1、March 2014Translation by DIN-Sprachendienst.English price group 11No part of this translation 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 6
2、7.060!%,“2099527www.din.deDDIN EN ISO 20483Cereals and pulses Determination of the nitrogen content and calculation of the crudeprotein content Kjeldahl method (ISO 20483:2013);English version EN ISO 20483:2013,English translation of DIN EN ISO 20483:2014-03Getreide und Hlsenfrchte Bestimmung des St
3、ickstoffgehaltes und Berechnung des Rohproteingehaltes Kjeldahl-Verfahren (ISO 20483:2013);Englische Fassung EN ISO 20483:2013,Englische bersetzung von DIN EN ISO 20483:2014-03Crales et lgumineuses Dtermination de la teneur en azote et calcul de la teneur en protines brutes Mthode de Kjeldahl (ISO 2
4、0483:2013);Version anglaise EN ISO 20483:2013,Traduction anglaise de DIN EN ISO 20483:2014-03SupersedesDIN EN ISO 20483:2007-02www.beuth.deIn case of doubt, the German-language original shall be considered authoritative.Document comprises 20 pages03.14 DIN EN ISO 20483:2014-03 2 A comma is used as t
5、he decimal marker. National foreword This standard (EN ISO 20483:2013) has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France), Subcommittee SC 4 “Cereals and pulses” (Secretariat: SAC, China) in collaboration with Technical Committee CEN/TC 338 “Cereals and c
6、ereal products” (Secretariat: AFNOR, France) and has been published in accordance with the result of the parallel voting procedure. The responsible German body involved in its preparation was the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards
7、Committee), Working Committee NA 057-05-06 AA Getreide und Getreideerzeugnisse. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO 712 DIN EN ISO 712 ISO 6540 DIN EN ISO 6540 ISO 3188 DIN EN ISO 3188 ISO 5725-2 DIN ISO 5725-2 ISO 5725-3 DI
8、N ISO 5725-3 ISO 5725-6 DIN ISO 5725-6 ISO 5983-1 DIN EN ISO 5983-1 ISO 24333 DIN EN ISO 24333 Amendments This standard differs from DIN EN ISO 20483:2007-02 as follows: a) Clause 2 “Normative references” has been updated to include ISO 24557; b) the former Subclause 5.11 “Sodium hydroxide” (now 5.8
9、) has been revised; c) Clause 7 “Sampling” now makes reference to ISO 24333. Previous editions DIN EN ISO 20483: 2007-02 DIN EN ISO 20483:2014-03 3 National Annex NA (informative) Bibliography DIN EN ISO 712, Cereals and cereal products Determination of moisture content Reference method DIN EN ISO 6
10、540, Maize Determination of moisture content (on milled grains and on whole grains) DIN EN ISO 3188, Starches and derived products Determination of nitrogen content by the Kjeldahl method Titrimetric method DIN ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2:
11、Basic method for the determination of repeatability and reproducibility of a standard measurement method DIN ISO 5725-3, Accuracy (trueness and precision) of measurement methods and results Part 3: Intermediate measures of the precision of a standard measurement method DIN ISO 5725-6, Accuracy (true
12、ness and precision) of measurement methods and results Part 6: Use in practice of accuracy values DIN EN ISO 5983-1, Animal feeding stuffs Determination of nitrogen content and calculation of crude protein content Part 1: Kjeldahl method DIN EN ISO 24333, Cereals and cereal products Sampling DIN EN
13、ISO 20483:2014-03 4 This page is intentionally blank EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM December 2013 ICS 67.060 Supersedes EN ISO 20483:2006English Version Cereals and pulses - Determination of the nitrogen conte ntand calculation of the crude protein content - Kjeldahl method (ISO 2
14、0483:2013) Crales et lgumineuses - Dtermination de la teneur en azote et calcul de la teneur en protines brutes - Mthode de Kjeldahl (ISO 20483:2013) Getreide und Hlsenfrchte - Bestimmung des Stickstoffgehaltes und Berechnung des Rohproteingehaltes -Kjeldahl-Verfahren (ISO 20483:2013) This European
15、Standard was approved by CEN on 7 September 2013. 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 conce
16、rning such national standards may be obtained on application to the CEN-CENELEC 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 int
