Maize - Determination of moisture content (on milled grains and on whole grains) (ISO 6540:2021)

This document specifies two methods:
— a reference method for the determination of the moisture content of maize grains and ground whole
maize, groats, grits and maize flour, see Clause 4;
— a routine method for the evaluation of the moisture content of maize in whole grains, see Clause 5.
The latter is not suitable for use for experts’ reports, or for calibration or checking of humidity meters,
because of its significant bias to the reference method (see Table B.3).

Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern) (ISO 6540:2021)

Dieses Dokument legt zwei Verfahren fest:
- ein Referenzverfahren zur Bestimmung des Feuchtegehalts von ganzen Maiskörnern und gemahlenem Vollmais, Grobgrieß, Feingrieß und Maismehl, siehe Abschnitt 4;
- ein Routineverfahren zur Bewertung des Feuchtegehalts von ganzen Maiskörnern, siehe Abschnitt 5.
Das letztgenannte Verfahren ist wegen seiner signifikanten systematischen Abweichungskomponente gegenüber dem Referenzverfahren (siehe Tabelle B.3) nicht zur Anwendung für Fachberichte oder für die Kalibrierung oder Überprüfung von Feuchtemessgeräten geeignet.

Maïs - Détermination de la teneur en eau (sur grains broyés et sur grains entiers) (ISO 6540:2021)

Le présent document spécifie deux méthodes:
- une méthode de référence pour la détermination de la teneur en eau des grains de maïs et de la mouture de maïs entier, des gruaux et de la farine de maïs; voir l'Article 4;
- une méthode pratique pour l'évaluation de la teneur en eau des grains de maïs, en opérant sur les grains entiers; voir l'Article 5.
Cette dernière ne convient ni pour des expertises ni pour l'étalonnage ou le contrôle des humidimètres en raison de son biais important par rapport à la méthode de référence (voir le Tableau B.3).

Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO 6540:2021)

General Information

Status
Published
Public Enquiry End Date
19-May-2020
Publication Date
15-Apr-2021
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
11-Mar-2021
Due Date
16-May-2021
Completion Date
16-Apr-2021

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SLOVENSKI STANDARD
SIST EN ISO 6540:2021
01-maj-2021
Nadomešča:
SIST EN ISO 6540:2010
Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO 6540:2021)
Maize - Determination of moisture content (on milled grains and on whole grains) (ISO
6540:2021)
Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern) (ISO
6540:2021)
Maïs - Détermination de la teneur en eau (sur grains broyés et sur grains entiers) (ISO
6540:2021)
Ta slovenski standard je istoveten z: EN ISO 6540:2021
ICS:
67.060 Žita, stročnice in proizvodi iz Cereals, pulses and derived
njih products
SIST EN ISO 6540:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6540:2021

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SIST EN ISO 6540:2021


EN ISO 6540
EUROPEAN STANDARD

NORME EUROPÉENNE

March 2021
EUROPÄISCHE NORM
ICS 67.060 Supersedes EN ISO 6540:2010
English Version

Maize - Determination of moisture content (on milled
grains and on whole grains) (ISO 6540:2021)
Maïs - Détermination de la teneur en eau (sur grains Mais - Bestimmung des Feuchtegehalts (von
broyés et sur grains entiers) (ISO 6540:2021) gemahlenen und ganzen Körnern) (ISO 6540:2021)
This European Standard was approved by CEN on 13 February 2021.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6540:2021 E
worldwide for CEN national Members.

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SIST EN ISO 6540:2021
EN ISO 6540:2021 (E)
Contents Page
European foreword . 3

2

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SIST EN ISO 6540:2021
EN ISO 6540:2021 (E)
European foreword
This document (EN ISO 6540:2021) has been prepared by Technical Committee CEN/TC 338 "NA" in
collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” the secretariat of
which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2021, and conflicting national standards
shall be withdrawn at the latest by September 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 6540:2010.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 6540:2021 has been approved by CEN as EN ISO 6540:2021 without any modification.

