BS-1741-4-1987 ISO-2450-1985.pdf
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1、BRITISH STANDARD BS 1741-4: 1987 ISO 2450:1985 Methods for Chemical analysis of liquid milk and cream Part 4: Determination of fat content of cream ISO title: Cream Determination of fat content Gravimetric method (Reference method) NOTEThis Part should be read in conjunction with Part 1 “General int
2、roduction including preparation of samples”, published separately. UDC 637.12 + 637.148.074:543 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:59:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1741-4:1987 This British Standard, having been prepared under the direction of the Dairying St
3、andards Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1987 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 84/54002 DC ISBN 0 580 15959 0 Committees responsible for this Brit
4、ish Standard The preparation of this British Standard was entrusted by the Dairying Standards Committee (DAC/-) to Technical Committee DAC/3, upon which the following bodies were represented: AFRC Institute of Food Research, Reading Laboratory Association of British Preserved Milk Manufacturers Asso
5、ciation of Public Analysts Association of Public Analysts of Scotland Creamery Proprietors Association Dairy Trade Federation Department of Trade attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full poi
6、nt on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Part of BS 1741”. The symbol “l” has been used to denote litre (and in its submultiples). In British Standards it is current practice to use the symbol “L
7、”. With reference to the NOTE to clause 1, the UK is participating in the preparation of ISO 8262-3 and consideration will be given later to implementing the resulting International Standard as a British Standard. A British Standard does not purport to include all the necessary provisions of a contr
8、act. 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 International StandardCorresponding British Standard ISO 707:1985BS 809:1985 Methods for sampling of milk and
9、milk products (Identical) ISO 3889:1977BS 5522:1977 Specification for milk and milk products Determination of fat content Mojonnier-type fat extraction flasks (Identical) ISO 1211:1984BS 1741 Methods for chemical analysis of liquid milk and cream Part 3:1987 Determination of fat content of liquid mi
10、lk (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment tab
11、le on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:59:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1741-4:1987 BSI 10-19991 0 Introduction This second edition of ISO 2450 has been prepared within the framework of producing a series of methods, which are harmo
12、nized to the greatest possible extent, for the gravimetric determination of the fat content of milk, milk products and milk-based foods. This revision is based on the revised Rse-Gottlieb method for milk specified in ISO 12111), comprising a number of modifications to improve the precision of that m
13、ethod. A more complete explanation of these modifications to the basic Rse-Gottlieb procedure is given in the introduction to ISO 1211. The addition of 5 ml of ethanol before the second extraction (see 8.5.10), in line with other revised methods, has made the dilution with 0,5 % (m/m) salt solution
14、as prescribed in the first edition superfluous and has therefore been replaced by a dilution with water (see 8.5.1). 1 Scope and field of application This International Standard specifies the reference method for the determination of the fat content of raw, processed and cultured cream in which no a
15、ppreciable splitting of fat has occurred. NOTEThe method is not suitable for sour creams with starch or other thickening agents. In this case, and when splitting of fat occurs, recourse has to be made to a method utilizing the Weibull-Berntrop principle as in ISO 8262-32). 2 References ISO 707, Milk
16、 and milk products Methods of sampling. ISO 3889, Milk and milk products Determination of fat content Mojonnier-type fat extraction flasks. 3 Definition fat content of cream all the substances determined by the method specified in this International Standard it is expressed as a percentage by mass 4
17、 Principle Extraction of an ammoniacal ethanolic solution 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 Rs
18、e-Gottlieb principle.) 5 Reagents All reagents shall 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 reag
19、ents, carry out a blank test as specified in 8.3. Use 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 r
20、esidue of the solvents separately by distilling 100 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. 5.1 Ammonia solution, contai
21、ning approximately 25 % (m/m) of NH3, 20 910 g/l. NOTEIf ammonia solution of this concentration is not available, a more concentrated solution of known concentration may be used (see 8.5.2). 5.2 Ethanol, or ethanol denatured by methanol, at least 94 % (V/V). (See 10.5.) 5.3 Congo-red solution Dissol
22、ve 1 g of Congo-red in water and dilute to 100 ml. NOTEThe use of this solution, which allows the interface between the solvent and aqueous layers to be seen more clearly, is optional (see 8.5.3). Other aqueous colour solutions may be used provided that they do not affect the result of the determina
23、tion. 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 Light petroleum, having any boiling range between 30 and 60 C. 1) ISO 1211, Milk Deter
24、mination of fat content Gravimetric method (Reference method). 2) ISO 8262-3, Milk products and milk-based foods Determination of fat content by the Weibull-Berntrop gravimetric method (Reference method) Part 3: Special cases. (At present at the stage of draft.) Licensed Copy: sheffieldun sheffieldu
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