17、o its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, G
18、ermany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE
19、 FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 20483:2013 EEN ISO 204832DIN EN ISO 20483:2014-03EN ISO 20483:2013 (E)Contents Page Foreword . 3
20、1 Scope . 4 2 Normative references. 4 3 Terms and definitions 4 4 Principle 5 5 Reagents . 5 6 Apparatus 6 7 Sampling . 6 8 Preparation of test sample 6 9 Determination of the moisture content 7 10 Procedure 7 10.1 General 7 10.2 Test portion . 7 10.3 Determination . 7 10.4 Blank test 8 10.5 Test wi
21、th reference material (check test) 8 11 Expression of results . 8 11.1 Nitrogen content . 8 11.2 Crude protein content 9 12 Precision . 9 12.1 Interlaboratory test . 9 12.2 Repeatability . 9 12.3 Reproducibility . 9 12.4 Critical difference . 9 13 Test report . 10 Annex A (informative) Results of in
22、terlaboratory tests . 11 Annex B (informative) Critical difference and practical application of the repeatability and reproducibility limits to different protein contents . 13 Annex C (informative) Factors for converting nitrogen content to protein content . 15 Bibliography 16 Foreword This document
23、 (EN ISO 20483:2013) has been prepared by Technical Committee ISO/TC 34 “Food products” in collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publ
24、ication of an identical text or by endorsement, at the latest by June 2014, and conflicting national standards shall be withdrawn at the latest by June 2014. 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
25、 not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 20483:2006. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulg
26、aria, 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Tu
27、rkey and the United Kingdom. Endorsement notice The text of ISO 20483:2013 has been approved by CEN as EN ISO 20483:2013 without any modification. 3DIN EN ISO 20483:2014-03EN ISO 20483:2013 (E)WARNING The use of this International Standard can involve hazardous materials, operations and equipment. T
28、his International Standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety practices and determine the applicability of regulatory limitations prior to use.1 ScopeThis Int
29、ernational Standard specifies a method for the determination of the nitrogen content of cereals, pulses and derived products, according to the Kjeldahl method, and a method for calculating the crude protein content.The method does not distinguish between protein nitrogen and non-protein nitrogen. If
30、 it is important to determine the non-protein nitrogen content, an appropriate method would be applied.NOTE In certain cases, full recovery of the nitrogen in nitrates and nitrites is not possible by this method.2 Normative referencesThe following documents, in whole or in part, are normatively refe
31、renced in this document and are indispensable to 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 712, Cereals and cereal products Determination of moisture content Refe
32、rence methodISO 6540, Maize Determination of moisture content (on milled grains and on whole grains)ISO 24557, Pulses Determination of moisture content Air-oven method3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1nitrogen contentquantity of ni
33、trogen determined after application of the procedure describedNote 1 to entry: It is expressed as a mass fraction of dry product, as a percentage.3.2crude protein contentquantity of crude protein obtained from the nitrogen content as determined by applying the specified method, calculated by multipl
34、ying this content by an appropriate factor depending on the type of cereal or pulseNote 1 to entry: It is expressed as a mass fraction of dry product, as a percentage.4DIN EN ISO 20483:2014-03EN ISO 20483:2013 (E)4 PrincipleA test portion is digested by sulfuric acid in the presence of a catalyst. T
35、he reaction products are made alkaline, then distilled. The liberated ammonia is collected in a boric acid solution, which is titrated with a sulfuric acid solution, in order to determine the nitrogen content and calculate the crude protein content.5 ReagentsWARNING The reagents described in 5.3, 5.
