1、 Reference numbers ISO 8262-1:2005(E) IDF 124-1:2005(E) ISO and IDF 2005INTERNATIONAL STANDARD ISO 8262-1 IDF 124-1 Second edition 2005-09-15 Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 1: Infant foods Produits la
2、itiers et produits base de lait Dtermination de la teneur en matire grasse par la mthode gravimtrique Weibull-Berntrop (Mthode de rfrence) Partie 1: Aliments pour enfants en bas ge ISO 8262-1:2005(E) IDF 124-1:2005(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Ad
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8、witzerland ii ISO and IDF 2005 All rights reservedISO 8262-1:2005(E) IDF 124-1:2005(E) ISO and IDF 2005 All rights reserved iii Contents Page Foreword iv Introduction . vi 1 Scope. 1 2 Terms and definitions. 1 3 Principle. 1 4 Reagents and materials . 1 5 Apparatus 2 6 Sampling 3 7 Procedure 3 7.1 P
9、reparation of test sample. 3 7.2 Test portion . 4 7.3 Blank test. 4 7.4 Preparation of extraction flask 4 7.5 Determination 4 8 Calculation and expression of results 6 9 Precision 6 9.1 Interlaboratory test . 6 9.2 Repeatability 6 10 Notes on procedure 7 10.1 Blank tests to check the solvent and fil
10、ter papers 7 10.2 Blank test carried out simultaneously with the determination 7 11 Test report. 7 Bibliography . 8 ISO 8262-1:2005(E) IDF 124-1:2005(E) iv ISO and IDF 2005 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national stan
11、dards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International org
12、anizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given
13、 in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75
14、 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8262-1 IDF 124-1 was prepared by Technical Committee ISO/
15、TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This edition of ISO 8262-1 IDF 124-1 cancels and replaces ISO 8262-1:1987, of which it constitutes a minor revision. ISO 8262 IDF 124 consists
16、of the following parts, under the general title Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method): Part 1: Infant foods Part 2: Edible ices and ice-mixes Part 3: Special cases ISO 8262-1:2005(E) IDF 124-1:2005(E) ISO and IDF
17、 2005 All rights reserved v Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF
18、collaborates with ISO in the development of standard methods of analysis and sampling for milk and milk products. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires
19、approval by at least 50 % of the IDF National Committees casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 8262-1 IDF 124-1 was pre
20、pared by the International Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. All work was carried out by the Joint ISO/IDF/AOAC Group of Experts on Fat determination (E 31), under the aegi
21、s of its chairman, Mr J. Eisses (NL). This edition of ISO 8262-1 IDF 124-1 cancels and replaces IDF 124A:1988, of which it constitutes a minor revision. ISO 8262 IDF 124 consists of the following parts, under the general title Milk products and milk-based foods Determination of fat content by the We
22、ibull-Berntrop gravimetric method (Reference method): Part 1: Infant foods Part 2: Edible ices and ice-mixes Part 3: Special cases ISO 8262-1:2005(E) IDF 124-1:2005(E) vi ISO and IDF 2005 All rights reservedIntroduction This International Standard has been prepared within the framework of producing
23、a series of reference methods, which are harmonized to the greatest possible extent, for the gravimetric determination of the fat content of milk, milk products and milk-based foods. These methods are based on the Rse-Gottlieb (RG) method, or the Weibull-Berntrop (WB) method, or the Schmid-Bondzynsk
24、i-Ratzlaff (SBR) principle. For this part of ISO 8262 IDF 124, dealing with milk-based and other types of infant food containing more than 5 % (mass fraction) (dry matter) of starch or dextrin, or vegetable, fruit, meat, etc., a method based on the WB principle has been chosen for the following reas
25、ons: a) the RG procedure is not suitable owing to the high level of the above ingredients, which causes incomplete extraction of the fat and thus gives too low values for the fat content; b) the SBR procedure is not suitable owing to the generally high content of carbohydrates, which gives rise to e
26、ther-extractable compounds in the digestion with acid and thus gives too high values for the fat content; c) the WB procedure, although it also includes acid digestion, is not adversely affected by the ether- extractable compounds, since the acid digest is filtered and washed, and the dried residue
27、on the filter does not contain compounds that are extractable by light petroleum; d) the method described is already used for this purpose in many countries and is recommended by the Codex Committee on Methods of Analysis and Sampling. The original Weibull method was designed for bread; a considerab
28、ly modified method, as specified in this International Standard, was developed by Berntrop. This version has found wide application for the determination of fat in many types of food product. INTERNATIONAL STANDARD ISO 8262-1:2005(E) IDF 124-1:2005(E) ISO and IDF 2005 All rights reserved 1 Milk prod
29、ucts and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 1: Infant foods 1 Scope This part of ISO 8262 IDF 124 specifies the reference method for the determination of the fat content of infant foods to which the Rse-Gottlieb method is
30、not applicable i.e. those milk-based and other types of infant food that contain more than 5 % (mass fraction) (dry matter) of starch or dextrin, or vegetable, fruit, meat, etc. The method is also applicable if the product contains free fatty acids in significant quantities or if hard lumps that do
