EN ISO 16634-1-2008 en Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Par.pdf

1、BS EN ISO16634-1:2008ICS 65.120; 67.050; 67.200.20NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDFood products Determination ofthe total nitrogencontent by combustionaccording to theDumas principle andcalculation of thecrude protein contentPart 1: Oilseeds and

2、animal feedingstuffs (ISO 16634-1:2008)This British Standardwas published underthe authority of theStandards Policy andStrategy Committee on 30November 2008 BSI 2008ISBN 978 0 580 54276 3Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 16634-1:2008National forewordThis British St

3、andard is the UK implementation of EN ISO16634-1:2008.The UK participation in its preparation was entrusted to TechnicalCommittee AW/4, Cereals and pulses.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all

4、 the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 16634-1November 2008ICS 65.120; 67.200; 67.050English VersionFood products -

5、 Determination of the total nitrogen content bycombustion according to the Dumas principle and calculation ofthe crude protein content - Part 1: Oilseeds and animal feedingstuffs (ISO 16634-1:2008)Produits alimentaires - Dtermination de la teneur en azotetotal par combustion selon le principe Dumas

6、et calcul de lateneur en protines brutes - Partie 1: Graines olagineuseset aliments des animaux (ISO 16634-1:2008)Lebensmittelerzeugnisse - Bestimmung des Gehaltes anGesamtstickstoff mit dem Verbrennungsverfahren nachDumas und Berechnung des Gehaltes an Rohprotein - Teil1: lsaaten und Futtermittel (

7、ISO 16634-1:2008)This European Standard was approved by CEN on 1 November 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibl

8、iographical references concerning such nationalstandards 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 translationunder the responsibility of

9、 a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland,

10、 Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-10

11、50 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 16634-1:2008: EBS EN ISO 16634-1:2008EN ISO 16634-1:2008 (E) 3 Foreword This document (EN ISO 16634-1:2008) has been prepared by Technical Committee ISO/TC 34 “Agri

12、cultural food products“ in collaboration with Technical Committee CEN/TC 327 “Animal feeding stuffs - 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 e

13、ndorsement, at the latest by May 2009, and conflicting national standards shall be withdrawn at the latest by May 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 identifyi

14、ng any or all such patent rights. 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,

15、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 16634-1:2008 has been approved by CEN as a EN ISO 16634-1:2008 without any

16、 modification. BS EN ISO 16634-1:2008ISO 16634-1:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction 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 test sample. 4 9 Procedure 4 9.1

17、 General. 4 9.2 Test portion . 4 9.3 Control of oxygen demand 5 9.4 Calibration . 5 9.5 Determination 5 9.6 Detection and integration 6 10 Calculation and expression of results 6 10.1 Calculation. 6 10.1.1 Nitrogen content . 6 10.1.2 Crude protein content 6 10.2 Expression of results . 7 11 Precisio

18、n 7 11.1 Interlaboratory tests . 7 11.2 Repeatability 7 11.3 Reproducibility 7 12 Test report . 7 Annex A (informative) Flowchart for the basic design of a Dumas apparatus 8 Annex B (informative) Schemes of suitable types of Dumas apparatus 9 Annex C (informative) Equipment calibration . 12 Annex D

19、(informative) Examples of factors for converting nitrogen content to protein content . 14 Annex E (informative) Result of collaborative studies. 15 Annex F (informative) Relationship between Dumas nitrogen and Kjeldahl nitrogen 24 Bibliography . 28 BS EN ISO 16634-1:2008ISO 16634-1:2008(E) iv ISO 20

20、08 All rights reservedForeword 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

21、 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 Commissio

22、n (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 co

23、mmittees 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 no

24、t be held responsible for identifying any or all such patent rights. ISO 16634-1 was prepared by Technical Committee ISO/TC 34, Food products. ISO 16634 consists of the following parts, under the general title Food products Determination of the total nitrogen content by combustion according to the D

25、umas principle and calculation of the crude protein content: Part 1: Oilseeds and animal feeding stuffs A part 2 on cereals, pulses and milled cereal products is in preparation. BS EN ISO 16634-1:2008ISO 16634-1:2008(E) ISO 2008 All rights reserved vIntroduction For a long time the Kjeldahl method h

26、as been the most frequently used method for the determination of protein content of food products. However, in recent years, the Kjeldahl method has increasingly been replaced by the Dumas method, which is faster and does not use dangerous chemicals. Although the principles of the two methods are di

27、fferent, both measure the nitrogen content of the product. Nitrogen can be converted into protein content by using an appropriate factor. The value of this factor varies with the relative amounts of different proteins and their amino-acid composition in the given product. Neither the Dumas nor the K

28、jeldahl method distinguishes between protein and non-protein nitrogen. In most cases, results obtained by the Dumas method are slightly higher than those of the Kjeldahl method. This is due to the fact that the Dumas method measures almost all of the non-protein nitrogen, whereas the Kjeldahl method

29、 measures only a part of it. Taking into consideration that the calculated protein content of a product by both methods only approximates the true value, it is a matter of discretion which one is accepted. The most appropriate solution should be the use of a second factor for the elimination of the

30、systematic error caused by the non-protein nitrogen content of the different products. However, this second factor has to be determined for each product, like existing factors, which show the ratio of the protein to the nitrogen content. BS EN ISO 16634-1:2008BS EN ISO 16634-1:2008INTERNATIONAL STAN

