9
Malting, Brewing and Distilling
Introduction
The essential process involved in brewing is
the conversion of cereal starch into alcohol to
make a palatable, intoxicating beverage. Fermen-
tation is mediated by yeasts appropriate to the
cereal or cereals involved. Most yeasts used
belong to the species Saccharomyces cerevisiae,
which now includes the ‘bottom yeast’ previ-
ously classified as S. carlsbergensis (Reed and
Nagodawithana, 1991).
Two processes are involved: the starch has first
to be converted to soluble sugars by amylolytic
enzymes, and second, the sugars have to be
fermented to alcohol by enzymes present in yeast.
In the first process the enzymes may be produced
in the grains themselves (endogenously) or
exogenously, in other organisms present. Alter-
natively they may be added as extracts.
The process in which the grain’s own enzymes
are employed is known as malting. This comprises
a controlled germination during which enzymes
capable of catalyzing hydrolysis, not only of
starch, but also other components of the grain,
are produced. The most significant are the pro-
teases and the P-glucanases, as the products
resulting from their activities affect the qualities
of the beverage.
Other organisms are employed as a source of
enzymes in the production of sake - a beer
produced from rice. Enzymes are added in solu-
tion, particularly when it is required to hydrolyze
the starch etc. present in endosperm grits or
flours, themselves incapable of enzyme produc-
tion. Such adjuncts may provide any proportion
of the total starch, depending on legislation water.
relevant to the country of origin and the descrip-
tion of the product. Consequently, added enzymes
may contribute different proportions of the enzyme
complement.
The alcohol content of the liquor produced by
fermentation is limited by the tolerance of the
yeasts. Probably the most tolerant yeasts are used
in sake production. They can survive alcohol
contents of about 20% although the product is
sold in a diluted form.
Distillation allows the concentration of alcohol
into drinks described as spirits, the special
character of which depends on flavours imparted
by the processing or added to a distillate, the
added flavours usually being extracts from other
plant sources.
For alcohol production from plant material,
sugars must be present, as in fleshy fruits, or
other substrates from which fermentable sugars
can be produced. Starch is such a substrate, so
all cereals can be used for beer production. In
the West, the most commonly used cereal is
barley but substantial quantities are derived from
maize (beer in central America), rye (kvass beer
in the former U.S.S.R), rice (sake in Japan and
shaoshinchu in China), sorghum (beer in Africa).
Triticale may be used as an adjunct in beers.
Malting
During malting, large molecular weight com-
ponents of the endosperm cell walls, the storage
proteins and the starch granules, are hydrolyzed
by enzymes, rendering them more soluble in
21 8
MALTING, BREWING AND DISTILLING 219
malting barley is 1.5%; some 38% of this
appears in the beer in the form of soluble
nitrogen compounds, the proportion of the
total nitrogen entering the beer being some-
what larger from two-row than from six-row
types.
All cereals are capable of undergoing malting
but barley is particularly suitable because the
adherent pales (lemma and palea - see Ch. 2)
provide protection for the developing plumule, or
acrospire, against damage during the necessary
handling of the germinating grains. Further, the
husk (pales) provides an aid to filtration when the
malt liquor is being removed from the residue of
insoluble grain components. A third advantage
of barley lies in the firmness of the grain at high
moisture content.
Both two-row and six-row barleys (see Ch. 2)
are suitable: the former are generally used in
Europe, the latter in North America. Distinct
varieties were formerly grown for malting. They
were lower yielding than varieties grown for
feeding. Modern malting varieties have high
yields and are thus suitable for the less demanding
alternative uses also.
The characteristics required of a malting barley
are:
Dormancy
Harvest-ripe barley may not be capable of
germination immediately. While this is advan-
tageous in the field, protecting the crop against
sprouting in the ear, it is clearly a problem in
relation to malting, which depends on germina-
tion occurring. The mechanism of dormancy is
not fully understood and indeed it is unlikely that
a single cauSe is involved in all cases; in many
instances it has been shown that germination is
inhibited by inability of the embryo to gain access
to oxygen. A distinct phenomenon known as
‘water sensitivity’ can arise during steeping if a
film of water is allowed to remain on the Surface
of grains. The water contains too little dissolved
oxygen to Satisfy the needs of the developing
embryo and it acts as a barrier to the passage of
air. Dormancy declines with time and storage is
thus not just a means of holding sufficient stocks
of grain, it is an essential part of the process of
malting. During the storage of freshly harvested
barley tests are performed to detect the time at
which dormancy has declined sufficiently for
malting proper to commence. Both ‘dormancy’
and ‘water sensitivity’ are defined in relation to
the test performed. In one test 100 grains are
germinated on filter papers with 4 and 8 ml of
water, the difference between viability and the
germination on 4 ml of water is called dormancy
while the difference bemeen the levels of geda-
tion on the different volumes of water is the water-
sensitivity. Factors involved in controlling and
breaking dormancy have been reviewed by Briggs
(1978).
