1、BRITISH STANDARD CONFIRMED OCTOBER1992 BS4401-8: 1976 Methods of test Meat and meat products Part8: Determination of nitrite content UDC637.5:664.91/.94:543:546.173BS4401-8:1976 This British Standard, having been prepared under the directionof the Farming, Food andAgriculture Standards Committee, wa
2、s published underthe authority of the Executive Board on 30 July1976 BSI08-1999 The following BSI references relate to the work on this standard: Committee reference FAC/6 Draft for comment72/52093 ISBN 0 580 09341 7 Co-operating organizations The Farming, Food and Agriculture Standards Committee, u
3、nder whose supervision this British Standard was prepared, consists of representatives from the following Government departments and consumer, scientific and industrial organizations: Agricultural Co-operative Company and Market Services British Food Manufacturing Industries Research Association* Br
4、itish Industrial Biology Research Association Central Council for Agricultural and Horticultural Co-operation Consumer Standards Advisory Committee of BSI Department of Agriculture and Fisheries for Scotland Department of Industry Laboratory of the Government Chemist* Flour Milling and Baking Resear
5、ch Association Food Manufacturers Federation Inc. Campden Food Preservation Research Association* Institute of Brewing Local Authorities Joint Advisory Committee on Food Standards Ministry of Agriculture, Fisheries and Food* Ministry of Agriculture, Government of Northern Ireland National Farmers Un
6、ion* National Farmers Union of Scotland Tobacco Advisory Committee The organizations marked with an asterisk in the above list, together with the following were directly represented on the committee entrusted with the preparation of this British Standard: Agricultural Research Council British Bacon
7、Curers Federation British Poultry Federation Institute of Meat Licensed Animal Slaughterers and Salvage Association Meat and Livestock Commission Meat Manufacturers Association National Council of Associations of Fresh Meat Wholesalers National Federation of Meat Traders Associations Public Health L
8、aboratory Service Sausage and Meat Pie Manufacturers Association Society of Analytical Chemistry Society of Chemical Industry Ulster Farmers Union Amendments issued since publication Amd. No. Date of issue CommentsBS4401-8:1976 BSI 08-1999 i Contents Page Co-operating organizations Inside front cove
9、r Foreword ii 1 Scope 1 2 References 1 3 Definition 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Sample 2 8 Procedure 2 9 Expression of result 2 10 Test report 3 Publications referred to Inside back coverBS4401-8:1976 ii BSI 08-1999 Foreword The separate Parts of this British Standard describe chemi
10、cal methods prepared by Subcommittee6 Meat and Meat Products, of ISO/TC34 Agricultural Food Products. Apart from editorial modifications and the difference described in the note to clause1, this Part is in technical agreement with ISO2918. A British Standard does not purport to include all the neces
11、sary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 t
12、o4, 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 table on the inside front cover.BS4401-8:1976 BSI 08-1999 1 1 Scope This Part of BS4401 describes a reference method for th
13、e determination of the nitrite content of meat and meat products. The method is applicable to all meat products, other than those having an unusually high content of strongly reducing substances. Strongly reducing substances (e.g.ascorbic acid, ascorbates) tend to reduce nitrite under the acidic con
14、ditions obtained in this method. If the content of reducing substances is much higher than that which has normally resulted from the manufacturing processes hitherto applied, the results obtained by this method could be misleading. NOTEISO2918 describes the method as suitable for meat and meat produ
15、cts, without indicating any limitation. 2 References The titles of the British Standards referred to in this standard are listed on the inside back cover. 3 Definition For the purposes of this British Standard the following definition applies: nitrite content the quantity of nitrite determined by th
16、e procedure described. Nitrite content is expressed as milligrams of sodium nitrite per kilogram (parts per million) 4 Principle The method consists of the extraction of a test portion with hot water, precipitation of the proteins and filtration. After development of a red colour by addition of sulp
