Cereals and cereal products — Sampling studies

This document presents the description and the results of the three studies conducted by United Kingdom, France and Germany related to grain sampling in order to define a harmonized sampling protocol for official controls. These results had been used to draft ISO 24333.

Céréales et produits céréaliers — Études sur l'échantillonnage

Le présent document détaille et expose les résultats des trois études sur l’échantillonnage des céréales menées par le Royaume-Uni, la France et l’Allemagne, dans le but de définir un protocole d’échantillonnage harmonisé pour les contrôles officiels. Ces résultats ont été utilisés pour élaborer l’ISO 24333.

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Publication Date
13-Jul-2021
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6060 - International Standard published
Start Date
14-Jul-2021
Completion Date
14-Jul-2021
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TECHNICAL ISO/TR
REPORT 29263
First edition
2021-07
Cereals and cereal products —
Sampling studies
Céréales et produits céréaliers — Études sur l'échantillonnage
Reference number
ISO/TR 29263:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TR 29263:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO 2021 – All rights reserved
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ISO/TR 29263:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Context ............................................................................................................................................................................................................................ 1

5 Study n°1: extract from "Grain sampling and assessment: sampling grain in lorries"

– Project report n° 339” ................................................................................................................................................................................. 1

5.1 General ........................................................................................................................................................................................................... 1

5.2 Context ........................................................................................................................................................................................................... 1

5.3 Studies conducted and objectives........................................................................................................................................... 3

5.4 Methodology ............................................................................................................................................................................................. 3

5.4.1 Conducting tests ............................................................................................................................................................... 3

5.4.2 Results and conclusions .................. ......................................................................................................................... .. 5

6 Study n°2: extract from "Sampling grain in static and flowing condition –

alternatives to the regulatory protocol" ...................................................................................................................................19

6.1 General ........................................................................................................................................................................................................19

6.2 Context ........................................................................................................................................................................................................20

6.2.1 Regulatory aspect .........................................................................................................................................................20

6.2.2 Normative aspect ..........................................................................................................................................................20

6.3 Studies conducted and objectives........................................................................................................................................20

6.3.1 Study A ...................................................................................................................................................................................20

6.3.2 Study B ...................................................................................................................................................................................21

6.4 Study A: silos and lorries of wheat and corn – Fusariotoxins and quality assessment .........21

6.4.1 Organising field tests .................................................................................................................................................21

6.4.2 Results and conclusions .................. ........................................................................................................................33

6.5 Study B : silos of corn – Fusariotoxins; flowing grains ......................................................................................48

6.5.1 Organising field tests .................................................................................................................................................48

6.5.2 Results and conclusions .................. ........................................................................................................................49

7 Study n°3: extract from "Investigation of the distribution of deoxynivalenol and

ochratoxin a contamination within a 26-T truckload of wheat kernels" – Project report ....90

7.1 Context ........................................................................................................................................................................................................91

7.2 Methodology ..........................................................................................................................................................................................91

7.2.1 Instruments for sampling and sample homogenization process ........................................91

7.2.2 Reagents and materials ...........................................................................................................................................91

7.2.3 Sampling procedure ...................................................................................................................................................92

7.2.4 Sample comminution ................................................................................................................................................93

7.3 Results and Discussion ..................................................................................................................................................................93

7.3.1 Distribution of DON and OTA infected kernels within the lot ................................................93

7.3.2 Sample comminution study for the dry milling process.............................................................95

7.4 Uncertainty comparison on the basis of number of incremental samples ......................................95

7.5 Conclusions .............................................................................................................................................................................................97

Bibliography .............................................................................................................................................................................................................................98

© ISO 2021 – All rights reserved iii
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ISO/TR 29263:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4,

Cereals and pulses, in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 338, Cereal and cereal products, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
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ISO/TR 29263:2021(E)
Introduction

This document presents the results of three groups of studies which results have been used to elaborate

ISO 24333

These studies have been managed by United Kingdom in May 2003, by France in 2004-2005 for the first

one and 2006-2007 for the second one and Germany in 2008.
© ISO 2021 – All rights reserved v
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TECHNICAL REPORT ISO/TR 29263:2021(E)
Cereals and cereal products — Sampling studies
1 Scope

This document presents the description and the results of the three studies conducted by United

Kingdom, France and Germany related to grain sampling in order to define a harmonized sampling

protocol for official controls.
These results had been used to draft ISO 24333.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Context

European directives for official controls of some contaminants such as mycotoxins required methods

for sampling and analysis. In order to harmonize sampling procedures necessary for these analysis and

to determine the best way to prepare a homogenous and representative laboratory sample, studies had

been conducted by United Kingdom, France and Germany.
The results of these 3 studies are presented in this report.
5 Study n°1: extract from "Grain sampling and assessment: sampling grain in
lorries" – Project report n° 339”
5.1 General
By J. KNIGHT, R. WILKIN and J. RIVETT

Department of Environmental Science and Technology, Renewable Resources Assessment Group,

Imperial College of Science and Technology, Prince Consort Road, London SW7 2BB

This is the final report of a 13-month project that started in May 2003. The work was funded by HGCA

(project 2955).
5.2 Context

This two-year programme was made at the request of HGCA to improve and standardise grain sampling

and analysis across the UK cereals industry.
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ISO/TR 29263:2021(E)

The first phase of the programme was to develop and validate protocols suitable for collecting samples

of grain on UK farms at harvest time and to train farmers in their use. The second part was to examine

approaches to the collection of samples during storage and to compare the results obtained, wherever

possible, with data collected as the store was filled. During the course of earlier sampling work, there

was strong interest expressed in the mechanics and effectiveness of sampling loads of grain in lorries.

In addition, some of the work done during storage involved sampling grain as it left the store in lorries.

This showed up the limitations of some approaches to lorry sampling and highlighted the need for more

information. An assessment of lorry sampling was therefore, added and is reported here.

Almost all grain is sampled as it is delivered to end users to confirm its quality and to ensure that

contractual obligations are met. This sampling takes the form of collecting one or more samples from a

lorry-load on arrival. The equipment used and method of sampling varies between end users and there

are no data to show if these variations may cause bias in the representativeness of the sample and,

therefore, in the results of quality analysis.

The key aim of end-user sampling is to ensure that the quality of the grain is suitable for its intended

use. Therefore, sampling is done before the load is tipped and this limits access to the surface of the

load. This access is further constrained by food safety and HSE legislation that prevent the sampler

from walking on the load.

