EN ISO 1735:2004

SLOVENSKI STANDARD
01-januar-2005
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Cheese and processed cheese products - Determination of fat content - Gravimetric
method (Reference method) (ISO 1735:2004)
Käse und Schmelzkäse - Bestimmung des Fettgehaltes - Gravimetrisches Verfahren
(Referenzverfahren) (ISO 1735:2004)
Fromages et fromages fondus - Détermination de la teneur en matiere grasse - Méthode
gravimétrique (Méthode de référence) (ISO 1735:2004)
Ta slovenski standard je istoveten z: EN ISO 1735:2004
ICS:
67.100.30 Sir Cheese
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 1735
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2004
ICS 67.100.30
English version
Cheese and processed cheese products - Determination of fat
content - Gravimetric method (Reference method) (ISO
1735:2004)
Fromages et fromages fondus - Détermination de la teneur
en matière grasse - Méthode gravimétrique (Méthode de
référence) (ISO 1735:2004)
This European Standard was approved by CEN on 1 June 2004.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 1735:2004: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 1735:2004) has been prepared by Technical Committee ISO/TC 34
"Agricultural food products" in collaboration with Technical Committee CEN/TC 302 "Milk and milk
products - Methods of sampling and analysis", the secretariat of which is held by NEN.

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 January 2005, and conflicting national
standards shall be withdrawn at the latest by January 2005.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Cyprus,
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 1735:2004 has been approved by CEN as EN ISO 1735:2004 without any
modifications.
INTERNATIONAL ISO
STANDARD 1735
IDF
Third edition
2004-07-01
Cheese and processed cheese
products — Determination of fat
content — Gravimetric method
(Reference method)
Fromage et fromage fondu — Détermination de la teneur en matière
grasse — Méthode gravimétrique (Méthode de référence)

Reference numbers
ISO 1735:2004(E)
IDF 5:2004(E)
©
ISO and IDF 2004
ISO 1735:2004(E)
IDF 5:2004(E)
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Published in Switzerland
ii © ISO and IDF 2004 – All rights reserved

ISO 1735:2004(E)
IDF 5:2004(E)
Contents Page
Foreword. iv
Foreword. v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Principle. 1
5 Reagents. 1
6 Apparatus. 2
7 Sampling. 3
8 Preparation of test sample. 3
9 Procedure. 4
9.1 Test portion. 4
9.2 Blank test. 4
9.3 Preparation of fat-collecting vessel . 4
9.4 Determination. 5
10 Calculation and expression of results . 7
10.1 Calculation. 7
10.2 Expression of results. 7
11 Precision. 8
11.1 Interlaboratory test. 8
11.2 Repeatability. 8
11.3 Reproducibility. 8
12 Test report. 8
Annex A (normative) Additional procedures . 9
Annex B (informative) Alternative procedure using fat-extraction tubes with siphon or wash-bottle
fittings . 11
Annex C (informative) Interlaboratory test. 14
Bibliography . 15

ISO 1735:2004(E)
IDF 5:2004(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 International Standard may be the
subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 1735IDF 5 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 1735IDF 5 cancels and replaces ISO 1735:1987, which has been technically revised.
iv © ISO and IDF 2004 – All rights reserved

ISO 1735:2004(E)
IDF 5:2004(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
IDF National Committees casting a vote.
International Standard ISO 1735IDF 5 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 Action Team, Fat, of the Standing Committee, Main
components in milk, under the aegis of its project leader, Mr G.J. Beutick (NL).
This edition of ISO 1735IDF 5 cancels and replaces IDF 5B:1986, which has been technically revised.

