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1、BRITISH STANDARD CONFIRMED APRIL 1993 BS 684-1.5: 1987 Incorporating Amendment No. 1 Methods of analysis of Fats and fatty oils Part 1: Physical methods Section 1.5 Determination of cloud point IMPORTANT NOTE. It is essential that BS 684-0, which is published separately, be read in conjunction with
2、this Section. UDC 665.1.014:543:536.421.4.24.083 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 This British Standard, having been prepared under the direction of the Food and Agriculture Standards Committee, was published u
3、nder the authority of the Board of BSI and comes into effect on 30 October 1987 BSI 10-1999 First published October 1976 First revision October 1987 The following BSI references relate to the work on this standard: Committee reference FAC/18 Draft for comment 86/50960 DC ISBN 0 580 16170 6 Foreword
4、This Section of BS 684 has been prepared under the direction of the Food and Agriculture Standards Committee. It supersedes BS 684-1.5:1976 which is withdrawn and from which it differs in that it does not refer to sperm oil, gives full details of methods 1 and 2 and includes a method 3. A British St
5、andard 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. Summary of pages This document comprises a front cove
6、r, an inside front cover, pages i and ii, pages 1 to 4, 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 amendment table on the inside front cover. Amendments issued since publication Am
7、d. No.Date of issueComments 6051June 1989Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 BSI 10-1999i Contents Page ForewordInside front cover 1Scope1 2Sampling1 3Preparation of test samp
8、le1 4Method 1. Cloud point more than 5 C below ambient temperature1 5Method 2. Cloud point within 5 C of ambient temperature3 6Method 3. Determination of cloud point of cooking oils on storage3 7Test report4 Figure 1 Cloud point apparatus (method 1)2 Figure 2 Cloud point apparatus (method 2)3 Public
9、ations referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 BSI 10-19991 1 Scope This
10、 Section describes three methods for the determination of the cloud point of fats which are liquid at ambient temperatures. Method 1 is applicable when the expected cloud point is more than 5 C below ambient temperature. Method 2 is applicable when the expected cloud point is within 5 C of ambient t
11、emperature. Method 3 is applicable when cloudiness occurs on storage. NOTEThe titles of the publications referred to in this Section are given on the inside back cover. 2 Sampling The laboratory sample shall be taken in accordance with BS 627. 3 Preparation of test sample Prepare the test sample fro
12、m the laboratory sample (see clause 2) in accordance with BS 684-0 ensuring that all moisture is removed and that the sample is bright and clear. 4 Method 1. Cloud point more than 5 C below ambient temperature 4.1 Definition For the purposes of method 1 the following definition applies. cloud point
13、the temperature at which opacity is observed when the sample is cooled under the conditions described in method 1 NOTEThe opacity is due to the formation of crystals of fat and is the first indication that solidification is occurring. 4.2 Principle A test portion is cooled by exposure to specified t
14、emperatures and inspected at intervals until cloudiness is observed. 4.3 Apparatus NOTEThe apparatus is illustrated in Figure 1. 4.3.1 Test jar, of clear glass, cylindrical in form with a flat bottom, 30 mm to 33.5 mm inside diameter and 115 mm to 125 mm in height. To indicate the height of the test
15、 portion the jar should be marked with a line 54 3 mm above the inside bottom. 4.3.2 Thermometers, covering a range from 10 C to + 50 C, capable of being read to within 0.5 C. 4.3.3 Cork, to fit the test jar (4.3.1), bored centrally to take the test thermometer (4.3.2). 4.3.4 Jacket, of glass or met
16、al, watertight, cylindrical in form with a flat bottom, about 115 mm in depth, with inside diameter 9.5 mm to 12.5 mm greater than the outside diameter of the test jar. 4.3.5 Disc, of cork or felt 6 mm in thickness with the same diameter as the inside of the jacket (4.3.4). 4.3.6 Ring gasket, about
17、5 mm in thickness, to fit snugly around the outside of the test jar and loosely inside the jacket. This gasket may be made of rubber, leather or other suitable material, elastic enough to cling to the test jar and firm enough to hold its shape. NOTEThe purpose of the ring gasket is to prevent the te
18、st jar from touching the jacket. 4.3.7 Bath or baths, maintained at specified temperatures with a firm support to hold the jacket vertical. The bath temperatures may be maintained by a cooling coil if available, otherwise by suitable freezing mixtures. NOTESuitable freezing mixtures are ice and wate
19、r (for temperatures down to + 10 C) and crushed ice and sodium chloride (for temperatures down to 10 C). 4.4 Procedure 4.4.1 Bring the test sample (see clause 3) to a temperature at least 15 C above the expected cloud point. 4.4.2 Pour a test portion into the test jar (4.3.1) to the marked height. 4
20、.4.3 Close the test jar tightly using the cork (4.3.3) carrying the test thermometer (4.3.2). Adjust the position of the cork and the thermometer so that the cork fits tightly, the thermometer and the jar are coaxial, and the thermometer bulb is resting on the bottom of the jar. 4.4.4 Ensure that th
21、e disc (4.3.5), ring gasket (4.3.6),and the inside of the jacket (4.3.4) are clean and dry. Place the disc in the bottom of the jacket. Place the ring gasket around the test jar, 25 mm from the bottom, insert the test jar in the jacket. NOTENever place a jar directly into the cooling medium. 4.4.5 M
22、aintain the temperature of the cooling bath (4.3.7) at 1 C to + 2 C. 4.4.6 At each test thermometer reading that is a multiple of 1 C, remove the test jar from the jacket quickly but without disturbing the oil, inspect for cloudiness, and replace in the jacket. This complete operation shall take not
