ISO 8262-3-2005 Milk products and milk-based foods - Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) - Part 3 Special.pdf

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1、 Reference numbers ISO 8262-3:2005(E) IDF 124-3:2005(E) ISO and IDF 2005INTERNATIONAL STANDARD ISO 8262-3 IDF 124-3 Second edition 2005-11-01 Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 3: Special cases Produits l

2、aitiers et produits base de lait Dtermination de la teneur en matire grasse par la mthode gravimtrique Weibull-Berntrop (Mthode de rfrence) Partie 3: Cas particuliers ISO 8262-3:2005(E) IDF 124-3:2005(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing

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5、very care has been taken to ensure that the file is suitable for use by ISO member bodies and IDF national committees. In the unlikely event that a problem relating to it is found, please inform the ISO Central Secretariat at the address given below. ISO and IDF 2005 All rights reserved. Unless othe

6、rwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respective address below. ISO copyright office International Dairy Feder

7、ation Case postale 56 CH-1211 Geneva 20 Diamant Building Boulevard Auguste Reyers 80 B-1030 Brussels Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii

8、ISO and IDF 2005 All rights reservedISO 8262-3:2005(E) IDF 124-3:2005(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 . 2 5 Apparatus 2 6 Sampling 3 7 Procedure 3 7.1 Preparation of

9、 test sample. 3 7.2 Test portion . 4 7.3 Blank test. 4 7.4 Preparation of extraction flask 4 7.5 Determination 5 8 Calculation and expression of results 6 9 Precision 6 9.1 Interlaboratory test . 6 9.2 Repeatability 6 9.3 Reproducibility 7 10 Notes on procedure 7 10.1 Blank tests to check the solven

10、t and filter papers 7 10.2 Blank test carried out simultaneously with the determination 8 11 Test report . 8 Bibliography . 9 ISO 8262-3:2005(E) IDF 124-3:2005(E) iv ISO and IDF 2005 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of nat

11、ional 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 has the right to be represented on that committee. Interna

12、tional organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electro technical Commission (IEC) on all matters of electro technical standardization. International Standards are drafted in accordance with the

13、 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. Publication as an International Standard requires approval by

14、 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 rights. ISO 8262-3 IDF 124-3 was prepared by Technical Co

15、mmittee 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 8262-3 IDF 124-3 cancels and replaces ISO 8262-3:1987, of which it constitutes a minor revision. ISO 8262 IDF 1

16、24 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 ISO 8262-3:2005(E) IDF 124-3:2005(E)

17、 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 on the IDF Standing Committees carrying out the technica

18、l 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 Committees for voting. Publication as an International Standa

19、rd 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 identifying any or all such patent rights. ISO 8262-3 IDF 1

20、24-3 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 IDF and ISO. All work was carried out by the Joint ISO-IDF Group of Experts on Fat determination (E 31), under

21、the aegis of its chairman, Mr J. Eisses (NL). This edition of ISO 8262-3 IDF 124-3 cancels and replaces IDF 126A: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 b

22、y the Weibull-Berntrop gravimetric method (Reference method): Part 1: Infant foods Part 2: Edible ices and ice-mixes Part 3: Special cases ISO 8262-3:2005(E) IDF 124-3:2005(E) vi ISO and IDF 2005 All rights reservedIntroduction ISO 8262 IDF 124 has been prepared within the framework of producing a s

23、eries 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-Gottlied (RG) method, or the Weibull-Berntrop (WB) method, or the Schmid-Bondzynski-R

24、atzlaff (SBR) principle. For this part of ISO 8262 IDF 124, dealing with milk-based and with liquid, concentrated or dried milk products in poor condition and/or containing insoluble non-milk ingredients, a method based on the WB principle has been chosen for the following reasons: a) the RG procedu

25、re is not suitable when a distinct quantity of free fatty acids is present, or when the product contains lumps and/or non-milk ingredients insoluble in ammonia, since the extraction of fat is incomplete; b) the SBR procedure is not suitable owing to a considerable lactose content, which gives rise t

26、o some 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 and washed, and the dried

27、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 International Standard, was d

28、eveloped by Berntrop. This version has found wide application for the determination of fat in many types of food product. INTERNATIONAL STANDARD ISO 8262-3:2005(E) IDF 124-3:2005(E) ISO and IDF 2005 All rights reserved 1 Milk products and milk-based foods Determination of fat content by the Weibull-

29、Berntrop gravimetric method (Reference method) Part 3: Special cases 1 Scope This part of ISO 8262 IDF 124 specifies the reference method for the determination of the fat content of milk- based and of liquid, concentrated or dried milk products to which the Rse-Gottllieb method is not applicable; i.

30、e. those containing distinct quantities of free fatty acids or those which are not completely soluble in ammonia owing to the presence of lumps or non-milk ingredients, such as custards, porridges or certain milk- based products for bakery purposes. NOTE 1 Reference Rse-Gottlieb methods for the dete

31、rmination of the fat content of milk, of cream, of evaporated and sweetened condensed milk, and of dried milk products are specified in ISO 1211, ISO 2450, ISO 1737 and ISO 1736 respectively. The method is also applicable to fresh cheese types, such as cottage cheese and quarg, as well as to fresh c

32、heeses with added fruit, syrup, “muesli”, etc. for which the SBR method is not suitable owing to the higher carbohydrate contents and/or extreme inhomogeneity. NOTE 2 A reference Schmid-Bondzynski-Ratzlaff method for the determination of the fat content of cheese and processed cheese products having

33、 lactose contents below 5 % (mass fraction) of the non-fat solids is specified in ISO 1735. 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 NOT

34、E It is expressed as a mass fraction in percent. 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 petrole

35、um. The solvent is removed by distillation or evaporation and the substances are extracted and weighed. (This is usually known as the Weibull-Berntrop principle.) ISO 8262-3:2005(E) IDF 124-3:2005(E) 2 ISO and IDF 2005 All rights reserved4 Reagents and materials Use only reagents of recognized analy

36、tical 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. 4.1 Dilute hydrochloric acid, containing approximately 20 % (mass fraction) of HCl, 20approximately 1,10 g/ml. Dilute

37、 100 ml of concentrated hydrochloric acid ( 20= 1,18 g/ml) with 100 ml of water and mix. 4.2 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

38、.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 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

39、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. 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 greate

40、r 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). 4.7 Cotton wool, defatted by extraction with the solvent (4.2) for 1,5 h and dried. 5 Apparatus WARNING Since the determination involves t

41、he use of volatile flammable solvents, electrical 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, i

42、f 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, continuous or semi-continuous. For example, use a Soxhlet type, consisting of an extraction flask (flat-bottomed, short-necked) of capacity 150 m

43、l, 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, of capacity 150 ml, flat-bottomed and short-necked. 5.5 Extraction thimbles, made of defatted filter paper, glass, alumina or polytetr

44、afluoroethylene (PTFE), 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 the extraction apparatus (5.3). ISO 8262-3:2005(E) IDF 124-3:2005(E) ISO and IDF 2005 All rights reserved 3 5.6 Wa

45、ter 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). 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

46、 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 conical flask fitted with a condenser. For example, use a wire gauze and gas burner, a

47、n 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 solvent to be gently distilled from the flasks at a temperature not exceeding 100 C. 5.1

48、4 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. 5.15 Measuring cylinders, of capacities 50 ml, 100 ml and 250 ml. 5.16 Tongs, made of

49、 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 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 recommended sampling method is given in ISO 707 IDF 50. All liquid, viscous or pasty laboratory samples shall be kept at a temperature of