1、BRITISH STANDARD BS 684-2.27: 1987 Methods of analysis of Fats and fatty oils Part 2: Other methods Section 2.27 Determination of bleachability IMPORTANT NOTE. It is essential that BS 684-0, which is published separately, be read in conjunction with this Section. UDC 665.1.014.099.72BS684-2.27:1987
2、This British Standard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority oftheBoardof BSI and comes into effect on 31 July 1987 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference FAC
3、/18 Draft for comment 86/54222 DC ISBN 0 580 16008 4 Foreword This Section of BS 684 has been prepared under the direction of the Food and Agriculture Standards Committee. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respon
4、sible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and2, an inside back cover and a back cover. This standard has been u
5、pdated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS684-2.27:1987 BSI 10-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Defini
6、tion 1 3 Principles 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Test sample 2 8 Procedure 2 9 Expression of results 2 10 Test report 2 Publications referred to Inside back coverii blankBS684-2.27:1987 BSI 10-1999 1 1 Scope This Section of BS 684 describes methods for the determination of the bleacha
7、bility of animal and vegetable fats and oils. The methods reflect industrial practice in the refining of fats. Method A is for technical tallow and animal grease. Method B is for crude palm oil. NOTE 1Method B may be suitable for other vegetable fats when a two-stage bleaching process is to be simul
8、ated. NOTE 2The titles of the publications referred to in this Section are given on the inside back cover. 2 Definition For the purposes of this Section of BS 684 the following definition applies. bleachability the colour of a sample of crude fat after it has been subjected to a specified procedure
9、intended to simulate the industrial bleaching process 3 Principles In method A the test portion is treated with bleaching earth under specified conditions and separated from the earth by filtration. In method B the test portion is treated with bleaching earth under specified conditions and separated
10、 from the earth by filtration followed by heating of the separated fat under vacuum. In both methods the colour of the bleached fat is measured using the method described in BS 684-1.14. 4 Reagents 4.1 Method A 4.1.1 Standard bleaching earth 1) , prepared by a recognized supplier for use with this m
11、ethod. A fresh supply shall be obtained at least annually and stored in small quantities of not more than100g in sealed packages. The loss in mass on drying at 105 C shall be determined immediately before use and if it exceeds 10 % (m/m), the package shall be discarded. The loss in mass on drying sh
12、all be determined by heating 5 0.1 g, weighed to the nearest 1 mg, of the earth in a weighed dish at105 2 C for 1 h, cooling and reweighing. 4.1.2 Inert gas, nitrogen (free from oxygen) or carbon dioxide. 4.2 Method B 4.2.1 Standard bleaching earth 1) , prepared by a recognized supplier for use with
13、 this method. A fresh supply shall be obtained at least annually and stored in small quantities of not more than100g in sealed packages. The loss in mass on drying at 105 C shall be determined (see4.1.1) immediately before use and if it exceeds 10 % (m/m), the package shall be discarded. 4.2.2 Inert
14、 gas, nitrogen (free from oxygen) or carbon dioxide. 4.2.3 Citric acid solution, 200 g/L. 5 Apparatus 5.1 Method A 5.1.1 Flat bottomed flask, capacity 250 mL, fitted with a gas inlet tube, a stirrer, a thermometer and an outlet tube. The stirrer shall rotate at 250 r/min to 350 r/min and shall not c
15、reate a vortex. Gas shall be able to escape from the flask and the stirrer shall be made of, or covered with, a suitable inert material, e.g.polytetrafluoroethylene (PTFE). 5.1.2 Electric hotplate or other heater, capable of maintaining the sample at110 2 C. 5.1.3 Filter funnel and fluted medium por
16、osity filter paper, large enough to hold the test portion (see8.1.4) and capable of being maintained at 50 C to60 C. 5.2 Method B 5.2.1 Round bottomed flask, capacity 250 mL, fitted with a gas inlet tube, a stirrer, a thermometer and an outlet tube. The stirrer shall rotate at 250 r/min to 350 r/min
17、 and shall not create a vortex. Gas shall be able to escape from the flask, and the stirrer shall be made of, or covered with, a suitable inert material, e.g.PTFE. 5.2.2 Electric hotplate or other heater, capable of maintaining the sample at 90 2 C, at 105 2 C and at260 5 C. 5.2.3 Hartley funnel and