31、DARD ISO 16634-1:2008(E) ISO 2008 All rights reserved 1Food products Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content Part 1: Oilseeds and animal feeding stuffs 1 Scope This part of ISO 16634 specifies a method fo

32、r the determination of the total nitrogen content and the calculation of crude protein content of oilseeds and animal feeding stuffs. This method, like the Kjeldahl method, does not distinguish between protein nitrogen and non-protein nitrogen. For the calculation of protein content, various convers

33、ion factors are used (see Annex D). This method is not applicable to milk and milk products, for which a method is specified in ISO 14891IDF 18510. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition

34、 cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 664, Oilseeds Reduction of laboratory sample to test sample ISO 665, Oilseeds Determination of moisture and volatile matter content ISO 771, Oilseed residues Determination of

35、 moisture and volatile matter content ISO 6496, Animal feeding stuffs Determination of moisture and other volatile matter content ISO 6498, Animal feeding stuffs Preparation of test samples 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 nitr

36、ogen content mass fraction of the total nitrogen determined by the procedure specified in this part of ISO 16634 NOTE The mass fraction is expressed as a percentage. BS EN ISO 16634-1:2008ISO 16634-1:2008(E) 2 ISO 2008 All rights reserved3.2 crude protein content nitrogen content (3.1) multiplied by

37、 a factor, usually 6,25 NOTE 1 A listing of other factors for possible use with various commodities is given in Annex D. NOTE 2 The factors for calculation of crude protein content from the total content of nitrogen are derived from the Kjeldahl method which is the reference method for the determina

38、tion of total nitrogen content. As the method uses the same factors as the Kjeldahl method, the use of these factors has to be verified due to the slight difference in results between the Kjeldahl and Dumas methods. 4 Principle Samples are converted to gases by heating in a combustion tube which gas

39、ifies samples. Interfering components are removed from the resulting gas mixture. The nitrogen compounds in the gas mixture or a representative part of them are converted to molecular nitrogen, which is quantitatively determined by a thermal conductivity detector. The nitrogen content is calculated

40、by a microprocessor. 5 Reagents Use only reagents of recognized analytical grade, or reagents of equivalent purity as specified by instrument manufacturers. Except for the reference materials (5.12), all reagents shall be free from nitrogen. 5.1 Carrier gas(es): use one of 5.1.1 and 5.1.2. 5.1.1 Car

41、bon dioxide, as pure as possible and of minimum volume fraction, (CO2) W 99,99 %. 5.1.2 Helium, as pure as possible and of minimum volume fraction, (He) W 99,99 %. 5.2 Oxygen, as pure as possible and of minimum volume fraction, (O2) W 99,99 %. 5.3 Sulfur dioxide and halogen absorbent, to eliminate a

42、ny sulfur from the sample e.g. lead chromate (PbCrO4) or steel wool. 5.4 Copper oxide platinum catalyst (filling material for the post-combustion tube). Platinum catalyst 5 % of Pt on alumina (Al2O3) is blended with CuO at a ratio of 1:7 parts or 1:8 parts according to the manufacturers recommendati

43、ons. To prevent separation as a result of the different bulk densities of the two materials, it is recommended not to prepare the mixture before filling the tube. It is advisable to pour the platinum catalyst and copper oxide simultaneously into the post-combustion tube using a suitable funnel. 5.5

44、Silver or copper wool. This should be disaggregated before being inserted in the post-combustion or reduction tube. 5.6 Silica (quartz) or glass wool or cotton wool, as recommended by the instrument manufacturer. 5.7 Copper (wire, cuttings, turnings or powder), or tungsten for the reduction tube. Th

45、e use of copper wires can improve the precision of analytical results for samples with low nitrogen contents (about 1 % mass fraction). 5.8 Diphosphorus pentoxide (P2O5) or granulated magnesium perchlorate Mg(ClO4)2, or another suitable support material, to fill the drying tubes. BS EN ISO 16634-1:2

46、008ISO 16634-1:2008(E) ISO 2008 All rights reserved 35.9 Hollow corundum spheres or aluminium oxide pellets, for the combustion tube. 5.10 Copper oxide (CuO), as filling material for the combustion tube. 5.11 Sodium hydroxide (NaOH), on a support material. 5.12 Aspartic acid (C4H7NO4) or ethylenedia

47、minetetraacetic acid (C10H16N2O8) or glutamic acid (C5H9NO4) or hippuric acid (C9H9NO3) standard, or other suitable reference materials with known, constant, certified nitrogen content. Minimum recovery should be 99 % mass fraction. 5.13 Light petroleum, with boiling range between 30 C and 60 C, or

48、acetone or ethanol. 6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to the nearest 0,000 1 g. 6.2 Grinding device, appropriate to the nature of the sample. 6.3 Sieve, of nominal size of openings 800 m or 1 mm, made of non-ferrous

49、material. 6.4 Crucibles (e.g. made of stainless steel, quartz, ceramic or platinum) or tin capsules or nitrogen-free filter paper for pressing pellets, suitable for the Dumas apparatus used. NOTE 1 Several commercial instruments are provided with an automatic sampler. NOTE 2 Some solid samples (e.g. powders) can be pressed to form pellets. 6.5 Dumas apparatus1), fitted with a furnace able to maintain a given temperature greater than or equal to 850 C, with a thermal conductivity detector and suitable device for signal in