DIN EN ISO 16634-1-2009 Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Pa.pdf

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1、July 2009DEUTSCHE NORM English price group 17No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 65.120; 67.060; 67.200.10

2、!$XjA“1537130www.din.deDDIN EN ISO 16634-1Food products Determination of the total nitrogen content by combustion according tothe Dumas principle and calculation of the crude protein content Part 1: Oilseeds and animal feeding stuffs (ISO 16634-1:2008)English version of DIN EN ISO 16634-1:2009-07Leb

3、ensmittelerzeugnisse Bestimmung des Gehaltes an Gesamtstickstoff mit dem Verbrennungsverfahren nachDumas und Berechnung des Gehaltes an Rohprotein Teil 1: lsaatenschrote und Futtermittel (ISO 16634-1:2008)Englische Fassung DIN EN ISO 16634-1:2009-07SupersedesDIN EN ISO 16634-1:2009-03www.beuth.deDoc

4、ument comprises 38 pagesDIN EN ISO 16634-1:2009-07 2 National foreword This standard has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France), Subcommittee SC 10 “Animal feeding stuffs” (Secretariat: NEN, Netherlands) in collaboration with Technical Committee C

5、EN/TC 327 “Animal feeding stuffs Methods of sampling and analysis” (Secretariat: NEN, Netherlands). Subcommittee ISO/TC 34/SC 2 “Oleaginous seeds and fruits and oilseed meals” (Secretariat: AFNOR, France) together with Subcommittee ISO/TC 34/SC 10 “Animal feeding stuffs“ decided to establish the Dum

6、as method. The responsible German body involved in its preparation was the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Technical Committee Futtermittel. Following the second parallel vote, draft standard DIN EN ISO 16634 has bee

7、n divided into two parts. This Part 1 applies to oilseeds and animal feeding stuffs. A Part 2 on cereals, pulses and milled cereal products is in preparation (intended as a Technical Specification). The DIN Standards corresponding to the International Standards referred to in this document are as fo

8、llows: ISO 542 DIN EN ISO 542 ISO 664 DIN EN ISO 664 ISO 665 DIN EN ISO 665 ISO 5725-1 DIN ISO 5725-1 ISO 5725-2 DIN ISO 5725-2 ISO 5983-1 DIN EN ISO 5983-1 ISO 5983-2 DIN EN ISO 5983-2 ISO 6497 DIN EN ISO 6497 ISO 13690 DIN EN ISO 13690 ISO 14891 DIN EN ISO 14891 ISO 20483 DIN EN ISO 20483 Amendmen

9、ts Compared with DIN EN ISO 16634-1:2009-03, the following correction has been made: a) (German version only) The equation in Annex F, Table F.1, line “Babynahrung”, column “Umrechnungs-gleichung” has been corrected. Previous editions DIN EN ISO 16634-1 :2009-03 DIN EN ISO 16634-1:2009-07 3 National

10、 Annex NA (informative) Bibliography DIN EN ISO 542, Oilseeds Sampling DIN EN ISO 664, Oilseeds Reduction of laboratory sample to test sample DIN EN ISO 665, Oilseeds Determination of moisture and volatile matter content DIN EN ISO 5983-1, Animal feeding stuffs Determination of nitrogen content and

11、calculation of crude protein content Part 1: Kjeldahl method DIN EN ISO 5983-2, Animal feeding stuffs Determination of nitrogen content and calculation of crude protein content Part 2: Block digestion/steam distillation method DIN EN ISO 6497, Animal feeding stuffs Sampling DIN EN ISO 13690, Cereals

12、, pulses and milled products Sampling of static batches DIN EN ISO 14891, Milk and milk products Determination of nitrogen content Routine method using combustion according to the Dumas principle DIN EN ISO 20483, Cereals and pulses Determination of the nitrogen content and calculation of the crude

13、protein content Kjeldahl method DIN ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions DIN ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatabi

14、lity and reproducibility of a standard measurement method DIN EN ISO 16634-1:2009-07 4 This page is intentionally blank. EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 16634-1 November 2008 ICS 65.120; 67.200; 67.050 English Version Food products Determination of the total nitrogen content