1. High germination capacity and energy, with
adequate enzymic activity.
2. Capacity of grains modified by malting to
produce a maximum of extract when mashed
prior to fermentation.
3. Low content of husk.
4. High starch and low protein contents.
The above qualities Can be affected by husbandry
and handling as well as by genetic factors: loss
of germination capacity can result from damage
to the embryo during threshing, Or overheating
during drying or storage.
Rovided that grains are ripe, free from fungal
infestation and intact, the yield of malt extract
should be directly related to starch content.
High-nitrogen barley is unsuitable for malting
because:
1. Starch content is lower.
2. Longer malting times are required.
3. Modification never proceeds as far as in low-
nitrogen barleys.
4. The greater quantities of soluble proteins lead
to haze formation and may provide nutrients
for bacteria and impair the keeping quality The practical steps in malting are shown
of the beer. The average nitrogen content of
Barley malting operations
schematically in Fig. 9.1.
220 TECHNOLOGY OF CEREALS
Malting
Clean, graded barley grains
At intervals the grain is mixed and turned to
provide more uniform growth opportunities, and
to prevent the roots from matting together. As
the embryo grows it produces hormones including
gibberellic acid, stimulating production of hydro-
lytic enzymes in the scutellum and aleurone layer,
leading to ‘modification’ of the starchy endo-
sperm. The malting process is regulated by the
initial choice of barley, the duration of growth,
the temperature, the grain moisture content,
changes in the steeping schedule,and by use of
additives. When modification is sufficient it is
stopped by kilning the ‘green malt’, that is, by
drying and cooking it in a current of hot dry air.
The dry, brittle culms are then separated and the
finished malt is stored. Dry malt is stable on
storage and, unlike barley, it is readily crushed.
Kilning Sprouts The conditions of kilning are critical in deter-
mining the character of the malt: it can cause a
slight enhancement of the levels found in green
Finished malt malt or completely destroy it. Malt contains
relatively large quantities of soluble sugars and
nitrogenous substances and, if it has been kilned
at low temperatures, it contains high levels of
hydrolytic enzymes. When crushed malt is mixed
with warm water the enzymes catalyze hydrolysis
of the starch, other polysaccharides, proteins and
nucleic acids accessible to them, whether from
the malt or from materials mixed with it. Malt
also confers colour, aroma and flavour to the
product. The solution of the products of hydrolysis
extracted from the malt is the ‘wort’. It forms
the feedstock for fermentation for brewing or
distillation (Briggs, 1978).
One of the benefits derived from the applica-
tion of technology in malting has been the reduc-
tion in time required to produce satisfactory
malts. The amount of time saved can be inferred
from the diagrams in Fig. 9.3. It is clear that
most saving has occurred during the present
1
Steeping
“Chit malt”
7
Germination
Green malt
1
+-Ma1t
+
Milling
Ground molt
FIG 9.1 Diagrammatic summary of the malting process.
Selected barley is ‘steeped’, usually by immer-
sion in water, for a period chosen to achieve a
particular moisture level. The water is drained
from the grain, which germinates. Conditions are
regulated to keep the grain cool (generally below
lS°C) and to minimize water losses. As the grain
germinates the coleoptile (acrospire) grows beneath
the husk and pericarp while the ‘chit’ (coleorhiza,
root sheath) appears at the base of the grain, and
is split by the emerging rootlets. Fig. 9.2.
0 1 2 3
FIG 9.2 Diagrammatic longitudinal sections through barley grains in the early stages of germination.
1. imbibed grain, 2. rootlets emerged, 3. Rootlets and coleoptile emerged. From Briggs (1978), Barley
(Fig. 1.11). Reproduced by courtesy of Chapman and Hall Ltd.
