or the 2013 crop of UK wheat, the
weather during planting was poor
hence, farmers sowed more spring
wheat, but because the weather improved,
the final crop quality was average.
The aim of the miller is to maintain the
production of flour that performs consist-
ently in processing.
Hence, the miller tests wheat quality to
maintain the quality of the raw materials
entering the mill.
Quality means different things for dif-
ferent products and therefore a number of
factors are important when assessing wheat
Some quality issues will render wheat
unsuitable for human or even animal con-
sumption. Wet wheat is unsuitable for safe
storage and can lead to fungal-based spoilage
or premature germination.
Wheat contaminated by the addition of
foreign material, ergot or chemicals leads to
food safety risks. Partially germinated grains,
those of low density, of unsuitable varieties
or low protein content may be unsuitable
The role of the grower
Growers play a key role in producing high
quality wheat. They begin influencing wheat
quality by selecting appropriate varieties
for the soil type and climate. The planting
season defines the varieties sown.
During the lifecycle of the plant, the
farmer monitors plant health. They use this
information to treat the crop with nutrients
such as nitrogen and sulphur and chemicals
such as herbicides and pesticides to encour-
age healthy plant growth.
The weather influences plant growth and
the opportunities to plant seeds and apply
treatments can limit the farmer’s control of
wheat quality. After harvest, the safe storage
of wheat before trade to the miller is essen-
tial. For further information see, The Home
Grown Cereals Authority (HGCA) “Grain
Storage Guide for Cereals and Oilseeds,”
which applies food safety approaches to the
storage of cereals (www.hgca.com).
The variety of wheat largely defines
the quality of subsequent products, for
example, flour. The genetics of a variety
endows resistance to disease and premature
germination whilst also defining grain shape,
specific weight, resistance to variations in
harvest conditions and the ability to store
To support the farmers in selecting
appropriate varieties in the UK, the National
Association of British and Irish Millers (nabim)
publish a categorisation of wheat varieties,
summarised in Table 1, based on at least
three years of trial data. The trials consider
the suitability of the wheat for bread and
The role of the miller
The miller is responsible for supplying
consistent flour of the quality required by
the baker and therefore demands control
over wheat quality. A contract of trade
defines the quality measurements and sets
These tests include rapid tests by mill
intake laboratories that enable the efficient
unloading of wheat.
However, where quality raises concerns,
further testing may be required.
The miller uses rapid tests, summarised
in Table 2, to measure the quality of traded
wheat at the mill. These include a visual
inspection to determine the suitability of the
wheat for milling and may result in rejection:
Damaged grains could indicate infesta-
Table 1: Categorisation of wheat varieties,
published by nabim to communicate
their preference for UK wheat varieties
demonstrated as suitable for processing
(Source: nabim Wheat Guide 2013 www.
Group 1 These varieties perform
consistently in milling and
Group 2 These varieties exhibit bread-
making potential, but not of the
consistent high performance
of those in Group 1. Some
speciality varieties may be
Group 3 These varieties are suitable for
biscuit, cake and other soft-
milling, low protein applications.
Group 4 These varieties do not meet
the processing quality criteria
described for Groups 1-3.
Effects on wheat quality and routes
to addressing issues of agronomic,
processing and financial
by Mervin Poole, Analytical Service, Cereals and
Ingredients Processing Department, Campden BRI, UK
46 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF
tions by insects or mites. Enzymes produced
by insects to digest wheat proteins render
the protein unsuitable for some baking
Odours, taints, shrivelled, pink or green
grains may suggest contamination by mould
or chemicals, which indicates a risk of poi-
sonous mycotoxins or dangerous chemicals
entering the food chain
Ergot is a fungus from the genus Claviceps.