15、 by combustion according to the Dumas principle and calculation of the crude protein content Part 1: Oilseeds and animal feeding stuffs (ISO 16634-1:2008) Produits alimentaires Dtermination de la teneur en azote total par combustion selon le principe Dumas et calcul de la teneur en protines brutes P

16、artie 1: Graines olagineuses et aliments des animaux (ISO 16634-1:2008) Lebensmittelerzeugnisse Bestimmung des Gehaltes an Gesamtstickstoff mit dem Verbrennungsverfahren nach Dumas und Berechnung des Gehaltes an Rohprotein Teil 1: lsaaten und Futtermittel (ISO 16634-1:2008) This European Standard wa

17、s 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 bibliographical references concerning such na

18、tional standards 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 a CEN member into its own language and

19、 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, Italy, Latvia, Lithuania, Luxembourg,

20、 Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of

21、 exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 16634-1:2008: EContents Page Foreword 3 Introduction 4 1 Scope . 5 2 Normative references . 5 3 Terms and definitions. 5 4 Principle. 6 5 Reagents 6 6 Apparatus 7 7 Sampling 8 8 Preparation of tes

22、t sample. 8 9 Procedure 8 9.1 General. 8 9.2 Test portion . 8 9.3 Control of oxygen demand 9 9.4 Calibration . 9 9.5 Determination 9 9.6 Detection and integration 10 10 Calculation and expression of results10 10.1 Calculation.10 10.1.1 Nitrogen content .10 10.1.2 Crude protein content 10 10.2 Expres

23、sion of results .11 11 Precision11 11.1 Interlaboratory tests .11 11.2 Repeatability11 11.3 Reproducibility11 12 Test report .11 Annex A (informative) Flowchart for the basic design of a Dumas apparatus 12 Annex B (informative) Schemes of suitable types of Dumas apparatus 13 Annex C (informative) Eq

24、uipment calibration . 16 Annex D (informative) Examples of factors for converting nitrogen content to protein content . 18 Annex E (informative) Result of collaborative studies. 19 Annex F (informative) Relationship between Dumas nitrogen and Kjeldahl nitrogen 28 Bibliography . 32 DIN EN ISO 16634-1

25、:2009-07EN ISO 16634-1:2008 (E)2Foreword This document (EN ISO 16634-1:2008) has been prepared by Technical Committee ISO/TC 34 “Agricultural food products“ in collaboration with Technical Committee CEN/TC 327 “Animal feeding stuffs - Methods of sampling and analysis” the secretariat of which is hel

26、d 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 May 2009, and conflicting national standards shall be withdrawn at the latest by May 2009. Attention is drawn to the possibility that some

27、 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. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to imple

28、ment this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland

29、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 modification. DIN EN ISO 16634-1:2009-07EN ISO 16634-1:2008 (E)3Introduction For a long time the Kjeldahl method has been the most frequently used method for the dete

30、rmination 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 different, both measure the nitrogen content of the pr

31、oduct. 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 Kjeldahl method distinguishes between protein and non

32、-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 measures only a part of it. Taking into considerati

33、on 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 systematic error caused by the non-protein nitrogen

34、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. DIN EN ISO 16634-1:2009-07EN ISO 16634-1:2008 (E)41 Scope This part of ISO 16634 specifies a method for the determ

35、ination 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 conversion factors

36、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 cited appli

37、es. 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 moisture an

38、d 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 nitrogen content

39、 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. DIN EN ISO 16634-1:2009-07EN ISO 16634-1:2008 (E)53.2 crude protein content nitrogen content (3.1) multiplied by a factor, usually 6,25 NOTE 1 A l

40、isting 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 determination of total nitrogen content. As

41、 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 gasifies samples. Interfering compone

42、nts 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 by a microprocessor. 5 Reagents Us

43、e 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 Carbon dioxide, as pure as possible a

44、nd 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 any sulfur from the sample e.g. lea

45、d 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 recommendations. To prevent separation as a re

46、sult 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 Silver or copper wool. This should

47、 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. The use of copper wires can improve

48、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. DIN EN ISO 16634-1:2009-07EN ISO 16634-1:2008 (E)65.9

49、 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 ethylenediaminetetraacetic 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,