Sample tap Tap is sterilised, Easy to operate.
uncontaminated by micro-organisms outside the in a tank usually by heat. The tap is difficult
bulk of material being sampled otherwise a false to sterilise.
result is given. In aseptic sampling, the sampling Sample is run into a
sterile bottle. The tap needs to
equipment and the sample bottle are all sterile.
be cleaned when
• Using ATP tests. The ATP test is a process of the tank is
rapidly measuring actively growing cleaned.
microorganisms through detection of adenosine
Membrane A sterile needle is The membrane is
triphosphate. ATP is a molecule found in and
sample inserted into the easily cleaned
around living cells only, and it gives a direct
point in a membrane. when the tank is
measure of biological concentration and health.
tank cleaned.
ATP is quantified by measuring the light produced
Sample is run into a
using a luminometer. The amount of light The membrane
sterile bottle.
produced is directly proportional to the amount of needs to be
living organisms present in the sample. replaced
regularly.
• Inspecting the sample through a microscope and
identifying the foreign organisms (but often only Aseptic The valve body is
useful after the micro-organisms have been sample arranged so that
grown). valve, e.g. the internal
o More detail can be seen under the microscope Keofit sampling area can
as micro-organisms have different shapes and be sterilised before
an experienced microbiologist can identify use.
them.
o A useful technique is to stain the sample to be When the valve is
examined, some bacteria take on the stain, closed it is possible
others do not. A Gram stain colours ‘Gram to pass sterilising
positive’ bacteria like lactobacillus. liquid through the
top sample point
• Encouraging the micro-organisms to grow (with
and out through
enriched media) so that they can be more easily
the bottom. This
detected and identified by plating out on growth
sterilises the entire
media and counting the colonies which grow. By
internal surface of
using a range of selective growth conditions, the
the valve.
micro-organism can be identified with sufficient
accuracy to enable the brewery hygiene to be
controlled at optimal cost. The conditions may be
aerobic or anaerobic, according to the needs of the
microbe being looked for.

142 General Certificate in Brewing

 Continuous A sample is Representative of • Design of plant for maximum hygiene and ease of
sampling continuously the whole batch cleaning.
from a ‘dripped’ into a of beer.
• Effective plant cleaning and sterilisation,
process line sterile bottle from a
housekeeping.
sample point in, for
example a filter • Product and raw material sterilisation, e.g. wort
line. boiling, sterile filtration, pasteurisation.
Swabbing The plant is Access to plant
checked by rubbing not always • Creating conditions that inhibit microbiological
with a sterile swab, possible, growth, e.g. cold storage, low beer pH, acid
normally wetted especially in large washing of yeast, pasteurisation, filtration, regular
with saline automated fresh yeast cultures.
solution. breweries.
• Monitoring microbiological quality.
Sometimes the The area being
saline is added swabbed needs to Plant design
after swabbing. be of consistent Micro-organisms will persist on rough surfaces, in corners
area and and it the ‘dead ends’ of pipework. The plant should be
The saline solution consistent designed (e.g. smooth surfaces, no dead ends, cleanable
is normally plated location every pumps) to eliminate these problems (for more detail see
out using agar time that item of Section 16).
growth media. plant is sampled.
Plant cleaning and sterilisation
Rinse Samples of the final Can be difficult to The principles of effective cleaning are to remove soil and
samples drainings of the obtain aseptically. micro-organisms from the plant surface and then, if
final rinse water, or Provides a necessary sterilise to kill any remaining harmful bacteria or
flush water are snapshot of the yeast, (for more detail see Section 15).
taken. hygiene at the Good housekeeping and environmental cleaning form an
time of the final essential part of creating hygienic brewing conditions.
rinse, but not
necessarily say 48 Product sterilisation
hours later when • Wort is boiled in the brewhouse. One of the
the plant is used. reasons for doing this is to sterilise it.

• Beer for packaging is often sterile filtered or

Sampling points pasteurised to improve microbiological stability.

When beer is contaminated, it is usually necessary to • Beer recovered from surplus yeast or from
identify the responsible organisms. It is to routine to check packaging operations is often sterile filtered or
for microbiological contamination throughout the brewing pasteurised to improve microbiological stability.
process:
• Pitching yeast is sometimes acid washed to kill off
• Water and raw materials. any contaminating micro-organisms. Bacteria are
more vulnerable to acids because they have
• All products and additions made to the wort and thinner cell walls.
beer.
Soak baths
• Wort and beer in process. Soak baths may be used to maintain the sterility of small
fittings, such as swing bends and hoses when not in use for
a production process. However, it is preferable to clean
• Hygiene and cleanliness of all vessels and
hoses and fittings as part of a CIP circuit and leave
pipework.
connected and isolated, full of sterilant or sterile rinse
liquor unless in use. Key procedures for maintaining their
• Beer in package.
effectiveness include:-

• Regular replacement of the sterilising solution with

13.4 Control fresh sterilant solution.
Practices to protect against contamination • Removal of the hoses and fittings prior to cleaning
There are 5 main considerations in achieving a high and then refilling the bath with fresh sterilant, and
standard of micro-biological control:- rinsing prior to replacement.
Learning Material 2016 143
 • Thorough rinsing out of hoses and fittings prior to Where a batch of product, whether raw material or product
submersion in the sterilant solution. in process, including yeast, wort, beer, is known to be
contaminated, then the priority is to prevent that batch
• A schedule of replacement and regular checks to from contaminating any other batches. Then, identify
ensure the solution is being replaced properly. where and why the contamination has arisen. Any or all of
• Correct placement of hoses and fittings in the soak the following actions may then be required to eliminate the
bath to ensure there are no trapped air bubbles. spread of any contamination and to prevent re-
Unless the sterilant is contact with the fitting, it introduction:-
cannot sterilise / keep the hose / fitting sterile.
• Disposal of the contaminated batch without
• Do not allow the soak bath to be overloaded. All further processing.
hoses / fittings must be fully submerged at all
times. • Cleans before and after transfer of the
contaminated batch.
• Ensure the hose linings are crack free.
• Disposal of contaminated yeast. Acid washing
should not be considered a suitable process for
Conditions that inhibit microbiological growth eliminating all bacterial contamination and will not
Micro-organisms have optimum conditions for growth. kill contaminating wild yeasts.
Where possible, beer is kept in conditions that inhibit their
growth. This means as low a temperature as practicable, • Special cleans, for instance to remove beer stone
close to minus 1°C. pH values in the range 3.6 - 4.4, typical that has built up without prior knowledge.
of most beers, will inhibit the growth of many bacteria.
• Maintenance of equipment to stop leakage, or
The same principles apply to yeast during its storage, but ingress through faulty seals, pin hole leaks etc.
normally this is stored slightly warmer at circa 3°C.
• Change of detergent or sterilant as sometimes
micro-organisms can become resistant to
Measures to combat known sources of contamination
sterilants.
The measures to combat known sources of contamination
• Increase in detergent or sterilant strength if found
are virtually the same as practices to protect against the to be below recommended concentrations.
spread of contamination.
• Increase in temperature of detergent / sterilant.
• Monitoring microbiological quality – to identify
when and where contamination is present. • Review of cleaning cycle times.
• Design of plant for maximum hygiene and ease of
cleaning, e.g. smooth surfaces, no dead ends, and
cleanable pumps. Notes
• Identify the areas in a plant that you are familiar
• Effective plant cleaning and sterilisation, good with where microbiological contamination is most
housekeeping. likely.
• Specify the micro-organisms that cause problems
• Product and raw material sterilisation, e.g. wort in a brewery that you are familiar with.
boiling, sterile filtration, pasteurisation. • What problems do they cause and how are they
eradicated?
• Creating conditions that inhibit microbiological • View a sample of yeast under the microscope at a
growth, e.g. cold storage, low beer pH, acid range of magnifications and draw what you see.
washing of yeast, pasteurisation, filtration, regular • Give details of the procedures used to combat
fresh yeast cultures. microbiological contamination in a brewery that
you are familiar with.
• Give details of the microbiological sampling
procedures and schedules in a brewery that you
are familiar with.

144 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 145

Section 14 Quality Assurance and Quality Management

14.1 Quality Management

Candidates should have an understanding of the The theory being that ‘if it isn’t written down, it isn’t done’.
fundamental principles of Quality Management and be
familiar with the methodology of at least one quality It is important that documents are ‘controlled’ so that
system appropriate to their region/country of operation. people are confident that the document they are working
to is current and valid.
The Key Features of a Quality Management System are:-
(d) Monitoring.
• To understand precisely what is to be achieved. Quality performance is monitored on a regular basis and
the results can be presented in a way that highlights
This means having specifications to meet and it means problems.
having procedures to follow.
(e) Auditing.
This also means that the procedures and specifications The purpose of auditing is to check that the quality system
will have to be documented. is being followed.

Audits are concluded with a report back which usually

• To monitor actual performance against what is to be
identifies areas for improvement.
achieved.
Auditing procedures have the advantage that they can be
This means keeping records of performance and it
conducted internally.
means auditing.
Audits do not necessarily have to cover the whole quality
• To correct things when they go wrong.
system, often following a trail of evidence will reveal how
rigorously procedures are being followed.
This means having a system of initiating corrective
action. (f) Corrective Action.
Action must be taken to put things right and how this is
• To review the overall quality management system and
done is usually covered by a procedure.
to plan for improvement.
The procedure will ensure that the following areas are
covered:-
(a) Specifications.
Process and product specifications must detail all those • Detail of the problem.
parameters that are required to be measured, including
flavour, and they must identify an ideal value together with • Nominating the person responsible for taking the
an acceptable range for each parameter. action.

(b) Procedures. • When the corrective action will be completed.

Documented procedures are there to explain what has to
be done and when and how it should be done. Procedures • A review of the result of the corrective action taken.
can cover a wide range of topics:-
(g) Review.
• An explanation of the organisation and responsibilities. An overview is required so that it can be confirmed that, for
example:-
• Procedures to be followed in the case of non-
conformances. • Corrective actions are being followed (implemented) in
time.
• Procedures on how the processes are managed.
• Audits are taking place as specified.
• Instructions on how to operate the plant.
• The brewery’s quality is meeting requirements.
• Procedures to be followed when auditing.
The procedure for a review is specified and documented in
(c) Documentation. the same way as all other procedures.
Quality management systems rely on documents to ensure
that procedures are followed.

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(h) Improvement. 14.2. Roles and Responsibilities and
It may be that an overall improvement in quality is Benefits
required; many world class manufacturers have a ‘zero
defect’ policy. Individual Actions on Product and Service Quality
In this case a plan to achieve the required improvements is
Quality is the responsibility of everyone working within an
necessary. The quality management system will contain all
organisation. However, the following actions are required
the specification and monitoring procedures to enable an
of a quality system:-
improvement plan to be implemented.
• It is the responsibility of top management to formulate
the Company’s quality policy and to ensure
Total Quality Management (TQM) commitment at all levels to comply with the Quality
System and to improve its effectiveness.
A good quality system includes:-
• Communication to all members of staff so that all
• Motivated and well trained workforce. understand it and are involved with its
implementation.
• Well maintained plant.
• All staff members responsibilities and level of authority
• Adequate capacity for peak demand.
should be defined and understood.
• Good plant cleanliness and housekeeping.
• A management representative should be appointed as
• Sufficient time for operations, cleaning and Quality Systems Manager, responsible for:
maintenance. o managing the requirements of the quality
standard
• Good relationships between suppliers and customers. o issuing amendments to manuals
o arranging audits
o checking suppliers
Typical Quality Management Systems include: o taking minutes of quality meetings
o investigating problems and initiating corrective
• ISO 9000 - Quality Management. actions
• ISO 14000 - Environmental Management. o following up corrective actions
• GMP - Good Manufacturing Practice. o handling complaints
• GLP - Good Laboratory Practice.
• NAMAS - National Accreditation of Measurement The Control of Documents
and Sampling.
• HACCP - Hazard Analysis Critical Control Points. All quality systems require control of documentation. It is
necessary to identify controlled documents (i.e. updated)
Notes. and uncontrolled documents.
Give details of a quality management system that you are
aware of. • Examples of Controlled documents include:-
o Quality Policy
o Quality Manual
o Procedures
o Work Instructions
o Specifications
o HACCP systems
o Codes of Practice

• Controlled documents must be:-

o approved before issue
o reviewed and updated
o changes identified
o up-to-date
o legible
o external documents also controlled
o obsolete documents removed

• Document control is usually achieved by:-

o issuing on coloured paper or including colour
logo

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 o no photocopying Benefits
o uniquely identified
o pages numbered (e.g. Page 1 of 10) The control of quality through a ‘Quality System’ gives the
o maintaining distribution list of holders following advantages over a ‘Final Inspection’ approach:-
o ensuring documents are not issued without
authorisation • The use of documented procedures and specifications
o only being available to staff who need to use ensures that everybody knows what they are supposed
them to be doing.
o limiting number of copies issued
• The responsibility for quality sits with the people who
• Document change is controlled by:- are operating the plant and making the beer.
o approval of changes before issue
o issue of an amendment sheet so that changes • Quality problems will be identified as soon as they occur
are identified rather than much later when the process is over.
o keeping a master list of document numbers to
ensure all staff use up-to-date copies Maintenance of accurate records makes it easier to track
o retrieval of obsolete copies as replacements back and investigate raw materials or processes so that
issued ‘due diligence’ in manufacturing can be proved.
o archiving one copy

The Maintenance of Conformity 14.3 Product Safety

Adherence to a well-established quality system will ensure HACCP - Hazard Analysis, Critical Control Points
that conformity of product quality and company operation
is maintained. HACCP is a programme that provides food manufacturers
with a systematic approach to address possible sources of
However, all quality standards strive for improvement and contamination of foods and beverages that could adversely
this is often best achieved by regular management reviews affect human health.
of the quality system and appropriate communication to all
staff, especially for changes to systems and regulations. The concept was developed by NASA in the 1960s as part of
research into ‘astronaut well-being’ for the American space
Regular quality review meetings should: programme, and more recently has evolved for the general
• review the Quality Policy and Quality System at defined food industry. HACCP, or its international version, iso
intervals (at least annually). 22,000, is now universally recognised by key legislative
bodies as the internationally accepted food safety standard.
• be additional to departmental or section quality The global brewing industry is obliged, both legally and
meetings. morally, to provide safe and wholesome products for
consumption and to assure food safety throughout the
• be chaired by senior management.
supply chain.
• include QA staff, production managers, auditors,
purchasing staff. There are three types of hazard, namely chemical, physical,
allergens and microbiological; it is important to note that
• review the operation of the quality system. hazards directly affecting quality, with no consumer safety
implications. are not part of HACCP. Given that beer
• ensure the policy and system are suitable and effective. contains ethanol, and has a relatively low pH, and has
limited available nutrient, the potential growth of any
• recommend changes. pathogenic organisms (harmful to human health) is limited,
with only a few issues deriving from mycotoxins produced
• record actions and responsibilities. by certain moulds and specific flavour compounds
produced by certain wild yeasts. However, contamination
• meeting agenda should include:
at successive stages of the process by various foreign
o audits (internal and external)
bodies and chemicals such as detergent or coolant is a
o process performance
viable risk that needs to be addressed and controlled. The
o complaints
HACCP programme thus developed will address risk by
o preventative and corrective actions
prevention rather than by final product inspection.
o changes
o training needs
Most countries have legal requirements for manufacturers
o supplier performance
to supply food that complies with food safety requirements
o future developments
and is of the nature, substance and quality demanded. Food

148 General Certificate in Brewing

safety regulations demand that suppliers consider the Step 2 Preparation and verification of the Process Flow
potential food safety hazards throughout their operation, Diagram
identify those steps where such hazards may occur, and put
in place at these points monitoring and control procedures The flow diagram is a detailed description of the process
for any hazards deemed ‘critical’. Other reasons to adopt a under study produced by the team to enable them to
HACCP approach include customer expectations, cost identify any process hazards whilst conducting the analysis.
control, especially in the prevention of product recalls, The diagram must show each process step in sequence and
product integrity, and the need for accreditation to external indicate clearly each material addition and service. The
auditing bodies. HACCP team should verify the flow diagram for accuracy by
walking the process with the associated operational teams
A HACCP system consists of two main parts, namely and checking any relevant documentation (work
individual HACCP studies on each separate process or instructions, engineering drawings etc.)
production line, and so-called ‘prerequisite programmes’
normally contained within the mantle of Good Step 3 Hazard analysis and identification of controls
Manufacturing Practice (GMP), covering elements such as
Pest Control, COSHH, personal hygiene, workwear The team should consider in turn each of the constituent
standards, equipment design, plant CIP, preventive process steps detailed on the flow diagram and conduct a
maintenance programmes etc. hazard analysis to establish which hazards are present and
if they present a risk to the consumer. Each hazard
The HACCP process consists of nine essential steps (some detected should be ranked in terms of’ ’risk’ on a scale of 1-
companies base their processes on seven steps):- 3 according to:-

• Agreeing the scope of the study. • Impact on the consumer (1= minor aversion; 3=
serious injury/illness or even fatality).
• Conduct a hazard analysis by constructing a flow- • Likelihood of occurrence (1=remote, single batch
diagram of the various process steps. affected ; 3 = multiple batches affected).

• Listing the hazards, rank them in order of ‘risk’, Hazard (Risk rating) = Impact x likelihood/probability, hence
specify any control measures. multiplied score can range from 1 to 9. Any hazard scoring 3
or more is deemed significant and should therefore be
• Determine any critical control points. included in the HACCP study as a critical control point (CCP),
the team identifying the appropriate ‘control’ to reduce the
• Establish critical limits. risk to an acceptable level and document it in the study.

• Set up monitoring of limits at each CCP. Step 4 Establish any CCPs by using a decision tree which
asks four key questions, viz:
• Establish any corrective actions.
• Are control measures in operation at this stage?
• Set up documentation and record-keeping • Does this stage eliminate the hazard or reduce it to
systems. an acceptable level?
• Could contamination with the hazard occur at an
• Set up procedures to verify that the HACCP plan is unacceptable level?
working effectively. • Will a subsequent process stage eliminate the
hazard or reduce it to an unacceptable level?

In order to conduct an effective HACCP study, a multi- If the answers to these questions are respectively either:-
disciplined audit team involving operators, managers and
technologists, must be assembled, containing the necessary Yes, Yes, or
engineering, technical and practical knowledge of the area
to be covered by the study. The team leader should be Yes, No, Yes, No
qualified or experienced in HACCP principles.
Then the hazard point is a CCP.
Step 1 Define the scope of the HACCP study, i.e.
Step 5 Establish critical limits for each CCP.
• The extent of the process covered, e.g. canning
line from BBT outlet to ’ full can’ warehouse store The critical limits define the difference between a ‘safe’ or
• Product description and its intended use ‘unsafe’ process, so if the limit is exceeded, the process is
• Types of hazard considered, i.e. physical, chemical, out of control and the safety of the product is
microbiological compromised. For example, the critical limit for a trap filter
• Description of any prerequisite programmes

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on the beer supply line to the can filler is “filter of correct Step 9 implementation, verification and review
mesh size in place and checked weekly for security and
integrity” Such Critical Limits are simple to install and Having documented all the CCPs and their ensuing critical
thereby implement corrective action. limits, monitoring and corrective actions, the appropriate
responsible people must be trained. Verification procedures
Step 6 Establish monitoring for each CCP should then be established to ensure that the controls
implemented are sufficient to manage any risks identified.
The monitoring procedure must state:- An example is a regular review of small-pack consumer
• The frequency of monitoring. complaints, where the incidence of flavour defects and
• The person responsible for carrying out the foreign bodies will serve as a measure of the effectiveness
monitoring. of ‘chemical’ and ‘physical’ CCP control on small-pack
• The monitoring procedure. production lines . A review of the HACCP plan should occur
at least annually, together with auditing of the CCP
The frequency of monitoring is such that any loss of control monitoring and corrective actions.
of a CCP is detected and rectified before any product
deemed at risk leaves site: for example, putting a series of
test bottles weekly through the empty bottle inspector (EBI) In summary, HACCP is all about:-
on a bottling line would require quarantining of a week’s
production should the test fail. As ever, all monitoring • Meeting legal, customer and consumer
results should be recorded. requirements.

Step 7 Set up any necessary corrective actions • Preventing the risk of illness or injury to
consumers.
When a critical limit is exceeded appropriate ‘corrective
action’ needs to be implemented to bring the CCP back into • Ensuring due diligence and avoiding liability.
control: it must stipulate ‘what to do’ both to restore the
CCP to control and to deal with any affected stock produced • Saving money.
since the last ‘good’ monitoring result. Again, all corrective
actions should be documented. As an example, any stock at • Preventing brand damage.
risk because of an EBI test bottle failure should be
quarantined by the team leader, ‘sorted’ for possible glass
defects, the test bottles checked, the test re-run
immediately and any sources of potential defects within the
empty bottle supply to the EBI highlighted and eliminated
before production resumes.

Step 8 Create appropriate documentation and records

Each study should yield a HACCP plan, defining hazards,

causes, risk rating, control, monitoring and corrective
actions, which can serve both as a work instruction and a
training document.

150 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 151

Section 15 Plant Cleaning – Detergents and Sterilants

Plant cleaning - Introduction • ‘Clean conditions’ are defined as those following the
removal of all soils but not all vegetative cells. Thus the
The objective of any cleaning and sanitising programme is higher the required degree of cleanliness the more
the control of microbiological growth. robust the cleaning process has to be, and the more
important it becomes to ensure that the plant is
Growth control can be effected by:- designed for effective cleaning.

• limiting microbial growth by the removal of • ‘Hygienic conditions’ for brewing and other beverage
nutrients or protective materials and films in the plants are defined as a degree of cleanliness which has
forms of scales and biofilms (cleaning). been achieved by elimination of vegetative forms of
life, making it suitable for most aspects of beer brewing
• by removing all viable microbes by either total or other beverage production.
removal (sterilisation) or removal of vegetative
cells only (commonly known as sanitisation) by the • ‘Disinfection or sanitisation’ may be defined as the
application of agents (e.g. biocides) to kill microbes destruction of micro-organisms, but not usually
or by the application of agents that, in continued bacterial spores. It does not necessarily kill all micro-
presence, prevent growth (e.g. bacteriostats). organisms, but reduces them to a level acceptable for a
defined purpose, i.e. a level which is harmful neither to
Typically, control measures follow the cycles of:- health nor to the quality of perishable goods (in this
case beer, cider etc.).
• soil removal (or cleaning).
• ‘Sterilisation’ is defined as the elimination of all forms
of life including microbial spores. Typically this is most
• disinfection or sanitisation (chemical agents or effectively achieved with live steam at a minimum
heat) to prevent growth or eliminate viable temperature of 122°C for a contact time of at least 15
microbes. minutes. These conditions are found most typically in
the pharmaceutical manufacturing environment, but in
• sterilisation to prevent the growth of any surviving breweries most commonly in a microbiological
organism including spore formers (by use of laboratory autoclave for preparing growth media, etc.
chemical agents or heat) thus preventing spoilage.
(b) Detergents
The purpose of cleaning is to remove permanently all the
soil from the surfaces of the plant and to leave it in a A detergent is a blend of chemicals, which is put together to
condition suitable for use. help solubilise soil, remove it from the surface and ensure
that it does not re-deposit itself back on the cleaned
The purpose of sanitisation or sterilising is to kill any micro- surface.
organisms that remain on the internal surfaces of the plant
after cleaning so that the wort, beer or yeast is not spoiled
due to infection by any remaining viable organisms. (c) Sterilants (sanitisers)

(a) Microbiology of Cleaning Sterilants (sanitisers) are formulated to kill microbes and
bring micro-organism load to an acceptable level and work
The degree of cleanliness required for a processing plant is by:-
defined by the potential impact of the soil or microbes on
the resultant product. This is largely determined by the • Creating the conditions of temperature, pH, chemical or
type of product being produced in that particular plant. surface activity that destroy (kill) micro-organisms.

Products that are sensitive to spoilage require higher 15.1 Detergents

degrees of cleanliness (hygiene) than those that are not as
susceptible; therefore knowledge of the products Detergents help the cleaning process by:-
propensity to spoil is essential in determining an
appropriate cleaning sequence. • Penetrating the soil, usually by increasing the wetting
power of the cleaning liquid.
This may or may not include a sanitisation / sterilisation
step.
• Dissolving soluble soil material.

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• Dispersing insoluble soil and holding it in suspension so There are two main types of soil that need to be removed
that it does not re-deposit. from the surface of brewing and packaging plant:-

• Carrying the soil away as the cleaning liquid is rinsed off. • Organic soil which includes yeast, protein, fat and
sugar. Plant which has a lot of organic soil that
A detergent is made using an acid or an alkali as the basis. needs to be removed should be cleaned with a
Therefore the chemical properties of the detergent are detergent that contains compounds that can
acidic or alkaline. dissolve it. Alkalis like caustic soda dissolve
organic soil and caustic solutions are often used to
In a brewery, the organic soils are best removed using an clean fermenting vessels and brewhouse plant.
alkaline cleaner. Acids are used to remove inorganic
deposits such as hard water deposits. • Inorganic soil which includes hard water scale and
‘beerstone’. Plant in some breweries becomes
Formulated detergents used in the beverage industry scaled up quite quickly, especially in hard water
comprise:- areas. This plant needs to be cleaned regularly
with a detergent that dissolves scale.
• A base dissolving material, which is either alkali or
acidic. These form the main dispersing agent of Caustic & other alkalis
the detergent. Caustic detergents are made of caustic soda (sodium
hydroxide) as the main ingredient. Caustic or alkali
• Surface active molecules as wetting agents detergents can be chlorinated.
(surfactants).
To clean surfaces where caustic is not allowed, detergents
• Chelating agents or sequestrants. are used which use sodium metasilicate as a base.
Sometimes soda ash or phosphate salts are used as alkali
• Rinsing agents. source with builder (sequestering) properties.

• Oxidising agents (sometimes). To deal with stubborn dirt, chlorinated caustics or

chlorinated alkalis are sometimes used. The amount of
Constituents of detergents and their functions available chlorine of the working solution should not
exceed 200ppm, and the pH should be greater than 11, i.e.
Water highly alkaline, to protect stainless steel from pitting and/or
Water acts as the principal solvent that breaks up soil stress corrosion.
particles after the surfactants reduce the surface tension
and allow the water to penetrate soil (water is commonly
referred to as “the universal solvent”). Acids
Acid detergents are also used specifically for descaling. The
Water also aids in the suspension and anti-redeposition of scale is made of metal salts of oxalates, phosphates,
soils. Once the soil has been dissolved and emulsified away carbonates, silicates, etc. The acid detergent should be
from the surface, any redeposition should be prevented. able to penetrate scale, for which a strong acid component
Water keeps the soil suspended away from the clean such as nitric acid is required. To facilitate the removal of
surface so that it can be carried away easily during the scale, an acid such as phosphoric acid is required that will
rinsing process. It is clear that without this water, the attach itself to metal ions and act as a sequestrant. Acid
cleaning formulae would be much less effective. detergents are often made of a blend of phosphoric acid
and nitric acid to a 1.2:1 ratio.
Base material (dissolving agent)
When a substance is dissolved, it becomes chemically Adding wetting agents in acid detergent improves
bound into the liquid and the liquid is usually clear. If the penetration and removal of scale especially when the scale
soil can be dissolved in the detergent liquid, not only can it is not only inorganic soil.
be removed from the plant surface, it can also be carried
away easily. Acids with a higher level of nitric acid than phosphoric acid
The same soil are recommended for passivation of stainless steel.
Particles of soil dissolved in a
Wetting agents (surfactants)
liquid
In breweries, water is always used as the medium for
carrying the detergents used to clean brewing plant.
However, water has a relatively high surface tension and
forms ‘beads’ on a surface rather than wetting it.

Most detergents contain substances that reduce the

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surface tension and so increase the detergent’s wetting by the oxidation of the soil. These are generally added to
power. Surfactants have a hydrophobic (water repellent) the caustic based detergent just before the point of use as
part and a hydrophilic (‘water loving’) part. Dependent on the oxiding agent breaks down so quickly, particularly at
the nature of the hydrophilic part the surfactants are high temperatures. Common usage areas include wort
classified as an-ionic, non-ionic, cat-ionic or amphoteric. copper heating surfaces and liquid hop extract addition
equipment.
'Bead' of water
sitting on a
surface.
The table below summarises the details of the most
common constituents and their contribution to the
effectiveness of the detergent:-

Water with a
'wetting' agent Constituent Effects Benefit/problem
added. Caustic soda Dissolves Does not rinse well.
organic matter.
Surface-active molecules act as wetting agents that assist Very hazardous and
with penetration of water into the dirt, otherwise water Sterilises cannot be used by
clings to itself due to the bipolar nature of the water especially when hand.
molecule. During cleaning of organic soil such as proteins, hot.
surface-active molecules are created out of hydrolysed Dissolves aluminium.
proteins, hence the creation of foam during cleaning.
Because of this tendency to foam, detergents are often Denatured by CO2.
supplemented with an antifoaming agent. Spraying a tank
containing CO2 with
Chelating (Sequestering) agents caustic can create a
Water is made "hard" by the presence of calcium, vacuum and collapse
magnesium, iron and manganese metal ions. These metal the tank.
ions interfere with the cleaning ability of detergents. The
metal ions act like dirt and "use up" the surfactants, making Other alkalis Dissolve Less aggressive than
them unavailable to act on the surface to be cleaned. e.g. silicates organic matter. caustic soda.

A chelating agent (pronounced keelating) combines itself Very good

with these disruptive metal ions in the water. The chelated dispersants.
metal ions remain tied up in solution in a harmless state
where they will not use up the surfactants. Oxidants e.g. Help dissolve Very corrosive unless
Hypochlorite protein. at high pH.
The choice of chelating agents or sequestrants depends on
the pH of the working solution. Their effectiveness is pH Sterilise.
dependant. Some common chelating agents used in
industrial cleaning compounds include phosphates, sodium Phosphates Soil removal. Very good rinsing
gluconate/heptonate or amino tris (methylenephosphonic properties.
acid) EDTA (ethylene diamine tetra acetate), sodium citrate,
sodium polyphosphates and zeolite compounds. Acids (nitric, Dissolve scale. Corrosive in high
phosphoric) concentrations.
Rinsing agents
It is important that at the completion of a cleaning cycle, no Not denatured by
detergent and accompanying soil remains on the plant CO2.
surface. In other words, the detergent must be ‘rinsable’.
Wetting Reduce surface May cause the
Thus to be effective, a detergent must be capable of
agents e.g. tension. detergent to foam.
adhering to the plant surface being cleaned; when the job is
teepol
done, however it must be rinsed away.
Sequestering Prevent the Expensive.
Rinsing agents are added to the detergent to enable these
agents e.g. formation of
two incompatible actions to take place.
EDTA scale.
Oxidising agents
These enhance soil breakdown and removal by the
mechanical action of the O2 gas release, or more normally

154 General Certificate in Brewing

Factors affecting the selection of detergents the drainage systems and environmental air? Because
detergents ultimately end up in the waste water, the
Legal aspects various components should be bio-degradable, and not
Is the material legally allowed to be used in this situation? have a significant adverse influence on the biological
degradation processes which take place in a wastewater
Nature of the soil treatment plant.
In the brewery, the soil will generally be a combination of
proteins, carbohydrates, and fats. In filtered beer Solubility
packaging, the soil will consist largely of light deposits of The detergent must be fully water soluble.
minerals and proteins.
Costs
Corrosivity The aim is to keep costs as low as possible. To achieve this,
The detergent used for cleaning the production plant the various products will have to be compared on a cost-
material must not corrode the brewing / packaging plant or effectiveness basis, and not on a price per kg basis,
the building materials. including of raw materials and disposal, and any additional
handling or storage requirements. The reason for doing
Composition / residues this is that the costs of labour and equipment account in
What is the composition of the material, both before use most situations for the bulk of the cleaning costs. An
and as a result of any breakdown during use or storage? important aspect in this context is whether the detergent
How will these affect the product? can be re-used or regenerated.

