Milk-based infant foods - Determination of fat content - Gravimetric method (Reference method) (ISO 8381:2008)

ISO 8381¦IDF 123:2008 specifies the reference method for the determination of the fat content of milk-based infant foods.
The method is applicable to liquid, concentrated and dried milk-based infant foods with no, or not more than a mass fraction of 5 % (dry matter) of such added matter as starch, dextrin, vegetables, fruit and meat.
The method is not applicable to products which do not dissolve completely in ammonia owing to the presence of starch or dextrin at mass fractions of more than a few percent, or to the presence of hard lumps. The method is also not applicable to products which contain free fatty acids in significant quantities. The results obtained for these products will be too low.

Säuglingsnahrung auf Milchbasis - Bestimmung des Fettgehaltes - Gravimetrisches Verfahren (Referenzverfahren) (ISO 8381:2008)

Diese Internationale Norm legt das Referenzverfahren für die Bestimmung des Fettgehaltes von Säuglings-nahrung auf Milchbasis fest.
Das Verfahren gilt für flüssige, konzentrierte und getrocknete Säuglingsnahrung auf Milchbasis, die keine oder höchstens einen Massenanteil von 5 % (in der Trockenmasse) an Zusätzen wie Stärke, Dextrin, Gemüse, Früchte und Fleisch enthält.
ANMERKUNG 1   In Säuglingsnahrung häufig vorhandene Maltosedextrine, die keine Dextrine hoher molarer Masse enthalten, wirken sich nicht nachteilig auf die Röse-Gottlieb-Extraktion aus, selbst wenn diese in hoher Konzentration vorhanden sind.
Das Verfahren gilt nicht für Produkte, die Stärke oder Dextrin an Massenanteilen von mehr als nur wenige Prozent enthalten oder zur Bildung harter Klumpen neigen und sich deshalb nicht vollständig in Ammoniak lösen. Das Verfahren gilt ebenso nicht für Produkte, die freie Fettsäuren in signifikanten Mengen enthalten. Bei diesen Produkten fallen die Untersuchungsergebnisse zu niedrig aus.
ANMERKUNG 2   Bei derartigen Produkten ist ein Verfahren geeignet, das nach dem Weibull-Berntrop-Prinzip arbeitet
(siehe ISO 8262-1|IDF 124-1 [3]).

Aliments à base de lait pour enfants en bas âge - Détermination de la teneur en matière grasse - Méthode gravimétrique (Méthode de référence) (ISO 8381:2008)

L'ISO 8381|FIL 123:2008 spécifie la méthode de référence pour la détermination de la teneur en matière grasse des aliments à base de lait pour enfants en bas âge.
Cette méthode est applicable aux aliments à base de lait liquides, concentrés et séchés pour enfants en bas âge, ne contenant pas ou pas plus qu'une fraction massique de 5 % (de la matière sèche) d'amidon, de dextrines, de légumes, de fruits, de viandes, etc.
La méthode n'est applicable ni aux produits qui ne se dissolvent pas complètement dans l'ammoniaque, du fait de la présence d'amidon ou de dextrines à des fractions massiques supérieures à quelques pour cent, ou encore de la présence de grumeaux compacts, ni aux produits qui contiennent des acides gras libres en quantité significative; le résultat de la détermination sera trop faible.

Hrana za majhne otroke na osnovi mleka - Določevanje maščob - Gravimetrijska metoda (Referenčna metoda) (ISO 8381:2008)

General Information

Status
Published
Publication Date
14-Oct-2008
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
15-Oct-2008
Completion Date
15-Oct-2008

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SLOVENSKI STANDARD
SIST EN ISO 8381:2009
01-februar-2009
1DGRPHãþD
SIST EN ISO 8381:2001
+UDQD]DPDMKQHRWURNHQDRVQRYLPOHND'RORþHYDQMHPDãþRE*UDYLPHWULMVND
PHWRGD 5HIHUHQþQDPHWRGD  ,62