3

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SIST EN ISO 6540:2021

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SIST EN ISO 6540:2021
INTERNATIONAL ISO
STANDARD 6540
Second edition
2021-02
Maize — Determination of moisture
content (on milled grains and on
whole grains)
Maïs — Détermination de la teneur en eau (sur grains broyés et sur
grains entiers)
Reference number
ISO 6540:2021(E)
©
ISO 2021

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SIST EN ISO 6540:2021
ISO 6540:2021(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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

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SIST EN ISO 6540:2021
ISO 6540:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference method . 1
4.1 Principle . 1
4.2 Apparatus . 1
4.3 Sampling . 2
4.4 Preparation of the test sample . 2
4.4.1 Products not requiring to be ground . 2
4.4.2 Products requiring to be ground . 3
4.5 Procedure . 3
4.5.1 Number of determinations. 3
4.5.2 Test portion . 3
4.5.3 Drying . 4
4.5.4 Weighing . 4
4.6 Expression of results . 4
4.7 Precision . 5
4.7.1 Interlaboratory test . 5
4.7.2 Repeatability . 5
4.7.3 Reproducibility . 5
4.7.4 Comparison of two groups of measurements in a laboratory . 5
4.7.5 Comparison of two groups of measurements in two laboratories . 5
4.7.6 Uncertainty . 6
4.7.7 Comparison with the absolute method . 6
4.8 Notes on procedure . 6
4.9 Test report . 6
5 Routine method on whole grains . 7
5.1 Principle . 7
5.2 Apparatus . 8
5.3 Sampling . 8
5.4 Procedure . 8
5.4.1 Test portion . 8
5.4.2 Drying . 8
5.4.3 Number of determinations. 8
5.5 Expression of results . 9
5.5.1 Method of calculation and formulae . 9
5.5.2 Repeatability . 9
5.5.3 Reproducibility . 9
5.5.4 Comparison of two groups of measurements in a laboratory . 9
5.5.5 Comparison of two groups of measurements in two laboratories .10
5.5.6 Application of fidelity limits.10
5.6 Remark .10
5.7 Test report .10
Annex A (informative) Absolute method .11
Annex B (informative) Interlaboratory test results .18
Annex C (informative) Application of fidelity data for the whole grains method .24
Bibliography .25
© ISO 2021 – All rights reserved iii

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SIST EN ISO 6540:2021
ISO 6540:2021(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 of 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 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).
This second edition cancels and replaces the first edition (ISO 6540:1980), which has been technically
revised. The main changes compared with the previous edition are as follows:
— Clauses 7 to 10 and 17 to 20 (now 4.5 to 4.9 and 5.4 to 5.7) and the annexes have been revised.
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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SIST EN ISO 6540:2021
ISO 6540:2021(E)

Introduction
The basic reference method and the routine reference method relating to cereals (see ISO 712) are
only applicable to other cereals than maize and cereal products. Therefore, this document has been
[4]
developed to specify the two methods for maize on the basis of research works published in 1979 .
The basic reference method for maize, which is called the “absolute method”, requires special equipment
and experienced personnel, and can only be applied in specialized laboratories.
Due to the very high moisture content that can be present in samples of maize (sometimes greater than
a mass fraction of 40 %) and because of the size and texture of the grains, the determination of the
moisture in maize raises problems with regard to its grinding and pre-drying.
Consequently, to allow the pre-drying and grinding to be avoided, this document also describes a
routine method for whole grains. which is easier to use and allows working in series. Its response time
is longer but the workload is lower, because of the absence of grinding. However, this practical whole
grain method has a positive bias of about a mass fraction of 0, 30 % compared to the reference method.
© ISO 2021 – All rights reserved v