A limited assessment of the practicalities of sampling lorries was done in 1992 (HGCA Project

Report 79) in which the effects of method of sampling, number and position of sample points, the

methods of loading lorries were considered. The wheat sampled was low-grade feed material with a low

specific weight and a high level of fine material so was not representative of other grades. The results

suggested that loading lorries with a front loader or from a hopper had no effect on the distribution of

the quality characteristics within a load. Small differences were noted in the mean values for specific

weight between automatic sampling using a Samplex CS90 and a manual spear but overall variability

of the grain meant that these differences were not significant. There was significant variability in the

results obtained at individual points with either method, although this variability was random and not

associated with any part of the load. Fine material appeared to be very difficult to measure. At the time,

this work was undertaken there were no restrictions limiting access to the surface of the grain so that a

widely disbursed pattern of sampling points could be used with the manual sampling. The conclusions

from this work were that it was extremely unwise to base an assessment of lorry load of grain on a

single sample and that more work was needed to confirm the results and to assesses other grades of

grain. The aim of this project was to establish if there are any inherent problems with the sampling of

grain for the determination of quality characteristics in lorries at the point of intake and to establish

recommendations in the form of a protocol for the sampling of grain under these conditions.

Grain was sampled using automated systems (Samplex CS90) and manual spearing to see if the method

of sampling influenced the grain quality measurements. A key part of the process was to assess the

influence that the number of samples taken from each load had on the likely accuracy of the results.

Samples were collected at 4 different locations; on two occasions 10 lorries were sampled and on two

occasions 8 lorries were sampled. At three locations, CS90 samplers were used and 8 samples were

withdrawn from each load and at the other location samples were taken manually with a multi-

compartmented spear with 5 samples being taken from each lorry. A comparison of different ways

of sample handling was obtained by comparing the individual results from the 8 samples against an

analysis of samples withdrawn from a composite sample formed from 8 samples. The latter method

reflects more accurately the procedure followed at most stores.

Results indicated that there were no statistically significant differences between results from the

individual samples or from the composite samples. Monte Carlo simulation of the impacts of using 2, 3, 5

or 8 samples per load revealed that the greater the number of samples used the greater the reliability of

the result and the more likely it was to represent the true mean of the load. It was noted that automatic

sampling equipment can no longer sample the entire length of a trailer and this could cause problems

with obtaining the ideal sample. Manual sampling also had severe limitations due to the lack of safe

access for sampling of trailers.

A sampling protocol for lorries is presented which emphasises the need for 8 samples to be taken from

each load in order to get a good representation of the quality of the entire load.

2 © ISO 2021 – All rights reserved
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ISO/TR 29263:2021(E)
5.3 Studies conducted and objectives

The study was conducted to assess the effectiveness of different approaches to sampling loads of grain

in lorries.
The specific objectives were:

— To assess if the method of collecting samples influences grain quality measurement;

— To assess if the number and position of sampling points influences grain quality measurement;

— To provide guidelines for sampling lorries giving reliable information about grain quality.

5.4 Methodology
5.4.1 Conducting tests
5.4.1.1 Collection of data relating to current sampling practice

In November 2002 the HGCA circulated a questionnaire to commercial grain stores and end-users of

grain requesting information about their methods of analysis and methods of intake sampling. The

information that was collected was used to assist with the design of the assessment of lorry sampling.

5.4.1.2 Sample collection
5.4.1.2.1 Store 1

The work was done at a store specialising in the storage of malting barley. Lorries were loaded with

malting barley, variety Pearl, of a quality representative of that delivered to central storage from farms.

The lorries, all 28 t articulated units, were loaded with a front loader fitted with a 2 t bucket.

Ten loads were sampled over a 2-day period. Sampling was done using the store’s Samplex CS90

automated vacuum sampler. Initially, it had been expected to re-programme the CS90 to take 10

samples/load in a pre-set pattern. However, observation of the method of operation and sampling

pattern achieved by the CS90 suggested that there was no advantage in using more than the 8 points

provided by one of the standard sampler programmes.

During the setting up and initial testing of the CS90, the slide on the sample spear was opened to its

maximum to increase the sample size. The system was set to collect grain only during the withdrawal

as is recommended by the manufacturer for granular materials.

Each of the eight points was sampled three times. On the first occasion, individual samples were held

separately. During the second and third samplings, all samples were bulked into single batches. One of

these bulk samples was held as a composite sample and the other was used to provide samples of 1, 2

and 3 litres (small medium and large) collected at random with a 1-litre jug.

A small sub-sample from each of the individual samples was tested on the spot by store staff for

screenings and germinative capacity. Screenings were tested by sieving a 100 g sub-sample with

a motorised shaker fitted with a 2,25 mm mesh screen for 2 minutes. The germinative capacity was

tested using the standard tetrazolium test.
5.4.1.2.2 Store 2

Work was done at a commercial store during the normal out-loading of feed wheat. The lorries were

loaded from an on-floor bulk using a front-bucket loader and were sampled as they left the store. Normal

sampling practice was to collect a single spear sample/load using a manual, multi-compartmented

spear of about 1,7 m in length. Access to the load was via a small sampling platform that only allowed

samples to be taken from less than half the length of the loaded trailer and from only one side of the

load.
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ISO/TR 29263:2021(E)

For the purposes of this investigation, 5 sample points were used for each load and the lorry was moved

forward during the sampling process so that access to the whole length of the load could be obtained.

However, it was not practical to turn the lorry round to give access to both sides of the load. Manual

sampling meant that there was, inevitably, some variation in the exact location of the sample points

between loads. Three spear samples were collected at each point. The first was held as an individual

sample, the second bulked to form a composite sample and the third bulked to give a sample from which

three random samples (small, medium and large) could be taken without mixing.
Ten lorry loads were sampled over a two-day period.
5.4.1.2.3 Store 3

The assessments were made at a commercial store during the normal out-loading of milling wheat.

Samples were collected using a Samplex CS90 but without the automatic option. Therefore, the spear

had to be controlled manually by the operator and this meant that there was considerable variation in

the positioning of sample points between loads. A further constraint on sampling was that the CS90

was positioned at one end of the weighbridge thus limiting access to just one-half of the load. The slide

on the sampler was fully open and grain was collected only as the spear withdrew.

The lorries were loaded using a bucket loader from a 2 000 t batch of wheat stored on-floor. Only a

limited number of loads were dispatched each day and time constraints meant that only 8 loads were

sampled during this assessment.

Three samples were collected from 8 sample points in each load. The first was held as an individual

sample, the second bulked to form a composite sample and the third bulked to give a sample from

which three random samples (small, medium and large) could be taken without mixing. The 8 points

were arranged in a 3, 2, 3 pattern with the two samples being taken from the centre line and each row

of 3 taken down the sides of the load (see Figure 1). The location of the sampler and the position of the

lorry on the weighbridge meant that the samples always came from the front half of the load.

Figure 1 — Arrangement of sampling points used by CS90 sampler

Data was supplied by the storekeeper giving the store’s own assessment of the quality of the batch of

grain as measured when the store was filled.
5.4.1.2.4 Store 4

Loads of milling wheat delivered to a large flour mill were sampled with a Samplex automatic CS90.

