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1、DD ISO/TS 17837:2008 ICS 67.100.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW DRAFT FOR DEVELOPMENT Milk and milk products Determination of nitrogen content and crude protein calculation Kjeldahl method Licensed Copy: London South Bank University, South Bank University, 3
2、1/01/2009 02:57, Uncontrolled Copy, (c) BSI This Draft for Development was published under the authority of the Standards Policy and Strategy Committee on 3 ember 2008 BSI 2008 ISBN 978 0 580 60160 6 Amendments/corrigenda issued since publication DateComments DD ISO/TS 17837:2008 National foreword T
3、his Draft for Development is the UK implementation of ISO/TS 17837:2008. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature. It should be applied on this provisional basis, so that inform
4、ation and experience of its practical application can be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the international organization responsible for its conversion to an international standard. A review of this publicati
5、on will be initiated not later than 3 years after its publication by the international organization so that a decision can be taken on its status. Notification of the start of the review period will be made in an announcement in the appropriate issue of Update Standards. According to the replies rec
6、eived by the end of the review period, the responsible BSI Committee will decide whether to support the conversion into an international Standard, to extend the life of the Technical Specification or to withdraw it. Comments should be sent to the Secretary of the responsible BSI Technical Committee
7、at British Standards House, 389 Chiswick High Road, London W4 4AL. The UK participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk products. A list of organizations represented on this committee can be obtained on request to its secretary. This p
8、ublication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. 1 Dec Licensed Copy: London South Bank University, South Bank University, 31/01/2009
9、 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 Reference numbers ISO/TS 17837:2008(E) IDF/RM 25:2008(E) ISO and IDF 2008 TECHNICAL SPECIFICATION ISO/TS 17837 IDF/RM 25 First edition 2008-03-15 Milk and milk products Determination of nitrogen content and crude protein calculation Kjeldahl me
10、thod Lait et produits laitiers Dtermination de la teneur en azote et calcul des protines brutes Mthode Kjeldahl Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 ISO/TS 17837:2008(E) IDF/RM 25:2008 PDF disclaimer Thi
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14、MENT 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
15、 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 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.is
16、o.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2008 All rights reserved Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 ISO/TS 17837:2008(E) IDF/RM 25:2008 ISO and IDF 2008 All rights reserved ii
17、i 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 3 7 Sampling 4 8 Preparation of the test sample 4 8.1 Cheese . 4 8.2 Milk. 5 9 Procedure 5 9.1 Traditional method 5 9.2 Block digestion method. 6 9.3 Blank
18、 test. 8 9.4 Recovery tests 8 10 Calculation and expression of results 9 10.1 Calculation. 9 10.2 Expression of results . 10 11 Precision 10 11.1 Interlaboratory test. 10 12 Test report . 11 Annex A (informative) Interlaboratory trial 12 Bibliography. 13 Licensed Copy: London South Bank University,
19、South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 ISO/TS 17837:2008(E) IDF/RM 25:2008 iv ISO and IDF 2008 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bo
20、dies). 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 an
21、d 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,
22、 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 cas
23、ting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a technical committee may decide to publish other types of document: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in an ISO working
24、group and is accepted for publication if it is approved by more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical committee and is accepted for publication if it is approved by 2/3 of th
25、e members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed again after a furt
26、her three years, at which time it must either be transformed into an International Standard or be withdrawn. 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
27、rights. ISO/TS 17837 was prepared by Technical Committee ISO/TC 34, Food Products, Subcommittee SC 5, Milk and milk products. ISO/TS 17837IDF/RM 25 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). I
28、t is being published jointly by ISO and IDF. Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 ISO/TS 17837:2008(E) IDF/RM 25:2008 ISO and IDF 2008 All rights reserved v Foreword IDF (the International Dairy Federati
29、on) 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 I
30、DF 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 fo
