1、BRITISH STANDARD BS ISO 1740:2004 Milkfat products and butter Determination of fat acidity (Reference method) ICS 67.100.10; 67.100.30 BS ISO 1740:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 7 December 2004 BSI 7 December 2004 ISBN 0
2、 580 44984 X National foreword This British Standard reproduces verbatim ISO 1740:2004 and implements it as the UK national standard. It supersedes BS 5086-6:1992 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has
3、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 under the section entitled “Inter
4、national 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 application. Compliance with a Br
5、itish 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 informed; monitor related international
6、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 v, a blank page, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was
7、last issued. Amendments issued since publication Amd. No. Date Comments Reference numbers ISO 1740:2004(E) IDF 6:2004(E) OSI DI dnaF 4002INTERNATIONAL STANDARD ISO 1740 IDF 6 Third edition 2004-12-01 Milkfat products and butter Determination of fat acidity (Reference method) Produits matire grasse l
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14、Contents Foreword iv 1 Scope 1 2 Terms and definitions. 1 3 Principle . 1 4 Reagents 1 5 Apparatus. 2 6 Sampling 3 7 Procedure. 3 7.1 Preparation of test sample. 3 7.2 Test portion . 3 7.3 Determination 4 7.4 Blank test . 4 7.5 Check test 4 8 Expression of results 4 9 Precision 5 9.1 Interlaboratory
15、 test . 5 9.2 Repeatability 5 9.3 Reproducibility 5 10 Test report 6 Bibliography . 7 BSISO1740:2004IS:0471 O4002(E) ID:6 F4002(E) iv I SO dna ID 4002 F All irhgts seredevrForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO me
16、mber 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, governme
17、ntal 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 Dire
18、ctives, 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 bod
19、ies 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 1740 IDF 6 was prepared by Technical Committee ISO/TC 34, Food products, Subc
20、ommittee 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. This edition of ISO 1740 IDF 6 cancels and replaces ISO 1740:1991, of which it constitutes
21、 a minor revision. Only editorial changes have been made. BSISO1740:2004IS:0471 O4002(E) ID:6 F4002(E) I SO dna ID 4002 F All irhgts seredevr vForeword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every member country. Every Nati
22、onal 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 Standards adopted by the Act
23、ion 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 1740 IDF 6 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC
24、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 Group of Experts, Free fatty acids (E39), under the
25、 aegis of its project leader, Mr A. Jellema (NL). This edition of ISO 1740 IDF 6 cancels and replaces IDF 6B:1989. Only editorial changes have been made. BSISO1740:2004blank 4002:0471OSISBNITERNATNOIAL STANDARD IS:0471 O4002(E) ID:6 F4002(E)I SO dna ID 4002 F All irhgts seredevr 1Milkfat products an
26、d butter Determination of fat acidity (Reference method) 1 Scope This International Standard specifies a method for the determination of the acidity of the fat contained in milkfat products 1)and in butter. 2 Terms and definitions For the purposes of this document, the following terms and definition
27、s apply. 2.1 fat acidity of a milkfat product or butter amount of alkali required to neutralize the free fatty acids in the test portion, as determined using the method specified in this International Standard, divided by the mass of the test portion NOTE 1 The fat acidity is expressed in millimoles
28、 per 100 g of fat. NOTE 2 The following alternative methods of expression of fat acidity have been used in the past but they are no longer recommended: a) the number of milligrams of potassium hydroxide required to neutralize the free acids contained in 1 g of fat (equal to the acid value); b) the n
29、umber of grams of oleic acid per 100 g of fat (equal to the percentage of free fatty acids). 3 Principle In the particular case of butter, the fat is first separated from the melted butter by centrifuging. In an oven, the melted milkfat product or fat from butter is filtered through a filter paper.
