EN ISO 8968-5:2001

SLOVENSKI STANDARD
01-junij-2002
0OHNR'RORþHYDQMHGXãLNDGHO'RORþHYDQMHEHOMDNRYLQVNHJDGXãLND,62

Milk - Determination of nitrogen content - Part 5: Determination of protein-nitrogen
content (ISO 8968-5:2001)
Milch - Bestimmung des Stickstoffgehaltes - Teil 5: Bestimmung des Proteinstickstoff-
Gehaltes (ISO 8968-5:2001)
Lait - Détermination de la teneur en azote - Partie 5: Détermination de la teneur en azote
protéique (ISO 8968-5:2001)
Ta slovenski standard je istoveten z: EN ISO 8968-5:2001
ICS:
67.100.10 0OHNRLQSUHGHODQLPOHþQL Milk and processed milk
SURL]YRGL products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 8968-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2001
ICS 67.100.10
English version
Milk - Determination of nitrogen content - Part 5: Determination
of protein-nitrogen content (ISO 8968-5:2001)
Lait - Détermination de la teneur en azote - Partie 5: Milch - Bestimmung des Stickstoffgehaltes - Teil 5:
Détermination de la teneur en azote protéique (ISO 8968- Bestimmung des Proteinstickstoff-Gehaltes (ISO 8968-
5:2001) 5:2001)
This European Standard was approved by CEN on 15 December 2001.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, 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
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8968-5:2001 E
worldwide for CEN national Members.

CORRECTED  2002-03-13
Foreword
This document (ISO 8968-5:2001) 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 June 2002, and conflicting national
standards shall be withdrawn at the latest by June 2002.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,
Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO 8968-5:2001 has been approved by CEN as a
European Standard without any modifications.
NOTE Normative references to International Standards are listed in annex ZA (normative).
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated
by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 8968-1 2001 Milk — Determination of nitrogen EN ISO 8968-1 2001
content — Part 1: Kjeldahl method.
ISO 8968-2 2001 Milk — Determination of nitrogen EN ISO 8968-2 2001
content — Part 2: Block-digestion
method (Macro method).
ISO 8968-4 2001 Milk — Determination of nitrogen EN ISO 8968-4 2001
content — Part 4: Determination of the
non-protein nitrogen content.
INTERNATIONAL ISO
STANDARD 8968-5
IDF
20-5
First edition
2001-12-15
Milk — Determination of nitrogen
content —
Part 5:
Determination of protein-nitrogen content
Lait — Détermination de la teneur en azote —
Partie 5: Détermination de la teneur en azote protéique

Reference numbers
ISO 8968-5:2001(E)
IDF 20-5:2001(E)
©
ISO and IDF 2001
ISO 8968-5:2001(E)
IDF 20-5:2001(E)
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ii © ISO and IDF 2001 – All rights reserved

ISO 8968-5:2001(E)
IDF 20-5:2001(E)
Contents Page
Foreword.iv
1 Scope.1
2 Normative references.1
3 Term and definition .1
4 Principle.2
5 Reagents.2
6 Apparatus.2
7 Sampling.2
8 Preparation of test sample.3
9 Procedure.3
9.1 Test portion.3
9.2 Direct determination.3
9.3 Indirect determination.4
10 Calculation and expression of results.4
10.1 Calculation of protein-nitrogen content.4
10.2 Calculation of true protein content.4
11 Precision.5
11.1 Interlaboratory test.5
11.2 Repeatability.5
11.3 Reproducibility.5
12 Test report.5
Bibliography.6

ISO 8968-5:2001(E)
IDF 20-5:2001(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 3.
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 part of ISO 8968IDF 20 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 8968-5IDF 20-5 was prepared by Technical Committee ISO/TC 34, Food products,
Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with
AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International.
ISO 8968IDF 20 consists of the following parts, under the general title Milk — Determination of nitrogen content:
— Part 1: Kjeldahl method
— Part 2: Block-digestion method (Macro method)
— Part 3: Block-digestion method (Semi-micro rapid routine method)
— Part 4: Determination of the non-protein-nitrogen content
— Part 5: Determination of the protein-nitrogen content

iv © ISO and IDF 2001 – All rights reserved

ISO 8968-5:2001(E)
IDF 20-5:2001(E)
Foreword
IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in
every member country. Every National Committee has the right to be represented on the IDF Standing Committees
carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard
methods of analysis and sampling for milk and milk products.
Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National
Committees for voting. Publication as an International Standard requires approval by at least 50 % of National
Committees casting a vote.
International Standard ISO 8968-5IDF 20-5 was prepared by Technical Committee ISO/TC 34, Food products,
Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with
AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International.
All work was carried out by the Joint ISO/IDF/AOAC Action Team, Nitrogen compounds, under the aegis of its
project leader, Mr D.M. Barbano (US).

ISO 8968-5:2001(E)
INTERNATIONAL STANDARD
IDF 20-5:2001(E)
Milk — Determination of nitrogen content —
Part 5:
Determination of protein-nitrogen conten
...