31、not dissolve completely in ammonia are present in the product. NOTE Other milk-based infant foods can be examined by the method utilizing the Rse-Gottlieb principle given in ISO 8381. Malto-dextrins without higher molecular dextrins, which are often present in infant foods, do not disturb the RG ext
32、raction even when present in high percentages. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 fat content all the substances determined by the method specified in this part of ISO 8262 IDF 124 NOTE It is expressed as a mass fraction in perce
33、nt. 3 Principle A test portion is digested by boiling with dilute hydrochloric acid. The hot digest is filtered through a wetted filter paper to retain fatty substances, then the fat is extracted from the dried filter paper using n-hexane or light petroleum. The solvent is removed by distillation or
34、 evaporation and the substances extracted are weighed. (This is usually known as the Weibull-Berntrop principle.) 4 Reagents and materials Use only reagents of recognized analytical grade that leave no appreciable residue when the determination is carried out by the method specified. Use distilled o
35、r deionized water, or water of at least equivalent purity. 4.1 Dilute hydrochloric acid, containing approximately 20 % (mass fraction) of HCl, 20approximately 1,10 g/ml. Dilute 100 ml of concentrated hydrochloric acid ( 20= 1,18 g/ml) with 100 ml of water and mix. ISO 8262-1:2005(E) IDF 124-1:2005(E
36、) 2 ISO and IDF 2005 All rights reserved4.2 Extraction solvent, free from water: n-hexane or light petroleum having any boiling range between 30 C and 60 C. To test the quality of the extraction solvent, distil 100 ml of it from an extraction flask (5.4) prepared as specified in 7.4. Use an empty ex
37、traction flask, prepared in the same way, to check the mass (see 10.1). The solvent shall leave no residue greater than 1,0 mg. Replace or distil the solvent if it does not meet this requirement. 4.3 Filter papers, of diameter 150 mm, pleated, medium grade, preferably defatted. To test the quality o
38、f the filter paper, carry out a blank test as specified in 7.3, using a solvent satisfying the requirement of 4.2. Use an empty extraction flask (5.4), prepared as specified in 7.4, to check the mass (see 10.1). The paper shall leave no residue greater than 2,5 mg. Replace unsatisfactory filter pape
39、rs. 4.4 Blue litmus paper. 4.5 Diatomaceous earth (optional; see 7.5.3). 4.6 Pure lactose (optional; see 7.5.3). 4.7 Cotton wool, defatted by extraction with the solvent (4.2) for 1,5 h and dried. 5 Apparatus WARNING Since the determination involves the use of volatile flammable solvents, electrical
40、 apparatus employed may be required to comply with legislation relating to the hazards in using such solvents. Usual laboratory equipment and, in particular, the following. 5.1 Analytical balance. 5.2 Blender, for homogenizing the laboratory sample, if necessary. For example, use a food chopper or a
41、 high-speed blender with a blender jar, of capacity 1 litre, fitted with a lid. 5.3 Extraction apparatus, continuous or semi-continuous. For example, use a Soxhlet type, consisting of an extraction flask (flat-bottomed, short-necked) of capacity 150 ml, an extractor with a siphoning volume of 40 ml
42、to 60 ml, and an efficient reflux condenser fitted with a drying tube or plug of cotton wool. 5.4 Extraction flasks, of capacity 150 ml, flat-bottomed and short-necked. 5.5 Extraction thimbles, made of defatted filter paper, glass, alumina or PTFE 1) , contributing no appreciable residue in the blan
43、k test, or made of cellulose, single thickness, of internal diameter 22 mm and external length 80 mm, for use with the extraction apparatus (5.3). 5.6 Water baths, capable of being maintained at the following temperatures: 40 C to 60 C (see 7.1.1); 30 C to 40 C (see 7.1.2). 1) Polytetrafluoroethylen
44、e. ISO 8262-1:2005(E) IDF 124-1:2005(E) ISO and IDF 2005 All rights reserved 3 5.7 Heating apparatus, for the extraction apparatus. For example, use a water bath, sand bath or a thermostatically controlled hotplate. 5.8 Boiling aids, fat-free, such as glass beads or pieces of non-friable, non-porous
45、 porcelain or silicon carbide. 5.9 Conical flask, of capacity 250 ml, fitted with a reflux condenser, preferably of the Liebig type. 5.10 Heating apparatus, for heating a conical flask fitted with a condenser. For example, use a wire gauze and gas burner, an electric hotplate or a sand bath. 5.11 Fi
46、lter funnel, suitable for use with the pleated filter paper (4.3). 5.12 Beakers with spouts, of capacities 100 ml and 250 ml. 5.13 Distillation apparatus, to enable the solvent to be gently distilled from the flasks at a temperature not exceeding 100 C. 5.14 Drying oven, electrically heated, with ve
47、ntilation port(s) fully open, capable of being maintained at a temperature of 102 C 2 C throughout the working space. The oven shall be fitted with a suitable thermometer. 5.15 Measuring cylinders, of capacities 50 ml, 100 ml and 250 ml. 5.16 Tongs, made of metal, suitable for holding flasks or beak
48、ers. 5.17 Tweezers, flat-tipped, for holding filter papers and thimbles. 6 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this part of ISO 8262 IDF 124.
49、A recommended sampling method is given in ISO 707 IDF 50. All liquid, viscous or pasty laboratory samples shall be kept at a temperature of 2 C to 4 C from the time of sampling to the time of commencing the procedure. In the case of a sealed can or bottle, store it unopened at a temperature below 20 C. 7 Procedure 7.1 Preparation of test sample 7.1.1 Liquid products Shake and invert the container. Open the container, pour the product slowly into a second container (provid
