Skimmed milk, whey and buttermilk - Determination of fat content - Gravimetric method (Reference method)(ISO 7208:2008)

ISO 7208|IDF 22:2008 specifies the reference method for the determination of the fat content of liquid skimmed milk, whey and buttermilk. It is a particularly accurate gravimetric method especially for the purpose of establishing the operating efficiency of cream separators.
ISO 7208|IDF 22:2008 also specifies the reference method for establishing correction tables for procedures with skimmed milk butyrometers.

Magermilch, Molke und Buttermilch - Bestimmung des Fettgehaltes - Gravimetrisches Verfahren (Referenzverfahren) (ISO 7208:2008)

Diese Internationale Norm legt das Referenzverfahren für die Bestimmung des Fettgehaltes von flüssiger Magermilch, Molke und Buttermilch fest. Dabei handelt es sich um ein besonders genaues gravimetrisches Verfahren, insbesondere um die Wirksamkeit von Rahmseparatoren festzustellen.
Diese Internationale Norm legt außerdem das Referenzverfahren zum Erstellen von Korrekturtabellen für Bestimmungen mit Magermilch-Butyrometern fest.
ANMERKUNG   Das in ISO 1211|IDF 1 [2] festgelegte Verfahren ist geeignet, falls eine hohe Bestimmungsgenauigkeit nicht erforderlich ist.

Lait écrémé, sérum et babeurre - Détermination de la teneur en matière grasse - Méthode gravimétrique (Méthode de référence) (ISO 7208:2008)

L'ISO 7208|FIL 22:2008 spécifie la méthode de référence pour la détermination de la teneur en matière grasse du lait liquide écrémé, du sérum et du babeurre. Il s'agit d'une méthode gravimétrique particulièrement précise en vue de déterminer l'efficacité de l'opération d'écrémage.
L'ISO 7208|FIL 22:2008 spécifie également la méthode de référence permettant d'établir des tables de correction pour les techniques utilisant les butyromètres à lait écrémé.

Posneto mleko, sirotka in pinjenec - Določevanje maščobe - Gravimetrijska metoda (Referenčna metoda) (ISO 7208:2008)

General Information

Status
Withdrawn
Publication Date
30-Jan-2009
Withdrawal Date
29-Apr-2009
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
15-Oct-2008
Due Date
18-Oct-2009
Completion Date
15-Oct-2008

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SLOVENSKI STANDARD
SIST EN ISO 7208:2009
01-februar-2009
1DGRPHãþD
SIST EN ISO 7208:2000
3RVQHWRPOHNRVLURWNDLQSLQMHQHF'RORþHYDQMHPDãþREH*UDYLPHWULMVND
PHWRGD 5HIHUHQþQDPHWRGD  ,62

Skimmed milk, whey and buttermilk - Determination of fat content - Gravimetric method

(Reference method) (ISO 7208:2008)

Magermilch, Molke und Buttermilch - Bestimmung des Fettgehaltes - Gravimetrisches

Verfahren (Referenzverfahren) (ISO 7208:2008)
Lait écrémé, sérum et babeurre - Détermination de la teneur en matière grasse -
Méthode gravimétrique (Méthode de référence) (ISO 7208:2008)
Ta slovenski standard je istoveten z: EN ISO 7208:2008
ICS:
67.100.10 0OHNRLQSUHGHODQLPOHþQL Milk and processed milk
SURL]YRGL products
SIST EN ISO 7208:2009 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 7208:2009
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SIST EN ISO 7208:2009
EUROPEAN STANDARD
EN ISO 7208
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2008
ICS 67.100.10 Supersedes EN ISO 7208:1999
English Version
Skimmed milk, whey and buttermilk - Determination of fat
content - Gravimetric method (Reference method)(ISO
7208:2008)

Lait écrémé, sérum et babeurre - Détermination de la Magermilch, Molke und Buttermilch - Bestimmung des

teneur en matière grasse - Méthode gravimétrique Fettgehaltes - Gravimetrisches Verfahren

(Méthode de référence) (ISO 7208:2008) (Referenzverfahren) (ISO 7208:2008)
This European Standard was approved by CEN on 14 October 2008.

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 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 Management Centre has the same status as the

official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, 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

© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7208:2008: E

worldwide for CEN national Members.
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SIST EN ISO 7208:2009
EN ISO 7208:2008 (E)
Contents Page

Foreword..............................................................................................................................................................3

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SIST EN ISO 7208:2009
EN ISO 7208:2008 (E)
Foreword

This document (EN ISO 7208:2008) 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 April 2009, and conflicting national standards shall be withdrawn at the

latest by April 2009.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 7208:1999.

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, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
Endorsement notice

The text of ISO 7208:2008 has been approved by CEN as an EN ISO 7208:2008 without any modification.

