《BS-684-1.13-1976.pdf》由会员分享,可在线阅读,更多相关《BS-684-1.13-1976.pdf(10页珍藏版)》请在三一文库上搜索。
1、BRITISH STANDARD CONFIRMED APRIL 1993 BS 684-1.13: 1976 Methods of analysis of Fats and fatty oils Part 1: Physical methods Section 1.13: Determination of cooling curve IMPORTANT NOTE. It is essential that this Section be read in conjunction with the information in the “General introduction” to BS 6
2、84, which is published separately. UDC 665.1.014:543:536.332 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 This British Standard having been prepared under the direction of the Oils and FAts Standards Committee, was publis
3、hed under the authority of the Executive Board on 29 October 1976 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference OFC/24 Draft for comment 74/50395 DC ISBN 0 580 09495 2 A British Standard does not purport to include all the necessary provisions of a
4、 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 cover, an inside front cover, pages i and ii, pages 1 to 5 and a back co
5、ver. 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 Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:4
6、2 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 BSI 07-1999i Contents Page 0Scope1 1 Method 1. Preferred method for cocoa butter and similar fats1 1.1Field of application1 1.2Reference1 1.3Principle1 1.4Apparatus1 1.5Sampling and preparation of sample for analysis3 1.6Procedure3 1.7Exp
7、ression of results4 1.8Test report4 2Method 2. For use with samples of less than 80 g4 2.1Field of application4 2.2Reference4 2.3Principle4 2.4Apparatus4 2.5Sampling and preparation of sample for analysis5 2.6Procedure5 2.7Expression of results5 2.8Test report5 Figure 1 Cooling curve apparatus2 Figu
8、re 2 Cooling curve apparatus Method 23 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 BSI 07-19991 0 Scope
9、This Section describes two methods for the determination of the cooling curve of cocoa butter and similar fats. Method 1 describes a procedure requiring a sample of at least 80 g and is preferred. Method 2 requires a sample of only 15 g and describes a procedure that may be used when there is insuff
10、icient sample available for method 1. The results of these two procedures are not interchangeable. 1 Method 1. Preferred method for cocoa butter and similar fats 1.1 Field of application The method described is suitable for the determination of the cooling curve of cocoa butter and similar fats. Thi
11、s method is recommended for use when 80 g or more of the fat is available for the test. 1.2 Reference The following standards publication is referred to in this method: BS 593, Laboratory thermometers. 1.3 Principle The molten fat is cooled under controlled conditions, solid particles of the fat are
12、 introduced and the temperature at which crystallization occurs is noted. 1.4 Apparatus The apparatus illustrated in Figure 1 and consisting of the following items is required (see also BS 684: General introduction). 1.4.1 Test tube, borosilicate glass, of the following dimensions: 1.4.2 Thermometer
13、, complying with the requirements of BS 593 type F50C/100. 1.4.3 Stirrer, a ring stirrer, fashioned from a borosilicate glass rod, with the following dimensions: 1.4.4 Rubber stopper, of moulded rubber with a central hole to carry the thermometer and a hole accommodating a glass bearing through whic
14、h the stirrer operates smoothly without contacting the thermometer or the inside of the test tube. The stopper shall have the following dimensions: 1.4.5 Air jacket, a glass jar (weighted with lead shot) fitted with a bored and recessed cork to accommodate the glass test tube and with the following
15、dimensions: 1.4.6 Water bath, capable of being maintained at a temperature of 55 C to 60 C. 1.4.7 Water bath, comprising a 4 litre low form beaker of borosilicate glass of the following dimensions and capable of being maintained at a temperature of 16.5 C to 17.0 C. 1.4.8 Stopwatch Inside diameter O
