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1、BRITISH STANDARD BS ISO 15648:2004 Butter Determination of salt content Potentiometric method ICS 67.100.20 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15648:2004 This British Standard was published under the authority of the St
2、andards Policy and Strategy Committee on 4 October 2004 BSI 4 October 2004 ISBN 0 580 44533 X National foreword This British Standard reproduces verbatim ISO 15648:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/5, M
3、ilk and milk products, which has the responsibility 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
4、under the section entitled “International 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
5、application. Compliance with a British Standard 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 informe
6、d; monitor related international and European 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 iv, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates wh
7、en the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference numbers ISO 15648:2004(E) IDF 179:2004(E) OSI DI dnaF 4002 INTERNATIONAL STANDARD ISO 15648
8、IDF 179 First edition 2004-08-15 Butter Determination of salt content Potentiometric method Beurre Dtermination de la teneur en sel Mthode potentiomtrique BS ISO 15648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:84651 O4002(E) ID
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15、02(E) I SO dna ID 4002 F All irhgts seredevr iii Foreword 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
16、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, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
17、 Electrotechnical 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for v
18、oting. 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 rights. ISO shall not be held responsible for identifying any or all s
19、uch patent rights. ISO 15648|IDF 179 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 In
20、ternational. BS ISO 15648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:84651 O4002(E) ID:971 F4002(E) iv I SO dna ID 4002 F All irhgts seredevr Foreword IDF (the International Dairy Federation) is a worldwide federation of the dai
21、ry sector with a National Committee in every member country. 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 m
22、ilk and milk products. Draft International Standards 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 IDF National Committees casting a vote. ISO 15648|IDF 179 was p
23、repared 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. All work was carried out by t
24、he Joint ISO/IDF/AOAC Action Team on Minor compounds, of the Standing Committee on Minor components and characterization of physical properties, under the aegis of its project leader, Mr G. Brthen (NO). BS ISO 15648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006,
25、 Uncontrolled Copy, (c) BSI NITERNATNOIAL STANDARD IS:84651 O4002(E) ID:971 F002(4)E I SO dna ID 4002 F All irhgts seredevr 1 Butter Determination of salt content Potentiometric method 1 Scope This International Standard specifies a method for the determination of the salt content of all types of bu
26、tter containing more than 0,1 % (mass fraction) salt. NOTE If the method is used for the analysis of butter with a low salt content, the expected relative precision figure will be higher than for salted butter; see also Reference 4. 2 Terms and definitions For the purposes of this document, the foll
27、owing terms and definitions apply. 2.1 salt content of butter mass fraction of substances determined by the procedure specified in this International Standard NOTE The salt content, being the equivalent of sodium chloride, is expressed in percent by mass. 3 Principle A test portion is suspended in w
28、ater. Chloride ions are titrated potentiometrically with a standard volumetric solution of silver nitrate. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water free from chloride, or water of equivalent purity. 4.1 Silver nitra
29、te, standard volumetric solution, of concentration in the range of c(AgNO3) = 0,08 mol/l to 0,12 mol/l. Dissolve 13,6 g to 20,4 g of silver nitrate in water which is practically free from carbon dioxide. Dilute to 1 000 ml. Standardize the silver nitrate standard volumetric solution against sodium c
30、hloride (NaCl), previously dried at 300 C for 2 h. Express the concentration of the silver nitrate standard volumetric solution to four decimal places. Store the solution protected from direct sunlight. Commercially available solutions may be used. 4.2 Nitric acid solution, c(HNO3) 4 mol/l. BS ISO 1
31、5648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:84651 O4002(E) ID:971 F4002(E) 2 I SO dna ID 4002 F All irhgts seredevr 5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Analytical balance, capable of