This work was done some months after the earlier assessments and it was decided that the collection of

extra samples to make up composite batches was not justified. Eight samples were collected from eight

loads of wheat over a 10 d period. For technical reasons, the collection of samples had to be done by mill

staff so the exact details of the points sampled are not known.
5.4.1.3 Assessment of samples

Samples had to be transported to the testing laboratory and some additional delays occurred between

the collection and assessment of samples. However, samples that could not be analysed within 48 h

were stored in a freezer at -16 °C to minimise changes in the properties of the grain. These samples

were allowed to return to ambient temperature before testing. The exceptions to this were samples

collected from store 4.
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ISO/TR 29263:2021(E)

These were collected over a 10 d period and a further 4 d elapsed before the samples arrived for testing.

During this period, the samples were not held under controlled temperature conditions.

Individual samples were tested separately, as were the three different sizes of random sample. However,

in the case of the medium and large samples, these were divided by coning and quartering to give the

correct volume of grain for assessment. The composite samples were also mixed and then divided by

coning and quartering. Five sub-samples of the composites were tested from Store1 but only three sub-

samples were tested from stores 2 and 3.

As a first step in the assessment process, the screenings in each sample were measured by manual

sieving. Each sample was weighed and then sieved for 30 s using a 2,5 mm slotted sieve for wheat or a

2,25 mm slotted sieve for barley. The sievings were weighed and the percentage calculated. The weights

of the individual samples gave an indication of the variation in the size of sample collected on each

occasion.

After sieving, the properties of each sample were assessed using a Foss Infratec Grain Analyser 1241

GA-TWM . The machine used official calibrations as provided by the NIR network and measured

moisture content, specific mass, protein in the case of wheat, or nitrogen in the case of barley and made

an assessment of hardness of wheat.

In addition, some of the samples of wheat from stores 2 and 3 were sent to NIAB for assessment of

Hagberg Falling Number. Complete sets of individual samples from 5 loads, together with a single

composite sample were tested from Store 3. Complete sets of individual samples and a single composite

from 4 loads were tested from Store 2. The testing was done using standard methodology and each

result was the mean of two determinations.
5.4.1.4 Estimating the reliability of sampling

The impact of the number of samples taken on the reliability of the result obtained from those samples

was assessed by determining the mean and standard deviation for the results of the 8 samples taken

from each lorry. This information was used to define a probability curve for a normal distribution for

each of the lorries. A Monte Carlo simulation was then run to sample from either 2, 3, 5 or 8 of these

distributions depending on the sampling regime to be simulated. The simulation was run for a total of

100 000 trials. From this result, cumulative probability distribution curves were obtained and these

were used to estimate the confidence limits for different numbers of samples for a given margin of

error. Thus, the confidence interval for sampling 2, 3, 5, or 8 times for a known deviation from the mean

for the different quality parameters could be produced. The final figure shows the probability of the

confidence interval actually covering the mean value.
5.4.2 Results and conclusions
5.4.2.1 Sample analysis results
5.4.2.1.1 Collection of data relating to current sampling practice

As part of the initiative to standardise grain testing a survey of laboratory practice was undertaken

and this included a set of questions on the collection of samples from lorry-loads of grain. This provided

information from a range of commercial premises receiving, handling or processing grain about current

lorry sampling practices. The response showed that there was no common industry-wide approach.

The most frequently used equipment was the Samplex CS90 or other unspecified Samplex units (49 %)

followed by manual sampling (37 %). The number of samples collected per load ranged between 1 and

10 and the mass of grain collected varied between 0,4 kg and 11 kg.

1) Foss Infratec Grain Analyser 1241 GA-TWM is an example of a suitable product available commercially. This

information is given for the convenience of users of this document and does not constitute an endorsement by ISO

of thisproduct.
© ISO 2021 – All rights reserved 5
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ISO/TR 29263:2021(E)
5.4.2.1.2 Observations on the sampling
5.4.2.1.2.1 Store 1

During the assessment, it became apparent that the reach of the CS90 sampling arm and the size of

current articulated trailers resulted in parts of the load being inaccessible unless the lorry was moved.

Of the total 11 m length
...

RAPPORT ISO/TR
TECHNIQUE 29263
Première édition
2021-07
Céréales et produits céréaliers —
Études sur l'échantillonnage
Cereals and cereal products — Sampling studies
Numéro de référence
ISO/TR 29263:2021(F)
ISO 2021
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ISO/TR 29263:2021(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2021

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y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

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ii © ISO 2021 – Tous droits réservés
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ISO/TR 29263:2021(F)
Sommaire Page

Avant-propos ..............................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes et définitions ....................................................................................................................................................................................... 1

4 Contexte ......................................................................................................................................................................................................................... 1

5 Étude n°1: extrait de «Grain sampling and assessment: sampling grain in lorries –

Project report n° 339 » ................................................................................................................................................................................... 1

5.1 Généralités .................................................................................................................................................................................................. 1

5.2 Contexte ........................................................................................................................................................................................................ 2

5.3 Études réalisées et objectifs ........................................................................................................................................................ 3

5.4 Méthodologie ............................................................................................................................................................................................ 3

5.4.1 Conduite des essais ........................................................................................................................................................ 3

5.4.2 Résultats et conclusions ............................................................................................................................................ 6

6 Étude n° 2: extrait de «Sampling grain in static and flowing condition – alternatives

to the regulatory protocol » ...................................................................................................................................................................21

6.1 Généralités ...............................................................................................................................................................................................21

6.2 Contexte .....................................................................................................................................................................................................21

6.2.1 Aspects réglementaires ...........................................................................................................................................21

6.2.2 Aspects normatifs ........................................................................................................................................................21

6.3 Études réalisées et objectifs .....................................................................................................................................................22

6.3.1 Étude A ..................................................................................................................................................................................22

6.3.2 Étude B ..................................................................................................................................................................................22

6.4 Étude A: silos et camions de blé et de maïs – évaluation des fusariotoxines et de la

qualité ..........................................................................................................................................................................................................23

6.4.1 Organisation des essais de terrain ................................................................................................................23

6.4.2 Résultats et conclusions .........................................................................................................................................37

6.5 Étude B: silos de maïs – Fusariotoxines; céréales en mouvement ..........................................................54

6.5.1 Organisation des essais de terrain ................................................................................................................54

6.5.2 Résultats et conclusions .........................................................................................................................................57

7 Étude n° 3: extrait de l’« Investigation of the distribution of deoxynivalenol and

ochratoxin a contamination within a 26-T truckload of wheat kernels – Project report » ..99

7.1 Contexte .....................................................................................................................................................................................................99

7.2 Méthodologie .........................................................................................................................................................................................99

7.2.1 Instruments d’échantillonnage et procédé d’homogénéisation des échantillons 99

7.2.2 Réactifs et matériaux ..............................................................................................................................................100

7.2.3 Mode opératoire de prélèvement ................................................................................................................100

7.2.4 Préparation des échantillons ..........................................................................................................................101

7.3 Résultats et discussion ...............................................................................................................................................................102

7.3.1 Distribution des grains contaminés par le DON et l’OTA au sein du lot .....................102

7.3.2 Étude de préparation des échantillons pour le procédé de mouture sèche ...........103

7.4 Comparaison des incertitudes en fonction du nombre d’échantillons élémentaires ..........104

7.5 Conclusions ..........................................................................................................................................................................................106

Bibliographie .......................................................................................................................................................................................................................107

© ISO 2021 – Tous droits réservés iii
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ISO/TR 29263:2021(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www

.iso .org/ directives).

