1、BSI Standards PublicationBS EN ISO 8968-4:2016Milk and milk products Determination of nitrogencontentPart 4: Determination of protein and non-protein nitrogen content and true proteincontent calculation (Reference method) (ISO8968-4:2016)BS EN ISO 8968-4:2016 BRITISH STANDARDNational forewordThis Br
2、itish Standard is the UK implementation of EN ISO8968-4:2016. It supersedes BS EN ISO 8968-4:2002 which iswithdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can
3、beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 77718 9ICS 67.100.10Compliance
4、 with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 April 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUR
5、OPISCHE NORM EN ISO 8968-4 April 2016 ICS 67.100.10 Supersedes EN ISO 8968-4:2001English Version Milk and milk products - Determination of nitrogen content - Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method) (ISO 8968-4:2016) La
6、it et produits laitiers - Dtermination de la teneur en azote - Partie 4: Dtermination de la teneur en azote protique et non protique et calcul de la teneur en protines vraies (Mthode de rfrence) (ISO 8968-4:2016) Milch und Milcherzeugnisse - Bestimmung des Stickstoffgehaltes - Teil 4: Bestimmung des
7、 Proteinstickstoff-Gehaltes und des Nichtproteinstickstoff-Gehaltes und Berechnung des tatschlichen Proteingehaltes (Referenzverfahren) (ISO 8968-4:2016) This European Standard was approved by CEN on 19 March 2016. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipu
8、late 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 S
9、tandard 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
10、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,
11、 Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any
12、 means reserved worldwide for CEN national Members. Ref. No. EN ISO 8968-4:2016 EBS EN ISO 8968-4:2016EN ISO 8968-4:2016 (E) 3 European foreword This document (EN ISO 8968-4:2016) has been prepared by Technical Committee ISO/TC 34 “Food products“ in collaboration with Technical Committee CEN/TC 278
13、“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 October 2016, and conflicting national standard
14、s shall be withdrawn at the latest by October 2016. 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 89
15、68-4:2001. 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,
16、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 8968-4:2016 has been approved by CEN as E
17、N ISO 8968-4:2016 without any modification. BS EN ISO 8968-4:2016ISO 8968-4:2016(E)IDF 20-4:2016(E)Forewords .v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 14.1 Indirect protein nitrogen . 14.2 Direct protein nitrogen 25 Reagents 25.1 General . 25.2 Trichloroacetic acid
18、(CCl3COOH) solution 25.3 Hydrochloric acid standard volumetric solution . 26 Apparatus . 27 Sampling 38 Preparation of test sample . 39 Procedure Direct protein nitrogen approach . 39.1 Test portion 39.2 Determination . 39.2.1 Precipitation and filtration . 39.2.2 Preparation of the precipitate 49.2
19、.3 Digestion and distillation . 49.2.4 Titration. 49.3 Blank test . 49.4 Calculation and expression of results 49.4.1 Calculation of protein nitrogen content . 49.4.2 Expression of results 59.4.3 Calculation of true protein content 59.4.4 Expression of the true protein content results 510 Procedure
20、Indirect protein nitrogen approach 610.1 Nitrogen determination 610.2 Non-protein nitrogen determination . 610.2.1 Test portion 610.2.2 Precipitation and filtration . 610.2.3 Preparation of the filtrate. 610.2.4 Digestion and distillation . 610.2.5 Titration. 610.3 Blank test . 610.4 Calculation and
21、 expression of results 710.4.1 Calculation of non-protein nitrogen content . 710.4.2 Calculation of protein nitrogen content . 710.4.3 Expression of results 810.4.4 Calculation of true protein content 810.4.5 Expression of the true protein content results 811 Precision . 811.1 Interlaboratory test.
