BS EN ISO 10520-1998 Native starch - Determination of starch content - Ewers polarimetric method《天然淀粉 淀粉含量的测定 Ewers旋光计法》.pdf

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1、BRITISH STANDARD BS EN ISO 10520:1998 Native starch Determination of starch content Ewers polarimetric method The European Standard EN ISO 10520:1998 has the status of a British Standard ICS 67.180.20BSENISO10520:1998 This British Standard, having been prepared under the directionof the Consumer Pro

2、ducts and Services Sector Committee, was published underthe authority of the Standards Committeee and comesinto effect on 15November1998 BSI 04-1999 ISBN 0 580 30395 0 National foreword This British Standard is the English language version of EN ISO10520:1998. It is identical with ISO10520:1997. Thi

3、s British Standard has been produced to fulfil BSIs obligation to publish all approved European Standards but, because of the absence of interest in the UK in the subject concerned, there has been no UK participation in the preparation of EN10520. Any queries relating to the EN should be directed to

4、 BSI quoting the reference AW/100. Cross-references Attention is drawn to the fact that CEN and CENELEC standards normally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement internation

5、al or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include al

6、l the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and

7、 ii, theEN ISO title page, page 2, the ISO title page, pages ii to iv, pages 1 to 6, aninsideback cover and aback cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments i

8、ssued since publication Amd. No. Date CommentsBSENISO10520:1998 BSI 04-1999 i Contents Page National foreword Inside front cover Foreword 2 Foreword iii Text of ISO 10520 1ii blankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 10520 September 1998 ICS 67.180 Descriptors: See ISO document E

9、nglish version Native starch Determination of starch content Ewers polarimetric method (ISO10520:1997) Amidons et fcules natifs Dosage de lamidon Mthode polarimtrique de Ewers (ISO10520:1997) Native Strke Bestimmung des Strkegehaltes Polarimetrisches Verfahren nach Ewers (ISO10520:1997) This Europea

10、n Standard was approved by CEN on 10 August 1998. 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

11、rning such national standards may be obtained on application to the Central Secretariat 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 into its own

12、language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Swede

13、n, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Me

14、mbers. Ref. No. EN ISO 10520:1998 EENISO10520:1998 BSI 04-1999 2 Foreword The text of the International Standard from Technical Committee ISO/TC93 “Starch (including derivatives and by-products” of the International Organization for Standardization (ISO) has been taken over as an European Standard b

15、y CEN/CS. 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 March1999, and conflicting national standards shall be withdrawn at the latest by March1999. According to the CEN/CENELEC Internal Regulat

16、ions, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the Uni

17、ted Kingdom. Endorsement notice The text of the International Standard ISO10520:1997 has been approved by CEN as a European Standard without any modification. NOTENormative references to International Standards are listed inAnnex ZA (normative).ENISO10520:1998 ii BSI 04-1999 Contents Page Foreword i

18、ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Preparation of test sample 1 7 Procedure 1 8 Expression of results 2 9 Precision 2 10 Test report 3 Annex A (informative) Ewers method Collaborative study 1990 4 Annex B (informative) Bibliography 6 Annex ZA (normative)

19、 Normative references to international publications with their relevant European publications Inside back cover Table 1 2 Table 2 3 Table A.1 5ENISO10520:1998 BSI 04-1999 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO

20、 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 technical committee has been established has the right to be represented on that committee. International organizations, gover

21、nmental 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 of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the

22、 member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO10520 was prepared by Technical Committee ISO/TC93, Starch (including derivatives and by-products). Annex A andAnnex B of this Internati

23、onal Standard are for information only. Descriptors: Food starch, chemical analysis, determination of content, starches, polarimetric method.iv blankENISO10520:1998 BSI 04-1999 1 1 Scope This International Standard specifies a polarimetric method for the determination of the starch content of native

24、 starch, with the exception of starch with high amylose content. It is not applicable to modified or pregelatinized (water-soluble) starch. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. A

25、t the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and

26、ISO maintain registers of currently valid International Standards. ISO 1666:1996, Starch Determination of moisture content Oven-drying method. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. 3 Principle The method includes two intermediate determination steps. 3.1

27、A portion of the sample is hydrolysed with dilute hydrochloric acid and the optical rotation measured polarimetrically after clarification and filtration. 3.2 A second portion of the sample is treated with40% (V/V) ethanol to extract soluble sugars and polysaccharides of lower molecular mass. The fi

28、ltrate is then subjected to the procedure given in3.1. The difference between the measurements3.1 and3.2, multiplied by a factor, gives the starch content of the sample. NOTEKey parameters of the method are the time and temperature of the hydrolysis, and the correct use and calibration of the polari

29、meter. Consequently, the method includes constant agitation in the water bath, which should be of a size appropriate to ensure rapid temperature rise and steady temperature conditions. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and water complying with g

30、rade2 in accordance with ISO3696. 4.1 Dilute hydrochloric acid, c(HCl) = 7,7 mol/l Dilute 63,7ml of hydrochloric acid ( 20= 1,19g/ml) with water up to100ml. 4.2 Dilute hydrochloric acid, c(HCl) = 0,309 mol/l Dilute 25,6 ml of hydrochloric acid ( 20= 1,19 g/ml) with water up to1000ml. NOTEThe concent

