1、BS EN ISO7208:2008ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDSkimmed milk, wheyand buttermilk Determination of fatcontent Gravimetricmethod (Referencemethod)(ISO 7208:2008)This British Standard was published under theauthority of the StandardsP
2、olicy and StrategyCommittee on 31 January2009 BSI 2009ISBN 978 0 580 63538 0Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 7208:2008National forewordThis British Standard is the UK implementation of EN ISO 7208:2008. Itsupersedes BS EN ISO 7208:2000 which is withdrawn.The UK pa
3、rticipation in its preparation was entrusted to TechnicalCommittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract
4、. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 7208October 2008ICS 67.100.10 Supersedes EN ISO 7208:1999 English VersionSkimmed milk, whey and buttermilk - Deter
5、mination of fatcontent - Gravimetric method (Reference method)(ISO7208:2008)Lait crm, srum et babeurre - Dtermination de lateneur en matire grasse - Mthode gravimtrique(Mthode de rfrence) (ISO 7208:2008)Magermilch, Molke und Buttermilch - Bestimmung desFettgehaltes - Gravimetrisches Verfahren(Refere
6、nzverfahren) (ISO 7208:2008)This European Standard was approved by CEN on 14 October 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lis
7、ts and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the respon
8、sibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Icelan
9、d, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassa
10、rt, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 7208:2008: EBS EN ISO 7208:2008EN ISO 7208:2008 (E) 3 Foreword This document (EN ISO 7208:2008) has been prepared by Technical Committee ISO/TC 34 “Agric
11、ultural food products“ in collaboration with Technical Committee CEN/TC 302 “Milk and milk products - Methods of sampling and analysis” the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by e
12、ndorsement, at the latest by April 2009, and conflicting national standards shall be withdrawn at the latest by April 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for ident
13、ifying any or all such patent rights. This document supersedes EN ISO 7208:1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denma
14、rk, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 7208:2008 has been approved
15、 by CEN as an EN ISO 7208:2008 without any modification. BS EN ISO 7208:2008ISO 7208:2008(E) IDF 22:2008(E) ISO and IDF 2008 All rights reserved iiiContents Page Foreword iv Foreword. v 1 Scope 1 2 Normative references 1 3 Terms and definitions .1 4 Principle2 5 Reagents.2 6 Apparatus .2 7 Sampling.
16、3 8 Preparation of test sample4 9 Procedure .4 9.1 Test portion 4 9.2 Blank tests4 9.3 Preparation of fat-collecting vessel.5 9.4 Determination.5 10 Calculation and expression of results.7 10.1 Calculation7 10.2 Expression of results 7 11 Precision.8 11.1 Interlaboratory test 8 11.2 Repeatability.8
17、11.3 Reproducibility.8 12 Test report 8 Annex A (informative) Notes on procedures 9 Annex B (informative) Alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings .11 Bibliography 14 BS EN ISO 7208:2008ISO 7208:2008(E) IDF 22:2008(E) iv ISO and IDF 2008 All rights reserve
18、dForeword 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 member body interested in a subject for which a
19、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 Electrotechnical Commission (IEC) on all matter
20、s of electrotechnical standardization. International 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 circulat
21、ed to 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
22、 for identifying any or all such patent rights. ISO 7208IDF 22 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This third edition of ISO 7208IDF 22 can
23、cels and replaces the second edition (ISO 7208:1999), of which it constitutes a minor revision. BS EN ISO 7208:2008ISO 7208:2008(E) IDF 22:2008(E) ISO and IDF 2008 All rights reserved vForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldw
24、ide. IDF membership comprises National Committees in every member country as well as regional dairy associations having signed a formal agreement on cooperation with IDF. All members of IDF have the right to be represented at the IDF Standing Committees carrying out the technical work. IDF collabora
25、tes with ISO 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. Publication as an International Standard requires approval
26、by at least 50 % of the IDF National Committees casting a vote. 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 7208IDF 22 was prepared by the In
27、ternational Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. All work was carried out by the Joint ISO-IDF Action Team Fat of the Standing Committee on Main components in milk under the a
28、egis of its project leader, Mr G.J. Beutick (NL). This edition of ISO 7208IDF 22 cancels and replaces IDF 22:1987, of which it constitutes a minor revision. BS EN ISO 7208:2008BS EN ISO 7208:2008INTERNATIONAL STANDARD ISO 7208:2008(E)IDF 22:2008(E) ISO and IDF 2008 All rights reserved 1Skimmed milk,
29、 whey and buttermilk Determination of fat content Gravimetric method (Reference method) WARNING The use of this International Standard may involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety problems associated with its use. I
30、t is the responsibility of the user of this International Standard to establish safety and health practices and determine the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies the reference method for the determination of the fat content of liquid sk