Milk-based infant foods - Determination of fat content - Gravimetric method (Reference

method) (ISO 8381:2008)
Säuglingsnahrung auf Milchbasis - Bestimmung des Fettgehaltes - Gravimetrisches
Verfahren (Referenzverfahren) (ISO 8381:2008)

Aliments à base de lait pour enfants en bas âge - Détermination de la teneur en matière

grasse - Méthode gravimétrique (Méthode de référence) (ISO 8381:2008)
Ta slovenski standard je istoveten z: EN ISO 8381:2008
ICS:
67.100.99 'UXJLPOHþQLSURL]YRGL Other milk products
67.230 Predpakirana in pripravljena Prepackaged and prepared
hrana foods
SIST EN ISO 8381:2009 en,fr,de

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

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SIST EN ISO 8381:2009
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SIST EN ISO 8381:2009
EUROPEAN STANDARD
EN ISO 8381
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2008
ICS 67.230 Supersedes EN ISO 8381:2000
English Version
Milk-based infant foods - Determination of fat content -
Gravimetric method (Reference method) (ISO 8381:2008)

Aliments à base de lait pour enfants en bas âge - Säuglingsnahrung auf Milchbasis - Bestimmung des

Détermination de la teneur en matière grasse - Méthode Fettgehaltes - Gravimetrisches Verfahren

gravimétrique (Méthode de référence) (ISO 8381:2008) (Referenzverfahren) (ISO 8381:2008)

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 8381:2008: E

worldwide for CEN national Members.
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SIST EN ISO 8381:2009
EN ISO 8381:2008 (E)
Contents Page

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

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SIST EN ISO 8381:2009
EN ISO 8381:2008 (E)
Foreword

This document (EN ISO 8381:2008) 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 8381:2000.

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 8381:2008 has been approved by CEN as a EN ISO 8381:2008 without any modification.

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SIST EN ISO 8381:2009
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SIST EN ISO 8381:2009
INTERNATIONAL ISO
STANDARD 8381
IDF
123
Third edition
2008-10-15
Milk-based infant foods — Determination
of fat content — Gravimetric method
(Reference method)
Aliments à base de lait pour enfants en bas âge — Détermination de la
teneur en matière grasse — Méthode gravimétrique (Méthode de
référence)
Reference numbers
ISO 8381:2008(E)
IDF 123:2008(E)
ISO and IDF 2008
---------------------- Page: 7 ----------------------
SIST EN ISO 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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

Case postale 56 • CH-1211 Geneva 20 Diamant Building • Boulevard Auguste Reyers 80 • B-1030 Brussels

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 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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

8.1 Liquid products......................................................................................................................................4

8.2 Viscous or pasty products....................................................................................................................4

8.3 Dried products .......................................................................................................................................4

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

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

9.2 Blank tests..............................................................................................................................................5

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

9.4 Determination.........................................................................................................................................5

10 Calculation and expression of results.................................................................................................8

10.1 Calculation..............................................................................................................................................8

10.2 Expression of results ............................................................................................................................8

11 Precision.................................................................................................................................................8

11.1 Interlaboratory test ................................................................................................................................8

11.2 Repeatability...........................................................................................................................................8

11.3 Reproducibility.......................................................................................................................................9

12 Test report ..............................................................................................................................................9

Annex A (informative) Notes on procedures ..................................................................................................10

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

fittings ...................................................................................................................................................12

Bibliography ......................................................................................................................................................15

© ISO and IDF 2008 – All rights reserved iii
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SIST EN ISO 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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 8381⎪IDF 123 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 8381⎪IDF 123 cancels and replaces the second edition (ISO 8381:2000), of which it

constitutes a minor revision.
iv © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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 8381⎪IDF 123 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 8381⎪IDF 123 cancels and replaces IDF 123:1988, of which it constitutes a minor revision.

© ISO and IDF 2008 – All rights reserved v
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SIST EN ISO 8381:2009
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SIST EN ISO 8381:2009
ISO 8381:2008(E)
INTERNATIONAL STANDARD
IDF 123:2008(E)
Milk-based infant foods — 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 milk-

based infant foods.