16、utside diameter Length 38 mm 43 mm 0.25 mm 190 mm Diameter of glass rod Diameter of ring 5.25 mm 0.25 mm 25 mm (centre of ring to centre of rod, see Figure 1) Length of stirrer 350 mm 5 mm Top diameter Bottom diameter Length 43 mm 38 mm 38 mm Outside diameter Height 100 mm 228 mm Outside diameter of
17、 neck Inside diameter of neck Length of neck 57 mm 50 mm 50 mm Outside diameter Height 160 mm 230 mm Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 2 BSI 07-1999 Figure 1 Cooling curve apparatus Licensed Copy: sheffieldun s
18、heffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 BSI 07-19993 1.5 Sampling and preparation of sample for analysis Heat a minimum quantity of 80 g of the fat in a beaker to 60 C and maintain at this temperature for 5 min. See also BS 684: General introdu
19、ction. 1.6 Procedure 1.6.1 Test portion. Transfer 75 g of the liquid sample into the glass test tube which has been warmed to 45 C to 50 C. Insert the stopper carrying the thermometer and stirrer. It is essential that the thermometer is equidistant from the vertical sides of the tube and that the ce
20、ntre of the bulb is located 40 mm from the upper surface of the fat. 1.6.2 Stabilization of the test portion. Place the test tube with the contents for a minimum of 15 min in a water bath maintained at a temperature of 55 C to 60 C. During this time destroy any crystal nuclei which may be present. F
21、igure 2 Cooling curve apparatus Method 2 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 4 BSI 07-1999 1.6.3 Determination. Conduct the determination in a draught-free area with an air temperature of 19 C to 21 C, avoiding a
22、 high relative humidity. Place the air jacket in the water bath maintained at a temperature of 16.5 C to 17.0 C. Adjust the level of the water in the bath so that it is level with the midpoint of the shoulder of the air jacket. Leave for at least 30 min before proceeding with the test. 1.6.3.1 Remov
23、e the test tube from the stabilizing bath (see 1.6.2). Wet the stirrer bearing with the fat by raising the stirrer arm. Allow to cool in air to 40 C, while gently stirring continuously, just breaking the surface of the fat with the ring of the stirrer. Secure the test tube in the air jacket by means
24、 of the recessed cork (see Figure 2). 1.6.3.2 Allow the test portion to cool to 35 C without stirring. Start the stopwatch; at each 5 s, 20 s, 35 s and 50 s past the minute make one stirrer stroke (up and down). This should be firm in action, raising the stirrer ring 25 mm to 40 mm above the surface
25、 of the fat. (This ensures that crystals formed in the bearing are carried down to the bulk of the test portion to achieve positive “seeding”.) 1.6.3.3 When the temperature falls to 32 C (or immediately above or below) record the temperature at the start of each minute and continue to record the tem
26、perature at one minute intervals until the test is completed. 1.6.3.4 Record the temperature at which fat crystals first appear in the main bulk of the sample as the “point of first crystals” (Jenson supercooling limit). The temperature will continue to fall until the “minimum” point is reached afte
27、r which it will commence to rise. Continue stirring as describe described in 16.3.2, ensuring that the stirring stroke is sufficiently firm to ensure thorough mixing of the test portion. Discontinue the stirring when the temperature rise becomes less than 0.1 C per minute or when the solidifying fat
28、 becomes so stiff that a risk of breakage is incurred. A further small rise in temperature will occur. Continue recording until the temperature commences to fall or until five consecutive readings are constant. Record the highest temperature reached as the “maximum”, the “temperature rise” (maximum
29、minus minimum) and the “total time” (the number of minutes taken to reach the maximum after commencing to take temperature readings at 32 C). 1.7 Expression of results Plot the recorded temperatures against time with temperature on the ordinate and time on the abscissa so that 0.1 C N 1 min = 2 min.
