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Digital Re-print -May | June 2014

Harvest conditions: Effects on wheat quality

and routes to addressing issues of agronomic,

processing and fnancial

www.gfmt.co.uk

Grain & Feed Milling Technology is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies,the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis ofinformation published.Copyright 2014 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any formor by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872
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F

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

quality.

Some quality issues will render wheatunsuitable 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

for processing.

The role of the growerGrowers 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 farmers 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 varietyendows resistance to disease and premature

germination whilst also defining grain shape,

specific weight, resistance to variations in

harvest conditions and the ability to store

protein efficiently.

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

biscuit processing.

The role of the millerThe 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

acceptable limits.

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 varietiesdemonstrated as suitable for processing(Source: nabim Wheat Guide 2013 www.nabim.org.uk)

Group 1 These varieties performconsistently in milling andbaking.

Group 2 These varieties exhibit bread-making potential, but not of theconsistent high performanceof those in Group 1. Somespeciality varieties may beincluded.

Group 3 These varieties are suitable forbiscuit, cake and other soft-milling, low protein applications.

Group 4 These varieties do not meetthe processing quality criteriadescribed for Groups 1-3.

Harvest conditions:Effects on wheat quality and routes

to addressing issues of agronomic,processing and financial

by Mervin Poole, Analytical Service, Cereals andIngredients Processing Department, Campden BRI, UK

46 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF


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tions by insects or mites. Enzymes produced

by insects to digest wheat proteins render

the protein unsuitable for some baking

applications

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 hightemperatures. Heat above approximately

40C damages the proteins in wheat making

them less capable of producing a functional

gluten network

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

expected

Moisture, protein and otherfactors

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

by consumers.

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 allsuggest safety and quality failures

Protein content poor bread volume and texture >13% on adry matter

basis

Moisture content Unsafe for storage, costly to dry, 76kg/hl

-Amylase content(Hagbergs falling

number)

Too much sugar released from the starch during baking.Dark, sticky breadcrumb with large holes.

>250s

May - June 2014 | 47GRAIN&FEED MILLING TECHNOLOGY F
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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 damagefrom 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

ratios.

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

(www.hgca.com).

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

Table 3.

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 theintake 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

crop.

The 2013 harvest in the UK

Dry conditions prevailed during the 2013

UK harvest.

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

concern.

Low specific weight in 2013 appears to

be due to a proportion of small or shrivelled

grains.

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 wheatmeeting 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

loaf volume.

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

to continue.

About the author:

Mervin Poole manages the analytical

service of the Cereals and IngredientsProcessing 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 UKs 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-

cess innovation.

Contact Mervin on: mervin.poole@

campdenBbri.co.uk or telephone: +44

1386 842287

Table 3: Proportions of wheat samples surveyed from the 2011-13 UK bread making crops thatmet the mill intake criteria limits for specific weight, protein content and Falling Number (sourcedata from: www.hgca.com)

% of samples tested that metintake requirement of:

Group 1 Group 2

2011 2012 2013 2011 2012 2013

Specific weight (>76kg/hl) 91 10 25 86 8 73Protein (>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 bythe baker and therefore

demands control over

wheat quality. A contract

of trade defines the quality

measurements and sets

acceptable limits"

48 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF


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