SIST EN ISO 20483:2014
(Main)Cereals and pulses - Determination of the nitrogen content and calculation of the crude protein content - Kjeldahl method (ISO 20483:2013)
Cereals and pulses - Determination of the nitrogen content and calculation of the crude protein content - Kjeldahl method (ISO 20483:2013)
This International Standard specifies a method for the determination of the nitrogen content of cereals, pulses and derived products, according to the Kjeldahl method, and a method for calculating the crude protein content. The method does not distinguish between protein nitrogen and non-protein nitrogen. If it is important to determine the non-protein nitrogen content, an appropriate method can be applied.
Getreide und Hülsenfrüchte - Bestimmung des Stickstoffgehaltes und Berechnung des Rohproteingehaltes - Kjeldahl-Verfahren (ISO 20483:2013)
Diese Internationale Norm legt ein Verfahren zur Bestimmung des Stickstoffgehaltes von Getreide, Hülsen-früchten und deren Produkten nach dem Kjeldahl-Verfahren und ein Verfahren zur Berechnung des Rohproteingehaltes fest.
Das Verfahren unterscheidet nicht zwischen Proteinstickstoff und Nichtproteinstickstoff. Wenn es wichtig ist, den Gehalt an Nichtproteinstickstoff zu bestimmen, kann ein geeignetes Verfahren angewendet werden.
ANMERKUNG In bestimmten Fällen ist eine vollständige Erfassung des in Nitraten und Nitriten vorliegenden Stickstoffs mit diesem Verfahren nicht möglich.
Céréales et légumineuses - Détermination de la teneur en azote et calcul de la teneur en protéines brutes - Méthode de Kjeldahl (ISO 20483:2013)
L'ISO 20483:2006 spécifie une méthode pour la détermination de la teneur en azote des céréales, des légumineuses et des produits dérivés, selon la méthode de Kjeldahl, ainsi qu'une méthode de calcul de la teneur en protéines brutes.
La méthode ne fait pas la distinction entre l'azote protéique et l'azote non protéique. S'il importe de déterminer la teneur en azote non protéique, on peut appliquer une méthode appropriée.
Žito in stročnice - Določevanje dušika in izračun deleža surovih beljakovin - Metoda po Kjeldahlu (ISO 20483:2013)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 20483:2014
01-februar-2014
1DGRPHãþD
SIST EN ISO 20483:2007
äLWRLQVWURþQLFH'RORþHYDQMHGXãLNDLQL]UDþXQGHOHåDVXURYLKEHOMDNRYLQ
0HWRGDSR.MHOGDKOX ,62
Cereals and pulses - Determination of the nitrogen content and calculation of the crude
protein content - Kjeldahl method (ISO 20483:2013)
Getreide und Hülsenfrüchte - Bestimmung des Stickstoffgehaltes und Berechnung des
Rohproteingehaltes - Kjeldahl-Verfahren (ISO 20483:2013)
Céréales et légumineuses - Détermination de la teneur en azote et calcul de la teneur en
protéines brutes - Méthode de Kjeldahl (ISO 20483:2013)
Ta slovenski standard je istoveten z: EN ISO 20483:2013
ICS:
67.060 äLWDVWURþQLFHLQSURL]YRGLL] Cereals, pulses and derived
QMLK products
SIST EN ISO 20483:2014 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST EN ISO 20483:2014
---------------------- Page: 2 ----------------------
SIST EN ISO 20483:2014
EUROPEAN STANDARD
EN ISO 20483
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2013
ICS 67.060 Supersedes EN ISO 20483:2006
English Version
Cereals and pulses - Determination of the nitrogen content and
calculation of the crude protein content - Kjeldahl method (ISO
20483:2013)
Céréales et légumineuses - Détermination de la teneur en Getreide und Hülsenfrüchte - Bestimmung des
azote et calcul de la teneur en protéines brutes - Méthode Stickstoffgehaltes und Berechnung des Rohproteingehaltes
de Kjeldahl (ISO 20483:2013) - Kjeldahl-Verfahren (ISO 20483:2013)
This European Standard was approved by CEN on 7 September 2013.
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-CENELEC 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-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20483:2013 E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 20483:2014
EN ISO 20483:2013 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 20483:2014
EN ISO 20483:2013 (E)
Foreword
This document (EN ISO 20483:2013) has been prepared by Technical Committee ISO/TC 34 “Food products”
in collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” the secretariat of which
is held by AFNOR.
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 June 2014, and conflicting national standards shall be withdrawn at
the latest by June 2014.
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 20483:2006.
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, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 20483:2013 has been approved by CEN as EN ISO 20483:2013 without any modification.