L’attention est attirée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www .iso .org/ brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion

de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir le lien suivant: www .iso .org/ iso/ fr/ avant -propos.

Le présent document a été élaboré par le Comité technique ISO/TC 34, Produits alimentaires, sous-

comité SC 4, Céréales et légumineuses, en collaboration avec le Comité européen de normalisation (CEN),

Comité technique CEN/TC 338, Céréales et produits céréaliers, conformément à l’accord de coopération

technique entre l’ISO et le CEN (Accord de Vienne).

Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent

document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l’adresse www .iso .org/ fr/ members .html.
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ISO/TR 29263:2021(F)
Introduction

Le présent document expose les résultats des trois groupes d’études dont les résultats ont été utilisés

pour élaborer l’ISO 24333.

Ces études ont été pilotées par le Royaume-Uni en mai 2003, par la France en 2004-2005 pour la

première étude et en 2006-2007 pour la seconde étude, et enfin par l’Allemagne en 2008.

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RAPPORT TECHNIQUE ISO/TR 29263:2021(F)
Céréales et produits céréaliers — Études sur
l'échantillonnage
1 Domaine d’application

Le présent document détaille et expose les résultats des trois études sur l’échantillonnage des

céréales menées par le Royaume-Uni, la France et l’Allemagne, dans le but de définir un protocole

d’échantillonnage harmonisé pour les contrôles officiels.
Ces résultats ont été utilisés pour élaborer l’ISO 24333.
2 Références normatives
Le présent document ne contient aucune référence normative.
3 Termes et définitions
Aucun terme n’est défini dans le présent document.

L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en

normalisation, consultables aux adresses suivantes:

— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp;

— IEC Electropedia: disponible à l’adresse https:// www .electropedia .org/ .
4 Contexte

Les directives européennes relatives aux contrôles officiels de certains contaminants, tels que les

mycotoxines, prescrivaient des méthodes d’échantillonnage et d’analyse. Des études visant à harmoniser

les modes opératoires d’échantillonnage requis par ces analyses et à déterminer la meilleure façon de

préparer un échantillon de laboratoire homogène et représentatif ont été réalisées par le Royaume-Uni,

la France et l’Allemagne.
Les résultats de ces trois études sont présentés dans le présent rapport.
5 Étude n°1: extrait de «Grain sampling and assessment: sampling grain in
lorries – Project report n° 339 »
5.1 Généralités
De J. KNIGHT, R. WILKIN et J. RIVETT

Department of Environmental Science and Technology, Renewable Resources Assessment Group,

Imperial College of Science and Technology, Prince Consort Road, London SW7 2BB

Ce document constitue le rapport final d’un projet de 13 mois initié en mai 2003. Les travaux ont été

financés par la Home Grown Cereals Authority (HGCA), projet 2955.
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ISO/TR 29263:2021(F)
5.2 Contexte

Ce programme de deux ans a été élaboré à la demande de la HGCA, dans le but d’améliorer et de

normaliser l’échantillonnage et l’analyse des céréales dans l’ensemble du secteur céréalier britannique.

La première phase du programme a consisté à développer et à valider des protocoles adaptés au

prélèvement d’échantillons de céréales dans les exploitations agricoles britanniques au moment

des moissons, et à former les exploitants à ces protocoles. La seconde phase a consisté à examiner

les techniques de recueil d’échantillons pendant le stockage, et à comparer les résultats obtenus,

si possible, aux données recueillies pendant le remplissage de l’entrepôt. Les premières opérations

d’échantillonnage se sont focalisées sur l’aspect mécanique et l’efficacité de l’échantillonnage des

chargements de céréales dans les camions. Une partie du travail réalisé pendant le stockage a également

comporté un échantillonnage des céréales à leur départ de l’entrepôt dans des camions. Ce travail a

permis d’exposer les limites de certaines techniques d’échantillonnage en camion et de souligner la

nécessité de disposer d’informations supplémentaires. Une évaluation de l’échantillonnage en camion a

donc été menée et ses résultats intégrés au présent rapport.

La quasi-totalité des céréales est échantillonnée au moment de la livraison à l’utilisateur final, afin de

vérifier la qualité des grains et de garantir le respect des obligations contractuelles. Cet échantillonnage

consiste à prélever au moins un échantillon dans chaque chargement de camion, à son arrivée sur le

site. Le matériel utilisé et la méthode d’échantillonnage varient d’un utilisateur final à l’autre et aucune

donnée ne permet de montrer si ces variations peuvent entraîner un biais de représentativité de

l’échantillon et, par conséquent, un biais dans l’analyse de la qualité.

Le principal objectif de l’échantillonnage chez l’utilisateur final est de s’assurer que les céréales

présentent la qualité adéquate pour l’usage prévu. Par conséquent, l’échantillonnage est effectué

avant le déchargement des camions, ce qui limite l’accès à la surface du chargement. L’accès est encore

restreint par la législation relative à la sécurité alimentaire, ainsi qu’à l’hygiène et la sécurité au travail,

qui interdit à l’opérateur responsable de l’échantillonnage de marcher sur le chargement.

Une évaluation limitée des modalités pratiques de l’échantillonnage des camions conduite en 1992

(Rapport de projet 79 de la HGCA) a examiné les effets de la méthode d’échantillonnage, du nombre

et de l’emplacement des points de prélèvement et des méthodes de chargement des camions. Le blé

échantillonné, un produit fourrager de basse qualité, présentait une faible masse à l’hectolitre et un taux

élevé de matière fine, ce qui en faisait un produit non représentatif des autres qualités. Les résultats

indiquent que le chargement des camions au moyen d’un chargeur frontal ou d’une trémie n’a aucun effet

sur la distribution des caractéristiques de qualité au sein du chargement. De légères différences des

masses à l’hectolitre moyennes ont été constatées entre un échantillonnage automatique par Samplex

CS90 et un échantillonnage manuel par sonde, mais rapportées à la variabilité globale des céréales, ces

différences ne sont pas significatives. Une variabilité significative des résultats obtenus par l’une ou

l’autre méthode a été constatée entre points d’échantillonnage individuels, bien que cette variabilité

présente un caractère aléatoire et ne soit pas associée à une partie spécifique du chargement. La

matière fine a posé des difficultés de mesurage très importantes. À l’époque à laquelle a été entreprise

l’étude, il n’existait pas de restrictions d’accès à la surface des céréales, ce qui a permis de pratiquer

l’échantillonnage manuel suivant un réseau de points d’échantillonnage fortement dispersés. L’étude a

conclu qu’il était extrêmement risqué de fonder l’évaluation d’un chargement de camion céréalier sur

un seul échantillon, et que des travaux complémentaires s’imposaient pour confirmer les résultats et

évaluer d’autres qualités de céréales. L’objet du projet était d’identifier d’éventuels problèmes inhérents

à l’échantillonnage des céréales dans les camions en vue de déterminer les caractéristiques de qualité

à réception, et de formuler des recommandations sous la forme d’un protocole d’échantillonnage des

céréales dans les conditions décrites.