36、8, 5.9 and 5.13 shall be handled with caution.5.1 Use only nitrogen-free reagents of recognized analytical grade, except for the reference materials, and distilled or demineralized water or water of equivalent purity5.2 Kjeldahl tablets, corresponding to the following composition: copper (II) sulfat
37、e pentahydrate (CuSO45H2O) = 2,8 %, titanium oxide (TiO2) = 2,8 % and potassium sulfate (K2SO4) = 94,3 %.Alternatively, copper(II) sulfate pentahydrate, titanium oxide and potassium sulfate may also be mixed in the corresponding ratio.5.3 Sulfuric acid, c(H2SO4) = 18 mol/l, 20(H2SO4) = 1,84 g/ml.5.4
38、 Antifoaming agent: Paraffin oil, silicone or even antifoam tablets may be used to prevent foaming.5.5 Acetanilide (C8H9NO) or tryptophan (C11H12N2O2), of minimum assay 99 % (mass fraction).5.6 Boric acid, aqueous solution, 20(H3BO3) = 40 g/l, or any other concentration recommended for the apparatus
39、 being used.5.7 Coloured indicatorAdd volumes of Solution A (5.7.1) and Solution B (5.7.2) as recommended for the apparatus being used (for example: 5 volumes of Solution A and 1 volume of Solution B) or any other coloured indicator recommended for the apparatus.NOTE 1 It is possible to use a ready-
40、to-use solution of boric acid containing the coloured indicator (5.7.1 and 5.7.2).NOTE 2 The ratio of Solutions A and B can be adjusted depending on the apparatus.The titration may also be carried out potentiometrically by the use of a pH electrode, which shall be checked every day.5.7.1 Solution AB
41、romocresol green (C21H14Br4O5S): 200 mg.Ethanol (C2H5OH), with a volume fraction of 95 %: quantity sufficient for 100 ml of solution.5.7.2 Solution BMethyl red (C15H15N3O2): 200 mg.Ethanol (C2H5OH), with a volume fraction of 95 %: quantity sufficient for 100 ml of solution.5DIN EN ISO 20483:2014-03E
42、N ISO 20483:2013 (E)5.8 Sodium hydroxide, aqueous solution (NaOH), having a mass fraction of between 30 % and 40 %, with nitrogen content less than or equal to 0,001 %.Technical grade sodium hydroxide may also be used when its nitrogen content is less than or equal to 0,001 %.5.9 Sulfuric acid, stan
43、dard volumetric solution, c(H2SO4) = 0,05 mol/l.The use of H2SO4instead of HCl is recommended because H2SO4does not have the tendency to produce bubbles in the connecting tubes.5.10 Ammonium sulfate, standard volumetric solution, c(NH4)2SO4= 0,05 mol/l.Alternatively, a salt such as (NH4)2Fe(2SO4)26H
44、2O may be used.5.11 Pumice stone, granulated, washed in hydrochloric acid and ignited or glass boiling rods may be used to prevent bumping.5.12 Sucrose (optional), free from nitrogen.5.13 Diphosphorus pentoxide (P2O5).6 ApparatusUsual laboratory apparatus and, in particular, the following.6.1 Mechan
45、ical grinder.6.2 Sieve, with aperture size 0,8 mm.6.3 Analytical balance, capable of weighing to the nearest 0,001 g.6.4 Digestion, distillation and titration apparatus.The homogeneous temperature distribution of the digestion unit should be ascertained.The homogeneity of the temperature should be e
46、nsured out by carrying out a full test with one of the two reference materials (5.5), and considering the recovery rates obtained.The distillation apparatus should also be verified by conducting the distillation of a known quantity of ammonium salt e.g. 10 ml of an ammonium sulfate solution (5.10),
47、and by checking that the recovery rate is greater than or equal to 99,8 %.7 SamplingSampling is not part of the method specified in this International Standard. Recommended sampling methods are given in ISO 24333.It is important the laboratory receive a truly representative sample which has not been
48、 damaged or changed during transport or storage.8 Preparation of test sampleIf necessary, grind the sample so that it passes entirely through a sieve with 0,8 mm aperture size. For grains, a mass of at least 200 g should be ground. Mix the ground sample thoroughly.6DIN EN ISO 20483:2014-03EN ISO 204
49、83:2013 (E)9 Determination of the moisture contentDetermine the moisture content, wH, of the test sample from an aliquot of the sample prepared according to Clause 8. Carry out the determination by following the method adapted to the product under test (i.e. ISO 712 for cereals and cereal products, ISO 6540 for maize, the method described in Reference8and which is used for testing certain pulses, or ISO 24557 for pulses).10 Proced
