BS-684-2.25-1997 ISO-6886-1996.pdf
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1、BRITISH STANDARD BS 684-2.25: 1997 ISO:6886:1996 Methods of analysis of Fats and fatty oils Part 2: Other methods Section 2.25 Determination of oxidative stability (accelerated oxidation test) IMPORTANT NOTICE: It is essential that BS 684-0.1 and BS 684-0.2 (BS EN ISO 661), which are published separ
2、ately, be read in conjunction with this Section. ICS 67.200.10 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-2.25:1997 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Boar
3、d, was published under the authority of the Standards Board and comes into effect on 15 March 1997 BSI 11-1998 First published August 1979 The following BSI references relate to the work on this standard: Committee reference AW/11 Draft for comment 89/54542 DC ISBN 0 580 26918 3 Committees responsib
4、le for this British Standard The preparation of this British Standard was entrusted to Technical Committee AW/11, Animal and vegetable fats and oils, upon which the following bodies were represented: Association of Public Analysts Department of Trade and Industry (Laboratory of the Government Chemis
5、t) Feed Fat Association FOSFA International International Federation of Inspection Agencies Lard Association Leatherhead Food Research Association Margarine and Shortening Manufacturers Association Ministry of Agriculture, Fisheries and Food National Edible Oil Distributors Association Seed Crushers
6、 and Oil Processors Association Soap and Detergent Industry Association Society of Chemical Industry Tropical Growers Association United Kingdom Renderers Association Ltd. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:47 GMT+00:
7、00 2006, Uncontrolled Copy, (c) BSI BS 684-2.25:1997 BSI 11-1998i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Definitions1 3Principle1 4Reagents and materials1 5Apparatus1 6Sampling2 7Preparation of test sample2 8Procedure2 9Calculation5 10Precision5 11Test re
8、port6 Annex A (informative) Summary of the method and examples of conductivity curves and the determination of induction time7 Annex B (informative) Bibliography9 Figure 1 Diagrammatic representation of the apparatus3 Figure 2 Diagrammatic representation of heating block, reaction vessel and measure
9、ment cell4 Figure A.1 Examples of conductivity curves8 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-2.25:1997 ii BSI 11-1998 National foreword This Section of BS 684 has been prepared by Technica
10、l Committee AW/11 and is identical with ISO 6886:1996 Animal and vegetable fats and oils Determination of oxidation stability (Accelerated oxidation test), published by the International Organization for Standardization (ISO) and in the preparation of which the United Kingdom played a full part. It
11、supersedes BS 684-2.25:1979 which was withdrawn in 1985, and from which it differs in that this edition has been technically updated. Additional information. ISO 5725:1986, to which informative reference is made in the text, has been superseded by ISO 5725-1:1994, ISO 5725-2:1994, ISO 5725-3:1994, I
12、SO 5725-4:1994 and ISO 5725-6:1994 which are identical with the following Parts of BS ISO 5725 Accuracy (trueness and precision) of measurement methods and results; BS ISO 5725-1:1994 General principles and definitions; BS ISO 5725-2:1994 Basic methods for the determination of repeatability and repr
13、odudibility of a standard measurement method; BS ISO 5725-3:1994 Intermediate measures of the precision of a standard measurement method; BS ISO 5725-4:1994 Basic methods for the determination of the trueness of a standard measurement method; and BS ISO 5725-6:1994 Use in practice of accuracy values
14、 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references Publication referred to
15、Corresponding British Standard Informative ISO 5555:1991BS EN ISO 5555:1995 Animal and vegetable fats and oils. Sampling (Identical) ISO 5725:1986BS 5497 Precision of test methods Part 1:1987 Guide for the determination of repeatability and reproducibility for a standard test method by inter-laborat
16、ory tests (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amend
17、ment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-2.25:1997 BSI 11-19981 1 Scope This International Standard specifies a method for the determination of the oxidation stability of fats and oils. It
18、is applicable to refined animal and vegetable fats and oils. NOTE 1The presence of volatile fatty acids and volatile acidic oxidation products makes accurate measurement impossible. 2 Definitions For the purposes of this International Standard, the following definitions apply. 2.1 induction period t
19、ime which passes between the moment when the sample reaches the desired temperature and the moment when the formation of oxidation products rapidly begins to increase 2.2 oxidation stability induction period determined according to the procedure specified in this International Standard. Oxidation st
20、ability is expressed in hours NOTE 2A temperature of 100 C is usually applied in the determination of oxidation stability. Depending on the oxidation stability of the sample under test, the determination may be carried out at a higher temperature, for example 110 C. The temperature should be chosen
21、so that an induction period of at least 5 h and at most 10 h is obtained. 3 Principle A stream of purified air is passed through the sample which has been brought to a specified temperature. The gases released during the oxidation process, together with the air, are passed into a flask containing wa
22、ter which has been demineralized or distilled and contains an electrode for measuring the conductivity. The electrode is connected to a measuring and recording device. It indicates the end of the induction period when the conductivity begins to increase rapidly. This accelerated increase is caused b
23、y the dissociation of volatile carboxylic acids produced during the oxidation process and absorbed in the water. 4 Reagents and materials Use only reagents of recognized analytical grade, and distilled or demineralized water. 4.1 Molecular sieve, with moisture indicator, 2 mbar, pore size 0,3 mm. Th
24、e molecular sieve should be dried in an oven set at 150 C and cooled down to room temperature in a siccative. 4.2 Potassium dichromate solution (optional), 20 g/l in 1 % sulfuric acid (V/V). 4.3 Petroleum ether, boiling range 40 C to 60 C, or acetone. 4.4 Cleaning agent, i.e. non-alkaline detergent
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