Hardness of the water Analysis methods

The degree of water hardness may make it necessary to add How easy is it to monitor and maintain strengths during the
a chelating (sequestering) agent to the water. cleaning process? Are any special chemicals or equipment
required for both in line and off line analysis?
Temperature
Is it possible to use hot detergent solution? This can often Caustic / alkaline detergents
improve and shorten the cleaning process. However, see • Caustic soda based products are easily controlled
later notes on use of hot detergent. on conductivity, but when they are contaminated
with carbonates, which contribute to conductivity,
Cleaning method the control using purely conductivity is not
How is the material to be used? E.g. contact time, accurate.
temperature, concentration. When manual cleaning is used, • Caustic soda based products react with carbon
the detergent should not be aggressive to the skin. With dioxide, producing sodium carbonate then sodium
mechanical or automatic cleaning, the quantity of foam bi-carbonate, reducing cleaning efficiency. When
that is produced may be a limiting factor. cleaning vessels this situation creates the potential
for implosion of the vessel.
Safety aspects • Caustic solutions provide bacteriological action at
O
How safe is it to handle? What precautions must be taken high pH, particularly when used hot e.g. at 65 C.
to protect personnel who are handling the material directly, • They will corrode aluminium rapidly, and copper
or working in the vicinity of the material in concentrated or and brass to a lesser extent.
usable form? Particularly when working with concentrated
detergents and hot detergents, it is necessary to take Acid detergents
measures to protect personnel. Plant may need to be • Acidic products are used to remove inorganic soils
specifically designed to cope with hot cleaning. such as mineral films (from hard water) and stones
(e.g. calcium oxalate) from brewing.
Product integrity • They are most effective at pH < 2.5.
The detergent should not affect the taste and flavour of • They are free rinsing and help to remove inorganic
wort and beer, and should not contain any odorous matter. soil.
In working solutions the detergents should not affect the • Anionic surfactants can be added to improve soil &
head retention and the colloidal stability of the beer. If, in scale penetration.
spite of the precautions taken, traces of a detergent should • They do not react with water hardness or carbon
enter the wort or the beer, the toxicity of the detergent is dioxide.
very important. All cleaning materials must be approved for • They are generally easily controlled using
use in the food industry, and must not exceed the conductivity instruments.
permitted concentrations. • They require formulation with “non oxidising
biocides” to deliver concurrent cleaning and
Environmental aspects
sanitising, and to maintain hygiene in the
What is the impact on the environment, including buildings,
recovered acid detergent tank.

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The table below gives details of the types of detergent used
to clean in the various situations encountered in breweries Process pipework. Caustic soda with
and packaging plants:- wetting/rinsing/sequestering
* Variable levels agents. Normally cleaned at
Plant to be cleaned. Detergents often used. of soil. elevated temperature - ca.
O
Brewhouse e.g. Caustic soda with wetting / * Complexity 65 C is typical.
coppers/kettles. rinsing agents. Used at high means it is
temperature. difficult to
* High level of organic clean.
soil.
Packaging plant. Caustic soda with
Fermenting vessels (CIP) Caustic soda with wetting/rinsing/sequestering
wetting/rinsing/sequestering * Low level of agents. May be used at high
* High level of organic agents. May be used at high soil. temperature if the plant is
soil. temperature if the plant is * Complexity suitable.
* Atmosphere of CO2. suitable. Effectiveness may means it is
* Requirement for be reduced because of effect difficult to Cold acid detergent also
sterility. of CO2. High usage. clean. used - either as normal clean
* Requirement or regular descaling clean.
Acid with wetting/rinsing for sterility.
agents, but this is less
effective than caustic unless Returnable Caustic soda with
high pressure jets are used. cask/kegs. wetting/rinsing/sequestering
agents. Will be used at high
Compromise of caustic pre- * Care with temperature.
wash followed by a rinse, materials of
then acid recirculation is construction. Must use non-caustic
increasingly being used * High levels of detergents with aluminium.
because of problems with organic soil.
CO2 atmospheres and * Need for good
energy requirements when rinsability.
cold or hot caustic alone
used.

Yeast handling plant. Caustic soda with Temperature

wetting/rinsing/sequestering
* Extremely high levels agents. May be used at high The temperature that a detergent operates at influences its
of organic soil. temperature if the plant is effectiveness. The action of caustic soda, for example is
* Complexity means it suitable. much more powerful at high temperatures than at low
is difficult to clean. temperatures. So called neutral detergents such as silicate
* Requirement for Caustic pre-wash followed based materials are often used hot, particularly for keg and
sterility. by a rinse, then acid cask cleaning. It is not common to use hot acid detergents.
recirculation is increasingly
being used. The graph (below) illustrates how caustic soda reaches
maximum effectiveness at 85°C.
Maturation/conditioning Acid with wetting / rinsing
120
vessels. agents. Substitute acid for
th
every 10 clean with caustic
* Medium level of soda solution.
100

organic soil.
* Inert gas atmosphere. 80

* Requirement for
sterility. 60

40
Bright beer tanks. Acid with wetting / rinsing
agents.
* Low level of soil. 20

* Inert gas atmosphere.

* Requirement for 0
15 C 35 C 55 C 75 C 95 C
sterility. 25C 45 C 65 C 85 C

156 General Certificate in Brewing

Where hot detergents are used, the equipment, whether
production or packaging, or reusable packages such as kegs, Types of sterilants (sanitisers) as defined by active agent
including any sealing joints / gaskets must be capable of
withstanding:- The main types of chemical sterilant are:-

• The additional corrosiveness during the hot cycle. • The ‘halogens’ like chlorine, bromine and iodine.
• The changes in expansion of enclosed gases when Chlorine is often used in the form of sodium
the temperature changes from cold pre-rinses to hypochlorite or chlorine dioxide. Iodine can be
hot detergent, and from hot detergent to cold post used in the form of an iodophor.
detergent rinses. • Formaldehyde.
• The physical expansion / contraction of the plant • Ammonia in the form of quaternary ammonia
itself. compounds.
• Hydrogen peroxide.
The changes due to use of hot detergent must not • Peracetic acid.
adversely affect operation staff or the product. • Ampholytic surfactants.
• Ozone.
The temperature used is a compromise between safety of
the plant, personnel and product, and the speed and Some of the above are not now considered acceptable for
effectiveness of the cleaning and sterilising processes. use, for a number of different reasons.

Note that hot caustic detergent in the presence of CO2 can Some sterilants (sanitisers) are considered by many to be
create insoluble calcium carbonate deposits on the suitable for non-rinse application. Peracetic acid is widely
equipment surfaces. considered to be one such material. Most sterilants require
rinsing off with sterile water before the equipment may be
Notes:- used.

Identify the detergents used in the following areas of your

brewery:- Sterilants for non-rinse application

Brewhouse. Fermenting vessels. Oxygen releasing sterilants

Maturation/conditioning tanks. Bright beer tanks. These are peroxyacetic (peracetic) acid (PAA) and hydrogen
Packaging machines. Container washing machines. peroxide based sterilants. They are made from the
blending of acetic acid and hydrogen peroxide in the
presence of a stabilising agent. When used, the breakdown
15.2 Sterilants (sanitisers) products are oxygen and water from hydrogen peroxide
and acetic acid and oxygen from peroxyacetic acid.
Introduction
These types of sanitisers break down in the presence of
• Disinfection or sanitisation may be defined as the metal ions. Apart from being used in vessel sanitation, they
destruction of micro-organisms, but not usually are also used in sanitiser baths and in environmental
bacterial spores. It does not necessarily kill all micro- sterilant formulation.
organisms, but reduces them to a level acceptable for a
defined purpose, i.e. a level which is harmful neither to Hydrogen peroxide
health nor to the quality of perishable goods (in this • Not very effective on own.
case beer, cider etc.) • Will not affect beer flavour at volumes / levels
normally remaining after effective scavenging.
• Sterilisation is defined as the elimination of all forms of • Safe to use but strong oxidising agent and could be
life including microbial spores. This is most effectively a fire hazard.
achieved in the brewing industry by using steam at a
minimum temperature of 122°C for a contact time of at Peroxyacetic acids
least 15 minutes. These conditions are common in the • Effective over wide temperature range, though
pharmaceutical manufacturing environment, but in contact time may be long at low temperatures.
breweries usually only in a microbiological laboratory • Broad spectrum of bactericidal activity.
autoclave for preparing growth media etc. and • Non corrosive to stainless steel.
sometimes in yeast culture plant. • Safe at working strength, but dangerous in more
concentrated form.
• Larger contaminating volumes / concentrations
There are several different types of sanitising / sterilising considered to affect beer / cider flavour, therefore
agent. However many are toxic, corrosive, or likely to taint many users prefer to rinse off.
the beer.

Learning Material 2016 157

 • Unstable unless combined with hydrogen Iodine releasing compounds
peroxide. Iodine releasing compounds, e.g. iodophors, used to be
• Considered by many not to affect beer flavour widely used as both CIP and soak bath sterilants. However
volumes / levels normally remaining after effective use for CIP is comparatively uncommon nowadays, but they
vessel scavenging. are more widely used for sterilant soak baths.
• However, many users require a final rinse due to Iodophors combine elemental iodine with surface-active
possible flavour effects when in contact with beer compounds. Acid is added to stabilise the product. Iodine:-
or cider.
• Is effective across a broad spectrum of micro-
Sterilants requiring rinsing off after use for plant organisms.
sterilization • Has an effective pH range greater than chlorine (2
to 8).
Chlorine dioxide • Is somewhat less irritating than chlorine.
Chlorine dioxide has gained popularity as an effective, safe • Is dangerous as a gas.
to use sterilant. It is effective against a wide spectrum of • Is corrosive, particularly at high temperatures
o
micro-organisms and in removing biofilms. It is tolerant of (don’t use above 50 C.).
small amounts of organic matter. • Has a long, stable shelf life.
• Loses effectiveness at low temperatures or in
Chlorine dioxide does not chlorinate, therefore there is presence of organic matter.
minimal risk of flavour taints the low (but still effective) • Leaves a very strong and lingering taint if it
concentrations used for sterilising final rinse waters (circa contaminates the beer.
0.2 ppm), but risks remain if used as a terminal sterilant • Must be rinsed off.
(circa 5ppm) and this high level must be rinsed off with
sterile water. Quaternary ammonium compounds
• Non corrosive, effective at low temperatures and
However, there is greater risk if the pre-addition chlorine temperature stable.
level is high. This often occurs when the liquor has not • Effective at low concentrations.
been de-chlorinated prior to ClO2 addition. The breakdown • Solutions prone to foam formation.
products of chlorine dioxide are chlorite and chloride.
• Adverse effect on beer foam stability.
• Must be rinsed off.
Chlorine dioxide is used for disinfection in many areas:-
o water disinfection.
Sterilants for sterilant (soak) baths
o post or final rinse sanitiser.
o biocide for cooling towers and tunnel pasteurisers.
Iodophors
Iodophors are used in sanitiser baths because their
Some brewers have concerns over safety of handling of the
presence can be easily be detected with brownish red
raw materials and the accuracy of chemical dosing.
colour. Iodophors can taint the product when not handled
properly and if not rinsed off thoroughly before use. Where
Chlorine releasing compounds
a fear of tainting exists, peroxide/peracetic acid based
Hypochlorites are widely used as a source of chlorine.
sterilants may be used instead.
These must be kept at low concentrations, typically 150 to
200 ppm chlorine, with high pH to reduce the evolution of
Chlorine releasing compounds
free chlorine. The free chlorine attacks the surface of the
Hypochlorites are widely used as a source of chlorine for
stainless steel, leading to corrosion which can eventually
soak-baths. These must be kept at low concentrations,
perforate or crack the steel. It is commonly used in caustic
typically 150 to 200 ppm chlorine. To ease safety issues
solutions for aggressive “one off” cleans. Chlorine:-
when handling the liquid, tablets of the material are now
available, allowing easy, accurate and relatively safe
• Is very effective, hard water tolerant and effective
addition of the sterilant to the soak bath water.
at low temperatures.
• Is cheap in most forms.
• Is dangerous as a gas and must be kept away from
acids to prevent gaseous chlorine formation.
• Is corrosive to plant.
• Is less effective in the presence of organic matter.
• Leaves a very strong and lingering taint if it
contaminates beer or cider.
• Must be rinsed off.

158 General Certificate in Brewing

Peroxyacetic acids • Ozone is active against bacteria, viruses, fungi and
Peroxyacetic acids may be used for soakbaths. They do spores.
however have to be changed regularly, even if the • Effectiveness of ozone is pH sensitive. It is
equipment being soaked is not changed for long periods. unstable at both high and low pH.
This is due to the rapid degradation of the PAA to acetic • The effectiveness at pH 6 – 8.5 is equivalent or
acid and oxygen, particularly in warm environments. It is better than peracetic acid.
not possible to determine if there is sufficient active • It is safe to use with stainless steel, but corrosive
ingredient in the solution simply by looking or smelling, or to soft metals, rubbers and some plastics.
using a test strip. • Low oxygen pickup. 350 ppb ozone resulted in
1.44 ppm increase in dissolved oxygen in rinse
Environmental sterilants water. But it is therefore not suitable for sterilizing
deaerated water.
Environmental sterilants are used for sanitising floors, walls, • It has a “half-life” of 10 minutes and so needs to be
external surfaces of tanks and pipes and cleaning of drains. made at point of use.
For these to work effectively on surfaces, they must be able
to cling to the surface to allow for extended contact time. Note that because of safety risks, it is not approved for use
When rinsed off the walls, they must be easily removed. in all countries.
Because the risk of contact with the product is low, there is
a wider choice of ingredients that can be used. Ultra violet light
Although not strictly a sterilant for production plant, Ultra
Quaternary ammonium compound (QAC) sterilants Violet (UV) light is widely used to sterilise clear water for
These work by surface action. The QAC formulations rinse waters and high gravity beer dilution water. Once the
contain non-ionic surfactants like ethoxylated fatty alcohols water has been treated, there is no residual biocidal
to boost foaming properties of the product. In order that activity, hence its non-use as a terminal sterilant during
micro-organisms do not develop a resistance to sanitisers, cleaning. It is ineffective on turbid water, so cannot be
different types should be used over specific periods of time. used for hygiene maintenance of detergents or pre-rinse
waters.
Gluteraldehydes
These are commercially available as acidic solutions and Criteria for choice of sterilant
they are activated before use by making them alkaline.
They have a wide spectrum activity against different micro- The choice of sterilant depends on a number of factors:-
organisms.
Is a sterilant required?
Biguanides and Chlorhexidines The microbiological condition of the plant may be suitable
These have widespread bactericidal properties. For the for its purpose after the standard clean, particularly those
product to foam, non-ionic surfactants are added. Anionic where hot caustic detergents are used. Note also that
compounds deactivate these sanitisers. They are also not many acid detergents are now formulated to contain a
compatible with phosphate, borate, chloride or carbonate sterilant, and a separate sterilant cycle is not normally then
ions because they form salts, which are insoluble so making required.
the active ingredients unavailable.
Legal aspects
Chlorine releasing compounds. e.g. sodium hypochlorite Is the material legally allowed to be used in this situation?
Possibly the most popular sanitiser for drains is sodium
hypochlorite solution that has been diluted to contain Corrosivity
about 5% available chlorine during use. This must be kept The sterilant used for sanitising the production plant
separate from stainless steel equipment (or drain gullys!), material must not corrode the brewing / packaging plant or
as the free chlorine corrodes the stainless. It must also be buildings.
kept away from acids to prevent gaseous chlorine
formation. Composition / residues
What is the composition of the material, both before use
Ozone and as a result of any breakdown during use or storage?
Although this compound has been successfully used as a Would a residual ‘taint’ affect the beer quality? If so, it will
sterilant during CIP, it is more commonly used for treating probably be considered necessary to rinse off.
wash-down and rinse water, and therefore has been
included as sterilant used for environmental cleaning. Cleaning method
Typical use is for packaging wash-down hoses and bottle How is the material to be used? E.g. contact time,
filler external (glass removal) rinse systems and can filler temperature, concentration. When manual cleaning is used,
external rinse systems. the sterilant should not be overly aggressive to the skin.
With mechanical or automatic cleaning, the quantity of
foam that is produced may be a limiting factor.

Learning Material 2016 159

Safety aspects 15.3 Heat sterilization
How safe is it to handle? What precautions must be taken
to protect personnel who are handling the material directly, There is a maximum permissible temperature for growth
or working in the vicinity of the material in concentrated or and survival of any organism, and exceeding this will result
usable form? Particularly when working with concentrated in death (macro-molecules lose their structure and cease to
sterilants, it is necessary to take measures to protect function). This is a result of the combination of time and
personnel. temperature.

Product integrity Heat is used at different temperatures and for different

The working strength sterilant residues should ideally not times to achieve different levels of hygiene.
affect the taste and flavour of wort and beer, and should
not contain any odorous matter. In working solutions the Lowest temperatures are those used during beer
sterilants should not affect the head retention and the O
pasteurisation, e.g. 65 C for 20 minutes in a smallpack
colloidal stability of the beer. If, in spite of the precautions O
tunnel pasteuriser, or 73 C for 15 seconds in a flash
taken, traces of a sterilant should enter the wort or the pasteuriser. However neither of these temperatures /
beer, the toxicity of the material is very important. All times are suitable for plant sanitisation. Pasteurisation is
cleaning materials must be approved for use in the food discussed in more detail in the General Certificate in
industry, and must not exceed the permitted Packaging.
concentrations.
The uses of steam & hot water as sterilants
Environmental aspects
What is the impact on the environment, including buildings, Hot water is widely used for sterilisation of mains, where
the drainage systems and environmental air? Because very high levels of hygiene, approaching absolute sterility is
sterilants or their residues ultimately end up in the waste required. Brewing equipment commonly sterilised using hot
water, the various components should be bio-degradable, water includes:-
and not have a significant adverse influence on the
biological degradation processes which take place in a • Wort mains and wort chillers.
wastewater treatment plant. • Yeast propagation mains.
• Pasteuriser mains and pasteurisers in recovered
Solubility beer areas.
The sterilant must be fully water soluble to allow easy • Filters – KG, PVPP, cross flow and trap filters.
rinsing. • Yeast propagation equipment (though other
methods are also widely used).
Costs
The aim is to keep costs as low as possible. To achieve this, It is important to note that all “corners” of the plant must
the various products will have to be compared on a cost- reach the required minimum temperature for the minimum
effectiveness basis, and not on a price per kg basis, time. Temperature probes are typically set at the system
including of raw materials and disposal, and any additional return, and will only initiate timers once a degree or two
handling or storage requirements. The reason for doing this above the minimum to ensure the complete plant is at the
is that the costs of labour and equipment account in most minimum temperature. It is essential that turbulent flow in
situations for the bulk of the cleaning costs. An important pipework is achieved during sterilisation to minimise risk of
aspect in this context is whether the sterilant can be largely cold spots. The water is normally recirculated through a
re-used or is used as a “single shot”. heat exchanger to reduce water wastage.
Analysis methods Brewing equipment commonly sterilised using steam
How easy is it to monitor and maintain strengths during the includes:-
cleaning process? Are any special chemicals or equipment
required for both in line and off line analysis?
• Gas supply mains.
• Gas particulate trap and sterilising filters.
• Product trap filters.
Effect of sterilant residues on beer quality
• Product mains, such as yeast propagation transfer
mains (less common).
Please refer to the paragraphs above, which summarise the
key properties of the various types of sterilant. • Propagation tanks (less common).

Notes. The steam needs to be food grade, filtered to ensure it is

Give details of the detergents and sterilants used in a free of particulate matter, and “wet”, i.e. supersaturated as
it is the heat given up during the condensation of steam
cleaning regime that you are familiar with.
into water that kills the micro-organisms. The moisture
Why have those particular materials been chosen? makes the high temperature much more effective at killing

160 General Certificate in Brewing

micro-organisms as it contacts the micro-organisms technical information on any cleaning materials they
resulting in rapid heat transfer. supply. This information (including the MSDS – Material
Safety Data Sheets) covers recommended usage
The effects of time and temperature concentrations and actions to be taken in case of accidents.

Heat is very effective as long as the plant is held at high Hazards of detergents and sterilants
temperature, for an adequate time
Cleaning of tanks and pipe lines require the use of
When sterilising with hot water, a typical specification is for aggressive chemicals which are strong acids and strong
the temperature at the system return to be greater than 85 bases designed to remove soils:-
O
C for not less than 20 minutes.
• Strong alkalis degrade organic materials like fat
To achieve total sterilisation using steam requires contact and protein.
O
at 120 C for at least 15 minutes (as in a laboratory • Strong acids degrade inorganic materials like scale
autoclave) However, for practical purposes for plant or for and stone.
bulk pack container sanitising, contact time with steam • Oxidising agents such as chlorine, oxygen, bromine
usually only requires 2 – 3 minutes to achieve the necessary react with proteins and fats in particular. Safety
level of hygiene. precautions, as required by Occupational Health
and Safety legislations (ISO 18000), have to be
Dry Heat considered when using these chemicals.
• The use of hot chemicals can exacerbate the
(Superheated steam) damage caused, in a similar manner to the way hot
O
Temp C Time cleans are more aggressive than cold cleans.
120 8 hours We are made of these organic and inorganic materials too,
140 2.5 hours and can therefore be damaged by both dilute and
concentrated chemicals or by heat from the diluted
160 1 hour chemicals, or hot water or steam used for heating or
170 40 minutes sterilisation.

180 20 minutes Components of these chemicals may have short or long-

term effect on the health of the employees. Some
components can affect the health of the consumer at parts
per million levels.
Moist Heat
(Saturated steam) Additionally, all these materials can damage the
O
environment, including buildings, the brewing plant itself
Temp C Time and effluent systems. The products used have to comply
100 20 hours with environmental legislation with respect to handling of
spillage.
110 2.5 hours
115 50 minutes Read all labels and ensure you understand what the
material is to be used for, under what conditions, and the
121 15 minutes hazards associate with that material. Ensure suitable
125 6.5 minutes precautions are taken in response to this information.

130 2.5 minutes Every material used must be accompanied by Material

Safety Data Sheet (MSDS).

15.4 Safety An MSDS should disclose the following:-

• Manufacturer’s details.
Detergents are designed to dissolve organic matter, and • Product identification.
sterilants are designed to kill microorganisms. • Composition information on ingredient.
Consequently, these are dangerous materials for people to • Hazards identification.
handle. • Safety first measures.
• Firefighting measures.
In the most countries, under the Control Of Substances • Accidental release measures.
Hazardous to Health (C.O.S.H.H.) legislation (or similar • Handling and storage.
outside the UK), manufacturers are required to issue • Exposure control and personal protection.

Learning Material 2016 161

 • Physical and chemical properties. • Make sure you know the location of the nearest
• Stability and reactivity. safety shower / eye wash station
• Toxicological information. • To protect eyes:-
• Ecological information. o Safety glasses.
o Goggles offer the best protection for the
The MSDS is meant to give enough data about the product eyes.
that assist the user to make an informed technical decision. o Face shield. A face shield protects the
A user will only know about this safety information if the whole face.
information provided is read and, if necessary, the supplier • To protecting the body:-
is questioned to clarify. o Apron.
o Gloves.
Good practices for chemical storage o Boots.
o Smock.
• Chemicals must be stored in a secure, cool, dry o Rain suit.
area, with adequate and appropriate ventilation. • Normally, sleeves and trouser legs should be worn
• Chemicals must be clearly labelled, and the on the outside of boots and gloves.
Material Safety Data Sheets (MSDS) and usage
information be readily available and understood. Procedures in case of chemical spillage or discharge
• Chemical storage areas must be fitted with safety
showers and eye wash stations. When tackling any spillage or environmental incident the
• Chemicals must be separated by type, and if liquid, first priority is to:-
stored in bunded areas to prevent accidents to
• Ensure the safety of yourself and others
personnel, property, plant or the environment.
• Wear appropriate Personal Protective Equipment
• Overstocking must be minimised.
(PPE).
• Good stock rotation must be employed.
• Determine what the spillage is:-
• Ensure that when in the proximity of detergents
o Check for any labels or hazard warnings
and sterilants people use appropriate personal
look at MSDS or COSHH sheets.
protective equipment especially eye protection
o Is it foaming, fuming or burning?
(goggles), gloves, boots and overalls.
• Determine if the spillage is:-
• Acids – avoid splashes and contact with fumes. o Safe to tackle (minor spillages).
o Not safe to tackle on your own, i.e. you
• Caustic substances – mixing caustic with water need assistance (major spillages).
generates heat. Splashes can cause severe burns.
When diluting, add caustic to water, not the other Generally the inclination is to flush spillages to drain with
way round (automated systems greatly reduce the water.
risk).
• STOP – CONSULT – THINK – ACT.
The use of PPE (Personal Protective Equipment) • If you flush a chlorinated product into drain water
that is acidic it will release chlorine gas.
• PPE is a last resort as it does nothing to prevent • Concentrated detergents and sanitisers may kill
the original exposure to the substance. effluent treatment plants.
• PPE must be suitable for the task and the user. • Consult the MSDS (there is a section on spillages) –
• Training in the use of PPE is required. If you are think and then act.
not trained, then the task must not be carried out.
• Regular cleaning and maintenance of PPE is MINOR SPILLAGES
required – and always after use.
• Replace PPE when it is no longer fit for purpose, or Tackle only if you feel it is safe to do so:-
if it doesn’t fit properly. • Determine what it is.
• Wear appropriate protective clothing.
• Wear safety glasses with side protection at • Protect drains.
locations where chemicals, steam or hot water can • Contain or stop the leak.
be released (for example at chemical dosing • Clean up spill.
points) • Dispose of clean-up materials in appropriate
• Wear face mask protective clothing and safety disposal skips / drums etc.
boots when handling chemicals • The spillage may need reporting to appropriate
• Wear whatever PPE is required by local laws if the authorities.
requirements exceed the above recommendations

162 General Certificate in Brewing

 • A major priority is protecting the drains.
• Eliminate (i.e. remove the source of the spillage).
• Isolate the spillage (e.g. shut off leaking valves).
• Contain (e.g. drain mats / bunding materials).
• Clean up the spill to prevent further contamination.
• If available, use the absorbent material from the
appropriate spill kit (larger sites may have separate
kits specifically for oils or chemicals). Highly Flammable Flammable
Flammable (F)

MAJOR SPILLAGES

Spillages you feel are unsafe to tackle:-

• Get away & keep a safe distance.
• Determine what the spillage material is and obtain
MSDS if possible.
• Seal off area. Extremely
• Alert others. Flammable (F+)
• Look for injured people but only if possible and safe
to do so.
• Get help.
• With suitable help contain & clean up, or contact
Emergency Services to assist.

Notes.
Harmful (Xn) Health Danger Health Hazard
What type of detergents and sterilants are used in your plant?
and Irritant
What safety precautions during both storage and use are
employed in this plant?

Chemical Hazard Identification -

The following symbols for chemical hazard identification are

commonly seen in different regions:- Irritant (Xi) Irritant

Corrosive (C) Corrosive Corrosive Toxic (T) Poison Toxic

Oxidising (O) Self-Ignition Oxidising Very Toxic (T+)

Learning Material 2016 163

 Explosive (E) Explosive Explosive Dangerous for the Environmentally
Environment (N) Damaging

164 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 165

Section 16 Plant cleaning – Cleaning In Place systems

Introduction

Cleaning in place of brewing and packaging plant has largely Recovery system Single use system
replaced traditional methods where plant was dismantled Running costs are lower Higher running costs because
for manual cleaning, or personnel had to enter vessels and because • chemicals are always
manually clean them. Effective CIP systems, when used in • chemicals are recovered run to drain
conjunction with correctly designed beer production or • final rinse water is • these chemicals may
packaging equipment can deliver higher hygiene standards normally reused for pre- also affect effluent costs
than can be achieved with manual cleaning, with less risk of rinsing • water is run to drain
damage to the equipment or risk to personnel from manual • where hot detergent is after a single use
handling, cleaning chemicals or dangerous gases. used, this is recovered, • heating energy when
saving heating energy hot cleaning is usually
In many countries, increasing costs have necessitated wasted
reductions in manpower and the time required for manual
Good practice CIP sets are One cleaning unit can clean
cleaning operations. For improved economics, the use of
only able to clean one type different types of plant, for
larger batch sizes requires larger vessels and mains, which of plant from a cleaning unit, example rough beer and
are not able to be easily cleaned manually, if at all. e.g. unfiltered beer in FVs & bright beer tanks, though
MVs or BBTs this functionality is not
CIP is the circulation of detergents, water rinses and generally considered to be
sterilants through fixed plant without dismantling. In order acceptable.
to achieve this, tanks have to be fitted with spray
balls/heads and pipework has to be linked into a ‘ring’ The time required to clean is The cleaning time is usually
main. reduced because the longer because
detergents and sterilants can • the detergents and
be prepared prior to use – no sterilants have to be
16.1 Types of CIP system separate makeup time is made up to strength
required fresh each time
Comparison of single use & recovery systems • if hot cleaning,
additional time is
A Single Use (total loss) system doses concentrated required to heat up the
detergent or sterilant into the delivery line and although recirculating CIP fluids
they are recirculated during that specific cycle, e.g.
detergent recirculation, at the end of the cycle, the cleaning Effluent produced is Volume and strengths of
generally less because most chemicals generally higher
fluids are run to waste. In their simplest form, these
of the detergent, and than recovery systems.
systems do not even recover post detergent and post sometimes sterilant is
sterilant rinses, but use fresh water for all rinses. recovered at the end of the
recirculation cycle.
A recovery CIP system consists of tanks where supplies of
detergent and sometimes sterilant are held at the required Automation control is Simpler due to single
concentration for use. Cleaning fluids are delivered from generally more complex due recirculation “buffer” tank,
the tanks and returned to them both during and at the end to additional tanks and and detergent / sterilant
of the cycle. Detergent (and sterilant) strength and separate sequences for makeup integral to the plant
temperature is maintained in the tank. make-up, and the actual cleaning cycles.
plant cleaning cycles
A recovery system can be designed with more than one CIP
supply and return, to be run simultaneously, using common
detergent and recovered rinse tanks for example, so
reducing capital costs. Types of cleaning head used and reasons for their choice

The benefits and problems associated with ‘Recovery’ and There are two main types of spray head, the fixed spray
‘Total Loss’ systems are identified in the following table:- head and the rotating spray head.

Recovery system Single use system Fixed spray ball

Capital costs are higher Lower capital cost because Fixed sprayballs are drilled to a number of different designs
because separate (often only a single recirculation appropriate for the vessel they are being used to clean.
large) tanks are required for buffer tank, which is used for
detergent, recovered rinse all stages of the clean is
water and sometimes required
sterilant

166 General Certificate in Brewing

The spray pattern of a nominal 360 degree ball is shown The fluid runs down the side of the walls of the vessel in a
below. These may be used on small vessels. continuous curtain to create turbulent flow, contributing to
the effect of the chemicals, time and temperature to assure
a clean surface.

Vertical tanks typically have only one installed, but

horizontal tanks usually require two or more to give
adequate coverage.

The spray pattern of a nominal 180 degree ball is shown

below. These are widely used on vertical cylindrical tanks.

The choice of spray balls or rotating spray cleaners is a key

factor in the effective design and operation of a CIP system
for tank cleaning.

Rotating spray heads

The rotating spray head, for example, the Sani Magnum

show below, rotates at high speed, spraying the vessel wall
with a sheet of CIP fluid rather than a jet.

They use large volumes of cleaning liquid at low pressure.

Effective cleaning relies on the cleaning liquid flowing over
the surface of the tank at sufficient depth and speed to
clean effectively. Therefore the whole surface must be
wetted thoroughly by correct positioning of a suitably
designed sprayhead.

Burst delivery is often used because the delivery flow rate is

so high that often the scavenge system cannot prevent a
pond developing in the bottom of the tank. This is
particularly a problem with dish bottom vessels or
horizontal vessels. If a pond develops, the flooded portion
of the tank is not cleaned because the cleaning liquid does
not flow over the surface at sufficient speed to develop The turbodisc head rotates at high speed and sprays a fan
turbulent flow. of fluid on to the vessel wall. This type of head tends to be
used for small vessels only, or for cask washing.
Spray balls are relatively cheap and they are easy to
maintain although they can block up, especially if the
cleaning liquid is unfiltered.

The dimension of the vessel dictates the number of, size of

the ball(s) and the drill pattern required for total coverage
of the entire surface during the clean. The hole pattern in
the sprayball is designed to direct the bulk of the flow of
the fluid onto the area where most of the soil is located,
e.g. at the yeast ring in a fermentation vessel. The areas
not wetted by direct contact are wetted by the drainage of
the fluid from these areas

Learning Material 2016 167

The high pressure jet, for example the TZ74 shown below Rotating spray heads are relatively expensive and are made
rotates at slow speed, with a number of jets impacting the up of moving parts, therefore there is wear and tear during
walls, floor and top of the vessel. use. Rotating spray heads are often fitted with rotation
sensors linked to the alarm handling of the CIP automation
because a stationary head will only clean a very small
section of the tank. Filters in the CIP delivery are essential
to reduce the risk of blockage and wear of the rotation
turbine.

Although high pressure heads are expensive compared to

sprayballs, the reduced water usage arising will often pay
back this cost within a few months, and so are becoming
increasing popular. When using caustic detergent in
atmospheres containing CO2, the detergent is subject to
slower degradation by the CO2.

Vertical tanks typically have only one installed, but

horizontal tanks often require two, to give adequate
TZ74 cleaning pattern, partial cycle only shown:- coverage. They are considered to be far more effective in
horizontal tanks than sprayballs, and are frequently
installed as replacements.

Notes:
Write down the type of cleaning heads fitted to a tank
installation that you are familiar with.
Why was that type of cleaning head selected?

