Cereal and cereal products - Technical report of the interlaboratory study for the determination of impurities content in maize (Zea mays, L.) and sorghum (Sorghum bicolor, L.)

The term impurities applies to all components of a grain sample that differ from the normal basic cereal. It includes the following groups: broken grains, other cereals, grains damaged by pests, grains overheated during drying, sprouted grains, extraneous seeds, unsound grains, extraneous matter and impurities of animal origin.
The principle of the determination of impurities content is to separate all the groups of impurities from the normal basic cereal grains of unimpaired quality by sieving and manual selection out of a subsample and to quantify them. There are various problems in the determination of impurities:
Firstly, the identification of the different groups of impurities depends strongly on the experience and the knowledge of the investigator.
Also experienced investigators can differ in their characterization of grains.
Finally, one is faced with the fact that grain, even after mixing, is rarely homogenous. In other words, if a sample was divided by a sample divider into a number of portions, the amount of a specific group of impurities in each portion could be different, even if absolutely no human or machine error occurred in each determination.
These problems will result in variation of the results of the determination.
An international interlaboratory test for the determination of impurities, according to this standard and involving 14 laboratories in 4 countries, was carried out with 5 maize and 3 sorghum samples. It was asked to participants to make determination in duplicate.
Ten laboratories reported results for the complete sample set and two only for corns.
The test materials ranged between:
-   0,0 % and 2,7 % for broken grains;
-   0,2 % and 3,5 % for grain impurities;
-   0,0 % and 0,1 % for sprouted grains;
-   0,5 % and 3,3 % for miscellaneous impurities;
-   1,8 % and 8,7 % for total impurities.
The aim of the study is to determine the precision, repeatability and reproducibility of the method of determination of impurities content in maize and sorghum samples.
The analyses were realized in March - April 2011.
It occurs according to the ISO 5725:1994.

Céréales et produits céréaliers - Rapport technique de l'étude interlaboratoires pour la détermination de la teneur en impuretés dans le maïs (Zea mays, L.) et le sorgho (Sorghum bicolor, L.)

Žito in žitni proizvodi - Tehnično poročilo medlaboratorijske študije o določevanju nečistoč v koruzi (Zea mays, L.) in prosu (Sorghum bicolor, L.)

Izraz »nečistoče« se nanaša na vse sestavine vzorca zrnja, ki se razlikujejo od običajnega osnovnega žita. Vključuje naslednje skupine: lomljena zrna, druga žita, zrna, ki so jih poškodovali škodljivci, zrna, ki so se pregrela med sušenjem, nakaljena zrna, tuja semena, nezdrava zrna, tuje snovi in nečistoče živalskega izvora.
Načelo določevanja nečistoč je ločiti vse skupine nečistoč od običajnega osnovnega žita v zrnju neoslabljene kakovosti s sejanjem in ročnim prebiranjem podvzorca ter jih količinsko opredeliti. Pri določevanju nečistoč se pojavljajo različne težave.
Opredelitev različnih skupin nečistoč je na primer zelo odvisna od izkušenj in znanja preiskovalca.
Tudi izkušeni preiskovalci lahko različno določijo lastnosti zrn.
Nenazadnje je treba upoštevati dejstvo, da je zrnje tudi po mešanju redko homogeno. Drugače povedano, če bi se vzorec z razdeljevalnikom vzorca razdelil na več delov, bi se lahko količina določene skupine nečistoč med posameznimi deli razlikovala, čeprav pri posamezni določitvi zagotovo ni bilo človeške ali strojne napake.
Zaradi teh težav bodo rezultati določevanja različni.
Mednarodni medlaboratorijski preskus za določevanje nečistoč, ki je bil izveden v skladu s tem standardom in pri katerem je sodelovalo 14 laboratorijev v 4 državah, je bil izveden s 5 vzorci koruze in 3 vzorci prosa. Sodelujoči laboratoriji so morali vsako določevanje izvesti po dvakrat.
Deset laboratorijev je sporočilo rezultate za celoten sklop vzorcev, dva pa le za koruzo.
Preskusne snovi so zajemale:
– 0,0 % do 2,7 % za lomljena zrna;
– 0,2 % do 3,5 % za nečistoče zrn;
– 0,0 % do 0,1 % za nakaljena zrna;
– 0,5 % do 3,3 % za druge nečistoče;
– 1,8 % do 8,7 % za celotne nečistoče.
Cilj študije je določiti natančnost, ponovljivost in možnost reprodukcije metode za določevanje nečistoč v vzorcih koruze in prosa.
Analize so se izvajale od marca do aprila 2011.
Upoštevan je bil standard ISO 5725:1994.

