TECHNICAL SUMMARY

Malt specifications & brewing performance

When buying malt, the brewery Both methods give a prediction of brewhouse
is looking for a product, which Technical Summary 10 performance. However under laboratory
conditions mashing are not optimised which
will yield the most economic By Tim O’Rourke explains how extract recoveries of greater
extract (wort) and will operate than 100% can be achieved with more
satisfactorily under brewhouse Continuing this series of modern mashing and wort separation
conditions and throughout the technical summaries for techniques such as the modern mash filter.
brewing process. Malt, which is the Institute & Guild’s
The factors which favour high extract
difficult to handle can cause AME candidates.
recovery include:
quality and process problems
involving additional costs. To characteristics through its genetic make-up 1. Varietial effects – different barley varieties
ensure that an appropriate malt which will determine certain properties of give different yields
is supplied the brewer will set important to brewing. Some varieties produce 2. The total nitrogen content – the higher the
better malt than others. nitrogen the lower the extract.
and agree a suitable Barley variety will influence malt quality in 3. Corn size – large even corns size give better
specification with his supplier. terms of variables such as: malting and milling performance.
4. Modification – the malt should be
• % nitrogen or protein in grain (see later) adequately but not over-modified – see

B rewhouse performance of the malt is

affected by the interactions between malt
quality and:
• % beta-glucan after malting
• Size and homogeneity of grain – plumper
later.
5. Enzyme capacity – the malt should have
grains yield better extracts and are easier to sufficient enzymes to degrade the starch
malt and mill. Most brewers specify that all and convert it to simple sugars.
• The type of brewing process. grains should be ≥ 2.2 mm 6. Low in gums – extract recovery can be
• The type of brewhouse equipment. • Not all barley varieties have similar abilities to reduced by the presence of gums –
• Other materials that are used with the malt produce enzymes, this can be important particularly beta-glucans in the malt. This
e.g. adjuncts. particularly when using high levels of problem is often resolved by the addition of
adjunct. exogenous beta glucanase.
The brewer has certain objectives when
purchasing malt: The environment also influences these Malt Nitrogen (usually expressed as %
factors, e.g. weather, soil type and the use of nitrogen)
• To recover a high yield of sugar (extract) from fertiliser. The higher the level of nitrogen the lower the
the malt. The barley variety used to make the malt is % extract. Therefore brewers specify the %
• That the malt will operate satisfactorily in the considered important not only because of its nitrogen or protein in malt.
plant without additional processing or brewing properties, but because of special
treatments. characters it gives to the finished beer. Today Typical % nitrogen is in the range of :
• The malt will pass through the plant within many traditional ale brewers still specify Maris Ale Malt 1.4 – 1.6%
the required cycle time (run off time). Otter as they believe it makes better quality Lager Malt 1.6 – 1.8%
• The wort produced from the malt provides all beer, even though this variety is no longer (Nitrogen is sometimes expressed as
the necessary nutrients to ensure a recommended because of its poor yield and % protein which is % nitrogen x 6.25)
satisfactory fermentation. agronomic performance.
• The malt delivers the flavour and process However nitrogen plays an essential role in
requirements of the brewer and his Extract Yield the quality of the beer:
customers. Extract is a measure of the amount of sugar
recovered from the malt after mashing. The • Nitrogen, in the form of amino acids, is
All of these benefits are supplied on consistent extract value is based on a laboratory mash. required for yeast growth with typical values
and reliable basis. There are two basic laboratory procedures of 160 to 240 mg/l depending on yeast
used for measuring extract. strain and wort gravity.
Malt specifications • Hydrophobic nitrogen from the malt provide
Barley, and the malt produced, is derived from • The IoB method, which involves mashing the beer foam and head retention in beer.
natural living material, and hence subject to all 10% malt with, distilled water and letting the • Some long chain polypeptides cause
the variations which can occur as a result of mash stands for 60 minutes at 65°C. The colloidal instability (chill and permanent
genetic and environmental conditions. It extract is measured as the specific gravity of haze) in beer and have to be reduced in the
follows that no two batches of malt are alike. the filtered solution at 20°C. The results are brewing process.
Malt is analysed in accordance with expressed as litre degrees per kilogram. • Proteins and polypeptides contribute to the
standard industry tests such as the IoB, EBC • In the EBC (European Brewery Convention) texture and mouthfeel of the beer. Excessive
and ASBC methods of analysis. However, method two mash stand temperatures of removal leads to a thin tasting beer with
standard malt specifications are not always a 45°C and 70°C are used. The Extract is poor foam.
reliable indicator of how well the malt will expressed % sugar (sucrose) over total
perform in the brewery. Brewers and maltsters weight of malt It is important to ensure a avoid excess
are continually looking for better predictions of nitrogen in the barley, but ensure sufficient of
brewing performance of a malt. Extract value for typical malt made from the nitrogen available is broken down to
standard 2-row barley. soluble nitrogen. The ratio of total to soluble
Barley variety Malt extract “dry” IoB l°/kg EBC°Plato nitrogen is an important indicator or brewing
There is a list of approved barley varieties for Standard ale malt 305 – 315 81 – 82 performance. Most of the nitrogen breakdown
malting. Each barley variety has its own Standard Lager malt 300 – 310 80 – 81 occurs during malting.