1686
1886
Germinate Kiln
IO-35d 4-6d
Steep
6-8d
-
3-7d 8-28 d 3-6 d
-
222 TECHNOLOGY OF CEREALS
Drive / Ra i I
Rotating
spirals
I
Perforated Humidificatibn system
floor (plus refrigeration
if required)
FIG 9.4 Diagrammatic section through a circular germination vessel. Source: Gibson 1989. Reproduced
by courtesy of Aberdeen University Press, Ltd.
'dry-casting' after draining. If additives are to be
added it is convenient to do so during transfer.
These may include gibberellic acid and potassium
bromate. The former hastens malting, especially
if bruised grains are present, and potassium
bromate reduces respiration and hence the rise
in temperature that accompanies it. It is also said
to inhibit proteolysis and control colour develop-
ment in the malting grain, as well as reducing
malting loss by reducing root growth.
Germination
Early mechanical maltings had rectangular
germination vessels, but this was followed in due
course by the drum, which provided ideal control
but is limited to about 100 tonnes and has a high
unit cost. Later the circular germination vessel
was developed and capacities rose to 500 tonnes.
Features common to all mechanical maltings are
an automatic means of turning the germinating
grains and a means of aeration. Turning may be
performed by rotating spirals that are moved
slowly through the grain mass. In the rectangular The objectives of kilning are to arrest botanical
vessels they move end to end on booms while in growth and internal modification, to reduce
the circular type vertical turners rotate on a boom moisture for grain storage, and to develop colour
or alternatively they remain stationary while the and flavour compounds in the malt. Kilning is
grain is transported past on a rotating floor. It is responsible for 90% of the energy consumption
usual for aeration to be provided by air passing of the entire malting process unless a heat recovery
up (usually) or down, from or into a 'plenum' is in use, when the proportion may be reduced to
beneath the floor which is constructed of slotted 75-80%.
steel plates. The layout of a circular germination For kilning, ambient air is heated by the pre-
vessel is shown in Fig. 9.4. ferred fuel and passed under positive or negative
Temperature and humidity are controlled by
humidifying and refrigerating or warming the air
passing through. Air volumes passing are of
the order of 0.15-0.2 m3/sec/tonne of barley.
Temperatures of 15"-19"C are common. Micro-
processor control of conditions is commonplace
JGibSnn, 1989).
The danger of microbial contamination is high
as air passing with high humidity is ideal for
growth of bacteria and fungi and nutrients are
plentiful. As well as introducing health hazards
microbes gain preferential access to oxygen, thus
inhibiting the germination and modification of
the barley for which the system is designed. In
some plants the germination and kilning are
carried out in a single vessel and this has the
advantage of the microbes being killed by the
heat of kilning. Cleaning the dry residue is easier
than complete removal of the wet remains of
germinating grain.
Kilning
MALTING, BREWING AND DISTILLING 223
pressure through the bed of grains. A plenum compounds is favoured by the combination of high
below the floor is provided as in the earlier stages temperatures with wet malts (Briggs, 1978). Small
of the malting process. A recent innovation in contributions to malt colour may be caramelized
kiln design is the double-deck version. In this sugars and oxidized polyphenols and other
system green malt is loaded on to the upper deck contributions come from aldehydes, ketones,
and transferred to the lower deck after partial alcohols, amines and miscellaneous other sub-
drying. Warmed air is passed first through the stances including sulphur-containing compounds
drier, lower bed before passing, unsaturated, to and nitrogenous bases. These are discussed in
the upper bed where it is capable of removing detail by Briggs (1978) and Palmer (1989). Peated
moisture from the green malt. distillery malts, for Scotch whisky manufacture,
The depth of green malt in a modern kiln is take up many substances from the peat smoke
0.85-1.2 m. For maximum efficiency the bed and contain various alkanes, alkenes, aldehydes,
should be level and uniformly compacted, a alcohols, esters, fatty acids, aromatic and phenolic
condition readily achieved by the automatic or substances, including phenol and cresols. The use
semi-automatic loading machinery available today. of peat as a fuel for kilning originated in cottage
Conditions for kilning are determined by the industry enterprises in the crofts of the Scottish
nature of the end product required. Variables Highlands where peat was the only available fuel
include the extract potential, moisture content, for domestic heating. In lowland distilleries peat
colour and enzyme activity. Curing temperatures heating has now been superseded by a succession
range from 80" to 100°C. In modern kilns the of fuels, currently oil or gas. Direct heating by
maltster is assisted in monitoring and controlling these fuels is not permitted as they can lead to
conditions by control programmes incorporated introduction of nitrosamines into the product.