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SIST EN ISO 6540:2021

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SIST EN ISO 6540:2021
INTERNATIONAL STANDARD ISO 6540:2021(E)
Maize — Determination of moisture content (on milled
grains and on whole grains)
1 Scope
This document specifies two methods:
— a reference method for the determination of the moisture content of maize grains and ground whole
maize, groats, grits and maize flour, see Clause 4;
— a routine method for the evaluation of the moisture content of maize in whole grains, see Clause 5.
The latter is not suitable for use for experts’ reports, or for calibration or checking of humidity meters,
because of its significant bias to the reference method (see Table B.3).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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/
3.1
moisture content of maize
loss in mass undergone by a product under specified conditions
Note 1 to entry: It is expressed as a percentage.
4 Reference method
4.1 Principle
If necessary, grinding of a sample, after pre-conditioning, if required. Drying of a test portion at a
temperature between 130 °C and 133 °C, under conditions that enable a result to be obtained in
agreement with that obtained by the absolute method (see Annex A).
4.2 Apparatus
4.2.1 Analytical balance, able to weight with an accuracy of ±0,001 g and therefore having a display
accuracy of 0,000 1 g.
4.2.2 Analytical balance, able to weight with an accuracy of ±0,1 g and therefore having a display
accuracy of 0,01 g.
© ISO 2021 – All rights reserved 1

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SIST EN ISO 6540:2021
ISO 6540:2021(E)

4.2.3 Grinding mill, having the following characteristics:
a) made of material that does not absorb moisture;
b) easy to clean and having as little dead space as possible;
c) enabling grinding of 30 g of maize grains to be carried out rapidly and uniformly, without
appreciable development of heat and, as far as possible, without contact with the outside air;
d) adjustable so as to obtain particles of the dimensions indicated in 4.4.1.
4.2.4 Metal boat, without lid, with an effective surface area enabling 100 g of maize grains to be
distributed in a single layer.
4.2.5 Metal capsule, of suitable dimensions, non-corrodible under the test conditions, or, failing this,
a glass dish, with a sufficiently tight-fitting lid, and having an effective surface area such as to allow
distribution of the test portion with no more than 0,3 g per square centimetre.
4.2.6 Constant-temperature oven, electrically heated, adjustable between 60 °C and 80 °C, and with
adequate ventilation.
4.2.7 Constant-temperature oven, electrically heated, capable of being controlled in such a way that
the temperature of the air and of the shelves carrying the test portions is within the range of 130 °C to
133 °C in the neighbourhood of the test portions, in normal working condition.
The oven shall have a heat capacity such that, when initially adjusted to a temperature of 131 °C, it can
again reach this temperature in less than 45 min (preferably in less than 30 min) after insertion of the
maximum number of test portions that can be dried simultaneously.
The effectiveness of the ventilation shall be determined using durum wheat semolina, with a maximum
particle size of 1 mm, as the test material. The ventilation shall be such that, after inserting all the test
portions that the oven can hold and drying at a temperature of 130 °C to 133 °C, the results after a heating
period of 2 h and then a further 1 h will not differ by more than 0,15 g of moisture per 100 g of sample.
4.2.8 Desiccator, containing an efficient desiccant.
4.3 Sampling
Sampling is not part of the method specified in this document. A recommended sampling method is
given in ISO 24333.
The laboratory should be provided with a truly representative sample, in a sealed package, that is
undamaged and unmodified during transport and storage.
4.4 Preparation of the test sample
4.4.1 Products not requiring to be ground
Products that have particles of sizes less than or equal to 1,7 mm, less than a mass fraction of 10 %
being over 1 mm and more than a mass fraction of 50 % being less than 0,5 mm, do not need to be
ground before the determination.
Mix the laboratory sample thoroughly before taking the test portion (see 4.5.3).
2 © ISO 2021 – All rights reserved

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SIST EN ISO 6540:2021
ISO 6540:2021(E)

