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EAS 80-4 (2006) (English): Butter
Methods of chemical analysis Part 4:
Determination of salt content

EAS 80-4:2006
ICS 67.100

EAST AFRICAN STANDARD
Butter ⎯ Methods of chemical analysis ⎯ Part 4:
Determination of salt content

EAST AFRICAN COMMUNITY

© EAC 2006

First Edition 2006

EAS 80-4:2006
Foreword
Development of the East African Standards has been necessitated by the need for harmonizing
requirements governing quality of products and services in East Africa. It is envisaged that through
harmonized standardization, trade barriers which are encountered when goods and services are
exchanged within the Community will be removed.
In order to achieve this objective, the Partner States in the Community through their National Bureaux
of Standards, have established an East African Standards Committee.
The Committee is composed of representatives of the National Standards Bodies in Partner States,
together with the representatives from the private sectors and consumer organizations. Draft East
African Standards are circulated to stakeholders through the National Standards Bodies in the Partner
States. The comments received are discussed and incorporated before finalization of standards, in
accordance with the procedures of the Community.
East African Standards are subject to review, to keep pace with technological advances. Users of the
East African Standards are therefore expected to ensure that they always have the latest versions of
the standards they are implementing.
© East African Community 2006 — All rights reserved*
East African Community
P O Box 1096
Arusha
Tanzania
Tel: 255 27 2504253/8
Fax: 255-27-2504481/2504255
E-Mail: [email protected]
Web: www.each.org

*

ii

© 2006 EAC — All rights of exploitation in any form and by any means reserved worldwide for EAC Partner States’ NSBs.

© EAC 2006 — All rights reserved

INTERNATIONAL
STANDARD

ISO
1738
IDF
12
Third edition
2004-10-15

Butter — Determination of salt content
Beurre — Détermination de la teneur en sel

Reference numbers
ISO 1738:2004(E)
IDF 12:2004(E)
© ISO and IDF 2004

ISO 1738:2004(E)
IDF 12:2004(E)

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© ISO and IDF 2004
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respective
address below.
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Tel. + 41 22 749 01 11
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Web www.iso.org

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Tel. + 32 2 733 98 88
Fax + 32 2 733 04 13
E-mail [email protected]
Web www.fil-idf.org

Published in Switzerland

ii

© ISO and IDF 2004 – All rights reserved

ISO 1738:2004(E)
IDF 12:2004(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 1738IDF 12 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,
Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International.
It is being published jointly by ISO and IDF and separately by AOAC International.
This edition of ISO 1738IDF 12 cancels and replaces ISO 1738:1997, of which it constitutes a minor revision.

© ISO and IDF 2004 – All rights reserved

iii

ISO 1738:2004(E)
IDF 12:2004(E)

Foreword
IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National
Committee in every member country. Every National Committee has the right to be represented on the IDF
Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in
the development of standard methods of analysis and sampling for milk and milk products.
Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the
National Committees for voting. Publication as an International Standard requires approval by at least 50 % of
the National Committees casting a vote.
ISO 1738IDF 12 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,
Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International.
It is being published jointly by ISO and IDF and separately by AOAC International.
All work was carried out by the Joint ISO/IDF/AOAC Group of Experts on Minerals and minor compounds
(E602), under the aegis of its chairman, Mr G. Bråthen (NO).
This edition of ISO 1738IDF 12 cancels and replaces IDF 12C:2000, of which it constitutes a minor revision.

iv

© ISO and IDF 2004 – All rights reserved

INTERNATIONAL STANDARD

ISO 1738:2004(E)
IDF 12:2004(E)

Butter — Determination of salt content

1

Scope

This International Standard specifies a method for the determination of the salt content of butter. The method
is applicable to all types of butter containing more than 0,1 % (mass fraction) of salt.

2

Normative references

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 385-1:1984, Laboratory glassware — Burettes — Part 1: General requirements
ISO 648, Laboratory glassware — One-mark pipettes
ISO 4788, Laboratory glassware — Graduated measuring cylinders

3

Terms and definitions

For the purposes of this document, the following terms and definitions apply.
3.1
salt content
mass fraction of substances determined by the method specified in this International Standard
NOTE

4

It is expressed as the equivalent content of sodium chloride as a mass fraction in percent.