The method is applicable to liquid, concentrated and dried milk-based infant foods with no, or not more than a

mass fraction of 5 % (dry matter) of such added matter as starch, dextrin, vegetables, fruit, and meat.

NOTE 1 Malto-dextrins without higher molecular mass dextrins, which are often present in infant foods, do not disturb

the Röse-Gottlieb extraction even when present in high concentrations.

The method is not applicable to products which do not dissolve completely in ammonia owing to the presence

of starch or dextrin at mass fractions of more than a few percent, or to the presence of hard lumps. The

method is also not applicable to products which contain free fatty acids in significant quantities. The results

obtained for these products are too low.
[3]

NOTE 2 For such products, a method utilizing the Weibull-Berntrop principle is suitable (see ISO 8262-1⎪IDF 124-1 ).

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 milk

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 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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 9.4.4). 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 8381:2009
ISO 8381:2008(E)
IDF 123:2008(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 9.4.7).

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 9.4.14) 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 baths, capable of being maintained at temperatures of between 30 °C and 40 °C, 40 °C and

60 °C, and 60 °C and 70 °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 all liquid, viscous or pasty laboratory samples at a temperature of between 2 °C and 6 °C from the time

of sampling to the time of commencing the procedure. Store laboratory samples in sealed cans or bottles

unopened at a temperature below 20 °C until the time of commencing the procedure.

© ISO and IDF 2008 – All rights reserved 3
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SIST EN ISO 8381:2009
ISO 8381:2008(E)
IDF 123:2008(E)
8 Preparation of test sample
8.1 Liquid products

Shake and invert the sample container. Open the container to pour the product slowly into a second sample

container provided with an airtight lid. Mix by repeated transfer of the product, taking care to incorporate in the

sample any fat or other constituent adhering to the wall and ends of the first container. Transfer the test

sample as completely as possible to the second sample container. Close this container.

If necessary, condition the unopened sample container in the water bath (6.5) maintained between 40 °C and

60 °C. Remove and shake the container vigorously every 15 min. After 2 h, remove the container, dry the

outside with a tissue and allow to cool to room temperature. Remove the lid or cap entirely and thoroughly mix

the contents by stirring with a spoon or spatula. (If fat separates, do not test the sample.) Transfer the test

sample as completely as possible to a second sample container provided with an airtight lid. Close this

container.
8.2 Viscous or pasty products

Open the sample container and thoroughly mix the contents with a spoon or spatula. If possible, use an

up-and-down rotary movement in such a way that the top layers and the contents of the lower corners of the

container are moved and mixed. Take care to incorporate in the test sample any fat or other constituents

adhering to the wall and ends of the container. Transfer the test sample as completely as possible to a second

sample container provided with an airtight lid. Close this container.

If necessary, condition the unopened sample container in the water bath (6.5) maintained between 30 °C and

40 °C. Remove the container, dry the outside with a tissue and open it. Scrape out all test sample adhering to

the interior of the container. Transfer the test sample to a dish large enough to permit thorough stirring, and

mix until the whole mass is homogeneous. Transfer the test sample as completely as possible to a second

sample container provided with an airtight lid. Close this container.
8.3 Dried products

Thoroughly mix the sample container by repeatedly rotating and inverting. If necessary, transfer all of the test

sample to a suitable airtight sample container of sufficient capacity to allow this operation to be carried out.

9 Procedure

NOTE 1 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 2 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) in the case of viscous, pasty or dried products by stirring, or in the case of

liquid products by gently inverting the sample container three or four times. Immediately weigh, to the nearest

1 mg, directly or by difference, 1,500 g to 10,000 g of the test sample, corresponding to 1,0 g to 1,5 g of dry

matter, in a fat-extraction flask (6.6).

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

4 © ISO and IDF 2008 – All rights reserved
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SIST EN ISO 8381:2009
ISO 8381:2008(E)
IDF 123:2008(E)
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 same reagents,

but replacing the dispersed test portion in 9.4.1 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.

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
...

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