into automated systems. Peatiness is a valued character of malt whiskies
Enzymes survive high curing temperatures however and direct heating with peat is the rule
best if the malt is relatively dry, but under these in their production.
conditions colour and flavour development are For production of brewing malts a major
minimal. They develop mainly as a result of economic consideration is brewer's extract. This
Maillard reactions occurring between the reducing is measured as hot water extract available as the
groups of sugars and amino groups, mainly of soluble nitrogen required to maintain fermenta-
amino acids. Development of additional flavour tion and beer quality properties. An analysis of
TABLE 9.1
Analytical Characteristics of Barley and Ale Malt
Constituent Barley Ale malt
Moisture content YO 15 4
Starch YO 65 60
0-D-glucan YO 3.5 0.5
Pentosans % 9.0 10.0
Lipid YO 3.5 3.1
Total nitrogen % 1.6 1.5
Total soluble nitrogen Oh 0.3 0.7
a-Amino nitrogen Oh 0.05 0.17
Sucrose o/o 1.0 2.0
Minerals Oh approx 2 approx 2
Colour "EBC under 1.5 5.0
Hot water extract (1"ikg) 150 305
Diastatic power (beta-amylase "L) 20 65
Dextrinizing unit (alpha-amylase) under 5 30
Endo P-glucanase (IRV units) under 100 500
Source: Palmer, 1989. Reproduced by courtesy of Aberdeen University Press.
224 TECHNOLOGY OF CEREALS
TABLE 9.2 fuel, 25-30%;
Characteristics of a Selection of Malts
electricity, 15-20%;
Malt type Extract Moisture Colour Final kilning wages, 15-20%;
(“/kg) (Oh) (“EBC) temperature repairs/maintenance, 10-20%;
(“C) miscellaneous, 15-25%.
Ale* 305 4.0 5.0 100
As with many wet processes of cereals the costs
Lager* 300 4.5 2.0 80
Cara pils 265 7.0 25-35 75
Crystal malt 268 4.0 100-300 75 of water treatment before discharge are increasing
70-80 150 as standards become more stringent. The Bio-
Amber malt 280 2.0
Chocolate malt 268 1.5 900-1200 220
Roasted malt 265 1.5 1250-1500 230 logical Oxygen Demand (BOD) load from a
Roasted barley 270 1.5 1000-1550 230 30,000 tonnes per annum maltings is equivalent
* Of all the malts listed only ale and lager malts contain to a PoPulation of about 9000 People (Gibson,
enzymes. 1989).
Source: Palmer, 1989. Reproduced by courtesy of Aberdeen
University Press.
ale malt compared with that of barley is shown
in Table 9.1. The characteristics of brewers malts
of various types are given in Table 9.2.
Ageing
Before use it is necessary to mill kilned malts
but it is customary to delay this process to permit
moisture equilibration. Kilning effects drying
rapidly and in individual grains a gradient exists
from a higher inner to a lower outer (husk)
moisture content. Differences in a malt of 3-5%
m.c. may be 4 or 5% (1-3% outside to 5-8%
inside). Unless equilibrated, agglomeration of the
damper parts can reduce extraction potential and
undue fragmentation of dry husk leads to haze
in the extract (Pyler and Thomas, 1986). Storage
for up to 3 months may be used. As specifications
become increasingly sensitive to moisture content
the conditions of storage progressively include
humidity control (Palmer, 1989).
Energy consumption and other costs
The Energy Technology Support Unit published
a report in 1985 of a survey of United Kingdom
maltsters. Specific energy consumed per tonne of
malt ranged from 2.48 to 6.81 GJ, with a weighted
average of 3.74 GJ. Quoted costs included fuel
and electricity. Power costs comprised grain
handling and process requirements.
Estimates of proportionate costs, including
these values are given by Gibson (1989) as:
Malt production
Palmer (1989) reports that about 17 million
tonnes of barley are used annually, world-wide , to
produce 12 million tonnes of malt and about 970
million hectolitres of beer. This represents about
10% of world barley production.