Principle

A test portion of butter is melted by adding boiling water. The dissolved chlorides in the mixture are titrated
with a solution of silver nitrate, using potassium chromate as indicator (the Mohr procedure).

5

Reagents

Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized
water or water of equivalent purity, free from chlorides.
5.1 Silver nitrate standard volumetric solution (AgNO3), of known concentration in the range 0,08 mol/l
to 0,10 mol/l.
Dissolve an amount of between 13,6 g to 20,4 g of silver nitrate in water which is practically free from carbon
dioxide in a 1 000 ml volumetric flask. Dilute to the mark with water. Calibrate the silver nitrate solution against
100 ml of a solution containing 0,400 g/l of sodium chloride (NaCl), which has previously been dried at 300 °C,

© ISO and IDF 2004 – All rights reserved

1

ISO 1738:2004(E)
IDF 12:2004(E)

following the procedure specified in 9.3.2 and 9.4. Express the concentration of the silver nitrate solution in
moles per litre to four decimals. Store the solution away from direct sunlight.
NOTE
If a solution containing 14,53 g/l (0,085 5 mol/l) of silver nitrate is used, 1 ml of this solution is equivalent to
5 mg of sodium chloride, thus making the calculation of the salt content of the butter easier.

5.2

Potassium chromate indicator solution

Dissolve 50 g of potassium chromate (K2CrO4) in 1 000 ml of water.
WARNING — Hexavalent chromium is a carcinogenic agent.

6

Apparatus

Usual laboratory apparatus and, in particular, the following.
6.1

Analytical balance, capable of being read to the nearest 0,001 g.

6.2

Titration vessel, made of glass, for example, a conical flask or beaker of capacity 250 ml.

6.3

Graduated measuring cylinder, of capacity 100 ml, complying with ISO 4788.

6.4

Pipette, capable of delivering 2,0 ml, complying with ISO 648.

6.5

Burette, of capacity 50 ml, complying with ISO 385:1984, Class B.

6.6 Greaseproof paper or plastic film, chloride free or of sufficiently low chloride content as to not affect
the results. The use of filter paper is not recommended.

7

Sampling

A representative sample should have been sent to the laboratory. It should not have been damaged or
changed during transport or storage.
Sampling is not part of the method specified in this International Standard. A recommended sampling method
is given in ISO 707.
Store the sample in such a way that deterioration and change in composition are prevented.

8

Preparation of test sample

Take a representative sample of butter to be tested.
If the test sample is visibly not homogeneous, or if the history of the test sample (age, storage conditions) is
such that inhomogeneity is to be expected, mix the test sample as follows. Warm the test sample in the
original unopened container, which should be from one-half to two-thirds full, to a temperature that preferably
should not exceed 30 °C. At this temperature the sample will be soft enough to facilitate thorough mixing to a
homogeneous state (either by a mechanical shaker or by hand).
Cool the sample to ambient temperature, continuing to mix until cooling is complete. Immediately after cooling,
open the sample container and stir briefly with a suitable device, for example a spoon or spatula, for no longer
than 10 s before weighing.

2

© ISO and IDF 2004 – All rights reserved

ISO 1738:2004(E)
IDF 12:2004(E)

9
9.1

Procedure
Number of determinations

If it is required to check whether the repeatability limit (11.1) is met, carry out two single determinations in
accordance with 9.2 and 9.3.

9.2

Test portion

Weigh, to the nearest 0,05 g, a test portion of between 4,5 g to 5,5 g either directly into the titration vessel
(6.2) or on a piece of greaseproof paper or plastic film (6.6) which is transferred with the test sample to the
titration vessel. Add 100 ml of boiling water or 100 ml of cold water and heat to boiling. Mix the contents of the
vessel.

