1、March 2009DEUTSCHE NORM English price group 12No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 67.100.10!$VZH“1515537ww
2、w.din.deDDIN EN ISO 2450Cream Determination of fat content Gravimetric method (Reference method) (ISO 2450:2008)English version of DIN EN ISO 2450:2009-03Sahne Bestimmung des Fettgehaltes Gravimetrisches Verfahren (Referenzverfahren) (ISO 2450:2008)Englische Fassung DIN EN ISO 2450:2009-03Supersedes
3、DIN EN ISO 2450:2000-06www.beuth.deDocument comprises 21 pagesDIN EN ISO 2450:2009-03 2 National foreword This standard has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France), Subcommittee SC 5 “Milk and milk products” (Secretariat: NEN, Netherlands) in colla
4、boration with Technical Committee CEN/TC 302 “Milk and milk products Methods of sampling and analysis” (Secretariat: NEN, Netherlands). The responsible German body involved in its preparation was the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standa
5、rds Committee), Technical Committee Milch und Milchprodukte Probenahme- und Untersuchungsverfahren. Based on the results of parallel voting, ISO 2450:2008 has been adopted as a European Standard. For reasons of environmental and worker protection, the German employers liability insurance association
6、s and inspectorates forbid the open evaporation of diethyl ether, which this standard allows as an alternative method. One way of reducing risks is to substitute diethyl ether with an equivalent amount of tert-butyl methyl ether (t-BME). This deviation from the specified procedure is to be stated in
7、 the test report. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO 707 DIN EN ISO 707 ISO 835 DIN EN ISO 835 ISO 1042 DIN EN ISO 1042 ISO 4788 DIN EN ISO 4788 Amendments This standard differs from DIN EN ISO 2450:2000-06 as follows: a) C
8、lause 1 “Scope” has been rendered more precise. b) Clause 2 “Normative references” and clause 7 “Sampling” have been revised. c) The standard has been revised in form and substance and brought in line with the current rules of presentation. d) The bibliography has been updated. Previous editions DIN
9、 10312: 1971-05 DIN 10312: 1991-01 DIN EN ISO 2450: 2000-06 DIN EN ISO 2450:2009-03 3 National Annex NA (informative) Bibliography DIN EN ISO 707, Milk and milk products Guidance on sampling DIN EN ISO 835, Laboratory glassware Graduated pipettes DIN EN ISO 1042, Laboratory glassware One-mark volume
10、tric flasks DIN EN ISO 4788, Laboratory glassware Graduated measuring cylinders DIN EN ISO 2450:2009-03 4 This page is intentionally blank EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 2450October 2008ICS 67.100.10 Supersedes EN ISO 2450:1999 English VersionCream - Determination of fat conte
11、nt - Gravimetric method(Reference method) (ISO2450:2008)Crme - Dtermination de la teneur en matire grasse -Mthode gravimtrique (Mthode de rfrence) (ISO 2450:2008)Sahne - Bestimmung des Fettgehaltes - GravimetrischesVerfahren (Referenzverfahren) (ISO 2450:2008)This European Standard was approved by C
12、EN on 14 October 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards
13、may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the C
14、EN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands
15、, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any fo
16、rm and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 2450:2008: EContents Page Foreword3 1 Scope 4 2 Normative reference 4 3 Terms and definitions .4 4 Principle5 5 Reagents.5 6 Apparatus .5 7 Sampling.6 8 Preparation of test sample7 9 Procedure .7 9.1 Test portion 7 9.2 Bl
17、ank tests7 9.3 Preparation of fat-collecting vessel.8 9.4 Determination.8 10 Calculation and expression of results.10 10.1 Calculation10 10.2 Expression of results 11 11 Precision.11 11.1 Interlaboratory test 11 11.2 Repeatability.11 11.3 Reproducibility.11 12 Test report 11 Annex A (informative) No
18、tes on procedures 12 Annex B (informative) Alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings .14 Bibliography 17 2EN ISO 2450:2008 (E) DIN EN ISO 2450:2009-03 EN ISO 2450:2008 (E) Foreword This document (EN ISO 2450:2008) has been prepared by Technical Committee IS
19、O/TC 34 “Agricultural food products” in collaboration with Technical Committee CEN/TC 302 “Milk and milk products - Methods of sampling and analysis”, the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identic
20、al text or by endorsement, at the latest by April 2009, and conflicting national standards shall be withdrawn at the latest by April 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held respon
21、sible for identifying any or all such patent rights. This document supersedes EN ISO 2450:1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
22、Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 2450:2008 ha
23、s been approved by CEN as EN ISO 2450:2008 without any modification. 3DIN EN ISO 2450:2009-03 WARNING The use of this International Standard may involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety problems associated with its
24、use. It is the responsibility of the user of this International Standard to establish safety and health practices and determine the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies the reference method for the determination of the fat content of raw
25、, processed and sour cream in which no appreciable separation or breakdown of fat, due to lipolysis, has occurred. The method is not applicable to sour creams with starch or other thickening agents. NOTE If the method is not applicable and when separation or breakdown of fat occurs, a method utilizi
26、ng the Weibull-Berntrop principle is suitable (see ISO 8262-3|IDF 124-33). 2 Normative reference The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenc
27、ed document (including any amendments) applies. ISO 835, Laboratory glassware Graduated pipettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 3889IDF 219, Milk and milk products Specification of Mojonnier-type fat extraction flasks ISO 4788, Laboratory glassware Graduated measuring
