DIN EN ISO 21415-1-2007 Wheat and wheat flour - Gluten content - Part 1 Determination of wet gluten by a manual method (ISO 21415-1 2006) German version EN ISO 21415-1 2007《小麦和小麦粉 .pdf

1、July 2007DEUTSCHE NORM English price group 10No 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 67.060!,y5“9869918www.din

2、.deDDIN EN ISO 21415-1Wheat and wheat flour Gluten content Part 1: Determination of wet gluten by a manual method(ISO 21415-1:2006)English version of DIN EN ISO 21415-1:2007-07Weizen und Weizenmehl Glutengehalt Teil 1: Manuelle Methode zur Bestimmung des Feuchtglutens (ISO 21415-1:2006)Englische Fas

3、sung DIN EN ISO 21415-1:2007-07www.beuth.deDocument comprises 15 pages09.07DIN EN ISO 21415-1:2007-07 2 National foreword This standard has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR/ABNT, France, Brazil), Subcommittee SC 4 “Cereals and pulses” (Secretariat: S

4、AC, China), in collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” (Secretariat: AFNOR, France). Based on the results of the unique acceptance procedure, ISO 21415-1:2006 has been adopted as European Standard EN ISO 21415-1:2007. The responsible German body involved in its

5、 preparation was the Normenausschuss Lebensmittel und land-wirtschaftliche Produkte (Foodstuffs and Agricultural Products Standards Committee), Technical Committee Getreide und Getreideerzeugnisse. ISO 21415 consists of the following parts, under the general title Wheat and wheat flour Gluten conten

6、t: Part 1: Determination of wet gluten by a manual method Part 2: Determination of wet gluten by mechanical means 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 The DIN Standard corresponding t

7、o the International Standard referred to in clause 2 of the EN is as follows: ISO 712 DIN 10350 National Annex NA (informative) Bibliography DIN 10350, Determination of moisture in cereals and cereal products EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 21415-1March 2007ICS 67.060English Ve

8、rsionWheat and wheat flour - Gluten content - Part 1: Determinationof wet gluten by a manual method (ISO 21415-1:2006)Bl et farines de bl - Teneur en gluten - Partie 1:Dtermination du gluten humide par une mthode manuelle(ISO 21415-1:2006)Weizen und Weizenmehl - Glutengehalt - Teil 1: ManuelleMethod

9、e zur Bestimmung des FeuchtglutensThis European Standard was approved by CEN on 25 February 2007.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-d

10、ate lists and bibliographical 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

11、 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 standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary,

12、 Iceland, Ireland, 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

13、 Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 21415-1:2007: E(ISO 21415-1:2006)EN ISO 21415-1:2006 (E) Contents Page Foreword. 3 Introduction 4 1 Scope . 5 2 Normative references . 5 3 Terms a

14、nd definitions 5 4 Principle. 5 5 Reagents 6 6 Apparatus 6 7 Sampling 7 8 Preparation of test sample. 7 9 Procedure 7 9.1 General. 7 9.2 Test portion . 7 9.3 Dough preparation and leaving it to rest . 7 9.4 Washing out 7 9.5 Removal of excess washing solution. 8 9.6 Determination of the mass of the

15、wet gluten. 8 9.7 Number of determinations . 8 10 Calculation and expression of results 8 11 Precision 9 11.1 Interlaboratory tests . 9 11.2 Repeatability 9 11.3 Reproducibility 9 12 Test report . 9 Annex A (normative) Gluten press. 10 Annex B (normative) Preparation of ground wheat 11 Annex C (info

16、rmative) Results of an interlaboratory test. 12 Bibliography . 13 2 EN ISO 21415-1:2006 (E) Foreword The text of ISO 21415-1:2006 has been prepared by Technical Committee ISO/TC 34 “Agricultural food products” of the International Organization for Standardization (ISO) and has been taken over as EN

17、ISO 21415-1:2007 by 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 publication of an identical text or by endorsement, at the latest by September 2007, and conf

18、licting national standards shall be withdrawn at the latest by September 2007. 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

19、, 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 Kingdom. Endorsement notice The text of ISO 21415-1:2006 has been approved by

20、 CEN as EN ISO 21415-1:2007 without any modifications. 3 Introduction The alternative techniques specified in this part of ISO 21415 and in ISO 21415-2 for the isolation of wet gluten (i.e. washing out by hand and mechanical washing out) do not usually give equivalent results. The reason is that, fo

21、r complete development of the 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, the test report should always indicat

22、e the technique used. EN ISO 21415-1:2006 (E) 4 1 Scope This part of ISO 21415 specifies a manual washing out method for the determination of the wet gluten content of wheat flour (Triticum aestivum L. and Triticum durum Desf.). This method is directly applicable to flour. It is also applicable to s

23、emolina and wheat after grinding, if their 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 refere

24、nces, the latest edition of the referenced 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

25、 visco-elastic substance, composed principally of two protein fractions (gliadin and glutenin) in a hydrated form, obtained as specified in this part of ISO 21415 or ISO 21415-2 3.2 ground wheat product of small-scale milling of whole wheat which meets the particle size distribution shown in Table B

26、.1 3.3 semolina coarsely milled wheat endosperm 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. The dough is left to rest for the gluten struct

27、ure to develop. The wet gluten is separated by hand EN ISO 21415-1:2006 (E) 5 washing the dough with sodium chloride solution, followed by removal of excess washing solution. The residue is weighed. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distille

28、d or demineralized water or water of equivalent purity. 5.1 Sodium chloride solution, 20 g/l. Dissolve 200 g of sodium chloride (NaCl) in water then dilute it to 10 l. 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)

29、 to this solution 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 Porcelain mortar, glazed inside, or enamelled metal vessel of diameter 10 cm to 15 cm. 6.2 Burette, of capacity 25 ml, g