Les céréales ont été échantillonnées au moyen de systèmes automatisés (Samplex CS90) et par sondage

manuel, afin de déterminer l’influence éventuelle de la méthode d’échantillonnage sur les mesurages

de qualité des céréales. Une étape clé du processus a consisté à évaluer l’effet du nombre d’échantillons

prélevés dans chaque chargement sur la précision probable des résultats. Les échantillons ont été

prélevés en 4 lieux différents; 10 camions ont été échantillonnés en deux occasions, et 8 camions en deux

autres. Dans trois de ces lieux, des échantillonneurs CS90 ont été employés pour prélever 8 échantillons

dans chaque chargement, tandis qu’au quatrième endroit, 5 échantillons ont été prélevés manuellement

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dans chaque camion au moyen d’une sonde compartimentée. Une comparaison des différentes

méthodes de manipulation des échantillons a été réalisée en comparant les résultats individuels des 8

échantillons aux analyses d’échantillons prélevés dans un échantillon composite formé en combinant

8 échantillons. Cette dernière méthode reflète plus exactement le mode opératoire suivi dans la plupart

des entrepôts céréaliers.

Les résultats ont indiqué une absence de différences significatives sur le plan statistique entre les

résultats des échantillons individuels et ceux des échantillons composites. Une simulation de Monte

Carlo de l’impact de l’utilisation de 2, 3, 5 ou 8 échantillons par chargement a révélé que plus le nombre

d’échantillons par chargement est élevé, plus les résultats sont fiables et plus ils sont susceptibles de

représenter la moyenne réelle pour le chargement. L’étude indique que l’équipement d’échantillonnage

automatique ne permet plus d’échantillonner la longueur entière d’une remorque, ce qui peut poser

problème pour obtenir l’échantillon idéal. L’échantillonnage manuel a également présenté des limites

importantes en raison de l’absence d’un accès sécurisé pour effectuer les prélèvements dans les

remorques.

Un protocole d’échantillonnage des camions est proposé, lequel met l’accent sur la nécessité de prélever

8 échantillons par chargement, pour une représentation satisfaisante de la qualité de l’ensemble du

chargement.
5.3 Études réalisées et objectifs

L’étude a été menée dans le but d’évaluer l’efficacité de différentes stratégies d’échantillonnage de

chargements de céréales dans des camions.
Les objectifs spécifiques étaient:

— d’évaluer si la méthode de prélèvement des échantillons a un effet sur le mesurage de la qualité des

grains;

— d’évaluer si le nombre et l’emplacement des points d’échantillonnage ont un effet sur le mesurage de

la qualité des grains;

— d’établir des lignes directrices pour l’échantillonnage dans les camions, en vue d’obtenir des

informations fiables sur la qualité des grains.
5.4 Méthodologie
5.4.1 Conduite des essais
5.4.1.1 Recueil de données relatives aux pratiques d’échantillonnage existantes

En novembre 2002, la HGCA a diffusé un questionnaire auprès d’entrepôts céréaliers commerciaux et

des utilisateurs finaux des céréales, afin de recueillir des informations sur leurs méthodes d’analyse

et de prélèvement d’échantillons. Les données recueillies ont contribué à la conception de la présente

étude d’évaluation de l’échantillonnage des camions.
5.4.1.2 Collecte des échantillons
5.4.1.2.1 Entrepôt 1

Le travail a été mené dans un entrepôt spécialisé dans le stockage de l’orge de brasserie. Des camions

ont été chargés d’orge de brasserie de la variété Pearl, d’une qualité représentative de celle livrée par

les exploitations agricoles aux entrepôts centraux. Les camions, des semi-remorques articulés de 28 t,

ont été chargés au moyen d’un chargeur frontal équipé d’un godet de 2 t.

Dix chargements ont été échantillonnés sur une période de deux jours. L’échantillonnage a été réalisé

au moyen d’un échantillonneur automatique à aspiration Samplex CS90. Il était prévu à l’origine de

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ISO/TR 29263:2021(F)

reprogrammer le CS90 pour qu’il prélève 10 échantillons par chargement, suivant un schéma prédéfini.

L’observation du mode opératoire et du schéma d’échantillonnage du CS90 a toutefois indiqué qu’il

n’était pas spécialement avantageux de choisir un nombre de points d’échantillonnage supérieur aux

8 points de l’un des programmes standard de l’échantillonneur.

Lors de la configuration et des essais initiaux du CS90, le volet de fermeture de la sonde d’échantillonnage

a été ouvert au maximum afin d’augmenter la taille des échantillons. Le système a été paramétré de

façon à prélever le grain uniquement lors de la remontée, suivant les recommandations du fabricant

pour les matériaux en granulés.

Trois échantillons ont été prélevés pour chacun des huit points d’échantillonnage. Lors du premier

prélèvement, les échantillons individuels ont été conservés séparément. Lors des deux prélèvements

suivants, tous les échantillons ont été rassemblés pour former un lot unique à chaque fois. L’un de ces

échantillons en vrac a été retenu en tant qu’échantillon composite, l’autre étant utilisé pour former des

échantillons de 1, 2 et 3 litres (petit, moyen, grand) prélevés aléatoirement au moyen d’un pichet d’un

litre.

Un petit sous-échantillon de chacun des échantillons individuels a été soumis à essai sur place par le

personnel de l’entrepôt à des fins de tamisage et de détermination de la faculté germinative. L’analyse

de tamisage a été réalisée en tamisant un sous-échantillon de 100 g pendant 2 minutes sur un tamis

secoueur motorisé équipé d’un tamis de 2,25 mm. La faculté germinative a été mesurée via l’essai

normalisé au tétrazolium.
5.4.1.2.2 Entrepôt 2

Les expériences ont été menées dans un entrepôt commercial au cours d’une opération normale de

chargement de blé fourrager. Les camions étaient chargés à partir de blé en vrac au sol, au moyen

d’un chargeur frontal à godet, et ils ont fait l’objet de prélèvements à leur départ de l’entrepôt.

L’échantillonnage normal consistait à prélever un seul échantillon par chargement au moyen d’une

sonde manuelle à compartiments d’environ 1,7 m de longueur. L’accès au chargement s’effectuait via

une petite plateforme d’échantillonnage qui limitait la prise d’échantillons à moins de la moitié de la

longueur de la remorque chargée, et sur un seul côté du chargement.