General Information

Status
Published
Publication Date
08-Sep-2015
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
09-Sep-2015
Completion Date
09-Sep-2015

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SLOVENSKI STANDARD
SIST-TP CEN/TR 16875:2015
01-november-2015

äLWRLQåLWQLSURL]YRGL7HKQLþQRSRURþLORPHGODERUDWRULMVNHãWXGLMHRGRORþHYDQMX

QHþLVWRþYNRUX]L =HDPD\V/ LQSURVX 6RUJKXPELFRORU/

Cereal and cereal products - Technical report of the interlaboratory study for the

determination of impurities content in maize (Zea mays, L.) and sorghum (Sorghum
bicolor, L.)

Céréales et produits céréaliers - Rapport technique de l'étude interlaboratoires pour la

détermination de la teneur en impuretés dans le maïs (Zea mays, L.) et le sorgho
(Sorghum bicolor, L.)
Ta slovenski standard je istoveten z: CEN/TR 16875:2015
ICS:
67.060 äLWDVWURþQLFHLQSURL]YRGLL] Cereals, pulses and derived
QMLK products
SIST-TP CEN/TR 16875:2015 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 16875:2015
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SIST-TP CEN/TR 16875:2015
CEN/TR 16875
TECHNICAL REPORT
RAPPORT TECHNIQUE
September 2015
TECHNISCHER BERICHT
ICS 67.060
English Version
Cereal and cereal products - Technical report of the
interlaboratory study for the determination of impurities
content in maize (Zea mays, L.) and sorghum (Sorghum
bicolor, L.)
Céréales et produits céréaliers - Rapport technique de
l'étude interlaboratoires pour la détermination de la
teneur en impuretés dans le maïs (Zea mays, L.) et le
sorgho (Sorghum bicolor, L.)

This Technical Report was approved by CEN on 27 July 2015. It has been drawn up by the Technical Committee CEN/TC 338.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16875:2015 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Design of the study.......................................................................................................................................... 6

3.1 Conception and organization ...................................................................................................................... 6

3.1.1 Method ................................................................................................................................................................ 6

3.1.2 Participants ....................................................................................................................................................... 6

3.1.3 Design and schedule of the study .............................................................................................................. 6

3.2 Product ................................................................................................................................................................ 6

3.3 Fabrication ........................................................................................................................................................ 6

3.4 Homogeneity and stability ........................................................................................................................... 6

3.5 Form ..................................................................................................................................................................... 6

4 Statistics ............................................................................................................................................................. 7

4.1 Methodology ..................................................................................................................................................... 7

4.2 Statistical treatment....................................................................................................................................... 7

5 Results of the interlaboratory study ........................................................................................................ 7

5.1 Validation of the raw results ....................................................................................................................... 7

5.2 Detection of stragglers and outliers ......................................................................................................... 7

5.3 Stragglers and outliers detections ............................................................................................................ 9

5.4 Statistics .......................................................................................................................................................... 10

5.5 Results .............................................................................................................................................................. 10

Annex A (informative) Raw results ..................................................................................................................... 16

A.1 Broken grains ................................................................................................................................................ 16

A.2 Grains impurities ......................................................................................................................................... 17

A.3 Sprouted grains ............................................................................................................................................. 18

A.4 Miscellaneous impurities .......................................................................................................................... 19

A.5 Total impurities ............................................................................................................................................ 20

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European foreword

This document (CEN/TR 16875:2015) has been prepared by Technical Committee CEN/TC 338 “Cereal

and cereal products”, the secretariat of which is held by AFNOR.