30、 1.8 Test report See the general instructions and recommendations given in BS 684: General introduction and include the following information: a) the method used; b) graph of temperature against time; c) temperature at which stirring was discontinued; d) temperature at which the first crystals were
31、observed; e) minimum temperature; f) maximum temperature; g) temperature rise i.e. e) to f); h) time taken from 32 C to the maximum temperature. 2 Method 2. For use with samples of less than 80 g 2.1 Field of application The method described is suitable for the determination of the cooling curve of
32、cocoa butter and similar fats but should only be used when the sample is less than 80 g. 2.2 Reference See 1.2. 2.3 Principle See 1.3. 2.4 Apparatus The apparatus illustrated in Figure 2 and consisting of the following items is required (see also BS 684: General introduction). 2.4.1 Glass test tube,
33、 thin-walled, 150 mm long and 25 mm in diameter, fitted with a bung bored with holes to accommodate a thermometer, gripped firmly and a stirrer. The bung is required to be an easy sliding fit for the test tube. 2.4.2 Thermometer, complying with the requirements of BS 593, type F50C/100. 2.4.3 Stirre
34、r, of 4 mm diameter borosilicate glass rod with a loop of suitable diameter so that it is approximately midway between the thermometer bulb and the wall of the test tube when the apparatus is assembled. 2.4.4 Beaker, 1 litre, tall form (diameter approximately 85 mm), weighted with lead shot, and wit
35、h a felt plug to accommodate the test tube. 2.4.5 Water bath, capable of being maintained at 17 0.2 C. The bath should be a glass vessel, or a vessel with a glass window, to enable the contents of the test tube to be observed. 2.4.6 Stopwatch Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13
36、:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13:1976 BSI 07-19995 2.5 Sampling and preparation of sample for analysis See BS 684: General introduction. 2.6 Procedure 2.6.1 Preparation of flakes of well grained fat for seeding. Melt a portion of the sample in an oven at a temperature be
37、tween 55 C to 60 C. Filter at this temperature through a dry filter paper. Cool the filtered fat, with occasional stirring, until the temperature falls to within 32 C to 34 C and then stir continuously either by hand or mechanically until the fat has the consistency of a paste. Immediately transfer
38、the fat to a vessel previously kept at a temperature of 15 C to 22 C, and allow to stand at this temperature for not less than 24 h. Shave or scrape the fat with a cool sharp blade (e.g. scalpel or razor blade), taking care to avoid melting of the sample, to obtain fine flakes for seeding the bulk o
39、f the fat during the determination (see 2.5.3). 2.6.2 Test portion. Weigh, to the nearest 0.1 g, 15 g of the fat into the test tube and melt the test portion at 50 C. 2.6.3 Determination. Assemble the apparatus as shown in Figure 2 with the thermometer bulb positioned at the centre of the test porti
40、on. Place the apparatus in the water bath at 17 C so that the water surface is 20 mm below the top of the tall form beaker air bath and stir the test portion occasionally until the thermometer reading indicates a temperature of 35 C. From this stage note the temperature readings at 1 min intervals,
41、stirring the test portion by gentle strokes of the stirrer at intervals of 15 s, taking care not to break the surface of the fat with the stirrer loop. At 28 C, add 0.03 g to 0.04 g of the flakes of well grained fat (2.6.1). Stop stirring when the increase in temperature has just passed its maximum.
42、 For samples of cocoa butter, readings may be stopped conveniently when the temperature has remained constant for two consecutive minutes after the rise in temperature. For fats whose properties are not known, continue to take readings beyond the maximum point. Record the temperature at which the fi
43、rst definite sign of crystallization appears. NOTEShould the sample under examination have solidification properties differing widely from those of cocoa butter, some modification to the procedure may be required. In particular, if crystallization first occurs at a temperature above 28 C, the seed c
44、rystals should be added 2 C or 3 C above the crystallization temperature. The temperature at which regular stirring and reading are commenced may also need to be altered. 2.7 Expression of results Plot the recorded temperatures against time, with temperature on the ordinate and time on the abscissa
45、so that 0.1 C N 1 min = 2 mm. 2.8 Test report See the general instructions and recommendations given in BS 684: General introduction and include the following information: a) the method used; b) graph of temperature against time; c) temperature at which stirring was discontinued; d) temperature at w
46、hich the first crystals were observed; e) minimum temperature; f) maximum temperature; g) temperature rise i.e. e) to f); h) time taken from 32 C to the maximum temperature. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:15:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.13: 1976 B
47、SI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards
48、are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this
49、 British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel: 020 8996 9000. Fax: 020 8996 7400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001. In response to o
链接地址:https://www.31doc.com/p-3774724.html