Aux fins de l’étude, 5 points d’échantillonnage ont été utilisés pour chaque chargement, les camions

avançant pendant le processus d’échantillonnage afin de permettre l’accès à la totalité de la longueur

du chargement. Pour des raisons pratiques, il n’a toutefois pas été possible de faire pivoter les camions

de façon à accéder aux deux côtés du chargement. Le recours à l’échantillonnage manuel a impliqué des

variations inévitables sur l’emplacement des points d’échantillonnage d’un chargement à un autre. Trois

volumes de sonde ont été prélevés en chaque point. Le premier a été conservé en tant qu’échantillon

individuel, le second a été combiné pour former un échantillon composite et le troisième a été combiné

pour former un échantillon dans lequel trois échantillons aléatoires (petit, moyen, grand) ont été

prélevés sans mélange.
Dix chargements de camion ont été échantillonnés sur deux jours.
5.4.1.2.3 Entrepôt 3

Les expériences ont été menées dans un entrepôt commercial au cours d’une opération normale de

chargement de blé meunier. Les échantillons ont été prélevés au moyen d’un échantillonneur Samplex

CS90, mais sans l’option automatique. La sonde a donc dû être pilotée manuellement par l’opérateur,

ce qui a induit des variations considérables de positionnement des points d’échantillonnage d’un

chargement à un autre. Une contrainte supplémentaire était l’emplacement du CS90, positionné à une

extrémité du pont-bascule, ce qui limitait l’accès à la moitié seulement du chargement. Le volet de

fermeture de l’échantillonneur était ouvert au maximum et le grain a été prélevé uniquement lors de la

remontée de la sonde.

Les camions ont été chargés au moyen d’un chargeur à godets puisant dans un tas de blé en vrac de

2 000 t stocké au sol. Un nombre limité de chargements était expédié quotidiennement et en raison des

contraintes de temps, seuls 8 chargements ont pu être échantillonnés pendant cette évaluation.

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ISO/TR 29263:2021(F)

Trois échantillons ont été prélevés en 8 points d’échantillonnage, dans chaque chargement. Le premier

a été conservé en tant qu’échantillon individuel, le second a été combiné pour former un échantillon

composite et le troisième a été combiné pour former un échantillon dans lequel trois échantillons

aléatoires (petit, moyen, grand) ont été prélevés sans mélange. Les 8 points étaient disposés suivant

un schéma 3-2-3, les deux échantillons étant prélevés au niveau de la ligne centrale et chaque ligne de

3 étant positionnée sur les côtés du chargement (voir la Figure 1). Compte tenu de l’emplacement de

l’échantillonneur et de la position du camion sur le pont-bascule, les échantillons ont tous été prélevés

dans la moitié avant du chargement.

Figure 1 — Disposition des points d’échantillonnage utilisés par l’échantillonneur CS90

L’exploitant de l’entrepôt a communiqué l’évaluation de la qualité du lot de céréales, réalisée par le

personnel de l’entrepôt à la réception.
5.4.1.2.4 Entrepôt 4

Des chargements de blé meunier destinés à une grosse minoterie ont été échantillonnés au moyen

d’un Samplex CS90 automatique. L’expérience a été réalisée plusieurs mois après les évaluations

précédentes et il a été décidé que le prélèvement d’échantillons supplémentaires destinés à former des

lots composites ne se justifiait pas. Huit échantillons ont été prélevés dans huit chargements de blé,

sur une période de 10 jours. La collecte des échantillons ayant dû être réalisée par le personnel de la

minoterie pour des raisons techniques, les détails exacts des points échantillonnés ne sont pas connus.

5.4.1.3 Évaluation des échantillons

Les échantillons ont dû être transportés vers le laboratoire d’essai, ce qui a occasionné des délais

supplémentaires entre le prélèvement et l’évaluation des échantillons. Toutefois, les échantillons

n’ayant pu être analysés sous un délai de 48 h ont été conservés dans un congélateur à −16 °C, afin de

réduire le plus possible les modifications de propriétés des grains. Ces échantillons ont été laissés au

repos jusqu’à la température ambiante avant les essais. Les échantillons provenant de l’entrepôt 4 font

exception à ce protocole.

Ces échantillons ont été collectés sur une période de 10 jours, et 4 jours supplémentaires se sont écoulés

avant l’arrivée des échantillons au laboratoire d’essai. Durant cette période, les échantillons n’ont pas

été maintenus dans des conditions de température contrôlées.

Les échantillons individuels ont été soumis à essai séparément, de même que les échantillons aléatoi

...

TECHNICAL ISO/TR
REPORT 29263
First edition
Cereals and cereal products —
Sampling studies
Céréales et produits céréaliers — Études sur l'échantillonnage
PROOF/ÉPREUVE
Reference number
ISO/TR 29263:2021(E)
ISO 2021
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ISO/TR 29263:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

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Published in Switzerland
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ISO/TR 29263:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Context ............................................................................................................................................................................................................................ 1

5 Study n°1: extract from "Grain sampling and assessment: sampling grain in lorries"

– Project report n° 339” ................................................................................................................................................................................. 1

5.1 General ........................................................................................................................................................................................................... 1

5.2 Context ........................................................................................................................................................................................................... 1

5.3 Studies conducted and objectives........................................................................................................................................... 3

5.4 Methodology ............................................................................................................................................................................................. 3

5.4.1 Conducting tests ............................................................................................................................................................... 3

5.4.2 Results and conclusions .................. ......................................................................................................................... .. 5

6 Study n°2: extract from "Sampling grain in static and flowing condition –

alternatives to the regulatory protocol" ...................................................................................................................................19

6.1 General ........................................................................................................................................................................................................19

6.2 Context ........................................................................................................................................................................................................20

6.2.1 Regulatory aspect .........................................................................................................................................................20

6.2.2 Normative aspect ..........................................................................................................................................................20

6.3 Studies conducted and objectives........................................................................................................................................20

6.3.1 Study A ...................................................................................................................................................................................20

6.3.2 Study B ...................................................................................................................................................................................21

6.4 Study A: silos and lorries of wheat and corn – Fusariotoxins and quality assessment .........21

6.4.1 Organising field tests .................................................................................................................................................21

6.4.2 Results and conclusions .................. ........................................................................................................................33

6.5 Study B : silos of corn – Fusariotoxins; flowing grains ......................................................................................48

6.5.1 Organising field tests .................................................................................................................................................48

6.5.2 Results and conclusions .................. ........................................................................................................................49

7 Study n°3: extract from "Investigation of the distribution of deoxynivalenol and

ochratoxin a contamination within a 26-T truckload of wheat kernels" – Project report ....90

7.1 Context ........................................................................................................................................................................................................91

7.2 Methodology ..........................................................................................................................................................................................91

7.2.1 Instruments for sampling and sample homogenization process ........................................91

7.2.2 Reagents and materials ...........................................................................................................................................91

7.2.3 Sampling procedure ...................................................................................................................................................92

7.2.4 Sample comminution ................................................................................................................................................93

7.3 Results and Discussion ..................................................................................................................................................................93

7.3.1 Distribution of DON and OTA infected kernels within the lot ................................................93

7.3.2 Sample comminution study for the dry milling process.............................................................95

