BS ISO 1739-2007 Butter - Determination of the refractive index of the fat (reference method)《奶油 脂肪折射率的测定(参照法)》.pdf

1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58fat (Reference method)ICS 67.100.20Butter Determination of the refractive index of the BRITISH STAN

2、DARDBS ISO 1739:2006BS ISO 1739:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2007 BSI 2007ISBN 978 0 580 50126 5Amendments issued since publicationAmd. No. Date Commentscontract. Users are responsible for its correct applica

3、tion.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 1739:2006.The UK participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk

4、 and milk products.A list of organizations represented on AW/5 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a Reference numbersISO 1739:2006(E)IDF 7:2006(E)INTERNATIONAL STANDARD ISO1739IDF7Second edition2006-12-01Butter Det

5、ermination of the refractive index of the fat (Reference method) Beurre Dtermination de lindice de rfraction de la matire grasse (Mthode de rfrence) BS ISO 1739:2006ii iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO mem

6、ber 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, governmen

7、tal 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. International Standards are drafted in accordance with the rules given in the ISO/IEC Direc

8、tives, 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. Publication as an International Standard requires approval by at least 75 % of the member bodi

9、es 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 rights. ISO 1739IDF 7 was prepared by Technical Committee ISO/TC 34, Food products, Subcom

10、mittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This edition of ISO 1739IDF 7 cancels and replaces ISO1739:1975, of which it constitutes a minor revision. BS ISO 1739:2006iv Foreword IDF (the International Dairy Federat

11、ion) 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 technical work. IDF collaborates with ISO in the development of standard methods of analysis

12、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. Publication as an International Standard requires approval by at least 50 % of the IDF National Committees casting a vote.

13、Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 1739IDF 7 was prepared by the International Dairy Federation (IDF) and Technical Committee ISO/TC

14、 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. This edition of ISO 1739IDF 7 cancels and replaces IDF 7A:1969, of which it constitutes a minor revision. All work was carried out by the former Joint ISO/IDF/AOAC Group of Experts on Fat (E4

15、0-E301). BS ISO 1739:20061Butter Determination of the refractive index of the fat (Reference method) 1 Scope This International Standard specifies a reference method for the determination of the refractive index of the fat obtained by melting butter. 2 Normative references The following referenced d

16、ocuments 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) applies. ISO 1740, Milkfat products and butter Determination of fat acidity (Referen

17、ce method) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 refractive index of the fat from butter ratio, at 40 C, of the velocity of light of a defined wavelength (the mean of D-lines of sodium) in air to its velocity in the fat NOTE In theo

18、ry, there are two D-lines of sodium and the ratio should be referred to the velocity of light in vacuum, not in air. In practice, sodium light may be considered monochromatic, and the ratio related to that in air. 4 Principle The refractive index of the fat obtained by melting butter is measured by

19、means of a suitable refractometer. 5 Apparatus 5.1 Refractometer, with a scale graduated in refractive index units to the third decimal place, and having prisms heated by means of a circulating liquid at 40 C, the temperature being thermostatically controlled to within 0,1 C. 5.2 Light source, sodiu

20、m vapour lamp. White light may also be used if the refractometer is fitted with an achromatic compensating device. BS ISO 1739:20062 6 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 par

21、t of the method specified in this International Standard. A recommended sampling method is given in ISO 707IDF 50. 7 Procedure 7.1 Preparation of test sample To separate the fat, melt the sample and allow it to stand for 2 h to 3 h at 50 C to 60 C. Then decant and filter it through a dry filter pape

22、r. Filter again if the filtrate obtained is not clear. Use the melted and clarified fat, well mixed and free from water. 7.2 Determination Prepare the refractometer and calibrate it by following the makers instructions for using the instrument. Adjust the temperature of the circulating liquid to (40

23、 0,1) C. Place a few drops of fat (prepared as described in 7.1) between the prisms of the refractometer in such a way that the space between the prisms is completely filled. Wait for a few minutes to allow the fat to assume the temperature of the prisms. Take the reading, estimating to tenths of a

24、scale division (i.e. the fourth decimal place). Carry out two determinations on the same prepared sample. 8 Expression of results 8.1 Correction Correct the observed refractive index by adding 0,000 045 for each unit of the acid value if the latter, when determined by the method specified in ISO 174

25、0, is equal to or greater than 2. 8.2 Method of calculation Take as the result the arithmetic mean of the two results, corrected if necessary, if the requirement concerning repeatability (see Clause 9) is satisfied. Round the result to the fourth decimal place. 9 Repeatability The difference between

26、 the results of two determinations carried out in rapid succession by the same analyst should not exceed 0,000 2. BS ISO 1739:2006310 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 t

27、est method used, with reference to this International Standard; d) 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); e) the test result(s) obtained or, if the repeatability

28、 has been checked, the final quoted result obtained. BS ISO 1739:20064 Bibliography 1 ISO 707IDF 50, Milk and milk products Guidance on sampling BS ISO 1739:2006blankBS ISO BSI389 Chiswick High RoadLondonW4 4AL1739:2006BSI British Standards InstitutionBSI is the independent national body responsible

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