By-products of malting
The main by-product of malting is called ‘malt
sprouts’. They are separated from kilned malt by
passing the malt through revolving reels or a wire
screen. They account for 3-5% of product and
they are incorporated into stock feeds. Typically
they contain 25-34% N-compounds, 1.6-2.2%
fat, 8.6-11.9% fibre, 6.0-7.1% ash and 3544%
N-free extract (Pomeranz, 1987).
Non-brewing uses of malt
Milled barley malt is used as a high diastatic
supplement for bread flours which are low in
natural diastatic activity, and as a flavour supple-
ment in malt loaves. Malt extracts and syrups are
produced by concentrating worts by evaporation.
Malt is also used in the manufacture of malt
vinegar.
Adjuncts
Although malt derived from barley is generally
considered to be the superior feedstock for brewing
and distilling, it is common practice in many
MALTING, BREWING AND DISTILLING 225
countries to supplement malt with alternative Solubility of proteins is decreased and some
sources of soluble sugars or starch capable of flavour may be introduced through their use if
conversion to soluble sugars. adequate treatment temperatures are used in
The principal adjuncts, as such non-malt addi- processing them. Heat treated cereals can be
tives are described, are rice, maize grits and added to malt before grinding; their extract yield
cereal starches. Adjuncts contribute virtually no is increased if they are precooked before use.
enzymes to the wort so hydrolysis of their starch Investigations with extruded cereals gave poorer
depends upon those enzymes present in the malt extract yields than traditional adjuncts (Briggs et
to which they are added. Use of adjuncts is al., 1986).
common practice in the U.S.A. and this is one Sorghum was used more in the U.S.A. when
reason for the preference there for the higher maize was in short supply during World War 11,
enzyme-containing six-row barleys. and it is used to a significant extent in Mexico
In the U.S.A. 38% of total materials used in today. It has a lower fat and protein content and
brewing (excluding hops) was reported to be a higher extract than maize and it thus has some
contributed by adjuncts (Pyler and Thomas, merit.
1986). Of this 46.5% was corn grits, 31.4% rice Barley and wheat starch have a lower gelatiniza-
and 0.7% barley. Sugars and syrups accounted tion temperature than maize and rice starch,
for the remaining 21.4%. hence digestion may occur at mash temperatures.
The form in which rice is added is the broken It is usual, however, to premash maize, rice,
grains that do not meet the requirements of milled wheat and barley etc. by cooking with a small
rice. As the quality of the products of fermenta- amount of malt before adding them to the mash.
tion is little affected by the nature of the adjunct, Addition of barley provides a means of reducing
the choice is usually made purely on economic the nitrogen content of the wort. It is disallowed,
grounds. This is not related only to the price per however, by the German beer law for the produc-
tonne of the adjunct because the yield of extract tion of bottom-fermented beers in which only
is not the same from each. Tests for extraction barley-malt, hops, yeast and water are allowed.
carried out in the laboratory generally give higher Top-fermented beers follow the same regulations
values than those obtained in the commercial but wheat malt may be included (Narziss, 1984).
practice. Pyler and Thomas quote 78% for rice For special beers, pure beet-cane-invert-sugar is
and 74% for maize grits in the brewhouse and allowed.
87-94% and 85-90% respectively in the laboratory
(American SOC of Brewing Chemists procedure).
Malts from ot,er cereals
Maize grits also contain higher levels of fat and
protein than rice, both of which constituents are In Africa many malts are produced from
considered undesirable. sorghum and, to a lesser extent, from millets. In
Other adjuncts used are: refined maize starch, the Republic of South Africa commercial produc-
wheat and wheat starch, rye, oats, potatoes, tion is of the order of 1000 m litres annually
tapioca, triticale, heat treated (torrefied or micro- and home brewing may be of the same order
nizec!) cereals, cereal flakes. Micronization invol- (Novellie , 1977).
ves heating grains to nearly 200°C by infrared Wheat malt is used in the production of wheat-
radiation while torrefication achieves similar malt beers. Examples of these and their character-
temperatures by use of hot air (Palmer, 1989). istics are shown in Table 9.3.