30、The filtrate is dissolved in a mixture of propan-2-ol and light petroleum, then titrated with tetra-n- butylammonium hydroxide standard solution using thymol blue as indicator. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized wat
31、er or water of equivalent purity. 1) As defined in FAO/WHO Standard A-2, Section A for anhydrous milkfat and anhydrous butter oil, and Section B for ghee. BSISO1740:2004IS:0471 O4002(E) ID:6 F4002(E) 2 I SO 4002 All irthgs ersedevr4.1 Tetra-n-butylammonium hydroxide standard solution, c(C 16 H 37 NO
32、) = 0,1 mol/l, in propan-2- ol/methanol mixture, 3 + 1 (volume fraction). The concentration of the tetra-n-butylammonium hydroxide standard solution may change on storage and when being transferred to the burette. For these reasons, the actual concentration of the solution should be determined to fo
33、ur decimal places immediately before use by titration against a standard solution of potassium hydrogen phthalate (KHC 8 H 4 O 4 ) using thymol blue as indicator. However, if the burette is fitted with a facility to exclude the entry of carbon dioxide, the concentration of the tetra-n-butylammonium
34、hydroxide standard solution is stable for longer periods. In this case the actual concentration of the solution need be checked only for each series of determinations by carrying out a check test (7.5) using the reference fat (4.4). 4.2 Thymol blue solution, (C 27 H 30 O 5 S) = 0,1 g/l, in propan-2-
35、ol. Dissolve 0,1 g of sodium salt of thymol blue in 100 ml of propan-2-ol to prepare a stock solution. Before use, dilute one volume of this stock solution with nine volumes of propan-2-ol. 4.3 Fat solvent 4.3.1 Mix one volume of thymol blue solution (4.2) with four volumes of light petroleum (boili
36、ng range 60 C to 80 C). Store this mixture in the dark. The mixture may be stored for up to 1 month. 4.3.2 If blank tests (7.4) give high results, neutralize the fat solvent with the tetra-n-butylammonium hydroxide standard solution (4.1) until a faint greenish colour is obtained. 4.4 Reference fat
37、(for checking periodically the whole titration procedure). 4.4.1 Preparation of reference fat samples Dissolve known quantities of palmitic acid (C 16 H 32 O 2 ) in washed milkfat (see 4.4.2). Suitable concentrations of palmitic acid are 0,5 mmol to 2,0 mmol of palmitic acid per 100 g of fat. Calcul
38、ate the fat acidity of the reference fat samples in millimoles of palmitic acid present in 100 g of reference fat. NOTE This calculated value may serve as a reference value. 4.4.2 Washed milkfat Wash a good quality milkfat 2)with aqueous potassium hydroxide solution c(KOH) = 0,1 mol/l. Then wash wit
39、h water, centrifuge and filter though a filter paper. 4.4.3 Storage Dispense the reference fat into bottles and seal them hermetically. If the fat is to be used within 4 weeks, the bottles may be stored in the dark at a temperature not exceeding 4 C. If it is necessary to keep the fat for a longer p
40、eriod, freeze it immediately and store in the dark. 5 Apparatus Usual laboratory apparatus and, in particular, the following. 2) For the specification of “good quality”, see FAO/WHO Standard A-2, Section A. BSISO1740:2004IS:0471 O4002(E) ID:6 F4002(E) I SO 4002 All irthgs ersedevr 35.1 Analytical ba
41、lance, capable of weighing to the nearest 0,01 g. 5.2 Centrifuge, capable of producing a radial acceleration of at least 350 g, with a swing-out rotor, for example a so-called Gerber centrifuge (see ISO 2446 2 ). 5.3 Centrifuge tubes. 5.4 Glass funnels and filter paper (medium grade). 5.5 Delivery p
42、ipettes or syringes, of capacity 5 ml to 10 ml. 5.6 Delivery pipettes or syringes, of capacity 50 ml 0,5 ml. 5.7 Titration vessels, for example conical flasks of capacity approximately 100 ml to 250 ml. 5.8 Burette, graduated in divisions of 0,02 ml. 5.9 Nitrogen, free from carbon dioxide. 5.10 Oven
43、, electrically heated, capable of being maintained at 50 C 2 C. 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 part of the method specified in this International Standard. A recommend
44、ed sampling method is given in ISO 707 1 . 7 Procedure 7.1 Preparation of test sample 7.1.1 Butter Set the oven (5.10) at 50 C. Melt an appropriate quantity of the sample in a centrifuge tube (5.3) in the oven and separate the fat by centrifuging at a radial acceleration of at least 350 g in the cen
45、trifuge (5.2) for 5 min. Filter the warm separated butterfat through a folded dry filter paper in the oven. The filtered butterfat shall be clear and visibly free from water and non-fatty compounds. 7.1.2 Milkfat products (anhydrous milkfat, anhydrous butter oil or anhydrous butterfat, butter oil, b
46、utterfat or ghee). Set the oven (5.10) at 50 C. Melt an appropriate quantity of the milkfat product in the oven and filter it through a folded dry filter paper in the oven. 7.2 Test portion Weigh, to the nearest 0,01 g, 5 g to 10 g of the test sample (7.1) into a titration vessel (5.7), transferring
47、 the fat using a pipette or syringe (5.5). BSISO1740:2004IS:0471 O4002(E) ID:6 F4002(E) 4 I SO 4002 All irthgs ersedevr7.3 Determination 7.3.1 Add to the test portion (7.2) 50 ml of the fat solvent (4.3) using a pipette or syringe (5.6) and dissolve the fat. 7.3.2 Titrate the dissolved fat with the
48、tetra-n-butylammonium hydroxide standard solution (4.1) under a flow of nitrogen (5.9) until a yellow to faint greenish colour persists for at least 5 s. Record the volume of solution (4.1) used to the nearest 0,01 ml. IMPORTANT To meet the requirements for precision, it is essential to exclude carb
49、on dioxide from the titration vessel during the titration procedure; this can be achieved by carrying out the titration in an atmosphere of nitrogen. Alternatively, the titration procedure may be carried out using automatic titration equipment and colorimetric determination of the endpoint of the titration (see 6 and 7). 7.4 Blank test Carry out a blank test simultaneously with the determination, using the same procedu