22、811.2 Repeatability . 811.3 Reproducibility . 812 Test report . 9Annex A (informative) Results of a collaborative study Estimation of precision data of direct and indirect methods for the true protein determination .10 ISO and IDF 2016 All rights reserved iiiContents PageBS EN ISO 8968-4:2016ISO 896
23、8-4:2016(E)IDF 20-4:2016(E)Bibliography .11iv ISO and IDF 2016 All rights reservedBS EN ISO 8968-4:2016ISO 8968-4:2016(E)ForewordsISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International S
24、tandards 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, als
25、o 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. I
26、n 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 (see www.iso.org/directives).Attention is drawn to the possibility that some of the element
27、s 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 (
28、see 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.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence
29、 to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products and the International Dairy Federation (IDF). It is being publ
30、ished jointly by ISO and IDF.This second edition of ISO 8968-4|IDF 20-4 cancels and replaces ISO 8968-4|IDF 20-4:2001 and ISO 8968-5|IDF 20-5:2001, which have been technically revised.ISO 8968|IDF 20 consists of the following parts, under the general title Milk and milk products Determination of nit
31、rogen content: Part 1: Kjeldahl principle and crude protein calculation Part 3: Block-digestion method (Semi-micro rapid routine method)1) Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method)1) It is intended that upon revision, th
32、e main element of the title of ISO 8968-3|IDF 20-3 (i.e. “Milk”) will be alignedwith the main element of the titles of ISO 8968-1|IDF 20-1 and ISO 8968-4|IDF 20-4.IDF 20-4:2016(E) ISO and IDF 2016 All rights reserved vBS EN ISO 8968-4:2016ISO 8968-4:2016(E)IDF (the International Dairy Federation) is
33、 a non-profit private sector organization representing the interests of various stakeholders in dairying at the global level. IDF members are organized in National Committees, which are national associations composed of representatives of dairy-related national interest groups including dairy farmer
34、s, dairy processing industry, dairy suppliers, academics and governments/food control authorities.ISO and IDF collaborate closely on all matters of standardization relating to methods of analysis and sampling for milk and milk products. Since 2001, ISO and IDF jointly publish their International Sta
35、ndards using the logos and reference numbers of both organizations.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. Details of any patent rights ident
36、ified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute and endorsementISO 8968-4|IDF 20-4
37、was prepared by the IDF Standing Committee on Analytical methods for composition and ISO Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products.The work was carried out by the IDF/ISO Project Group (C13) of the Standing Committee on Analytical methods for composition
38、 under the aegis of its project leaders, D. Barbano (US) and P. Trossat (FR).This ISO|IDF International Standard cancels and replaces ISO 8968-4|IDF 20-4:2001 and ISO 8968-5|IDF 20-5:2001, which have been technically revised.ISO 8968|IDF 20 consists of the following parts, under the general title Mi
39、lk and milk products Determination of nitrogen content: Part 1: Kjeldahl principle and crude protein calculation Part 3: Block-digestion method (Semi-micro rapid routine method) Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method)I
40、DF 20-4:2016(E)vi ISO and IDF 2016 All rights reservedBS EN ISO 8968-4:2016Milk and milk products Determination of nitrogen content Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method)WARNING The use of this part of ISO 8968|IDF 20
41、 can involve the use of hazardous materials, operations and equipment. This part of ISO 8968|IDF 20 does not purport to address all the safety risks associated with its use. It is the responsibility of the user of this part of ISO 8968|IDF 20 to establish appropriate safety and healthy practices and
42、 determine the applicability of local regulatory limitations prior to use.1 ScopeThis part of ISO 8968|IDF 20 specifies a method for the direct and indirect determination of the protein nitrogen content of liquid, whole or skimmed milk.2 Normative referencesThe following documents, in whole or in pa
43、rt, are normatively referenced in this document and are indispensable for 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 8968-1|IDF 20-1, Milk and milk products Determ
44、ination of nitrogen content Part 1: Kjeldahl principle and crude protein calculation3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1non-protein nitrogen contentNPNmass fraction of substances determined by the specified procedure Note 1 to entry:
45、 The non-protein nitrogen content is expressed as a percentage by mass.3.2protein nitrogen contentmass fraction of substances determined by the specified procedure, directly or, alternatively, indirectlyNote 1 to entry: The protein nitrogen content is expressed as a percentage by mass.4 Principle4.1
46、 Indirect protein nitrogenPrecipitation of protein from a test portion by addition of trichloroacetic acid solution such that the final concentration of trichloroacetic acid in the mixture is approximately 12 %. Removal of the precipitated INTERNATIONAL STANDARDISO 8968-4:2016(E)IDF 20-4:2016(E) ISO
47、 and IDF 2016 All rights reserved 1BS EN ISO 8968-4:2016ISO 8968-4:2016(E)milk protein by filtration, with the remaining filtrate containing the non-protein nitrogen components. Determination of the nitrogen content of the filtrate by the procedure described in ISO 8968-1|IDF 20-1.Where the total ni
48、trogen content of the milk sample has previously been determined, the true protein nitrogen content may be calculated as the difference between the total nitrogen content and the non-protein nitrogen content.4.2 Direct protein nitrogenPrecipitation of protein from a test portion by addition of trich
49、loroacetic acid solution such that the final concentration of trichloroacetic acid in the mixture is approximately 12 %. Separation of the protein precipitate by filtration. (The precipitate contains the protein nitrogen of the sample.) Determination of the nitrogen content of the precipitate by the procedure described in ISO 8968-1|IDF 20-1.5 Reagents5.1 GeneralUse only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity.The reagents specified for
