1、BRITISH STANDARD BS ISO 15884:2002 Milk fat Preparation of fatty acid methyl esters ICS 67.100.10 BS ISO 15884:2002 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 January 2003 BSI 28 January 2003 ISBN 0 580 41154 0 National foreword This
2、British Standard reproduces verbatim ISO 15884:2002 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has the responsibility to: A list of organizations represented on this committee can be
3、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 “International Standards Correspondence Index”, or by using the “Search” facility of the B
4、SI 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 Standard does not of itself confer immunity from legal obligations. aid enquir
5、ers 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 European developments and promulgate them in the UK. Summary of pages This docum
6、ent comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 6, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Refer
7、ence numbers ISO 15884:2002(E) IDF 182:2002(E)INTERNATIONAL STANDARD ISO 15884 IDF 182 First edition 2002-11-15 Milk fat Preparation of fatty acid methyl esters Matires grasses du lait Prparation des esters mthyliques dacides gras BSISO15884:2002IS:48851 O2002(E) ID:281 F2002(E) DPlcsid Fremia ihTs
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13、-lidif.org We bwww.is.o gro We bwww.fil-ifd. groii ISO dnaID 2002 FA ll rihgtsser devreBSISO15884:2002 iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is nor
14、mally 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, governmental and non-governmental, in liaison with ISO, also take part in
15、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 Directives, Part 2. The main task of technical committees is to prepar
16、e 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 bodies casting a vote. Attention is drawn to the possibility that som
17、e 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 15884 IDF 182 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Da
18、iry Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. BSISO15884:2002iv Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every memb
19、er 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 milk and milk products. Draft International Standa
20、rds 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 15884 IDF 182 was prepared by Technical Committee ISO/TC 34, Food p
21、roducts, 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 Action Team, Fat, of the S
22、tanding Committee on Main Components in Milk, under the aegis of its project leader, Dr F. Ulberth (AT). BSISO15884:2002NITERNATNOIAL STANDARD IS:48851 O2002(E) ID:281 F2002(E)1Milk fat Preparation of fatty acid methyl esters 1 Scope This International Standard specifies a method for the preparation
23、 of fatty acid methyl esters from milk fat and fat obtained from dairy products. The method is not suitable for the analysis of partially lipolysed milk fat (fat acidity 1 mmol of free fatty acids per 100 g of fat). In such a case, the alternative method described in Annex A can be used. 2 Normative
24、 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) applies. ISO 2446, Milk Determination of fat c
25、ontent (Routine method) ISO 14156 IDF 172, Milk and milk products Extraction methods for lipids and liposoluble compounds ISO 15885 IDF 184, Milk fat Determination of the fatty acid composition by gas-liquid chromatography 3 Terms and definitions For the purposes of this document, the following term
26、s and definitions apply. 3.1 fatty acid methyl esters of milk fat methyl esters of fatty acids prepared by the procedure specified in this International Standard 4 Principle Methyl esters of milk fat fatty acids are prepared by base-catalysed methanolysis of the glycerides in an essentially non-alco
27、holic solution. After a certain reaction time, the mixture is neutralized by the addition of crystalline sodium hydrogen sulfate to avoid saponification of preformed esters. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water
28、or water of equivalent purity. 5.1 Solvent: n-pentane, n-hexane or n-heptane. 5.2 Methanol, containing not more than a mass fraction of 0,5 % water. BSISO15884:20022 5.3 Sodium hydrogen sulfate monohydrate (NaHSO 4 H 2 O). 5.4 Transesterification reagent, potassium hydroxide (KOH) or sodium methoxid
29、e (NaOCH 3 ), methanolic solution of approximately 2 mol/l. Dissolve 11,2 g of KOH in 100 ml of methanol and mix well. Alternatively, dissolve 10,8 g of NaOCH 3in 100 ml of methanol and mix well. The sodium methoxide methanolic solution may also be prepared by dissolving 4,6 g of metallic sodium in