32、 weighing to the nearest 1 mg, with a readability of 0,1 mg. 5.2 Potentiometer, provided with a measuring electrode suitable for the determination of chloride (e.g. a silver electrode) and a reference electrode e.g. a mercury(I) sulfate electrode. 5.3 Vessel, suitable for blending and titration. 5.4
33、 Graduated cylinders, of capacities 50 ml and 100 ml. 5.5 Burette, of capacity 50 ml, graduated in 0,1 ml, or, preferably, an automatic plunger burette, readable to the nearest 0,01 ml, both made of brown glass or protected from light. 5.6 Stirrer. Suitable (semi) automatic titration apparatus may b
34、e used for 5.2 to 5.6. 5.7 Spoon or spatula. 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampl
35、ing method is given in ISO 707. Store the sample in such a way that deterioration and change in its composition are prevented. 7 Preparation of test sample Take a representative test sample. If the test sample is visibly not homogeneous, or if the history of the test sample (age, storage conditions)
36、 is such that inhomogeneity is expected, homogenize the sample as follows. a) Warm the test sample in the original unopened container, which should be from one-half to two-thirds full, to a temperature at which the sample will be soft enough to facilitate thorough mixing to a homogeneous state (eith
37、er by a mechanical shaker or by hand). Take care that the mixing temperature does not exceed 30 C. b) Cool the test sample to ambient temperature with constant mixing until cooling is complete. As soon as possible thereafter, open the sample container and stir briefly (no longer than for 10 s) with
38、a suitable device, for example a spoon or spatula (5.7), before weighing. 8 Procedure 8.1 Test portion Weigh, to the nearest 1 mg, 2 g to 4 g of the test sample (Clause 7) into the vessel (5.3). Record the mass to 0,1 mg. BS ISO 15648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40
39、:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:84651 O4002(E) ID:971 F4002(E) I SO dna ID 4002 F All irhgts seredevr 3 8.2 Determination 8.2.1 Add 100 ml of boiling water or 100 ml of cold water and heat to boiling to dissolve the test portion. Cool the obtained suspension to below 55 C. Put the
40、measuring electrode and the reference electrode of the potentiometer (5.2) into the suspension. Titrate the suspension with the silver nitrate standard volumetric solution (4.1) using the burette (5.5). Stir continuously until the endpoint has nearly been reached. Then titrate cautiously until the e
41、ndpoint is reached. NOTE The endpoint corresponds to the maximum potential difference which is observed between two successive equal additions (of about 0,05 ml) of the silver nitrate standard volumetric solution. 8.2.2 In the case of a difficult titration, the addition of 2 ml to 3 ml of nitric aci
42、d solution (4.2) to the contents of the vessel before titration is allowed. By testing this in the collaborative study (see Annex A), it was shown that the same level of precision was attained. 8.3 Blank test Carry out a blank test using all reagents but omitting the test portion. 9 Calculation and
43、expression of results 9.1 Calculation Calculate the salt content of the test sample, w, expressed as a percentage by mass, using the following equation: 10 ()5,84VVc w m = where V0 is the volume of the silver nitrate standard volumetric solution used in the blank test, in millilitres (see 8.3), V1 i
44、s the volume of the silver nitrate standard volumetric solution used in the determination, in millilitres (see 8.2); c is the numerical value of the actual concentration of the silver nitrate standard volumetric solution, in moles per litre; 5,84 is the factor transforming the experimentally obtaine
45、d amount of Cl into salt (NaCl); m is the mass of the test portion, in grams (see 8.1). 9.2 Expression of results Express the test results to two decimal places. BS ISO 15648:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:07 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:84651 O400
46、2(E) ID:971 F4002(E) 4 I SO dna ID 4002 F All irhgts seredevr 10 Precision 10.1 Interlaboratory test Details of an interlaboratory test on the precision of the method are summarized in Annex A. The values derived from this interlaboratory test may not be applicable to concentration ranges and matric
47、es other than those given. 10.2 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 same equipment within a short interval of time, will in not more than 5 %
48、 of cases be greater than a mass fraction of 0,05 %. 10.3 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, will in not more than 5 % of case
49、s be greater than a mass fraction of 0,08 %. 11 Test report The test report shall specify: a) all information necessary for the complete identification of the sample; b) the sampling method used, if known; c) the test method used, with reference to this International Standard; d) all operational details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test