4.4.2 Products requiring to be ground
4.4.2.1 General
If the laboratory sample does not have the particle size characteristics mentioned in 4.4.1, it shall be
ground either without pre-conditioning (4.4.2.2) or with pre-conditioning (4.4.2.3) as required.
4.4.2.2 Grinding without pre-conditioning
For products that are not likely to undergo variations in moisture content in the course of grinding (in
general, products with a moisture content between a mass fraction of 9,00 % and 15,00 %, see 4.8),
carry out grinding without pre-conditioning.
Adjust the grinding mill (4.2.3) to obtain particles of the dimensions indicated in 4.4.1.
Then quickly grind about 30 g of the laboratory sample, mix with a spatula and proceed immediately as
specified in 4.5.1.
4.4.2.3 Grinding with pre-conditioning
Products that are likely to undergo changes in moisture content in the course of grinding (in general,
products with a moisture content more than a mass fraction of 15,00 % or less than a mass fraction of
9,00 %) shall be pre-conditioned to bring their moisture content to between a mass fraction of 9,00 %
and 15,00 %, see 4.8) before grinding.
If the moisture content is greater than a mass fraction of 15,00 % (which is the more frequent case),
weigh, to the nearest 0,1g, about 100 g of the laboratory sample in the metal boat (4.2.4), place this
in the oven (4.2.7) controlled at between 60 °C and 80 °C, and leave it for the time necessary to bring
the moisture content to between a mass fraction of 9,00 % and 15,00 %. Take the boat out of the oven
and allow it to stand in the laboratory atmosphere for the time necessary (at least 2 h) for the pre-
conditioned sample to return to the laboratory temperature and for the moisture distribution to be
relatively uniform. During this rest, it shall be ensured that no addition or withdrawal of material is
made to the contents of the boat. If necessary, cover it with a sheet of paper but not with a lid, since this
could limit the exchange of moisture between the air and the grain.
After conditioning, weigh the sample to the nearest 0,1 g, then, proceeding rapidly, grind about 30 g of
this product. Mix using a spatula.
If the moisture content is less than a mass fraction of 9,00 %, place about 100 g of the laboratory sample,
weighed to the nearest 0,1 g, in a suitable atmosphere (usually that of the laboratory) and leave it until
a moisture content within the limits specified above is obtained.
4.5 Procedure
4.5.1 Number of determinations
For each laboratory sample, carry out the determination in duplicate.
Carry out one determination on each of the two ground test portions taken from the laboratory sample,
in accordance with 4.5.2 to 4.5.4. If the absolute difference between the two results is greater than the
repeatability limit given in 4.7.2, repeat the determination until the requirements are met.
4.5.2 Test portion
For each sample, tare to the nearest 0,001 g two metal capsules (4.2.5) beforehand. For each capsule,
note the tare t.
Weigh rapidly, to the nearest 0,001 g, approximately (8 ± 1) g of the test sample (see 4.4.1, 4.4.2.2 or
4.4.2.3, as appropriate) into the capsule. Note the mass m′ .
0
© ISO 2021 – All rights reserved 3

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SIST EN ISO 6540:2021
ISO 6540:2021(E)

4.5.3 Drying
Place the open capsule containing the test portion, and the lid, in the oven (4.2.7) controlled between
130 °C and 133 °C and leave it for 4 h ± 5 min.
Never place moist products in an oven containing test portions at the end of dehydration, nor open the
oven door during drying, nor introduce new wet test samples before removing the dry test portions as
this would rehydrate them.
At the end of the drying time and, proceeding rapidly, take the dish out of the oven, cover it and place it
in the desiccator (4.2.8). When several tests are being carried out simultaneously, never place dishes on
top of one another in the desiccator.
4.5.4 Weighing
When the dish has cooled to laboratory temperature (generally between 30 min and 45 min after it has
been placed in the desiccator), weigh it to the nearest 0,001 g. Note the mass m′ .
1
4.6 Expression of results
The moisture content, w , expressed as a percentage by mass of the product as received, is given by
H2O
Formulae (1) and (2):
a) without pre-conditioning:
100
w = mm− (1)
()
H200 1
m
0
where
m = m′ – t is the mass, in grams, of the test portion (see 4.5.3);
0 0
m = m′ – t is the mass, in grams, of the test portion after drying (see 4.5.4);
1 1
t is the tare of the capsule, in grams (see 4.5.2).
b) with pre-conditioning:
m
 
100
3
wm= −m +−mm (2)
()
 