30、methanol or by diluting a commercially available solution of approximately 5,4 mol/l (e.g. Fluka 71748 1) ). Special precautions, however, shall be taken when handling metallic sodium. 6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Balance, capable of weighing to the n
31、earest 1 mg. 6.2 Test tube, of diameter 16 mm, of length 100 mm, fitted with PTFE-lined screw cap. 6.3 Graduated pipettes, of capacity 1 ml and 10 ml. 6.4 Vortex mixer. 6.5 Centrifuge, capable of operating at 350 g 50 g. It shall also be provided with a speed indicator indicating the number of revol
32、utions per minute, with a maximum tolerance of 50 r/min. For acceleration details, see ISO 2446. 7 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
33、 in this International Standard. A recommended sampling method is given in ISO 707. 8 Preparation of test sample Follow the extraction method specified in ISO 14156 IDF 172. The extracted fat may be stored in a freezer for no longer than 1 month. 9 Procedure Weigh, to the nearest 5 mg, 100 mg of the
34、 prepared test sample (Clause 8) in a test tube (6.2). Dissolve the test portion sample in 5 ml of solvent (5.1) and mix. Add 0,2 ml of the transesterification reagent (5.4) and cap the tube. 1) Fluka is the tradename of a reagent commercially available. This information is given for the convenience
35、 of users of this International Standard and does not constitute an endorsement by ISO or IDF of this product. BSISO15884:2002 3Mix the contents of the tube vigorously with the vortex mixer (6.4) for 1 min. After an additional reaction time of 5 min, add 0,5 g of solid sodium hydrogen sulfate (5.3)
36、and mix again. Place the test tubes with the test portion in the centrifuge (6.5) and centrifuge for 3 min at room temperature. After centrifuging, take an aliquot from the obtained clear supernatant of the test portion for the gas-liquid chromatographic analysis. Proceed as specified in ISO 15885 I
37、DF 184. If necessary, decant the ester solution and store it at normal refrigeration temperatures or, preferably, in a deep-freezer for several days. Precautions shall be taken to avoid losses due to the volatility of methyl esters of milk fat fatty acids. NOTE N-Acyl lipids (e.g. sphingolipids) are
38、 not properly transesterified by base-catalysed methanolysis. These substances occur primarily in lipids of products derived from whey. 10 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)
39、the test method used, together 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). BSISO15884:20024 Annex A (normative) Alte
40、rnative procedure using acid-catalysed transesterification of glycerides A.1 Introduction If a partially hydrolysed milk fat is to be converted to fatty acid methyl esters, use acid-catalysed transesterification of glyceride-bound acids with concomitant esterification of free fatty acids as specifie
41、d in this annex. A.2 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. A.2.1 Sulfuric acid, 20(H 2 SO 4 ) = 1,84 g/ml. A.2.2 Methanol, containing not more than a mass fraction of 0,5 % water. A.2
42、.3 Esterification reagent. While cooling, add slowly 1 ml of sulfuric acid (A.2.1) to 15 ml of methanol (A.2.2). A.3 Apparatus Usual laboratory equipment and, in particular, the following. A.3.1 Balance, capable of weighing to the nearest 10 mg. A.3.2 Graduated pipettes, of capacities 1 ml and 5 ml.
43、 A.3.3 Glass ampoules, of capacity 5 ml. Instead of glass ampoules, another suitable derivatization vial of similar dimensions may be used, provided that a leaktight closure prevents losses of volatile esters. A.3.4 Oven, capable of operating at between 100 C and 110 C, or water bath, capable of boi
44、ling. A.4 Preparation of test sample Prepare the test sample as specified in Clause 8. BSISO15884:2002 5A.5 Procedure Weigh, to the nearest 10 mg, 2 g of the prepared sample into a glass ampoule (A.3.3). Add 0,4 ml of esterification reagent (A.2.3). Flame seal the glass ampoule. Heat the glass ampou
45、le and its contents for 3 h in the oven (A.3.4) set at between 100 C and 110 C, with intermittent mixing of the ampoule contents. Cool the glass ampoule and its contents to room temperature and allow for complete phase separation. Open the glass ampoule and take an aliquot of the upper phase for fur
46、ther analysis. Dilution of the formed esters with an appropriate solvent may be necessary. BSISO15884:20026 Bibliography 1 ISO 707, Milk and milk products Guidance on sampling BSISO15884:2002BS ISO 15884:2002 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the indep
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