18、 filter paper, with the funnel being70mm in diameter. 5.2.4 Recovery bends, air condenser and flask, for use with the vacuum pump. 5.2.5 Vacuum pump, capable of producing a pressure below400Pa(3mmHg). 6 Sampling The laboratory sample shall be taken in accordance with BS 627. 1) For information on th
19、e availability of the standard bleaching earth, apply to Enquiry Section, British Standards Institution, Linford Wood, Milton Keynes MK14 6LE, enclosing a stamped addressed envelope for reply.BS684-2.27:1987 2 BSI 10-1999 7 Test sample Prepare the test sample from the laboratory sample in accordance
20、 with BS 684-0. 8 Procedure 8.1 Method A. For technical tallow and animal grease 8.1.1 Weigh 100 0.5 g of the test sample (clause7) into the 250 mL flask (5.1.1), connect up the apparatus (5.1.1) and pass the inert gas (4.1.2) into the flask, over the surface of the fat but not into the fat. Heat th
21、e fat on the hotplate or other heater(5.1.2) to 110 2 C, with stirring. Allow the inert gas to escape through the outlet tube. 8.1.2 Add 5 0.1 g of the bleaching earth (4.1.1) to the fat. Ensure that the earth is evenly distributed in the fat and that there is no vortex. Raise the temperature to and
22、 maintain at 110 2 C for30min. 8.1.3 Remove from the source of heat and allow to stand for 10 1 min without stirring, but let the inert gas flow so that most of the earth settles. 8.1.4 Without delay, pour the supernatant liquid fat all at once into the filter paper in the funnel (5.1.3) maintaining
23、 the temperature at 50 C to 60 C. 8.1.5 Measure the colour of the filtrate in accordance with BS684-1.14. 8.2 Method B. For crude palm oil 8.2.1 Weigh 100 0.5 g of the test sample (clause7) into the 250 mL flask (5.2.1), connect up the apparatus (5.2.1) and pass the inert gas (4.2.2) into the flask,
24、 over the surface of the fat but not into the fat. Heat the fat on the hotplate or other heater(5.2.2) to 90 2 C, with stirring. Allow the inert gas to escape through the outlet tube. Add 0.5 0.05 mL of the citric acid solution (4.2.3) and maintain the temperature at 90 2 C for10min before proceedin
25、g to 8.2.2. 8.2.2 Add 2 0.1 g of the bleaching earth (4.2.1) to the fat. Ensure that the earth is evenly distributed in the fat and that there is no vortex. Raise the temperature to and maintain at 105 2 C for30min. 8.2.3 Allow to cool to 60 2 C without stirring but let the inert gas flow so that mo
26、st of the earth settles. 8.2.4 Filter the supernatant liquid fat using the preheated flask and funnel (5.2.3) through the filter paper without delay. 8.2.5 Transfer 90 1 g of the hot filtrate to a clean250 mL flask without a stirrer, add a few antibumping granules and connect the flask to the vacuum
27、 pump(5.2.5) via the recovery bends, air condenser and flask(5.2.4). Reduce the pressure to between130Pa and400Pa(1 mmHg to 3 mmHg) and raise the temperature of the fat to 260 5 C using the heater within 10 min. WARNING. Take the usual precautions in accordance with safe laboratory practice when wor
28、king with apparatus under vacuum. 8.2.6 Maintain the temperature at 260 5 C and the pressure at 130 Pa to 400 Pa for 20 min. 8.2.7 Remove the source of heat but maintain the vacuum and cool the flask with the fat to 60 2 C safely but quickly, for instance in a stream of cold air. 8.2.8 Release the v
29、acuum, without allowing any condensed fatty acids to contaminate the fat, and measure the colour of the fat in accordance with BS684-1.14. 8.3 The entire procedure in 8.2 shall be completed within2h30min. If not, repeat the procedure. 9 Expression of results The results shall be expressed in accorda
30、nce with BS684-1.14 giving the number of red, yellow and blue units needed to obtain the match and the path length of the cell used. 10 Test report The test report shall show the method used, that is method A or method B of BS 684-2.27 and the results obtained. It shall also mention any operating co
31、nditions not specified in this Section as well as any circumstances that may have influenced the results. The test report shall include all details required for complete identification of the sample.BS684-2.27:1987 BSI 10-1999 Publications referred to BS 627, Methods for sampling animal and vegetabl
32、e fats and oils. BS 684, Methods of analysis of fats and fatty oils. BS 684-0, General introduction. BS 684-1.14, Determination of colour. BS 684-2.27: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishS
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