In grains treated by either method the vapourized Malts made on a pilot scale from U.K.-grown
water produced disrupts the physical structure triticales were evaluated by Blanchflower and
of the endosperm, denaturing protein and par- Briggs (1991). Viscosities of resulting worts were
tially gelatinizing starch. Digestibility is thus high due to pentosans, particulaly arabinose and
increased and these products are also used in xylose. Hot water extracts after five days germina-
cattle feeds and whole-grain baked products. tion were 302-324 litre degree per kg. Filtered
226 TECHNOLOGY OF CEREALS
TABLE 9.3
Beers Made From Wheat-Malt and their Characteristics
Type Character Origin Alcohol Flavour features
(Yo v/v)
Weizenbeer LageriAle Bavaria 5-6 Full bodied, low hops
Weisse Lager Berlin 2.5-3 Light flavoured
Gueuze-Lambic Acid ale Brussels 5+ Acidic
Hoegards wit Ale East of Brussels 5 Full bodied, bitter
Source: Pomeranz, 1987, citing information from A. A. Leach of the Brewers' Society, U.K.
worts were turbid owing to proteinaceous materials.
Malt yields were between 87 and 90%
sugars. Hops are also added at this stage. As well
as adding flavour they serve to sterilize the wort
and participate in reactions that precipitate proteins
responsible for haze when the wort is boiled.
Boiling may continue for 1.5-2 h. During boiling
the humulones, or a-acids are isomerized to the
bitter iso-a-acids. As the yield of bitter iso-a-acids
Beer
extracted from the hops by boiling may be as low
Wort production
as 30%, a modern procedure is to replace part of the
The starting material for brewing may be pure raw hops by a pre-isomerized hop extract, which is
(usually barley) malt, or a mixture of malt and added to the beer after fermentation. It is com-
adjunct. If solid adjuncts are to be included they mon for half the hops to be added at the beginning
may be milled with the malt. The coarsely ground of the period and half at the end. The wort is
material, on hydration with brewing liquor, cooled (to 15.5"-18"C for British ales or to 4"-7"C
produces a brewers' extract from the solubles, for pilsners and lagers), filtered and transferred to
and a filter bed from the husk. The quality of pitching tanks where it is 'pitched' with yeast (Le.
the filter bed depends on the size of the husk yeast is added). Air is also passed into the hopped
particles; they should not be too fine. The process wort to provide a supply of oxygen for the yeast
is known as mashing and it is carried out in vessels which rapidly becomes active (added oxygen
called mash tuns. removes the lag phase that would otherwise occur).
After an initial rest for hydration to be completed
Fermentation
the temperature is raised above the gelatinization
temperature of the starch. This renders the starch
much more susceptible to digestion by amylase Yeasts vary in their behaviour during fermenta-
enzymes, to produce soluble sugars. The process tion, some strains tend to flocculate, as a result
of conversion, begun during malting, thus con- they trap C02 and rise to the top. Others, which
tinues during this phase. do not flocculate, sink to the bottom. Several
It is now necessary to separate the liquid wort styles of lagers are produced by bottom fermenta-
from the solid remains of the malt and adjuncts, tion while many types of ales and stouts are
and this is done by a process called 'lautering'. produced using top fermentation. Examples are
The spent grains act as a filter bed when the given in Table 9.4.
mixture is transferred to a lauter tub, which has An efficient type of fermenter is a deep
a perforated bottom. The spent grains accumulate cylindrical vessel with a conical base into which
on this and allow the liquid to pass through while the yeast eventually sediments. In such vessels
retaining the fine solids. The sugary liquid is the liberation of carbon dioxide provides efficient
known as the 'sweet wort'; it is supplemented agitation, allowing cycles of filling, fermentation,
with syrups at this stage if such adjuncts are to emptying and cleaning to be accomplished in 5
be used to increase the amount of fermentable days at 12°C or 2.5 days at 18°C.
