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1、BRITISH STANDARD BS ISO 1740:2004 Milkfat products and butter Determination of fat acidity (Reference method) ICS 67.100.10; 67.100.30 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 1740:2004 This British Standard was published und
2、er the authority of the Standards Policy and Strategy Committee on 7 December 2004 BSI 7 December 2004 ISBN 0 580 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 It supersedes BS 5086-6:1992 which is withdrawn.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 p
3、articipation 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 obtained on request to its secretary. Cross-references The British Standards which implement international
4、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 BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all th
5、e 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 enquirers to understand the text; present to the responsible international/European committee any enquiries on th
6、e 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 document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages
7、1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference num
8、bers ISO 1740:2004(E) IDF 6:2004(E) OSI DI dnaF 4002 INTERNATIONAL STANDARD ISO 1740 IDF 6 Third edition 2004-12-01 Milkfat products and butter Determination of fat acidity (Reference method) Produits matire grasse laitire et beurre Dtermination de lacidit de la matire grasse (Mthode de rfrence) BS
9、ISO 1740:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) DPlcsid Fremia ihTs PDF file may ctnoian emdebt dedyfepcaes. In ccaocnadrw eith Aebods licensilop gnic,y this file mairp eb ynted iv roweb detu slah
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15、Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) I SO dna ID 4002 F All irhgts seredevr iii Contents Forewordiv 1 Scope1 2 Terms and definitions.1 3 Principle.1 4 Reagents1 5 Apparatus.2 6 Sampling3 7 Procedure.3 7.1 Preparation of test sample.3 7.2 Test
16、portion .3 7.3 Determination4 7.4 Blank test.4 7.5 Check test4 8 Expression of results4 9 Precision5 9.1 Interlaboratory test .5 9.2 Repeatability5 9.3 Reproducibility5 10 Test report6 Bibliography .7 BS ISO 1740:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Un
17、controlled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) iv I SO dna ID 4002 F All irhgts seredevr 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 ca
18、rried 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 the work
19、. 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 prepare Intern
20、ational 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 some of the
21、 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 1740IDF 6 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federati
22、on (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. This edition of ISO 1740IDF 6 cancels and replaces ISO 1740:1991, of which it constitutes a minor revision. Only editorial changes have been made. BS ISO 1740:2004 L
23、icensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) I SO dna ID 4002 F All irhgts seredevr v Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee
24、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 and AOAC International in the development of standard methods of analysis and sampling for milk and milk products. Draft Interna
25、tional 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 National Committees casting a vote. ISO 1740IDF 6 was prepared by Technical Committee ISO/TC 3
26、4, 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 and separately by AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Group of Experts,
27、 Free fatty acids (E39), under the aegis of its project leader, Mr A. Jellema (NL). This edition of ISO 1740IDF 6 cancels and replaces IDF 6B:1989. Only editorial changes have been made. BS ISO 1740:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Cop
28、y, (c) BSI blank 4002:0471 OSI SB Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI NITERNATNOIAL STANDARD IS:0471 O4002(E) ID:6 F4002(E) I SO dna ID 4002 F All irhgts seredevr 1 Milkfat products and butter Determination of fat acidity (Refere
29、nce method) 1 Scope This International Standard specifies a method for the determination of the acidity of the fat contained in milkfat products1) and in butter. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 fat acidity of a milkfat product
30、 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 per 100 g of fat. NOTE 2 The following alter
31、native 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 number of grams of oleic acid per 100 g of fat
32、 (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. The filtrate is dissolved in a mixture of pro
33、pan-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 water or water of equivalent purity. 1) As defin
34、ed in FAO/WHO Standard A-2, Section A for anhydrous milkfat and anhydrous butter oil, and Section B for ghee. BS ISO 1740:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) 2 I SO 4002 All irthgs ersedevr 4.1
35、 Tetra-n-butylammonium hydroxide standard solution, c(C16H37NO) = 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 a
36、ctual concentration of the solution should be determined to four decimal places immediately before use by titration against a standard solution of potassium hydrogen phthalate (KHC8H4O4) using thymol blue as indicator. However, if the burette is fitted with a facility to exclude the entry of carbon
37、dioxide, the concentration of the tetra-n-butylammonium 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
38、blue solution, (C27H30O5S) = 0,1 g/l, in propan-2-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
39、 (4.2) with four volumes of light petroleum (boiling 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 fai
40、nt greenish colour is obtained. 4.4 Reference fat (for checking periodically the whole titration procedure). 4.4.1 Preparation of reference fat samples Dissolve known quantities of palmitic acid (C16H32O2) in washed milkfat (see 4.4.2). Suitable concentrations of palmitic acid are 0,5 mmol to 2,0 mm
41、ol of palmitic acid per 100 g of fat. Calculate 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 milkfat2) with aqueous potassium hydroxid
42、e solution c(KOH) = 0,1 mol/l. Then wash with 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
43、 is necessary to keep the fat for a longer period, 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. BS ISO 1740:2004 Licensed Copy: sheffieldun sheff
44、ieldun, na, Mon Nov 27 03:46:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:0471 O4002(E) ID:6 F4002(E) I SO 4002 All irthgs ersedevr 3 5.1 Analytical balance, 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
45、rotor, for example a so-called Gerber centrifuge (see ISO 24462). 5.3 Centrifuge tubes. 5.4 Glass funnels and filter paper (medium grade). 5.5 Delivery pipettes 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 con
46、ical 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, electrically heated, capable of being maintained at 50 C 2 C. 6 Sampling A representative sample should have been sent to the laboratory. It shou
47、ld not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 7071. 7 Procedure 7.1 Preparation of test sample 7.1.1 Butter Set the oven (5.10) at 50 C. Melt an appropriate q
48、uantity 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 centrifuge (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
49、 visibly free from water and non-fatty compounds. 7.1.2 Milkfat products (anhydrous milkfat, anhydrous butter oil or anhydrous butterfat, butter oil, butterfat 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), transfer