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1、BRITISH STANDARD BS 684-1.12: 1990 ISO 8293:1990 Methods of analysis of Fats and fatty oils Part 1: Physical methods Section 1.12 Determination of dilatation IMPORTANT NOTE. It is essential that BS 684-0, which is published separately, be read in conjunction with this Section. Licensed Copy: sheffie
2、ldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 This British Standard, having been prepared under the direction of the Food and Agricultural Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect o
3、n 30 November 1990 BSI 10-1999 First published October 1976 Second edition February 1988 Third edition November 1990 The following BSI references relate to the work on this standard: Committee reference FAC/18 Draft for comment 88/54727 DC ISBN 0 580 19010 2 Committees responsible for this British S
4、tandard The preparation of this British Standard was entrusted by the Food and Agricultural Standards Policy Committee (FAC/-) to Technical Committee FAC/18, upon which the following bodies were represented: Association of Public Analysts British Food Manufacturing Industries Research Association Co
5、-operative Union Department of Trade and Industry (Laboratory of the Government Chemist) FOSFA International Institute of Biology International Association of Seed Crushers Margarine and Shortening Manufacturers Association Ministry of Agriculture, Fisheries and Food Overseas Development Natural Res
6、ources Institute Royal Society of Chemistry Seed Crushers 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:
7、 sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 BSI 10-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Definition1 4Principle1 5Reagent1 6Apparatus1 7Sampling3 8Preparation
8、of the test sample3 9Procedure3 10Expression of results4 11Repeatability5 12Test report5 Annex A (informative) Specimen dilatation report6 Figure 1 Dilatometer2 Table 1 Correction Wt as a function of temperature t4 Table 2 Values of Vt5 Publication(s) referred toInside back cover Licensed Copy: shef
9、fieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 ii BSI 10-1999 National foreword This Section of BS 684 has been prepared under the direction of the Food and Agricultural Standards Policy Committee. It is identical with ISO 8293:1990 “Animal a
10、nd vegetable fats and oils Determination of dilatation” published by the International Organization for Standardization (ISO), and in the preparation of which the United Kingdom played a full part. It is a revision of BS 684-1.12:1976 which is withdrawn and from which it differs in that the dilatati
11、on is expressed in millimetres per kilogram of fat and not in cubic millimetres per 25 g of fat. If differs also in that a separate procedure is not given for animal fats requiring extended stabilization. With reference to clause 2 and clause 7, the revised edition of ISO 5555 is expected to be publ
12、ished in 1991 and it is intended that it will be implemented in the United Kingdom as a revision of BS 627:1982 “Methods for sampling animal and vegetable fats and oils”. In the meantime, BS 627:1982, which is technically equivalent to ISO 5555:1983, should be used. A British Standard does not purpo
13、rt 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 International StandardCorresponding British Standard BS 6
14、84 Methods of analysis of fats and fatty oils ISO 661:1980Part 0:1982 General introduction (Appendix B identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see co
15、pyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 BSI 10-19991 1 Scope This International Standar
16、d specifies a method for the determination of the dilatation of fats. It is applicable to animal and vegetable fats and oils (referred to as fats hereinafter), except palm stearin, having a melting point above 0 C and not more than 60 C. The method is empirical and therefore any variation in the pre
17、scribed operational details will modify the results obtained. A special procedure is given for the stabilization of cocoa butter and other polymorphic fats. NOTE 1Fats which consist principally of 2-unsaturated 1,3-saturated triglycerides display a characteristic polymorphism and need to be stabiliz
18、ed in a particular way before the dilatations are measured. Nevertheless, for cocoa butter substitutes based on lauric acid derivatives, whether hydrogenated or not, the method for non-polymorphic fats (9.5.1) may be applied. It should then be stated in the test report whether the fat has been subje
