1、BSI Standards PublicationBS EN ISO 20483:2013Cereals and pulses Determination of the nitrogencontent and calculation ofthe crude protein content Kjeldahl methodBS EN ISO 20483:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO20483:2013. It supersedes BS E
2、N ISO 20483:2006 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee AW/4, Cereals and pulses.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprov
3、isions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 76312 0ICS 67.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published un
4、der the authority of theStandards Policy and Strategy Committee on 31 December 2013.Amendments issued since publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 20483 December 2013 ICS 67.060 Supersedes EN ISO 20483:2006English Version Cereals and pulses - Determinat
5、ion of the nitrogen content and calculation of the crude protein content - Kjeldahl method (ISO 20483:2013) 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 Stickstoffg
6、ehaltes und Berechnung des Rohproteingehaltes - Kjeldahl-Verfahren (ISO 20483:2013) This European 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
7、 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 Standard exists in three official versions (English, French, German)
8、. 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 national standards bodies of Austria, Belgium, Bulgaria, Croatia, C
9、yprus, 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, Turkey and United
10、Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE 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
11、 20483:2013 EBS EN ISO 20483:2013EN ISO 20483:2013 (E) 3 Foreword This document (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 Eur
12、opean Standard shall be given the status of a national standard, either by publication 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
13、 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 20483:2006. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
14、countries are bound to implement this European Standard: 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
15、, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey 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. BS EN ISO 20483:2013ISO 20483:2013(E) ISO 2013 All rights reserved iiiCont
16、ents PageForeword iv1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 25 Reagents 26 Apparatus . 37 Sampling 38 Preparation of test sample . 39 Determination of the moisture content 410 Procedure. 410.1 General . 410.2 Test portion 410.3 Determination . 410.4 Blank test . 510
17、.5 Test with reference material (check test) 511 Expression of results 511.1 Nitrogen content 511.2 Crude protein content . 612 Precision . 612.1 Interlaboratory test. 612.2 Repeatability . 612.3 Reproducibility . 612.4 Critical difference 613 Test report . 7Annex A (informative) Results of interlab
18、oratory tests 8Annex B (informative) Critical difference and practical application of the repeatability and reproducibility limits to different protein contents .10Annex C (informative) Factors for converting nitrogen content to protein content 12Bibliography .13BS EN ISO 20483:2013ISO 20483:2013(E)
19、ForewordISO (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 subject for which a te
20、chnical 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 Commission (IEC) on all matters
21、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. In particular the different approval criteria needed for the different types of ISO documents should be noted. This documen
22、t was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directivesAttention 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
23、 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. www.iso.org/patentsAny trade name used in this document is information given for the convenience of users and does not constitut
24、e an endorsement.The committee responsible for this document is ISO/TC 34, food and food products, Subcommittee SC 4, cereals and pulses.This second edition cancels and replaces the first edition (ISO 20483:2006), which has been technically revised.iv ISO 2013 All rights reservedBS EN ISO 20483:2013
25、INTERNATIONAL STANDARD ISO 20483:2013(E)Cereals and pulses Determination of the nitrogen content and calculation of the crude protein content Kjeldahl methodWARNING The use of this International Standard can involve hazardous materials, operations and equipment. This International Standard does not
26、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 International Standard specifies a meth
27、od 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 it is important to determine the no
28、n-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 referenced in this document and are indi
29、spensable 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 Reference methodISO 6540, Maize Determin
30、ation 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 nitrogen determined after application
31、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 multiplying this content by an appropriate
32、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. ISO 2013 All rights reserved 1BS EN ISO 20483:2013ISO 20483:2013(E)4 PrincipleA test portion is digested by sulfuric acid in the presence of a catalyst. The reaction pr
33、oducts 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, 5.8, 5.9 and 5.1
34、3 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) sulfate pentahydrate
35、 (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 Antifoaming a
36、gent: 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 being used.5.
37、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-to-use solutio
38、n 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 ABromocresol gre
39、en (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.2 ISO 2013 All rights reservedBS EN ISO
40、20483:2013ISO 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 aci
41、d, standard 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(2
42、SO4)26H2O 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
43、 Mechanical 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 shou
44、ld be ensured 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 (
45、5.10), 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 n
46、ot been 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. ISO 2013 All rights reserve
47、d 3BS EN ISO 20483:2013ISO 20483:2013(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
48、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 Procedure10.1 GeneralIf it is required to check that the requirements given concerning the repeatability limit (12.2) are fulfilled, carry out
49、two separate determinations in accordance with 10.2 to 10.5.10.2 Test portionWeigh, to the nearest 0,001 g, a mass of test sample prepared according to Clause 8, chosen on the basis of the assumed nitrogen content, so that the test portion contains between 0,005 g and 0,2 g of nitrogen and preferably more than 0,02 g.10.3 Determination10.3.1 DigestionWARNING The following operations should be conducted under a well-ventilated, sulfuric acid-resistant hood.Transfer the test portion (10.2) to the digestion flask. Then, add the req