High pressure cleaning heads, e.g. Toftejorg TZ74. These

are mechanically driven heads that rotate to direct high- Operating principles of CIP systems
pressure jets to the tank surface, in a pattern to ensure that
the entire surface is jetted. This principle means that it RECOVERY (REUSE) SYSTEM
takes a defined time to complete the pattern and cover all
surfaces. 1. First rinse:-
Recovery CIP System
Rotating jet cleaners require a high pressure supply to
direct the fluid onto the surface of the vessel to create. The
rotating jets have a higher impact force on the surface,
giving much higher physical cleaning effect on the soil or
scale than the flooding low pressure system applied on Fresh
Dilute
detergent
Dilute
sterilant
Recovered
rinse water
Production
plant
water tank
fixed spray balls. The mechanical force is a powerful aid to tank tank tank

the cleaning process and the system can use colder and or
less aggressive detergent, and often shorter cycle times
than sprayballs. The fluid flowing down the rest of the
surface continues to clean in a similar manner to that of
fluid from a sprayball. Fresh, or more normally, rinse water recovered from the
post detergent and post sterilant rinse cycles is delivered to
The jets on a rotating mechanism direct the fluid on the plant and returned to drain. If the buffer tank is too
forming a narrow track, and rotate a specified number of small, the rinse may be supplemented with fresh water.
times for a complete cycle, at the end of which the entire When cleaning tanks with spray balls, burst rinsing is often
surface will have had direct impingement from the high used to allow the tank to drain between bursts, so
pressure jet. improving the cleaning affect at the bottom of the tank.

168 General Certificate in Brewing

The time taken for these rinses will depend on the design of The diagram assumes use of recovered / reused sterilant
the plant and therefore how easy it is to clean.
Many systems use sterilant once only in a single use
2. Detergent circulation:- system. Fresh water is recirculated through the system,
Recovery CIP System and dosed up with sterilant until the required strength is
achieved, and then the system is recirculated for a
programmed time.

The time of sterilisation will depend on the effectiveness of

Fresh
Dilute
detergent
Dilute
sterilant
Recovered
rinse water
Production
plant the sterilant under those conditions, and the level of
water tank
tank tank tank
microbiological contamination in the plant, but times of 10
to 30 minutes are common.

5. Final rinse:-
The dilute detergent tank is maintained at the correct Recovery CIP System
strength and its contents are circulated through the plant.
At the start of the detergent cycle, the plant will contain
pre-rinse water, and the return will be run to drain until
detergent is detected to reduce dilution of the detergent.
Dilute Dilute Recovered Production
Fresh
detergent sterilant rinse water plant
The time of recirculation will depend on the level of soil in water tank
tank tank tank

the plant, but times of 20 to 30 minutes are common.

3. Second (post detergent) rinse:-

Fresh water is delivered to the plant and normally If it is considered, however, that residual traces of the
recovered to a recovered rinse water tank. As the plant sterilant will not harm the product, the final rinse may be
contains detergent, at the start of this cycle, the return is omitted.
recovered to the detergent tank until the rinse water is
detected. The water from the post detergent rinse is This is similar to the initial rinse although the water that is
usually collected and used as the pre- rinse when the next used must be of potable quality, i.e. free from
piece of plant is cleaned. microbiological or chemical contamination.

Recovery CIP System The water from the final rinse is usually collected and used
as an initial rinse when the next piece of plant is cleaned.

TOTAL LOSS (SINGLE USE) SYSTEM

Dilute Dilute Recovered Production
Fresh
detergent sterilant rinse water plant
water tank
tank tank tank
It has been assumed for these drawings that there is no
recovered rinse water tank built into the system.

1. First rinse:-
Single Use CIP System
4. Sterilisation:-
Recovery CIP System

Production
Fresh Recirculation
Dilute Dilute Recovered Production
plant
Fresh water tank buffer tank
detergent sterilant rinse water plant
water tank
tank tank tank

Concentrated detergent

If the sterilant is suitable for re-use, the dilute sterilant tank Concentrated sterilant
is maintained at the correct strength and its contents are
circulated through the plant for a programmed time. At the Fresh water is delivered to the plant and returned to drain.
start of the cycle, because the plant contains rinse water, When cleaning tanks with spray balls, burst rinsing is often
the return is run to drain until the interface is detected to used to allow the tank to drain between bursts, so
reduce dilution the sterilant in the tank. improving the cleaning effect at the bottom of the tank.

Learning Material 2016 169

The time taken for these rinses will depend on the design of programmed time. Normally no further additions of
the plant and therefore how easy it is to clean. sterilant will be made.

2. Detergent clean:- Single Use CIP System

Single Use CIP System

Production
Fresh Recirculation
plant
water tank buffer tank
Production
Fresh Recirculation
plant
water tank buffer tank

Concentrated detergent
Concentrated detergent
Concentrated sterilant
Concentrated sterilant
The time of sterilisation will depend on the effectiveness of
Fresh water is delivered to the plant and dosed with the sterilant under those conditions, and the level of
detergent, ideally at a rate that achieves the required microbiological contamination in the plant, but times of 10
concentration in a single pass. If the detergent is to be to 30 minutes are common.
used hot, then the recirculating fluid will be heated at the
same time as the detergent is being dosed. When all the
recirculating fluid is at the correct concentration and 5. Final rinse:-
temperature, the detergent is circulated back to and from
the buffer tank for a programmed time. Normally no Single Use CIP System
further additions of detergent will be made, but if
necessary, but it will continue to be heated if necessary.

The time of recirculation will depend on the level of soil in

the plant, but times of 20 to 30 minutes are common.
Production
Fresh Recirculation
3. Second rinse:- water tank buffer tank
plant

Single Use CIP System

Concentrated detergent

Production Concentrated sterilant

Fresh Recirculation
plant
water tank buffer tank
If it is considered, however, that residual traces of the
sterilant will not harm the product, the final rinse may be
omitted.

The water that is used must be of potable quality, i.e. free

Concentrated detergent from microbiological or chemical contamination.

Concentrated sterilant

Fresh water is delivered to the plant and returned to drain. 16.2 CIP cleaning cycles
The buffer tank is drained and rinsed out as part of this
cycle. Typical cleaning programmes and cycle times

CIP programmes vary from one area of the brewery to

4. Sterilisation:-
another, depending on the soil loading and the
Fresh water is delivered to the plant and dosed with
microbiological standards required. Example CIP
sterilant, ideally at a rate that achieves the required
programmes are given below for a number of different
concentration in use in a single pass. When all the
areas.
recirculating fluid is at the correct concentration, the
sterilant is circulated back to and from the buffer tank for a

170 General Certificate in Brewing

Brewhouse: • In the FVs, the cycle will vary depending on the spray
• Hot (or sometimes cold) pre-rinse (ideally head used, the soil loading and whether sacrificial
recovered final rinse water). caustic rinses are used. If sacrificial caustic rinses are
• Detergent (normally hot caustic) recirculation used, pre-rinses are best not carried out as they
• Hot water post detergent rinse. reduce the effectiveness of the caustic rinses.
• In MVs and yeast vessels, the yeast / hop debris ring
Fermenting, maturation vessels and yeast vessels: is virtually absent, and the vessels are often free
The following is one of the more traditional CIP cycle rinsing. If this is the case, the rinse cycle may be
sequences:- reduced to a few minutes only.
• Pre-rinse with hot or cold water (ideally recovered • Bright beer tanks may be rinsed for 5 to 10 minutes.
from post detergent or post sterilant rinse). • Mains are typically rinsed for perhaps ½ a circuit
• Hot caustic detergent recirculation. volume only, except in the brewhouse, where the
• Post detergent fresh water rinse. soil residues may be very high. All product transfers
• Sterilant recirculation. should have been flushed out with clean water, and
• Post sterilant fresh water rinse. the soil loading should be very low. There is no need
to waste additional water flushing out where no
An increasing number of breweries are using the following residues remain.
sequence
• There is no pre-rinse. Detergent recirculation times vary somewhat, according to
• Sacrificial cold caustic detergent burst rinsing. the soil loading and the cleaning head used.
• Post caustic detergent fresh water rinse (to drain). • In the brewhouse, 20 to 30 minutes is typically used.
• Cold acid detergent recirculation. • In FVs, MVs and yeast vessels using hot caustic
• Post detergent fresh water rinse. recirculation, typical times are 20 to 30 minutes.
• Sterilant recirculation. • In FVs, MVs and yeast vessels using a sacrificial
• Post sterilant fresh water rinse. caustic prewash cycle, this can take up to 30
minutes, mainly because of the soak time after each
Note that the separate sterilant recirculation and post burst delivery cycle. A rinse of perhaps 5 minutes
sterilant rinse may be omitted because many if not most follows. The acid detergent cycle which then follows
acid detergents are now combined detergent & sanitisers. lasts for 15 to 20 minutes.
• Mains detergent recirculation is typically 20 to 30
Bright beer tanks and similar vessels: minutes, but this varies according to the complexity
• Pre-rinse with cold recovered water. of the circuit.
• Cold acid detergent recirculation.
• Post detergent fresh water rinse. Post detergent rinse (and post sterilant rinse) cycles are as
• Sterilant recirculation. short as possible to minimise water usage. The cycle time
• Post sterilant fresh water rinse. commences once the interface between detergent and
Again, the separate sterilant recirculation and post sterilant water has been detected at the CIP set, and the rinse times
rinse may be omitted because many if not most acid can be very short after this if a clean interface, i.e. efficient
detergents are now combined detergent & sanitiser. rinsing is achieved. For vessels, only one or two minutes
after the interface is detected is normal. For mains, it can
Also note that good practice requires regular periodic be as short as ¼ of a circuit.
caustic cleaning of the BBTs etc.
Sterilant recirculation cycles are dependent upon the type
Mains: of sanitiser being used, but typical times are between 10
• Pre-rinse with hot or cold water (ideally recovered and 20 minutes. A long duration should not be required as
from post detergent or post sterilant rinse) the detergent cycles will have removed or killed the vast
• Hot caustic detergent recirculation majority of micro-organisms.
• Post detergent fresh water rinse
The function of each of the cycle stages
Depending on the quality of the hot detergent cycle, in
particular the temperature, there may be a need for a The pre-rinse removes as much water soluble and loose soil
sterilant recirculation and final rinse cycle in addition to the as possible and flushes this to drain.
above.
The detergent recirculation cleans the plant by loosening
The pre-rinse cycle times are very dependent upon the soil and suspending solid materials, which may include yeasts,
bacteria, protein from malt and hops, oils and resins from
loading.
hops, and dissolving soluble materials. This leaves the
• For instance, in the brewhouse, the pre-rinse cycle
surface free of material that might cover yeast or bacteria.
may last for 10 – 15 minutes or more, because the
Most detergents are also effective at killing yeasts and
soil loading is so high, and because rotary high
bacteria.
pressure cleaning heads are often used.

Learning Material 2016 171

Where a sacrificial caustic cycle is used when cleaning FVs, These specifications may be cross checked against the real
MVs and yeast vessels, this is to remove the high levels of time values, and if out of range may alarm hold the clean so
organic material present in the form of yeasts, hop debris corrective action can be taken.
etc. Acid detergents are not as good as this and are far
more expensive. It is cheaper and more effective to The frequency of cleaning may be determined by advanced
sacrifice a small quantity of caustic than a similar quantity management information systems, with automatic start of
of acid detergent. clean when a plant item becomes dirty.

The post detergent rinse removes traces of detergent and Similarly, automated plant, before it can be used for a
any loosened soil residues. production process can be set so it has to be clean / sterile
before the production process will be allowed to start.
The sanitisation cycle destroys any remaining micro-
organisms left on the surface of the physically clean plant. Management information systems will allow regular
reviews of cleaning frequency and reviews of problems,
The post sterilant rinse removes traces of sterilant if it is particularly if repeated. This allows corrective action to be
decided that no sterilant should remain in the plant and be taken as required.
capable of contaminating the product.
What this automation and management information does
Notes: not do is provide assurance that the programme specified is
Write down details of a CIP programme for a piece of plant fit for purpose. Other methods are required for this aspect,
that you are familiar with. For all rinse, detergent and as outlined below.
sterilisation cycles include
Visual inspection
• times,
Wherever possible, both production and CIP plant should
• temperatures
be visually inspected at least annually. This is probably best
• chemical strengths
carried out when other essential planned maintenance /
• flow rates.
insurance inspections are carried out. Where pipes are
What precautions are taken to ensure that the plant is not
broken for maintenance or as part of the routine set up for
re-contaminated before re-use?
production / CIP, the internal surfaces should be inspected.
Whenever possible, open up the production tanks and
inspect the spray balls for scale blockage: this can be done
Quality assurance of cleaning operations
remotely by using sound waves.
Quality assurance of CIP is provided by a number of
If visible soiling is present, it must be assumed that
methods
microbial contamination is also present, hidden in the
• CIP and production plant process automation and soiling. Special cleans may be required to bring the plant
management information systems. back to the required state, but in addition, the root cause of
• Visual inspection. the problem must be resolved, either by appropriate
• Swabbing Techniques. maintenance, or by changes to the CIP programme.
o Conventional Techniques.
Laboratory sampling / analysis
o Rapid Methods.
Methods carried out by the lab include conventional and
• Rinse Water Analysis. rapid result analysis of microbiological swabs of production
equipment wherever this is possible, either as routine
CIP and production plant process automation
validation, or as “one offs”. In most cases, it is considered
Providing the systems are programmed correctly, the
essential to re-clean or re-sterilise following swabbing,
repeatability of automated CIP processes and the interface
especially if the plant has had to be opened up by breaking
with the production plant provides a high degree of
joints or opening access doorways.
assurance that the plant is being cleaned as specified. The
process specifications for a number of key parameters Where equipment forms a closed circuit and is impossible
including those below may be specified:- to carry out regular swabs, final rinse water samples may be
• Times. taken and analysed.
• Temperatures – delivery & return.
• Flow rates. In all cases, the beer which has been processed by the
production plant should be checked for increased levels of
• Delivery pressures.
contamination. Any major increase suggests the plant itself
• Detergent strengths. is contaminated.
• Sterilant strengths.
• Numbers of pulse pause delivery cycles. 16.3 Hygienic plant design
• Product tank empty checks.
• Rotation checks on high pressure cleaning heads. Introduction
Effective cleaning is the result of a combination of four
factors:-

172 General Certificate in Brewing

 • Time. How long is the cleaning agent/detergent in • There should be no ‘U’ bends or ‘goalposts’ in the
contact with the plant? More heavily fouled plant pipework. Where these are necessary, then cleaning
normally requires longer to clean than less heavily processes must ensure they are cleaned effectively
fouled plant. (principally by using high flow rates).
• Pipes must be designed for fast flow of fluids during
• Temperature. How hot is the cleaning cleaning.
agent/detergent? Cleaning effectiveness rises as the • Spray heads must be of suitable design and sited in
temperature increases up to an optimum for each the correct position.
chemical. • The plant must be accessible for external cleaning
and maintenance.
• Chemical activity. How strong/effective is the
cleaning agent/detergent? Generally, the stronger
(a) Vessel design
the detergent, the greater the cleaning power. Note
that at very high concentrations, cleaning
Vessels in modern breweries are designed for being cleaned
effectiveness will drop off, and there may be
in place, i.e. by using spray heads rather than manually with
problems rinsing, or high wastage which makes high
personnel having to enter and clean. They must drain well
concentrations non cost effective. There may also
and have no internal encumbrances.
be safety issues with higher concentrations.

• Physical activity. How vigorously is the cleaning Cylindroconical vessel

agent/detergent applied to the plant? The greater
the physical force, the more effective the cleaning. • Drain freely and completely.
Thus high pressure cleaning heads are increasingly • Smooth walls.
used for tanks. • No or minimal intrusions (e.g. temperature probes) .
• Sprayball or high pressure head.
If one of these factors is reduced, for example if the plant
has to be cleaned quickly, then another factor must be
increased to compensate, for example hot instead of cold
detergent could be used.

Plant design needs to take this concept into consideration

in the following ways:-

• The plant capacity needs to be large enough to allow

time for cleaning.
• The parts of the plant where very high standards of
hygiene and sterility are normally required to be
capable of being cleaned hot.
• The materials of construction should be capable of Open square FV
withstanding strong detergents such as caustic soda
or phosphoric / nitric acids. • Poor drainage due to flat floor.
• The plant needs to be able to withstand oxidising • Attemperation coils difficult to clean, either
agents such as peracetic acids which are used as manually or using CIP techniques.
sterilants. This is particularly applicable to valve • Normally manually cleaned.
rubbers and joint gaskets.
• The plant design should either allow access for
manual cleaning or more commonly, ensure that
detergent can flow over the surface at the speed
required to give turbulent flow, and thus clean
effectively.

Design features to minimize soil accumulation

(b) Vessel drainage
Effective cleaning is a major consideration when designing
brewing equipment. The main areas for consideration are:- Good drainage:
Fast flow of liquid cleans surface, and scours away soil from
• No encumbrances (intrusions) in vessels if possible. side walls and dish bottom Often requires burst delivery to
• Vessels must drain well. achieve effective scouring of the vessel bottom dish surface
• There must be no ‘dead legs’ in the pipework. on a regular basis throughout the clean.

Learning Material 2016 173

Vortex breakers are often fitted to improve the flow rate at
the outlet, and so reduce the scavenging time.

Pipes with sharply angled bends are difficult to clean,

leaving soil build up in the areas shown.

The bottom section of the cylindroconical vessel shown

below is the most easily drained.

They are only very rarely fitted with vortex breakers, and
providing the CIP return pump is fast enough, only rarely
need burst delivery to ensure the lower cone vessel walls
Slow flow of cleaning fluid through a pipe (typically less
are scoured effectively at all times.
than 1.5 metres / sec, see diagram) is ineffective because
the flow is not turbulent, or laminar, and there is no
scrubbing action. The times required for rinsing will also be
excessive, leading to high water usage and long cleaning
times.

Adequately fast flow of cleaning fluid through a pipe

(typically more than 1.5 - 2.0 metres / sec, see lower
diagram) causes turbulent flow, and generates a good
scrubbing action.

Poor drainage
Very low (non-turbulent) flow in the ponded area doesn’t
clean the surface of the dish bottom.

Soil removed from higher up the vessel may be re-

deposited on the dish area.
Long dead legs (> 1.5 times the pipework diameter) never
get cleaned, even with good turbulent flow through the
main section of pipework, and irrespective of the direction
in which they point. .

(c) Pipework design

Pipes and mains in modern breweries are designed to be

cleaned in place. They have smooth bends and no ‘dead Short dead legs are cleanable providing there is good
legs’. Flow of cleaning fluids is fast through all the turbulent flow through the main sections of pipework.
pipework, 2 meters per second giving turbulent flow and
effective cleaning.

Pipe with smooth, swept bends are cleanable.

174 General Certificate in Brewing

Because Tee pieces are inevitable, particularly with
equipment that is manually set up, it is essential that the
direction of flow is correct to maximise the ability to clean.
Plug valves are virtually impossible to clean as part of a CIP
circuit. The housing surrounding the plug allows soil and
microorganism build up. They can only be cleaned properly
by dismantling. Typically they are manually controlled, but
may be controlled automatically.

Double seat valves are widely used in critical areas. These

designs are effectively two separate hygienic blocking
valves combined, with interseat drainage for leak detection.
To clean the interseat space and seals, they are fitted with
interseat cleaning, or are designed to lift a single seat a
time, leaving the other seat sealed. This design minimises
the risk of cross contamination between different products
or CIP fluid and product. Two styles of 4 port valve are
shown here:-

A pipe circuit for CIP should consist of pipes of the same

diameter. If there are different pipework sizes, the flow
rate must be suitable for the largest pipe diameter,
otherwise the flow may be too slow to clean.

(d) Valve design

Valves in modern breweries are designed so that they can

be cleaned in place as part of the pipework cleaning cycle.

A butterfly valve is easy to clean. It has a smooth finish,

hygienic glands to seal around the spindle, and when the
seal is in good condition has minimal areas where soil and
bacteria can build up. They can be manually controlled or
automated.

Learning Material 2016 175

 Peristaltic pumps, e.g. for yeast cropping, are reasonably
easy to keep clean. The internal hose is flexed by the
compression wheel or shoe and helps top loosen any soil.
However, a bypass is essential to allow the remainder of
the pipework to be cleaned at the correct flow rate.

(e) Pump design

A centrifugal pump, e.g. for beer transfer, are easy to clean.

The impeller creates turbulence. There are only two seals
with no “hard to clean” corners. Sometimes pumps, particularly positive displacement
pumps such as lobe and piston pumps are fitted with
pressure relief by-pass systems. This by-pass must be
opened during the cleaning programme whilst the pump
runs to maximise cleaning effectiveness.

Design features of CIP sets and brewing plant to facilitate

CIP

The key features to be considered when designing a CIP

Stainless steel lobe pumps, e.g. for yeast cropping, are system include:-
reasonably easy to keep clean. The internal surfaces are
polished. However, a bypass is essential to allow the Product tank
remainder of the pipework to be cleaned at the correct • Size and design, e.g. cylindroconical, dish end
flow rate. vertical, dish end horizontal.
• Tank material, e.g. stainless steel, epoxy resin,
copper, aluminium.

Pipework
• Diameter and length of cleaning circuit.
• Pipework material. Typically in new or recent
developments this will be stainless steel, but
old plant may still contain copper and brass.

Piston pumps, e.g. for accurate dosing of additives, are Fouling

difficult to clean. A film of soil on the cylinder wall and the • The type of fouling.
non-return valves is difficult to remove due to the low flow • The degree of fouling.
rates through the pump. A bypass is essential to allow the
remainder of the pipework to be cleaned at the correct For instance, brewhouse plant will get fouled more easily,
flow rate. and heavily than bright beer tanks and mains.

176 General Certificate in Brewing

The factors noted above will determine:- • Strong construction, for example thick walls to a
• The flow rates and pressures to tank cleaning vessel.
heads, and from the tank outlets. • The presence of a pressure relief valve, which must
• The flow rate to clean the pipework. be regularly tested.
• The choice of cleaning/sterilising chemicals (see • Vacuum relief system, to prevent the collapse of
Section 15). the vessel due to the very low pressures that will
• The detergent recirculation temperature occur if the vessel cools quickly.
• The CIP programme or sequence of cleaning cycles
to ensure the plant is cleaned. Mains are normally cleaned hot. The layout must be
designed to allow expansion and contraction of longer runs
The following factors also need to be considered:- without damage to fixed items of plant such as valve blocks
• The number of individual routes (plant items) in or supporting brackets.
the same are that require cleaning
• The cleaning frequency of each route (plant item) Construction materials
• The likely duration of each of these cleans The choice of material that the plant is made from needs to
allow for the detergents and sterilants that are going to be
These factors will then help determine if the CIP system is used.
to be a ‘recovery’ or a ‘total loss’ system, the number of
independent channels installed, the tank sizes and the type Most modern plant is constructed of a suitable quality of
of and level of automation and monitoring. This will then stainless steel. However, pump glands, hoses, valves and
determine the capital and revenue (running) costs. sensing equipment such as thermometers, must also be
compatible with what might be very corrosive substances.
Whichever type of system is installed, it should be capable Some of the more common problems are listed below:-
of being cleaned periodically to remove any debris removed • Caustic soda will dissolve aluminium.
from the production plant and subsequently deposited in • Chlorine is a very strong oxidising agent and will
the tanks. Note that in the following diagrams, no facility to corrode most metals.
clean the CIP tanks themselves is shown. • Acids will seriously damage concrete.
• Dilute sulphuric acid corrodes many grades of
Hot cleaning stainless steel.
Some plant is designed to be cleaned at high temperatures • Hoses and rubber seals, for example plate heat
because of the importance of hygiene and sterility. The exchanger gaskets can pick up taints from
yeast culture vessels are common examples. Plant design sterilising agents, e.g. chlorine and iodine.
features that allow high temperature cleaning of tanks are:-
• If gaskets become worn, it is possible for small
detergent volume to be trapped between rubber
and plate, thereby setting up a corrosion cell.

Example of a single use (total loss) CIP set

Learning Material 2016 177

Example of a recovery CIP set using caustic detergent only

Features included in the two more detailed layouts for CIP • Individual cleaning programmes can be designed
sets include:- and fine tuned when the plant is commissioned to
maximise cleaning effectiveness, and minimise
• Level switches or gauges on the individual CIP set revenue costs. This programme will be
tanks, to ensure the tanks do not run out of CIP consistently adhered to subsequently.
fluids during a clean, or overflow causing • Cleans can run unsupervised.
dangerous spillages. • Automated records of cycle times, detergent
• Temperature sensors immediately after the heat strengths, temperatures and flow rates can be
exchanger, to ensure the delivery temperature is implemented.
correct. • The clean can be suspended if a problem is
• Temperature sensor on the return line, to ensure detected.
the minimum temperature has been achieved • Detergent and sterilant strengths can be
throughout the plant being cleaned. optimised.
• Conductivity sensors on the recirculation loop to • Sensors can detect detergent / sterilant strengths
ensure the detergent or sterilant strength is on the return line and direct the return to tank or
correct at all times. drain reducing chemical and water costs.
• Pressure sensors and indicators to ensure that the • The CIP set automation can be linked to the
required pressure is achieved where this is a process plant automation to ensure the plant is
specific requirement, e.g. for high pressure available for cleaning at the start of a clean, and
cleaning heads, or to indicate blockages of, or available for production at the end of a clean.
damage to filters and heat exchangers. • Flow rates and supply pressures can be adjusted
• Flow meters to ensure the flow rates are correct automatically (using variable speed pumps) to suit
for the item of plant being cleaned. the type of plant being cleaned.
• A filter in the delivery line to ensure that large • Interlocks can be built in to assure plant, product
particles which might block spray heads, or and personnel safety.
damage other equipment are removed.
• A heat exchanger to ensure the temperature of the
CIP fluid is correct at all times (only required if
warm or hot cleans required). Notes:
Draw an automated CIP system that you are familiar with
Automation and monitoring
and specify the pieces of equipment that are automatically
Complex CIP systems are ideally controlled using
controlled.
automation, the advantages being:-
178 General Certificate in Brewing
Design features for the working environment • Walkways and hand rails should be made of
corrosive resistant material or coated with a
Room and building finishes suitable corrosion resistant material.
The buildings that house brewing and packaging plant • No protrusions should be allowed on walls and
should be designed with the following hygienic design windows should have sills facing the outside. Any
features:- internal protrusion or beams should have at least a
30° fall to reduce dust from accumulating and to
• The floors can be cleaned easily. This means good
facilitate cleaning.
drainage and chemical and temperature resistant
impermeable floors, tiled or of suitable material • All holes to the exterior should be covered by
that is durable and has an impermeable surface plastic bird and or fly netting.
that will allow for regular cleaning and sanitation.
• All process areas should be protected against entry
• Floors of the process and packaging areas must be of insects, vermin, dirt and dust. All floors and
made from materials that resist the chemicals at walls should be repaired promptly should they be
the concentrations found in the operational areas. damaged.
• Where areas are earmarked for storage of the • Hot and cold water points should be positioned
concentrated forms of detergents and other strategically around the plant for hand cleaning
materials, the floors and walls should be able to and cleaning of equipment, walls and floors.
resist those materials.
• Toilets and changing areas must be positioned
• Floors must have a good fall towards the drains to away from the process area and be fitted with
prevent ponding of water after spillages or hosing suitable lockers, showers, washbasins and other
down. 1.5% is often considered the minimum fall. required sanitary fittings.
• Drainage systems should be dimensioned (size and
falls) to allow for effective discharge of effluent
16.4 General plant cleaning
with solids without having any blockages.

• All drains in the process areas and packaging areas 16.4.1 Cleaning plant surfaces, walls & floors
should have appropriate airlocks.
General requirements
• Drain covers in the packaging areas should be
• Suitable bins to hold all waste material should be
constructed with baskets to retain glass or other
positioned around the plant.
debris.
• Only nylon (i.e. not natural bristle) brooms and
• Skirting of the wall to floor joints must be brushes should be used to sweep and clean floors
adequate, generally considered to be at least etc.
100mm high and of the same material as the floor • Foam cleaning systems are increasingly being used
finish. as these allow quick, and more importantly effective
and regular cleaning of intricate areas, with reduced
• The walls must be easy to clean. Walls in the manual handling hazards for personnel.
process areas should be tiled to the ceiling or • Squeegees can be used to push excess water from
coated with a durable and washable coating. the floors.
Ceilings should be painted with durable and • Sufficient hoses and hose points are required to
washable coating. Where possible, anti-mould allow cleaning of walls, floors and equipment.
coatings should be used. • Special brushes may be required for cleaning
surfaces of the plant. Care must be taken not to
• The plant can be accessed for maintenance, ideally scratch inside and outside surfaces of stainless steel
without the need for scaffolding. plant.
• Personnel performing cleaning duties should wear
• There is adequate lighting with access for
appropriate personal protective equipment.
maintenance.
• Suitable detergents should be used for general
• There is good ventilation or air-conditioning should cleaning of all surfaces. The choice of the detergents
supply sufficient air movement to reduce the risk must take account of the fact that chlorine based
of a damp atmosphere, which can result in mould chemicals are corrosive to stainless steel equipment.
growth and to eliminate odours. • MSDS certificates must be available for all materials
on site.

Learning Material 2016 179

Constituents of foam cleaning agents Foam cleaning has proven to be a very effective, efficient
and popular method for cleaning of rooms and equipment.
A typical foam cleaner contains a blend of caustic alkali, The improvement in foam technology, such as long cling
sequestrants and high foaming surfactants/wetting agents. foams, and the introduction of different types of foam
Some foam detergents also contain hypochlorite for use in detergents have made it a process that can be used, with
particularly heavily soiled areas. benefit, in many situations. Air pressure must be sufficiently
high to generate a dry, and hence adhesive, foam.
• When selecting the type of foam cleaning material
to be used, consideration should be given not only Foam is created by mixing water, detergent and air
to the soil to be removed but also the materials of together and applying it via a hose with a special nozzle or
construction that the foam detergent will come lance onto the surfaces and equipment. The foam
into contact with. detergent will typically be applied at 3 to 5% v/v, depending
• Alkaline based foams are the most common used on the soil to be removed and water hardness. The main
for cleaning in the food industry. They will range advantages of foam and gel cleaning in comparison to
from approximately pH8 to pH12 (in use) and are manual cleaning are:
effective on most types of soil encountered. Some
alkaline foams are inhibited and may be safe to • The detergent solution can be applied to large and
use on soft metal such as aluminium, tin, brass etc. difficult to reach areas in a short period of time.
Uninhibited alkaline foams may cause some • The can be an extended detergent contact time
corrosion to soft metals. between the soil and the detergent.
• Chlorinated foams are alkaline based with a • There is normally a reduction in the time required
chlorine “donor”. They are usually very powerful to clean equipment, particularly complex
detergents. The introduction of hypochlorite in equipment such as pie racks and valve blocks.
the formulation is to assist with protein removal
• Less manpower is therefore required.
rather than acting as a biocide.
• Detergent use can be carefully controlled.
• Acid based foams are used for the removal of
• Application of hazardous detergents can be made
mineral scale and protein build up. They may be
safer, allowing use of stronger detergents for
used in hard water areas (usually more than
effective cleaning.
200ppm). They will range from pH1 to pH4, are
aggressive and care should be taken on soft metals
A common misconception of foam and gel cleaning is that it
such as aluminium, tin, brass, copper and zinc.
removes the need for any type of physical action (such as
• QAC (Quaternary Ammonium Compound) foams
scrubbing with a brush or scourer). Physical energy must
are used mainly for light to medium cleaning tasks
still be applied after suitable detergent contact time. The
such as break cleaning and product changeovers.
physical energy can be applied by either scrubbing or by
• Neutral foam detergents are by description energy from a water jet, usually at high or medium
approximately pH7. They are usually used where pressure.
soft metals are present or to reduce the hazards of
cleaning and therefore reduce the need for All wash-down systems whether low, medium or high
Personal Protective Equipment. pressure will cause overspray and / or aerosols, which can
The use of foaming systems lead to cross contamination if no controls are put in place.

Foam cleaning refers to the cleaning process where the

main detergent is applied as foam, and Gel cleaning where Notes:
the main detergent is applied as a gel. Gels can also be Draw a diagram of a piece of plant with which you are
aerated during application; this is called a mousse. Foam or familiar:
gel application is followed by a water rinse. This rinse this • Identify parts that are easy to clean.
can be of low, medium or high pressure. • Identify parts that are difficult to clean.

180 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 181

Section 17 Engineering and Engineering Maintenance

17.1 Engineering Basics Applications - closed impeller

• Most common type of impeller.
PUMPS • Handles liquid with low levels of solids.
• Wort, beer, water transfer.
• Flash pasteurisation.
• Filter precoating powders.
• CIP delivery and scavenge.

Applications - open impeller

• Where liquids contain higher levels of solids.
• Wort transfer from lauter tun.
• Trub transfer.
• Thin yeast slurry transfer (though not best pump for
this duty) .