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SIST EN ISO 7208:2009
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SIST EN ISO 7208:2009
INTERNATIONAL ISO
STANDARD 7208
IDF
Third edition
2008-10-15
Skimmed milk, whey and buttermilk —
Determination of fat content —
Gravimetric method (Reference method)
Lait écrémé, sérum et babeurre — Détermination de la teneur en
matière grasse — Méthode gravimétrique (Méthode de référence)
Reference numbers
ISO 7208:2008(E)
IDF 22:2008(E)
ISO and IDF 2008
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)
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© ISO and IDF 2008

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.
ISO copyright office International Dairy Federation

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Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88
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Published in Switzerland
ii © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)
Contents Page

Foreword............................................................................................................................................................ iv

Foreword............................................................................................................................................................. v

1 Scope ......................................................................................................................................................1

2 Normative references ............................................................................................................................1

3 Terms and definitions ...........................................................................................................................1

4 Principle..................................................................................................................................................2

5 Reagents.................................................................................................................................................2

6 Apparatus ...............................................................................................................................................2

7 Sampling.................................................................................................................................................3

8 Preparation of test sample....................................................................................................................4

9 Procedure ...............................................................................................................................................4

9.1 Test portion ............................................................................................................................................4

9.2 Blank tests..............................................................................................................................................4

9.3 Preparation of fat-collecting vessel.....................................................................................................5

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 (informative) Notes on procedures ....................................................................................................9

Annex B (informative) Alternative procedure using fat-extraction tubes with siphon or wash-bottle

fittings ...................................................................................................................................................11

Bibliography ......................................................................................................................................................14

© ISO and IDF 2008 – All rights reserved iii
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(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 7208⎪IDF 22 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,

Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and

IDF.

This third edition of ISO 7208⎪IDF 22 cancels and replaces the second edition (ISO 7208:1999), of which it

constitutes a minor revision.
iv © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)
Foreword

IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide.

IDF membership comprises National Committees in every member country as well as regional dairy

associations having signed a formal agreement on cooperation with IDF. All members of IDF have the right to

be represented at the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO 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 IDF National Committees casting a vote.

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.

ISO 7208⎪IDF 22 was prepared by the International Dairy Federation (IDF) and Technical Committee

ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF

and ISO.

All work was carried out by the Joint ISO-IDF Action Team Fat of the Standing Committee on Main

components in milk under the aegis of its project leader, Mr G.J. Beutick (NL).

This edition of ISO 7208⎪IDF 22 cancels and replaces IDF 22:1987, of which it constitutes a minor revision.

© ISO and IDF 2008 – All rights reserved v
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SIST EN ISO 7208:2009
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
INTERNATIONAL STANDARD
IDF 22:2008(E)
Skimmed milk, whey and buttermilk — Determination of fat
content — Gravimetric method (Reference method)

WARNING — The use of this International Standard may involve hazardous materials, operations and

equipment. This International Standard does not purport to address all the safety problems associated

with its use. It is the responsibility of the user of this International Standard to establish safety and

health practices and 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 liquid

skimmed milk, whey and buttermilk. It is a particularly accurate gravimetric method especially for the purpose

of establishing the operating efficiency of cream separators.

This International Standard also specifies the reference method for establishing correction tables for

procedures with skimmed milk butyrometers.
[2]

NOTE When a high accuracy of determination is not required, the method specified in ISO 1211⎪IDF 1 is suitable.

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 835, Laboratory glassware — Graduated pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks

ISO 3889⏐IDF 219, Milk and milk products — Specification of Mojonnier-type fat extraction flasks

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
fat content of skimmed milk, whey and buttermilk

mass fraction of substances determined by the procedure specified in this International Standard

NOTE The fat content is expressed as a percentage mass fraction.
© ISO and IDF 2008 – All rights reserved 1
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)
4 Principle

An ammoniacal ethanolic solution of a test portion is extracted with diethyl ether and light petroleum. The

solvents are removed by distillation or evaporation. The mass of the substances extracted is determined.

NOTE This is usually known as the Röse-Gottlieb principle.
5 Reagents

Use only reagents of recognized analytical grade, unless otherwise specified, and only 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 9.2.2).

5.1 Ammonia solution, containing a mass fraction of NH of approximately 25 % (ρ = 910 g/l).

3 20

NOTE If ammonia solution of this concentration is not available, a more concentrated solution of known concentration

may be used (see 9.4.2).

5.2 Ethanol (C H OH), or ethanol denatured by methanol, containing a volume fraction of ethanol of at

2 5
least 94 %. (See Clause A.5.)
5.3 Congo red solution

Dissolve 1 g of Congo red (C H N Na O S ) in water in a 100 ml one-mark volumetric flask (6.14). Make

32 22 6 2 6 2
up to the mark with water.