H20 01 23
m m
 0  2
 mm 
13
w =100 1−
 
H20
mm
 
02
where
m and m have the same signification as in a) above;
0 1
m is the mass, in grams, of the sample before conditioning (see 4.4.2.3);
2
m is the mass, in grams, of the sample after conditioning (see 4.4.2.3).
3
Take as the result the average of the two values obtained, provided that the requirement for repeatability
(see 4.7.2) is satisfied. If it is not, repeat the determinations.
Express the result to the second decimal place.
4 © ISO 2021 – All rights reserved

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SIST EN ISO 6540:2021
ISO 6540:2021(E)

4.7 Precision
4.7.1 Interlaboratory test
The details of an interlaboratory test relating to the precision of the method are summarized in
Annex B. Values from this test can only be applied to water content ranges from 11,90 % to 39,20 % and
the studied matrix (maize).
4.7.2 Repeatability
The absolute difference between two independent individual test results, obtained using the same
method on identical material test
...

SLOVENSKI STANDARD
oSIST prEN ISO 6540:2020
01-maj-2020
Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO/DIS 6540:2020)
Maize - Determination of moisture content (on milled grains and on whole grains)
(ISO/DIS 6540:2020)
Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern)
(ISO/DIS 6540:2020)
Maïs - Détermination de la teneur en eau (sur grains broyés et sur grains entiers)
(ISO/DIS 6540:2020)
Ta slovenski standard je istoveten z: prEN ISO 6540
ICS:
67.060 Žita, stročnice in proizvodi iz Cereals, pulses and derived
njih products
oSIST prEN ISO 6540:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 6540:2020

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oSIST prEN ISO 6540:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 6540
ISO/TC 34/SC 4 Secretariat: SAC
Voting begins on: Voting terminates on:
2020-03-23 2020-06-15
Maize — Determination of moisture content (on milled
grains and on whole grains)
Maïs — Détermination de la teneur en eau (sur grains broyés et sur grains entiers)
ICS: 67.060
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 6540:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