The BREWER International • www.igb.org.uk • Volume 2 • Issue 10 • 2002

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TECHNICAL SUMMARY

Moisture (usually expressed as % moisture) observation of the endosperm and evaluate

The lower the % moisture, the higher the the degree of modification. It is found that
extract in the malt. Malt specifications express these observations correlate well with brewing
the extract as “extract dry” or “extract as is” – performance.
which includes the moisture content.
The darker the malt colour, the higher or Indirect measurements
longer the kilning time. This results in lower % Another way of measuring modification is
moisture. Because of their darker colour ale assessing factors influenced by the
malts tend to have a lower % moisture than Figure 1 – Process of modification of a barley breakdown of the endosperm structure in the
lager malt. corn. grain:
Kilning uses a large amount of energy. The
next process stage after kilning is mashing 1.During malting the protein matrix, which
when the malt is re-hydrated, There is no surrounds the starch granules inside each
benefit in excessive moisture reduction and storage cell is broken down. The greater the
the trend is to move to higher lager malt value of soluble nitrogen, the higher the
moistures to reduce energy costs. For safe modification. The IoB analysis it is usually
storage and good milling performance malt expressed as the “Soluble Nitrogen Ratio”
moisture should not exceed 6%. (SNR), which is the soluble nitrogen/total
The higher the moisture, the lower the nitrogen expressed as a %. The EBC method
extract yield per tonne of delivered malt. This uses a similar ratio based the EBC mash
has to be adjusted in the price since the Figure 2. Before – showing the beta glucan cell where it is called the Kolbach Index.
brewer wants to pay for malt not water. walls surrounding the starch granules in the
endosperm before in barley before malting. 2. Unless the malt is fully modified a number of
Typical % moisture values for standard malts: cells within the endosperm will not be
degraded and will remain intact with coarser
Standard ale malt = 2 – 3% moisture milling. When the malt is mashed the
Standard lager malt = 4 – 6% moisture enzymes will not be able to penetrate the
cells and gain access to the starch. These
Colour cells are ruptured with fine milling and the
During kilning chemical reactions take place extract can be recovered. Another
between the malt components to produce measurement of modification is the
colour compounds. There are a number of course/fine difference, which measures the
colour and flavour reactions. The principal difference in extract yield between finely
reaction is between amino acids and sugars Figure 3. After – showing how the cell structure and coarsely ground malt. The smaller the
called the “Maillard reaction” which produces has been stripped away exposing the starch difference the better the modification.
both colour and flavour active compounds. granules, which can now be degraded by
The higher the kilning temperature, the enzymes during mashing. 3. During malting the cell walls in the
greater the amount of colour compounds endosperm are dissolved away making the
Thanks to Professor G. Palmer, Heriot Watt University, for
produced. As well as producing colour, these grain softer and easier to mill. It is possible
permission to use the electron-micrographs.
compounds also contribute to flavour. to use this property to measure the degree
The colour of the malt is based on the colour of modification, by measuring the amount of
obtained from the IoB or EBC mash using a in a number of ways: energy required to grind the malt (Friability).
10% solution. This colour value provides an The method takes 50 grams of malt which is
approximate indicator of final beer because it Direct observation milled with a constant pressure over a mesh
is based on a dilute laboratory mash with an The electron micrographs clearly show the screen. The well modified grain will fall
original gravity of 1030° (8°Plato). Further degradation of the cell walls. This is a through the screen leaving the chunks of
colour develops during wort boiling. complicated and expensive technique for under-modified malt. The weight of ground
routine analysis. malt indicates the degree of modification. It
However, the presence of cell wall material also measures the homogeneity or
Modification
can be detected using a calcofluor stain. The evenness of modification.
Before the brewer can break down the starch
calcofluor dye binds with beta-glucans (cell
in malt to sugars during mashing, the maltster
wall material) and fluoresces under UV light. 4. Cold water extract measures the amount of
has to break down the cell structure in the
Thus if sectioned grains are exposed to this sugars broken down and released during
endosperm to make the starch granules
dye those parts of the corn rich in beta-glucan the malting process. – higher cold water
accessible. This process is called modification
will fluoresce. This technique can be used to extracts indicate higher modification (see
and is the most important measurement when
determine both the proportion of corns that Table 1).
predicting brewing performance and extract
have modified as well as the extent of
yield from malt.
modification within individual corns. It is important to use malt that has been
Modification gives a measurement of how
By taking a series of transverse sections correctly modified:
evenly the cell structure in the endosperm has
through the gain it is possible to make direct In under-modified malt all the cell walls have
been broken down during the malting process.
Enzyme activity starts from the embryo and Table 1: Typical specification for modification in pale ale and well
the aleurone layer surrounding the endosperm modified lager malt.
to break down the protein and beta-glucan cell
walls surrounding the starch granules (see Index of modification Pale Ale Malt Lager Malt
Figure 1). Kolbach % (Sol N/Total N) 38 – 39 40 – 43
The process of modification has the effect Course/Fine difference (l°/kg) 3–6 2–3
of stripping away the cell wall structure and is Friability % ≥ 95 ≥ 95
shown in the two electron micrographs Homogeneity % ≥ 88 ≥ 82
(Figures 2 and 3). Cold water extract % 1.8 – 2.0 2.0 – 2.2
The degree of modification can be measured