3
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SIST EN ISO 20483:2014
---------------------- Page: 6 ----------------------
SIST EN ISO 20483:2014
INTERNATIONAL ISO
STANDARD 20483
Second edition
2013-12-01
Cereals and pulses — Determination
of the nitrogen content and calculation
of the crude protein content —
Kjeldahl method
Céréales et légumineuses — Détermination de la teneur en azote et
calcul de la teneur en protéines brutes — Méthode de Kjeldahl
Reference number
ISO 20483:2013(E)
©
ISO 2013
---------------------- Page: 7 ----------------------
SIST EN ISO 20483:2014
ISO 20483:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 20483:2014
ISO 20483:2013(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 3
7 Sampling . 3
8 Preparation of test sample . 3
9 Determination of the moisture content . 4
10 Procedure. 4
10.1 General . 4
10.2 Test portion . 4
10.3 Determination . 4
10.4 Blank test . 5
10.5 Test with reference material (check test) . 5
11 Expression of results . 5
11.1 Nitrogen content . 5
11.2 Crude protein content . 6
12 Precision . 6
12.1 Interlaboratory test. 6
12.2 Repeatability . 6
12.3 Reproducibility . 6
12.4 Critical difference. 6
13 Test report . 7
Annex A (informative) Results of interlaboratory tests. 8
Annex B (informative) Critical difference and practical application of the repeatability and
reproducibility limits to different protein contents .10
Annex C (informative) Factors for converting nitrogen content to protein content .12
Bibliography .13
© ISO 2013 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 20483:2014
ISO 20483:2013(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.
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. www.iso.org/directives
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. 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. 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.
The committee responsible for this document is ISO/TC 34, food and food products, Subcommittee SC 4,
cereals and pulses.
This second edition cancels and replaces the first edition (ISO 20483:2006), which has been
technically revised.
iv © ISO 2013 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 20483:2014
INTERNATIONAL STANDARD ISO 20483:2013(E)
Cereals and pulses — Determination of the nitrogen
content and calculation of the crude protein content —
Kjeldahl method
WARNING — The use of this International Standard can 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 appropriate safety practices and determine the applicability of regulatory limitations
prior to use.
1 Scope
This International Standard specifies a method for the determination of the nitrogen content of cereals,
pulses and derived products, according to the Kjeldahl method, and a method for calculating the crude
protein content.
The method does not distinguish between protein nitrogen and non-protein nitrogen. If it is important
to determine the non-protein nitrogen content, an appropriate method would be applied.
NOTE In certain cases, full recovery of the nitrogen in nitrates and nitrites is not possible by this method.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable to its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 712, Cereals and cereal products — Determination of moisture content — Reference method
ISO 6540, Maize — Determination of moisture content (on milled grains and on whole grains)
ISO 24557, Pulses — Determination of moisture content — Air-oven method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nitrogen content
quantity of nitrogen determined after application of the procedure described
Note 1 to entry: It is expressed as a mass fraction of dry product, as a percentage.
3.2
crude protein content
quantity of crude protein obtained from the nitrogen content as determined by applying the specified
method, calculated by multiplying this content by an appropriate factor depending on the type of
cereal or pulse
Note 1 to entry: It is expressed as a mass fraction of dry product, as a percentage.
© ISO 2013 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 20483:2014
ISO 20483:2013(E)
4 Principle
A test portion is digested by sulfuric acid in the presence of a catalyst. The reaction products are made
alkaline, then distilled. The liberated ammonia is collected in a boric acid solution, which is titrated with a
sulfuric acid solution, in order to determine the nitrogen content and calculate the crude protein content.
5 Reagents
WARNING — The reagents described in 5.3, 5.8, 5.9 and 5.13 shall be handled with caution.
5.1 Use only nitrogen-free reagents of recognized analytical grade, except for the reference materials,
and distilled or demineralized water or water of equivalent purity
5.2 Kjeldahl tablets, corresponding to the following composition: copper (II) sulfate pentahydrate
(CuSO ·5H O) = 2,8 %, titanium oxide (TiO ) = 2,8 % and potassium sulfate (K SO ) = 94,3 %.
4 2 2 2 4
Alternatively, copper(II) sulfate pentahydrate, titanium oxide and potassium sulfate may also be mixed
in the corresponding ratio.
5.3 Sulfuric acid, c(H SO ) = 18 mol/l, ρ (H SO ) = 1,84 g/ml.
2 4 20 2 4
5.4 Antifoaming agent: Paraffin oil, silicone or even antifoam tablets may be used to prevent foaming.
5.5 Acetanilide (C H NO) or tryptophan (C H N O ), of minimum assay 99 % (mass fraction).
8 9 11 12 2 2
5.6 Boric acid, aqueous solution, ρ (H BO ) = 40 g/l, or any other concentration recommended for
20 3 3
the apparatus being used.
5.7 Coloured indicator
Add volumes of Solution A (5.7.1) and Solution B (5.7.2) as recommended for the apparatus being used
(for example: 5 volumes of Solution A and 1 volume of Solution B) or any other coloured indicator
recommended for the apparatus.