ISO 1735:2004(E)
INTERNATIONAL STANDARD
IDF 5:2004(E)
Cheese and processed cheese products — Determination of fat
content — Gravimetric method (Reference method)
WARNING — The use of ISO 1735IDF 5 may involve hazardous materials, operations and equipment.
This standard does not purport to address all the safety problems associated with its use. It is the
responsibility of the user of this standard to establish safety and health practices and to determine the
applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies the reference method for the determination of the fat content of all types
of cheese and processed cheese products having lactose contents of below 5 % (mass fraction) of non-fat
solids.
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 3889:1977, Milk and milk products — Determination of fat content — Mojonnier-type fat extraction flasks
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
fat content of cheese and processed cheese products
mass fraction of substances determined by the procedure specified in this International Standard
NOTE The fat content is expressed as a percentage by mass.
4 Principle
A test portion is digested with hydrochloric acid then ethanol is added. The acid-ethanolic solution is extracted
with diethyl ether and light petroleum and the solvents are removed by distillation or evaporation. The mass of
the substances extracted is determined. This is usually known as the Schmid-Bondzynski-Ratzlaff principle.
5 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized
water or water of equivalent purity. The reagents shall leave no appreciable residue when the determination is
carried out by the method specified (see 5.1).
ISO 1735:2004(E)
IDF 5:2004(E)
5.1 Purity of reagents
To test the quality of the reagents, carry out a blank test as specified in 9.2. Use an empty fat-collecting vessel,
prepared as specified in 9.3, for mass control purposes.
The reagents shall leave no residue greater than 0,5 mg (see A.1 of Annex A).
If the residue of the complete reagent blank test is greater than 0,5 mg, determine the residue of the solvents
separately by distilling 100 ml of the diethyl ether and light petroleum, respectively. Use an empty control
vessel to obtain the real mass of residue, which shall not exceed 0,5 mg. Replace unsatisfactory reagents or
solvents, or redistil solvents.
Very occasionally, the solvents may contain volatile matter which is strongly retained in fat. If there are
indications of the presence of such substances, carry out blank tests on all the reagents and for each solvent
using a fat-collecting vessel with about 1 g of anhydrous butterfat. If necessary, redistil solvents in the
presence of 1 g of anhydrous butterfat per 100 ml of solvent. Use the solvents only shortly after the
redistillation.
5.2 Concentrated hydrochloric acid, ρ (HCl) = 1,18 g/ml.

5.3 Dilute hydrochloric acid, ρ (HCl) = 1,125 g/ml approximately.
Dilute 675 ml of concentrated hydrochloric acid (5.2) to 1 000 ml with water and mix.
5.4 Ethanol, or ethanol denatured by methanol, containing at least 94 % (volume fraction) of ethanol
(see A.5).
5.5 Diethyl ether, free from peroxides (see A.4), complying with the requirements for the blank test.
5.6 Light petroleum, with any boiling range between 30 °C and 60 °C or, as equivalent, pentane
[CH (CH ) CH ], with a boiling point of 36 °C.
3 2 3 3
NOTE The use of pentane is recommended due to its higher purity and constant quality.
5.7 Mixed solvent, prepared shortly before use by mixing equal volumes of diethyl ether (5.5) and light
petroleum (5.6).
6 Apparatus
WARNING — Since the determination involves the use of volatile flammable solvents, electrical
apparatus employed may be required to comply with legislation relating to the hazards in using such
solvents.
Usual laboratory equipment and, in particular, the following.
6.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg.
6.2 Centrifuge, capable of holding the fat-extraction flasks or tubes (6.6) and capable of spinning at a
−1 −1
rotational frequency of 500 min to 600 min to produce a radial acceleration of 80 g to 90 g at the outer end
of the flasks or tubes.
NOTE The use of the centrifuge is optional but recommended (see 9.4.7).
6.3 Distillation or evaporation apparatus, capable of distilling the solvents and ethanol from the flasks or
capable of evaporating from beakers and dishes (9.4.13) at a temperature not exceeding 100 °C.
2 © ISO and IDF 2004 – All rights reserved

