BS 684-1 5-1987 Methods of analysis of fats and fatty oils - Physical methods - Determination of cloud point《脂肪和油脂的分析方法 物理法 浊点的测定》.pdf

1、BRITISH STANDARD CONFIRMED APRIL1993 BS684-1.5: 1987 Incorporating AmendmentNo.1 Methods of analysis of Fats and fatty oils Part1: Physical methods Section1.5 Determination of cloud point IMPORTANT NOTE. It is essential that BS 684-0, which is published separately, be read in conjunction with this S

2、ection. UDC 665.1.014:543:536.421.4.24.083BS684-1.5:1987 This British Standard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes intoeffecton 30October1987 BSI10-1999 First published October 1976 Firs

3、t 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 This Section of BS684 has been prepared under the direction of the Food and Agriculture Standards Committee. It supersedes BS

4、684-1.5:1976 which is withdrawn and from which it differs in that it does not refer to sperm oil, gives full details of methods1 and2 and includes a method3. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for thei

5、r 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 to4, an inside back cover and a back cover. This standard has been updated (see cop

6、yright 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 Comments 6051 June1989 Indicated by a sideline in the marginBS684-1.5:1987 BSI 10-1999 i Contents Page Foreword I

7、nside front cover 1 Scope 1 2 Sampling 1 3 Preparation of test sample 1 4 Method1. Cloud point more than 5 C below ambient temperature 1 5 Method2. Cloud point within 5 C of ambient temperature 3 6 Method3. Determination of cloud point of cooking oils on storage 3 7 Test report 4 Figure1Cloud point

8、apparatus (method1) 2 Figure2Cloud point apparatus (method2) 3 Publications referred to Inside back coverii blankBS684-1.5:1987 BSI 10-1999 1 1 Scope This Section describes three methods for the determination of the cloud point of fats which are liquid at ambient temperatures. Method 1 is applicable

9、 when the expected cloud point is more than5 C below ambient temperature. Method2 is applicable when the expected cloud point is within5 C of ambient temperature. Method3 is applicable when cloudiness occurs on storage. NOTEThe titles of the publications referred to in this Section are given on the

10、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 from the laboratory sample (seeclause2) in accordance with BS 684-0 ensuring that all moisture is removed and that the sample is bright and clear. 4 Meth

11、od 1. Cloud point more than5 C below ambient temperature 4.1 Definition For the purposes of method 1 the following definition applies. cloud point the temperature at which opacity is observed when the sample is cooled under the conditions described in method1 NOTEThe opacity is due to the formation

12、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 temperatures 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

13、glass, cylindrical in form with a flat bottom,30mm to33.5mm inside diameter and115mm to125mm in height. To indicate the height of the test portion the jar should be marked with a line543mm above the inside bottom. 4.3.2 Thermometers, covering a range from10 C to+50 C, capable of being read to within

14、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 metal, watertight, cylindrical in form with a flat bottom, about115mm in depth, with inside diameter9.5mm to12.5mm greater than the outside diameter of the test jar. 4.3.5

15、Disc, of cork or felt 6mm in thickness with the same diameter as the inside of the jacket (4.3.4). 4.3.6 Ring gasket, about 5mm 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

16、 enough to cling to the test jar and firm enough to hold its shape. NOTEThe purpose of the ring gasket is to prevent the test 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 maintain

17、ed by a cooling coil if available, otherwise by suitable freezing mixtures. NOTESuitable freezing mixtures are ice and water (fortemperatures down to+10 C) and crushed ice and sodium chloride (for temperatures down to10 C). 4.4 Procedure 4.4.1 Bring the test sample (seeclause3) to a temperature at l

18、east 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. 4.4.3 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 th

19、ermometer and the jar are coaxial, and the thermometer bulb is resting on the bottom of the jar. 4.4.4 Ensure that the 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,25mm fr

20、om the bottom, insert the test jar in the jacket. NOTENever place a jar directly into the cooling medium. 4.4.5 Maintain the temperature of the cooling bath(4.3.7) at1 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

21、disturbing the oil, inspect for cloudiness, and replace in the jacket. This complete operation shall take not 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 of10 C to5 C. D

22、o not transfer the jacket. Continue the procedure in 4.4.6BS684-1.5:1987 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 nearest0.5 C. NOTECloud

23、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 det

24、ermination 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. The

25、difference between the results of two determinations on the same test sample carried out by the same analyst in quick succession shall not exceed2 C, otherwise the procedure shall be repeated. Figure 1 Cloud point apparatus (method 1)BS684-1.5:1987 BSI 10-1999 3 4.6.2 Reproducibility. The difference

26、 between the results obtained by two analysts in different laboratories, on portions of the same sample are not expected to exceed4 C on more than one occasion in twenty. 5 Method 2. Cloud point within 5 C of ambient temperature 5.1 Definition For the purposes of method 2, the following definition a

27、pplies. cloud point the temperature at which cloudiness is observed when the sample is cooled under the conditions described in method2 NOTEThe cloudiness is due to the formation of crystals of fat and is the first indication that solidification is occurring. 5.2 Principle A test portion is cooled b

28、y 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 illustrated in Figure 2. 5.4.1 Thermometer, covering a range from0 C to50 C and capable of being read to within0.5 C. 5.4

29、.2 Test tube, 75mm long, 20mm in diameter. 5.4.3 Felt jacket, 50mm 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 sample (see clause3) at a temperature of10 C to15 C above the expected cloud point into the test tube (5.4.2) until this is t

30、wo-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 diethyl ether to evaporate so that the temperature of the fat drops at a rate of approximately 2 C/min, adding no further di

31、ethyl 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 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.

32、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 the same test sample. 5.6 Expression of results Express the result as the mean of the results of the two determinations. 6 Met

33、hod 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 cloudiness to develop when the sample is stored at a particular temperature Figure 2 Cloud point apparatus (method 2)BS684-1.5:1

34、987 4 BSI 10-1999 NOTEThe temperature of storage depends on the type 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.

35、6.3 Apparatus 6.3.1 Controlled temperature cabinet, maintained at the required temperature of 5 C, 10 C or 15 C. 6.3.2 Conical flask, 50mL, 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 por

36、tion (seeclause3) which has been heated to 70 C to ensure that 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 so

37、me circumstances the test is stopped when cloudiness does not 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 th

38、e method used and the result obtained, it shall also mention any 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 t

39、he sample.BS684-1.5:1987 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. BS684-0, General introduction. BS 684-1.5: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution B

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