NOTE 1 It is possible to use a ready-to-use solution of boric acid containing the coloured indicator
(5.7.1 and 5.7.2).
NOTE 2 The ratio of Solutions A and B can be adjusted depending on the apparatus.
The titration may also be carried out potentiometrically by the use of a pH electrode, which shall be
checked every day.
5.7.1 Solution A
Bromocresol green (C H Br O S): 200 mg.
21 14 4 5
Ethanol (C H OH), with a volume fraction of 95 %: quantity sufficient for 100 ml of solution.
2 5
5.7.2 Solution B
Methyl red (C H N O ): 200 mg.
1
...
SLOVENSKI STANDARD
oSIST prEN ISO 20483:2012
01-september-2012
äLWRLQVWURþQLFH'RORþHYDQMHGXãLNDLQL]UDþXQGHOHåDVXURYLKEHOMDNRYLQ
0HWRGDSR.MHOGDKOX ,62',6
Cereals and pulses - Determination of the nitrogen content and calculation of the crude
protein content - Kjeldahl method (ISO/DIS 20483:2012)
Getreide und Hülsenfrüchte - Bestimmung des Stickstoffgehaltes und Berechnung des
Rohproteingehaltes - Kjeldahl-Verfahren (ISO/DIS 20483:2012)
Céréales et légumineuses - Détermination de la teneur en azote et calcul de la teneur en
protéines brutes - Méthode de Kjeldahl (ISO/DIS 20483:2012)
Ta slovenski standard je istoveten z: prEN ISO 20483 rev
ICS:
67.060 äLWDVWURþQLFHLQSURL]YRGLL] Cereals, pulses and derived
QMLK products
oSIST prEN ISO 20483:2012 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 20483:2012
---------------------- Page: 2 ----------------------
oSIST prEN ISO 20483:2012
EUROPEAN STANDARD
DRAFT
prEN ISO 20483 rev
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2012
ICS 67.060 Will supersede EN ISO 20483:2006
English Version
Cereals and pulses - Determination of the nitrogen content and
calculation of the crude protein content - Kjeldahl method
(ISO/DIS 20483:2012)
Céréales et légumineuses - Détermination de la teneur en Getreide und Hülsenfrüchte - Bestimmung des
azote et calcul de la teneur en protéines brutes - Méthode Stickstoffgehaltes und Berechnung des Rohproteingehaltes
de Kjeldahl (ISO/DIS 20483:2012) - Kjeldahl-Verfahren (ISO/DIS 20483:2012)
This draft European Standard is submitted to CEN members for parallel enquiry. It has been drawn up by the Technical Committee
CEN/TC 338.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 20483 rev:2012: E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN ISO 20483:2012
prEN ISO 20483:2012 (E)
Contents Page
Foreword .3
2
---------------------- Page: 4 ----------------------
oSIST prEN ISO 20483:2012
prEN ISO 20483:2012 (E)
Foreword
This document (prEN ISO 20483:2012) has been prepared by Technical Committee ISO/TC 34 "Food
products" in collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” the secretariat
of which is held by AFNOR.
This document is currently submitted to the parallel Enquiry.
This document will supersede EN ISO 20483:2006.
Endorsement notice
The text of ISO/DIS 20483:2012 has been approved by CEN as a prEN ISO 20483:2012 without any
modification.
3
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oSIST prEN ISO 20483:2012
---------------------- Page: 6 ----------------------
oSIST prEN ISO 20483:2012
DRAFT INTERNATIONAL STANDARD ISO/DIS 20483
ISO/TC 34/SC 4 Secretariat: SAC
Voting begins on Voting terminates on
2012-07-05 2012-12-05
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ ORGANISATION INTERNATIONALE DE NORMALISATION
Cereals and pulses — Determination of the nitrogen content
and calculation of the crude protein content — Kjeldahl method
Céréales et légumineuses — Détermination de la teneur en azote et calcul de la teneur en protéines brutes —
Méthode de Kjeldahl
[Revision of first edition (ISO 20483:2006)]
ICS 67.060
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for Standardization (ISO), and
processed under the ISO-lead mode of collaboration as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel
five-month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments received, will be
submitted to a parallel two-month approval vote in ISO and formal vote in CEN.