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

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
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Introduction

The principle of the determination of impurities is to separate all the groups of impurities from the

normal basic cereal grains of unimpaired quality by sieving and manual selection out of a subsample

and to quantify them. The amount of impurities and its constituent groups is important for health,

cleaning, milling and further processing aspects. For these reasons impurities content is a part of

contracts in grain trade and also of the grain intervention system of the EU.

At present a European standard for the determination of impurities in maize and sorghum (EN 16378)

has been developed.

An international interlaboratory trial for the determination of impurities in maize and sorghum was

accomplished in order to get information on the intra- and interlaboratory variability of the

determination of impurities content.

The technical report here describes the preparation and evaluation of the results of this interlaboratory

test.
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1 Scope

The term impurities applies to all components of a grain sample that differ from the normal basic cereal.

It includes the following groups: broken grains, other cereals, grains damaged by pests, grains

overheated during drying, sprouted grains, extraneous seeds, unsound grains, extraneous matter and

impurities of animal origin.

The principle of the determination of impurities content is to separate all the groups of impurities from

the normal basic cereal grains of unimpaired quality by sieving and manual selection out of a subsample

and to quantify them. There are various problems in the determination of impurities:

Firstly, the identification of the different groups of impurities depends strongly on the experience and

the knowledge of the investigator.
Also experienced investigators can differ in their characterization of grains.

Finally, one is faced with the fact that grain, even after mixing, is rarely homogenous. In other words, if a

sample was divided by a sample divider into a number of portions, the amount of a specific group of

impurities in each portion could be different, even if absolutely no human or machine error occurred in

each determination.
These problems will result in variation of the results of the determination.

An international interlaboratory test for the determination of impurities, according to this standard and

involving 14 laboratories in 4 countries, was carried out with 5 maize and 3 sorghum samples. It was

asked to participants to make determination in duplicate.

Ten laboratories reported results for the complete sample set and two only for corns.

The test materials ranged between:
— 0,0 % and 2,7 % for broken grains;
— 0,2 % and 3,5 % for grain impurities;
— 0,0 % and 0,1 % for sprouted grains;
— 0,5 % and 3,3 % for miscellaneous impurities;
— 1,8 % and 8,7 % for total impurities.

The aim of the study is to determine the precision, repeatability and reproducibility of the method of

determination of impurities content in maize and sorghum samples.
The analyses were realized in March - April 2011.
It occurs according to ISO 5725:1994.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

EN 16378, Cereals - Determination of impurities content in maize (Zea mays, L.) and sorghum (Sorghum

bicolor, L.)
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3 Design of the study
3.1 Conception and organization
3.1.1 General

The interlaboratory comparisons of this test were designed according to the wishes of AFNOR and

organized by BIPEA.
3.1.2 Method

The participants made a commitment to apply strictly the described method and to prepare the samples

according to the method provided with the commitment letter for participating to the test: the standard

EN 16378.
3.1.3 Participants

Fourteen laboratories made a commitment to participate to the test. Twelve did answer.

3.1.4 Design and schedule of the study

Each laboratory received eight samples: 5 samples of corn and 3 samples of sorghums, according to a

blind distribution.

In order to take into account the sampling of the laboratory into the precision values, the laboratories

realized two analytical series on two sub-samples from each sample, leading to sixteen determinations

of impurities.
Tests were conducted between March, 1st and April, 26th, 2011.

In order to be as close as possible to repeatability conditions, the two sub-samples analyses has been

realized during a time as short as possible. The repeatability variance is an intra-laboratory variance.

However, in order to be easier to read, it is called repeatability mean in the report.

3.2 Product

In order to cover the scope of the method, the products analysed are maize mixes and sorghum mixes.