ISO 1735:2004(E)
IDF 5:2004(E)
6.4 Drying oven, electrically heated, with ventilation port(s) fully open, capable of being maintained at a
temperature of 102 °C ± 2 °C throughout the working space. The oven shall be fitted with a suitable
thermometer.
6.5 Boiling water bath or hot plate.
6.6 Fat-extraction flasks, Mojonnier-type, as specified in ISO 3889.
NOTE It is also possible to use fat-extraction tubes, with siphon or wash-bottle fittings, but the procedure is slightly
different then. The alternative procedure is specified in Annex B.
The flasks shall be provided with good quality bark corks or stoppers of other material unaffected by the
reagents used. Extract bark corks with the diethyl ether (5.5), then place in water at 60 °C or more for at least
15 min. Then allow them to cool in the water so that they are saturated when used.
6.7 Rack, capable of holding the fat-extraction flasks (or tubes) (6.6).
6.8 Wash bottle, suitable for use with the mixed solvent (5.7). Do not use plastic wash bottles.
6.9 Fat-collecting vessels, for example: boiling flasks, flat-bottomed, of capacity 125 ml to 250 ml; conical
flasks, of capacity 250 ml; or metal dishes made of stainless steel, flat-bottomed, of diameter 80 mm to
100 mm, of height approximately 50 mm. Do not use aluminium dishes.
6.10 Boiling aids, fat-free, of non-porous porcelain or silicon carbide (optional if using metal dishes).
6.11 Measuring cylinders, of capacities 5 ml and 25 ml.
6.12 Pipettes, graduated, to deliver 10 ml.
6.13 Tongs, made of metal, capable of holding flasks, beakers or dishes.
6.14 Sheets of cellulose film, unlacquered, soluble in hydrochloric acid, of thickness 0,03 mm to 0,05 mm,
of dimensions 50 mm × 75 mm approximately. The sheets shall be inert under the test conditions.
6.15 Appropriate grinding or grating device, easy to clean, for preparing the test sample.
7 Sampling
It is important that the laboratory receive a test sample which is truly representative and has not 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.
The test samples shall be kept at a temperature of between 0 °C and 20 °C from the time of sampling to the
time of commencing the procedure.
8 Preparation of test sample
Prior to analysis, remove the rind, the smear or the mouldy surface layer of the cheese in such a way as to
obtain a test sample representative of the cheese as it is usually consumed.
Grind or grate the test sample by using an appropriate grinding or grating device (6.15). Mix the ground mass
quickly and, if necessary for semi-hard and hard cheeses, grind it a second time and again mix thoroughly.
Preferably, cut hard and semi-hard cheeses into cubes of about 15 mm × 15 mm. Mix the cubes by shaking in
a container. Grind or grate the test sample as specified before. Clean the device after preparing each sample.
ISO 1735:2004(E)
IDF 5:2004(E)
If the test sample cannot be ground or grated, mix it thoroughly by intensive kneading, for example with a
pestle in a mortar. Care should be taken to avoid moisture loss.
Store the test sample in an airtight container until commencing the analysis, which shall be carried out as
soon as possible after grinding.
If, however, a delay is unavoidable, take all precautions to ensure proper preservation of the test sample.
When refrigerated, bring the test sample to room temperature. Thoroughly mix the sample to obviate the well-
documented transfer of moisture within the cheese that occurs during cooling and warming. Ensure that any
condensation of moisture on the inside surface of the container is thoroughly and uniformly re-incorporated
into the test sample. Do not examine ground cheese showing unwanted mould growth or signs of deterioration.
All sample preparation should be carried out in a manner which minimizes moisture loss. Such moisture loss
will have the effect of increasing the apparent fat content.
9 Procedure
NOTE An alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings is specified in Annex B.
9.1 Test portion
Mix the test sample (Clause 8) by gently stirring. Immediately weigh, to the nearest 1 mg, directly or by
difference, 1 g to 3 g of test sample into a fat-extraction flask (6.6), a 100 ml beaker or flask.
Weigh an amount of 3 g for cheeses having a mass fraction of fat of up to 30 %. For cheeses having a mass
fraction of fat of more than 30 %, adapt the mass of the test portion so as to obtain a mass of extracted fat of
between 750 mg and 1 000 mg.
The test portion may also be weighed on a sheet of cellulose film (6.14), which is subsequently folded and
introduced into the chosen vessel. Deliver the test portion as completely as possible into the lower (small) bulb
of the fat-extraction flask.
9.2 Blank test
Carry out a blank test simultaneously with the determination, using the same procedure and same reagents
but omitting the test portion (see A.2).
If the value obtained in the blank test regularly exceeds 1,0 mg, check the reagents if this has not been done
recently (see 5.1). Corrections for values of more than 2,5 mg in the blank test shall be reported in the test
report.
9.3 Preparation of fat-collecting vessel
Dry a fat-collecting vessel (6.9) with a few boiling aids (6.10) in the drying oven (6.4) set at 102 °C for 1 h.
NOTE Boiling aids are desirable to promote gentle boiling during the subsequent removal of solvent, especially in the
case of glass vessels; their use is optional in the case of metal dishes.
Allow the fat-collecting vessel to cool (protected from dust) to the te
...