30、raduated in 0,1 ml. 6.3 Beaker, of capacity 250 ml. 6.4 Spatula, plastic or stainless steel, 18 cm to 20 cm in length. 6.5 Glass plate, about 40 cm 40 cm. 6.6 Gloves, of thin rubber and having a smooth surface. 6.7 Wooden frame, about 30 cm 40 cm, covered with No. 56 grit gauze (308 m). 6.8 Containe

31、r, with adjustable outflow, for the sodium chloride solution (5.1). 6.9 Filter paper1), of mass approximately 120 g/m2. 6.10 Stop-watch. 6.11 Balance, capable of weighing to the nearest 0,01 g. 6.12 Gluten press, see Annex A. 6.13 Watch-glass, of diameter 8 cm. 6.14 Small-scale mill, capable of mill

32、ing to a particle size distribution that meets the requirements given in Table B.1. 1) For example, the Macherey Nagel No. 651 filter paper is suitable 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

33、this product. EN ISO 21415-1:2006 (E) 6 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 part of the method specified in this part of ISO 21415. A recommended sampling method is given i

34、n 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 wheat grain and semolina using a small-scale mill (6.14) as specified in Annex B. To avoid changes in the moist

35、ure content of the samples, take special care during grinding and storage. 9 Procedure 9.1 General Use sodium chloride solution (5.1) for the preparation and washing of the dough. The test sample and the sodium chloride solution should be kept at least for one night in the laboratory where the proce

36、dure will be carried out. If the ambient temperature is lower than 20 C or higher than 25 C, the temperature of the test sample and the sodium chloride solution should be adjusted to between 20 C and 25 C. 9.2 Test portion Weigh about 24 g of the test sample to the nearest 0,01 g (m1) and transfer i

37、t quantitatively to the mortar or vessel (6.1). 9.3 Dough preparation and leaving it to rest 9.3.1 Add drop-by-drop 12 ml of the sodium chloride solution (5.1) from the burette (6.2), while continuously stirring the flour with the spatula (6.4). 9.3.2 After adding the sodium chloride solution, compr

38、ess the mixture with the spatula and form a dough ball, taking care to avoid loss of flour. Dough residues adhering to the wall of the vessel or to the spatula shall be collected with the dough ball. 9.3.3 Preparation of the dough should not take longer than 3 min. 9.3.4 Place the dough ball on the

39、glass plate (6.5). Cover the inside of a 250 ml beaker (6.3) with wet filter paper (6.9) and then use it to cover the dough ball. Leave the dough to rest for 30 min. 9.4 Washing out 9.4.1 The operations described in 9.4.2 and 9.4.3 shall be carried out over the wooden frame covered with gauze (6.7)

40、to avoid the possible loss of dough. During the operations, the hands shall be covered with rubber gloves (6.6) in order to protect the dough from warmth and perspiration from the hands. 9.4.2 After the resting period, weigh about 30 g from the dough ball (9.3) to the nearest 0,01 g (m2). Take it in

41、 the palm of one hand and allow the sodium chloride solution (5.1) to drip onto it from the container (6.8) at a flowing rate of 750 ml per 8 min. During this time, successively roll out and mould the dough ball with the thumb of the other hand. EN ISO 21415-1:2006 (E) 7 9.4.3 The washing is conside

42、red to be complete when the sodium chloride solution pressed out from the gluten ball obtained as in 9.4.2 is practically free of starch. For the detection of starch, press out some drops of the washing solution from the gluten ball into a watch-glass (6.13) and add a few drops of potassium iodide/i

43、odine solution (5.2) to it. If the colour of the solution does not change, the washing out procedure is completed. If the colour of the solution turns blue, this indicates that starch is still present and the washing out procedure should be continued until it cannot be detected. 9.4.4 The washing ou

44、t time depends on the gluten content, but in general is about 8 min. 9.5 Removal of excess washing solution 9.5.1 Eliminate most of the washing solution adhering to the gluten ball by holding it between the fingers of one hand and compressing it briefly three times. 9.5.2 Divide the gluten ball into

45、 two approximately equal parts, form them into a laminated shape and place them in the gluten press (6.12). Close the gluten press and re-open it after 5 s. Transfer the gluten leaves, without deforming them, to other dry places in the gluten press and close it again for 5 s. Repeat this operation 1

46、5 times. Dry the glass plates of the gluten press after each operation. 9.6 Determination of the mass of the wet gluten Weigh together the two gluten leaves formed in 9.5.2, to the nearest 0,01 g (m3). 9.7 Number of determinations Carry out two determinations on the same sample. 10 Calculation and e

47、xpression of results The wet gluten content (Gwet), expressed as a mass fraction of the test sample in percent, is equal to 31wet21( 12)100 %mmGmm+=where m1 is the mass of test portion of the sample (9.2), in grams; m2 isthe mass portion of dough ball (9.3) used for the washing out procedure (9.4),

48、in grams; m3 is the mass of wet gluten (9.6), in grams; 12 is the volume of sodium chloride solution (5.1) used for preparing the dough, in millilitres. Express the results to one decimal place. NOTE 1 Deviation of the specific gravity of sodium chloride solution (5.1) from 1,00 is negligible in com

49、parison with the standard deviation of the method itself. NOTE 2 Generally the result of the determination is not expressed as the dry matter content of the test sample (flour or semolina or wheat). It is advisable, therefore, to give the moisture content of the test sample in the test report. EN ISO 21415-1:2006 (E) 8 11 Precision 11.1 Interlaboratory tests Details of an interlaboratory test on the precision of the method are summarized in Annex C. The values derived from this interlaboratory test may not be applicable to concentration ranges and