BS ISO 2911-2004 Sweetened condensed milk - Determination of sucrose content - Polarimetric method《甜炼乳 蔗糖含量的测定 旋光法》.pdf

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1、BRITISH STANDARD BS ISO 2911:2004 Sweetened condensed milk Determination of sucrose content Polarimetric method ICS 67.100.10 BS ISO 2911:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 23 December 2004 BSI 23 December 2004 ISBN 0 580 45

2、162 3 National foreword This British Standard reproduces verbatim ISO 2911:2004 and implements it as the UK national standard. It supersedes BS 1742-6:1990 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has the res

3、ponsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “Internationa

4、l Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British S

5、tandard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and Eur

6、opean developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last is

7、sued. Amendments issued since publication Amd. No. Date Comments Reference numbers ISO 2911:2004(E) IDF 35:2004(E)INTERNATIONAL NATSDRAD ISO 2119 FDI 53 noceSd deoitin 1-400210-2 Sweetened condensed milk Determination of sucrose content Polarimetric method Laits concentrs sucrs Dtermination de la te

8、neur en saccharose Mthode polarimtrique Referecne unbmers OSI :1192)E(4002 DI2:53 F0)E(40 OSI DI dnaF 4002INTERNATIONAL STANDARD ISO 2911 IDF 35 Second edition 2004-12-01 Swoc deneteendesneim d kl mreteDanitnoi of rcusc esotnoen t emiraloPm cirteohtd stiaL cocnrtnes sucrs retDmanitoid ne la etruen n

9、e saccrahsoe ohtM op edlarimrtqieu BSISO2911:2004 ii BSISO2911:2004 iiiContents Foreword iv 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle . 1 5 Reagents 2 6 Apparatus. 2 7 Sampling 3 8 Procedure. 3 8.1 Preparation of test sample. 3 8.2 Check test 3 8.3 Determination 3 8

10、.4 Direct polarization. 4 8.5 Inversion 4 8.6 Invert polarization . 4 9 Expression of results 4 9.1 Method of calculation and equations 4 9.2 Values of the inversion division factor, Q 5 10 Repeatability 6 11 Test report 6 Bibliography . 7 BSISO2911:2004iv Foreword ISO (the International Organizatio

11、n 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 technical committee has been established has

12、 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 of electrotechnical standardization. Inter

13、national 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 adopted by the technical committees are circulated to the member bodies for voting. Publicat

14、ion 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 rights. ISO shall not be held responsible for identifying any or all such patent righ

15、ts. ISO 2911 IDF 35 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. This

16、 edition of ISO 2911 IDF 35 cancels and replaces ISO 2911:1976, of which it constitutes a minor revision. Only editorial changes have been made. BSISO2911:2004 vForeword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every member c

17、ountry. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard methods of analysis and sampling for milk and milk products. Draft International Standards

18、adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires approval by at least 50 % of the National Committees casting a vote. ISO 2911 IDF 35 was prepared by Technical Committee ISO/TC 34, Food product

19、s, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Group of Experts, Lactose (E6),

20、under the aegis of its project leader, Mr E. Langridge (GB). This edition of ISO 2911 IDF 35 cancels and replaces IDF 35A:1992. Only editorial changes have been made. BSISO2911:2004blankNITERNATNOIAL STANDARD IS:1192 O4002(E) ID:53 F4002(E)1Sweetened condensed milk Determination of sucrose content P

21、olarimetric method 1 Scope This International Standard specifies a polarimetric method for the determination of sucrose in sweetened condensed milk. The method is applicable to sweetened condensed milk of normal composition prepared from whole, partially skimmed or skimmed milk and sucrose only and

22、containing no altered sucrose. 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 referenced document (including any amendments) appl

23、ies. ISO 648, Laboratory glassware One-mark pipettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 1737, Evaporated milk and sweetened condensed milk Determination of fat content Gravimetric method (Reference method) 3 Terms and definitions For the purposes of this document, the foll

