1、 Reference numbers ISO 8262-2:2005(E) IDF 124-2:2005(E) ISO and IDF 2005INTERNATIONAL STANDARD ISO 8262-2 IDF 124-2 Second edition 2005-09-15 Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 2: Edible ices and ice-mixe
2、s Produits laitiers et produits base de lait Dtermination de la teneur en matire grasse par la mthode gravimtrique Weibull-Berntrop (Mthode de rfrence) Partie 2: Glaces de consommation et prparations pour glaces base de lait ISO 8262-2:2005(E) IDF 124-2:2005(E) PDF disclaimer This PDF file may conta
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8、w.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2005 All rights reservedISO 8262-2:2005(E) IDF 124-2:2005(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
9、 Apparatus 2 6 Sampling 3 7 Procedure 3 7.1 Preparation of test sample. 3 7.2 Test portion . 4 7.3 Blank test. 5 7.4 Preparation of extraction flask 5 7.5 Determination 5 8 Calculation and expression of results 6 9 Precision 6 9.1 Interlaboratory test . 6 9.2 Repeatability 7 9.3 Reproducibility 7 10
10、 Notes on procedure 8 10.1 Blank tests to check the solvent and filter papers 8 10.2 Blank test carried out simultaneously with the determination 8 11 Test report . 8 Bibliography . 9 ISO 8262-2:2005(E) IDF 124-2:2005(E) iv ISO and IDF 2005 All rights reservedForeword ISO (the International Organiza
11、tion for Standardization) is a worldwide federation of national standards 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
12、has the right to be represented on that committee. International organizations, 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. In
13、ternational Standards are drafted in accordance with the rules given 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. Publi
14、cation as an International Standard requires approval by at least 75 % 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 r
15、ights. ISO 8262-2 IDF 124-2 was prepared by Technical Committee ISO/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 8262-2 IDF 124-2 cancels and replaces ISO 8262-2:1987,
16、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 Weibull- Berntrop gravimetric method (Reference method): Part 1: Infant foods Part 2: Edible ices and ice-mixes P
17、art 3: Special cases ISO 8262-2:2005(E) IDF 124-2:2005(E) ISO and IDF 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
18、 on the IDF Standing Committees carrying out the technical work. IDF 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 Comm
19、ittees for voting. Publication as an International Standard requires 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 id
20、entifying any or all such patent rights. ISO 8262-2 IDF 124-2 was prepared 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/
21、IDF/AOAC Group of Experts on Fat determination (E 31), under the aegis of its chairman, Mr J. Eisses (NL). This edition of ISO 8262-2 IDF 124-2 cancels and replaces IDF 125A:1988, of which it constitutes a minor revision. ISO 8262 IDF 124 consists of the following parts, under the general title Milk
22、 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 8262-2:2005(E) IDF 124-2:2005(E) vi ISO and IDF 2005 All rights reservedIntroduction This Intern
23、ational Standard has been prepared within the framework of producing 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)
24、 method, or the Weibull-Berntrop (WB) method, or the Schmid-Bondzynski-Ratzlaff (SBR) principle. For this part of ISO 8262 IDF 124, dealing with milk-based and other types of edible ices and ice-mixes containing high levels of fruit, egg yolk, emulsifier, etc., a method based on the WB principle has
25、 been chosen for the following reasons: 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 c
26、arbohydrates, which gives rise to ether-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
27、 and washed, and the dried residue 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. The original Weibull method was designed for bread; a considerably modified method, as specified in this In
28、ternational 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 8262-2:2005(E) IDF 124-2:2005(E) ISO and IDF 2005 All rights reserved 1 Milk products and milk-based foods Determination of
29、fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 2: Edible ices and ice-mixes 1 Scope This part of ISO 8262 IDF 124 specifies the reference method for the determination of the fat content of edible ices and ice-mixes to which the Rse-Gottlieb method is not applicable (i
30、.e. those products containing high levels of stabilizer or thickening agent, or of egg yolk or of fruit, or of combinations of these constituents). NOTE Milk-based edible ices and ice-mixes containing no or not more than a few percent of the above ingredients can be examined by the method utilizing
31、the RG principle given in ISO 7328. 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 percent. 3 Princ
32、iple 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 evaporatio
33、n 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 or deionized
34、 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 8262-2:2005(E) IDF 124-2:2005(E) 2 ISO and
35、 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 extraction fl
36、ask, 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 of the filte
37、r 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 papers. 4.4 Blu
38、e 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 apparatus
39、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 high-speed
40、 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 to 60 ml, a
41、nd 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 blank test, or
42、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 7.1.2); 30 C to 40 C (see 7.1.3). 1) Polytetrafluoroethylene. ISO 8262
43、-2:2005(E) IDF 124-2:2005(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 porcelain
44、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 Filter funnel
45、, 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 ventilation p
46、ort(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 beakers. 5.17 T
47、weezers, 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. A recommend
48、ed 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, store it unopened at a temperature below 20 C. Laboratory sample
49、s of frozen ice shall be kept at a temperature of not more than 18 C from the time of sampling to the time of commencing the procedure. 7 Procedure 7.1 Preparation of test sample 7.1.1 Edible ices, frozen After removing any coating of a non-ice character, cut the laboratory sample into pieces. When it is required to determine the fat content of each layer of a multi-layer product, carefully separate the layers, if possible while they are still frozen. Prepare individual t
