EN ISO 21415-2-2008 0625 Wheat and wheat flour - Gluten content - Part 2 Determination of wet gluten by mechanical means《小麦和小麦粉 谷蛋白含量 第2部分 机械法测定湿谷蛋白含量》.pdf

1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 21415-2:2008Wheat and wheat flour Gluten contentPart 2: Determination of wet gluten bymechanical means (ISO 21415-2:2006)Copyright European Committee for Standardizatio

2、n Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of . It is identical to ISO 21415-2:2008. It supersedes BS 4317-25:1990 wh

3、ich is withdrawn. Together with BS EN ISO 21415-1:2007 it supersedes BS 4317-12:1980 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee AW/4, Cereals and pulses.A list of organizations represented on this committee can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 secretar

4、y.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. BSI 2008ISBN 978 0 580 57886 1ICS 67.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published un

5、der the authority of theStandards Policy and Strategy Committee on 31 August 2008.Amendments issued since publicationDate Text affectedCopyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS

6、-,-,-EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 21415-2January 2008ICS 67.060English VersionWheat and wheat flour - Gluten content - Part 2: Determinationof wet gluten by mechanical means (ISO 21415-2:2006)Bl et farines de bl - Teneur en gluten - Partie 2:Dtermination du gluten humide par

7、 des moyensmcaniques (ISO 21415-2:2006)Weizen und Weizenmehl - Glutengehalt - Teil 2:Bestimmung des Feuchtglutens durch mechanischeVerfahren (ISO 21415-2:2006)This European Standard was approved by CEN on 15 December 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations whic

8、h 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 nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Stand

9、ard 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 notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standa

10、rds bodies of 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 and United Kingdo

11、m.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 21415-2:2008: ECopyri

12、ght European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008ISO 21415-2:2006(E) ISO 2006 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normati

13、ve references . 1 3 Terms and definitions. 1 4 Principle. 1 5 Reagents 2 6 Apparatus 2 7 Sampling 3 8 Preparation of test sample. 3 9 Procedure 3 9.1 General. 3 9.2 Test portion . 3 9.3 Dough preparation 3 9.4 Washing the dough. 4 9.5 Removal of excess water and weighing the wet gluten 4 9.6 Number

14、of determinations . 4 10 Calculation and expression of results 5 11 Precision 5 11.1 Interlaboratory tests . 5 11.2 Repeatability 5 11.3 Reproducibility 5 12 Test report . 6 Annex A (informative) Washing chamber and kneader of Glutomatic equipment, and the centrifuge. 7 Annex B (normative) Preparati

15、on of ground wheat 9 Annex C (informative) Results of an interlaboratory test. 10 Bibliography . 11 Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008ISO 2141

16、5-2:2006(E) iv ISO 2006 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

17、 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 and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Elect

18、rotechnical Commission (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 adopte

19、d 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 casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

20、 rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21415-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4, Cereals and pulses. This first edition of ISO 21415-2 cancels and replaces ISO 7495:1990, which has been technically

21、revised. Together with ISO 21415-1:2006, it also cancels and replaces ISO 5531:1978. ISO 21415 consists of the following parts, under the general title Wheat and wheat flour Gluten content: Part 1: Determination of wet gluten by a manual method Part 2: Determination of wet gluten by mechanical means

22、 Part 3: Determination of dry gluten from wet gluten by an oven drying method Part 4: Determination of dry gluten from wet gluten by a rapid drying method Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted with

23、out license from IHS-,-,-BS EN ISO 21415-2:2008ISO 21415-2:2006(E) ISO 2006 All rights reserved vIntroduction The alternative techniques specified in this part of ISO 21415 and in ISO 21415-1 for the isolation of wet gluten (i.e. washing out by hand and mechanical washing out) do not usually give eq

24、uivalent results. The reason is that, for complete development of gluten structure it is necessary to rest the dough. Therefore, the result obtained by hand washing is usually higher than that obtained by mechanical washing, mainly in the case of wheat which has high gluten content. Consequently, th

25、e test report should always indicate the technique used. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008Copyright European Committee for Standardization Pr

26、ovided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008INTERNATIONAL STANDARD ISO 21415-2:2006(E) ISO 2006 All rights reserved 1Wheat and wheat flour Gluten content Part 2: Determination of wet gluten by mechanical

27、 means 1 Scope This part of ISO 21415 specifies a method for the determination of the wet gluten content of wheat flour (Triticum aestivum L. and Triticum durum Desf.) by mechanical means. This method is directly applicable to flour. It is also applicable to semolina and wheat after grinding, if the

28、ir particle size distribution meets the specification given in Table B 1. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenc

29、ed document (including any amendments) applies. ISO 712, Cereals and cereal products Determination of moisture content Routine reference method 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 wet gluten visco-elastic substance, composed princ

30、ipally of two protein fractions (gliadin and glutenin) in hydrated form, obtained as specified in this part of ISO 21415 or ISO 21415-1 3.2 ground wheat product of small-scale milling of whole wheat which meets the particle size distribution shown in Table B.1. 3.3 semolina coarsely milled wheat end