17、hanilamide and N-1-naphthylethylenediamine dihydrochloride to the filtrate, photometric measurement is carried out at a wavelength of538nm. 5 Reagents 5.1 General. The reagents described in5.2, 5.3 and5.4 are required and shall be of analytical quality. The water used shall comply with the requireme
18、nts of BS3978. 5.2 Solutions for precipitation of proteins 5.2.1 Reagent I. Dissolve106g of potassium ferrocyanide trihydrate K 4 Fe(CN) 6 .3H 2 O in water and dilute to1000ml. 5.2.2 Reagent II. Dissolve220g of zinc acetate dihydrate Zn(CH 3 COO) 2 .2H 2 O and30ml of glacial acetic acid in water and
19、 dilute to1000ml. 5.2.3 Borax solution, saturated. Dissolve50g of disodium tetraborate decahydrate (Na 2 B 4 O 7 .10H 2 O) in1000ml of tepid water and cool to room temperature. 5.3 Standard sodium nitrite solutions. Dissolve1.000g of sodium nitrite (NaNO 2 ) in water and dilute to100ml in a one-mark
20、 volumetric flask. Pipette5ml of the solution into a1000ml one-mark volumetric flask. Dilute to the mark. Prepare a series of standard solutions by pipetting5ml,10ml and20ml respectively of this solution into100ml one-mark volumetric flasks and diluting to the mark with water. These standard solutio
21、ns contain respectively2.54g,5.04g and10.04g of sodium nitrite per millilitre. The standard solutions and the dilute(0.05g/l) sodium nitrite solution from which they are prepared shall be made up on the day of use. 5.4 Solutions necessary for colour development 5.4.1 Solution I. Dissolve2g of sulpha
22、nilamide (NH 2 C 6 H 4 SO 2 NH 2 ) in800ml of water by heating on a water bath. Cool, filter if necessary, and add100ml of concentrated hydrochloric acid ( 20 1.19g/ml), while stirring. Dilute to1000ml with water. 5.4.2 Solution II. Dissolve0.25g of N-1-naphthylethylenediamine dihydrochloride (C 10
23、H 7NHCH 2CH 2 NH 2 .2HCI) in water. Dilute to250ml with water. Store the solution in a well stoppered brown bottle and keep it in a refrigerator, for not longer than one week. 5.4.3 Solution III. Dilute445ml of concentrated hydrochloric acid ( 20 1.19g/ml) to1000ml with water. 6 Apparatus Usual labo
24、ratory equipment is required and, in particular, the following items. 6.1 Mechanical meat mincer, laboratory size, fitted with a perforated plate with holes not greater than4mm in diameter. 6.2 Analytical balance 6.3 One-mark volumetric flasks,100ml,200ml and1000ml sizes, class B complying with the
25、requirements of BS1792. 6.4 One-mark pipettes,10ml size and, if necessary, another size according to the aliquot of flitrate (see8.5.1). The pipettes shall comply with the requirements for class A of BS1583.BS4401-8:1976 2 BSI 08-1999 6.5 Boiling water bath 6.6 Photoelectric colorimeter, or spectrop
26、hotometer, with cells of1cm optical path length. 6.7 Fluted filter paper, diameter about15cm, free of nitrite. 6.8 Conical flask,300ml. 7 Sample 7.1 Proceed from a representative sample of at least200g. (See BS . . . . 1)“Methods for sampling meat and meat products”.) 7.2 Prepare the test sample (se
27、e8.1) immediately or, if this cannot be done, store the sample at a temperature of0 to5 C, for not longer than four days. 8 Procedure 8.1 Preparation of test sample. Make the sample homogeneous by passing it at least twice through the meat mincer(6.1) and mixing. Keep the homogenized sample in a com
28、pletely filled, air-tight, closed container under refrigeration. Analyse uncooked products immediately after homogenization. For other samples, analyse the test sample as soon as possible, but always within24h. 8.2 Duplicate procedure. Carry out in duplicate the procedure described in8.3, 8.4 and8.5
29、. 8.3 Test portion. Weigh, to the nearest milligram, about10g of the test sample. 8.4 Precipitaton of protein 8.4.1 Transfer the test portion quantitatively into the conical flask(6.8) and add successively5ml of saturated borax solution(5.2.3) and100ml of water at a temperature not below70 C. 8.4.2
30、Heat the flask and its contents for15min on the boiling water bath(6.5) and shake the flask repeatedly. 8.4.3 Allow the flask and its contents to cool to room temperature and add successively2ml of reagentI(5.2.1) and2ml of reagentII(5.2.2). Mix thoroughly after each addition. 8.4.4 Transfer the con
31、tents to a200ml one-mark volumetric flask(6.3). Dilute to the mark with water and mix. Allow the flask to stand for30min at room temperature. 8.4.5 Carefully decant the supernatant liquid and filter it through the fluted filter paper(6.7) so as to obtain a clear solution. 8.5 Colour measurement 8.5.