31、r voting. Publication as an International Standard requires approval by at least 50 % of the IDF National Committees casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a Standing Committee may decide to publish another type of normativ
32、e document which is called by IDF: Reviewed method. Such a method represents an agreement between the members of a Standing Committee and is accepted for publication if it is approved by at least 50 % of the committee members casting a vote. A Reviewed method is equal to an ISO/PAS or ISO/TS and wil
33、l, therefore, also be published jointly under ISO conditions. 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/TS 17837IDF/RM 25 was prepared by t
34、he 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 on Nitrogen compounds of the Standing committee on Main compone
35、nts in milk under the aegis of its project leader, Mr. J. Romero (US). This edition of ISO/TS 17837IDF/RM 25 cancels and replaces IDF 25:1964, which has undergone minor editorial and technical revisions. Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontroll
36、ed Copy, (c) BSI DD ISO/TS 17837:2008 Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 TECHNICAL SPECIFICATION ISO/TS 17837:2008(E) IDF/RM 25:2008 ISO and IDF 2008 All rights reserved 1 Milk and milk products Determ
37、ination of nitrogen content and crude protein calculation Kjeldahl method WARNING Performance of the method specified in this Technical Specification may involve the use of hazardous materials, operations, and equipment. This Technical Specification does not purport to address all the safety risks a
38、ssociated with such performance. It is the responsibility of the user to establish appropriate safety and health practices and determine the applicability of local regulatory limitations prior to performance of the method. 1 Scope This Technical Specification specifies a method for the determination
39、 of the nitrogen content and crude protein content by calculation in milk and milk products by using the Kjeldahl principle, both traditional and block digestion methods. The methods specified are applicable to whole and skimmed liquid bovine, caprine and ovine milk, and hard, semi-hard and processe
40、d cheese. NOTE Inaccurate crude protein results are obtained if non-dairy sources of nitrogen are present in the specified milk or milk products. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition c
41、ited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 385, Laboratory glassware Burettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 4788, Laboratory glassware Graduated measuring cylinders 3 Terms and definition
42、s For the purposes of this document, the following terms and definitions apply. 3.1 nitrogen content mass fraction of nitrogen determined by the procedure specified in this Technical Specification NOTE The nitrogen mass fraction is expressed as a percentage. 3.2 crude protein content mass fraction o
43、f crude protein calculated as specified by this Technical Specification NOTE The crude protein mass fraction is expressed as a percentage. Licensed Copy: London South Bank University, South Bank University, 31/01/2009 02:57, Uncontrolled Copy, (c) BSI DD ISO/TS 17837:2008 ISO/TS 17837:2008(E) IDF/RM
44、 25:2008 2 ISO and IDF 2008 All rights reserved 4 Principle A test portion is digested with a mixture of concentrated sulfuric acid and potassium sulfate. Copper(II) sulfate is used as a catalyst to thereby convert organic nitrogen present to ammonium sulfate. The function of the potassium sulfate i
45、s to elevate the boiling point of the sulfuric acid and to provide a stronger oxidizing mixture for digestion. Excess sodium hydroxide is added to the cooled digest to liberate ammonia. The liberated ammonia is steam distilled into excess boric acid solution and titrated against a hydrochloric acid
46、standard volumetric solution. The nitrogen content is calculated from the amount of ammonia produced and the crude protein content from the nitrogen content obtained. 5 Reagents Unless otherwise specified, use only reagents of recognized analytical grade, and only distilled or demineralized water or
47、 water of equivalent purity. 5.1 Potassium sulfate (K2SO4), nitrogen free. 5.2 Copper(II) sulfate pentahydrate solution, (CuSO45H2O) = 5,0 g/100 ml. Dissolve 5,0 g of copper(II) sulfate pentahydrate in water in a 100 ml one-mark volumetric flask (6.8). Dilute to the mark with water and mix. 5.3 Sulf
48、uric acid (H2SO4), with a mass fraction of between 95 % and 98 %, nitrogen free 20(H2SO4) 1,84 g/ml. 5.4 Sodium hydroxide aqueous solution, nitrogen free, containing 50 g of sodium hydroxide (NaOH) per 100 g (mass fraction of sodium hydroxide, wNaOH = 50 %). If plugging of the flow system in an auto
49、matic distillation unit is a problem, use a solution with wNaOH = 40 %. 5.5 Indicator solution. 5.5.1 Dissolve 0,1 g of methyl red in 95 % (volume fraction) ethanol in a 50 ml one-mark volumetric flask (6.8). Dilute to the 50 ml mark with similar ethanol and mix. 5.5.2 Dissolve 0,5 g of bromocresol green in 95 % (volume fraction) ethanol in a 250 ml one-mark volumetric flask (6.8). Dilute to the mark with similar ethanol and mix. 5.5.3 Mix one volume of the methyl red solution (5.5.1) with five volumes of the br
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