ISO 5537:2023

INTERNATIONAL ISO
STANDARD 5537
IDF 26
Second edition
2023-07
Dried milk and dried milk products —
Determination of moisture content
(reference method)
Lait sec et produits à base de lait sec — Détermination du taux
d’humidité (méthode de référence)
Reference numbers
IDF 26:2023(E)
IDF 26:2023(E)
© ISO and IDF 2023
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Published in Switzerland
ii
IDF 26:2023(E)
Contents Page
Forewords .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Sampling . 3
7 Preparation of test sample . 3
8 Procedure .3
8.1 Preparation of column . 3
8.2 Preparation of test portion . 3
8.3 Determination . 4
9 Calculation and expression of results . 4
9.1 Calculation . 4
9.2 Expression of test results. 4
10 Precision . 4
10.1 Interlaboratory test . . 4
10.2 Repeatability . 5
10.3 Reproducibility . . 5
11 Test report . 5
Annex A (informative) Drying apparatus. 6
Annex B (informative) Precision data . 7
Bibliography . 9
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IDF 26:2023(E)
Forewords
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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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).
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www.iso.org/iso/foreword.html.
This document 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 the European
Committee for Standardization (CEN) Technical Committee CEN/TC 302, Milk and milk products -
Methods of sampling and analysis, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement). It is being published jointly by ISO and IDF.
This second edition cancels and replaces the first edition (ISO 5537 | IDF 26:2004), which has been
technically revised to add precision data for additional matrices.
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
IDF 26:2023(E)
IDF (the International Dairy Federation) is a non-profit private sector organization representing the
interests of various stakeholders in dairying at the global level. IDF members are organized in National
Committees, which are national associations composed of representatives of dairy-related national
interest groups including dairy farmers, dairy processing industry, dairy suppliers, academics and
governments/food control authorities.
ISO and IDF collaborate closely on all matters of standardization relating to methods of analysis
and sampling for milk and milk products. Since 2001, ISO and IDF jointly publish their International
Standards using the logos and reference numbers of both organizations.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. IDF 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.
This document was prepared by the IDF Standing Committee on Analytical Methods for Composition and
ISO Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is
being published jointly by ISO and IDF.
The work was carried out by the IDF/ISO Action Team C54 of the Standing Committee on Analytical
Methods for Composition under the aegis of its project leaders Dr H. van den Bijgaart (NL) and Mrs F. de
Boer (NL).
v
INTERNATIONAL STANDARD
IDF 26:2023(E)
Dried milk and dried milk products — Determination of
moisture content (reference method)
WARNING — The use of this document can involve the use of hazardous materials, operations
and equipment. This document does not purport to address all the safety risks associated with
its use. It is the responsibility of the user of this document to establish appropriate safety and
health practices and determine the applicability of local regulatory limitations prior to use.
1 Scope
This document specifies a method for the determination of the moisture content of all types of dried
milk and dried milk products.
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 terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
moisture content
mass fraction of substances determined by the procedure specified in this document
Note 1 to entry: The moisture content is expressed as a percentage by mass.
4 Principle
A test portion is dried in a drying oven set at 87 °C for 5 h while dry air is passed through the test
portion. The loss of mass of the test portion (which is related to the content of “non-chemically bound”
water) is determined.
5 Apparatus
The usual laboratory apparatus and, in particular, the following shall be used.
5.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg.
5.2 Drying oven, capable of being maintained at 87 °C ± 1 °C throughout the working space, with
forced ventilation, thermostatically controlled, with the following equipment (see also Figure A.1).
5.2.1 Metal block, provided with channels of diameter 4,3 mm for holding the columns (5.4) in the
drying oven.
IDF 26:2023(E)
5.2.2 Copper tubes, of length 1 500 mm, of internal diameter 2 mm, connected to the metal block in
the drying oven.
5.2.3 Constant pressure regulator, provided with restrictors, capable of delivering 33 ml/
min ± 2 ml/min of dry air to each column in the drying oven.
5.2.4 Tube, made of polycarbonate, of length 350 mm, of diameter 40 mm, filled with silica gel with
hygrometric indicator.
The silica gel should have been dried at 150 °C for more than 12 h before use. Using the dry compressed
air (5.11), no colour change of the hygrometric indicator should be noticed.
5.3 Desiccator, containing freshly dried silica gel with hygrometric indicator.
1)
5.4 Columns, made of hard polypropylene (Phenomenex 1213–10211) , of length 90 mm, of internal
1)
diameter 20 mm, provided with two polyethene filters (Phenomenex 1212–1023) , narrowed towards
one end to fit onto the block (5.2.1).
5.5 Synthetic stoppers, of adequate sizes to fit with the columns (5.4), made of soft polyethylene
1)
(Emergo 20273 B198 and 20371 U1) .
5.6 Container, suitable for holding the columns (5.4).
5.7 Container, suitable for holding the synthetic stoppers (5.5).
5.8 Rod, made of polyvinyl chloride (PVC), of length 120 mm, of diameter 18 mm, suitable for placing
the polyethylene filters in the column (5.4).
5.9 Tweezers, suitable for removing the polyethylene filters from the column (5.4).
5.10 Calibrated airflow meter, suitable for measuring a flow rate of 33 ml/min ± 2 ml/min.
Electronic airflow meters, as for instance used with gas chromatography, have been found to be
suitable. For use, the inlet of the airflow meter is connected to a copper tube, with an internal diameter
of 2 mm, that is punctured through the centre of a synthetic stopper (5.5).
5.11 Dry compressed air, minimum pressure of 200
...