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1、BRITISH STANDARD BS EN ISO 1211:1995 BS 1741-3: 1995 Milk Determination of fat content Gravimetric method (reference method) The European Standard EN ISO 1741:1995 has the status of a British Standard Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy,
2、(c) BSI BS EN ISO 1211:1995 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on 15 August 1995 BSI 07-1999 The following BSI references relate to the work
3、 on this standard: Committee reference AW/5 Draft announced in BSI News December 1993 ISBN 0 580 24014 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk products, upon which the fo
4、llowing bodies were represented: Association of Public Analysts Department of Trade and Industry (Laboratory of the Government Chemist) Intervention Board Ministry of Agriculture, Fisheries and Food Royal Society of Chemistry Society of Dairy Technology Amendments issued since publication Amd. No.Da
5、teComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 1211:1995 BSI 07-1999i Contents Page Committees responsibleInside front cover National forewordii Foreword2 0Introduction3 1Scope and field of application3 2References3 3De
6、finition3 4Principle3 5Reagents3 6Apparatus4 7Sampling4 8Procedure4 9Expression of results7 10Notes on procedure7 11Test report8 Annex A Alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings9 Figure 1 Before decantation6 Figure 2 After decantation6 Figure 3 Examples of
7、 extraction tubes10 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 1211:1995 ii BSI 07-1999 National foreword This British Standard has been prepared by Technical Committee AW/5 and is the Engli
8、sh language version of EN ISO 1211:1995 Milk Determination of fat content Gravimetric method (Reference method), published by the European Committee for Standardization (CEN). It is identical with ISO 1211:1984 published by the International Organization for Standardization (ISO) in cooperation with
9、 the International Dairy Federation (IDF) and the Association of Official Analytical Chemists (AOAC), and in the preparation of which the UK played a full part. It supersedes BS 1741-3:1987 which is withdrawn. A British Standard does not purport to include all the necessary provisions of a contract.
10、 Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references Publication referred toCorresponding British Standard ISO 707:1985BS 809:1985 Methods for sampling of milk and mil
11、k products ISO 3889:1977BS 5522:1987 Specification for milk and milk products Determination of fat content Mojonnier-type fat extraction flasks Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN ISO title page, pages 2 to 10, an inside back cover an
12、d a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN S
13、TANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 1211 June 1995 ICS 67.100.10 Descriptors: Dairy products, milk, agricultural products, determination of fats, gravimetric analysis, chemical analysis English version Milk Determination of fat content Gravimetric method (Reference method) (ISO 1211:1984)
14、 Lait Dtermination de la teneur en matire grasse Mthode gravimtrique (Mthode de rfrences) (ISO 1211:1984) Milch Bestimmung des Fettgehaltes Gravimetrisches Verfahren (Referenzverfahren) (ISO 1211:1984) This European Standard was approved by CEN on 1995-02-05. CEN members are bound to comply with the
15、 requirements of the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Ce
16、ntral Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status a
17、s the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit E
18、uropen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1995 Copyright reserved to CEN members Ref. No. EN ISO 1211:1995 E Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 1211:19
19、95 BSI 07-1999 2 Foreword The text of the International Standard from ISO/TC 34, Agricultural food products, of the International Organization for Standardization (ISO) has been taken over as a European Standard by the Technical Committee CEN/TC 302, Milk and milk products Methods of sampling and an
20、alysis. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 1995, and conflicting national standards shall be withdrawn at the latest by December 1995. According to the CEN/CENELEC Internal R
21、egulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Licensed Copy: sheffieldun sheffieldu
22、n, na, Sun Nov 19 13:57:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 1211:1995 BSI 07-19993 0 Introduction This International Standard constitutes a revision of ISO/R 1211. Attempts to produce a single International Standard specifying the use of the Rse-Gottlieb method applicable to all mil
23、k products have been found impracticable for the time being. Therefore, it has been decided to revise and harmonize the existing standardized methods for individual products or groups of products and to standardize similar methods for those products for which methods had not been prepared previously
24、. The main modifications as compared to ISO/R 1211 are: a) preference is given to the use of Mojonnier-type fat-extraction flasks and the use of a centrifuge to separate the solvent layers; b) addition of ethanol before the second extraction; c) emphasis is placed on the necessity of cooling the fat
25、-collecting vessels to ambient temperature before performing weighings. The use of a centrifuge enables rapid and complete separation of the solvent layers and minimizes the need for redissolution of the extracted fat or a repetition of the determination. The addition of ethanol before the second ex
26、traction has been specified to reduce the risk of formation of a viscous or gelified aqueous layer, especially in the case of products containing sucrose (for example sweetened condensed milk, edible ices and, to a lesser extent, milk powder). It has been found that this addition distinctly improves
27、 the precision of the method, also for milk. Emphasis has been placed on the necessity of cooling fat-collecting vessels to ambient temperature before weighing, as errors from this source of the order of 0,01 % fat per degree Celsius have been reported for liquid milk. The use of a desiccator is the
28、refore not recommended. The use of an empty control vessel will compensate for these errors to some extent. It has been found, however, that the use of such a vessel together with a blank test on 10 ml of water carried out with the determination is complicated and produces no improvement in precisio