Advantages
Centrifugal pumps • Comparatively inexpensive.
They are excellent pumps for general transfer applications • Smaller than other designs with similar capacity
of low viscosity liquids such as wort, beer, water. • Easy to clean.
Centrifugal pumps handle high volumes with a smooth, • Easy to install due to compact size and the ability to
non-pulsating flow. rotate the discharge port to various positions for
ease of piping.
• Less expensive to maintain. They are easily
disassembled for quick service, and have few moving
parts.
• Wear due to operation is minimal.
• Will handle fine solids (but will wear pump material
if solids are hard & abrasive such as KG powder).
• Valves in discharge line may be closed with minimal
risk of damage to pump in short term.
• No pressure relief by-pass valve required in
discharge main.
Liquid enters the central inlet port of pump. The level of
liquid must be high enough above pump, or the supply Disadvantages
pressurised to push the liquid into the pump. The rotating • Damages fragile products such as mash, so most are
impeller moves the liquid to the outside of the impeller, unsuitable for this purpose.
into the casing and towards the discharge port. The
• Can't easily handle solids or thick products such as
pressure is dependent on the design of the impeller and the
yeast slurries.
casing. The flow rate is dependent upon restrictions in the
• Easily gas locked.
inlet and outlet piping and the height that the liquid needs
• Not normally self-priming.
to be moved.
Hygienic properties
Straight bladed impellers are very inefficient. The capacity
• Minimal risk of blockage due to open design.
of the pump can be controlled by either trimming the
diameter of the impeller or restricting the discharge of the • All surfaces are accessible and can be polished to
pump with a partially closed valve but these can cause any surface quality.
unnecessary damage to the product. Curved impellers are • All internally wetted areas are actively flushed by
much more efficient and substantially reduce turbulence product flow.
and damage to the product. • No enclosed or low flow areas within the pump or
impeller.
Reasonably priced variable frequency drive (VFD), also • Self- cleaning.
known as variable speed drive (VSD) speed controls are
widely available. With a VFD you can use a larger diameter Positive displacement pumps
impeller so that the pump is capable of pumping at a range All positive displacement pumps take a fixed portion of
of different flow rates, whilst operating at its best product (the amount that fits between the rotors or vanes
efficiency. The required flow rate can be achieved without or in the housing) and physically moves that product from
excess turbulence, wasted energy or damage to the pump. the inlet to the outlet side of the pump. The pump impellers

182 General Certificate in Brewing

move slowly (typically 300 - 500 rpm for rotary) and there is • As described above, the second type of diaphragm
very little slippage, especially if pumping a thick product like pump works with volumetric positive displacement,
mash. but differs in that the prime mover of the diaphragm
is neither oil nor air; but is electro-mechanical,
Advantages: working through a crank or geared motor drive. This
• Can pump thick products such as mash, yeast, trub. method flexes the diaphragm through simple
• Gentler on the product, especially thick products. mechanical action, and one side of the diaphragm is
• Can produce high pressure. open to air.

Disadvantages: Operation of a double diaphragm pump

• Many designs produce pulsing flow. The double diaphragm pump is perhaps the most
• Hard to clean. commonly used type of diaphragm pump in breweries, and
• Lower flow rates, bigger and more expensive than so only this type is described.
equivalent capacity centrifugal pump.
• Can be more expensive to maintain. Compressed air flows into the right air chamber, causing
• Can build high pressure if blocked, so normally have the right diaphragm to flex. This expansion creates a high
pressure relief system fitted at outlet ]. pressure in the right fluid housing equal to the air pressure
applied to the pump. The inlet check valve (4) of the right
Piston pumps fluid housing closes, the outlet valve (2) opens, and the fluid
A motor-driven cam pulls the piston back and forth in the is pumped through the outlet manifold. The pump shaft
pump head. A flexible seal around the periphery of the moves right creating a vacuum in the left fluid housing. The
piston prevents leakage of liquid from the back of the left inlet check valve (3) opens, the left outlet valve (1)
pump. Check valves mounted in the head open and close in closes, and the fluid flows into the left fluid housing.
response to small changes in pressure to maintain a one-
way flow of the liquid.

The capacity of the pump is determined by the plunger

diameter, the stroke length and the number of strokes per
unit of time. The combined adjustment of stroke length
and speed allows metering as a function of the two
variables. A piston pump is independent of head against
which it is pumping.

At the end of the pump stroke the air valve switches and
compressed air will flow into the left air chamber, causing
Applications the left diaphragm to flex. The inlet check valve (3) of the
• Filtration – bodyfeed dosing. left fluid housing closes, the outlet valve (1) opens, and the
• Additives dosing, e.g. colour, priming sugar, finings. fluid is pumped through the outlet manifold. The pump
• CIP – concentrated detergents and sterilants. shaft moves left creating a vacuum in the right fluid
housing. The right outlet valve (2) closes, the right inlet
Diaphragm pumps check valve (4) opens, and the fluid flows into the right fluid
A diaphragm pump is a positive displacement pump that housing.
uses a combination of the reciprocating action of a rubber,
Teflon or similar diaphragm and suitable non-return check
valves to pump a fluid. This type of pump is sometimes also
called a membrane pump.

There are two main types of diaphragm pumps used in

breweries:-
• In the first type, the diaphragm is sealed with one
side in the fluid to be pumped, and the other in air
or hydraulic fluid. The diaphragm is flexed, causing
the volume of the pump chamber to increase and
decrease. A pair of non-return check valves prevents
the reverse flow of the fluid.

Learning Material 2016 183

Applications Applications
• Yeast slurry transfers from tank to tank. • Filtration – bodyfeed dosing.
• Trub slurry transfer. • Additives dosing, e.g. colour, priming sugar, finings.
• Yeast and bottoms transfer to presses for beer • CIP – concentrated detergents and sterilants dosing.
recovery. • Laboratory equipment.
• Yeast cropping and transfer.
Advantages of diaphragm pumps • Trub slurry transfer.
• They do not depend on pumped liquid for • Yeast and bottoms delivery to presses for beer
lubrication, thus can be run dry without damage. recovery.
• They are self-priming. • Re-slurried filter cake transfer to waste.
• They can have single or multiple chambers, with
more chambers resulting in smoother flow. Advantages
• They can pump fluids with fine solids, though the • Seal-less design. The main feature of the peristaltic
solids may affect the seals (ball valves in the pump is the tube/hose. Because this is the only part
diagrams). of the pump to come in contact with the product it
• They are pressure balanced. They stall if discharge is means the pump avoids corrosion and is leak-free.
closed and restart when discharge is opened so • Dry running. Many pump users face difficulties when
avoiding heat build-up and component wear. the pump runs dry. Note that in many designs the
• They have minimum product agitation. outside of the tube & the rotor are immersed in
• If air driven, they are safe in hazardous areas, no lubricating oil.
sparking. • Self-priming. The pumps are capable of self-priming
and can handle products that are likely to suffer gas
Disadvantages
breakout.
• They generally have a low throughput.
• Gentle pumping action. Because of the tube/hose and
• If mechanically driven, they need a pressure relief the pumps’ gentle action, the product being pumped
valve on the outlet if there is a risk of dead-ending is not damaged in the process thus making peristaltic
(not applicable to air driven pumps as these will pumps ideal for shear sensitive or viscous liquids or
stall). suspensions such as yeast slurry.
• Pulsating flow (though they can be smoothed to • High discharge pressure. The pumps can provide high
some extent). discharge pressures meaning they are suitable for use
Peristaltic pumps where the product being pumped is viscous and
Peristaltic pumps work using the process of peristalsis to develops high back pressure (e.g. yeast slurry), or is
pump products through a hose, in the same way that food being pumped into an areas of high pressure (e.g.
is pumped through the small and large intestine. kieselguhr dosing).
• The hose sits around a rotor which, when turning, • Accurate dosing. The pumps are accurate in dosing,
compresses a segment of the hose almost flat. with repeatability of circa ±0.5% and metering
capabilities of circa ±2%.
• This compression is released as the rotor moves
around the hose with the hose reinforcements • Enhanced hose life & abrasion resistant. Tube/hose
causing it to spring back to its round shape, thus life is not related to a product’s abrasive qualities. The
creating a partial vacuum refilling the hose. tube/hose only fails due to fatigue or chemical action.
• This compression creates a seal and, as the rotor Progressive cavity pumps
turns, any product on the discharge side of the rotor These are a type of positive displacement pump. They may
is propelled forward and displaced from the pump. be known by a variety of similar names including Moineau
• Combining this suction and discharge action results (after the inventor), Mono pump, Moyno pump and Mohno
in a self-priming positive displacement pump. pump They are also known as progressing cavity pumps,
eccentric screw pumps or cavity pumps.

The progressing cavity pump uses the helical rotor pumping

principle. There is a single helix metal rotor which rotates
eccentrically within a double helix resilient stator. The rotor
of circular cross section creates a continuously forming
cavity as it rotates. The cavity progresses towards the
discharge end, carrying the pumped material with it. As the
stator open cross sectional area is always constant the flow
rate is continuous without pulsation.

The volumetric flow rate is proportional to the rotation

rate.

184 General Certificate in Brewing

The pumps are suitable for fluid metering and pumping of • As the lobes come out of mesh, they create
viscous or shear-sensitive materials. The cavities taper expanding volume on the inlet side of the pump.
down toward their ends and overlap with their neighbours, Liquid flows into the cavity and is trapped by the
so that, in general, no flow pulsing is caused other than that lobes as they rotate.
caused by compression of the fluid. • Liquid travels around the interior of the casing in the
pockets between the lobes and the casing -- it does
not pass between the lobes.
• Finally, the meshing of the lobes forces liquid
through the outlet port under pressure.

Lobe pumps can handle solids such as yeast slurry without

damaging the product. Particle sizes pumped can be much
larger in lobe pumps than in other PD types. Since the
lobes do not make contact, and clearances are not as close
as in other PD pumps, this design handles low viscosity
liquids with reduced performance. Slip in a rotary lobe
pump is the amount of liquid which escapes from the high
pressure side of the pump to the low pressure side. Slip
occurs between the two lobes, between the lobes and the
rotor case walls and between the lobes and the front and
Applications back of the rotor case.
• Yeast slurry transfer (more commonly waste yeast).
Applications
• Trub slurry transfer.
• Yeast cropping and transfer.
• Re-slurried filter cake transfer.
• Yeast and bottoms presses for beer recovery.
Advantages
Advantages
• Capacity is proportional to speed.
• Can handle fine solids such as yeast slurries.
• Self-priming even with entrained air.
• No metal-to-metal contact.
• Can handle a variety of viscous materials.
• Good CIP capabilities.
• Minimal damage to shear sensitive products.
• Long term dry run (providing there is lubrication to
• Can handle liquids containing solids or abrasive seals).
particles.
• Non-pulsating discharge.
• Pulsation free operation.
• The flow can be bi-directional, though is rarely if
• Positive displacement. ever used in brewing.
Disadvantages • Relatively quiet operation.
• Reduced pressure developed with thin liquids such Disadvantages
as beer.
• Reduced pressure developed with thin liquids such
• Needs pressure relief valve on outlet if there is a risk as beer.
of dead-ending.
• Needs pressure relief valve on outlet if there is a risk
Lobe pumps of dead-ending.
These pumps offer a variety of lobe options including single,
Gear pumps
bi-wing, tri-lobe (shown), and multi-lobe. Rotary lobe
The simplest gear-type pump, most commonly used in the
pumps are able to handle slurries, pastes, and a wide
brewing industry, uses a pair of mating gears rotating in an
variety of other liquids. If wetted, they offer self-priming
oval chamber to produce flow. As the gears rotate, the
performance. A gentle pumping action minimizes product
changing size of the chambers created by the meshing and
degradation. They also offer reversible flows and can
un-meshing of the teeth provides the pumping action.
operate dry for long periods of time. Flow is relatively
independent of changes in process pressure, so output is Another design (not shown) uses an external rotating ring
constant and continuous. with internal gear teeth that mesh with an internal gear as
it rotates. As the inner gear rotates, the tooth engagement
Lobe pumps are similar to external gear pumps in operation
creates chambers of diminishing size between the inlet and
in that fluid flows around the interior of the casing.
outlet positions to create flow.

Slip in a gear pump is the amount of liquid which escapes

from the high pressure side of the pump to the low
pressure side. Slip occurs between the two gears, between
the gears and the rotor case walls and between the gears
and the front and back of the rotor case.

Learning Material 2016 185

 flow, it is fully closed. The rim of the disc and the
circumference of the pipe at the point of contact are
generally fitted with sealing rings to provide complete
shutoff.

The maintenance costs are usually low because there are a

minimal number of moving parts and there are no pockets
to trap fluids.

They are especially well-suited for the handling of large

flows of liquids or gases at relatively low pressures and for
the handling of slurries or liquids with large amounts of
suspended solids.

They can be automatic or hand operated. Seat materials

can be specified to suit the particular duty. They are
relatively cheap and provide good “shut off”. They are not
suitable for controlling flow rates accurately, though are
often found “locked” partially closed for crude flow control.

Applications
• Yeast cropping and transfer.
• Yeast and bottoms presses for beer recovery.

Advantages
• The flow can be bi-directional, though is rarely if
ever used in brewing.
• Gear pumps are capable of self-priming because the
rotating gears evacuate gas in the suction line.
• Can be relatively high speed.
• High pressure.
• Relatively quiet operation.
• Design accommodates wide variety of materials.
• Good CIP capabilities.
• Non-pulsating discharge.
Non hygienic butterfly valve – to demonstate basic design
Disadvantages only.
• No solids allowed, though they can be used for yeast
slurries. Advantages
• Fixed end clearances so potential for considerable • Compact design requires considerably less space,
slippage. compared to other valves.
• Light in weight.
• Quick operation requires less time to open or close
VALVES
• Available in very large sizes.
Butterfly valves • Low-pressure drop and high-pressure recovery.
A hygienic butterfly valve suitable for use with beer, cider
Disadvantages
etc. has a short circular body, a round disc, metal-to-soft
seat seal, top and bottom shaft bearings, and a stuffing box. • Throttling service is limited to low differential
The construction of a butterfly valve body varies. A pressure
commonly used design is the wafer type that fits between • Cavitation and choked flow are two potential
two flanges. Another type, the lug wafer design, is held in concerns
place between two flanges by bolts that join the two • Disc movement is unguided and affected by flow
flanges and pass through holes in the valve's outer casing. turbulence
Butterfly valves are available with flanged, threaded or butt • Butterfly valves require special seal for tight shutoff.
welding ends.
Gate valves
A circular disc, of the same internal diameter as the pipe is Gate valves are primarily designed to start or stop flow, and
pivoted in the pipeline. When the axis is parallel to the when a straight-line flow of fluid and minimum flow
flow, it is fully open. When the axis is at right angles to the restriction are needed. In service, these valves generally are
either fully open or fully closed.

186 General Certificate in Brewing

The disk of a gate valve is fully drawn up into the valve
bonnet when the valve is fully open. This leaves an opening
for flow through the valve at the same inside diameter as
the pipe system in which the valve is installed.

A gate valve can be used for a wide range of liquids and

provides a tight seal when closed.

Advantages
• Good shut-off features.
• Gate valves are bidirectional and therefore they can
be used in two directions.
• Pressure loss through the valve is minimal.

Disadvantages
• They are not hygienic and so must not be used for
product.
• They cannot be quickly opened or closed.
• Gate valves are not suitable for accurate control of
flow rates.
• They are sensitive to vibration in the open state.

The disc or gate travels normal to the direction of flow of

the liquid and causes a rapid change in the area of the
orifice. Sizes up to 12” (30cm) are common.

Weir type valve

Applications
• Air and other gases
• Steam supply

Advantages
• A weir-type diaphragm valve can be used to control
small flows.
Diaphragm valves • Diaphragm valves are particularly suited for the
A resilient, flexible diaphragm is connected to a handling of corrosive fluids or other fluids that must
compression system by a stud moulded into the diaphragm. remain free from contamination.
The compressor is moved up and down by the valve stem. • The operating mechanism of a diaphragm valve is
Hence, the diaphragm lifts when the compressor is raised. not exposed to the media within the pipeline. Sticky
As the compressor is lowered, the diaphragm is pressed or viscous fluids cannot interfere with the operating
against the contoured bottom in the straight through valve mechanism.
or the body weir in the weir-type. A straight through type • Many fluids that would clog, corrode, or gum up the
of diaphragm valve is shown below. working parts of most other types of valves will pass
through a diaphragm valve without causing
problems. Conversely, lubricants used for the
operating mechanism cannot be allowed to
contaminate the fluid being handled.
• There are no packing glands to maintain and no
possibility of stem leakage in valves.
Disadvantages
• Generally these are unhygienic and must not be
used with product (beer / cider etc., where the
mains require cleaning)

Learning Material 2016 187

Needle valve Double seat valves
A needle valve has a relatively small orifice with a long, These are commonly used on larger installations where for
tapered seat, and a needle-shaped plunger, on the end of a instance, a number of tanks are connected to a number of
screw, which exactly fits this seat. As the screw is turned different filling, emptying and CIP lines and are used to
and the plunger retracted, flow between the seat and the ensure the complete separation of incompatible products in
plunger is possible. However, until the plunger is automatic process plants. The closed valve avoids mixing
completely retracted the fluid (or gas) flow is significantly the two liquids by having two independent valve seats with
impeded. Since it takes many turns of the fine-threaded depressurized leakage discharge between them. In case of a
screw to retract the plunger, precise regulation of the flow damaged sealing, the process medium escapes from the
rate is possible. valve into the depressurized area. The leakage space can be
cleaned by lifting the upper valve disk or lowering the lower
Needle valves are commonly used when a precise control of valve disk respectively, or less efficiently by spaying CIP
gas flow is required, at low pressure such as wort fluids into the space between the upper and lower seats.
oxygenation or small scale carbonation.
The following diagrams show the phases of opening of a
Since flow rates are low and many turns of the valve stem typical double seat valve.
are required to completely open or close, needle valves are
not used for simple shutoff applications. It may also be
necessary to force the needle into the orifice resulting in
damage to the needle or the orifice surface.

Typical separated flows – CIP & Beer

Applications
• Flow control of air, CO2 and other gases

Larger variable flow control valves operate on a similar

principle, but use wider “plugs” instead of a needle. The
principle of operation is shown below.

Bottom seat lifting – slight beer leakage

188 General Certificate in Brewing

 Advantages
• Quick quarter turn on-off operation
• Tight sealing with low torque
• Smaller in size than most other valves

Disadvantages
• Generally these are unhygienic and must not be
used with product
• Some suppliers claim to have hygienic ball valves,
but these still have a portion of the ball surface and
the housing which is does not come into contact
with CIP fluids and must therefore be considered
unhygienic
• Conventional ball valves have poor throttling
properties
• In slurry or other applications, the suspended
particles can settle and become trapped in body
cavities causing wear, leakage, or valve failure.

Bottom and top seats sealed – leakage stops Plug valves

Plug valves are valves with cylindrical or conically-tapered
"plugs" which can be rotated inside the valve body to
control flow through the valve, in a similar manner to ball
valves. The plugs in plug valves have one or more hollow
passageways going sideways through the plug, so that fluid
can flow through the plug when the valve is open. An
advantage of these types of valves is that they are excellent
for quick shutoff. The following diagram shows a three way
valve.

Seats fully lifted – flow from bottom to upper main

3 way plug valve
Ball valves
A ball valve is a quarter-turn rotational motion valve that Applications
uses a ball-shaped disk to stop or start flow. If the valve is • They are not hygienic as the surfaces cannot be fully
opened, the ball rotates to a point where the hole through exposed to CIP fluids, and therefore are not suitable
the ball is in line with the valve body inlet and outlet. If the for beer or cider production.
valve is closed, the ball is rotated so that the hole is
perpendicular to the flow openings of the valve body and Pressure Relief Valves
the flow is stopped. A pressure relief valve (PRV) is a safety device designed to
protect a pressurized vessel or system during an
Applications overpressure event, i.e. any condition which would cause
• Air, gaseous, and liquid applications pressure in a vessel or system to increase beyond the
• Drains and vents in liquid, gaseous, and other fluid specified design pressure or maximum allowable working
services pressure (MAWP). The primary purpose of a pressure relief
• Steam service valve is protection of life and property by venting fluid or
gas from an over-pressurized vessel. There is normally a
statutory requirement to test these valves regularly.

Learning Material 2016 189

Spring loaded PRV
The basic spring loaded PRV has been developed to meet
the need for a simple, reliable, system actuated device to
provide overpressure protection.

The image on the right shows the construction of a spring

loaded PRV.

The valve consists of a valve inlet or nozzle mounted on the

pressurized system, a disc held against the nozzle to
prevent flow under normal system operating conditions, a
spring to hold the disc closed, and a body/bonnet to
contain the operating elements. The spring load is Applications
adjustable to vary the pressure at which the valve will open. • They are used for liquids and steam, though the
exact internal design will differ for each application.
When a pressure relief valve begins to lift, the spring force
increases. Thus system pressure must increase if lift is to Pressure regulating (control or reducing) valve
continue. For this reason PRVs are allowed an overpressure These are installed on services such as gas supplies to
allowance to reach full lift. This allowable overpressure is control the downstream pressure in the system at point of
generally 10% for non-actuated valves. This margin is use. They are usually installed in conjunction with a
relatively small and some means must be provided to assist pressure relief valve so the system is protected in event of a
in the lift effort. failure. The following is a simplified example of a steam
control valve.

Applications
• They are used for gases and liquids, though the exact
internal design will differ for each application. When the pressure is too high, the valve closes slightly and
when the pressure is at the desired level, the valve takes up
a pre-set central position.
Globe Valves
A globe valve is a type of valve used for regulating flow in a Applications
pipeline, consisting of a movable disk-type element and a • They are used for liquids and gases, though the exact
stationary ring seat in a generally spherical body. The valve internal design will differ for each application.
can have a stem or a cage, similar to ball valves, that moves
the plug into and out of the globe. The fluid's flow Anti-vacuum valve
characteristics can be controlled by the design of the plug These are designed to minimise the risk of implosion of
being used in the valve. A seal is used to stop leakage tanks being exposed to vacuum (e.g. during emptying, cool
through the valve. Globe valves are designed to be easily rinsing after hot-cleaning or caustic cleaning in a CO2
maintained. They usually have a top that can be easily atmosphere). These valves can be installed on any closed
removed, exposing the plug and seal. Globe valves are good tank. The size and setting of the anti vacuum valve is based
for on, off, and accurate throttling purposes but especially on thetank design data, cleaning procedure and process
for situations when noise and cavitation are factors. requirements. The following picture is of a dead weight
anti vacuum valve. (Photo courtesy of Alfa Laval)

190 General Certificate in Brewing

 JOINTS

The installation should fulfil the following requirements to

be considered hygienically designed:

• No metal on metal joints unless welded

• The minimum number couplings
• No sharp corners
• No dead ends, pores, cracks
• No O-rings, unless these provide a smooth seal
• No thread ends
• No shadow areas
Cleaning • No possibility of stagnant liquid (self draining)
The underside of the anti-vacuum valve is cleaned when • No risk of air entrapment (no ‘goal posts’)
closed, by the tank cleaning head, but this will not include
the valve seal. To include the valve seal in the cleaning cycle It is strongly recommended that joints are avoided
a CIP device can be mounted on the valve. wherever possible. Bending of the pipe is highly preferable
over the use of prefabricated bends with couplings. If pipe
The CIP device uses the CIP pressure to open the valve bending is not possible, welding is the preferred method
slightly and cleaning liquid flushes the valve disc and drains provided that the welding is done correctly to ensure
back in to the tank. The CIP device is supplied with a smooth and continuous welds. Where detachable joints are
splashguard to catch reflecting sprays. Note: This facility necessary, they should be sealed by suitable elastomer
can only take place if the tank is fully depressurised. seals.
Mounting Over-compression of seals may affect the hygienic
The valve should be seated horizontally. An inclination of characteristics of equipment in two ways.
max. 10° is acceptable but the lever arm must then point in
to the centre of the tank top.
• Firstly, over-compression may lead to destruction of
Non-return valves the elastomer particularly if the over-compressed
Non-return valves in hygienic pipelines (beer, cider, dilution seal is heated (such as during pasteurization or
water etc.) should be avoided. The principle of operation of sterilization). The elastomer may become brittle and
a non-return valve of the type widely installed in breweries fail to provide the required seal, whilst parts of the
is shown in the following diagrams. elastomer may break off and contaminate the
product.

• Secondly, over-compression may lead to protrusion

of the elastomer into the equipment, thereby
hampering cleaning and draining. Under-
compression too is highly undesirable as it may lead
to crevices and fail to provide a reliable seal. Even
when it is not visibly leaking, the seal may permit the
ingress of microorganisms.

Not only the dimensions of the metal components, but also

those of the gasket must be correct, ensuring adequate
compression at the product side, allowing for differences in
thermal expansion under all operation conditions (cleaning,
pasteurization or sterilisation, and processing).

Improper alignment may also result in inadequate cleaning

and reduced drainability. Many designs of joint (e.g.
traditional flange connection) do not control compression
of the gasket and automatically result in misalignment.

Installations containing conventionally designed O-ring

seals invariably create crevices that are impossible to clean
in-place. Further, it is difficult to inactivate micro-organisms
present in conventional O-ring seals because when heating
equipment with O-ring seals, the O-ring expands trapping
and protecting micro-organisms between the O-ring and
Learning Material 2016 191
the steel surface against contact with the hot water, • Almost all other analogue instruments (flow meters,
chemical solution or steam used for sterilizing. On cooling temperature sensors, conductivity sensors use 4 - 20
down, the O-ring shrinks and surviving micro-organisms will mA signals. If a pump runs at 0 % this corresponds to
be freed to infect the product at the start of production. 4 mA and 100% corresponds to 20 mA. We start at 4
mA so it is easy to detect an open circuit (i.e. 0 mA).
O-rings can be acceptable from a hygienic point of view if • Thermocouple devices used to measure temperature
mounted in a way that ensures that the area of steel use a mV signal. The change in temperature changes
covered by the rubber at the product side does not change the resistive properties of the sensor, thus changing
with temperature. However repeated changes in the voltage (ohms law)
temperature may result in accelerated ageing, so that • All analogue instruments present a 4 - 20 mA or
periodic replacement of the elastomer seal is required. variable mV signal to a PLC input card. This is
converted to a integer value e.g. 0 - 32000 which is
Non welded metal-to-metal joints seal as a result of the used in the program.
deformation of the contacting metal surfaces. The result is
permanent damage to these surfaces which makes it more Digital
difficult to obtain a tight seal after every disconnection. • Used where a distinct change of state is being
Even when these joints are not visibly leaking, the ingress of determined. e.g. vessel empty or full level switches.
microorganisms is probable. Further, the seal obtained is • Digital Inputs are usually 0 - 24 volts DC where zero
very unlikely to be at the product side. More likely, the is off and 24 volts is on (can also be 0 - 110 V or 0 -
actual seal follows an irregular line between the inside and 240 V)
outside. The resulting annular crevice will trap product. • Digital Outputs normally switch 0 volts = off and 24
Therefore, metal-to-metal joints must not be used in a volts = on (can also be 0 - 240 V)
hygienic plant. • Note 0 - 5 volts may be off, 5 - 15 volts not reliable,
15 - 24 volts is on. So if you get interference (noise)
Seals should be resilient enough to guarantee an adequate between 0 - 5 volts the input is off because it needs
seal under all process conditions. The selection of seal type more than 15 volts to switch on.
must take into be design to accommodate processes carried
out at both the maximum temperature (e.g. during Instruments commonly used in a brewery
pasteurization or sterilization) and minimum temperature • Oxygen
(e.g. during the cooling to cold maturation / filtration • Carbon dioxide
temperatures). Generally EPDM or Viton seals will meet • Nitrogen
the requirements of the production processes. • Alcohol
• PG
• OG
• Level
• Colour
• Conductivity
• Turbidity
• Biomass / Viability
• pH
• Flow
• Pressure
• Temperature

Installation

Protection against the environment

INSTRUMENTS The instrument itself must be protected by suitable
enclosure against the conditions anticipated including dust,
Analogue water, steam.
• Used where a continuous range of values needs to
be monitored e.g. dissolved CO2 levels in beer, It should be positioned so that where it is not intended to
turbidity, tank levels (variable volume indicated) use the instrument to measure that condition, it is not
exposed to abnormal conditions such as strong electric
• Where a range of changeover setpoints may be fields, dust, water, water vapour, vibration, aggressive
used, e.g. buffer tank top pressure control :– chemicals such as caustic or peracetic acid.

High level value - start venting the tank, Set point - The field wiring associated with the instrument must be
stop pressurising or venting the tank, as appropriate, suitable for the environment in which it is laid, and should
Low value - start pressurising the tank, Low low be protected by careful routing and trunking or cable trays.
value – put the associated processes into alarm hold.
192 General Certificate in Brewing
Protection against workforce magflow meters, typical distances quoted are 5D prior to,
The instruments and associate wiring should be positioned and 2D after the meter of straight pipe of equal internal
to minimize accidental damage due to knocks, washing diameter to that of the meter. More recent meters may
down etc., but ensuring good access for maintenance. not require as much – check the individual instrument
installation details.
Robust
The instrument should be suitable for the environment it is The instrument itself should not restrict the flow, otherwise
to be used in. For example, a temperature probe in a CIP it may affect the overall process design, or the increased
return line should be designed to cope with the flow rates pressure and turbulence may damage the instrument.
and temperatures required, with strong fittings to ensure
physical stability in the line. Instrument reliability

Accessible for maintenance Install in a fail-safe condition

Technician’s own access. Although desirable to site The instruments should be installed in a fail-safe condition,
instruments at high levels, or at the back of a valve block, i.e. in the event of instrument failure; the plant the
easy access is required by the maintenance technicians. If instrument is controlling will revert to a safe condition.
they are working at a comfortable height in good lighting Examples include high level probes which if they fail
conditions, then maintenance will be quicker, easier, and normally indicate the vessel is full, thus preventing
with less risk of safety problems. overfilling, or if a temperature probe controlling a beer
chiller should fail, then the coolant supply is shut off fully in
Plant isolations. It should be possible to isolate the the belief that the product is already too cool.
instrument from the plant using local isolation manual
valves so that, for example, full drain down is not required. Cross checked
It is essential to be able to isolate the plant electrically and The instrument may be cross checked against another
or mechanically to prevent it running whilst maintenance is instrument for validity. An example is the use of cross
in progress. checked low and high level probes set to operate an alarm
condition if the indicated values are incompatible. Should
Easy to replace / maintain the low level probe fail whilst the high level probe is
The fittings used to insert the instrument should be covered, then an "incompatible levels" alarm may be
compatible with others used across site, and require only generated and the process held. Another is the use of a
standard tools to remove & replace. Ideally it should be tank level transmitter (and hence volume) with a low level
possible from a time and cost point of view, to repair the probe in the outlet to control the tank empty sequences.
instrument in the brewery workshop, rather than replace, The tank may only be deemed empty if the measured tank
or have to return to supplier / manufacturer. volume is less than a small, but consistently measurable
volume, and the level probe is uncovered.
Operating conditions
The instrument may be cross checked against an operator
Good practice operating conditions for in line sensors such input into a SCADA system for validity. An example is the
as flow meters, conductivity probes, pH meters are as use of a temperature probe on the filter discharge during
follows – sterilisation, which may be used to prompt the operator to
confirm once all physical checks have been made, and the
The pipe should be full whenever the sensor is required to sterilisation timer may be started.
measure. This is particularly important for instruments
such as flow meters and haze meters, where entrained gas The instrument may be cross checked against the stage of
will cause a false reading. It may be less critical for the process for validity. An example is the use of interface
instruments such as conductivity or pH probes. However, detection devices only being enabled during the beer push
some probes are not designed to cope with drying out, and out DAL pre-flush to BBT sequence when the interface is
suitable instruments must be installed if the main dries out anticipated. Should a change of state be detected during
as part of normal production procedures. the forward flow sequence, then an alarm condition may be
generated, or perhaps the instrument may not be
Ideally the pipe should be rising or at least horizontal, with monitored at all.
a rising loop after the instrument to help ensure a full pipe.
A falling pipe requires high flow rates to ensure the pipe is
fully gas free should it ever entrain gas. FLOW METERS

The flow through the pipe should be reasonably “laminar”, Rotameters

such that excessive turbulence in the flow does not affect This is a simple and economical means of flow control, with
the instruments reading, or even damage the instrument. local readout, for a wide variety of gases and liquids of low-
This is assisted by not positioning the instruments too close to-moderate viscosities.
to sharp bends (typically less than 1.5 D radius) Tee pieces,
or other sudden changes in pipe diameter. In the case of

Learning Material 2016 193

 Electromagnetic
An electromagnetic flowmeter operate on Faraday's law of
electromagnetic induction that states that a voltage will be
induced when a conductor moves through a magnetic field.
The liquid serves as the conductor and the magnetic field is
created by energized coils outside the flow tube. The
voltage produced is directly proportional to the flow rate.
Two electrodes mounted in the pipe wall detect the voltage
which is measured by a secondary element.