24、owing terms and definitions apply. 3.1 sucrose content of sweetened condensed milk content of unaltered sucrose (saccharose) determined using the method specified in this International Standard NOTE It is expressed as a mass fraction in percent. 4 Principle A test sample is treated with ammonium hyd

25、roxide, so as to bring mutarotation of lactose to final equilibrium. It is neutralized and then clarified by successive additions of zinc acetate and potassium hexacyanoferrate(II), followed by filtration. The optical rotation is determined on a portion of the filtrate. On another portion of the fil

26、trate, inversion is induced (based on the Clerget principle) by mild acid hydrolysis of the sucrose, leaving lactose and other sugars virtually unaffected. The optical rotation is determined after inversion. BSISO2911:20042 The sucrose content is calculated from the change in optical rotation on inv

27、ersion. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 5.1 Zinc acetate solution, 1,0 mol/l. Dissolve in water 21,9 g of zinc acetate dihydrate Zn(C 2 H 3 O 2 ) 2 2H 2 O and add 3 ml of glac

28、ial acetic acid. Mix and dilute to 100 ml. 5.2 Potassium hexacyanoferrate(II) solution, 0,25 mol/l. Dissolve in water 10,6 g of potassium hexacyanoferrate(II) trihydrate K 4 Fe(CN) 6 3H 2 O and dilute to 100 ml. 5.3 Dilute hydrochloric acid, c(HCl) = (6,35 0,20) mol/l 20 % to 22 % (mass fraction). 5

29、.4 Ammonium hydroxide solution, c(NH 4 OH) = (2,0 0,2) mol/l 3,5 % (mass fraction). 5.5 Dilute acetic acid, c(CH 3 CO 2 H) = (2,0 0,2) mol/l 12 % (mass fraction), of exactly known concentration. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Analytical balance, capable

30、 of weighing to the nearest 0,01 g. 6.2 Glass beaker, of capacity 100 ml. 6.3 Volumetric flasks, of capacities 200 ml and 50 ml, conforming to class A of ISO 1042. 6.4 Pipette, either 20 ml, conforming to class A of ISO 648, or 40 ml, of corresponding accuracy. 6.5 Graduated measuring cylinders, of

31、capacity 25 ml. 6.6 Graduated pipettes, of capacity 10 ml. 6.7 Filter funnel, of diameter 8 cm to 10 cm, and folded medium-grade filter papers, of diameter 15 cm. 6.8 Polarimeter tube, exactly 2 dm long. 6.9 Polarimeter or saccharimeter. 6.9.1 Polarimeter, using sodium light or mercury green light (

32、mercury vapour lamp with prism or the special Wratten screen No. 77A), capable of being read to an accuracy of at least 0,05 angular degrees. 6.9.2 Saccharimeter, with international sugar scale, using white light passing through a filter of 15 mm depth of a 6 % solution of potassium dichromate, or s

33、odium light, capable of being read to an accuracy of at least 0,1 international sugar scale degrees. 6.10 Water baths, capable of being maintained at about 40 C and at (60 1) C respectively. BSISO2911:2004 37 Sampling A representative sample should have been sent to the laboratory. It should not hav

34、e been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707 1 . 8 Procedure 8.1 Preparation of test sample 8.1.1 Samples of recently manufactured products in which no appreciable

35、 separation of components may be expected Open the container, transfer all material adhering to the lid into the container and thoroughly mix by an up- and-down movement of a spoon, in such a way that the top layers and the contents of the lower corners are moved and mixed. When the product is in a

36、can, transfer the contents to a jar with a well-fitting lid. When the product is in a collapsible tube, transfer as much as possible of the contents to a jar with a well-fitting lid, then cut open the tube, scrape out all material adhering to the interior and transfer this also to the jar. Mix the c

37、ontents of the jar as described above. 8.1.2 Samples of older products and samples in which separation of components may be expected Heat in a water bath (6.10) at about 40 C until the sample has nearly reached this temperature. Open the container and proceed as described in 8.1.1. When the product

38、is in a can or tube, transfer the contents to a jar, scrape out all material adhering to the walls (in the case of a collapsible tube, after cutting open the tube) and continue the mixing until the whole mass is homogeneous, reducing the size of any large crystals by crushing them with a glass rod.