Brewing
MALTING, BREWING AND DISTILLING 227
TABLE 9.4
Classical Beers of the World Classified According to Yeast Types Used in their Brewing
Type Character Origin Alcohol Flavour
(Oh viv) features
Bottom-fermented
Munchener Lagedale Munich 4-4.8 Malty, dry, mod. bitter
Vienna (Marzen) Lager Vienna 5.5 Full-bodied, hoppy
Pilsner Lager Pilsen 4.5-5 Full-bodied, hoppy
Dortmunder Lager Dortmund 5+ Light hops, dry, estery
Bock Lager Bav., U.S., Can 6 Full-bodied
Dopplebock Lageriale Bavaria 7-13 Full-bod., estery, winey
Light beers Lager U.S. 4.2-5 Light-bodied, light hops
Saissons Ale Belgium, France 5 Light, hoppy, estery
Trappiste Ale Bel. Dutch Abbeys 68 Full-bodied, estery
Kolsch Ale Cologne 4.4 Light, estery, hoppy
Alt Ale Dusseldorf 4 Estery, bitter
Provisie Ale Belgium 6 Sweet, ale-like
Ales Ale U.K., U.S., Can., Aus 2.5-5 Hoppy, estery, bitter
Strong/old ale Ale U.K. 68.4 Estery, heavy, hoppy
Barley wine Ale/wine U.K. 8-12 Rich, full, estery
Stout (Bitter) stout Ireland 4-7 Dry, bitter
Stout (Mackeson) stout U.K. 3.7-4 Sweet, mild. lact. sour
Porter stout London, U.S., Can 5-7.5 V. malty, rich
Source: Pomeranz, 1987, using information from A. A. Leach of the Brewers’ Society, U.K.
Fermentation continues for 7-9 days, producing
ethanol and carbon dioxide. The gas may be
collected for sale or for adding back when the
beer is bottled or casked. The reaction is exo-
thermic and the temperature would rise unduly
if not controlled- The Yeast increases during
fermentation through asexual reproduction and
in consequence this constitutes an additional
by-product- During fermentation the PH drops
from 5.2 to 4.2 as a result of acetic and lactic
acids synthesized by bacteria inevitably intro-
Top-fermented
Two thirds of the world’s sake production takes
place in Japan.
An essential difference between beer and sake
is that for sake the natural enzymes present in
the grain are not employed in solubilizing the
starch, indeed they are expressly inactivated
before the saccharifying phase of sake brewing.
E~~~~~~ are of cOurSe needed and these are
derived from the fungus Aspergillus 0 yzae, they
are provided from a culture of that mould known
as ‘koji7. Koji contains 50 different enzymes
duced with the yeast. The green (jargon for
young) beer is run Off from the aggregated yeast
including the alpha- and bela-amylases present
in malt and an additional amylolytic enzyme
cells and cooled to precipitate further haze-
producing proteins and aged before filtering and
carbonating. Lagers are stored at 0°C for some
weeks (‘lagering’) before packaging into bottles
amyloglucosidase (see Fig. 3.12, p. 67), capable
of hydrolyzing starch polymers to glucose. The
balance of amylase to protease is inflenced by
or kegs. An alternative treatment is for the green
beer to be run into casks, primed with sugars to
cultural conditions, figher temperatures favouring
amylase Production. The process is summarized
permit secondary fermentation and ‘fined’ with
isinglass for sale as ‘naturally conditioned’ beer; a
product peculiar to the British Isles. (The brewing
process is summarized schematically in Fig. 9.5.)
Sake
in Fig* 9*6.
The Yeast used in sake Production is a specialized
strain of Saccharomyces ce~visiae.
Unlike the husk of barley in the malting
process, that of rice is not valued for its filtration
properties, nor indeed any other qualities. It is
removed by milling (see Ch. 6). The degree
of polishing is severe; removing 25-30% of Sake uroduction was reuorted to be 15 x lo5
1
and water is again made. A third addition is made
the following day and fermentation increases in
vigour, raising the temperature from about 9°C
Wort cooling Yeast
tion of the sake. Maturation takes 3-8 months
MALTING, BREWING AND DISTILLING 229
Acidified seed mash Steamed rice and water
+I+ Main mash Steamed rice
Alcohol ++ Main mash Steamed rice
Compression and
Lw f il tration
Sakh
Clarification and
filtration
Pasteurisation
I Maturation
Blending, dilution
bottling, pasteurisation
FIG 9.6 Schematic summary of sake production.
Scotch Malt Whisky is produced by traditional Traditional malt whisky
low temperatures (to retain enzyme activity),
The first worts are run off before mashing at a
higher temperature of 70°C and running off of
that is fermented. Two further worts are produced
methods> using ma1t as the "le carbohydrate
Well modified, peated malt is dried at relatively
source (by legal definition).
Scotch whisky that is made from a mash of cooked
grain, and saccharified by the action of enzymes
barley or wheat.