Electromagnetic flowmeters can measure difficult and

corrosive liquids and slurries, and can measure flow in both
directions with equal accuracy.

Electromagnetic flowmeters have relatively high power

consumption and can only be used for electrical conductive
fluids such as water, beer or cider. This type is perhaps the
most common flowmeter in use for drinks production.
Rotameter operating principle Coriolus
Direct mass measurement sets coriolis flowmeters apart
from other technologies. Mass measurement is not
sensitive to changes in pressure, temperature, viscosity and
density.

Coriolis mass flowmeters use the coriolis effect to measure

the amount of mass moving through the element. The fluid
to be measured runs through a U-shaped tube that is
caused to vibrate in an angular harmonic oscillation. Due to
the coriolis forces, the tubes will deform and an additional
vibration component will be added to the oscillation. This
additional component causes a phase shift on some places
of the tubes which can be measured with sensors.

The Coriolis flow meters are in general very accurate, better

than +/-0.1% with an turndown rate more than 100:1. The
Coriolis meter can also be used to measure the fluids
Rotameter with built in manual flow control density.
A rotameter is a variable-area flowmeter inside of which a They are commonly used for measuring wort and beer
float rises and falls in a tapered tube to provide a measure density, both in-line and off-line, in the laboratory.
of flowrate. The downward force of gravity on the float
continuously opposes the upward force of the flowing fluid. Venturi Tube
With a change in flowrate, the float rises or falls in the Due to simplicity and dependability, the venturi tube
tapered tube until the size of the annular area between the flowmeter is often used in applications where higher turn
float and tube changes sufficiently to create a new down rates, or lower pressure drops are required than the
equilibrium position (hence variable area). There is one orifice plate can provide.
installation requirement - the measuring tube must be
vertical, to balance the float against the full force of gravity. In the venturi tube the fluid flowrate is measured by
The exact specification of a rotameter will vary slightly due reducing the cross sectional flow area in the flow path,
to the density and viscosity of the fluid or gas, i.e. a unit generating a pressure difference. After the constricted area,
purchased for measuring air flow will not read accurately if the fluid is passes through a pressure recovery exit section,
used for measuring CO2 flow. where up to 80% of the differential pressure generated at
the constricted area, is recovered.
Although shown with a visual indication, the height of the
float, and thus measured flow rate may be measured
electronically. Rotameters are often combined with a
needle valve so the flow can be adjusted at the point of
measurement (as shown in the bottom picture).

When measuring gases, the gas must be completely dry to

ensure the float does not stick.

194 General Certificate in Brewing

With proper instrumentation and flow calibrating, the The turndown ratios may be more than 100:1 if the turbine
venturi tube flowrate can be reduced to about 10% of its meter is calibrated for a single fluid and used at constant
full scale range with proper accuracy. This provides a turn conditions. Accuracy may be better than +/-0.1%.
down rate of 10:1.
These are commonly used in keg filling machines.
Orifice plate
PRESSURE GAUGES

Pressure gauges and switches are among the most often

used instruments. But because of their great numbers,
attention to maintenance and reliability is often
compromised and it is not uncommon in older plants to see
many gauges and switches out of service. This is
unfortunate because, if a plant is operated with a failed
pressure switch, the safety of the plant may be
compromised. Conversely, if a plant can operate safely
while a gauge is defective, it shows that the gauge was not
With an orifice plate, the fluid flow is measured through the needed in the first place. Therefore, one goal of good
difference in pressure from the upstream side to the process design is to install fewer but more useful and more
downstream side of a partially obstructed pipe. The plate reliable pressure gauges and switches.
obstructing the flow offers a precisely measured
obstruction that narrows the pipe and forces the flowing
TEMPERATURE
fluid to constrict.
A number of different types of thermometer may be used
The turn-down rate for orifice plates is less than 5:1. The
in a brewery or packaging plant.
accuracy is poor at low flow rates. A high accuracy depends
on an orifice plate in good shape, with a sharp edge to the Thermocouples
upstream side. Wear reduces the accuracy. Thermocouples consist essentially of two strips or wires
made of different metals and joined at one end. Changes in
Calorimetric
the temperature at that joint induce a change in
The calorimetric principle for fluid flow measurement is
electromotive force (emf) between the other ends. As
based on two temperature sensors in close contact with the
temperature goes up, this output emf of the thermocouple
fluid but thermal insulated from each other.
rises, though not necessarily linearly.

Resistance (RTD)
Resistive temperature devices use the fact that the
electrical resistance of a material changes as its
temperature changes. Two key types are the metallic
devices (commonly referred to as RTDs), and thermistors.
These devices are commonly used in automated breweries.
One of the two sensors is constantly heated and the cooling They have rapid response times. An example of a hygienic
effect of the flowing fluid is used to monitor the flowrate. In in-line sensor is shown below.
a stationary (no flow) fluid condition there is a constant
temperature difference between the two temperature
sensors. When the fluid flow increases, heat energy is
drawn from the heated sensor and the temperature
difference between the sensors are reduced. The reduction
is proportional to the flow rate of the fluid.

The calorimetric flowmeter can achieve relatively high

accuracy at low flow rates, and can be used where low
flows may be experienced at times, e.g. the beer supply to a
lane keg racking machine.
Infrared
Turbine flowmeter Infrared sensors are non-contacting devices. They infer
There are many different manufacturing design of turbine temperature by measuring the thermal radiation emitted
flow meters, but in general they are all based on the same by a material. They are sensitive to the roughness and
simple principle. If a fluid moves through a pipe and acts on colour of the surface, and normally have a range of
the vanes of a turbine, the turbine will start to spin and different settings available for selection. Due to the
rotate. The rate of spin is measured to calculate the flow. variation in the surface, these cannot be considered

Learning Material 2016 195

accurate, but are suitable for quick checks where for
instance thermal strips of the correct range are not
available.

They are self adhesive, but are removable, particularly

whilst still hot and so can be transferred to paper for long
term record.
Bimetallic strip
Bimetallic devices take advantage of the difference in rate They are available in a number of different temperature
of thermal expansion between different metals. These ranges, changing colour once the surface to which the label
devices are portable and they do not require a power is attached reaches the indicated temperature.
supply, but they are usually not as accurate as
thermocouples or RTDs and they do not readily lend Note that they are not very accurate so can only be used as
themselves to temperature recording. They are best used a guide to the maximum temperature reached.
inserted into a pocket, not directly into the product.

CONDUCTIVITY

Electrical Conductivity is the ability of a solution to transfer

(conduct) electric current. Conductivity is used to measure
the concentration of dissolved solids which have been
ionized in a polar solution such as water. The unit of
measurement commonly used is one millionth of a Siemen
per centimetre (micro-Siemens per centimeter or µS/cm).
When measuring more concentrated solutions, the units
are expressed as milli-Siemens/cm (mS/cm - thousandths of
a Siemen). 1000 µS/cm are equal to 1 mS/cm. Conductivity
is usually simply expressed as either micro or milli Siemens.
Fluid-Expansion
Perhaps better known as conventional liquid (mercury or Temperature plays a role in conductivity. Ionic activity, and
alcohol) in glass thermometers. Ideally, these should not therefore conductivity, is directly proportional to
be used in production plant due to the risk of breakage and temperature. The effect is predictable and repeatable for
contamination of the product by mercury or alcohol. most chemicals, but unique to each chemical. The effect is
However, if necessary, only alcohol in glass thermometers instantaneous and quite large (typically 1%- 3% / ºC)
should be used. Again ideally, the thermometer should sit compared to the reference value of 25ºC. Advanced meters
in a pocket to ensure isolation from the product. allow for custom reference temperatures, and / or measure
the temperature of the liquid and automatically
Fluid-expansion sensors do not require electric power, do compensate for the temperature.
not pose explosion hazards, and are stable even after
repeated cycling. On the other hand, they do not generate They are widely used for beer / water interface detection
data that is easily recorded or transmitted, and they cannot and for control of detergent strengths.
make spot or point measurements.
pH
Change-of-state
These are commonly used for validation of temperatures Because pH plays such a critical role in enzyme activity, and
achieved when sterilising plant, e.g. plate and frame filters, hence mash conversion, fermentation etc., accurate
as part of the routine quality checks, or during measurement is critical.
commissioning.
The methods for measuring pH fall roughly into a number
of categories. However for practical use in breweries, only

196 General Certificate in Brewing

the following are currently used:- The essential measurement is the difference between total
• Indicator methods. pressure at the bottom of the tank (hydrostatic head
• Glass-electrode methods. pressure of the fluid plus static pressure in the vessel) and
the static or head pressure in the vessel. The hydrostatic
Indicator methods pressure difference equals the process fluid density
One method involves comparing the standard color multiplied by the height of fluid in the vessel. The example
corresponding to a known pH with the colour of an above uses atmospheric pressure as a reference. A vent at
indicator immersed in the test liquid using buffer solution. the top keeps the headspace pressure equal to atmospheric
pressure. Where a tank is pressurised, a second sensor is
The other method involves preparing pH test paper which is used to measure the pressure of the gas and this value
soaked in the indicator, then immersing the paper in the deducted from the bottom sensor readout to give the fluid
test liquid and comparing its color with the standard color. height.
This method is simple, but prone to error. A high degree of
accuracy cannot be expected. Capacitance Transmitters
These devices operate on the fact that process fluids
Glass-Electrode Method generally have dielectric constants significantly different
The glass electrode method uses two electrodes, a glass from that of air or other gases used such as CO2. They are
electrode and reference electrode, to determine the pH of commonly used for CIP fluids but may still be found in
a solution by measuring the voltage (potential) between product tanks. They are not ideal here as they are difficult
them. to clean effectively, or may cause “CIP shadows” on the
vessel walls. They are also not normally able to detect
This method is the one most commonly used for pH when a tank is completely empty due to the length of probe
measurement, since the potential quickly reaches required and the potential for it to bend sue top turbulence
equilibrium and shows good reproducibility, and can be during filling.
used on various types of solution.

LEVEL SENSORS

Floats
Floats work on the simple principle of placing a buoyant
object with a specific gravity intermediate between those
of the process fluid and the headspace vapor into the tank,
then attaching a mechanical device to read out its position.
The float simply floats on top of the process fluid. While the
float itself is a basic solution to the problem of locating a
liquid's surface, reading a float's position (i.e., making an
actual level measurement) is still problematic. Early float
systems used mechanical components such as cables,
tapes, pulleys, and gears to communicate level. Magnet-
equipped floats are popular today.

They are not suitable for product, and due to complexity

are now rarely installed for other purposes. Load Cells
A load cell or strain gauge device is essentially a mechanical
Differential pressure support member or bracket equipped with one or more
sensors that detect small distortions in the support
member. As the force on the load cell changes, the bracket
flexes slightly, causing output signal changes.

To measure level, the load cell must be incorporated into

the vessel's support structure. As process fluid fills the
vessel, the force on the load cell increases. Knowing the
vessel's geometry (specifically, its cross-sectional area) and
the fluid's specific gravity, it is a simple matter to convert
the load cell's known output into the fluid level.

Load cells do not come into contact with the product and so
are hygienic. The vessel support structure and connecting
piping must be designed so the vessel movement due to
increase weight is not restricted by the pipework.

Learning Material 2016 197

The supporting structure's expansion or contraction, caused LEVEL SWITCHES
by uneven heating (e.g., morning to evening sunshine) may
be reflected as level. Load cell weighing system Capacitance, conductance and vibrating level switches may
requirements must be a paramount consideration be used in addition to or instead of variable level sensors.
throughout initial vessel support and piping design, or
performance is quickly degraded. Vibrating sensors
Vibrating level switches detect the dampening that occurs
Ultrasonic Level Transmitters when a vibrating probe is submerged in a process medium.
Ultrasonic level sensors measure the distance between the They may be used to detect liquids or solid materials such
transducer and the surface by measuring the time required as powders and grain. They provide excellent performance
for an ultrasound pulse to travel from a transducer to the as high or low level switches and can be mounted from the
fluid surface and back. The speed of sound depends on the tops or sides of tanks. Vibrating and tuning fork probes can
mixture of gases in the headspace and their temperature. tolerate a fair amount of material build-up without
The sensor temperature is compensated for (assuming that affecting their performance, unlike conductivity switches.
the sensor is at the same temperature as the air in the
headspace). They are extremely useful where there is foam formation as
they can distinguish between foam and liquid, unlike
conductivity probes, and are unaffected by films of highly
conducting liquid such as caustic remaining at the end of a
tank CIP scavenge cycle, and so can be used to accurately
determine when a tank is empty during burst delivery
cycles.

Capacitance sensors
To measure the liquid level, the level switch emits a signal
from the sensor tip into the tank. If the medium is
conductive (e.g. beer) then an insulated probe is used and
the capacitor is formed by the outer surface of the
insulation (“shorted” to the wall) and the electrode. This
capacity depends upon the dielectric value of the liquid,
They have also been used in beer, the sensor being located
which is well defined for most media. The capacitance is
in the base of the tank, but have only proven reliable in
directly proportional to the height of the medium.
filtered beer due to the attenuation due to the solids in
fermenting or unfiltered beer. There are a number of issues associated with these sensors:

Radar Level Transmitters • Coating or build-up of salts or other process

Through-air radar systems beam microwaves downward chemicals
from either a horn or a rod antenna at the top of a vessel. • Wicking and uneven coating of the electrode
The signal reflects off the fluid surface back to the antenna, • Corrosion
and a timing circuit calculates the distance to the fluid level • Non-conductive tanks
by measuring the round-trip time. • Splashing or bubbles/foam

In through-air radar systems, the radar waves suffer from Conductivity sensors
the same beam divergence that afflicts ultrasonic
transmitters. Internal piping, deposits on the antenna, and
multiple reflections from tank buildup and obstructions can
cause erroneous readings.

The signal generator in the circuit generates a signal on its

reference probe. If a current is detected by the sensor
terminal, then conductive liquid must be present.

A number of different length probes can be used to

determine different levels.

198 General Certificate in Brewing

17.2 Brewing Plant Maintenance - This is called ‘Condition Monitoring’ and specifically it is a
Approaches and Tasks maintenance process where the condition of equipment is
monitored for early signs of impending failure. Equipment
Maintenance is the management of activities that can be monitored using sophisticated instrumentation such
contribute to optimum levels of availability and as vibration analysis, oil analysis, laser alignment of shafts
performance of plant. in rotating equipment and thermal imaging. More
traditionally, temperature, over voltage or current and
The AIMS of maintenance are: liquid level has been monitored to warn of problems.
• To sustain the functionality of plant Equally monitoring can be manual often using the human
• To minimise downtime senses. Where instrumentation is used (automatic
• To provide a safe environment for personnel monitoring) actual limits can be imposed to trigger
operating/cleaning/maintaining the plant maintenance activity, generally through a computerised
• To protect product quality maintenance management system.
• To prove due diligence, for example for consumer
Predictive maintenance can also be known as Condition
safety
Based maintenance. A further variation can be Risk Based
• To ensure legal requirements are met, for example
maintenance where maintenance tasks are arranged to
environmental compliance
reflect the risk of failure based on predicted plant life and
• To protect the value of plant
plant history.
There are four approaches to maintenance.
Comments
1. No maintenance.
a) Whatever maintenance system is employed all activities
This is when no checking and no maintenance take place at
must be carried out safely and meet all legal requirements.
all.
To meet these requirements a system of ‘safe working
This applies to certain items like electrical components that practices’ should be employed to ensure that Health and
as and when they fail are discarded and replaced. This Safety is treated as a priority at all times. A system of safe
approach will only be appropriate in some circumstances. working practices would include items such as:
• Some form of permit to work.
2. Breakdown maintenance. • Use of the correct personal protective equipment.
This is when equipment is only attended to if it breaks • Interlocked guarding systems.
down. • Training
• System reviews
With this system, there is a big risk of lost production
because breakdowns often occur at the worst time. b) Most maintenance systems now employ computers for
recording information, issuing work and storing plant
It may be applicable if duplicate plant is installed; otherwise history. This also enables automatic electronic spares
a big stock holding of spares is needed. Breakdown ordering and easily obtainable financial information about
maintenance can also be known as Corrective maintenance. maintenance.
3. Preventative maintenance. c) The cost of engineering maintenance needs to be
This is where plant is maintained to a plan whether or not it controlled so annual budgets and regular reviews (normally
shows signs of wear. monthly) of expenditure are a pre-requisite for control
purposes. The normal costs for day-to-day maintenance
Usually components are replaced at the same time, for
activities are usually referred to as revenue items whereas
example pump glands or wear strips on conveyors.
the purchases of new plant like a hammer mill or filling
Planned maintenance can vary from a weekly inspection machine are capital items.
and oil top, through two or three day mini-overhauls, up to
The advantages and disadvantages of the various
a complete line or major item annual overhaul.
maintenance systems are detailed in the table below:
The concept is that unforeseen breakdowns are much less
likely to occur.
System Advantages. Disadvantages.
No maintenance. Easy to set up. Risk of plant
Preventative maintenance can also be known as Planned
unavailability at key
maintenance or Planned Preventative maintenance.
Appropriate in times.
some
4. Predictive maintenance.
circumstances High cost of
This is where plant condition is monitored and a prediction replacement parts.
is made about when it is likely to break down. A
maintenance programme is developed based on the
information gathered.

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 Breakdown No unnecessary Risk of plant 17.3 Performance Improvements
maintenance. work on the unavailability at key
plant. times. Poor plant performance and plant failure in one form or
another has a major impact on business performance;
High cost of spares. consequently systems that improve plant reliability are
becoming widely implemented.
Preventative Work done on the Expensive.
Maintenance. plant at a Three process improvement initiatives are:-
convenient time. Plant may be
worked on • Reliability Centred Maintenance (RCM) where teams of
Less likelihood of unnecessarily. key personnel for example maintenance engineers and
breakdowns. plant operators decide on how the plant can fail, the
consequences of failure and finally the most appropriate
Predictive Most effective Complex
maintenance procedures that will reduce the incidence
maintenance. use of information system
engineering needs to be of failure.
resources. maintained.
• Total Productive Maintenance (TPM) where the plant
Work done on the technicians/operators are trained to pay strict attention
plant at a to detail, to take great pride in their equipment and to
convenient time. tolerate zero plant defects.

Less likelihood of • Workplace Organisation (5S) where technicians or

breakdowns. operators focus on achieving and maintaining visual
order and cleanliness. 5S aims to remove unneeded
items and organise the workplace so that it is easy for
Types of tasks associated with engineering maintenance. the operatives to carry out their tasks and maintain a
clean and orderly environment.
Whether the conditions are breakdown, planned,
preventative or associated with an overhaul the majority of In more detail:
engineering maintenance tasks can be linked to the
following headings: Reliability Centred Maintenance (RCM)

Mechanical The principles which define and characterise RCM are:

Lubrication
• a focus on the preservation of system function;
Electrical
Software/hardware • the identification of specific failure modes to define
Calibration loss of function or functional failure;
Inspection
Condition monitoring • the prioritisation of the importance of the failure
Cleaning of plant modes, because not all functions or functional failures
Health and Safety are equal;
Recording and updating information
• the identification of effective and applicable
Notes: maintenance tasks for the appropriate failure modes.
Specify important pieces of mechanical and electrical plant (Applicable means that the task will prevent, mitigate,
that you are familiar with. detect the onset of, or discover, the failure mode.
Effective means that among competing candidates the
What method of maintenance is employed to ensure that
selected maintenance task is the most cost effective
these pieces of plant or equipment perform as required?
option).
Describe in detail a variety of maintenance tasks that are
performed under the headings shown above. These principles, in turn, are implemented in a seven-step
process:
How much does engineering maintenance cost on an annual
basis. How is the budget controlled? 1. The objectives of maintenance with respect to any
Find out the costs of major capital plant items. particular item/asset are defined by the functions
of the asset and its associated desired
Describe how health and safety and other legal
performance standards.
requirements are met under the engineering maintenance
2. Functional failure (the inability of an item/asset to
banner
meet a desired standard of performance) is
identified. This can only be identified after the
functions and performance standards of the asset
have been defined.

200 General Certificate in Brewing

 (3) Plan maintenance: have a systematic approach to all
3. Failure modes (which are reasonably likely to maintenance activities. This involves the identification of
cause loss of each function) are identified. the nature and level of preventive maintenance required
4. Failure effects (describing what will happen if any for each piece of equipment, the creation of standards for
of the failure modes occur) are documented. condition-based maintenance, and the setting of respective
5. Failure consequences are quantified to identify the responsibilities for operating and maintenance staff. The
criticality of failure. (RCM not only recognizes the respective roles of "operating" and "maintenance" staff are
importance of the failure consequences but also seen as being distinct. Maintenance staff is seen as
classifies these into four groups: Hidden failure; developing preventive actions and general breakdown
Safety and environmental; Operational and Non- services, whereas operating staff take on the "ownership"
operational.) of the facilities and their general care. Maintenance staff
6. Functions, functional failures, failure modes and typically moves to a more facilitating and supporting role
criticality analysed to identify opportunities for where they are responsible for the training of operators,
improving performance and/or safety. problem diagnosis, and devising and assessing maintenance
7. Preventive tasks are established. These may be practice.
one of three main types: scheduled on-condition
tasks (which employ condition-based or predictive (4) Train all staff in relevant maintenance skills: the defined
maintenance); scheduled restoration; and responsibilities of operating and maintenance staff require
scheduled discard tasks. that each has all the necessary skills to carry out these
roles. TPM places a heavy emphasis on appropriate and
Although one of the prime objectives of RCM is to reduce continuous training.
the total costs associated with system failure and
downtime, evaluating the returns from an RCM program (5) Achieve early equipment management: the aim is to
solely by measuring its impact on costs hides many other move towards zero maintenance through "maintenance
less tangible benefits. Typically these additional benefits fall prevention" (MP). MP involves considering failure causes
into the following areas: and the maintainability of equipment during its design
stage, its manufacture, its installation, and its
(1) improving system availability; commissioning. As part of the overall process, TPM
(2) optimising spare parts inventory; attempts to track all potential maintenance problems back
(3) identifying component failure significance; to their root cause so that they can be eliminated at the
(4) identifying hidden failure modes; earliest point in the overall design, manufacture and
(5) discovering significant, and previously unknown, deployment process.
failure scenarios;
(6) providing training opportunities for system TPM works to eliminate losses:
engineers and operations personnel;
• Downtime from breakdown and changeover times
(7) identifying areas for potential design
• Speed losses (when equipment fails to operate at its
enhancement;
optimum speed)
(8) providing a detailed review, and improvement
• Idling and minor stoppages due to the abnormal
where necessary, of plant documentation.
operation of sensors, blockage of work on chutes,
etc.
Total Productive Maintenance (TPM) • Process defects due to scrap and quality defects to
be repaired
TPM aims to establish good maintenance practice through • Reduced yield in the period from machine start-up
the pursuit of "the five goals of TPM": to stable production.

(1) Improve equipment effectiveness: examine the

effectiveness of facilities by identifying and examining all Workplace Organistion (5S)
losses which occur - downtime losses, speed losses and
defect losses. 5S can be broken down into 4 activities and one conviction
to continue with the 4 activities. 5S originated in Japan and
(2) Achieve autonomous maintenance: allow the people there are many translations of the Japanese words for 5S –
who operate equipment to take responsibility for, at least a common set is listed below:
some, of the maintenance tasks. This can be at:
• The repair level (where staff carry out instructions • “Sein” - Sort
as a response to a problem). • “Seiton” - Set in order
• The prevention level (where staff take pro-active • “Seiso” - Shine
action to prevent foreseen problems). • “Seiketsu” - Standardise
• Improvement level (where staff not only takes • “Shitsuke” - Sustain
corrective action but also propose improvements
to prevent recurrence).

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Sort The direct changes resulting from carrying out 5S are
The aim of Sort is to remove from the workplace items workplace tidiness and orderliness; these have a beneficial
that are not needed, such as tools, materials and parts, effect on a large number of other factors which improve
and to identify what items are needed to perform the efficiency. These range from reduced time searching for
operations at each of the workstations. tools, reduced changeover time, reduced inventory to
reduced cycle time.
Set in order
Set in order is the part of the 5S technique that All three methods rely on detailed records and analysis and
arranges materials, components and tools in such a ‘problem solving’ in a teamworking environment. These
way that the operatives can easily access them. An methods also depend on the teams being supported by
example of this is a shadow board, where each tool has senior management.
its own place and can be easily located. Additionally, if High initial set-up costs ultimately enable the achievement
an empty place exists on the board the missing tool can significantly improved and sustainable plant reliability.
easily be identified.
Comments:
Shine There are a number of performance improvement
For Shine, the workplace needs to be kept clean so that initiatives that are similar to RCM, TPM and 5S. The
it is safe for the operators to carry out their tasks and majority of them focus on improving plant performances by
move around their workstation. This also benefits combining a number of simultaneous initiatives and
productivity as the easier it is for the operatives to typically include the following:
move around the quicker it is for them to carry out
their tasks. • ‘Organisational Changes’.
• Computerised systems for maintenance,
Standardise measuring plant breakdowns and performance.
Formalise the Sort, Set in order and Shine activities to • Predictive maintenance techniques.
standardise their practice so that all involved can • Cleaning-inspection-lubricate.
achieve the same results. Application of this will ensure • Teamworking.
that the workplace is clean and organised. • Improvement analysis (various techniques).
• Defining roles, responsibilities and accountabilities.
Sustain • Training and education.
The sustain activity will ensure that 5S is ingrained in
the organisation culture. Sustain aims to keep the Notes:
workforce focussed on carrying out 5S activities on a Describe the typical features of a performance improvement
regular basis, usually daily. Performance is measured to initiative you are familiar with.
maintain consistency and ensure that all involved are
informed of their progress. Describe your role and responsibilities, who you consult and
who you inform.

202 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 203

Section 18 Utilities – Water & Effluent

18.1 Water sources and treatments

Introduction

Water is the principal ingredient in beer, accounting for Product water (brewing liquor and water used in the
around 94% of the content of a normal 5% alcohol beer. As production of beer, i.e. it will eventually be consumed by
well as being the principal ingredient in beer, water has a the customer) makes a major contribution to the quality of
number of important functions in the brewing process. It is the beer that is produced. Salts dissolved in the water affect
therefore important that each brewery has a reliable supply the beer’s flavour, influence the pH (acidity/alkalinity) of
of good quality water. the process and the final product and they provide essential
trace elements for yeast growth.
Generally it takes between 3 and 20 hectolitres of water to
produce 1 hectolitre of beer depending on the efficiency of In general:-
the brewery and the range of packaging tasks. The
adjudged minimum ratio of consumption, allowing for • Chlorides give beer a fuller flavour.
unavoidable losses, is approximately 1.4:1. In practice the • Sulphates give the beer a dry sulphury character.
minimum consumption is generally in the range 2.5:1 to 5:1 • Calcium helps to reduce the mash pH and is needed
depending on the operations carried out by the particular by the yeast and for beer stability.
brewery, with best practice sites down to 2 to 2.2:1. The
• Carbonates raise pH and form scale on heating
ratio is normally measured in hectolitres water per
surfaces.
hectolitre beer produced (hl/hl).
• Iron gives beer a metallic flavour and will form
Characteristics and quality of brewery water supply hazes.
• Nitrates indicate surface water or sewage
A brewery water supply should have the following contamination.
characteristics: • Magnesium and zinc are trace elements required by
Characteristic Standard the yeast.

Appearance. Clear and colourless. The following are overviews of water ionic compositions
Wholesomeness/ Freedom from undesirable flavours or used for different beers.
potability. odours which may be derived from
organic or inorganic sources, or from Pilsener type lagers
poisonous material, metals or (usually)
organic compounds. • Soft water, low mineral content.
Mineral salt and Contents that meet the brewing and • Low levels of carbonates, helping to bring out
metallic content. process requirements. The quantity and delicate flavours.
type will affect the pH, which should • Low calcium ion level.
ideally be neutral or slightly acidic.
Ales (bitters, pale ales)
Heavy metal ions, most commonly
ferrous or ferric ions must be absent.
• Sulphates > chlorides to bring out bitter flavours.
Microbiological Freedom from any micro-organisms that • Low carbonates (< 30 ppm) to help achieve low pH.
standard. would spoil the beer or affect the people
• Higher calcium (> 135 ppm) for flavour and pH.
who drink it. The presence / absence of
coliform bacteria are a commonly used
Milds, stouts, porters
indication of microbiological purity. They
should be absent from a 100 ml sample.
• Chlorides > sulphates for enhanced fullness &
Organic The water should be free of dissolved sweetness.
compounds. organic compounds. These indicate
• Carbonates medium (< 70 ppm).
contamination with, for example sewage,
industrial (e.g. oils, detergents, phenolic • Calcium levels lower around 75 ppm for mild and 30
compounds) or agricultural runoffs ppm for Stouts.
(biocides, fertilisers) and may require
extensive (and expensive) treatment to Specific mineral ion contents will of course vary from
make fit for brewing purposes. brewery to brewery, and beer types brewed within the
Reliability of There must be water available at all same brewery may have different mineral salts added to
supply. times, ideally having consistent change the ionic composition. The following table shows
specifications as outlined above. examples of ionic composition of water from a number of
brewing centres.

204 General Certificate in Brewing

 Borehole Water:
Ions in ppm Burton Munich Dublin Pilsen
on Rain Bore hole
Trent
Type of Beer Pale Ale Dark Irish Light
Lager Stout Lager
Top soil
Total dissolved 1300 280 340 50
solids
Ca - calcium 352 106 132 10 Sub soil

Mg – 24 30 18 1
magnesium
Water bearing rock
Na – sodium 54 6 12 2

Cl – chloride 16 2 15 5 Impervious rock

SO4 – sulphate 820 8 15 6

Surface Water:
NO3 – nitrate 18 3 5 Na
Rain
*HCO3 – 320 120 175 15
bicarbonate

Main salts CaSO4 CaCO3 & CaSO4 &

MgCO3 CaCl
Reservoir

* Before being suitable for brewing, the "temporary

hardness" or bicarbonates (HCO3) have to be removed.
Hardness is usually expressed in terms of calcium carbonate
Water can be sourced directly from underground wells
(CaCO3).
(boreholes) or from a surface supply such as a reservoir.
Further details of the quality aspects of water are discussed Normally, surface water will have been treated at a
in the following section. municipal treatment works before distribution to the
brewery and other domestic and commercial users.
Sources of water for a brewery
Some of the key differences in untreated water quality from
A plentiful supply of water is essential to the brewery; this boreholes and surface water, along with treated municipal
is why, in the past, breweries were built in areas that had supply water are shown in the following table.
their own sources, usually in the form of wells or boreholes.
These original sources are still used in some plants while Comment Borehole Surface Municipal
others have to rely on the local water authority for their water supply
Temperature
supply.
May need to Consistent Varies with Rather
The nature of the water source will affect the quality of the be cooled to season. variable,
allow use in depending on
beer and this has resulted in some areas being famous for
production Cooling may source and
their beers. Examples are Burton-on-Trent for strong bitters
processes – be required method and
and Pilsen for fine lagers. The quality of the water will also additional particularly distance of
affect the efficiency of the processes where it is used, for costs during transport to
example in boiler feed water or in plant cleaning systems. summer. brewery.

As water falls to the ground as rain or snow, it is free of Turbidity

minerals, but may contain particles of soot and grits, and Turbid water Generally low Varies, can be Normally very
will contain some dissolved gases such as SO2 and CO2, the will need to be (borehole not high, consistent
latter being particularly important. Whilst some is filtered before generally especially assuming
absorbed by plants or evaporates directly, much will run off use – considered after heavy municipal
into rivers and lakes, either natural or artificial, from where additional suitable supply rain following supply treated
it may be recovered for use. Some will also percolate cost. if the water is dry periods. to WHO
through the ground and porous subsurface rock layers to not clear). guidelines for
form aquifers where it meets a layer of impermeable rock. potable water.

Boreholes may be sunk into the aquifers for recovery of the

water.