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oSIST prEN ISO 6540:2020
ISO/DIS 6540:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 6540:2020
ISO/DIS 6540:2020(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Sampling . 2
7 Preparation of the test sample . 2
7.1 Products not requiring to be ground . 2
7.2 Products requiring to be ground . 2
7.3 Grinding with pre-conditioning . 3
8 Procedure. 3
8.1 Number of determinations . 3
8.2 Taring of capsules . 3
8.3 Test portion . 3
8.4 Drying . 3
8.5 Weighing . 4
9 Expression of results . 4
9.1 Method of calculation and formulae . 4
10 Precision . 4
11 Notes on procedure . 6
12 Test report . 6
13 Scope . 7
14 Terms and definitions . 8
15 Principle . 8
16 Apparatus . 8
17 Sampling . 8
18 Procedure. 8
18.1 Test portion . 8
18.2 Drying . 8
18.3 Number of determinations . 9
19 Expression of results . 9
19.1 Method of calculation and formulae . 9
19.2 Repeatability . 9
19.3 Reproductibility . 9
19.4 Comparison of two groups of measurements in a laboratory .10
19.5 Comparison of two groups of measurements in two laboratories .10
19.6 Application of fidelity limits .10
19.7 Remark .10
20 Test report .10
Annex A (informative) Absolute method .12
Annex B (informative) Inter-laboratory test results .19
Annex C (informative) Application of fidelity data for the whole grains method (section 2) .24
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Bibliography .25
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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 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.
The committee responsible for this document is Technical Committee ISO/TC 34, Food Products,
Subcommittee SC 4, Cereals and pulses.
This second edition cancels and replaces the first edition ISO 6540:1980 – Maïze – Determination of
moisture content (on milled grains and on whole grains), of which clauses 8 to 12 and 17 to 21, as well as
annexes, have been technically revised.
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Introduction
The basic reference method and the routine reference method relating to cereals (ISO 712 and its annex
B) are only applicable to maize with a number of amendments. This is why it has been considered
advisable to reproduce the whole of these two methods, amended for application to the case of maize.
The basic reference method, for maize, which is called the absolute method in this case, requires special
equipment and experienced personnel, and can only be applied in specialized laboratories.
Because of the very high moisture content which may be present in samples of maize [sometimes
greater than 40 % (m/m)] and because of the size and texture of the grains, the determination of the
moisture in maize raises problems with regard to its grinding and pre-drying.
Consequently, to allow the pre-drying and grinding to be avoided, this International Standard also
describes a routine method for whole grain (section 2) which is easier to use and allows working in
series. Its response time is longer but the workload is lower, because of the absence of grinding.
However, this practical whole grain method has a positive bias of about 0.30 % (w/w) compared to the
reference method.
Section one: Reference method
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DRAFT INTERNATIONAL STANDARD ISO/DIS 6540:2020(E)
Maize — Determination of moisture content (on milled
grains and on whole grains)
1 Scope
This section specifies the reference method for the determination of the moisture content of maize
grains and maize semolina.
2 Normative references
No other standard is indispensable for the application of this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
moisture content of maize
conventionally, the loss in mass, expressed as a percentage, undergone by the product under the
conditions specified in this section of this standard
4 Principle
If necessary, grinding of a sample, after pre-conditioning, if required. Drying of a test portion at a
temperature between 130 °C and 133 °C, under conditions which enable a result to be obtained which is
in agreement with that obtained by the absolute method (see the annex).
5 Apparatus
5.1 Analytical balance, able to weight with an accuracy of +/- 0.001 g and therefore having a display
accuracy of 0.1 mg.
5.2 Analytical balance, able to weight with an accuracy of +/- 0.1 g and therefore having a display
accuracy of 0.01 mg.
5.3 Grinding mill, having the following characteristics:
a) made of material which does not absorb moisture;
b) easy to clean and having as little dead space as possible;
c) enabling grinding of 30 g of maize grains to be carried out rapidly and uniformly, without
appreciable development of heat and, as far as possible, without contact with the out side air;
d) adjustable so as to obtain particles of the dimensions indicated in 7.1
5.4 Metal boat, without lid, with an effective surface area enabling 100 g of maize grains to be
distributed in a single layer.
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5.5 Metal dish, of suitable dimensions, non-corrodible under the test conditions, or, failing this, a glass
dish, with a sufficiently tight-fitting lid, and having an effective surface area such as to allow distribution
of the test portion with no more than 0,3 g per square centimeter.
5.6 Constant-temperature oven, electrically heated, adjustable between 60 °C and 80 °C, and with
adequate ventilation.
5.7 Constant-temperature oven, electrically heated, capable of being controlled in such a way that
the temperature of the air and of the shelves carrying the test portions is within the range of 130 °C to
133 °C in the neighbourhood of the test portions, in normal working.
The oven shall have a heat capacity such that, when initially adjusted to a temperature of 131 °C, it can