19、cted to a pre-treatment (as in 9.5.2) or not. Fats very rich in glycerol 2-oleate, 1,3-distearate, such as shea fat fractions, kokum butter and the allanblackia group of fats, sometimes behave unsatisfactorily if occluded air is retained; it is then advisable to heat the dilatometer before filling i
20、t. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on t
21、his International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 661:1989, Animal and vegetable fats and oils Preparation of test s
22、ample. ISO 5555:, Animal and vegetable fats and oils Sampling1). 3 Definition For the purposes of this International Standard, the following definition applies. dilatation of a fat the isothermal expansion, due to a change in state from solid to liquid, of a fat which has been previously solidified
23、under precisely prescribed conditions the dilatation of a fat is expressed in millilitres per kilogram of fat (or microlitres per gram of fat) and represents the difference between the volume the fat would occupy at the temperature in question if it were completely liquid (supercooled) and the actua
24、l volume of the fat at this temperature. It affords an empirical indication of the solid fats content at this temperature NOTE 2Care should be taken to avoid confusion with the expression of dilatation in microlitres per 25 g of fat which is sometimes used. 4 Principle Measurement of the volume of a
25、 known mass of fat at 60 C and at various temperatures below 60 C. Calculation of the volume of the liquid supercooled fat at other temperatures as required from the volume at 60 C. 5 Reagent 5.1 Sealing liquid, consisting of distilled water boiled out under vacuum and coloured using a 10 g/l soluti
26、on of congo-red, methyl orange or potassium dichromate. 6 Apparatus Usual laboratory and, in particular, the following. 6.1 Round-bottomed flask, of 100 ml capacity. 6.2 Burette, graduated in divisions of 0,05 ml or less. 6.3 Dilatometer, (see Figure 1). The bulb of the dilatometer shall have a volu
27、me of (7 0,5) ml, and the graduated part of the capillary tube shall have a volume of 900 4l. The zero mark on the capillary tube shall be level with the top of the neck of the dilatometer bulb. The stopper shall be filled with a sufficient quantity of lead-shot (or other suitable material) to preve
28、nt the dilatometer from floating in the water-bath. The dilatometer shall be carefully cleaned before use. It shall have a regularity of the graduated scale within 2 4l and an accuracy of 0,25 %, calculated in accordance with 6.3.1 and 6.3.2 respectively. 1) To be published. (Revision of ISO 5555:19
29、83.) Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 2 BSI 10-1999 6.3.1 Regularity of the graduated scale Introduce through the bulb of the dilatometer (6.3) into the capillary tube approximately 250 4l of mercury. Place th
30、e dilatometer in a horizontal position on two wooden blocks and place a small mirror under the capillary tube to avoid errors in reading due to parallax. When the dilatometer and mercury have attained room temperature, read the volume of mercury in scale units. Slightly displace the mercury column a
31、long the capillary tube and again read the volume of mercury in scale units. Repeat this procedure for various positions along the capillary. If the differences between the readings exceed 2 4l, or if they regularly increase or decrease, reject the tube. 6.3.2 Accuracy of the graduated scale Ensure
32、that the capillary tube is empty. Introduce about 750 4l of mercury into the capillary tube via the bulb. Place the dilatometer in a horizontal position on two wooden blocks alongside a thermometer, and position a small mirror under the capillary tube. Read the volume of the mercury and note the tem
33、perature. Slightly displace the mercury column along the capillary and again read the volume and note the temperature. Repeat this process several times. Pour the mercury from the 900 4l graduated end of the capillary tube into a tared flask and weigh. Calculate the volume of mercury from its mass a
34、nd apparent density at the measuring temperature. Deduct 1 4l from the observed volume as a correction for the meniscus reading, and compare the corrected observed volume with the true volume. Reject dilatometers showing differences of 0,5 % or more. 6.4 Water-baths 6.4.1 Each water-bath shall be fi
35、tted with a) a thermostat, capable of maintaining the water at any selected temperature between 10 C and 60 C to within 0,1 C, b) a vigorous stirrer, and c) a thermometer (see 6.6). 6.4.2 Depending on whether one or two water-baths are used for the determination, the heating capacity of the water-ba
