BS EN ISO 8381:2000 pdf – Milk based infant foods Ð Determination offat content Ð Gravimetric method (Reference method).
1Scope This International Standard specifies the reference method for the determination of the fat content of milk-based infant foods. The method is applicable to liquid, concentrated and dried milk-based infant foods with no, or not more than a mass fraction of 5 % (dry matter) of starch or dextrin, or vegetable, fruit, meat, etc. NOTE 1 Malto-dextrins without higher molecular mass dextrins, which are often present in infant foods, do not disturb the Röse-Gottlieb extraction even when present in high concentrations. The method is not applicable to products which do not dissolve completely in ammonia owing to the presence of more than a few percent of starch or dextrin, or to the presence of hard lumps. The method is also not applicable to products which contains free fatty acids in significant quantities. The results obtained for these products will be too low. NOTE 2 For such products, recourse should be made to a method utilizing the Weibull-Berntrop principle (see ISO 8262-1 ). 2Normative reference The following normative document contains 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 agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative document 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. 3Term and definition For the purposes of this International Standard, the following term and definition apply. 3.1 fat content of milk mass fraction of substances determined by the procedure specified in this International Standard
4Principle 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. 5Reagents 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 % (H 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 9.4.4). 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).