again reach this temperature in less than 45 min (preferably in less than 30 min) after insertion of the
maximum number of test portions that can be dried simultaneously.
The effectiveness of the ventilation shall be determined using durum wheat semolina, with a maximum
panicle size of 1 mm, as the test material. The ventilation shall be such that after in-serting all the test
portions that the oven can hold and drying at a temperature of 130 °C to 133 °C, the results after a heating
period of 2 h and then a further 1 h will not differ by more than 0,15 g of moisture per 100 g of sample.
5.8 Desiccator, containing an efficient desiccant.
6 Sampling
Sampling is not part of the method specified in this International Standard. A recommended sampling
method is given in ISO 24333 – Cereal and ceral products – Sampling.
The laboratory should be provided in a sealed package a truly representative sample, undamaged and
unmodified during transport and storage.
7 Preparation of the test sample
7.1 Products not requiring to be ground
Products which have particles of sizes less than or equal to 1,7 mm, less than 10 % (m/m) being
over 1 mm and more than 50 % (m/m) being less than 0,5 mm, do not need to be ground before the
determination.
Mix the laboratory sample thoroughly before taking the test portion (8.3).
7.2 Products requiring to be ground
lf the laboratory sample does not have the particle size characteristics mentioned in 7.1, it shall be
ground either without pre-conditioning (7.2.1) or with pre-conditioning (7.2.2) as required.
7.2.1 Grinding without pre-conditioning
For products which are not likely to undergo variations in moisture content in the course of grinding
[in general, products with a moisture content between 9.00 % and 15.00 % (m/m) (see 11)], carry out
grinding without pre-conditioning.
Adjust the grinding mill (5.3) to obtain particles of the dimensions indicated in 7.1, grind a small
quantity of the laboratory sample and discard it.
Then quickly grind about 30 g of the laboratory sample, mix with a spatula and proceed immediately as
specified in 8.1.
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7.3 Grinding with pre-conditioning
Products which are likely to undergo changes in moisture content in the course of grinding [in general,
products with a moisture content more than 15.00 % (m/m) or less than 9.00 % (m/m)] shall be
pre-conditioned to bring their moisture content to between 9.00 % (m/m) and 15.00 % (m/m) (see 11)
before grinding.
If the moisture content is greater than 15.00 % (m/m) (the more frequent case, weigh, to the nearest
0.1g, about 100 g of the laboratory sample in the metal boat (5.3), place this in the oven (5.6) controlled
at between 60 °C and 80 °C, and leave it for the time necessary to bring the moisture content to
between 9.00 % (m/m) and 15.00 % (m/m). Take the boat out of the oven and allow it to stand in the
laboratory atmosphere for the time necessary (at least 2 h) for the pre-conditioned sample to return
to the laboratory temperature and for the moisture distribution to be relatively uniform. During this
rest, it must be ensured that no addition or withdrawal of material is made to the contents of the boat.
If necessary, cover it with a sheet of paper but not with a lid that could limit the exchange of moisture
between the air and the grain.
After conditioning, weigh the sample to the nearest 10 mg, then, proceeding rapidly, grind about 30 g of
this product. Mix using a spatula.
If the moisture content is less than 9.00 % (m/m), place about 100 g of the laboratory sample, weighed to
the nearest 10 mg, in a suitable atmosphere (usually that of the laboratory) and leave it until a moisture
content within the limits specified above is obtained.
8 Procedure
8.1 Number of determinations
For each laboratory sample, carry out the determination in duplicate
Carry out one determination on each of the two grinded test portions taken from the laboratory sample,
in accordance with paragraphs 8.2 to 8.5. If the absolute difference between the two results is greater
than the repeatability limit given in Clause 10, repeat the determination until the requirements are met.
8.2 Taring of capsules
For each sample, dry and tare to the nearest 0.001 g two capsules (5.5) beforehand. For each capsule,
note the tare t.
8.3 Test portion
Weigh rapidly, to the nearest 0.001 mg, approximately 8 g +/- 1 g of the test sample (7.1.1, 7.2.1 to or
7.2.2 as appropriate) into the capsule (5.4). Note the mass m’ .
0
8.4 Drying
Place the open dish containing the test portion, and the lid, in the oven (5.7) controlled between 130 °C
and 133 °C and leave it for 4 h +/- 5 min.
Never place moist products in an oven containing test portions at the end of dehydration, as this will
result in partial rehydration of the latter.
Do not open the oven door during drying nor introduce new wet test samples before removing the dry
test portions as this would rehydrate them.
At the end of the drying time and proceeding rapidly, take the dish out of the oven, cover it and place it
in the desiccator (5.8). When several tests are being carried out simultaneously, never place dishes on
top of one another in the desiccator.
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8.5 Weighing
When the dish has cooled to laboratory temperature (generally between 30 min and 45 min after it has
been placed in the desiccator), weigh it to the nearest 0.001 mg. Note the mass m’ .
1
9 Expression of results
9.1 Method of calculation and formulae
The moisture content, w , expressed as a percentage by mass of the product has received, is given by
H2O
the following formulae:
a) without pre-conditioning:
100
w = ()mm−
H2O
01
m
0
where
m = m’ - t is the mass, in grams, of the test portion (8.3) ;
o 0
m = m’ - t is the mass, in grams, of the test portion after drying (8.5).
1 1
t is the tare of the capsule, in grams (8.2)
b) with pre-conditioning:
m3 100
 