32、1 Pipette an aliquot portion of the filtrate (V ml), but not more than25ml, into a100ml one-mark volumetric flask(6.3) and add water to obtain a volume of about60ml. 8.5.2 Add10ml of solutionI(5.4.1), followed by6ml of solutionIII(5.4.3), mix and leave the solution for5min at room temperature in the
33、 dark. 8.5.3 Add2ml of solution II(5.4.2), mix and leave the solution for3min to10min at room temperature in the dark. Dilute to the mark with water. 8.5.4 Measure the absorbance of the solution at a wavelength of538nm in a1cm cell using the photoelectric colorimeter or spectrophotometer(6.6). NOTEI
34、f the absorbance of the coloured solution obtained from the test portion exceeds that obtained for the standard solution with the highest concentration, repeat the operations described in8.5 reducing the quantity of filtrate pipetted in8.5.1. 8.6 Calibration curve 8.6.1 Into a100ml one-mark volumetr
35、ic flask(6.3) pipette10ml of water and into three similar flasks pipette, respectively,10ml of each of the standard sodium nitrite solutions, thus preparing a series of flasks containing the following masses of sodium nitrite: 04g,254g,504g and1004g. 8.6.2 To each flask add water to increase the vol
36、ume to about60ml and proceed as described in8.5.2 to8.5.4. 8.6.3 Draw the calibration curve by plotting the measured absorbance of the test solution (see8.5.4) calculate the the100ml flasks. 9 Expression of result 9.1 Calculation. From each of the duplicate values for the absorbance of the test solu
37、tion (see8.5.4) calculate the corresponding nitrite content (N), expressed in milligrams of sodium nitrite per kilogram, using the following formula: 1) In course of preparation. N 200 m 1 m 0 V - =BS4401-8:1976 BSI 08-1999 3 9.2 Agreement between duplicates. The difference between the two values ca
38、lculated as described in9.1 shall not exceed10% of their mean value. If this requirement is not complied with, the result is not valid. 9.3 Mean value. Provided that the duplicate values calculated as described in9.1 comply with the requirement of9.2, calculate the mean value and express this result
39、, to the nearest milligram per kilogram of sample, as the nitrite content. 10 Test report State in the test report the method used and the result obtained. Mention also all operating conditions not specified in this Part of this standard or regarded as optional, as well as any circumstances that may
40、 have influenced the result. Include in the report all details necessary for complete identification of the sample. where m 0 is the mass, in grams, of the test portion; m 1 is the value given by the calibration curve for the mass of sodium nitrite, in micrograms, corresponding to the absorbance of
41、the test solution (see8.6.1); V is the volume, in millilitres, of the aliquot portion of the flitrate (see8.5.1) taken for the photometric determination.4 blankBS4401-8:1976 BSI 08-1999 Publications referred to This standard makes reference to the following British Standard and International Standar
42、d: BS1583, One-mark pipettes. BS1792, One-mark volumetric flasks. BS3978, Water for laboratory use. BS . . , Methods for sampling meat and meat products 2) . ISO2918, Meat and meat products Determination of nitrite content (reference method). 2) In course of preparationBS4401-8: 1976 BSI 389 Chiswic
43、k High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amen
44、dment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard wou
45、ld inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of st
46、andards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been publ
47、ished as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available w
48、hich give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax:02089967048. Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. For details of these and other benefi
49、ts contact Membership Administration. Tel:02089967002. Fax:02089967001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the international standardization bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, photocopying, recording or otherwise without prior written permission from BSI. This does not preclude the free use, in the cours
