FprEN ISO 6540

Maize - Determination of moisture content (on milled grains and on whole grains) (ISO/FDIS 6540:2020)

Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern) (ISO/FDIS 6540:2020)

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/FDIS 6540:2020)

Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO/FDIS 6540:2020)

Standards Content (sample)

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.

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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,
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STANDARDS MAY ON OCCASION HAVE TO
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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)
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© ISO 2020

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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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oSIST prEN ISO 6540:2020
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’ .
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’ .

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
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);
m is the mass, in grams, of the sample after conditioning (7.2.2).

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 = 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
where
S is the standard deviation of repeatability ;
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
where
S is the standard deviation of repeatability ;
S is the standard deviation of reproductibility ;
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

...