3.3 Fabrication
The samples are produced according to the following procedure:

Each batch is homogenized and divided in samples serials. This operation is made with a carousel. The

principle of turning spreading, that involves a progressive filling, ensures the homogeneity of the

product between each sample.

The samples of maize 1, 2 and 4 and the samples of sorgho 1 and 3 were of 500 g in paper bags. The

samples of maize 3 and 5 and the samples of sorgho 2 were of 1 kg in paper bags. The weights were

increased for some samples in order to integer the division step inside the laboratory.

3.4 Homogeneity and stability

On this test, no control was planned. However, homogeneity and stability were considered as sufficient

by the working group for the test, during its conception.
3.5 Form

In addition to final results, expressed in % of impurities, the weights values were requested to the

participants. The form sheet template is in A.2.
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4 Statistics
4.1 Methodology

The precision parameters were calculated on the two sub-samples of each impurity category according

to the following plan.
Figure 1
4.2 Statistical treatment
The statistical treatment was carried out according to ISO 5725-2.
5 Results of the interlaboratory study
5.1 Validation of the raw results

The project leader realized the checks of the calculations of impurities contents from the weight values.

A laboratory seems not to have followed the method; it was excluded from the calculations of the

precision parameters (laboratory 7568).

A laboratory did not write correctly his results, it has a lack of traceability of its samples (laboratory

2190). The results of the corn 3 have been reported on the corn 2 form sheets, those of corn 4 on the

form sheet for corn 3 and those of corn 2 on the form sheet of corn 4.
The traceability and the results have been corrected.
5.2 Detection of stragglers and outliers

Stragglers and outliers detection have been realized with statistical tests on the provided results except

for the excluded laboratory above:
— Cochran’s test: outliers and stragglers for variances (at 5 % and 1 %);
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— Grubbs’ test: outliers and stragglers for means (at 5% and 1 %).
The principles of the tests and the decision rules are described in ISO 5725-2.

The results of those tests are presented in Table A.9 and Table A.10, in A.5. As abstract:

— For the corn 1:

— the variance of the laboratory 8577 for miscellaneous impurities has been detected as outlier;

— the variance of the laboratory 8577 for total impurities has been detected as straggler;

— the mean of the laboratory 7489 for broken grains has been detected as outlier;

— the mean of the laboratory 6723 for total impurities has been detected as straggler.

— For the corn 2:

— the variance of the laboratory 5909 for broken grains has been detected as outlier;

— the mean of the laboratory 7489 for broken grains has been detected as outlier;

— the mean of the laboratories 6723 and 8577 for miscellaneous impurities has been detected as

straggler;
— For the corn 3:

— the variance of the laboratories 5909 for miscellaneous impurities and 6723 for total

impurities has been detected as outlier;

— the variance of the laboratory 6637 for sprouted grains has been detected as straggler;

— the mean of the laboratory 8577 for miscellaneous impurities and for total impurities has been

detected as straggler.
— For the corn 4:

— the variance of the laboratory 8577 for sprouted grains and for grain impurities has been

detected as outlier;

— the variance of the laboratory 8577 for broken grains and for total impurities has been

detected as straggler;

— the mean of the laboratory 8577 for miscellaneous impurities has been detected as straggler.

— For the corn 5:

— the variance of the laboratory 8577 for broken grains and for miscellaneous impurities has

been detected as outlier;

— the variance of the laboratory 8577 for grain impurities and for total impurities has been

detected as straggler;

— the mean of the laboratory 6723 for grain impurities, for miscellaneous impurities and for total

impurities;
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— the mean of laboratory 8577 for miscellaneous impurities has been detected as straggler.

— For the sorgho 1:

— the variance of the laboratory 5703 for grain impurities has been detected as outlier;

— the mean of the laboratory 6723 for grain impurities has been detected as straggler.

— For the sorgho 2:

— the variance of the laboratory 7489 for total impurities has been detected as outlie;

— the variance of the laboratory 7489 for miscellaneous impurities has been detected as straggle;

— the mean of the laboratory 6723 for grain impurities has been detected as straggler.

— For the sorgho 3:
— the varia
...

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