w = ()mm01− +−mm23
H2O
 
m0 m2
 
mm13
 
w = 100 1−
 
H2O
mm02
 
where
m and m have the same signification as in 9.1
o 1
m is the mass, in grams, of the sample before conditioning (7.2.2);
2
m is the mass, in grams, of the sample after conditioning (7.2.2).
3
Take as the result the arithmetic mean of the two values obtained, provided that the requirement for
repeatability (see 10.2) is satisfied. If it is not, repeat the determinations.
Express the result to the second decimal place.
10 Precision
10.1 Inter-laboratory test
10.2 The details of an inter-laboratory test relating to the precision of the method are
summarized in Appendix B. Values from this test can only be applied to water content ranges
from 11.90 to 39.20 % and the studied matrix (maize).Repeatability
The absolute difference between two independent individual test results, obtained using the same
method on identical material tested in the same laboratory by the same operator using the same
apparatus and within a short time interval, shall be exceed in no more than 5% of cases the repeatability
limit r.
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r = 2.8 S
r
r = 2.8 x 0.07 = 0.19
for maize with water content between 11.90 and 39.20%
10.3 Reproductibility
Reproductibility is the absolute difference between two individual test results, obtained with the same
method on identical material tested in different laboratories by differnet operators using different
equipment.
In practice, it is not appropriate to compare the results of 2 laboratories if the related test imposes
repeatability conditions.
The appropriate comparison tool is the critical difference as described in paragraphs 10.4 and 10.5.
10.4 Comparison of two groups of measurements in a laboratory
The critical difference (DCr) is the difference between two averaged values obtained from two test
results under repeatability conditions. Each result being the average of two values (see 8.4), the
comparison of the two water content results must be done using the critical difference.
The critical difference (DCr) between two averaged values each obtained from two test results under
repeatability conditions is equal to:
1 1 1
DC =+28,,S ==28SS19, 8 = 0,14
rr rr
2nn2 2
12
where
S is the standard deviation of repeatability ;
r
n and n are the number of test results corresponding to each averaged values.
1 2
10.5 Comparison of two groups of measurements in two laboratories
The critical difference (DCr) between two averaged values each obtained in two different laboratories
from two test results under repeatability conditions is equal to:
1 1
22 22
CD =−28,(SS 1−− ),=−28 SS05, = 0,68
RR rR r
2nn2
12
where
S is the standard deviation of repeatability ;
r
S is the standard deviation of reproductibility ;
R
n and n are the number of test results corresponding to each averaged values.
1 2
10.6 Uncertainty
It is possible to evaluate measurement uncertainties using data obtained from studies carried out
in accordance with ISO 5725-2: the reproducibility standard deviation obtained during an inter-
laboratory test is a valid basis to assess measurement uncertainty because, by definition, uncertainty
characterizes the dispersion of values that can be reasonably attributed to the parameter.
The calculated expanded standard uncertainty should be ≤ ± 2 reproducibility standard deviations.
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10.7 Note
Compared to the absolute method (see Annex A), the results generally differ from less than 0.15 g of
water per 100 g of samples.
11 Notes on procedure
11.1 The range of moisture contents for which conditioning products before grinding has to be realized
corresponds to a laboratory atmosphere of temperature 20 +/- 2°C and relative humidity 45 % to 75 %.
It should be modified for different atmospheric conditions.
11.2 The conditioning and grinding carried out on 100 g and 30 g respectively for a test portion of 8 g
are intended to provide a more representative sample. A direct sampling for grinding of only 8 g would
correspond to an insufficient quantity of initial product to be representative and would lead to too great
a dispersion of the results.
12 Test report
The test report shall contain at least the following information:
a) all information neccessary for the identification of the sample (type of sample, origin and
designation of the sample);
b) a reference to this international standard;
c) the date and type of sampling procedure (if known);
d) the date of receipt;
e) the date of test;
f) the test result and the unit in which it has been expressed
g) any operation not specified in the method or regarded as optional, which might have affect
...

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