36、ths shall be sufficient to increase the temperature of the water a) at a rate of at least 1 C/min, if one water-bath is used; b) by 10 C within a maximum of 30 min, in the case of two water-baths. 6.4.3 The water-baths shall be capable of producing a constancy of temperature of approximately 0,05 C
37、throughout the water-bath. NOTE 3The efficiency of stirring and possible deviation of the temperature of the water in the immediate neighbourhood of the dilatometer can be checked by inserting a dilatometer filled with hard fat (e.g. hardened palm oil, melting point 42 C to 48 C) and fitted with a t
38、hermometer. The reading of this thermometer should not deviate more than 0,05 C from that of the other thermometer in the water-bath. 6.4.4 The water-baths shall be equipped with an arrangement for suspending the dilatometers in the water and which allows individual vertical adjustment and easy tran
39、sfer from one water-bath to another. Figure 1 Dilatometer Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.12:1990 BSI 10-19993 6.5 Bath at 0 C If crushed ice is used for the bath at 0 C, the vessel shall have drain holes, otherwise
40、water at a temperature above 0 C will collect at the bottom of the vessel. The ice shall be stirred and repacked frequently, especially if several dilatometers are being cooled from 60 C to 0 C in the same bath. A cooling unit that can be maintained at 0 C is recommended, but this will need to be fi
41、lled with a liquid having a freezing point below 0 C. 6.6 Thermometers, graduated in divisions of 0,05 C, covering the required range of temperatures and calibrated against an official standard thermometer. 6.7 Water-bath, containing boiling water. 6.8 Boiling aids 7 Sampling Sampling shall have bee
42、n carried out in accordance with ISO 5555. 8 Preparation of the test sample Prepare the test sample in accordance with ISO 661. 9 Procedure 9.1 Types of procedure There are three types of procedure as follows: a) normal short range: measurements are made at temperatures of 20 C, 25 C, 30 C and 35 C,
43、 and at 5 C intervals thereafter up to 60 C if required; b) normal long range: measurements are made at temperatures of 0 C, 10 C, 15 C, 20 C and 25 C, and at 5 C intervals thereafter up to 60 C if required; c) rapid method for factory control: measurements are made at temperatures of 20 C and 30 C,
44、 and at any higher temperature if required. 9.2 Test portion Transfer 15 ml to 20 ml of the test sample (clause 8) into a 100 ml round-bottomed flask (6.1), add some boiling aids (6.8), heat to 80 C to 100 C in a boiling water-bath (6.7) and evacuate in a sufficient vacuum, shaking vigorously at int
45、ervals until air bubbles no longer escape from the boiling aids (this may take 10 min). Store the test portion under vacuum at 70 C until required (see 9.3). 9.3 Filling the dilatometer Care shall be taken not to heat the capillary tube by the hands or breath. By means of a burette (6.2) introduce 1
46、,5 ml of the sealing liquid (5.1) into the dilatometer (6.3). Weigh the dilatometer with the stopper to the nearest 10 mg. Fill the dilatometer bulb to half-way up the neck with the prepared test portion (9.2), if necessary after warming the dilatometer to prevent the fat from solidifying. Insert th
47、e stopper carefully to avoid trapping air bubbles and at the same time to drive the sealing liquid up the capillary tube. When the sealing liquid in the capillary tube rises to the 600 4l to 700 4l mark, close the capillary tube almost completely with the tip of the finger. Then place the stopper se
48、curely in position and remove the finger. Check that no air has been trapped under the stopper. Clean the outside of the bulb with solvent, dry and weigh the dilatometer again to determine the mass of the fat. 9.4 Volume of liquid fat Immerse the dilatometer to the zero mark in a water-bath (6.4) ma
49、intained at (60 0,1) C. Read the level of the sealing liquid in the capillary tube after not less than 30 min. NOTE 4A burette magnifier increases the precision with which the reading can be made. 9.5 Maturing 9.5.1 All fats Remove the dilatometer from the water-bath (6.4) and immerse it to the zero mark in the bath at 0 C (6.5) for 90 min. For non-polymorphic fats, for which the dilatation D0 is required at 0 C, record the level of the meniscus in the capillary tube and proceed to 9.6. For polymorphic fats,