9.3

Determination

9.3.1 The titration may be carried out on the hot solution or after cooling. It is essential, however, that each
laboratory standardize its own procedure for the determination by always bringing the contents of the titration
vessel to approximately the same temperature before titration.
The titration should preferably be carried out a temperature of about 50 °C. This temperature may (partially)
prevent coagulation of the butterfat which influences the orange tint.
9.3.2 Cool, while mixing, the contents of the titration vessel to the laboratory standardized temperature. Add
2,0 ml of the potassium chromate indicator (5.2).
Titrate the solution with the silver nitrate solution (5.1), with stirring, until an orange tint is obtained which
persists for 30 s. Record the volume, in millilitres, of silver nitrate used.

9.4

Blank test

Carry out a blank test using all the reagents but omitting the test portion.

10 Calculation and expression of results
10.1 Calculation
10.1.1 Calculate the salt content of butter, w, expressed as a mass fraction in percent, using the following
equation:

w=

5,844 c s (V s − V 0 )
m

%

where
Vs

is the numerical value of the volume, in millilitres, of silver nitrate solution used in the titration of
the test portion (9.3.2);

V0

is the numerical value of the volume, in millilitres, of silver nitrate solution used in the titration of
the blank test (9.4);

cs

is the numerical value of the concentration of the silver nitrate solution, in moles per litre;

m

is the numerical value of the mass, in grams, of the test portion;

© ISO and IDF 2004 – All rights reserved

3

ISO 1738:2004(E)
IDF 12:2004(E)

5,844

is the mass of NaCl equivalent of 1 ml of standard volumetric solution, c(AgNO3) = 1 mol/l,
divided by a factor 10 [obtained by dividing 100 (%) by 1 000 (ml)].

10.1.2 If a solution containing 14,53 g/l of silver nitrate is used and 5 g of the test portion is weighed to the
nearest 0,01 g, the calculation of w, the salt content of butter, may be simplified using the following equation:

V − V0
%
w= s
10
where Vs is the numerical value of the volume, in millilitres, of a silver nitrate solution containing 14,53 g/l of
silver nitrate.

10.2 Expression of results
Round the result to the nearest 0,01 % (mass fraction).

11 Precision
Details of an interlaboratory test on the precision of the method are summarized in Reference [5]. The study
was carried out in accordance with ISO 5725:1986 (now withdrawn). The values derived from this
interlaboratory test may not be applicable to concentration ranges and matrices other than those given.

11.1 Repeatability
The absolute difference between two independent single test results, obtained using the same method on
identical test material in the same laboratory by the same operator using the same equipment within a short
interval of time, will in not more than 5 % of cases be greater than 0,03 % (mass fraction).

11.2 Reproducibility
The absolute difference between two single test results, obtained using the same method on identical test
material in different laboratories with different operators using different equipment, will in not more than 5 % of
cases be greater than 0,05 % (mass fraction).

12 Test report
The test report shall specify:
a)

all information necessary for the complete identification of the sample;

b)

the sampling method used, if known;

c)

the test method used, with reference to this International Standard;

d)

all operating details not specified in this International Standard, or regarded as optional, together with
details of any incidents that may have influenced the test result(s);

e)

the test results obtained;

f)

if the repeatability has been checked, the final quoted result obtained.

4

© ISO and IDF 2004 – All rights reserved

ISO 1738:2004(E)
IDF 12:2004(E)

Bibliography

[1]

ISO 707:1997, Milk and milk products — Guidance on sampling1)

[2]

ISO 5725:1986, Precision of test methods — Determination of repeatability and reproducibility for a
standard test method by inter-laboratory tests (now withdrawn)

[3]

ISO 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results — Part 1:
General principles and definitions

[4]

ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2:
Basic method for the determination of repeatability and reproducibility of a standard measurement
method

[5]

BRÅTHEN, G. and MARTENS, R. Bulletin of the IDF, 235, 1988, pp. 20-33

1)

Equivalent to IDF 50.

© ISO and IDF 2004 – All rights reserved

5

ISO 1738:2004(E)
IDF 12:2004(E)

ICS 67.100.20
Price based on 5 pages

© ISO and IDF 2004 – All rights reserved

EAS 80-4:2006

© EAC 2006 — All rights reserved