31、osperm 3.4 flour finely milled wheat endosperm with a particle size of less than 250 m 4 Principle Dough is prepared from a sample of flour or reground semolina, or ground wheat and a solution of sodium chloride, in the chamber of the equipment. The wet gluten is separated by washing the dough with

32、sodium chloride solution, followed by removal of excess washing solution by centrifugation. The residue is weighed. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 2141

33、5-2:2008ISO 21415-2:2006(E) 2 ISO 2006 All rights reserved5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 5.1 Sodium chloride solution, 20 g/l. Dissolve 200 g of sodium chloride (NaCl) in wat

34、er then dilute it to 10 l. The temperature of the solutions when used should be 22 C 2 C. It is advisable to prepare this solution freshly every day. 5.2 Potassium iodide/iodine solution (Lugols solution). Dissolve 2,54 g of potassium iodide (KI) in water. Add 1,27 g of iodine (I2) to this solution

35、and, after complete dissolution of the integral parts, dilute to 100 ml with water. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Automatic apparatus for gluten separation1), single or double, consisting of washing chamber(s), kneader(s) (see Figures A.1 and A.2) and

36、a dispensing device under electronic control for gluten separation. 6.1.1 Washing chamber(s), equipped with interchangeable chromed sieve holder(s) and with 88 m aperture polyester sieves or 80 m aperture metal sieves, and 840 m aperture polyamide sieves or 800 m aperture metal sieves. 6.1.2 Kneader

37、 hook, at a distance from the chromed sieve holder of 0,7 mm 0,05 mm. This value should be checked using the stamped metal plates supplied. 6.1.3 Plastic container, of capacity 10 l, containing a reservoir of sodium chloride solution (5.1) connected to the equipment by plastic tubing. 6.1.4 Dispensi

38、ng device, consisting of a peristaltic pump, to deliver the sodium chloride solution (5.1) for gluten washing at a constant flow rate of 50 ml/min to 56 ml/min. For a detailed description of the equipment and for detailed operating instructions, users of this part of ISO 21415 should consult the man

39、ufacturers manual for the equipment employed. 6.2 Adjustable dispenser, for the sodium chloride solution, capable of dispensing 3 ml to 10 ml with an accuracy of 0,1 ml. 6.3 Centrifuge, capable of maintaining a rotational frequency of 6 000 5 per minute and of producing a radial acceleration of 2 00

40、0 g, equipped with perforated plates having apertures 500 m in diameter. 6.4 Balance, capable of weighing to the nearest 0,01 g. 6.5 Spatula, made of stainless steel. 6.6 Beakers, of capacity 500 ml (to collect washings). 1) Glutomatic equipment (types 2100 and 2200) produced by Perten Instruments A

41、B (Sweden) is the most widely used mechanical means for this purpose. This information is given for the convenience of users of this part of ISO 21415 and does not constitute an endorsement by ISO of this equipment. Other equipment may also be used if it gives similar results to Glutomatic equipment

42、 or to the method specified in ISO 21415-1. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN ISO 21415-2:2008ISO 21415-2:2006(E) ISO 2006 All rights reserved 36.7 Metal twee

43、zers. 6.8 Small-scale mill, capable of producing ground product with a particle size that meets the requirements given in Table B.1. 7 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not a p

44、art of the method specified in this part of ISO 21415. A recommended sampling method is given in ISO 6644 or ISO 13690. 8 Preparation of test sample Homogenize the samples and determine their moisture content in accordance with ISO 712. Prior to the gluten content measurement, grind the wheat grain

45、and semolina using a small-scale mill (6.8) as specified in Annex B. To avoid significant changes in the moisture content of the samples, take special care during grinding and storage. 9 Procedure 9.1 General The operations of preparation and washing of the dough are carried out as a continuous proc

46、ess by the automatic apparatus (6.1). Work in accordance with the manufacturers operating instructions for the apparatus in use. 9.2 Test portion Weigh 10 g of the test sample to the nearest 0,01 g and transfer it quantitatively to the washing chamber of the apparatus (6.1.1). Make sure that the was

47、hing chamber is equipped with the appropriate sieve, which has been previously cleaned and moistened. Fine (88 m aperture) polyester or (80 m aperture) metal sieve(s) is/are used for testing flour and reground semolina samples. When testing ground wheat, chromed sieve holder(s) with an indented ring

48、 around the base is/are also required with 840 m aperture polyamide or 800 m metal sieve(s). The aperture size of the sieve(s) used should be indicated in the test report. Shake the chamber gently to spread the flour evenly. 9.3 Dough preparation As a suggested starting point, add 4,8 ml of the sodium chloride solution (5.1) to the test sample using the adjustable dispenser (6.2). Direct the stream of salt solution against the side wall of the chamber so that it does not go through the sieve. Shake the washing chamber gently so that the salt solution is