BS EN ISO 3657-2020 pdf free download.Animal and vegetable fats and oils – Determination of saponification value
This document specifies a method for the determination of the saponification value of animal and vegetable fats and oils. The saponification value is a measure of the free and esterified acids present in fats and fatty acids.
The method is applicable to refined and crude vegetable and animal fats.
If mineral acids are present, the results given by this method are not interpretable unless the mineral acids are determined separately.
The saponification value can also be calculated from fatty acid data obtained by gas chromatography analysis as given in Annex B. For this calculation, it is necessary to be sure that the sample does not contain major impurities or is thermally degraded.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 661, Animal and vegetable fats and oils — Preparation of test sample
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1 saponification value
Is number of milligrams of potassium hydroxide required for the saponification of 1 g of the product tested
4 Principle
The test sample is saponified by boiling under reflux with an excess of ethanolic potassium hydroxide,followed by titration of the excess potassium hydroxide with standard volumetric hydrochloric
acid solution.
5 Reagents
Use only reagents of recognized analytical grade, and distilled or demineralized water of equivalent purity.
5.1 Ethanol, volume fraction φ = 95 %.
The test samples are carefully mixed and filtered if visible impurities are present. If filtration is necessary, this shall be mentioned in the test report.
9 Procedure
9.1 Test portion
Weigh, to the nearest 5 mg, approximately 2 g of the test sample (see Clause 8) into a conical flask (6.1).
The test portion of 2 g has been determined on the basis of saponification values of 170 to 200. For other saponification values, the mass should be altered accordingly so that approximately half the ethanolic potassium hydroxide solution is neutralized. Recommendations for the mass of the test portion are given in Table 1.
9.2 Determination
9.2.1 Using a pipette (6.5), add to the test portion 25,0 ml of the ethanolic potassium hydroxide solution (5.2) and some boiling aids (5.6). Connect the reflux condenser (6.2) to the flask, place the flask on the heating device (6.3) and boil gently, shaking from time to time, for 60 min or for 2 h in the case of oils and fats having a high melting point and which are difficult to saponify.
9.2.2 Add to the hot solution 0,5 ml to 1 ml of the colour indicator solution (5.4 or 5.5) and titrate with the standard volumetric hydrochloric acid solution (5.3) until the colour of the indicator changes at the equivalence point. If the solution is strongly coloured, phenolphthalein (5.5) shall not be used as indicator.
9.3 Blank test
Carry out a blank test following the procedure specified in 9.2, using another 25,0 ml of the ethanolic potassium hydroxide solution (5.2) but omitting the test portion.
11 Precision
11.1 Results of interlaboratory test
An interlaboratory test carried out at the international level in 2000 by DIN (see Annex A), in which 22 laboratories participated, each of which carried out two determinations on each sample, gave the statistical results (evaluated in accordance with ISO 5725-1 and ISO 5725-2) shown in Table A.1.
11.2 Repeatability
The absolute difference between two independent single test results, obtained using the same method in identical test material in the same laboratory by the same operator using the same equipment within a short interval of time, will in not more than 5 % of cases be greater than the repeatability limit r given in Table A.1.
11.3 Reproducibility
The absolute difference between two single test results, obtained using the same method in identical test material in different laboratories with different operators using different equipment, will in not more than 5 % of cases be greater than the reproducibility limit R given in Table A.1.
12 Test report
The test report shall contain at least the following information:
a) all information necessary for the complete identification of the sample;
b) the sampling method used, if known;
c) whether filtration of the test sample(s) was necessary;
d) the test method used, with reference to this document, i.e. ISO 3657:2020;
e) a statement of which indicator has been used, 5.4 or 5.5;
f) all operating details not specified in this document, or regarded as optional, together with details of any incidents which may have influenced the test result(s);
g) the test result(s) obtained or, if the repeatability has been checked, the final result obtained.BS EN ISO 3657 pdf download.