31、ration should be verified using sodium hydroxide solution c(NaOH) = 0,1mol/l and Methyl red as indicator:10mlHCl should consume30,94ml of0,1 mol/l NaOH. 4.3 Dilute ethanol, 40% (V/V) ( 20= 0,948g/ml) 4.4 Carrez solution I Dissolve 10,6 g of potassium hexacyanoferrate(II) trihydrate K 4 Fe(CN) 6 .3H

32、2 O in water. Dilute to100ml with water. 4.5 Carrez solution II Dissolve 21,9 g of zinc acetate dihydrate Zn(CH 3 COO) 2 .2H 2 O and3g of glacial acetic acid in water. Dilute to100ml with water. 5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Volumetric flasks, of capac

33、ity100ml. 5.2 Shaking boiling water bath, or boiling water bath equipped with a magnetic stirrer. 5.3 Polarimeter, adjusted to a wavelength of589,3nm, with200mm tubes. 5.4 Analytical balance, capable of weighing to the nearest0,001g. 6 Preparation of test sample If the particle size of the laborator

34、y sample exceeds0,5mm, grind the sample to pass a sieve with0,5mm apertures. Homogenize the sample thus prepared. 7 Procedure Carry out weighings to the nearest0,001g (see5.4). 7.1 Determination of optical rotation of a total portion 7.1.1 Weigh 2,5 g 0,05g(m 1 ) of the test sample and transfer it t

35、o a volumetric flask(5.1). Add25ml of the dilute hydrochloric acid(4.2) and agitate to distribute the test sample evenly. Add a further25ml of the dilute hydrochloric acid(4.2). 7.1.2 Immerse the flask in the boiling water bath(5.2) and shake continuously or immerse the flask in the boiling water ba

36、th equipped with a magnetic stirrer and stir at minimum speed. 7.1.3 Leave the flask for15min 5s in the boiling water bath and stop shaking or stirring shortly before removing it. Immediately add30ml of cold water and cool rapidly under flowing water to20C2CENISO10520:1998 2 BSI 04-1999 7.1.4 Add 5

37、ml of the Carrez solution I(4.4) and shake for1min. 7.1.5 Add 5 ml of the Carrez solution II(4.5) and shake for1min. 7.1.6 Dilute to the mark with water. Homogenize and filter the solution through a suitable filter funnel and paper. If the filtrate is not perfectly clear, repeat the operations with1

38、0ml of each of the Carrez solutions. 7.1.7 Measure the optical rotation ( 1 ) of the solution in a200mm tube with the polarimeter(5.3). 7.2 Determination of optical rotation of substances soluble in40% (V/V) ethanol 7.2.1 Weigh 5 g 0,1g (m 2 ) of the sample and transfer to a100ml volumetric flask(5.

39、1). Add about80ml of the ethanol solution(4.3). Leave the flask to stand for1h at room temperature; shake vigorously six times during the hour to ensure thorough mixing of the test sample with the ethanol. Dilute to100ml with ethanol(4.3), homogenize and filter. 7.2.2 Pipette 50 ml of the filtrate (

40、equivalent to2,5g of the test portion) into a volumetric flask(5.1). Add2,1ml of the dilute hydrochloric acid(4.1) and shake vigorously. Fit a reflux condenser to the flask and immerse the flask in a boiling water bath. Remove the flask from the boiling water bath after15min5s. Cool to 20C2C. 7.2.3

41、Clarify the solution using Carrez I and II solutions as in7.1.4, 7.1.5 and then continue as in7.1.6. 7.2.4 Measure the optical rotation ( 2 ) of the solution as in7.1.7. 7.3 Determination of dry matter content Determine the moisture content of the test sample, w 0 , in accordance with the method giv

42、en in ISO1666. Then calculate the dry matter content, w 1 , of the test sample using the following equation: w 1= 100 w 0 8 Expression of results Calculate the starch content of the dry matter content of the test sample, w, as a percentage by mass, using the following equation: where Table 1 Round t

43、he result to one decimal place. 9 Precision The precision of the method was established by an interlaboratory test organized by ISO/TC93/WG1, Determination of starch content, in1990 and carried out in accordance with ISO 5725 1 . In this test,12laboratories participated. Samples investigated include

44、d maize starch, potato starch and wheat starch. The statistical results are summarized inAnnex A. 9.1 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the sam

45、e equipment within a short interval of time, should not be greater than the repeatability limit shown inTable 2 for the type of starches listed. 1is the numerical value of the total optical rotation measured in7.1, in degrees; 2 is the numerical value of the optical rotation of the ethanol-soluble s

46、ubstances measured in7.2, in degrees; m 1 is the numerical value of the mass of the test portion in7.1.1, in grams; m 2 is the numerical value of the mass of the test portion in7.2.1, in grams; w 1 is the numerical value of the dry matter content of the test sample determined in7.3, as a percentage

47、by mass; is the numerical value of the specific optical rotation of pure starch measured at a wavelength of589,3nm, in degrees. (SeeTable 1.) Starch type Numerical value of (degrees) Rice starch + 185,9 Potato starch + 185,7 Maize starch + 184,6 Wheat starch + 182,7 Barley starch + 181,5 Oat starch

48、+ 181,3 Other types of starch and starch mixtures + 184,0 20 D 20 DENISO10520:1998 BSI 04-1999 3 9.2 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in different test laboratories with different operators using differ

49、ent equipment, should not be greater than the reproducibility limit shown inTable 2 for the type of starches listed. Table 2 10 Test report The test report shall specify the method used, the test result(s) obtained, and if the repeatability has been checked, the final quoted result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s). The test re