BS ISO 8262-2-2006 Milk products and milk-based foods - Determination of fat content by the Weibull-Berntrop gravimetric method (reference method) - Edible ices and ice-mixes《乳制品和以.pdf

1、BRITISH STANDARD BS ISO 8262-2:2005 Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 2: Edible ices and ice-mixes ICS 67.100.01 BS ISO 8262-2:2005 This British Standard was published under the authority of the Standard

2、s Policy and Strategy Committee on 12 January 2006 BSI 12 January 2006 ISBN 0 580 47143 8 National foreword This British Standard reproduces verbatim ISO 8262-2:2005 and implements it as the UK national standard. It supersedes BS 7142-3:1989 which is withdrawn. The UK participation in its preparatio

3、n was entrusted to Technical Committee AW/5, Milk and milk products, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in th

4、is document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a co

5、ntract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals

6、 for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to vi, pages 1 to 9 and a back cover. The BSI copyright noti

7、ce displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference numbers ISO 8262-2:2005(E) IDF 124-2:2005(E)INTERNATIONAL STANDARD ISO 8262-2 IDF 124-2 Second edition 2005-09-15 Milk products and milk-based foods Determi

8、nation of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 2: Edible ices and ice-mixes 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

9、 et prparations pour glaces base de lait BS ISO 8262-2:2005 ii BS ISO 8262-2:2005 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 Preparation of test sample. 3 7.2 Test por

10、tion . 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 Notes on procedure 8 10.1 Blank tests to check the solvent and filter papers 8 10.2 B

11、lank test carried out simultaneously with the determination 8 11 Test report . 8 Bibliography . 9 BS ISO 8262-2:2005 iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International St

12、andards 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 organizations, governmental and non-governmental, in liaison with ISO, also

13、 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 in the ISO/IEC Directives, Part 2. The main task of technical committee

14、s 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 % of the member bodies casting a vote. Attention is drawn to the possib

15、ility 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 8262-2IDF 124-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the

16、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, of which it constitutes a minor revision. ISO 8262 IDF 124 consists of the following parts, under the general title Milk products and milk-ba

17、sed 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 v Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Commit

18、tee in every member country. Every National Committee has the right to be represented 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 ad

19、opted by the Action Teams and Standing Committees are circulated to the National Committees 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 d

20、ocument may be the subject of patent rights. IDF shall not be held responsible for identifying 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

21、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 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 rev

22、ision. 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 Part 3: Special cases BS ISO 8262-2:2

23、005vi Introduction This International 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

24、based on the Rse-Gottlieb (RG) 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

25、 based on the WB principle has 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 t

26、he generally high content of carbohydrates, 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, sin

27、ce the acid digest is filtered 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 m

28、ethod, 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. BS ISO 8262-2:20051 Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric m

29、ethod (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.e. those products containing high levels of stab

30、ilizer 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 the RG principle given in ISO 7328. 2 Terms and d

31、efinitions 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 Principle A test portion is digested by boiling with d

32、ilute 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 evaporation and the substances extracted are weighed. (This

33、 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 water, or water of at least equivalent purity. 4

34、.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. BS ISO 8262-2:20052 4.2 Extraction solvent, free from water: n-hexane or light petroleum having

35、 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 flask, prepared in the same way, to check the mass (see 10.1). The solvent shall leave no residue greater

36、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 filter paper, carry out a blank test as specified in 7.3, using a solvent satisfying the requirement of 4.2.

37、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 Blue litmus paper. 4.5 Diatomaceous earth (optional; see 7.5.3). 4.6 Pure lactose (optional; see 7.5.3). 4.

38、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 employed may be required to comply with legislation relating to the hazards in using such solvents. Usua

39、l 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 blender with a blender jar, of capacity 1 litre, fitted with a lid. 5.3 Extraction apparatus, continuou

40、s 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, and an efficient reflux condenser fitted with a drying tube or plug of cotton wool. 5.4 Extraction flasks

41、, 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 made of cellulose, single thickness, of internal diameter 22 mm and external length 80 mm, for use with

42、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. BS ISO 8262-2:20053 5.7 Heating apparatus, for the extraction apparatus. For example, use a water bath, sand bat

43、h or a thermostatically controlled hotplate. 5.8 Boiling aids, fat-free, such as glass beads or pieces of non-friable, non-porous 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

44、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, 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 so

45、lvent to be gently distilled from the flasks at a temperature not exceeding 100 C. 5.14 Drying oven, electrically heated, with ventilation 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.

46、 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 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 bee

47、n damaged or changed during transport or storage. Sampling is not part of the method specified in this part of ISO 8262 IDF 124. 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 sam

48、pling to the time of commencing the procedure. In the case of a sealed can, store it unopened at a temperature below 20 C. Laboratory samples 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 Preparat

49、ion 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 test samples from each layer in the following manner for separate analysis. BS ISO 8262-2:2005