28、cylinders 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 fat content of cream mass fraction of substances determined by the procedure specified in this International Standard NOTE The fat content is expressed as a percentage mass fraction. 4
29、EN ISO 2450:2008 (E) DIN EN ISO 2450:2009-03 4 Principle 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
30、the Rse-Gottlieb principle. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and only 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
31、(see 9.2.2). 5.1 Ammonia solution, containing a mass fraction of NH3of approximately 25 % (20= 910 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 (C2H5OH), or ethanol denatured by methano
32、l, containing a volume fraction of ethanol of at least 94 %. (See Clause A.5.) 5.3 Congo red solution Dissolve 1 g of Congo red (C32H22N6Na2O6S2) in water in a 100 ml one-mark volumetric flask (6.14). Make up to the mark with water. NOTE The use of this solution, which allows the interface between t
33、he solvent and aqueous layers to be seen more clearly, is optional (see 9.4.3). Other aqueous indicator solutions can be used provided that they do not affect the result of the determination. 5.4 Diethyl ether (C2H5OC2H5), free from peroxides (see Clause A.3), containing no more than 2 mg/kg of anti
34、oxidants, and complying with the requirements for the blank test (see 9.2.2, Clauses A.1 and A.4). WARNING The use of diethyl ether can lead to hazardous situations. Observe current safety precautions for handling, use, and disposal. 5.5 Light petroleum, with any boiling range between 30 C and 60 C
35、or, as equivalent, pentane (CH3CH23CH3) with a boiling point of 36 C and complying with the requirements for the blank test (see 9.2.2, Clauses A.1 and A.4). The use of pentane is recommended because of its higher purity and consistent quality. 5.6 Mixed solvent Shortly before use, mix equal volumes
36、 of diethyl ether (5.4) and light petroleum (5.5). 6 Apparatus WARNING Since the determination involves the use of volatile flammable solvents, all electrical apparatus employed shall comply with legislation relating to the hazards in using such solvents. Usual laboratory equipment and, in particula
37、r, the following. 6.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. 5EN ISO 2450:2008 (E) DIN EN ISO 2450:2009-03 6.2 Centrifuge, capable of holding the fat-extraction flasks or tubes (6.6) and capable of spinning at a rotational frequency of 500 min1to 6
38、00 min1to produce a radial acceleration of 80g to 90g at the outer end of the flasks or tubes. The use of the centrifuge is optional but recommended (see 9.4.6). 6.3 Distillation or evaporation apparatus, for distilling the solvents and ethanol from the boiling or conical flasks, or evaporating from
39、 beakers and dishes (see 9.4.13) at a temperature not exceeding 100 C. 6.4 Drying oven, electrically heated, with ventilation port(s) fully open, capable of being maintained at a temperature of 102 C 2 C throughout its working space. The oven shall be fitted with a suitable thermometer. 6.5 Water ba
40、th, capable of being maintained at a temperature between 35 C and 50 C. 6.6 Mojonnier-type fat-extraction flasks, as specified in ISO 3889IDF 219. NOTE It is also possible to use fat-extraction tubes, with siphon or wash-bottle fittings, but then the procedure is different. The alternative procedure
41、 is given in Annex B. The fat-extraction flasks shall be provided with good quality cork bungs or stoppers of other material e.g. silicone rubber or polytetrafluoroethylene (PTFE) unaffected by the reagents used. Cork bungs shall be extracted with the diethyl ether (5.4), kept in water at a temperat
42、ure of 60 C or more for at least 15 min, and shall then be allowed to cool in the water so that they are saturated when used. 6.7 Rack, for holding the fat-extraction flasks (or tubes) (6.6). 6.8 Wash bottle, suitable for use with the mixed solvent (5.6). A plastics wash bottle shall not be used. 6.
43、9 Fat-collecting vessels, such as boiling flasks (flat-bottomed), of capacities 125 ml to 250 ml, conical flasks, of capacity 250 ml, or metal dishes. If metal dishes are used, they shall be of stainless steel, flat-bottomed with a diameter of 80 mm to 100 mm and a height of approximately 50 mm. 6.1
44、0 Boiling aids, fat-free, of non-porous porcelain or silicon carbide (optional when metal dishes are used). 6.11 Measuring cylinders, of capacities 5 ml and 25 ml, complying with the requirements of ISO 4788, class A, or any other apparatus suitable for the product concerned. 6.12 Pipettes, graduate
45、d, of capacity 10 ml, complying with the requirements of ISO 835, class A. 6.13 Tongs, made of metal, for holding flasks, beakers or dishes. 6.14 Volumetric flask, one-mark, of capacity 100 ml, complying with the requirements of ISO 1042, class A. 7 Sampling A representative sample should have been
46、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 International Standard. A recommended sampling method is given in ISO 707IDF 501. 6EN ISO 2450:2008 (E) DIN EN ISO 2450:2009-03 Store laboratory sample
47、s at a temperature between 2 C and 6 C from the time of sampling to the time of commencing the procedure. 8 Preparation of test sample Warm the test sample to a temperature of between 35 C and 40 C by means of the water bath (6.5), if necessary. Thoroughly, but gently, mix the test sample by repeate
48、dly inverting the sample bottle, or, if the cream is very thick, by stirring with a spatula, without causing frothing or churning, and cool quickly to approximately 20 C. Sour cream should not be warmed but should be thoroughly stirred. Churned cream should not be cooled as it has to be weighed at a
49、 temperature of between 30 C and 40 C (see 9.1). NOTE A reliable value for the fat content cannot be expected: a) when a distinct smell of free fatty acids is perceptible; b) if during, or after, preparation of the test sample, white particles are visible on the walls of the sample bottle or fat droplets float on the surface of the sample. In these cases, a method utilizing the Weibull-Berntrop principle is suitable (see ISO 8262-3IDF 124-33). 9 Procedure NOTE 1 If it is required to check whether the