The fruiting bodies are dark coloured fun-
gal spores known as sclerotia that contain
poisonous alkaloids. They have a creamy
white centre of similar size and density to
a wheat grain and are therefore difficult to
separate from wheat. The risk to human
and animal health excludes wheat from the
food chain if it contains these poisonous
sclerotia. Furthermore, the EU Commission
Regulations (Numbers 1234/2007 and
1272/2009) have set maximum levels per-
mitted under EU regulations of 500mg/kg of
sclerotia in wheat
Dark coloured grains can indicate heat-
damage due to drying the wheat at high
temperatures. Heat above approximately
40˚C damages the proteins in wheat making
them less capable of producing a functional
Skilled intake technicians may recognise
varieties by visual examination. A passport
scheme supports the traceability of wheat
and states its variety. As a significant propor-
tion of quality is fixed by variety, this is a key
indicator of quality and further testing may
be required if the sample does appear as
Moisture, protein and other
Independent to the visual inspection, the
miller measures moisture because wheat
cannot be stored safely above 14.5 percent
moisture on a mass basis.
Drying grain is expensive and grain is
traded based on weight.
Therefore, the miller does not wish to
pay for either the cost of drying or the extra
weight of the water included with the grain.
The miller measures protein content
because specific products need appropriate
flour protein for their manufacture. The
acceptable threshold for bread wheat is 13.0
percent. Below 13.0 percent wheat protein,
the derived flour is incapable of maintaining
the consistent bread loaf-volumes expected
Premature germination of wheat due to
variety, moisture and heat in either the field
or following storage causes the production
of an enzyme, which breaks down stored
starch to sugar. The miller measures the
quantity of this enzyme by the Hagberg
Falling Number test.
Low Falling Number values indicate
excess enzyme. The threshold for bread
wheat is a minimum of 250s. Below this level,
the enzyme releases too much sugar, which
feeds the yeast causing uncontrolled holes or
Table 2: Tests used to assess wheat quality in a mill intake laboratory
Test Considerations and impact Limits
Sensory evaluation Infestation, odours, taints, heat-damage and variety all
suggest safety and quality failures
Protein content poor bread volume and texture >13% on a
Moisture content Unsafe for storage, costly to dry, <14.5%
(Hectolitre weight or
Low density equates to lower flour yields during milling
and below 76kg/hl indicates grain quality problems
Too much sugar released from the starch during baking.
Dark, sticky breadcrumb with large holes.
May - June 2014 | 47GRAIN&FEED MILLING TECHNOLOGY F
darkening of the breadcrumb structure.
Both of these contribute to undesir-
able bread, which does not meet consumer
expectations. Excess enzyme can also lead
to stickiness of the dough and crumb causing
dough processing and bread slicing failures.
The miller measures the density of the
wheat. Known as the Hectolitre or Bushel
Weight tests, the results help identify shrunk-
en grain due to disease, drought or damage
from insect infestations.
The acceptable threshold for bread
wheat is 76kg/hl.
Higher levels are associated with higher
flour yields from the wheat because plump
grains have lower surface bran to endosperm
The conclusions of these tests will influ-
ence the suitability of the wheat for process-
ing into flour and its sale to a baker. The
results will conclude the trade agreements
for the wheat and define the payment the
farmer receives for their crop.
Farmers are dependent on weather
throughout the lifecycle of the plant to
produce good quality wheat.
Late summer, autumn and winter of
2012 were very wet and prevented the
sowing and establishment of wheat in the
UK because the land was too wet to work.
In response, the farmers selected more
spring wheat varieties and sowed these in
the spring of 2013. Opportunities for good
plant husbandry during the life cycle of the
plant improved following a cold spring. The
warm and dry summer increased plant
growth rates. The farmers harvested the
crops under dry conditions.
After harvest, they stored the wheat
under controlled conditions to maintain
quality. The summer and harvest conditions
in 2013 helped the crop to recover from
expectations of a disastrous harvest. The
final quality assessments suggest the quality
of the harvest was average.
Based on HGCA estimates, the total
UK wheat yield decreased from 15.2mt in
2011, to 13.3mt in 2012 and 11.9mt in 2013
Nabim classify Group 1 and Group 2 vari-
eties as potentially suitable for bread making.
The basic intake requirements used to assess
quality include; a specific weight of greater
than 76kg/hl, a protein content of greater
than 13.0 percent and Falling Number values
greater than 250s.