Grain Whisky is the cQmponent Of b1ended
milled and mashed at temperatures of 64045°C.
from ma1ted bar1ey. The grain may be maize,
a second wort. Both WOrtS become the liquor
In Bourbon whiskey the grain in the ma'h
consists of at least 51%, and usually 60J0°h,
from mashes at 80" and 9PC, and are used as
mashing liquor for subsequent grists. Batches
maize. Typically some rye is included to impart of 5-10 tonnes of mait are typical.
a spicy, estery flavour. Although included, malt Fermentation is preceded by cooling to
contributes only 10-15% of total carbohydrate. 20"-21"c, and is initiated by pitching with dis-
tiller's yeast. Yeasts are of the high attenuation
type (tolerating high alcohol levels) grown in
molasses and ammonium salts. They are also
selected to produce appropriate flavours. After
3648 h, alcohol content reaches 8% and the
temperature reaches 30°C.
Rye whiskey contains at least 51% of rye, Irish
whiskey is made predominately from malted or
unmalted barley, with wheat, rye or oats making
up the remaining 20%. Canadian whiskies are
mainly blends of neutral grain whiskies (90%)
and Bourbon or rye (Nagodawithana, 1986).
collected as the basis of the marketable product.
oak casks, over a period of at least three years
It contain 68% alcohol but it has to mature in
1
Cooker
MALTING, BREWING AND DISTILLING 231
Temperatures during cooking may be 100°C
under atmospheric conditions or 160°C if high
pressure cooking is used. The pressure cooking
saves time (5 min instead of 30-60 min at the
highest temperature).
Amylases are added at appropriate temperatures
as the mash cools: bacterial at 85”C, fungal at
63°C and amyloglucosidase at 60°C. Fermenta-
tion is achieved by yeasts selected for their high
rate of alcohol production and their tolerance of
high alcohol levels, possibly 8-9%. Continuous
distillation of the resulting beer produces an
alcohol content of 95%.
Still, named after its inventor (Bathgate, 1989).
A summary of Scotch grain whisky production
is given in Fig. 9.7.
Bourbon whiskey
Maize and other cereals to be mashed are
ground in a hammer mill prior to addition of malt
and water. Water is added at the rate of 6-7.4 l/kg.
and some stillage may be included to adjust the
pH to 5. Although a total of 10-15% of malt is
finally present only 1-5% is added initially,
the remainder (‘conversion malt’) being added
following cooling after the cook. Cooking consists
of raising the temperature to 70°C and holding
it for 30-60 mins. It is cooled to 63°C for the
conversion of starch to sugars to be completed.
Further cooling follows before the whole mash is
Pumped to a fermentor where it is Pitched with
2% V/V Yeast- The rise in temperature due to
fermentation is not allowed to exceed 35°C.
Fermentation takes about 72 h, the resulting
Product is known as ‘drop beer’ and this iS
distilled in a COntinuous cohu-nn distillation system
(Nagodawithana, 1986).
Neutral spirits 1988).
The beer for neutral spirits distillation is
produced as economically as possible as flavour
is an undesirable attribute and expensive means
Of producing flavours (as in whisky) are unneces-
sary. Only the chemistry of conversion of starch
to sugars and of sugars to alcohol has to be
considered. The cheapest source of starch is used.
In countries where maize can be grown that cereal
be cheaper.
It is more economical to use enzymes derived
from ~cro-oganisms than those from malt. ~~~al
and bacteria1 enzymes are thus Used in this
process. A further advantage is that amylogluco-
sidase is available from microbial sources. Adjust-
ment of pH is achieved by use of chemicals,
calcium hydroxide being added to the suspension
Of ground cerea1 introduced into the cooker to
achieve pH 6.3 and dilute hydrochloric acid
adjcrsring rhe pff Co 4.5 before saccharification.
By-products of Brewing and Distilling
The largest quantity of by-products consists of
the solids remaining after the final sparging,
leaving spent grains in the case of brewing and
distiller’s dark grains. They are valued as cattle-
feed. yeast is saleable and co2 may be worth
harvesting for sale if produced in sufficient
quantity. Fusel oils, including the following com-
ponents: furfural, ethyl acetate, ethyl lactate,
ethyl decanoate, n-propanol, iso-butanol and amyl
alcohol, are used in the perfume industry (Walker,
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