23、 more than 3 s. 4.4.7 If the oil does not show cloudiness when it has been cooled to 10 C, transfer the test jar to another jacket in a second bath maintained at a temperature of 10 C to 5 C. Do not transfer the jacket. Continue the procedure in 4.4.6 Licensed Copy: sheffieldun sheffieldun, na, Wed
24、Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 2 BSI 10-1999 4.4.8 When the inspection (4.4.6) first reveals a distinct cloudiness or haze in the oil at the bottom of the test jar, record the reading of the test thermometer as the cloud point to the nearest 0.5 C. NOTEClo
25、ud or haze is noted first at the bottom of the test jar where the temperature is lowest. A slight haze throughout the entire sample, which slowly becomes more apparent as the temperature is lowered, is usually due to traces of water in the oil. Generally, this water haze will not interfere with the
26、determination of the cloud point. 4.4.9 Carry out two determinations on the same test sample. 4.5 Expression of results Express the result as the mean of the results of the two determinations provided that the requirements for repeatability (4.6.1) are satisfied. 4.6 Precision 4.6.1 Repeatability. T
27、he difference between the results of two determinations on the same test sample carried out by the same analyst in quick succession shall not exceed 2 C, otherwise the procedure shall be repeated. Figure 1 Cloud point apparatus (method 1) Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:
28、40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 BSI 10-19993 4.6.2 Reproducibility. The difference between the results obtained by two analysts in different laboratories, on portions of the same sample are not expected to exceed 4 C on more than one occasion in twenty. 5 Method 2. Clou
29、d point within 5 C of ambient temperature 5.1 Definition For the purposes of method 2, the following definition applies. cloud point the temperature at which cloudiness is observed when the sample is cooled under the conditions described in method 2 NOTEThe cloudiness is due to the formation of crys
30、tals of fat and is the first indication that solidification is occurring. 5.2 Principle A test portion is cooled by the evaporation of diethyl ether until cloudiness is observed. 5.3 Reagent 5.3.1 Diethyl ether WARNING. Diethyl ether is toxic and flammable. 5.4 Apparatus NOTEThe apparatus is illustr
31、ated in Figure 2. 5.4.1 Thermometer, covering a range from 0 C to 50 C and capable of being read to within 0.5 C. 5.4.2 Test tube, 75 mm long, 20 mm in diameter. 5.4.3 Felt jacket, 50 mm deep, to fit snugly round the test tube (5.4.2). 5.4.4 Small plane mirror 5.5 Procedure 5.5.1 Pour the test sampl
32、e (see clause 3) at a temperature of 10 C to 15 C above the expected cloud point into the test tube (5.4.2) until this is two-thirds full. 5.5.2 Fit the felt jacket (5.4.3) around the test tube so that the sample is completely enclosed. 5.5.3 Soak the jacket with diethyl ether (5.3.1) and allow the
33、diethyl ether to evaporate so that the temperature of the fat drops at a rate of approximately 2 C/min, adding no further diethyl ether when the temperature drops to within 5 C of the expected cloud point. Stir with the thermometer (5.4.1) during cooling. 5.5.4 Wipe the outside of the bottom of the
34、tube to prevent mistiness which might be confused with the clouding of the fat. 5.5.5 Look down the tube into the mirror (5.4.4) reflecting a light-coloured object and record the temperature to the nearest 0.5 C at which the liquid becomes cloudy in appearance. 5.5.6 Carry out two determinations on
35、the same test sample. 5.6 Expression of results Express the result as the mean of the results of the two determinations. 6 Method 3. Determination of cloud point of cooking oils on storage 6.1 Definition For the purposes of method 3 the following definition applies. cloud point the time taken for cl
36、oudiness to develop when the sample is stored at a particular temperature Figure 2 Cloud point apparatus (method 2) Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 4 BSI 10-1999 NOTEThe temperature of storage depends on the t
37、ype of fat and the reason for the test. The cloudiness is due to the start of complete solidification or the precipitation of a fraction. 6.2 Principle A test portion is stored at a particular temperature until cloudiness is observed. 6.3 Apparatus 6.3.1 Controlled temperature cabinet, maintained at
38、 the required temperature of 5 C, 10 C or 15 C. 6.3.2 Conical flask, 50 mL, with stopper. 6.4 Procedure 6.4.1 Set the cabinet (6.3.1) at the required temperature of 5 C, 10 C or 15 C. 6.4.2 Fill the conical flask (6.3.2) with a test portion (see clause 3) which has been heated to 70 C to ensure that
39、 it is completely liquid, stopper it and place in the cabinet. 6.4.3 Observe the test portion, preferably daily, and when cloudiness is observed record the number of days elapsed since the test portion was placed in the cabinet. NOTEIn some circumstances the test is stopped when cloudiness does not
40、occur after a certain period. 6.5 Expression of results Express the result as the number of days taken for cloudiness to develop or during which the sample remains clear at the temperature used. 7 Test report The test report shall show the method used and the result obtained, it shall also mention a
41、ny operating conditions not specified in this standard or regarded as optional, as well as any incidents that may have influenced the result. The test report shall include all the information necessary for the complete identification of the sample. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec
42、 06 13:36:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.5:1987 BSI 10-1999 Publications referred to BS 627, Methods for sampling animal and vegetable fats and oils. BS 684, Methods of analysis of fats and fatty oils. BS 684-0, General introduction. Licensed Copy: sheffieldun sheffieldun, na
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