To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
publication stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME
STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2012
---------------------- Page: 7 ----------------------
oSIST prEN ISO 20483:2012
ISO/DIS 20483
Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted
under the applicable laws of the user’s country, neither this ISO draft nor any extract from it may be
reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic,
photocopying, recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2012 – All rights reserved
---------------------- Page: 8 ----------------------
oSIST prEN ISO 20483:2012
ISO/DIS 20483
Contents Page
Foreword .iv
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Principle.2
5 Reagents.2
6 Apparatus.3
7 Sampling.3
8 Preparation of test sample .3
9 Determination of the moisture content .4
10 Procedure.4
10.1 General.4
10.2 Test portion.4
10.3 Determination.4
10.3.1 Digestion.4
10.3.2 Distillation.5
10.3.3 Titration.5
10.4 Blank test.5
10.5 Test with reference material (Check test) .5
11 Expression of results.5
11.1 Nitrogen content.5
11.2 Crude protein content .6
12 Precision.6
12.1 Interlaboratory test.6
12.2 Repeatability.6
12.3 Reproducibility.6
12.4 Critical difference.7
12.4.1 Comparison of two groups of measurements in one laboratory .7
12.4.2 Comparison of two groups of measurements in two laboratories.7
13 Test report.7
Annex A (informative) Results of interlaboratory tests.8
Annex B (informative) Critical difference and practical application of the repeatability and
reproducibility limits to different protein contents.10
B.1 Comparison of two groups of measurements in one laboratory .10
B.2 Comparison of two groups of measurements in two laboratories.10
Annex C (informative) Factors for converting nitrogen content to protein content .12
Bibliography.13
© ISO 2012 – All rights reserved iii
---------------------- Page: 9 ----------------------
oSIST prEN ISO 20483:2012
ISO/DIS 20483
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 20483 was prepared by Technical Committee ISO/TC 34, food and food products, Subcommittee SC 4,
cereals and pulses.
This second edition cancels and replaces the first edition, which has been technically revised.
iv © ISO 2012 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 20483:2012
ISO/DIS 20483
Cereals and pulses — Determination of the nitrogen content
and calculation of the crude protein content — Kjeldahl method
WARNING — The use of this standard 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 appropriate safety practices and determine the
applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a method for the determination of the nitrogen content of cereals, pulses
and derived products, according to the Kjeldahl method, and a method for calculating the crude protein
content.
The method does not distinguish between protein nitrogen and non-protein nitrogen. If it is important to
determine the non-protein nitrogen content, an appropriate method can be applied.
NOTE In certain cases, full recovery of the nitrogen in nitrates and nitrites is not possible by this method.
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 712, Cereals and cereal products — Determination of moisture content — Routine reference method
ISO 6540, Maize — Determination of moisture content (on milled grains and on whole grains)
ISO 24557, Pulses - Determination of moisture content – Air oven method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nitrogen content
quantity of nitrogen determined after application of the procedure described in this International Standard
NOTE It is expressed as mass fraction of dry product, in percent.
3.2
crude protein content
quantity of crude protein obtained from the nitrogen content as determined by applying the method described
in this document, calculated by multiplying this content by an appropriate factor depending on the type of
cereal or pulse
NOTE It is expressed as mass fraction of dry product, in percent.
© ISO 2012 – All rights reserved i
---------------------- Page: 11 ----------------------
oSIST prEN ISO 20483:2012
ISO/DIS 20483
4 Principle
A test portion is digested by sulfuric acid in the presence of a catalyst. The reaction products are made
alkaline then distilled. The liberated ammonia is collected in a boric acid solution, which is titrated with a
sulfuric acid solution, to determine the nitrogen content and calculate the crude protein content.
5 Reagents
Use only nitrogen-free reagents of recognized analytical grade, except for the reference materials, and
distilled or demineralized water or water of equivalent purity.
WARNING — The reagents described in 5.4, 5.8, 5.11 and 5.12 shall be handled with precautions.
5.1 Potassium sulfate (K SO ).
2 4
5.2 Copper(II) sulfate pentahydrate (CuSO ·5H O).
4 2
5.3 Titanium oxide (TiO ).
2
5.4 Sulfuric acid, c(H SO ) = 18 mol/l, ρ (H SO ) = 1,84 g/ml.
2 4 20 2 4
5.5 Paraffin oil.
5.6 Acetanilide (C H NO), having a melting point of 114 °C and nitrogen content of 10,36 g/100 g.
8 9
5.7 Tryptophan (C H N O ), having a melting point of 282 °C and nitrogen content of 13,72 g/100 g.
11 12 2 2
5.8 Phosphorus pentoxide (P O ).
2 5
5.9 Boric acid, aqueous solution, ρ (H BO ) = 40 g/l, or any other concentration recommended for the
20 3 3
apparatus being used.
5.10 Coloured indicator
Add volumes of Solution A (5.10.1) and Solution B (5.10.2) as recommended for the apparatus being used (for
example: 5 volumes of Solution A and 1 volume of Solution B).
NOTE 1 It is possible to use a ready-to-use solution of boric acid containing the coloured indicator (5.9 + 5.10).
NOTE 2 The ratio of Solutions A and B may be adjusted depending on the apparatus.
The titration may also be carried out potentiometrically by the use of pH-electrode, which has to be checked
every day.
5.10.
...
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