39、Close the jar with a well-fitting lid. Allow to cool. 8.2 Check test In order to check the procedure, the reagents and the apparatus, make a check test as described below in duplicate, on a mixture of 100 g of whole milk (or 110 g of skimmed milk) and 18,00 g of pure sucrose. This mixture correspond

40、s to 40,00 g of condensed milk containing 45,0 % of sucrose. Calculate the sugar content by means of the equations in 9.1, using in Equation (2) for m, F and P respectively the quantity of milk weighed and the fat and protein content of this milk, and in Equation (1) for m, the value 40,00. The mean

41、 of the values found shall be within the range (45 0,1) % (mass fraction). 8.3 Determination 8.3.1 Weigh, to the nearest 0,01 g, a test portion of approximately 40 g of the well-mixed test sample into the glass beaker (6.2). Add 50 ml of hot water (80 C to 90 C) and mix well. 8.3.2 Transfer the mixt

42、ure quantitatively to the 200 ml volumetric flask (6.3), rinsing the beaker with successive quantities of water at 60 C, until the total volume is between 120 ml and 150 ml. Mix and cool to (20 2) C. 8.3.3 Add 5 ml of the ammonium hydroxide solution (5.4). Mix again and then allow to stand for 15 mi

43、n at (20 2) C. 8.3.4 Neutralize the ammonium hydroxide by adding the stoichiometrically equivalent quantity of the dilute acetic acid (5.5). Mix. BSISO2911:20044 8.3.5 Add, mixing gently by rotating the tilted flask, 12,5 ml of the zinc acetate solution (5.1). 8.3.6 In the same manner as for the add

44、ition of the zinc acetate solution, add 12,5 ml of the potassium hexacyanoferrate(II) solution (5.2). 8.3.7 Bring the contents of the flask to 20 C and dilute to the mark with water at 20 C. Up to this stage, all additions of water or reagents shall be made in such a manner as to avoid the formation

45、 of air bubbles and, with the same object in view, all mixing shall be carried out by rotation of the flask rather than by shaking. If air bubbles are found to be present before completion of the dilution to 200 ml, they may be removed by temporarily connecting the flask to a vacuum pump, and rotati

46、ng the flask. 8.3.8 Close the flask with a dry stopper and mix thoroughly by vigorous shaking. 8.3.9 Allow the precipitate to settle for a few minutes and then filter the solution through a dry filter paper, rejecting the first 25 ml of filtrate. 8.4 Direct polarization Determine the optical rotatio

47、n of the filtrate (8.3.9) at (20 2) C. 8.5 Inversion Pipette 40 ml (two 20 ml portions if a 40 ml pipette is unavailable) of the filtrate (8.3.9) into the 50 ml volumetric flask (6.3). Add 6,0 ml of the dilute hydrochloric acid (5.3). Place the flask in a water bath (6.10) set at 60 C for 15 min, th

48、e flask being immersed to the base of the neck. Mix by rotating the flask during the first 5 min, in which time the contents of the flask should have reached the temperature of the water bath. Cool to 20 C and dilute to the mark with water at 20 C. Mix and allow to stand for 1 h at this temperature.

49、 8.6 Invert polarization Determine the optical rotation of the inverted solution at (20 2) C. If the temperature of the liquid in the polarization tube differs by more than 0,2 C from 20 C during the measurement, the temperature correction Equation (4) given in 9.1 shall be applied. 9 Expression of results 9.1 Method of calculation and equations The sucrose content, w S , of the sample, expressed as a perce