BS-770-9-1985 ISO-4099-1984.pdf
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1、BRITISH STANDARD CONFIRMED FEBRUARY 1991 BS 770-9:1985 ISO 4099:1984 Methods for Chemical analysis of cheese Part 9: Determination of nitrate and nitrite contents Cadmium reduction and photometry method NOTEThis Part should be read in conjunction with Part 1 “General introduction”, published separat
2、ely. UDC 637.3.07:546.173 + 546.175 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:49:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-9:1985 This British Standard, having been prepared under the direction of the Dairying Standards Committee, was publish
3、ed under the authority of the Board of BSI and comes into effect on 30 August 1985 BSI 01-2000 First published January 1980 First revision August 1985 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 84/53993 DC ISBN 0 580 14525 5 Committe
4、es responsible for this British 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: Association of British Preserved Milk Manufacturers Association of Public Analys
5、ts Association of Public Analysts of Scotland Creamery Proprietors Association Dairy Trade Federation Department of Trade and Industry (Laboratory of the Government Chemist) Ice Cream Alliance Limited Intervention Board for Agricultural Produce Joint Committee of the Milk Marketing Board and the Dai
6、ry Trade Federation Milk Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food National Institute for Research in Dairying Royal Association of British Dairy Farmers Royal Society of Chemistry Society of Chemical Industry Society of Dairy Technology Un
7、iversity of Reading Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:49:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-9:1985 BSI 01-2000i Contents Page Committees responsibleInside front
8、cover National forewordii 1Scope and field of application1 2Reference1 3Definition1 4Principle1 5Reagents1 6Apparatus2 7Sampling2 8Procedure2 9Expression of results4 10Test report5 Figure Apparatus for nitrate reduction6 Publications referred toInside back cover Licensed Copy: London South Bank Univ
9、ersity, London South Bank University, Fri Dec 08 13:49:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-9:1985 ii BSI 01-2000 National foreword This revision of this Part of BS 770, which has been prepared under the direction of the Dairying Standards Committee, is identical with ISO 4099:1984 “
10、Cheese Determination of nitrate and nitrite contents Method by cadmium reduction and photometry”, prepared by ISO/TC 34, Agricultural food products, of the International Organization for Standardization (ISO). It supersedes BS 770-9:1980, which is withdrawn. Terminology and conventions. The text of
11、the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal mark
12、er. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Where the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. The spelling “sulfur” is used throughout for that element and its derivat
13、ives. In British Standards it is current practice to use the spelling “sulphur”. Cross-reference. The Technical Committee has reviewed the provisions of ISO 707:1984, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related
14、 standard is BS 809 “Methods for sampling milk and milk products”, which is in course of revision. Additional information. With reference to 8.4, for some hard cheeses, it is often advantageous to grate the cheese, rather than grinding, prior to mixing (kneading). NOTETypographical error. In 5.1, th
15、e chemical formula for cadmium sulfate octahydrate should read “3CdSO48H2O”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself conf
16、er immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, 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
17、 in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:49:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-9:1985 BSI 01-20001 1 Scope and field of application This International Standard specifies a method by c
18、admium reduction and photometry for the determination of the nitrate and nitrite contents of cheese. The method is suitable for hard, semi-hard and soft cheeses of various ages and for processed cheese. The detection limits of the method are 5 mg of nitrate per kilogram and 0,5 mg of nitrite per kil
19、ogram. 2 Reference ISO 707, Milk and milk products Methods of sampling. 3 Definition nitrate and nitrite contents of cheese the contents of substances determined by the procedure specified in this International Standard and expressed respectively as milligrams of nitrate ionand of nitrite ionper kil
20、ogram 4 Principle Extraction of the cheese with warm water, precipitation of the fat and proteins, and filtration. Reduction of the nitrate in a portion of the filtrate to nitrite, by means of copperized cadmium. Development of a red colour, in portions of both unreduced filtrate and of the reduced
21、solution, by addition of sulfanilamide and N-1-naphthyl-ethylenediamine dihydrochloride, and spectrometric measurement at a wavelength of 538 nm. Calculation of the nitrite content of the sample and of the total nitrite content after reduction of nitrate, by comparing the measured absorbances with t
22、hose of a series of standard sodium nitrite solutions; calculation of the nitrate content from the difference between these two contents. 5 Reagents All reagents shall be of recognized analytical grade. The water used shall be distilled or deionized water, free from nitrate and nitrite. NOTEIn order
23、 to avoid possible inclusion of small gas bubbles in the copperized cadmium column (6.10), the distilled or deionized water used for the preparation of the column (8.1), for checking the reducing capacity of the column (8.2), and for regeneration of the column (8.3) should preferably be freshly boil
24、ed and afterwards cooled to room temperature. 5.1 Cadmium, granules, diameter 0,3 to 0,8 mm. If cadmium granules are not available commercially, they may be prepared as follows. Place a suitable number of zinc rods in a beaker and cover with a 40 g/l solution of cadmium sulfate octahydrate (CdSO48H2
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