Volume 2 • Issue 10 • 2002 • The BREWER International • www.igb.org.uk

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not been broken down, it usually has a lower the starch to produce shorter chains and The contribution of malt to flavour
soluble protein content (SNR is lower) and reduces the viscosity. The activity of the Malt is the principal ingredient in beer
there may still be small starch granules enzyme is measured by the length of time supplying sugar to the yeast which produces
present which can give starch conversion and required to break down a standard starch alcohol. In addition to sugar, yeast requires a
haze problems. Under-modified malt will give solution to a specific colour standard using variety of essential nutrients which are
brewhouse problems and give poor extract an iodine indicator. The activity is expressed necessary for satisfactory yeast growth and
recovery. as dextrinizing units (DU). nutrition. The typical components required
In over-modified malts the cell structure is include:
fully broken down, the soluble protein is higher • The other enzyme, beta amylase attacks the
(high SNR), and most of the small starch non reducing end of the starch chain to • Simple sugars (glucose, maltose and
granules have be broken down. It is much produce maltose sugar. The enzymic power maltotriose) for fermentation
easier to recover but extract from over is measures as DP (Diastatic Power in • Amino acids (free amino nitrogen > 150 mg/l)
modified malt, but some extract may have °Lintner) in the IoB methods of analysis. for yeast growth
been used up during the malting process. • Mineral ions for enzymes – typically zinc,
Excessive nitrogen breakdown may lead to The DP is around 35 – 40 for standard Ale copper etc
loss of foam positive proteins and poorer beer Malts, but can be as high as 100 to 125 for • Vitamins for healthy growth
foam performance. lager malts and over 160 for some high protein • Some lipid material for cell wall production –
six row North American malts. The latter malts although yeast manufactures most of these
Enzyme Activity. have far more enzymic power than they compounds using available oxygen in the
The principal activity of malting is to require just to convert the starch from the malt wort.
encourage the barley to produce its own itself and enable the brewer to use high levels
enzymes. Some of the enzymes are required of unmalted starch adjuncts (see a later During fermentation yeast will produce a
during malting to modify the corn structure. series.) number of flavour compounds as a direct
The other enzymes, principally the Diastase In EBC analysis the diastatic power is consequence of metabolising brewing wort.
enzymes (which break down starch) are measured as °WK (Windisch-Kolbach units). Changes in wort composition will influence
required to work during mash conversion in The value of °WK can be converted to °Lintner this metabolism and hence the flavour of the
the brewhouse. by the formula: beer produced.
There are two principle diastatic enzymes:
DP °Lintner = (°WK + 16) / 3.5 Malt also contributes directly to the appear-
• Alpha amylase which randomly hydrolyses ance final character and taste of the beer:

Murphy Half
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The BREWER International • www.igb.org.uk • Volume 2 • Issue 10 • 2002

29
TECHNICAL SUMMARY

• Most of the colour of beer comes from the

Typical Specification for a Lager Malt.
crushed malt or is developed during the
brewing process from reactions between Specification IGB (Institute & Guild EBC (European Brewery
malt components. of Brewing) methods: Convention)
• The colour compounds also give beer a Moisture 4.5 – 5.5 % 4.5 – 5.5 %
characteristic flavour from light biscuity Extract yield (dry wt) > 305 l°/kg > 80.5 %
for the lager malt to a strong burnt acrid Corn size > 2.5 mm 95% 95%
taste for black malt and roasted barley. Colour 2- 4 EBC 2 – 4 EBC
• The mouthfeel and texture of the beer Total Nitrogen 1.6 – 1.8% 1.6 – 1.8 %
Total Soluble Nitrogen 0.57 – 0.66% 0.65 – 0.75%
comes mainly from the residual
FAN > 160 mg/l > 160 mg/l
unfermentable sugars (dextrins) derived
SNR Soluble nitrogen ratio 34 – 40 % 38 – 44 %
from the malt. Coarse/Fine difference 3 – 7 l°/kg 1 – 2%
• The pH of wort and beer is regulated Friability meter reading > 85% > 85%
through the precipitation of malt Homogeneity > 96% > 96 %
components with mineral ions from the Diastatic Power > 65° IoB > 220 Windisch-Kolbach
water. Wort viscosity mPas @ 20°C 1.55 -1.65 1.55 – 1.65
• Beer foam is made up from hydrophobic DMS precursor 2 – 8 mg/kg 2 – 8 mg/kg
proteins, which have their origins in the Beta glucan mg/l < 200 < 250
Alpha Amylase du (dextrin units) > 30 > 30
malt.
• Other protein fractions are involved in
beer haze and have to be removed to
achieve long term colloid stability in small converted to DMS by heating. contribution but are thought to be
pack beers. The levels of DMS precursor can be carcinogenic.
• Malt also has an effect on beer flavour reduced during malting by: Volatile nitrosamine in malt is produced
through certain flavour active compounds. as oxides of nitrogen (NOx) react with
• Reduced proteolysis and rootlet growth naturally occurring malt amines during
Most of these factors other than colour, are during germination kilning to produce N-nitrosodimethylamine,
not included in the malt specification. • Poorly modified malts have lower SMM usually abbreviated to NDMA. NOx may be
However there is one flavour active • Higher kilning temperatures reduce SMM. present either in the hot gases from
compound formed during malting which combusted fuel where direct drying is used
has to be controlled in the finished beer. The brewer will often set a maximum or even from general air pollution in
DMS or Dimethyl Sulphide is a malt specification for SMM to reduce the beer indirectly fired kilns.
derived flavour compound with the flavour DMS. However in some beer brands DMS is The most active forms of NOx are N2O3
of “cooked sweetcorn” often associated seen as a positive flavour and high SMM and N2O4. To avoid the formation of these
with lagers. It has a flavour threshold of levels are encouraged by short, low compounds most maltsters use indirect
around 35 ppb. It is only noticeable in lightly temperature kilning conditions. heat to fire the kilns, low NOx burners or
kilned malts (lager) and is derived from a Nitrosamines are chemical compounds burn sulphur. Although there is no legal limit
precursor, S-methyl methionine (SMM) containing the grouping N-NO and may be for NDMA in the UK there is an industry
produced during germination which is found in malt. They do not have a flavour agreed standard of < 5 ppb. ■

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