NOTE The use of this solution, which allows the interface between the solvent and aqueous layers to be seen more

clearly, is optional (see 9.4.3). Other aqueous indicator solutions can be used provided that they do not affect the result of

the determination.

5.4 Diethyl ether (C H OC H ), free from peroxides (see Clause A.3), containing no more than 2 mg/kg of

2 5 2 5

antioxidants, and complying with the requirements for the blank test (see 9.2.2, Clauses A.1 and A.4).

WARNING — The use of diethyl ether can lead to hazardous situations. Observe current safety

precautions for handling, use, and disposal.

5.5 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 and complying with the requirements for the blank test (see

3 2 3 3
9.2.2, Clauses A.1 and A.4).

The use of pentane is recommended because of its higher purity and consistent quality.

5.6 Mixed solvent.

Shortly before use, mix equal volumes of diethyl ether (5.4) and light petroleum (5.5).

6 Apparatus

WARNING — Since the determination involves the use of volatile flammable solvents, all electrical

apparatus employed shall 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.

2 © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)

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 80g to 90g at the outer end

of the flasks or tubes.
The use of the centrifuge is optional but recommended (see 9.4.6).

6.3 Distillation or evaporation apparatus, for distilling the solvents and ethanol from the boiling or conical

flasks, or evaporating from beakers and dishes (see 9.4.13) at a temperature not exceeding 100 °C.

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 its working space.
The oven shall be fitted with a suitable thermometer.

6.5 Water bath, capable of being maintained at a temperature of between 35 °C and 40 °C.

6.6 Mojonnier-type fat-extraction flasks, as specified in ISO 3889⏐IDF 219.

NOTE It is also possible to use fat-extraction tubes, with siphon or wash-bottle fittings, but then the procedure is

different. The alternative procedure is given in Annex B.

The fat-extraction flasks shall be provided with good quality cork bungs or stoppers of other material (e.g.

silicone rubber or polytetrafluoroethylene) unaffected by the reagents used. Cork bungs shall be extracted

with the diethyl ether (5.4), kept in water at a temperature of 60 °C or more for at least 15 min, and shall then

be allowed to cool in the water so that they are saturated when used.
6.7 Rack, for holding the fat-extraction flasks (or tubes) (6.6).
6.8 Wash bottle, suitable for use with the mixed solvent (5.6).
A plastics wash bottle shall not be used.

6.9 Fat-collecting vessels, such as boiling flasks (flat-bottomed), of capacities 125 ml to 250 ml, conical

flasks, of capacity 250 ml, or metal dishes.

If metal dishes are used, they shall be of stainless steel, flat-bottomed with a diameter of 80 mm to 100 mm

and a height of approximately 50 mm.

6.10 Boiling aids, fat-free, of non-porous porcelain or silicon carbide (optional when metal dishes are used).

6.11 Measuring cylinders, of capacities 5 ml and 25 ml, complying with the requirements of ISO 4788,

class A, or any other apparatus suitable for the product concerned.

6.12 Pipettes, graduated, of capacity 10 ml, complying with the requirements of ISO 835, class A.

6.13 Tongs, made of metal, for holding flasks, beakers or dishes.

6.14 Volumetric flask, one-mark, of capacity 100 ml, complying with the requirements of ISO 1042, class A.

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

[1]
is given in ISO 707⎪IDF 50 .

Store laboratory samples at a temperature between 2 °C and 6 °C from the time of sampling to the time of

commencing the procedure.
© ISO and IDF 2008 – All rights reserved 3
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)
8 Preparation of test sample

Warm the test sample to a temperature between 35 °C and 40 °C by means of the water bath (6.5), if

necessary. Gently mix the test sample thoroughly by repeatedly inverting the sample bottle without causing

frothing or churning. Cool the test sample quickly to approximately 20 °C.
NOTE A reliable value for the fat content cannot be expected:
a) if the milk is churned;
b) when a distinct smell of free fatty acids is perceptible;

c) if during or after preparation of the test sample, white particles are visible on the walls of the sample bottle or fat

droplets float on the surface of the sample.
9 Procedure

NOTE 1 In the determination, two test portions (9.1) are extracted in two Mojonnier-type fat-extraction flasks (6.6). The

extracts of the two flasks are poured into one prepared fat-collecting vessel (9.3).

NOTE 2 If it is required to check whether the repeatability limit (11.2) is met, carry out two single determinations in

accordance with 9.1 to 9.4.

NOTE 3 An alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings (see Note to 6.6) is given

in Annex B.
9.1 Test portion

Mix the test sample (Clause 8) by gently inverting the bottle three or four times. Immediately weigh, to the

nearest 1 mg, 10,000 g to 11,000 g of the test sample, directly or by difference, in each of two fat-extraction

flasks (6.6).