The proportions of samples meeting
these criteria when surveyed after the 2011,
2012 and 2013 harvests are summarised in
We made a comparison of the 2013
and 2011 crops. We did not compare the
2012 crop because it was abnormal and the
quality was not a reflection of average crop
performance in the UK.
Of the nabim Group 1 and 2 varieties
harvested in 2013 more samples met the
intake requirements for falling number than
2011 but fewer met the requirements for
protein or specific weight.
The farmers concentrate on producing
good quality wheat throughout the lifecycle
of the plant. For the millers, the commercial
incentives to use locally available wheat out-
weigh the cost of importing wheat.
However, the negative effect of any
food safety scare outweighs any commercial
incentive to use the most readily available
The 2013 harvest in the UK
Dry conditions prevailed during the 2013
The dry conditions helped avoid prema-
ture germination and enabled safe storage
of the crop. The Falling Number values of
>250s in more than 90 percent of bread-
making samples meant that excess sugars
in baking were unlikely to be common. The
bakers can easily compensate for low levels
of enzyme in the bakery and therefore the
low level of enzyme is unlikely to cause
Low specific weight in 2013 appears to
be due to a proportion of small or shrivelled
It is of concern because it is predomi-
nantly evident in the survey of Group 1
varieties. The root cause of such shrivelled
grains is important because drought, pre-
mature harvesting or disease can define the
risk of using these samples in the food chain.
Small grains due to drought or premature
harvesting will result in a low flour yield and
potential bran contamination without care-
ful and costly mill adjustment. Small grains
due to disease are associated with higher
mycotoxin risks associated with mycotoxin
producing fungi such as the Fusarium species.
Mycotoxin contaminated samples are
excluded from the food chain when safe lim-
its are exceeded. However, specialist equip-
ment is available that can separate samples
based on their density to recover the plump
grains. This expensive process will recover a
proportion of plump grains from the sample.
Grain sorters, which rely on image tech-
nology, remove individual grains contami-
nated by Fusarium.
However, not all Fusarium species pro-
duce mycotoxins. Hence, the removal of all
Fusarium contaminated grains by grain sort-
ers is both wasteful and expensive.
With only 28 percent of Group 2 wheat
meeting the grain intake specifications in
2013, low protein is a potential problem.
The main impacts of low protein bread
wheat are low and inconsistent loaf volumes.
The baker can add gluten to improve the
However, this is expensive because glu-
ten is manufactured from wheat.
A remaining option is to import wheat
of the appropriate quality. This incurs higher
transport costs. However, this option may
be associated with lower risks and process-
ing costs, causing it to be a realistic option.
In conclusion, the harvest conditions have
lead to a small, average quality UK crop in
2013. Although the crop was better than
anticipated, the penetration of the quality
is unlikely to compensate for the shortage.
Hence, imports of wheat to meet the
demand for consistent products are likely
About the author:
Mervin Poole manages the analytical
service of the Cereals and Ingredients
Processing department at Campden
BRI. The service supports innovation
and training at Campden BRI by provid-
ing testing to the cereals, ingredients
and animal feed industries.
Campden BRI is the UK’s larg-
est independent membership-based
organisation carrying out research and
development for the food and drinks
industry worldwide. It is committed to
providing industry with the research,
technical and advisory services needed
to ensure product safety and quality,
process efficiency and product and pro-
Contact Mervin on: mervin.poole@
campdenBbri.co.uk or telephone: +44
Table 3: Proportions of wheat samples surveyed from the 2011-13 UK bread making crops that
met the mill intake criteria limits for specific weight, protein content and Falling Number (source
data from: www.hgca.com)
% of samples tested that met
intake requirement of:
Group 1 Group 2
2011 2012 2013 2011 2012 2013
Specific weight (>76kg/hl) 91 10 25 86 8 73
Protein (>13%) 50 50 50 37 60 28
Falling number (>250s) 86 56 93 84 38 90
"The miller is responsible for
supplying consistent flour
of the quality required by
the baker and therefore
demands control over
wheat quality. A contract
of trade defines the quality
measurements and sets
48 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF
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