Learning Material 2016 205

 Colour Taints
Indicates high Generally low Varies, can be Normally very Flavour or Usually very May be Likely to be low
dissolved (borehole not high, consistent aroma may low (borehole present, because of
mineral or generally especially assuming carry through not generally particularly treatment by the
organic matter considered after heavy municipal to final product considered because of water authority.
content. suitable supply rain following supply treated and both actual suitable supply agricultural or
if the water is dry periods. to WHO taints and if the water is industrial However,
This needs to not guidelines for precursors contaminated) runoff. chlorine content
be removed to colourless). potable water. must be . (for sterilisation)
ensure it does removed prior is often
not affect the However, in to use. unacceptably
brewing spite of high.
process / final complying Many
product. with WHO compounds
guidelines, can have low
still vary, and sensory
can be high, thresholds.
especially
after heavy Microbiological
rain following Must be Usually very Likely to be Likely to be low
dry periods. removed / low (borehole high because because of
killed to not generally of agricultural treatment by the
Mineral content
prevent considered runoff. water authority.
Can affect Will contain Varies, but Depends on
contamination suitable supply
brewing some of the likely to be whether the
/ slime build if the water is
process and soluble low unless source is
ups. contaminated.
flavour of material agricultural borehole or
beer. present in the chemicals are surface. Any
Consistency
rock strata being washed anomalies
of supply
May also where the off the land. should be
Required to Very good Can be Microbiologically,
adversely water is held. known if the
allow over long variable clarity and aroma
affect utilities, supplies
Depending on consistent periods of especially in - very good
particularly if alternate.
the type of treatment for time. periods of because of the
mineral
rock, it could brewing & drought, or water authority’s
content high.
be high or low utilities without rain legal obligations.
in minerals. excessive costs. immediately
following However mineral
Hardness drought. content may vary
Can affect Depends on Varies – Depends on with water
brewing the type of usually low, whether the source, especially
process and rock, may be but may vary source is if a number are
flavour of high or low, with season / borehole or used.
beer. but is rainfall. surface.
generally
May also consistent.
adversely
affect process
water and
The composition of brewing water has now been
utilities, determined scientifically, it so can be adjusted to brew a
particularly if range of different beer types, even though the source water
high. may not be particularly suitable. Water which would in the
past have been considered totally unsuitable for brewing
Nitrate can now be treated to allow its use, allowing breweries to
Must be Usually low. May be high Depends on be built close to centres of population for ease of transport,
removed to due to whether the
rather than according to the water type available.
reduce risk of agricultural source is
nitrosamine runoff borehole or
formation. surface, but
generally low
due to
treatment
process. (+
legal
requirements)

206 General Certificate in Brewing

The following sections describe the different methods When exhausted, the carbon has to be replaced with a
available to treat water from virtually any source and fresh batch. It cannot be regenerated.
ensure it is usable in breweries, both for the brewing water
itself, and all other activities associated with the brewing Water sterilization
and packaging processes. Most of the water used for brewing will be heated prior to
mashing and sparging, and then boiled in the kettle thus
The basic principles of water treatment plant ensuring it is free from non-sporulating micro-organisms.
However additional water used for diluting wort or beer or
Treatment depends on the source and quality of the water, rinsing equipment may not be microbiologically sterile and
and whether it is to be used of brewing, or for cleaning and it may be necessary for the brewery to carry out some
heat transfer, boiler feed water etc. sterilisation treatment of this water.

Brewing water treatment depends on the kind of source The method of water sterilisation depends on the level of
and the quality of the water, and the type of beer to be infection and on the subsequent use of the water. If the
brewed. Treatment must ensure removal of any suspended water is heavily infected it may require filtration followed
solids and organic matter, on sterilisation and adjustment by a secondary sterilization treatment using one of the
of the ionic content if necessary. Where water is to be used following methods.
post fermentation then the oxygen must also be removed.
• Chlorination
Water filtration • Chlorine dioxide
Water from deep boreholes is usually clear and colourless, • Ozone
but surface water may need treatment. This is usually • Ultraviolet light
achieved by - • Ultraviolet light + silver addition
• Sterile filtration (0.2 - 0.45 micron) (note this is not
Sand filtration
pharmaceutically sterile, but commercially
Pressure type (tank) filters are normally used. The
acceptable for brewing operations)
suspended solids are removed periodically by backwashing
the filter. To improve filtration efficiency, a layer of Chlorine
anthracite is normally placed on top of the sand. If the water will become part of the beer, or come into
contact with the wort or beer, chlorine, added either as gas,
If iron and / or manganese are present, the sand media is
or as hypochlorite, must not remain in the water at point of
mixed with a catalyst to speed up the oxidation of the
usage, because of the risk of off flavours. If used, it must be
soluble ferrous iron, converting it to insoluble ferric iron,
removed before the point of final use, normally by passing
which is then filtered out.
through an activated charcoal filter.
Supplies which contain colour due to the presence of
Chlorine dioxide
organic matter are clarified by coagulating the organic
Chlorine dioxide works as an effective oxidising agent. It is
matter with alum or aluminium sulphate and
typically used for sterilising water by addition at up to 0.2
polyelectrolyte. The floc formed by the chemicals attracts
ppm. Higher rates are sometimes used, up to 0.5 ppm for
the colloidal particles responsible for forming the colour
example for pasteuriser and CIP water, but if used to
which are then filtered out. Where the water contains high
sterilise dilution water, or as flush water which may come
levels of solids, the coagulation may also be carried out in
into contact with product, a maximum of 0.2 is advised due
separate settling upflow tanks.
to potential flavour / aroma off flavours.
If the incoming supply only periodically suffers from
Chlorine dioxide may also be used at up to 5 ppm as a
suspended solids, cartridge type filters may be used instead
terminal sterilant, though in this case, it must be flushed off
as these can be considerably smaller and thus cheaper.
with suitable sterile water (e.g. max 0.2 ppm ClO2 or UV
Carbon filtration treated water).
In addition to solids removal, the water may be carbon
Ozone
filtered to remove flavour taints like chlorine and organics
This is a strong oxidising agent which kills off micro-
such as trihalomethanes. These use granular activated
organisms. It is an unstable oxygen molecule comprised of
charcoal, which are periodically back-flushed with water to
three atoms of oxygen, formed by passing clean air through
remove any fines and suspended matter.
a high voltage discharge tube. It decomposes rapidly,
Typical surface area for activated carbon is between 500 reverting to normal oxygen, normally in minutes. It leaves
and 1000 square metres per gram, depending largely on the no residue, and oxidizes organics leaving little or no off
raw material it was produced from. Organic materials are flavour. Dosage rates are 0.1 to 4 mg / litre, with exposure
removed by adsorption. Disinfectants such as chlorine are times of 4 to 10 minutes.
removed by catalytic reduction. The chlorine capacity of
It is not currently widely used for sterilising brewing or
new activated charcoal is approximately 1 kg chlorine per
dilution water, but is more commonly used for sterilizing
kg charcoal.
washdown water and filler external rinse water. It is highly
Learning Material 2016 207
aggressive to many gaskets and “rubber” membranes. Hardness is defined as a property of water which enables it
Some brewers have been using this for final sterilising to "collapse" soap lather by forming insoluble salts of fatty
rinses in CIP systems. acids.
• Hardness can lead to scale developing on brewing
Ultra-violet light vessel surfaces, which can lead to microbiological
UV light in the wavelength of 200 to 280 nm destroys the contamination build up / retention in the scale.
DNA in micro-organisms provided a sufficient level of light • Hardness causes scaling in wort kettles, boilers and
to ensure adequate dose rate is applied. Because there is hot water installations reducing the thermal
no residual action, the effect is limited to the point of efficiency.
application, and it must be possible to clean and sterilize • Hardness increases the consumption of detergents,
the distribution system after the point of treatment. an in particular the chelating agents of the
Because there is no residual action, it is also essential to detergents which dissolve or keep dissolved, the
ensure no ingress of contaminants between the point of mineral salts responsible for the above problems.
treatment and the point of use. Water should be treated • Temporary hardness makes the water alkaline and
immediately before use. To be effective the water must be therefore is liable to increase the pH throughout the
colourless and free from suspended material or the brewing process.
sterilisation will be ineffective. In order to ensure the • Hardness depends almost entirely on the calcium
consistent clarity of the water some form of water pre- and magnesium ionic content of the water.
treatment is invariably required. • The fraction of hardness remaining after boiling is
called “permanent hardness” and consists mainly of
Some other industries add silver to the water to ensure a
salts of sulphate, chloride, calcium and magnesium.
residual secondary sterilising effect. However, this is not
Permanent harness may also be termed non-alkaline
used within the brewing industry as with care, adequate
hardness. This type of harness has little effect on
sterility can be achieved by application of UV alone.
the pH of the water.
Sterile filtration • Temporary hardness is due to the carbonate and
Water may be filtered to produce sterile water at point of (principally) the bicarbonate salts of calcium and
use. For the purposes of breweries, it is considered magnesium. These are precipitated during boiling,
necessary to filter through a 0.45micron absolute (or finer) hence the term. Water with high temporary
filter. Although this will not produce water to hardness tends to be more alkaline.
pharmaceutical standards of sterility, it is generally • Total hardness is the total hardness attributable to
considered adequate for breweries as any micro-organisms both the temporary harness and the permanent
that pass through are not pathogenic and will not grow in hardness
beer, to create off flavours, hazes, or illness of the
consumer. As noted above, not only may it be necessary to treat
brewing water, but it is often necessary to treat boiler feed
Note that prior to “sterile” filtration, it is necessary to water, since hard water leads to a build-up of scale with a
ensure the water is filtered, typically with a 5 and or 1 loss in boiler efficiency.
micron filter first to ensure the fine filter does not get
blocked too rapidly. The methods used in a brewery to treat the source water
will be determined by a number of factors, including
As with UV treated water, because there is no residual • The number and type of different beers to be
chemical sterilant effect, it is essential to ensure the brewed.
distribution system can be adequately cleaned and • The amount of temporary hardness
sterilised. For this reason sterile filtration is generally only • The amount of permanent hardness
used for low volumes, and immediately before the point of • Other mineral salts dissolved in the water, and their
use. effects on
o The beer being brewed
Reverse osmosis systems produce sterile water, but this is o The brewing process itself
not its primary function, and will be discussed in the o Utilities such as steam raising
following sections under mineral ion adjustment.
Removal of hardness by boiling
Water softening / de-ionization
Boiling the water breaks down the soluble calcium
Water may be unsuitable for brewing or other production bicarbonate and magnesium bicarbonate into the insoluble
processes because of the mineral ions present in the source carbonates, thus
water. The type and quantity of mineral ions dissolved in
the water will determine the type of treatment required to Heat
remove or adjust the mineral content. One of the key Ca(HCO3)2  CaCO3 ↓ + H2O+ CO2 ↑
factors is the degree of, and type of hardness.

208 General Certificate in Brewing

The treatment also removes the chlorine and sterilises the De-ionisation
water. However, this is an expensive process as it is It is not common for brewing water to be treated using ion
necessary to boil all the water used for brewing (mashing, exchange. However boiler feed water treatment varies
sparging and dilution) for around 30 minutes, and tends to with the type of boiler, but usually the choice is between
be used in microbreweries only for this reason. It can chemical treatment with lime and more commonly, by ion
create large quantities of scale, particularly on the heating exchange.
surfaces which must be regularly removed to ensure good
thermal efficiency. De-ionisation (removal of the salts) in ion exchange
columns is common in breweries. The columns contain
Note that this only removes the temporary hardness, and special resins that are capable of exchanging the unwanted
cannot be considered a suitable treatment on its own if the ions for harmless ones. The resins can be regenerated when
water contains considerable permanent hardness, or other exhausted, usually by washing through with mineral acids.
undesirable mineral salts. In the plant illustrated below, carbonates are removed in
ion exchange columns and CO2 is formed. This is removed in
Lime addition the degassing towers.
Lime reacts with soluble calcium bicarbonate to form
insoluble carbonate, as follows A typical water softener has a pressure tank partially filled
with ion exchange resin. The resin consists of highly porous,
Ca(HCO3)2 + Ca(OH)2  2CaCO3 ↓ + 2 H2O
plastic beads loaded with "exchange sites" that
The water must be allowed to stand for a considerable time preferentially remove hardness (typically calcium and
to allow the precipitated carbonate to settle, or be passed magnesium) ions and replace them with sodium, a "soft"
through settling systems. Again, this only removes the ion.
temporary hardness, and cannot be considered a suitable
At the beginning of the softening cycle, sodium ions occupy
treatment on its own if the water contains considerable
the resin's exchange sites. As water passes through it, the
permanent hardness, or other undesirable mineral salts.
resin's stronger attraction for the hardness ions causes it to
Acid treatment take on the hardness ions and give up its sodium ions. Iron
Sulphuric acid (H2SO4), hydrochloric acid (HCl) or and manganese are considered hardness and they are
removed also, provided they are in solution. Ion exchange
phosphoric acid (H3PO4) may be used to remove carbonate.
cannot remove suspended matter.
Where the calcium acid salt is insoluble, part of the calcium
content will be removed as well (as shown below). The type As water flows downward through the resin bed, the resin
of acid used will influence the ionic composition of the at the top of the bed gives up its sodium first. The exchange
water. Typically sulphuric acid is used as it is cheaper than process is not instantaneous, so exchange occurs in a band
phosphoric acid, and not as corrosive to stainless steel as called a "reaction zone". When the reaction zone's leading
hydrochloric acid. edge reaches the bottom of the resin bed and hardness
passed into the service line, the resin has become
Ca(HCO3)2+ H2SO4  CaSO4 ↓ + 2H2O + 2CO2 ↑ "exhausted" and it must be regenerated before it can
remove hardness again.
CaCO3 + H2SO4  CaSO4 ↓ + H2O + CO2 ↑

It is normally necessary to pass the treated water through a

degassing column to strip out the CO2, and to allow settling
time to allow the insoluble calcium sulphate to settle out.

Again, this only removes the hardness attributable to the

carbonates and bicarbonates, and cannot be considered a
suitable treatment on its own if the water contains
considerable permanent hardness due to for example
calcium sulphate, or other undesirable mineral salts.

Distillation The regeneration cycle starts with backwash, an upward

This process involves boiling the raw water to create pure flow that loosens the resin bed and flushes out suspended
water vapour and then condensing back to the liquid in a particles. Regeneration is carried out by passing a solution
separate collection system. The dissolved mineral salts of sodium chloride (salt) solution through the resin. A large
remain in the boiler. Freshly distilled water is sterile, but excess of sodium ions causes the resin to release its hold on
volatile impurities such as ammonia and a variety of organic hardness ions picked up during the preceding service cycle
compounds can carry over into the distillate. Because and returns the resin to its sodium state. This is followed
distillation requires such high energy (heat) input, it is by a rinse to displace spent brine from the resin. It also
generally only used for producing distilled water for the carries the hardness removed from the resin to drain.
laboratories. Where high purity water is required in larger
volumes, reverse osmosis is generally used.
Learning Material 2016 209
 BASIC RESIN (Rb)
RbOH + HAn  RbAn + H2O

The hydroxyl ion (OH-) reacts with the hydrogen ion (H+) to
produce a very pure water similar to distilled water in
mineral ion composition, but it may still contain an organic
residues, and silicates from the source water.

When all the sites on the exchange resins are saturated

they are regenerated with dilute acid or alkali as
appropriate.

Reverse Osmosis
Full demineralisation can also be achieved by the use of
membrane filters for Reverse Osmosis. Reverse osmosis,
commonly referred to as RO, is a process where water is
demineralized or deionized by pushing it under pressure
Ion Exchange through a semi-permeable membrane.

With the appropriate selection of membrane, water can be

The disadvantages of water softening become apparent totally de-mineralised and have bacteria, trihalomethanes
when high-quality water is required. Softening simply (THMs), some pesticides, solvents and other volatile organic
exchanges the hardness ions in the water supply for compounds (VOCs) removed.
normally less-troublesome sodium ions. Since the treated
water contains sodium instead of calcium or magnesium, To help understand what RO is, it is useful to have a basic
and the sodium salts are not scale forming it is often used understanding of Osmosis. This is a naturally occurring
for softening water for boiler treatment or CIP. On its own phenomenon where water from a weaker saline solution
it is not suitable for treating brewing water e.g. mashing / will tend to migrate to a strong saline solution. Examples of
sparging / dilution water, but it may be used as a pre- osmosis are when plant roots absorb water from the soil
treatment for further ion exchange. and our kidneys absorb water from our blood.

Demineralisation A semi-permeable membrane is a membrane that will allow

Demineralisation replaces the sodium ion exchange resin some atoms or molecules to pass but not others. An
with a hydrogen ion exchange resin making it possible to example is Gore-tex clothing fabric that contains an
swap the calcium and magnesium (and any sodium) ions for extremely thin plastic film into which billions of small pores
hydrogen. have been cut. The pores are big enough to let water
vapour through, but small enough to prevent liquid water
The dissolved salts are converted into their corresponding from passing.
acids instead of sodium salts. The water cannot be used
until the acids have been removed or neutralised. It is Reverse osmosis is the process of osmosis in reverse.
possible to add alkali such as lime or dilute sodium Whereas osmosis occurs naturally without energy required,
hydroxide to neutralise the acid, but as this would add to reverse the process of osmosis you need to apply energy
more (undesirable) ions, the water is passed through an to the more saline solution. A reverse osmosis membrane
anion exchange resin which exchanges the sulphate, allows the passage of water molecules but not the majority
carbonate and chlorides for the hydroxyl ion (OH-). The salt of dissolved salts, organics, or bacteria. However, you need
represented by MAn (metal anion) is absorbed on to the to 'push' the water through the reverse osmosis membrane
resins: by applying pressure that is greater than the naturally
occurring osmotic pressure allowing pure water through
ACID RESIN (Ra) while holding back a majority of contaminants.
RaH + MAn  RaM + Han

210 General Certificate in Brewing

 There are a number of methods of producing deaerated
liquor.
• Stripping at high temperature and atmospheric
pressure
• Vacuum stripping at low temperature
• Gas stripping with nitrogen or CO2 (or a mixture)
• Membrane gaseous exchange
• Chemical methods (for boiler water)

High temperature stripping

o
Water is heated to 105 C. It is then sprayed through
nozzles into a tank at atmospheric pressure. This gives a
fine mist of water, subject to flash evaporation which
releases the dissolved gases. This method of deaeration is
not as common as a few years ago due to the energy costs.
When pressure is applied to the source water, using a high Due to the high temperature, it is often not considered
pressure pump, the water molecules are forced through the necessary to install additional water sterilizers after the
semi-permeable membrane leaving almost all the dissolved plant.
salts and all bacteria behind in the reject stream. The
amount of pressure required depends on the salt Vacuum stripping
concentration of the feed water. The more concentrated The principle is just the same as at high temperature.
the feed water, the more pressure is required to overcome Water boils at low temperatures the lower the atmospheric
the osmotic pressure. pressure. By applying a vacuum to the tank into which the
water is being sprayed, the boiling point is substantially
The desalinated water that is demineralized or deionized, is reduced, and thus far less thermal energy is required. The
called permeate (or product) water. The water stream that o
process is carried out at 1 or 2 C above the boiling point at
carries the concentrated contaminants that did not pass the selected low pressure.
through the RO membrane is called the reject (or
concentrate) stream. Gas stripping
In one method, this is achieved by saturating the water with
An RO system employs cross flow filtration rather than
nitrogen (or CO2) and then allowing the nitrogen to flash
standard filtration where the contaminants are collected
off, carrying the dissolved oxygen with it. This gives a ten-
within the filter media. To avoid build-up of contaminants,
fold reduction in a single pass, so that a number, typically
cross flow filtration allows water to sweep away
two or three, are used in practice.
contaminant (mainly mineral salts) build up so keep the
membrane surface clean. The pore sizes in the membrane An alternative is to stream water downwards through a
determine the mineral salts that are allowed to pass packed stripping column against a counter-current of inert
through the membrane. gas (CO2 or nitrogen). The water is sprayed into the top of
the de-aerating column and it slowly trickles down the
Water deaeration
packed columns. The upward flowing CO2 (N2) ensures the
release of the oxygen. At the outlet of the system the water
It is common to brew beer at ‘high gravity’ and to dilute the is saturated with CO2 (N2).
beer to its specified alcohol content at a later stage, for
example post filtration. The water used for dilution has Water for high gravity beer dilution is normally carbonated
specific quality requirements. immediately after deaeration if CO2 has not been used as
the stripping gas. The use of nitrogen is often considered
• It must be sterile. preferable as it is often cheaper than CO2, certainly if
• The ionic composition should be similar to the bought in CO2, and the small quantity of N2 dissolved (circa
brewing liquor, or be demineralized, but certainly 10 ppm) helps to improve foam stability on beer dispense.
with a lower calcium level than brewing liquor to
reduce the risk of oxalate haze formation. The following diagram shows the general layout of a gas
• The pH should be neutral or very slightly acidic. stripping deaeration system, using a packed column, carbon
• It should be carbon filtered to ensure it is halide filter and trap filter prior to the column, UV steriliser, post
free. column trap filter and CO2 injection point, with a
• It must have a very low dissolved oxygen level – recirculation loop to ensure the product running forward to
typically less than 50 ppb. storage is always below the maximum permitted oxygen
• It must be at a suitable temperature for blending (instrument not shown).
and flushing, typically 2 – 4 deg C, which also has the
benefit of restricting growth of any contaminating
micro-organisms.

Learning Material 2016 211

 Product water
Water used for brewing & processing, including dilution,
normally treated to some degree. All water which is added
to the wort or beer must be product water.
• Deaerated water –used for diluting high gravity
brewed beer, or where it will come into contact with
beer, or other materials such as filter aids which will
come into contact with beer.
Most cask beers are not brewed at high gravity.
However, where they are, the beer is normally
diluted on transfer to cask racking tank.
Bright packaged beer is normally diluted after
filtration on transfer to BBT, though less commonly
may be added prior to filtration or after the bright
beer tank on transfer to the packaging line.
• Mixing water – used for mixing up, for example filter
aids, caramel, enzymes, hop extracts which are then
dosed into beer post fermentation, thus requiring
Membrane gaseous exchange very low oxygen levels. Additional deaeration is
Very low residual oxygen values can be achieved with low normally required in mixing tanks, achieved by
energy and purge gas consumption (CO2 or N2). bubbling carbon dioxide or nitrogen through the
mixture.
The water flows along the outside of the pack of hollow • Flush water – used to purge lines or process plant
fibres made of hydrophobic polypropylene. Purge gas (CO2 such as centrifuges, filters or yeast presses clear of
or N2) flows at low pressure through the inside of the highly oxygenated CIP final rinse water, or to flush
hollow fibre and is sucked out by a vacuum pump. Due to out the beer on completion of a transfer, prior to a
this, the partial pressure of the oxygen inside the hollow quality change or CIP.
fibre is reduced almost to zero. The partial pressure
difference between both sides forces the oxygen to flow Process water
through the membrane from the water into the gas. Process water is that water used for:
• Cleaning brewery plant.
The membrane material can allow only gases to pass • Washing beer packages before filling.
through. Thousands of hollow fibres are bound together to • Heating, for example in tunnel pasteurisers.
form a bundle in a tube. The high surface area compared to
the small volume is the main reason for the high efficiency Service water
and low running costs. The number of bundles of hollow Service water is generally softened water (typically with
fibres (and thus the surface area) is determined by the reduced temporary hardness to prevent scale formation,
required residual oxygen values and the throughput but may also be completely demineralized). It is used for:-
required. • Boilers for raising steam and hot water for general
use (i.e. not brewing water). The water may be
Chemical methods softened or completely demineralized for boiler feed
Chemical can be added to boiler water to reduce the water. Even if fully demineralized, boiler feed water
oxygen level and thus the corrosion during steam will be chemically treated to prevent corrosion,
generation and distribution. sludge build up etc.
• Cooling towers as part of the refrigeration plant.
Corrosive components, especially oxygen and CO2 have to
be removed, usually by use of a deaeration chemical such
as hydrazine. Remnants can be removed chemically, by use Hot water systems
of an oxygen scavenger such as hydrazine. Feed water also Hot water systems also present a potential source of
has to be treated to attain a pH of 9 or higher, to reduce legionella especially where aerosols are formed (e.g. by
oxidation and to support the forming of a stable layer of showerheads). Cold water systems also present a risk,
magnetite on the water-side surface of the boiler, though lower. To minimise the risk, sites ensure:
protecting the material underneath from further corrosion. • Suitable sized storage tanks are used.
• Water is stored at the appropriate temperatures.
• Ensure regular use.
18.2 Water types and uses • Regular flushing of low use outlets.

Differentiation and uses of different waters General cleaning water

Brewing requires a plentiful supply of good clean water. This is water that is used for hosing down, e.g. floors, and
general hygiene and the normal standard supply can be
The main categories of use are:- used. This is normally mains or water that remains

212 General Certificate in Brewing

untreated other than being sterilised, normally with chlorine. quality requirements for the different types of water at
points of use.
Cooling tower water
Water used in cooling towers is prone to the growth of Product water
bacteria of which the most important is Legionella. Cooling
Task Type of water Treatment
tower water is an ideal environment for growth as it is at a
suitable temperature for growth, and usually contains Mashing - water Product water with the Addition of
suitable nutrients, oxygen and of course water. The very is mixed with the correct salts needed to calcium salts,
grist (ground malt ensure the optimum particularly
action of the cooling tower generates an aerosol during the
and dry adjuncts) conditions for effective calcium sulphate.
process, which allows a single cooling tower to affect a wide
at mashing. enzyme activity Calcium chloride
and diverse population. particularly pH control. or sodium
In many countries there are regulations for managing the risks chloride can be
added to the
from legionella. These regulations generally include:
water tanks or
• The identification and assessment of sources of risk;
into the mash.
• The preparation and management of a scheme to Lactic acid
prevent or control the risk; preparations are
• The keeping of records to check that what has been also widely used
done is effective. to correct pH

Cooling towers and similar systems are often treated using Sparging - water Product water – should be Adjusted for pH
biocides but other treatments are available such as UV used to wash the neutral or slightly acidic and mineral
irradiation, copper / silver ionisation and ozone. extract from the with low dissolved mineral composition,
malt husk. salts. often by addition
In hot and cold water systems legionella has traditionally of calcium salts if
o
been controlled by storing water above 60 C and distributing required.
o o
it above 50 C - and cold water below 20 C if possible. Other
methods which are used include copper / silver ionisation and Breakdown or Product water – free of Often use same
chlorine dioxide treatment. dilution water taints and micro- water as used for
used to dilute the organisms. sparging. Hot
Legionella wort to collection water is cooled
Legionnaire’s disease is a potentially fatal pneumonia caused gravity (strength.) through the wort
by legionella bacteria. The infection is caused by breathing in chillers, or cold
small droplets of water contaminated by the bacteria. Only sterile product
droplets of 5 microns or less will pass deeply into the lungs. water may be
th used instead.
This is 1/1000 the size of a raindrop. The disease cannot be
passed directly from one person to another.
Additions or Product water – free of Often use
Legionella bacteria are common in natural water courses such makeup water taints and micro- demineralized
as rivers and ponds. Since legionella are widespread in the used in organisms. and deaerated
environment, they may contaminate and grow in other water fermentation, water.
systems such as cooling towers, evaporative condensers and maturation and Post fermentation
filtration for additions must be free of See water
hot and cold water services. They survive low temperatures
o mixing process any dissolved oxygen. sterilisation & de-
and thrive at the optimum temperatures between 30 C –
o aids like finings. aeration.
40 C when the conditions are right, e.g. if a supply of
nutrients is present such as rust, sludge, scale, algae and Dilution of high Product water – free of Often use
other bacteria. Over 40 °C, the multiplication will cease, but gravity beer - taints and micro- demineralized
bacteria are not killed. Legionella is not viable at water used to organisms and any water for
temperatures higher than 65 °C, and will be killed. adjust alcohol dissolved oxygen. preparation of
content in high deaerated water.
Areas of risk of encouraging growth and risk of spreading
gravity beers –
legionella include
normally after See water
• Water systems incorporating cooling towers, filtration. sterilisation & de-
evaporative condensers and pasteurisers. aeration.
• Hot and cold water systems.
• Other plant and systems containing water which is Water jetting in Product water – free of See water
o
likely to exceed 20 C, and may release aerosols during bottling - water is taints and micro- sterilisation & de-
operation or maintenance. used to jet into organisms and any aeration.
bottles to dissolved oxygen
Points of use, and quality of water at usage points promote a CO2
The following tables show further details of the water purge. Often hot water (circa
80oC +) is used

Learning Material 2016 213

Process water Services water

Task Type of water Treatment Task Type of water Treatment

CIP and Softened or fully Removal of carbonates & Boiler Water. Uses softened or Removal of
manual demineralized process bicarbonates during fully demineralized carbonates &
water to reduce the bicarbonates during
cleaning of water is used to reduce softening process, or full
softening process,
plant. the formation of scale in demineralization. formation of scale
or full
CIP delivery systems and and form deposits demineralization.
spray heads which is which can corrode
To prevent
caused by the presence of heating surfaces.
corrosion, additives
carbonates in the water. are used to
scavenge dissolved
Carbonates & oxygen the water
bicarbonates affect the pH is adjusted.
efficiency of caustic based Cooling tower Risk of bacterial To reduce risk:
detergents. water contamination by generally
Legionella bacteria
which cause • Risk assessment
Returnable Softened or fully Removal of carbonates & • Management of
Legionnaires disease,
bottle, cask & demineralized process bicarbonates during risk
a potentially fatal
keg washing. water is used to reduce softening process, or full pneumonia type • Records of
the formation of scale in demineralization. disease following treatment
CIP delivery systems and breathing in small • Regular
spray heads. Temporary droplets of operation to
contaminated water. prevent build up
hardness can cause
• Water
‘bloom’ in washed temperature
returnable bottles. control
• Filtration of
Carbonates & water and / or
bicarbonates affect the • Treat water with
efficiency of caustic based biocide
detergents.
E.g. UV, bromine or
chlorine, chlorine
Final rinses of Softened or fully Removal of carbonates & dioxide, silver
plant and demineralized process bicarbonates during ionisation, ozone.
packages water is used to reduce softening process, or full
after the formation of scale. demineralization. The General cleaning This is water that is Normal hygiene
cleaning. water must be sterile to water used for hosing standards apply.
reduce the risk of re- down.
Non infection by micro-
returnable organisms contained in
bottle and unsterile rinse water. 18.3 Sources of effluent and its
can rinsing measurement
Tunnel Softened or fully Removal of carbonates &
Pasteurisers. demineralized process bicarbonates during The nature and characteristics of brewery effluents
water is used to reduce softening process, or full
the formation of scale. demineralization. Effluent is any liquid containing dissolved solids, suspended
solids, brewing materials, beer, yeast, lubricants,
Anti fungicides used to detergents, refrigerant or other chemicals that does not
prevent mould formation. leave the brewery as product and which will, with or
without treatment, eventually enter a water course. Clean
Rust inhibitors used to
water or even good quality beer accidentally discharged to
help prevent rust on
a foul drain becomes effluent.
bottle crowns.
It is expensive to process and the brewery is charged for
this processing. The local water authority will normally also
impose limits to the volume of and content (including
temperature, suspended solids, pH, COD, BOD) of the
effluent that the brewery is allowed to discharge.

Note that there are a number of materials that it is

prohibited to discharge to an effluent system. Special
arrangements must be made for disposal of these
materials. However, these materials are not common in
brewery operations.

214 General Certificate in Brewing

This section will not discuss a number of brewery and Fermentation, yeast room and maturation (cold storage)
packaging waste products such as packaging materials or During fermentation, the amount of yeast in the beer can
oils from engineering, but will be limited to product that is multiply four fold or more resulting in a surplus. Without
discharged to the drains, as indicated above. effective processing, there is the potential for this surplus,
including entrained beer, to be washed down the drain.
Sources in brewing and packaging operations Yeast has a very high COD and suspended solids (SS). The
beer portion has a very high COD & BOD.
Examples of effluent from different parts of a brewery.
Purges from maturation or cold storage tanks contain yeast
and protein, both of which have high solids and COD levels.
CO2 In older breweries, water is used to cool fermentations via
Warehouse
attemperating coils / jackets, rather than recirculating
refrigerant such as glycol. This water is often run directly to
Boilerhouse Packaging Hall drain.
CO2
Fermentation, yeast room and maturation plant becomes
Bottle and Keg
rinses soiled and must be cleaned regularly. Large quantities of
water are used and the effluent from this cleaning
Brewhouse
operation can be high in solids and have a high or low pH
depending on the detergents and sterilants used.
Fermentation Filtration

Spent grain drainings Waste yeast &

and trub Vessel rinses
Waste Filter Aid Filter room
In kieselguhr filtration, beer is dosed with filter aid on its
way to the filter, the filter aid being added to trap yeast and
other small particles so that they do not pass through into
Most of the waste water from a brewery is biodegradable,
the final package beer. When the filter needs cleaning this
although there may be a problem with some CIP wastes.
filter aid is washed off. Effluent from the filter room will
have very high solids content and COD from the entrained
Brewhouse
yeast and protein particles, and if not flushed out
Spent grain is the husk that remains from the malted barley
effectively, will also have a very high COD due to the
used to produce beer. This grain (grist) has been sparged
entrained beer.
with hot water to extract the maximum amount of sugar
from the malt. After sparging, the grain is still very wet. The Filter runs are started and completed by pre and post filter
grain is sold as cattle food as a co-product but the final flushes with water. Often, large quantities of interface,
drainings from the spent grain are high in solids and with high COD levels are run to drain.
Chemical Oxygen Demand (COD), and are normally run to
drain. Modern mash filters and lauter tuns minimise the Packaging Effluent
amount of liquid not recovered for use in the next brew. Effluent from the packaging plant comes from returnable
bottle, cask and keg washing machines, from filling
Trub is formed when the wort is boiled and subsequently machines and from pasteurisers.
cooled. Effluent can be produced if this is washed away to
drain. Trub contains a large proportion of solids and has Returnable package washing is main source of effluent.
very high levels of COD. For this reason, trub is often Detergents are used and the packages have to be rinsed
returned to and disposed of with the spent grains. Trub with fresh water before being filled. Returnable bottle
also contains considerable amounts of retained wort, and washing machines are required to remove paper labels
for this reason, it is often added back to the lauter tun / which could be washed to drain. The packages themselves
mash filter prior to recovery of the final drain down, so usually contain small quantities of beer residues.
reducing the amount of COD / BOD sent to effluent. For an
explanation of COD, see later in this section. Bottles and cans are rinsed prior to pasteurisation and must
be rinsed off before their transfer to the pasteuriser to
Large volumes of water are used to cool the hot wort, prevent corrosion of the pasteuriser by the acid beer, or as
usually in plate heat exchangers. The water is normally a result of bacterial growth. This rinse water often contains
recovered as hot water but an excess can be sent to the comparatively large proportions of beer.
effluent system.
Tunnel pasteurisers invariably use large volumes of water,
Brewhouse plant becomes heavily soiled and must be and in spite of recycling within the pasteuriser considerable
cleaned regularly. A lot of water is used and the effluent quantities may be run to drain. This may be greatly
from this cleaning operation can be high in solids and reduced by water recovery systems which use refrigerant to
normally has a very high pH because of the use of caustic remove the excess heat, along with use of biocides to
detergents. prevent microbial growth.

