BS 684-1.3:1991 pdf free download.Methods of analysis of fats and fatty oils Part 1: Physical methods — Section 1.3: Determination of melting point (slip point).
1 Scope
BS 684-1.3 specifies two mathods for the determinatbon of the melting point in open capillary tubes, commonly known as the slip point, of animal and vegetable fats and oils (referred toes fats hereinafter).
— Method A is only applicable to animal and vegetable fats which are solid at ambient temperature and which do not ethibit pronounced polymorphism.
— Method B is applicable to all animal and vegetable fats which art’ solid at ambient temperature, and is the method to be used for fats whose polymorphic behaviour is unknown,
A method for determination of the melting point of palm oil samples is given In Annex A.
NOTE) If applied ta fits with pramnasred palymarphi.in method A wifl gre. different and Ira. a.tid*rtovy results than nwthod B.
NOTE 2 Fat., which eshihit ponouncsd polymni’ptaun are principally enaa huttar and fat. congainlig appreciable quantities
of 2.unaatur.tgd, 1,I..aIur.tad tnacylglycseeL
2 Normative references
The following stendards contain provisions which, through reference in this text, constitute provisions of BS 684-1.3. At the timeof publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements baed on BS 684-1.3 are encouraged to investigate the possibility o(applying the most recent editions of thc standards indicated below, Members of LEC and ISO maintain registers of currently valid International Standards..
1S0661:1969, Animol and cegrtablr fats and oils — Pivparution of test sample. ISO MM1 991. Animal and tcgetahk fats and oil* — Sampling.
3 Definition
For the purposes of this International Standard, the following definition applies.
3.1
melting point (In open capillary tubes) slip point
the temperature at which a column of fan in an open capiliarv tube commences to rise under the conditions specified in this International Standard
4 Principle
Immersion of a capillary tube, containing a column of the fat which has been crystallized under controlled conditions, to a specified depth in water, the temperature of which is increased at a specified rate. Recording of the temperature at which the column its observed to start rising in the capillary tube.
5 Apparatus
Usual laboratory apparatus and, in particular, the following.
51 Capillary tubes, having uniform walls and which are open at both ends, of internal diameter 1.0 mm to 1,2 mm, external diameter 1,3 mm to 1,6 mm, wall thickness 0.15mm to 0,20mm and length 54) mm to 64) mm.
Check the internal and external diameters of the capillary cubes using a teat gauge such as that shown in Figure 1.
Before use, clean the tubes thoroughly by washing them successively with a mixture of chromic acid, water and acetone, and then dry them in an oven. It is recommended that new tubes be used.
52 Thermometer, graduated in divisions of 0.1 °C. calibrated over the range of melting points expected.
5.3 Stirrer, electrical.
5.4 Cooling bath, filled with brine or other non’freezing liquid, thermostatically maintained at a temperature of—iD °C to —12 °C. or filled with a mixture of flaked ice and salt (in the proportions 2 to 1 by mass) at a temperature of—ID °C to —12 °C.
5.5 Heating apparatus. consisting of the following elements:
a) water jacket, made of glass, provided with inlet and outlet tubes, and having the shape and dimensions shown in Figure 2:
b) water heater, capable of delivering a slow stream of water, the temperature of which can be controlled to increase at a rate of between 0.5 °C/min and 4 °Clmin. through the water jacket [a)1.
An example of a suitable heating apparatus is shown in Figure 3.
NOTE 3 Other types of heating apparatus, such aa a watcr.bath with magnetic stirrer, capable of being controlled to produce the
specified temperaturo rise may also be used.
6 Sampling
Sampling shall have been carried out in accordance with ISO 5555.
7 Preparation of the test sample
Prepare the test sample in accordance with ISO 661.
8 Procedure
8.1 Preparation of the capillary tubes for method A
Melt a portion of the test sample as rapidly as possible 1.0 at least 5 °C, but not more than 10°C, above the temperature at which it is completely melted.
Dip two capillary tubes (5.1) into the melted test sample until columns of fat 10 mm ± 2 mm long are obtained. Immediately after filling the tubes wipe them quickly with absorbent tissue to remove any fat adhering to the outer surfaces of the tubes. Immediately place the filled capillary tubes for a few seconds against a beaker filled with ice so that the fat solidifies.
Place the tubes in the cooling bath (5.4) for 5 mm. Continue in accordance with 8.3.
8.2 Preparation of the capillary tubes for method B
Melt a portion of the test sample as rapidly as possible to at least 5°C, but not more than 10°C, above the temperature at which it is completely melted.
Cool the melted test sample, with occasional stirring, until its temperature is 32 °C to 34 °C and then stir continuously with the stirrer (5.3). allowing the fat to cool until the first signs of cloudiness appear. Continue stirring by hand until the fat has a pasty consistency and then transfer the fat to a 100 ml beaker
8.4 Number of determinations
Carry out two determinations on the same test sample [i.e. to obtain two mean readings for
method A (8.3.5) and two final mean readings for method B (8.3.6)].
9 Expression of results
Take as the result the arithmetic mean of the two determinations.
Express the result to the nearest 0,1 DC.
10 Precision
10.1 Statistical results of inter-laboratory tests
Two inter.laboratory tests, carried out at the international level in 1982 and 1986 by ISOITC 34/SC 11, in which 20 laboratories [each of which carried out three determinations on each sample (columns 2, 3 and 8)] and 15 laboratories leach of which carried out three determinations on each sample (columns 4 to 7)] participated. gave the statistical results (evaluated in accordance with ISO 5725’>) shown in Table 1.
The results of interlaboratory tests on palm oil samples are given in Annex B.
10.2 Repeatability
The difference between the values of two determinations, carried out in rapid succession (or simultaneously) by the same operator using the same apparatus on the same test sample, shall not exceed 0,5 °C for method A and 1.0 °C for method B.
11 Test report
The test report shall specify the method used (i.e. Iso 6321, method A or method B) and the result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the result.
The test report shall include all information necessary for the complete identification of the sample.