BS EN ISO 1737:2000 pdf – Evaporated milk and sweetened condensed milk Ð Determination of fat content Ð Gravimetric method (Reference method).
1 Scope This International Standard specifies the reference method for the determination of the fat content of all types of evaporated milk and sweetened condensed milk (liquid sweetened and unsweetened concentrated milk). 2 Normative reference The following normative document contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, this publication do not apply. However, parties to agreement based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3889, Milk and milk products — Determination of fat content — Mojonnier-type fat extraction flasks . 3 Term and definition For the purposes of this International Standard the following term and definition apply. 3.1 fat content of evaporated milk and sweetened condensed milk mass fraction of substances determined by the procedure specified in this International Standard NOTE The fat content is expressed as a mass fraction, in percent [formerly given as % (m/m)]. 4 Principle An ammoniacal ethanolic solution of a test portion is extracted with diethyl ether and light petroleum. The solvents are removed by distillation or evaporation. The mass of the substances extracted is determined. NOTE This is usually known as the Röse-Gottlieb principle.
5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. The reagents shall leave no appreciable residue when the determination is carried out by the method specified (see 9.2.2). 5.1 Ammonia solution, containing a mass fraction of NH 3 of approximately 25 % ( ρ 20 = 91 0 g/l). NOTE If ammonia solution of this concentration is not available, a more concentrated solution of known concentration may be used (see 9.4.2). 5.2 Ethanol (C 2 H 5 OH), or ethanol denatured by methanol, containing a volume fraction of ethanol of at least 94 %. (See A.5.) 5.3 Congo red solution Dissolve 1 g of Congo red in water in a 1 00 ml one-mark volumetric flask (6.1 4). Dilute to the mark with water. NOTE The use of this solution, which allows the interface between the solvent and aqueous layers to be seen more clearly, is optional (see 9.4.3). Other aqueous colour solutions may be used provided that they do not affect the result of the determination. 5.4 Diethyl ether (C 2 H 5 OC 2 H 5 ), free from peroxides (see A.3), containing no more than 2 mg/kg of antioxidants, and complying with the requirements for the blank test (see 9.2.2, A.1 and A.4). NOTE The use of diethyl ether could lead to hazardous situations. Due to expected changes in safety regulations studies are ongoing to replace diethyl ether by another reagent provided that it does not affect the end result of the determination. 5.5 Light petroleum, with any boiling range between 30 °C and 60 °C or, as equivalent, pentane (CH 3 [CH 2 ] 3 CH 3 ) with a boiling point of 36 °C and complying with the requirements for the blank test (see 9.2.2, A.1 and A.4). NOTE The use of pentane is recommended because of its higher purity and constant quality. 5.6 Mixed solvent Shortly before use, mix equal volumes of diethyl ether (5.4) and light petroleum (5.5).
8.2 Sweetened condensed milk Open the sample container and mix thoroughly with a spoon or spatula. Use an up-and-down rotary movement in such a way that the top layers and the content of the lower corners of the container are moved and mixed. Take care to incorporate in the sample any milk adhering to the wall and ends of the container. Transfer the sample as completely as possible to a second sample container (provided with an airtight lid). Close the second container. If necessary, in the case of samples in sealed cans, condition the unopened can in the water bath (6.5) at a temperature of between 30 °C and 40 °C. Open the can, scrape out all milk adhering to the interior of the can, transfer to a dish large enough to permit stirring thoroughly and mix until the whole mass is homogeneous. In the case of a sample in a collapsible tube, open the tube and transfer the contents to a jar. Then cut open the tube and scrape out all material adhering to the interior and add to the contents of the jar. 9 Procedure NOTE An alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings (see note in 6.6) is given in annex B. 9.1 Test portion Mix the test sample (clause 8), by stirring in the case of sweetened condensed milk, or by gently inverting the bottle three or four times in the case of evaporated milk. Immediately weigh to the nearest 1 mg, directly or by difference, 4 g or 5 g of the test sample of evaporated milk, or 2,0 g to 2,5 g of the test sample of sweetened condensed milk in a fat-extraction flask (6.6). Transfer the test portion as completely as possible into the lower (small) bulb of the fat-extraction flask.