31、immed milk, whey and buttermilk. It is a particularly accurate gravimetric method especially for the purpose of establishing the operating efficiency of cream separators. This International Standard also specifies the reference method for establishing correction tables for procedures with skimmed mi
32、lk butyrometers. NOTE When a high accuracy of determination is not required, the method specified in ISO 1211IDF 12is suitable. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For
33、undated references, the latest edition of the referenced document (including any amendments) applies. ISO 835, Laboratory glassware Graduated pipettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 3889IDF 219, Milk and milk products Specification of Mojonnier-type fat extraction flas
34、ks ISO 4788, Laboratory glassware Graduated measuring cylinders 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 fat content of skimmed milk, whey and buttermilk mass fraction of substances determined by the procedure specified in this Interna
35、tional Standard NOTE The fat content is expressed as a percentage mass fraction. BS EN ISO 7208:2008ISO 7208:2008(E) IDF 22:2008(E) 2 ISO and IDF 2008 All rights reserved4 Principle An ammoniacal ethanolic solution of a test portion is extracted with diethyl ether and light petroleum. The solvents a
36、re removed by distillation or evaporation. The mass of the substances extracted is determined. NOTE This is usually known as the Rse-Gottlieb principle. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and only distilled or demineralized water or water of equi
37、valent purity. The reagents shall leave no appreciable residue when the determination is carried out by the method specified (see 9.2.2). 5.1 Ammonia solution, containing a mass fraction of NH3of approximately 25 % (20= 910 g/l). NOTE If ammonia solution of this concentration is not available, a mor
38、e concentrated solution of known concentration may be used (see 9.4.2). 5.2 Ethanol (C2H5OH), or ethanol denatured by methanol, containing a volume fraction of ethanol of at least 94 %. (See Clause A.5.) 5.3 Congo red solution Dissolve 1 g of Congo red (C32H22N6Na2O6S2) in water in a 100 ml one-mark
39、 volumetric flask (6.14). Make up to the mark with water. NOTE The use of this solution, which allows the interface between the solvent and aqueous layers to be seen more clearly, is optional (see 9.4.3). Other aqueous indicator solutions can be used provided that they do not affect the result of th
40、e determination. 5.4 Diethyl ether (C2H5OC2H5), free from peroxides (see Clause A.3), containing no more than 2 mg/kg of antioxidants, and complying with the requirements for the blank test (see 9.2.2, Clauses A.1 and A.4). WARNING The use of diethyl ether can lead to hazardous situations. Observe c
41、urrent safety precautions for handling, use, and disposal. 5.5 Light petroleum, with any boiling range between 30 C and 60 C or, as equivalent, pentane (CH3CH23CH3) with a boiling point of 36 C and complying with the requirements for the blank test (see 9.2.2, Clauses A.1 and A.4). The use of pentan
42、e is recommended because of its higher purity and consistent quality. 5.6 Mixed solvent. Shortly before use, mix equal volumes of diethyl ether (5.4) and light petroleum (5.5). 6 Apparatus WARNING Since the determination involves the use of volatile flammable solvents, all electrical apparatus emplo
43、yed shall comply with legislation relating to the hazards in using such solvents. Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. BS EN ISO 7208:2008ISO 7208:2008(E) IDF 22:2008(E) ISO and ID
44、F 2008 All rights reserved 36.2 Centrifuge, capable of holding the fat-extraction flasks or tubes (6.6) and capable of spinning at a rotational frequency of 500 min1to 600 min1to produce a radial acceleration of 80g to 90g at the outer end of the flasks or tubes. The use of the centrifuge is optiona
45、l but recommended (see 9.4.6). 6.3 Distillation or evaporation apparatus, for distilling the solvents and ethanol from the boiling or conical flasks, or evaporating from beakers and dishes (see 9.4.13) at a temperature not exceeding 100 C. 6.4 Drying oven, electrically heated, with ventilation port(
46、s) fully open, capable of being maintained at a temperature of 102 C 2 C throughout its working space. The oven shall be fitted with a suitable thermometer. 6.5 Water bath, capable of being maintained at a temperature of between 35 C and 40 C. 6.6 Mojonnier-type fat-extraction flasks, as specified i
47、n ISO 3889IDF 219. NOTE It is also possible to use fat-extraction tubes, with siphon or wash-bottle fittings, but then the procedure is different. The alternative procedure is given in Annex B. The fat-extraction flasks shall be provided with good quality cork bungs or stoppers of other material (e.
48、g. silicone rubber or polytetrafluoroethylene) unaffected by the reagents used. Cork bungs shall be extracted with the diethyl ether (5.4), kept in water at a temperature of 60 C or more for at least 15 min, and shall then be allowed to cool in the water so that they are saturated when used. 6.7 Rac
49、k, for holding the fat-extraction flasks (or tubes) (6.6). 6.8 Wash bottle, suitable for use with the mixed solvent (5.6). A plastics wash bottle shall not be used. 6.9 Fat-collecting vessels, such as boiling flasks (flat-bottomed), of capacities 125 ml to 250 ml, conical flasks, of capacity 250 ml, or metal dishes. If metal dishes are used, they shall be of stainless steel, flat-bottomed with a diameter of 80 mm to 100 mm and a height of approximately 50 mm. 6.10 Boiling aids, fat-free, of non-porou