7.4 Uncertainty comparison on the basis of number of incremental samples ......................................95

7.5 Conclusions .............................................................................................................................................................................................97

Bibliography .............................................................................................................................................................................................................................98

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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4,

Cereals and pulses, in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 338, Cereal and cereal products, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/TR 29263:2021(E)
Introduction

This document presents the results of three groups of studies which results have been used to elaborate

ISO 24333

These studies have been managed by United Kingdom in May 2003, by France in 2004-2005 for the first

one and 2006-2007 for the second one and Germany in 2008.
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TECHNICAL REPORT ISO/TR 29263:2021(E)
Cereals and cereal products — Sampling studies
1 Scope

This document presents the description and the results of the three studies conducted by United

Kingdom, France and Germany related to grain sampling in order to define a harmonized sampling

protocol for official controls.
These results had been used to draft ISO 24333.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Context

European directives for official controls of some contaminants such as mycotoxins required methods

for sampling and analysis. In order to harmonize sampling procedures necessary for these analysis and

to determine the best way to prepare a homogenous and representative laboratory sample, studies had

been conducted by United Kingdom, France and Germany.
The results of these 3 studies are presented in this report.
5 Study n°1: extract from "Grain sampling and assessment: sampling grain in
lorries" – Project report n° 339”
5.1 General
By J. KNIGHT, R. WILKIN and J. RIVETT

Department of Environmental Science and Technology, Renewable Resources Assessment Group,

Imperial College of Science and Technology, Prince Consort Road, London SW7 2BB

This is the final report of a 13-month project that started in May 2003. The work was funded by HGCA

(project 2955).
5.2 Context

This two-year programme was made at the request of HGCA to improve and standardise grain sampling

and analysis across the UK cereals industry.
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The first phase of the programme was to develop and validate protocols suitable for collecting samples

of grain on UK farms at harvest time and to train farmers in their use. The second part was to examine

approaches to the collection of samples during storage and to compare the results obtained, wherever

possible, with data collected as the store was filled. During the course of earlier sampling work, there

was strong interest expressed in the mechanics and effectiveness of sampling loads of grain in lorries.

In addition, some of the work done during storage involved sampling grain as it left the store in lorries.

This showed up the limitations of some approaches to lorry sampling and highlighted the need for more

information. An assessment of lorry sampling was therefore, added and is reported here.

Almost all grain is sampled as it is delivered to end users to confirm its quality and to ensure that

contractual obligations are met. This sampling takes the form of collecting one or more samples from a

lorry-load on arrival. The equipment used and method of sampling varies between end users and there

are no data to show if these variations may cause bias in the representativeness of the sample and,

therefore, in the results of quality analysis.

The key aim of end-user sampling is to ensure that the quality of the grain is suitable for its intended

use. Therefore, sampling is done before the load is tipped and this limits access to the surface of the

load. This access is further constrained by food safety and HSE legislation that prevent the sampler

from walking on the load.

A limited assessment of the practicalities of sampling lorries was done in 1992 (HGCA Project

Report 79) in which the effects of method of sampling, number and position of sample points, the

methods of loading lorries were considered. The wheat sampled was low-grade feed material with a low

specific weight and a high level of fine material so was not representative of other grades. The results

suggested that loading lorries with a front loader or from a hopper had no effect on the distribution of

the quality characteristics within a load. Small differences were noted in the mean values for specific

weight between automatic sampling using a Samplex CS90 and a manual spear but overall variability

of the grain meant that these differences were not significant. There was significant variability in the

results obtained at individual points with either method, although this variability was random and not

associated with any part of the load. Fine material appeared to be very difficult to measure. At the time,

this work was undertaken there were no restrictions limiting access to the surface of the grain so that a

widely disbursed pattern of sampling points could be used with the manual sampling. The conclusions

from this work were that it was extremely unwise to base an assessment of lorry load of grain on a

single sample and that more work was needed to confirm the results and to assesses other grades of

grain. The aim of this project was to establish if there are any inherent problems with the sampling of

grain for the determination of quality characteristics in lorries at the point of intake and to establish

recommendations in the form of a protocol for the sampling of grain under these conditions.

Grain was sampled using automated systems (Samplex CS90) and manual spearing to see if the method

of sampling influenced the grain quality measurements. A key part of the process was to assess the

influence that the number of samples taken from each load had on the likely accuracy of the results.

Samples were collected at 4 different locations; on two occasions 10 lorries were sampled and on two

occasions 8 lorries were sampled. At three locations, CS90 samplers were used and 8 samples were

withdrawn from each load and at the other location samples were taken manually with a multi-

compartmented spear with 5 samples being taken from each lorry. A comparison of different ways

of sample handling was obtained by comparing the individual results from the 8 samples against an

analysis of samples withdrawn from a composite sample formed from 8 samples. The latter method

reflects more accurately the procedure followed at most stores.

Results indicated that there were no statistically significant differences between results from the

individual samples or from the composite samples. Monte Carlo simulation of the impacts of using 2, 3, 5

or 8 samples per load revealed that the greater the number of samples used the greater the reliability of

the result and the more likely it was to represent the true mean of the load. It was noted that automatic

sampling equipment can no longer sample the entire length of a trailer and this could cause problems

with obtaining the ideal sample. Manual sampling also had severe limitations due to the lack of safe

access for sampling of trailers.

A sampling protocol for lorries is presented which emphasises the need for 8 samples to be taken from

each load in order to get a good representation of the quality of the entire load.

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5.3 Studies conducted and objectives

The study was conducted to assess the effectiveness of different approaches to sampling loads of grain

in lorries.
The specific objectives were:

— To assess if the method of collecting samples influences grain quality measurement;

— To assess if the number and position of sampling points influences grain quality measurement;

— To provide guidelines for sampling lorries giving reliable information about grain quality.

5.4 Methodology
5.4.1 Conducting tests
5.4.1.1 Collection of data relating to current sampling practice

In November 2002 the HGCA circulated a questionnaire to commercial grain stores and end-users of

grain requesting information about their methods of analysis and methods of intake sampling. The

information that was collected was used to assist with the design of the assessment of lorry sampling.

5.4.1.2 Sample collection
5.4.1.2.1 Store 1

The work was done at a store specialising in the storage of malting barley. Lorries were loaded with

malting barley, variety Pearl, of a quality representative of that delivered to central storage from farms.

The lorries, all 28 t articulated units, were loaded with a front loader fitted with a 2 t bucket.

Ten loads were sampled over a 2-day period. Sampling was done using the store’s Samplex CS90

automated vacuum sampler. Initially, it had been expected to re-programme the CS90 to take 10

samples/load in a pre-set pattern. However, observation of the method of operation and sampling

pattern achieved by the CS90 suggested that there was no advantage in using more than the 8 points

provided by one of the standard sampler programmes.