Transfer the test portion as completely as possible into the lower (small) bulb of the fat-extraction flask.

9.2 Blank tests
9.2.1 Blank test for method

Carry out a blank test simultaneously with the determination using the same procedure and the same

reagents, but replacing the test portion by 10 ml of water (see Clause A.2).

When one blank sample is used for a batch of test samples of which the individual samples may not have

exactly the same conditions, ensure that the procedure for obtaining the value of the blank used in the

calculation of the result corresponds exactly to that of the individual test sample.

If the value obtained in the blank test regularly exceeds 1,0 mg, check the reagents if this has not been

recently done (9.2.2). Corrections of more than 2,5 mg should be mentioned in the test report.

9.2.2 Blank test for reagents

To test the quality of the reagents, carry out a blank test as specified in 9.2.1. Additionally, use an empty fat-

collecting vessel, prepared as specified in 9.3, for mass control purposes. The reagents shall leave no residue

greater than 1,0 mg (see Clause A.1).

If the residue of the complete reagent blank test is greater than 1,0 mg, determine the residue of the solvents

separately by distilling 100 ml of the diethyl ether (5.4) and light petroleum (5.5), respectively. Use an empty

fat-collecting vessel, prepared for control purposes as in the preceding paragraph, to obtain the real mass of

residue which shall not exceed 1,0 mg.
4 © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)

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.
Replace unsatisfactory reagents and solvents, or redistil solvents.
9.3 Preparation of fat-collecting vessel

Dry a fat-collecting vessel (6.9) with a few boiling aids (6.10) in the oven (6.4) maintained at 102 °C for 1 h.

NOTE 1 Boiling aids are desirable to promote gentle boiling during the subsequent removal of solvents, especially

when using glass fat-collecting vessels; their use is optional with metal dishes.

Protect the fat-collecting vessel from dust and allow it to cool to the temperature of the weighing room (glass

fat-collecting vessel for at least 1 h, metal dish for at least 30 min).

To avoid insufficient cooling or unduly long cooling times, the fat-collecting vessel should not be placed in a

desiccator.

Use tongs (6.13) to place the fat-collecting vessel on the balance. Weigh the fat-collecting vessel to the

nearest 1,0 mg.

NOTE 2 The use of tongs effectively avoids, in particular, inducing temperature variations.

9.4 Determination
9.4.1 Carry out the determination without delay.

Carry out the operations specified in 9.4.2 to 9.4.13 on both pretreated test portions (9.1).

9.4.2 Add 2 ml of ammonia solution (5.1) to the two test portions in the fat-extraction flasks (9.1), or an

equivalent volume of a more concentrated ammonia solution (see Note to 5.1). Mix thoroughly with the test

portion in the small bulb of each of the two fat-extraction flasks.

9.4.3 Add 10 ml of ethanol (5.2). Mix gently but thoroughly by allowing the contents of the two fat-extraction

flasks to flow backwards and forwards between the small and large bulb. Avoid bringing the liquid too near to

the necks of the flasks. If desired, add 2 drops of the Congo red solution (5.3).

9.4.4 Add 25 ml of diethyl ether (5.4). Close both fat-extraction flasks with a cork bung saturated with water

or with a stopper of other material wetted with water (6.6). Shake the flasks vigorously, but not excessively, for

1 min, to avoid the formation of persistent emulsions.

While shaking, keep both fat-extraction flasks in a horizontal position with their small bulbs extending

upwards, periodically allowing the liquid to run from the large bulb into the small bulb. If necessary, cool the

flasks in running water to about room temperature. Carefully remove the bungs or stoppers and rinse them

and the necks of both flasks with a little mixed solvent (5.6). Use the wash bottle (6.8) so that the rinsings run

into the flask concerned.

9.4.5 Add 25 ml of the light petroleum (5.5). Close both fat-extraction flasks with the rewetted (by dipping

into water) bungs or stoppers. Shake the flasks gently again for 30 s as specified in 9.4.3. Proceed with

shaking as specified in 9.4.4.

9.4.6 Centrifuge the two closed fat-extraction flasks for between 1 min and 5 min at a radial acceleration of

80g to 90g. If a centrifuge (6.2) is not available, allow the closed flasks to stand in the rack (6.7) for at least

30 min until the supernatant layer is clear and distinctly separated from the aqueous layer. If necessary, cool

both flasks in running water to room temperature.
© ISO and IDF 2008 – All rights reserved 5
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SIST EN ISO 7208:2009
ISO 7208:2008(E)
IDF 22:2008(E)

9.4.7 Carefully remove the bungs or stoppers and rinse them and the inside of the necks of the two fat-

extraction flasks with a little mixed solvent (5.6). Use the wash bottle (6.8) s
...

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