29、n. An empty control vessel is, however, necessary, and is therefore specified when performing the blank test to check the reagents in order to avoid a false impression of the presence or absence of non-volatile matter. 1 Scope and field of application This International Standard specifies the refere
30、nce method for the determination of the fat content of raw and processed liquid milk, partly skimmed milk and skimmed milk in which no appreciable separation or splitting of fat has occurred (see the note to 8.1). NOTEWhen greater accuracy is required for skimmed milk, for instance to establish the
31、operating efficiency of cream separators, the special method for skimmed products, specified in ISO 7208, Skimmed milk, whey and buttermilk Determination of fat content Gravimetric method (Reference method), should be used. 2 References ISO 707, Milk and milk products Methods of sampling. ISO 3889,
32、Milk and milk products Determination of fat content Mojonnier-type fat extraction flasks. 3 Definition fat content of milk all the substances determined by the method specified in this International Standard it is expressed as a percentage by mass 4 Principle Extraction of an ammoniacal ethanolic so
33、lution of a test portion with diethyl ether and light petroleum, removal of the solvents by distillation or evaporation, and determination of the mass of the substances extracted which are soluble in light petroleum. (This is usually known as the Rse-Gottlieb principle.) 5 Reagents All reagents shal
34、l be of recognized analytical grade and shall leave no appreciable residue when the determination is carried out by the method specified. The water used shall be distilled water or water of at least equivalent purity. To test the quality of the reagents, carry out a blank test as specified in 8.3. U
35、se an empty fat-collecting vessel, prepared as specified in 8.4, for mass control purposes. The reagents shall leave no residue greater than 0,5 mg (see 10.1). If the residue of the complete reagent blank test is greater than 0,5 mg, determine the residue of the solvents separately by distilling 100
36、 ml of the diethyl ether and light petroleum respectively. Use an empty control vessel to obtain the real mass of residue which shall not exceed 0,5 mg. Replace unsatisfactory reagents or solvents, or redistil solvents. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 13:57:39 GMT+00:00 2006,
37、Uncontrolled Copy, (c) BSI EN ISO 1211:1995 4 BSI 07-1999 5.1 Ammonia solution, containing approximately 25 % (m/m) of NH3, A20 = 910 g/l. NOTEIf ammonia solution of this concentration is not available, a more concentrated solution of known concentration may be used (see 8.5.1). 5.2 Ethanol, or etha
38、nol denatured by methanol, at least 94 % (V/V). (See 10.5.) 5.3 Congo-red solution Dissolve 1 g of Congo-red in water and dilute to 100 ml. NOTEThe use of this solution, which allows the interface between the solvent aqueous layers to be seen more clearly, is optional (see 8.5.2). Other aqueous colo
39、ur solutions may be used provided that they do not affect the result of the determination. 5.4 Diethyl ether, free from peroxides (see 10.3) and containing no or not more than 2 mg/kg of antioxidants and complying with the requirements for the blank test (see clause 5, and also 10.1 and 10.4). 5.5 L
40、ight petroleum, having any boiling range between 30 and 60 C. 5.6 Mixed solvent, prepared shortly before use by mixing equal volumes of the diethyl ether (5.4) and the light petroleum (5.5). 6 Apparatus WARNING Since the determination involves the use of volatile flammable solvents, electrical appar
41、atus employed shall be required to comply with legislation relating to the hazards in using such solvents. Usual laboratory equipment, and in particular 6.1 Analytical balance 6.2 Centrifuge, in which the fat-extraction flasks or tubes (6.6) can be spun at a rotational frequency of 500 to 600 min1 t
42、o produce a gravitational field of 80 g to 90 g at the outer end of the flasks or tubes. NOTEThe use of the centrifuge is optional but recommended (see 8.5.5). 6.3 Distillation or evaporation apparatus, to enable the solvents and ethanol to be distilled from the flasks or to be evaporated from beake
43、rs and dishes (see 8.5.12) 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 2 C throughout the working space. The oven shall be fitted with a suitable thermometer. 6.5 Water-bath, capa
44、ble of being maintained at 35 to 40 C. 6.6 Mojonnier-type fat-extraction flasks, as-specified in ISO 3889. NOTEIt is also possible to use fat-extraction tubes, with siphon or wash-bottle fittings, but the procedure is then different and is specified in the annex. The flasks (or tubes, see the note)
45、shall be provided with good quality bark corks or stoppers of other material (for example silicone rubber) unaffected by the reagents used. Bark corks shall be extracted with the diethyl ether (5.4), kept in water at 60 C or more for at least 15 min, and shall then be allowed to cool in the water so
46、 that they are saturated when used. 6.7 Rack, to hold the fat-extraction flasks (or tubes) (see 6.6). 6.8 Wash bottle, suitable for use with the mixed solvent (5.6). A plastic wash bottle shall not be used. 6.9 Fat-collecting vessels, for example boiling flasks (flat-bottomed), of capacity 125 to 25
47、0 ml, conical flasks, of capacity 250 ml, or metal dishes. If metal dishes are used, they shall preferably be of stainless steel, shall be fiat-bottomed, preferably with a spout, and shall have a diameter of 80 to 100 mm and a height of approximately 50 mm. 6.10 Boiling aids, fat-free, of non-porous
48、 porcelain or silicon carbide (optional in the case of metal dishes). 6.11 Measuring cylinders, of capacities 5 and 25 ml. 6.12 Pipettes, graduated, of capacity 10 ml. 6.13 Tongs, made of metal, suitable for holding flasks, beakers or dishes. 7 Sampling See ISO 707. All laboratory samples shall be k
49、ept at a temperature of 3 to 6 C from the time of sampling to the time of commencing the procedure. 8 Procedure NOTEThe alternative procedure using fat-extraction tubes with siphon or wash-bottle fittings (see the note to 6.6) is described in the annex. 8.1 Preparation of the test sample Adjust the temperature of the laboratory sample (clause 7) to 35 to 40 C, by means of the water-bath (6.5) if necessary. Mix the sample thoroughly, but gently, by repeatedly inverting the sample bottle without causing frothing o