Learning Material 2016 215

The components of effluent quality
Trub
Effluent Costs
The authorities operating the effluent plants often have Lauter Tun
particular problems to resolve and their charging policies
reflect these. Effluent is typically measured in five ways -
Volume, Suspended Solids, COD, pH and temperature. The
charge for discharging effluent generally takes these values Pasteuriser
Filler
and uses them in a formula e.g. the UK’s Mogden formula to Fermentation
Bottle Washer
calculate the cost per unit of effluent. Individual authorities
may adjust the formula itself to reflect their own problems.

An example of the as used Mogden Formula is as follows Filtration

P = C + V + (St / Ss)S + (Ot /Os)O

Chemical oxygen demand
where Value Explanation Source
• P = cost (pence) per m3 C.O.D. COD was developed as a rapid test Organic material
• C = conveyance charge, p per m3 for the extent of organic assimilable like spent grain,
• V = volumetric charge, p per m3 material in industrial or trade trub and yeast.
• S = suspended solids charge, p per m3 wastewaters. It does not depend on
• O = COD charge, p per m3 the growth of microorganisms and
• St = suspended solids content of trade waste, mg/l there are not the same concerns that
• Ss = suspended solids content of sewage, mg/l there may be toxic material present
• Ot = COD of trade waste, mg/l that would inhibit microbe growth
• Os = COD of sewage, mg/l and therefore lead to a depression of
BOD values. A sample of the waste
Volume stream is oxidized with a mixture of
Value Explanation Source sulphuric acid and potassium
Volume The volume of effluent Wastage of water permanganate and the extent of
discharged, usually described above. reduction in the permanganate
measured in cubic assessed. The test takes about two
metres. hours.

Filtration

Fermentation Trub Lauter Tun

Bottle washer
Brewhouse
Pasteuriser
Filler
Pasteuriser
Bottle Washer
Filtration
Fillers Fermentation

Suspended solids
Value Explanation Source
Suspended This represents that material not Spent grain,
Solids settling in 30 minutes of standing. trub, yeast,
The solids are recovered by filter aid
filtration through paper, which is and bottle
then dried and weighed. The labels.
suspended solids can smother
aquatic organisms and, of course,
increases the sludge quotient in
the treatment works. It is
expressed in ppm (parts per
million) or mg/litre.

216 General Certificate in Brewing

Biological oxygen demand Total organic carbon
Value Explanation Source Value Explanation Source
B.O.D. BOD is a measure of the Organic material TOC TOC has been recognized All organic
impact of a waste like spent grain, for more than thirty years material
stream on a river based trub and yeast. as an analytical technique such as
on its content of to measure water quality. It spent
nutrients that will is determined as the carbon grains, trub,
support the growth of dioxide released by yeast, beer.
micro-organisms, chemical oxidation of the
thereby removing organic carbon in a sample.
oxygen from the water After the sample has been
and contributing to its acidified and purged of
stagnancy. The test inorganic carbon, the strong
measures how much oxidiser sodium persulphate
oxygen is consumed is added and, at 100ºC, the
over a five day period. carbon is converted to CO2
The test has been which is measured in an
around since 1908, it infra-red analyser.
having been established
through the work of the
Royal Commission on Statutory Controls
Sewage Disposal.
Water Authorities generally impose limits to the amount of
pH and condition of effluent being discharged from a brewery
Value Explanation Source into their systems. They can levy penalties and fines to
pH A measure of the Detergents, companies who persistently exceed the limits.
acidity/alkalinity of the sterilants and beer.
A typical set of limits is detailed in the table below:
effluent. Water is
neutral at 7.
Parameter Limit
Maximum volume 100,000 litres per 24
Temperature
Value Explanation Source hours
Temperature. A measure of the heat Hot effluent from
Maximum suspended solids 500 mg/litre
in the effluent. the brewhouse,
boilerhouse, hot CIP Maximum COD 10,000 kg per 24
units or hours
pasteurisers.
pH range 6 – 10
In addition to the above measurements, the following may o
Maximum temperature 40 C
be measured and used in a modified version of the formula.

Notes:
Write down the sources of your own brewery’s water Describe the treatment used for your brewery’s boiler
supply. water and cooling tower water.
Write down the principal characteristics of your own Describe how the de-aerated water plant operates in
brewery’s water supply and how it meets the standards your brewery. Use flow diagrams to illustrate your
required. description.
Investigate the uses for product water in your brewery Write down the sterilisation procedures of your own
and the reasons for the chosen treatments. brewery’s water supply. Illustrate with flow diagrams.
Write down the primary treatment procedures of your Describe an area in your brewery where effluent is a
own brewery’s water supply. Illustrate with flow problem.
diagrams. Identify the charges for your own brewery and how they
Describe the problems experienced with your brewery’s are calculated.
process water and how these are overcome. Identify below the limits set for your brewery.

Learning Material 2016 217

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

218 General Certificate in Brewing

Section 19 Utilities - Process Gases

19.1 Properties, applications and safety of

gases

The essential properties & quality of air and oxygen system with associated sterilisation / CIP capability.

Compressed air and oxygen are used for a number of The essential properties & quality of CO2 and nitrogen
different purposes. The specific requirements for each
purpose vary slightly, and are thus listed separately below CO2 and nitrogen are both used in situations where they
Air or oxygen used for aerating wort or yeast cultures, and will either be in contact with product (e.g. tank top pressure
for CO2 degassing towers for water must be:- gas) or are injected directly into the product.

• Clean, i.e. free of particulate matter. They must both therefore be:-

• Sterile, to prevent infection by non-culture yeasts • Clean, i.e. free of particulate matter.
or bacteria present in the gas.
• Sterile, to prevent infection by non-culture yeasts
• Free of other contaminating gases which would or bacteria present in the gas.
have an adverse effect on the product.
• Free of other contaminating gases which would
• Oil / grease free, to prevent loss of head retention. have an adverse effect on the product.

• Normally dry to prevent bacterial / yeast / mould • Oil / grease free, to prevent loss of head retention.
growth on filters, or blockages of filter by moisture
• Normally dry to prevent bacterial / yeast / mould
(though of course this is not a requirement for
growth on filters, or blockages of filter by moisture
water degassing towers).
(though of course this is not a requirement for
Air used for pneumatic operation of plant, such as valves, water degassing towers).
and use in instruments such as pressure sensors must be:-
• Oxygen free to minimise flavour and haze changes
• Clean and dry, to minimise the risk of corrosion. in the beer.

• Oil free, to minimise risk of contamination of Again, the gas is normally sterile filtered just before the
product in the event of a passing seal, though point of use, using a similar design system as used for air or
sometimes, the air will be deliberately “oiled” for oxygen as shown in the notes GCB section 4.
lubrication purposes (e.g. cylinders for pneumatic
hoists). Note that CO2 reacts with sodium hydroxide to form sodium
carbonate and bicarbonate. Therefore vessels containing
Compressed air used for CO2 should ideally only be cleaned using acid detergents
and sterilants to prevent severe degradation of the caustic
• spent grains transfer for feedstuffs should be clean and possible creation of a vacuum. Tanks containing
and oil free. nitrogen may be safely cleaned with caustic or acid as the
gas does not react with either.
• air knives on small pack tunnel pasteurisers to
remove excess water and foaming units for The practice and benefits of CO2 collection
environmental cleaning need simply be clean
enough not to cause blockages. As it does not There are two sources of CO2 suitable for recovery in
come into contact with product, it does not need breweries:
to be dry, oil free or sterile.
• The CO2 evolved during fermentation
Where gases are to be sterilised, the normal method is • The CO2 being displaced from vessels or beer
filtration through very fine filters. The filters and the containers during filling
pipework from the filter through to the injection point must o
One hectolitre of 44 SG (12 P) wort will produce about 4.2
also be sterilisable. The filter must be capable of being kg of CO2. Allowing for initial losses, mainly due to air
sterilised using clean “wet” steam. The connecting contamination in the initial stages of fermentation, other
pipework is normally sterilised by the steam or the CIP run losses in the collection system and residual dissolved CO2,
through the production plant. See GCB section 4 (wort the likely amount collected assuming > 99.5% pure, will be
cooling and oxygenation) for an example of a gas injection 50 – 60% of this figure – 2.2 to 2.5 kg / hl.

Learning Material 2016 219

Thus large volumes of high gravity wort are going to make • Water scrubber, to remove residual foam and
recovery more economically viable than small volumes of more particularly, the water soluble volatiles
wort and/or low gravity wort. The economics of recovery which would otherwise taint the product when re-
also depends to a large extent on the local cost of used.
purchased gas. In some instances, the brewery may collect
gas surplus to its needs, and the sale of CO2 to a third party • Compressor – to compress the gas, typically to 18
can help offset the capital and revenue costs. The design of bar.
the brewery can also play a large part in the cost -
considerable expenditure may be required to install a • Cooler – to remove the heat generated during the
suitable large scale hygienic collection network. compression of the gas.

• Dryer – to remove moisture, typically to achieve a

Carbon dioxide, especially that collected from FVs, must be o
dewpoint of - 40 C.
checked for purity, cleaned and dried as necessary. Only
pure CO2 must be re-used. A typical collection plant
• Deodoriser – to remove residual volatiles.
consists of:
• Liquefier – typically a shell and tube heat
• Collection mains from the source (vessels) leading exchanger. The carbon dioxide liquefies at circa -
to o
20 C.

• A fob trap, to eliminate any foam or excess • Storage tank – insulated, and fitted with a
moisture vented into the system by a vigorous refrigeration coil to maintain the temperature at
o
fermentation, then to circa - 20 C and 20 bar.

• Balloon storage to provide a low pressure buffer, • Vaporiser. The gas is then normally stored in liquid
to collect any surges in load, and provide a form and subsequently evaporated, using a steam
constant pressure supply to the compressors. or sometimes electric vaporiser to produce gas at a
Note this can be a major bug trap. suitable pressure for distribution. It is essential no
liquid gas passes into the distribution system.

220 General Certificate in Brewing

The significance of inertness • Air curtains on small pack pasteurisers or building
entrances
CO2 and nitrogen are both used in situations where they • Cleaning, either simply as air lines, or incorporation
will either be in contact with product or are injected into chemical foaming units.
directly into the product. They need to be oxygen free
because the oxygen will react with haze forming materials CO2 and nitrogen are both used in situations where they
in the beer, leading to flavour changes and decreases in will either be in contact with product or are injected
solubility of haze forming materials. These flavour changes, directly into the product including:-
hazes, and in extreme cases, sediment will cause a
reduction in the shelf life of the product. • Tank top pressure gas to eliminate contact with
oxygen from air.
Where CO2 and nitrogen are injected into the beer, to be
fully dissolved, this is particularly critical. However, • Filler counter pressuring to minimise oxygen
experience shows that even small amounts of residual gas pickup during filling.
in a vertical bright beer tank counter pressure gas for
example can increase the dissolved oxygen from an in • Package flushing to minimise oxygen pickup during
specification 75 ppb to an out of specification 200 ppb. filling.

Thorough gas purging of tanks after they have been opened • Undercover gassing of canned beer immediately
for inspection is critical for this reason, some breweries prior to seaming.
making a point of flood filling the tank with water, then
• Deaeration of water for use prior to and after beer
emptying with CO2 or N2 top pressure, before cleaning and
transfers such as through mains and filters.
refilling with beer.
• Deaeration of filter aid slurries of other additions
The complete lack of oxygen also makes CO2 and nitrogen
to beer after fermentation.
extremely dangerous to use in confined spaces.
The typical uses of process gases • Outside the brewery itself, it may be used to flood
fill hop storage bags to reduce the oxidation of the
Pure oxygen is used for:- hop oils and resins.

• Wort oxygenation to allow healthy yeast growth CO2 is also used for:-
and subsequently, fermentations and excess yeast
suitable for re-pitching. • Direct injection in order to give beer its fizzy
character.
• Yeast culture oxygenation – for reasons as above.
• Purging water in a deaeration column to produce
The oxygen requirement of some yeasts can be met by
de-oxygenated water for flushing and dilution,
dissolving air, which can provide up to about 10 ppm
with the added benefit (compared to other means
dissolved oxygen. However, others require more than this,
of deaeration) when used for dilution that the
which can only be met by pure oxygen, which can provide
carbonation plant does not have to add as much
up to approximately 30 ppm. Excessive foaming due to the
CO2.
presence of approximately 4/5 nitrogen by volume in air
may also drive the use of oxygen instead. • Degassing beer by bubbling CO2 through beer with
reduced top pressure, to wash out excess CO2, or
Air may be used for:-
to remove dissolved oxygen. This process is not
• Wort and yeast culture oxygenation – as above. widely used as it is not easily controlled; it
adversely affects head retention by using up the
• Spent grains discharge from mash / lauter tun or supply of head forming proteins, and may cause
mash filter dump tanks to silos. haze or even gushing due to the collapsed foam.

• CO2 stripping in water degassing tower (for CO2 • Some breweries have used it to correct high pH
removal). effluent, the CO2 reacting with alkaline materials,
especially NaOH to form the carbonate or
• Operation of pneumatic actuators such as valves. bicarbonate form, which both have considerably
lower pH. This helps bring the pH of the effluent
• Operation of pneumatic cylinders such as pallet into the permissible range. CO2 used for this
hoists. purpose does not have to be particularly pure
• Instruments such as pressure sensors. (unless it had to be liquefied for storage).

• Air knives on small pack tunnel pasteurisers to • It is used for beer dispense, either on its own, or
remove excess water. mixed with nitrogen for improved head formation
and retention.

Learning Material 2016 221

Nitrogen is also used for:- Some key aspects include the following:-

• Direct injection in order to enhance the foam • Keep cylinder stocks to the minimum necessary.
retention of the beer to achieve for example, 10
ppm for conventional keg lagers and ales, up to • Only use cylinders filled by a reputable gas supplier
approximately 50 ppm for stouts or nitro-keg who fills and regularly tests cylinders in accordance
beers. with current safety regulations.
• Liquid nitrogen may also be used in canned
• Return gas cylinders to the supplier you purchased
products instead of widgets to help create a dense
them from – and to no-one else.
long lasting head.

• Degassing beer by bubbling N2 through beer with • Cylinders should be handled with care and not
reduced top pressure, to wash out excess CO2 or knocked violently or allowed to fall. They should
dissolved oxygen. This process is not widely used be stored and secured in an upright position.
as it is not easily controllable; it adversely affects
• Always store full cylinders in an area away from
head retention by using up the supply of head
cylinders in use.
forming proteins, and may cause haze or even
gushing due to the collapsed foam. • When in use cylinders should be firmly secured to
a suitable cylinder support.
The economic importance of leak prevention
The purchase of, collection and storage of, or the • Never drop, throw or mishandle cylinders.
production on site of these gases is expensive.
Considerable energy is required to compress and cool the • Never use cylinders for anything other than storing
gases for storage, normally as a liquid, and subsequently to and delivering the gas for which the cylinder is
consistently evaporate the liquid to usable gas. Other specified.
materials and operations required to ensure efficient
• Never store cylinders where they may come into
operation may include maintenance, water, CIP.
contact with water.
Gas leaks result not only in loss of the gas, generally at high
pressure, and thus all the electrical, thermal energy etc. • Never store next to a direct heat source; e.g.
required to produce the gas at that point. High losses may radiators, coolers etc.
result in failure of other plant to operate less efficiently.
• Medical gases must only be used for medicinal
Where an inert gas such as CO2 or nitrogen is lost, there
purposes.
may be safety risks associated with increased levels in the
atmosphere due to reduced oxygen levels. Where pure
oxygen is lost, there may be an increase fire risk in that
Safety hazards of gases and high pressure distribution
area.
Gas leaks may also damage plant if not maintained Carbon dioxide
promptly, either from failure to operate correctly, or from Carbon dioxide is present in the atmosphere at
simple wear of, for example the flange surfaces from where concentration of 0.04% and is a normal body constituent
the gas is leaking. arising from respiration. It is toxic in high concentrations
acting directly on the respiratory centres in the brain.
Safe handling & storage of gas cylinders In liquid form, there is a risk of frost burns due to the
Dispense gas cylinders are heavy and are filled with gas held extreme low temperature.
under high pressure. If a cylinder discharges or ruptures
A major gas leak may be reportable to the HSE as a
(perhaps through mishandling), the damage is likely to be
dangerous occurrence under RIDDOR regulations. (UK –
considerable because a cylinder can become a missile-like
equivalent regulations may apply elsewhere).
projectile or fracture catastrophically.
Carbon dioxide is a special safety hazard in fermenting
Cylinders must be handled and stored in accordance with
rooms. There are several features of this gas to be
the UK Manual Handling Regulations 1992 (or similar in
considered:
other countries) and other health and safety guidelines.
• It is a toxic gas at high concentrations in the
There are well recognised procedures to minimise risks atmosphere – see table later.
covering: • It is heavier than air and it will accumulate in low-
• Labelling lying areas.
• Handling • It is generated in very large quantities during
• Storage fermentation.
• Transporting
• Use of personal protective equipment
222 General Certificate in Brewing
The risks associated with CO2 can be reduced by: CO2 reacts with sodium hydroxide to form sodium
carbonate and bicarbonate. Therefore vessels containing
• Effective removal of the gas from FV rooms using CO2 should ideally only be cleaned using acid detergents
extraction systems. and sterilants to prevent severe degradation of the caustic
and possible creation of a vacuum. Tanks containing
• CO2 collection from fermentations. nitrogen may be safely cleaned with caustic or acid as the
gas does not react with either.
• The installation of gas detectors with associated
alarm handling. Occupational exposure limits
The exposure limits for carbon dioxide published by the UK
• Safe systems of work, including permits to work,
Health & Safety Executive are:
permits to enter confined spaces and evacuation
procedures.
• 0.5% as a time weighted average over an 8 hour
• Clearly defined evacuation procedures. working day.

The effects of increasing CO2 concentrations are noted in • 1.5% as a time weighted average over a 10
the following table: minute period.

CO2 conc. by Effects and Symptoms Most UK companies apply their own restrictions based on
these values which appear, at first glance to be
volume of air
considerably stricter, but are designed to ensure the
“weighted average” is never exceeded.
1% Slight and unnoticeable increase in
breathing rate – this is the level Typical alarms are set up with 2 level settings as follows:
commonly used to evacuate an area.
• CO2 first level alarm (limited access time)
2% Breathing rate increases (increase to = > 0.5%in air
1.5 times normal rate), and prolonged
exposure over several hours may • CO2 second level (immediate evacuation) alarm
cause headache and feeling of = > 1.0% in air
exhaustion
Nitrogen
3% Breathing becomes deeper (increase Air contains approximately 80 % N2. Nitrogen levels above
to twice normal rate). Hearing ability this are potentially dangerous because it will suffocate and
reduced, headache experienced with it is difficult to detect. In liquid form, there is a risk of frost
increase in blood pressure and pulse burns due to the extreme low temperature. People
rate required to enter tanks where N2 is used for back pressure
are especially at risk. Dangers can be reduced by the
4–5% Breathing becomes deeper and more installation of gas detectors (Oxygen deficiency meters).
rapid (increase to four times normal
rate). Signs of intoxication after Atmospheric sampling of an area where there is a
exposure for half an hour, with slight significant risk that nitrogen could be released / present in
choking feeling. dangerous quantities must be carried out prior to entry.
When testing for the presence of nitrogen it is usual to
5 – 10 % Characteristic pungent odour achieve this by measuring oxygen levels as nitrogen diffuses
noticeable. Breathing very laboured into the atmosphere and will displace oxygen.
leading to physical exhaustion.
Oxygen levels should be between 19.5% and 21.5% prior to
Headache, visual disturbance, ringing entry into confined working spaces.
in the ears and confusion, probably
leading to loss of consciousness within In liquid form, there is a risk of frost burns due to the
minutes. extreme low temperature. One tonne of liquid N2 will
3
generate approximately 840 m of CO2 at atmospheric
10 – 100 % Loss of consciousness more rapid, with pressure.
risk of death from respiratory failure.
Typical alarms are set up with range settings as follows
Hazard to life increases with the
percentage concentration, even if • O2 depletion = < 19 % vol in air
there is no oxygen depletion.
• Excess oxygen = > 23 % vol in air

Learning Material 2016 223

Oxygen Pressurized gas systems
Oxygen supports combustion and in high concentrations All pressurized process gas systems (including compressed
can therefore lead to very intense fires. Therefore high air) present safety hazards. If pressure systems fail, they
levels of oxygen can be considered as dangerous as low can seriously kill or injure people. Most countries have
levels of oxygen, though in the brewing industry, high levels regulations dealing with the risks created by a release of
are not generally considered a common risk. In liquid form, stored energy should the system fail and detailing the
there is a risk of frost burns due to the extreme low measures that should be taken to prevent failures and
temperature. reduce risks. The regulations generally cover:

It is stored in high pressure containers, sometimes as a • Safe operating limits.

liquid, when it must be vaporised before distribution and
use. • Written schemes of examination.

The effects of decreasing O2 concentrations due to • Specific requirements relating to most pressure
increased CO2 or nitrogen concentration are noted in the vessels, all safety devices and any pipework which
following table: is potentially dangerous.

O2 conc. by Effects and Symptoms

volume of air (Normal air contains 20.9% oxygen by Notes:
volume) Candidates should familiarise themselves with their own
21 - 14 % Increasing pulse rate. Tiredness. brewery’s procedures for:
• the safe entry into tanks, cold rooms and other
14 - 11 % Physical movement and intellectual confined spaces where carbon dioxide or excessive
performance becomes difficult. nitrogen may be present
• the use of portable and fixed alarms together with
11 - 8 % Possible headaches, dizziness and other personal protective equipment.
fainting after short period of time.
Candidates should also investigate their own national (and
8–6% Fainting within a few minutes, any local) safety regulations and procedures relating to:
resuscitation possible if carried out • the storage of liquid gases and their distribution in
immediately. high-pressure mains.
• compressed air systems and equipment.
6–0% Fainting almost immediately, death or • the safe handling and storage of compressed gas
severe brain damage. cylinders.

224 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Learning Material © Institute of Brewing and Distilling 2016

Learning Material 2016 225

Section 20 Brewing and the Environment

20.1 Sustainability and climate change

The concept of a sustainable industry

The brewing industry, in common with other industries, Climate change

impacts on the environment in many different ways. For Climate change is being caused / accelerated by an increase
example: in greenhouse gases in the atmosphere. These gases come
from both natural and man-made sources, but the increase
• As a user of energy. is the result of human activity, mainly the release of carbon
dioxide from the use of fossil fuels such as coal, gas, oil,
• As a ‘consumer’ of water and other natural petrol and diesel.
resources.
All businesses and societies, to a greater or lesser extent,
• As a source, both directly and indirectly, of are feeling the impact of climate change and the policies of
atmospheric emissions, trade effluent and packaging governments around the world to address it. These may
waste. include:
Some of the materials consumed can be considered • restrictions on emission levels
“renewable”, such as the barley grown for malting,
although its production actually consumes considerable • restrictions on water use
fossil fuel energy. Others resources such as fossil fuels are
consumed by the process. The malting, brewing, packaging, • changes in agricultural growth patterns
distribution, and consumers generate “waste” contributing
to land fill material and gas emissions which impacts on the • increases in energy prices
environment.
• changes in consumer habits
Sustainable development has been described as:
Sustainability guiding principles
• Development that meets the needs of the present Our industry consumes significant resources. Can true
without compromising the ability of future sustainability be achieved? Probably not, but there is much
generations to meet their own needs. (ref: we can do to improve our use of diminishing resources.
Brundtland Commission, 1987)
Companies committing to minimising the total impact of
• Sustainable development is about ensuring a better their activities on the environment, to using natural
quality of life for everyone, now and for generations resources wisely, to pursuing social progress and to playing
to come. To achieve this, sustainable development is leading roles in their economies adhere to certain guiding
concerned with achieving economic growth, in the principles typified by the following:
form of living standards, while protecting and where
possible enhancing the environment – not just for its • To comply with all relevant national and local
own sake but because a damaged environment will legislation and regulations.
sooner or later hold back economic growth and
• To design, operate and maintain processes and
lower the quality of life – and making sure that those
plants to:
economic and environmental benefits are available
o optimise the use of all resources (materials,
to everyone, not just the privileged few. (ref: UK
water, energy etc.) whilst ensuring that
Department of the Environment, Transport and
unavoidable wastes are recovered, reused or
Regions. 1998)
disposed of in an economically sustainable
and environmentally responsible manner.
The challenge of sustainable development is to achieve
o minimise the potential impact on the
economic, social and environmental objectives at the same
environment from site emissions to air, water
time. In the past, economic activity and growth have often
and land.
resulted in pollution and wasted resources. A damaged
o regularly assess the environmental impacts of
environment impairs quality of life and at worst may
processes and plants and, based on the
threaten long term existence, for example as a result of
assessments, set annual objectives and targets
global climate change.
for the continual improvement of
environmental performance.

226 General Certificate in Brewing

 o use and develop packaging distribution Other organic residues such as spent grains, trub and yeast
systems for which packaging/product also release CO2 when they are microbiologically degraded.
combination will make fewer demands on These activities are of course out of the direct control of the
non-renewable and renewable natural brewer, though he may be able to influence the quantities
resources. of waste, and the way in which they are treated.
o minimise the use of substances which may
cause potential harm to the environment and
ensure they are used and disposed of safely.
o encourage a culture of awareness on
sustainability issues amongst employees
through management commitment,
appropriate communications, training and
other initiatives.
o establish and maintain appropriate
procedures and management systems to
implement these principles through policy
commitment.
o work with suppliers and other business
partners in the supply chain to maintain high
Carbon dioxide derived from the fermentation process is
environmental standards.
increasingly recovered in the brewery for use in the process
The role of carbon dioxide – the carbon cycle and product. The carbon dioxide emitted at the start of
Carbon dioxide emission is seen as a key measure of fermentation is mixed with air, is uneconomic to recover,
environmental damage. During fermentation the yeast and is therefore vented to atmosphere. Carbon dioxide
metabolises the sugars in the wort to produce a recovery becomes viable when the gas reaches a
combination of alcohol and carbon dioxide. The impression predetermined purity level (e.g. 99.5%). Generally, the
may erroneously be given that the brewing industry is a net recovery process involves the following stages:
generator of carbon dioxide as a result. In reality, carbon
dioxide evolution through that route is simply part of the • Collection
natural carbon cycle: • Washing / scrubbing
• Compression
• The amount of carbon dioxide released during • Deodorising and drying
fermentation is roughly a quarter of the amount • Liquefaction and storage
absorbed from the atmosphere through
photosynthesis by the growing grain. In addition to reducing emissions to the environment, this
saves the brewery having to purchase all the gas it requires
• Photosynthesis by the growing grain releases oxygen from outside manufacturers thereby reducing demand on
back into the atmosphere. resources and indirect energy use.

Sources of carbon dioxide emissions

The real source of carbon dioxide emissions in the brewing

industry is the combustion of fossil fuels – either at the
brewery itself for steam raising, or for the generation of the
electricity used by the brewery. There is therefore a need
for continuing improvement in the efficiency with which
fossil fuels are used, whether through the use of purchased
electricity or through the combustion of fuel at the
brewery:

• Electricity, as compared with natural gas, gives rise

to three times the quantity of carbon dioxide for the
same amount of delivered energy.
• Whereas electricity provides only perhaps 25% of
the energy requirements of the brewing industry,
the generation of electricity creates almost 50% of
carbon dioxide emissions.
However, note that carbon dioxide is also released back • Where available, natural gas generally provides
into the atmosphere through human metabolism, including perhaps 66% of the total energy requirement but
the alcohol and residual sugars in beer. creates only 40% of carbon dioxide emissions.

Learning Material 2016 227

Fossil fuels are of course used for all vehicular movements on site in boilers using primary fuels such as gas, oil or coal.
of materials to and from the brewery, adding to the total Electricity on the other hand is usually purchased from
CO2 produced during beer production. national grids, even though some breweries generate a
proportion in-house.
Agricultural operations such as planting, harvesting and use
of fertilisers, the transport and drying of barley, and the The approach to achieving savings in the use of energy can
malting process also have an impact on the carbon be categorised under the following headings:
emissions of the total brewing process.
• Process technologies
Other gases
• Horizontal technologies
Other gases including sulphur dioxide, hydrogen sulphide,
oxides of nitrogen, possibly partially burned fuel and • Overall energy management
particulates may also be emitted to the atmosphere if the
control of the burners is inadequate. These emissions are Process technologies
also subject to controls and may require use of scrubbers Process technologies relate to the use and treatment of the
etc. to clean up flue gas prior to discharge. materials themselves, principally malt, water and hops in a
way specific to brewing. Energy savings can be achieved by
the adoption of Best Available Techniques (BAT) which are
20.2 Conservation widely disseminated within the brewing industry. Examples
of processes which require high energy inputs where much
Principal energy consuming activities in a brewery work has been carried out might include:

• Mashing
Within the brewing industry the main energy usage will
• Wort boiling
vary between breweries (large, small, old, modern), with
• Wort cooling
product (beer, lager), with the mix of package type (cask,
• Hot water management
keg, returnable bottle, non-returnable bottle, can) and with
• Fermentation
location (ambient air temperature and water temperature).
• Pasteurisation
The following are some illustrative examples:
Horizontal technologies
Horizontal technologies (with demonstrable Best Available
Thermal Energy %
Techniques) can invariably be applied across many
Brewhouse 20 to 50 industries. Examples include:

• Steam raising
Packaging 25 to 30
• Refrigeration
Utilities 15 to 20 • Compressed air
• Utility pipework distribution systems and insulation
Admin, space heating Up to 10 • Combined heat and power
• Electric motors and drives
• Biomass solutions as alternative energy sources
Electricity consumption %
Overall energy management
Refrigeration 30 to 40 A number of well proven techniques can be employed in
the effort to reduce energy use:
Packaging 15 to 35
(1) Analysis of energy use and implementation of a
Compressed air 10
monitoring and targeting (M & T) system
Brewhouse 5 to 10
This is the fundamental energy management technique that
Boilerhouse 5 must always be implemented first. It ensures that all energy
usage is monitored on a regular basis.
Other 15 to 35
The key is the installation of strategically positioned
effective metering to provide reliable data. Best practice is
Typical energy reduction strategies to develop the energy metering to allow the transfer of
The energy used in brewing where it interfaces with the measured energy costs into the user cost centres with a
processes takes the form of heat (steam and hot water) and comparison of usages against calculated standards, any
power (electricity). The heat energy is normally generated variance being reported.

