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1、 Reference numbers ISO 15648:2004(E) IDF 179:2004(E) ISO and IDF 2004 INTERNATIONAL STANDARD ISO 15648 IDF 179 First edition 2004-08-15 Butter Determination of salt content Potentiometric method Beurre Dtermination de la teneur en sel Mthode potentiomtrique Copyright International Organization for S
2、tandardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:2004(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordan
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5、ptimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies and IDF national committees. In the unlikely event that a problem relating to it is found, please inform the ISO Central Secretariat at the address given below. ISO and IDF 2004 All righ
6、ts reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respective address below. ISO copyright office I
7、nternational Dairy Federation Case postale 56 CH-1211 Geneva 20 Diamant Building Boulevard Auguste Reyers 80 B-1030 Brussels Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Publ
8、ished in Switzerland ii ISO and IDF 2004 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO
9、 15648:2004(E) IDF 179:2004(E) ISO and IDF 2004 All rights reserved 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 tech
10、nical 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, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
11、 with the International 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
12、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 rights. ISO shall not be held responsible for i
13、dentifying any or all such 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 an
14、d separately by AOAC International. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:20
15、04(E) iv ISO and IDF 2004 All rights reserved Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy 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 te
16、chnical 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 adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publicati
17、on as an International Standard requires approval by at least 50% of IDF National Committees casting a vote. 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
18、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 Action Team on Minor compounds, of the Standing Committee on Minor components and characterization of physical properties, under the aegis of its
19、project leader, Mr G. Brthen (NO). Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO 15
20、648:2004(E) IDF 179:2004(E) ISO and IDF 2004 All rights reserved 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 butter containing more than 0,1 % (mass fraction) salt. NOTE
21、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 following terms and definitions apply. 2.1 salt content of butt
22、er 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 water. Chloride ions are titrated potentiometrically with a
23、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 nitrate, standard volumetric solution, of concentration in the r
24、ange 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 chloride (NaCl), previously dried at 300 C for 2 h. Express
25、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. Copyright International Organization for Standardization Provided b
26、y IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:2004(E) 2 ISO and IDF 2004 All rights reserved 5 Apparatus Usual laboratory apparatus and, in particular,
27、 the following. 5.1 Analytical balance, capable of 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.
28、3 Vessel, suitable for blending and titration. 5.4 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. S
29、uitable (semi) automatic titration apparatus may be 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 i
30、n this International Standard. A recommended sampling 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 hi
31、story of the test sample (age, storage conditions) 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 facil
32、itate thorough mixing to a homogeneous state (either 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 containe
33、r and stir briefly (no longer than for 10 s) with 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. Copyright International Orga
34、nization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:2004(E) ISO and IDF 2004 All rights reserved 3 8.2 Determination 8
35、.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 measuring electrode and the reference electrode of the potentiometer (5.2) into the suspension. Titrate the suspension with the silver nitrat
36、e standard volumetric solution (4.1) using the burette (5.5). Stir continuously until the endpoint has nearly been reached. Then titrate cautiously until the endpoint is reached. NOTE The endpoint corresponds to the maximum potential difference which is observed between two successive equal addition
37、s (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 acid 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
38、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 expression of results 9.1 Calculation Calculate the salt content of the test sample, w, expressed as a percentage by mass, using the followin
39、g 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 is the volume of the silver nitrate standard volumetric solution used in the determination, in millilitres (see 8.2); c is the numerical value
40、 of the actual concentration of the silver nitrate standard volumetric solution, in moles per litre; 5,84 is the factor transforming the experimentally obtained 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
41、 two decimal places. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:2004(E) 4 ISO and
42、 IDF 2004 All rights reserved 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 matrices other than those given. 10.2
43、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 % of cases be greater than a mass
44、 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 cases be greater than a mass fractio
45、n 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 Inter
46、national Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s); e) the test result(s) obtained and, if the repeatability has been checked, the final quoted result obtained. Copyright International Organization for Standardization Provi
47、ded by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/23/2007 02:51:47 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 15648:2004(E) IDF 179:2004(E) ISO and IDF 2004 All rights reserved 5 Annex A (informative) Results of the interlaboratory
48、test A.1 An international collaborative test involving eleven laboratories was carried out on six butter samples, each divided in two equal samples (blind duplicates) so as to obtain 12 test samples. The Norwegian Institute for Food and Environmental Analysis organized the test. The results obtained were subjected to statistical analysis in accordance with ISO 5725-1 and ISO 5725-2 to give the precision data shown in Table A.1. Based on the obtained results, the