During the setting up and initial testing of the CS90, the slide on the sample spear was opened to its

maximum to increase the sample size. The system was set to collect grain only during the withdrawal

as is recommended by the manufacturer for granular materials.

Each of the eight points was sampled three times. On the first occasion, individual samples were held

separately. During the second and third samplings, all samples were bulked into single batches. One of

these bulk samples was held as a composite sample and the other was used to provide samples of 1, 2

and 3 litres (small medium and large) collected at random with a 1-litre jug.

A small sub-sample from each of the individual samples was tested on the spot by store staff for

screenings and germinative capacity. Screenings were tested by sieving a 100 g sub-sample with

a motorised shaker fitted with a 2,25 mm mesh screen for 2 minutes. The germinative capacity was

tested using the standard tetrazolium test.
5.4.1.2.2 Store 2

Work was done at a commercial store during the normal out-loading of feed wheat. The lorries were

loaded from an on-floor bulk using a front-bucket loader and were sampled as they left the store. Normal

sampling practice was to collect a single spear sample/load using a manual, multi-compartmented spear

of about 1,7 m in length. Access to the load was via a small sampling platform that only allowed samples

to be taken from less than half the length of the loaded trailer and from only one side of the load.

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For the purposes of this investigation, 5 sample points were used for each load and the lorry was moved

forward during the sampling process so that access to the whole length of the load could be obtained.

However, it was not practical to turn the lorry round to give access to both sides of the load. Manual

sampling meant that there was, inevitably, some variation in the exact location of the sample points

between loads. Three spear samples were collected at each point. The first was held as an individual

sample, the second bulked to form a composite sample and the third bulked to give a sample from which

three random samples (small, medium and large) could be taken without mixing.
Ten lorry loads were sampled over a two-day period.
5.4.1.2.3 Store 3

The assessments were made at a commercial store during the normal out-loading of milling wheat.

Samples were collected using a Samplex CS90 but without the automatic option. Therefore, the spear

had to be controlled manually by the operator and this meant that there was considerable variation in

the positioning of sample points between loads. A further constraint on sampling was that the CS90

was positioned at one end of the weighbridge thus limiting access to just one-half of the load. The slide

on the sampler was fully open and grain was collected only as the spear withdrew.

The lorries were loaded using a bucket loader from a 2 000 t batch of wheat stored on-floor. Only a

limited number of loads were dispatched each day and time constraints meant that only 8 loads were

sampled during this assessment.

Three samples were collected from 8 sample points in each load. The first was held as an individual

sample, the second bulked to form a composite sample and the third bulked to give a sample from

which three random samples (small, medium and large) could be taken without mixing. The 8 points

were arranged in a 3, 2, 3 pattern with the two samples being taken from the centre line and each row

of 3 taken down the sides of the load (see Figure 1). The location of the sampler and the position of the

lorry on the weighbridge meant that the samples always came from the front half of the load.

Figure 1 — Arrangement of sampling points used by CS90 sampler

Data was supplied by the storekeeper giving the store’s own assessment of the quality of the batch of

grain as measured when the store was filled.
5.4.1.2.4 Store 4

Loads of milling wheat delivered to a large flour mill were sampled with a Samplex automatic CS90.

This work was done some months after the earlier assessments and it was decided that the collection of

extra samples to make up composite batches was not justified. Eight samples were collected from eight

loads of wheat over a 10 d period. For technical reasons, the collection of samples had to be done by mill

staff so the exact details of the points sampled are not known.
5.4.1.3 Assessment of samples

Samples had to be transported to the testing laboratory and some additional delays occurred between

the collection and assessment of samples. However, samples that could not be analysed within 48 h

were stored in a freezer at -16 °C to minimise changes in the properties of the grain. These samples

were allowed to return to ambient temperature before testing. The exceptions to this were samples

collected from store 4.
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These were collected over a 10 d period and a further 4 d elapsed before the samples arrived for testing.

During this period, the samples were not held under controlled temperature conditions.

Individual samples were tested separately, as were the three different sizes of random sample. However,

in the case of the medium and large samples, these were divided by coning and quartering to give the

correct volume of grain for assessment. The composite samples were also mixed and then divided by

coning and quartering. Five sub-samples of the composites were tested from Store1 but only three sub-

samples were tested from stores 2 and 3.

As a first step in the assessment process, the screenings in each sample were measured by manual

sieving. Each sample was weighed and then sieved for 30 s using a 2,5 mm slotted sieve for wheat or a

2,25 mm slotted sieve for barley. The sievings were weighed and the percentage calculated. The weights

of the individual samples gave an indication of the variation in the size of sample collected on each

occasion.

After sieving, the properties of each sample were assessed using a Foss Infratec Grain Analyser 1241

GA-TWM . The machine used official calibrations as provided by the NIR network and measured

moisture content, specific mass, protein in the case of wheat, or nitrogen in the case of barley and made

an assessment of hardness of wheat.

In addition, some of the samples of wheat from stores 2 and 3 were sent to NIAB for assessment of

Hagberg Falling Number. Complete sets of individual samples from 5 loads, together with a single

composite sample were tested from Store 3. Complete sets of individual samples and a single composite

from 4 loads were tested from Store 2. The testing was done using standard methodology and each

result was the mean of two determinations.
5.4.1.4 Estimating the reliability of sampling

The impact of the number of samples taken on the reliability of the result obtained from those samples

was assessed by determining the mean and standard deviation for the results of the 8 samples taken

from each lorry. This information was used to define a probability curve for a normal distribution for

each of the lorries. A Monte Carlo simulation was then run to sample from either 2, 3, 5 or 8 of these

distributions depending on the sampling regime to be simulated. The simulation was run for a total of

100 000 trials. From this result, cumulative probability distribution curves were obtained and these

were used to estimate the confidence limits for different numbers of samples for a given margin of

error. Thus, the confidence interval for sampling 2, 3, 5, or 8 times for a known deviation from the mean

for the different quality parameters could be produced. The final figure shows the probability of the

confidence interval actually covering the mean value.
5.4.2 Results and conclusions
5.4.2.1 Sample analysis results
5.4.2.1.1 Collection of data relating to current sampling practice

As part of the initiative to standardise grain testing a survey of laboratory practice was undertaken

and this included a set of questions on the collection of samples from lorry-loads of grain. This provided

information from a range of commercial premises receiving, handling or processing grain about current

lorry sampling practices. The response showed that there was no common industry-wide approach.

The most frequently used equipment was the Samplex CS90 or other unspecified Samplex units (49 %)

followed by manual sampling (37 %). The number of samples collected per load ranged between 1 and

10 and the mass of grain collected varied between 0,4 kg and 11 kg.

1) Foss Infratec Grain Analyser 1241 GA-TWM is an example of a suitable product available commercially. This

information is given for the convenience of users of this document and does not constitute an endorsement by ISO

of thisproduct.
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5.4.2.1.2 Observations on the sampling
5.4.2.1.2.1 Store 1

During the assessment, it became apparent that the reach of the CS90 sampling arm and the size of

current a
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