228 General Certificate in Brewing

The energy data provided by the monitoring and targeting require cooling as “hot” lines and all the streams
system must be disseminated inside the brewery. This is of that require heating as “cold” lines. The point of
prime importance, in conjunction with awareness training, closest approach between the hot and cold
to motivate the staff to save energy and allow them to composite curves is the pinch point (or just pinch)
participate and improve the efficiency of the equipment. with a hot stream pinch temperature and a cold
stream pinch temperature. This is where the design
(2) Targeted investigation and action plan is most constrained.
Here an investigation is initiated to look at an area (or • In the second step of the pinch technology analysis,
areas) of high energy usage or known inefficiency. For a aspects that can be improved are studied from the
generalised approach the highest users of energy would be perspective of energy conservation, operational
targeted first (adopting the Pareto principle). costs and new plant capital cost. Finally the heat
exchange network is improved and optimised.
Examples for high levels of thermal energy usage are
mashing and lautering, wort boiling, CIP and pasteurisation By finding the pinch point and starting the design there,
/ sterilisation. energy targets can be achieved using heat exchangers to
recover heat from the hot to the cold streams in two
Examples for electricity are refrigeration, compressed air,
separate systems, one for temperatures above pinch
pumps and conveyor systems.
temperatures and one for temperatures below pinch
Examples for effluent are trub, tank bottoms, returnable temperatures.
packaging container cleaning, detergents & sterilants used
The concept is designed applicable for both new breweries
in CIP.
or for retrofit situations. In its widest application it can take
The key stages in the investigation process are: account of all the energy flows on a site and identify
projects that look attractive on their own or inappropriate
• Audit the process when considered in a wider context.
• Produce findings
(4) Feasibility studies into alternative technologies
• Evaluate findings
• Produce action plan In addition to the energy saving techniques described
• Make modification / investment above, it may be appropriate from time to time to carry out
• Re-evaluate process performance feasibility studies into alternative technologies which may
• Assess energy saving and financial implications lead to strategic capital investment. Examples of such
technologies might be:
This technique can be developed into one of continuous
improvement: • Combined heat and power
• Wind power
• Evaluate against standard / benchmark • Photovoltaic cells for electrical generation
• Assess options • Solar panels for thermal energy
• Make change • Generation of methane from biomass (anaerobic
• Re-evaluate digesters)
• Monitor improvement • Burning of biomass, including spent grains to
• Etc. produce heat and power (steam and / or
electricity).
(3) Pinch analysis and pinch technology

Introduced in the mid-1980s, pinch analysis is a Specific examples

methodology for minimizing energy consumption of
Specific examples of methods of reducing energy
industrial processes by calculating thermodynamically
consumption include:-
feasible energy targets (or minimum energy consumption)
• Movement sensors to control lighting
and achieving them by optimizing heat recovery systems,
• High efficiency motors
energy supply methods and process operating conditions.
• Variable speed drives to optimise pump outputs and
Pinch technology proceeds in two steps: reduce starting loads
• Good design of process pipework and pumps to
• In the first step, the process data is represented minimise pressures and excess flow rates
graphically as a set of energy flows in the process, as • Automatic shutdown / restart for computer systems
a function of heat load against temperature to • Building insulation
determine the minimum energy consumption a • Maximising refrigerant temperatures
process should use to meet its specific production • Wort kettle vapour heat recovery
requirements. Composite curves are created • Condensate recovery
considering all the streams within the process that • Light weight bottles and cans.

Learning Material 2016 229

Principal water consuming activities An example of a well proven staged approach to improve
water management is detailed below:
See section 18.2 for more detail. There are three distinct
purposes: • Produce mass balance
o Start with survey of water use across brewery
• Product (brewing) water (liquor) - for the production o Include all water use – product, process, and
of the beer itself services
• Process water - for cleaning brewery plant, washing o Aim to account for > 80% of water use
beer packages before filling, cooling and heating
• Construct simple model
• Service water - for boilers, utility cooling towers,
o Build simple network model based on
general cleaning water
information known (flows, concentrations) to
Typical water conservation strategies identify areas of inaccuracy
o Resample critical nodes to improve
Access to a sustainable water supply is critical to the accountability to 90 to 95%
brewery as one of the key raw materials. Quality and
availability are of major significance. It could, perhaps a • Reduce Waste
little cynically, be said that breweries “borrow” water from
the environment: Focus on poor housekeeping to reduce wastage
o routine inspection for leaks
• treat it as needed o prevention of losses from taps, triggers by fitting
• use it once (mostly) flow restrictors
• treat it again o or shut-off valves
• throw it away
• Improve Management
o Examine CIP programmes to ensure the water is
This can be represented as the “Water Supply Chain”
being used effectively
o Examine operations of keg washers, bottle
washers and all small pack pasteurisers to
prevent unnecessary wastage of water
o Examine utilities (cooling systems, water
purification, boiler operation) to check for
inefficient water usage

• Identify Reuse or Recycling Options

o Using network model, identify opportunities for
water reuse and water recycling
o Identify minimum economic water consumption
Surveys of breweries have shown that the ratio of volumes for site
of water consumption to production varies from 3:1 to
20:1. The adjudged minimum ratio of consumption, • Generate Strategic Vision
allowing for unavoidable losses, is approximately 1.4:1. In o Incorporate new plant, expansions, discharge
practice, however, the minimum consumption is regarded consent levels (new plant will be designed for
as being in the range 2.5:1 to 5:1 depending on the minimum economic water use)
operations carried out by the particular brewery. o Identify new minimum economic water
consumption for site
Strategies to conserve water are, not surprisingly, very
similar to those to conserve energy (see Section 20.2). The • Improvement Plan
adoption of Process and Horizontal Technologies o Identify steps to implement water management
incorporating Best Available Techniques (BAT) is essential in strategy and
seeking step-wise reductions in water use. o Prepare economic cases
o Implement water reuse and recycle
As described in the section on energy reduction, similar
improvements
approaches can be adopted:
It is generally accepted that full savings cannot be achieved
• Analysis of water use and implementation of a in one step. There is often merit in starting with the
monitoring and targeting (M & T) system cheapest and most cost effective.
• Targeted investigation and action plan Typical savings may then build up in the following way:
• Feasibility studies into alternative technologies • Reduction in uncontrolled use (housekeeping)
20 to 30%

230 General Certificate in Brewing

 • Improved control (management) 20 to 30%
Process Excessive Automate and
• Water reuse 10 to 20% water flushes/rinses optimise CIP systems
during plant to reduce rinse times
• Water recycling 10 to 20% cleaning. / cycles / improve
interface accuracy.
• Design improvements 10 to 20%
Recover and re-use
water and chemicals
Diagrammatically this staged approach might be (where possible).
represented as shown:
Use several short
rinses rather than
one long rinse.

Unnecessary Optimise pre-rinses.

dumping of Remove CO2 from
detergent. FVs if using caustic
detergent. Use
sacrificial detergent
cycles for heavy soil
removal. Use acid
detergents where
possible to avoid CO2
degradation.
CAPITAL COST
Tunnel pasteuriser Recover, cool and
water. treat with biocides
prior to re-use.

Specific Water Conservation Measures Service Loss of steam Plant maintenance.

water condensate.
Management of water usage can be improved by adopting
good practices, a number of which are detailed below: Leaks.

Water Use Wastage Conservation Over use of hoses Training and

for hygiene cleaning. supervision to ensure
careful use.
Product Excessive drainings Measure and control
water from the the volumes of water
Use of triggers and
mash/lauter tun. used.
restrictors on hoses.
Change from lauter
Use of high pressure,
tun to mash filter.
low volume cleaning
systems where
Recover ‘last
appropriate.
runnings’ and reuse
Water used for All cooling water
Excessive Optimise mash and
cooling. recovered and re-
evaporation from sparge water
used in the most
wort boiling. volumes.
energy efficient way.

Hot water recovery Ensure processes are

system (primarily well designed and
from wort cooling) tightly controlled. 20.3 Waste
out of balance
leading to an excess Principal waste generating activities in a brewery
of hot water going
to drain.
Brewing operations achieve good conversion rates of raw
materials into product. As well as beer products, reasonable
Excessive flushing or Ensure processes are
chasing following well designed and quantities of surplus yeast and spent brewer’s grain are
product transfer. tightly controlled. produced during the process. These are considered “co-
products” rather than waste streams since in the main they
are sold on for animal feeds or, in the case of yeast, often
for human consumption.

Learning Material 2016 231

Most of the solid waste produced by a brewery site is Cans Recycle Skip
generated from packaging materials whilst most of the non-
solid waste primarily arises from the production and Glass Recycle Skip
processing of beer.
Cardboard Recycle Cage / skip /
compacted bundle
Note: Brewery effluent is covered separately in Section 18
and packaging waste is covered in the GCP syllabus in Polythene Recycle Cage / skip /
Section 19. compacted bundle

Effluent Landfill Skip

In general, waste streams comprise: screenings
(biodegradable)
• process wastes specific to brewing and packaging.
Building waste Landfill Skip
(from minor
• residues of raw materials and product removed from civil works)
wastewaters by drainage catch pots and screens.
Wood (non- Recycle Skip
• dust and particulate caught in abatement returnable or
damaged
equipment, for example, bag filters. pallets)

• product wastage. Stainless steel Recycle Skip

(processing
pipework
• boiler plant ash (for coal). modifications
etc.)
Most of the waste produced by breweries can potentially
be recycled into the process, reworked for animal feed, Metal waste Recycle Skip
(e.g.
used in land spreading or is suitable for waste treatment aluminium,
methods such as composting. steel from plant
modifications)
The following table gives a list of the main waste streams
Office paper Recycle Bin
arising at a brewery, where they originate from and how waste
they are disposed of and the usual storage containers used
within a brewery for temporary storage. Spent oil Recycle Bunded tank

Ink Specialist disposal Bin

Description Disposal route Storage container
of waste Fluorescent Specialist disposal Specialist storage
Malt Landfill / animal feed Bag tubes containers
screenings
Spent grains Animal feed / burning Bulk silos (appropriate Special cleaning Specialist disposal Bunded drum / IBC
directly or after to brewery size) chemicals
digestion for methane
production for burning Fibreglass Specialist disposal Covered skip
(insulation)
Trub With spent grains

Yeast Foodstuffs e.g. animal Bulk slurry / pressed

feed, Marmite, medical, cake Issues for waste disposal
e.g. yeast supplements
Waste disposal and duty of care
Yeast Effluent Direct to sewer Where waste disposal is controlled by taxation, levy or
Waste beer or Recycle as soil improver Bunded tank
simply cost, systems to monitor waste are required.
fob specialist effluent Information recorded would normally include:
treatment
• quantity
Processing aid Landfill Bag / skip
bags and fines • nature
(e.g.
kieselguhr) • origin (where relevant)
Spent Recycle as soil improver Bunded tank • destination
processing aid / landfill
slurry (e.g. • mode of transport
kieselguhr)
• treatment method

232 General Certificate in Brewing

Increasingly breweries have service agreements with • Surplus cleaning chemicals (typically strong alkaline
specialist, licensed waste disposal contractors for the or acid products).
provision of comprehensive waste disposal and • Residual chemicals left in portable storage
management services, covering but not limited to: containers (thus prohibiting return of the containers
to the supplier).
• Reducing the amount of waste produced. • Chemicals that have been identified as waste due to
• Making the most efficient use of waste. quality aspects (e.g. contaminated, out of
• Selecting waste disposal options which minimise the specification or simply substances no longer used)
risk of environmental pollution and harm to human • Flammable wastes
health. • Wastes sensitive to heat or light.
• Employing the hierarchy of waste reduction, reuse,
recycle, recover and dispose. In such cases, some or all of the techniques listed below
may be applied to minimise potential environmental
The duty of care responsibility ensures that waste impacts:
management is audited throughout the process including
confirmation of the final location of the waste disposal or • The storage area is covered.
recycling. • The storage area is fully enclosed (to contain
spillage).
The pressure on landfill • There is protection against flood or fire-water
Land fill is increasingly discouraged for a number of key ingress.
reasons: • There is an air extraction system.
• Drainage liquids are contained, treated and tested
• Climate change caused by landfill gas from prior to release.
biodegradable waste. • There is fire protection.
• Loss of resources.
• Constraints on areas suitable for landfill sites. When considering temporary waste storage areas, factors
• Loss of recyclable components of waste landfilled. considered when assessing a storage risk assessment would
normally include:
Many countries have introduced a landfill tax which is a
form of tax that is applied to increase the cost of landfill. • Compatible containers are used for the substances
The tax is typically levied in units of currency per unit of being stored and that these containers are of robust
weight or volume. The reasons for landfill taxes can vary construction to ensure that spills and leaks do not
from country to country. occur
• Adequate warning notices, barrier tape and signage
They may include: are in place forbidding access to the storage area
• Storage areas are not located adjacent to surface
• a means of raising general revenues. water drains and, where possible, these areas are
• to generate funds for solid waste planning and located within bonded or kerbed areas
inspection programmes. • Individual containers are labelled to identify their
• for long-term mitigation of environmental impacts contents and volume
related to disposal. • The period of storage is minimised so that all waste
• a means of inhibiting disposal by raising the cost in containers are removed from the area as soon as
comparison to preferable alternatives (in the same possible
manner as an excise or “sin tax”). • No other wastes are stored in the temporary area
other than those that have been agreed.
Waste storage and segregation
Best practice dictates that, where possible: Strategies to minimize waste and encourage recycling
• wastes are stored as close as possible to the point of Waste recovery or disposal
generation In terms of environmental impact there is increasing
• waste storage areas are clearly marked pressure to improve the utilisation of materials, water,
• skips are specified appropriate for the duty energy and minimise waste. The hierarchy of waste
• skips are stored on hard standing areas reduction applies:
• wastes are segregated wherever possible to
maximise the opportunity to reuse or recycle. • Reuse

From time to time “special” wastes may arise which have • Recycle
particular storage requirements. Typical examples may
include: • Recover

• Dispose

Learning Material 2016 233

Increasingly governments and other regulating authorities • composting
are “encouraging” the recovery of waste unless it is • animal feed
technically or economically impossible to do so. • land spreading where the brewery:
o Can demonstrate that it represents a genuine
In considering options for waste management, many agricultural benefit or ecological improvement.
countries now encourage a process known as “Best o Has identified the pollutants likely to present
Practical Environmental Option (BPEO) Assessment”. As the from a knowledge of the process, materials of
term suggests the assessment is designed to demonstrate construction, corrosive / erosion mechanisms,
that the chosen routes for recovery or disposal represent materials related to maintenance, for both
the best environmental option considering, but not limited normal and abnormal operation, validated as
to, the following: necessary by appropriate analytical techniques.
• All avenues for recycling back into the process or o Has identified the ultimate fate of the
reworked for another process. substances in the soil.

234 General Certificate in Brewing

 Qualifications

The General Certificate in Brewing (GCB)

Examination Syllabus 2016

Learning Material 2016 235

 Syllabus Section 1: Beer types; their raw materials; sweet wort production.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 5)
1.1 Definition of beer and 1. A generic, non-legalistic definition of beer in terms of its typical ingredients
types of beer and methods of production.

2. Characteristics which differentiate lagers, ales and stouts.

1.2 Barley and malt 1. The role of barley as a principal source of starch.

2. The special attributes of barley for malting.

3. The significant changes that occur when the barley grain is malted.

4. The principal constituents of malt.

5. The key malt parameters of degree of modification, extract content, moisture

content, extract, and colour.

6. The selection of malt for beer type and mash conversion method.

7. Pre-acceptance checks at malt intake.

1.3 Adjuncts and coloured 1. Reasons for the use of adjuncts.

malts
2. Types of adjunct and their method of use.

3. Typical usage rate as proportion of the grist.

4. Types of coloured malt and their characteristics.

5. Typical uses of coloured malts.

1.4 Mash conversion 1. The respective roles of the amylases and protease, the effect of temperature,
pH and time on their activity.

2. Temperature and wort viscosity.

3. The influence of the ionic composition (hardness salts) of mashing water in the
mash and on beer flavour.

4. The starch test.

5. Key sweet wort parameters of fermentability. [See also section 10.2]

1.5 Grist composition and 1. The extract yield of raw materials.

extract performance
2. Malt and adjunct quantities required for a grist from theoretical material
extract values.

3. Calculation of brewhouse extract performance.

236 General Certificate in Brewing

 Syllabus section 2: Sweet wort production (methods and plant).

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered =4)
2.1 Brewing process 1. The sequence of events from raw material intake to the preparation of beer
overview for packaging and the typical points of use for raw materials and process aids.

2. A representation of the brewing process as a flow diagram.

2.2 Brewhouse plant 1. The purposes of milling with respect to the type of mashing / mash separation
operation – grain systems available.
handling and milling
2. The significance of grist fraction analysis (expressed in quantitative terms) and
its assessment.

3. The operating principles and diagrammatic representation of malt mills and

i
their associated malt preparation equipment.

4. Grain handling and safety.

2.3 Brewhouse plant 1. The operating principles and diagrammatic representation of mashing/mash
ii
operation – mashing conversion systems, including the cereal-cooking vessel, if appropriate.
and conversion
2. An awareness of the operational differences between isothermal (mash-tun)
conversion and temperature programmed conversion vessels.

3. A quantitative knowledge of typical times, temperatures and grist ratios used

in the conversion vessel.

4. The qualitative assessment of starch conversion.

2.4 Brewhouse plant 1. The operating principles and diagrammatic representation of wort separation
operation – wort devices.
separation
2. The significance of cycle times for brewhouse capacity.

3. Methods for the assessment of wort clarity / solids content.

4. Use of spent grains as a co-product.

Learning Material 2016 237

 Syllabus section 3: Wort boiling.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 4)
3.1 Wort boiling 1. The purposes of boiling: sterilization, stabilization of enzyme action,
evaporation, coagulation and precipitation of protein (trub formation) and
beer haze precursors, flavour development other than hop bitterness [see 3.2
below], and colour formation.

2. Factors affecting the effectiveness of wort boiling.

3. The purposes of liquid adjunct additions to the wort kettle.

3.2 Wort boiling systems 1. The operating principles and diagrammatic representation of wort boiling
iii
systems.

2. Typical boiling times and hop addition practices.

3.3 The nature of hop 1. The nature and origins of hops and hop products.
bitterness
2. Isomerization and how hops or hop products yield bitterness during wort
boiling.

3. How alternative or supplementary additions of hop bitterness are made at

later stages in brewing.

3.4 Hop calculations 1. How bitterness value of beer is expressed and typical values.

2. The bitterness potential of hops.

3. Calculation of required hop addition rates to achieve a given beer bitterness.

4. Calculation of hop utilization.

238 General Certificate in Brewing

 Syllabus section 4: Wort clarification, cooling and oxygenation (aeration).

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 3)
4.1 Wort clarification 1. The potential of trub constituents, spent hops, etc in boiled wort to detract
from beer quality.

2. Methods available for kettle fining.

3. Methods available for the removal of trub and / or spent hops.

4. The basic operating principles and diagrammatic representation of wort

iv
clarification devices.

4.2 Wort cooling 1. The purposes of wort cooling.

2. The effect of cooling on wort constituents.

3. Methods available for cooling wort.

4. The basic operating principles and diagrammatic representation of a type of

wort cooler.

4.3 Wort oxygenation / 1. The purpose of wort oxygenation. [See also section 5.2]
aeration
2. Methods of wort oxygenation / aeration and values achievable.

3. The basic operating principles and diagrammatic representation of wort

oxygenation systems, including the air or oxygen sterilization equipment.

Learning Material 2016 239

 Syllabus section 5: The basic principles of yeast fermentation.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 3)
5.1 Brewing yeast 1. Basic understanding of the relationship of brewing yeast to other living
organisms.

2. The differences between the bottom-fermenting/cropping (lager) and top-

fermenting/cropping (ale) yeasts in terms of their practical brewing
applications.

3. The microscopic appearance of a yeast cell.

4. The nutritional requirements of yeast derived from wort including trace

elements.

v
5.2 Fermentation theory 1. The production of alcohol and carbon dioxide from wort sugars by yeast.

2. Key flavour compounds produced by yeast.

3. The main phases and events of brewery fermentations.

4. The significance of the presence and absence of dissolved oxygen.

5. Other factors affecting the phases of fermentations.

6. Other factors affecting the speed of fermentations.

240 General Certificate in Brewing

 Syllabus section 6: Fermentation practice.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 2)
6.1 Fermentation vessels 1. General knowledge of the basic requirements of brewery fermentation
and their control vessels.

2. The operating principles and diagrammatic representation of fermentation

vi
vessels, the reasons for their choice, their advantages and disadvantages.

3. Reasons for temperature control.

4. Procedures for the temperature control of fermentations.

6.2 Health and Safety 1. The evolution of carbon dioxide from fermentations.

2. The hazards associated with carbon dioxide.

3. The monitoring / checking of atmospheres for safe working including a

quantitative knowledge of exposure limits.

4. Safe working practices for fermenting room operations.

Learning Material 2016 241

 Syllabus section 7: Yeast management.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 2)
7.1 Yeast propagation, 1. The reasons for yeast propagation.
storage and cropping
2. Basic procedures for producing a pure culture yeast.

3. The operating principles and diagrammatic representation of a yeast culture

plant.

4. The purposes and timing of yeast cropping.

5. The operating principles and diagrammatic representation of systems for the

vii
removal of yeast from a completed fermentation.

6. The monitoring of yeast growth.

7. The conditions necessary for the storage of either pressed or liquid yeast.

7.2 Yeast selection, 1. The selection of yeast for pitching.

treatment and pitching
2. Characteristics of healthy pitching yeast and the assessment of yeast condition
and purity.

3. Acid washing procedures including a quantitative knowledge of time,

temperature and pH ranges.

4. Yeast pitching methods.

5. The calculation of yeast pitching rate for a fermentation.

242 General Certificate in Brewing

 Syllabus section 8: Beer maturation and cold storage.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 2)
8.1 Warm maturation 1. The purposes of warm maturation.

2. Typical times and temperatures appropriate to different beer types.

3. Typical changes affecting beer flavour. [See also section 11.1]

8.2 Cold storage and 1. The purposes of cold storage.

stabilization
2. Typical times and temperatures appropriate to different beer types.

3. The general principles of stabilization.

4. Haze precursors and their removal.

5. The nature and action of the principal types of stabilizing agents.

Learning Material 2016 243

 Syllabus section 9A: Bright beer preparation (for Mainstream Brewery option A).

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 4)
9.1 Chilling and 1. The operating principles and diagrammatic representation of a beer chiller
carbonation (plate or shell and tube).

2. The purposes of carbonation.

3. Typical dissolved CO2 levels for different beer types.

4. Location in process of carbonation points.

5. The operating principles and diagrammatic representation of a carbonator.

9.2 Filtration 1. The purposes of filtration.

2. The principles of filtration – sieving, depth and absorption.

3. The origin, nature and preparation of filter aid – diatomaceous earth

(kieselguhr) and perlite.

4. The operating principles of a rough beer filter.

5. The types of beer sterilizing (polishing) filters available.

6. Representation of the sequence of events in a typical filtration system as a flow

diagram.

7. Awareness of alternative rough beer filter types – cross flow filtration.

8. The health and safety hazards associated with filter aids. Personal protection
equipment (PPE) and the plant safety features necessary.

9.3 High gravity dilution 1. Reasons for brewing at high gravity.

2. Typical quality specifications for water to be used for dilution (quantitative data
required).

3. Deaerated water production.

4. The calculation of blending quantities.

9.4 Considerations for 1. Cask conditioned beer.

other package types

244 General Certificate in Brewing

 Syllabus section 9B: Cask and craft beer preparation and packaging (for Craft option B)

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 4)
9.1 Cask beer preparation 1. The purposes of cask conditioning.
for racking
2. The importance of controlling yeast concentration / count, and typical values.

3. Conditioning and the necessity for residual fermentable sugars, with typical
values.

9.2 Clarification of cask 1. Clarification of cask conditioned beer.

beer
2. The origin, nature and action of auxiliary and isinglass finings.

3. Storage of prepared finings prior to use.

4. Typical addition rates and procedures for finings.

5. The operating principles and diagrammatic representation of finings addition

equipment.

6. Reasons for the addition of priming sugar.

7. Types of hops and hop products used for cask beer.

8. Reasons for addition of hops or hop products.

9.3 Cask washing and 1. Preparation and inspection of casks for racking.
racking
2. Cask filling practice, typical temperature specifications, filling volume control.

3. Conditioning in cask including storage temperature, the use of soft/hard pegs

and shelf life.

9.4 Craft beer preparation 1. The operating principles and diagrammatic representation of a beer chiller
for packaging (plate or shell and tube).

2. The purposes of filtration.

3. The principles of filtration – sieving, depth and absorption.

4. The operating principles of a small scale rough beer filter.

5. The types of small scale beer sterilizing (polishing) filters available.

6. The health and safety hazards associated with filter aids. Personal protection
equipment (PPE) and the plant safety features necessary.

9.5 Considerations for 1. Bottled conditioned beer.

other package types

Learning Material 2016 245

 Syllabus section 10: Beer quality and process control.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 2)

Key parameters examined in this section are:

Original gravity (OG), present gravity (PG), alcohol content (ABV %), pH, colour,
haze, bitterness, head retention or foam stability, dissolved oxygen, dissolved
carbon dioxide.

10.1 Process specifications 1. The variable nature of the natural ingredients of beer.

2. The purpose of process specifications.

3. Effects of the brewing process on the final product value of these key
parameters.

10.2 Process control 1. The principles of monitoring and adjustment to achieve product consistency.

2. Simple statistical quality control procedures.

3. The concepts of tolerance and range for specification parameter values.

4. Typical specifications which differentiate beer types.

5. Typical process specification ranges, especially those requiring periodic

adjustment to achieve product consistency [see Ref 10.1.above].

6. Typical applications for in-line and on-line instruments for process control.

246 General Certificate in Brewing

 Syllabus section 11: Beer quality – Flavour.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 2)
11.1 Terminology, 1. The reasons for adopting industry standard descriptors for flavour.
evaluation and tasting
during brewing 2. The flavour wheel.
operations
3. The more commonly used components.

4. Taste training procedures.

5. The three-glass test – statistical significance rating.

6. Flavour profiling.

7. Trueness to type panel tasting.

8. Common faults / contamination by contact materials that may be detected by

tasting during brewing operations.

Learning Material 2016 247

 Syllabus section 12: Beer quality – Dissolved oxygen.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 2)
12.1 The spoilage of beer 1. Sensitivity of beer to small amounts of oxygen – typical levels causing spoilage.
by oxygen
2. Basic mechanism for haze formation.

3. Oxidation reactions to form flavour compounds.

4. Typical flavour descriptors for oxidation effects.

5. Oxygen as a constituent of air.

6. Typical points of exposure of beer to air.

12.2 Monitoring and 1. Key control points.

control of dissolved
oxygen levels 2. The significance of sampling time.

3. Operating a dissolved oxygen meter.

4. Typical specified maximum levels.

5. Good practices to avoid oxygen pick-up.

6. The use of sulphur dioxide, ascorbic acid and potassium meta-bisulphite (KMS).

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 Syllabus section 13: Beer quality – Microbiological contamination.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 4)
13.1 Beer spoilage 1. Anaerobic growth.

2. Typical spoilage products formed.

3. Effects on beer quality of microbiological spoilage, appropriate use of flavour

descriptors to describe spoilage. [See also section 12.1]

13.2 Spoilage organisms 1. The principal categories of spoilage organisms:

Pediococcus, Lactobacillus, Acetobacter, Obesumbacterium, Megasphaera, wild
yeasts:
- their common points of contamination in the brewery.

13.3 Detection and 1. Methods of sampling for microbiological testing.

monitoring
2. Sampling points.

13.4 Control 1. Practices to protect against infection.

2. Measures to combat known sources of contamination.

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 Syllabus section 14: Quality management.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 3)
14.1 Features of a quality 1. The key features of a quality system:
system - written specifications
- written procedures
- monitoring of performance
- corrective actions
- auditing
- regular reviews for improvement

14.2 Roles responsibilities 1. The impact of individual actions on product and service quality.
and benefits
2. The control of documentation.

3. The maintenance of conformity.

4. The business benefits of an effective quality management system.

14.3 Product safety 1. The control of product safety

- Hazard Analysis Critical Control Point (HCCP).

2. The importance of traceability for product recall.

250 General Certificate in Brewing

 Syllabus topic 15: Plant Cleaning - Detergents and sterilizing agents.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 4)
15.1 Detergents 1. Types of detergent (alkali, acid and neutral).

2. The constituents of detergents.

3. The individual functions of the constituents.

4. Criteria for choice of detergent for an application.

5. Considerations for the use of hot detergent cleaning.

15.2 Sterilants 1. Types of sterilant as defined by the active agent.

2. Criteria for choice of sterilant for an application.

3. The effect of sterilant residues on beer quality.

15.3 Heat sterilization 1. Uses of steam and hot water as a sterilant.

2. Time and temperature.

15.4 Safety 1. The hazards associated with chemical cleaning and sterilizing agents.

2. Good practices for the storage of chemicals.

3. Use of personal protective equipment (PPE).

4. Procedures in case of accidental spillage or discharge of chemicals.

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 Syllabus section 16: Plant cleaning - Cleaning in-place (CIP) and general cleaning.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 4)
16.1 Types of CIP systems 1. The general differences between single use and recovery systems – advantages
and disadvantages.

2. The types of cleaning head used and reasons for their choice.

3. The operating principles and diagrammatic representation of CIP systems.

16.2 CIP cleaning cycles 1. Typical cleaning programs and cycle times.

2. The function of each of the cleaning cycle stages.

3. Quality assurance of cleaning operations.

16.3 CIP plant design 1. Design features that minimize soil accumulation in brewery vessels and
hygiene pipelines.
considerations
2. Design features that facilitate vessel and pipeline cleaning using a CIP system.

3. Design features which promote a hygienic working environment.

16.4 General plant cleaning 1. Cleaning plant surfaces, walls and floors.

2. The constituents of foam cleaning agents.

3. The use of foaming systems.

252 General Certificate in Brewing

 Syllabus section 17: Engineering basics and maintenance.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 3)
17.1 Engineering basics This subsection is not examined.

17.2 Brewing Plan 1. The key business reasons for an effective maintenance system.
Maintenance –
Approaches and Tasks 2. The features, advantages, disadvantages and applications of:
- no maintenance
- breakdown maintenance
- preventive maintenance
- predictive maintenance

3. The contribution of maintenance tasks to plant safety, reliability, quality,

economics and environmental impact.

4. Familiarity with key maintenance tasks:

- mechanical
- electrical
- calibration
- inspection
- condition monitoring
- cleaning of plant
- health and safety

5. Maintenance planning and record keeping.

6. Autonomous maintenance.

17.3 Performance 1. The key features of the following performance improvement systems:
improvements - Reliability Centred Maintenance (RCM)
- Total Productive Maintenance (TPM)
- Workplace Organisation (5S)

Learning Material 2016 253

 Syllabus section 18: Utilities – Water and effluent in brewing.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 3)
18.1 Water sources and 1. Characteristics and quality of an ideal brewery water supply.
treatments
2. Sources of water for a brewery.

3. The basic principles and diagrammatic representation treatment plants for:

- water filtration
- water sterilization
- water softening / deionization
- water de-aeration

18.2 Water types and uses 1. Differentiation and typical uses of:
- de-aerated water
- process water
- service water

2. Legionella in cooling water and service water and the health risks associated
with the micro-organism.

3. Points at which water is introduced into the process and the special water
quality needed at these points.

18.3 Sources of effluent 1. The nature and characteristics of effluent from principal brewery operations.
and its measurement
2. The components of effluent quality:
- volume
- suspended solids (SS)
- chemical oxygen demand (COD)
- biological oxygen demand (BOD)
- pH
- temperature

254 General Certificate in Brewing

 Syllabus Section 19: Utilities – Process gases.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to
be answered = 1)
19.1 Properties, 1. The essential properties and quality of compressed air and oxygen for use as
applications and process gases.
safety
2. The essential properties of carbon dioxide and nitrogen for use as process
gases.
viii
3. The practice and benefits of carbon dioxide collection.

4. The significance of inertness.

5. Typical uses for process gases.

6. The economic importance of leak prevention.

7. Safe handling and storage of compressed gas cylinders.

8. Safety hazards associated with storage of liquid gases and their distribution in
high-pressure mains.

Learning Material 2016 255

 Syllabus section 20: Brewing and the environment.

Ref. Topics Candidates should understand and be able to explain and describe in simple terms, or
demonstrate familiarity with:
(No. of questions to be
answered = 3)
20.1 Sustainability and climate 1. The concept of a sustainable industry.
change
2. The role of carbon dioxide – the carbon cycle.

3. Sources of carbon dioxide emissions.

20.2 Conservation 1. Principal energy consuming activities in a brewery.

2. Typical energy reduction strategies.

3. Principal water consuming activities.

4. Typical water conservation strategies.

20.3 Waste 1. Principal waste generating activities in a brewery.

2. Issues for waste disposal.

3. Strategies to minimize waste and encourage recycling.

Notes for examiners and tutors.

i
Options include 4, 5, and 6 –roll dry mills, wet mill, and hammer mill. The malt preparation equipment, appropriate to the type
of mill, includes screens, destoners, weighers and malt conditioning devices. Candidates should be aware of the different
operating principles of a dry roll mill, a wet mill and a hammer mill, and their association with the type of mash separation
device used.
ii
For decoction systems incorporating a cereal cooker, familiarity with the plant configuration is expected but the quantitative
data required is restricted to the temperatures achieved in the main conversion vessel. Details of volumes and cereal
temperatures are not required.
iii
Candidates may be aware of other systems, but questions will only be asked on ‘traditional’ wort boiling systems.
iv
Wort filtration systems using filter aids are not required.
v
Knowledge of metabolic pathways and yeast enzymes is not required.
vi
No knowledge of continuous fermentation systems is required.
vii
Includes green beer centrifuging, though questions will not be asked about the centrifuges themselves.
viii
No knowledge of the collection and compression plant is required. Candidates should be aware of the economic and
environmental arguments for collection [see section 20] and the operational procedures for the timing of collection.

256 General Certificate in Brewing