BS-770-7-1997 ISO-2963-1997.pdf
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1、BRITISH STANDARD BS 770-7:1997 ISO 2963:1997 Methods for Chemical analysis of cheese Part 7: Determination of citric acid content of cheese and processed cheese products (enzymatic method) ICS 67.100.30 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GM
2、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-7:1997 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 1997 BSI 09-1999 ISBN 0 580 27823 9 N
3、ational foreword This British Standard reproduces verbatim ISO 2963:1997 and implements it as the UK national standard. It supersedes BS 770-7:1976 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk products, whic
4、h has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them
5、 in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section enti
6、tled “International Standards Correspondence Index”, or using the “Find” facility of the BSI Standards Electronic Catalogue. 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
7、 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, pages i and ii, the ISO title page, pages ii to iv, pages 1 to 8 and a back cover. This standard has been updated (see copyright date) an
8、d may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy,
9、(c) BSI BS 770-7:1997 BSI 09-1999i Contents Page National forewordInside front cover Forewordiii Text of ISO 29631 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: London South Bank Unive
10、rsity, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-7:1997 ii BSI 09-1999 Contents Page Forewordiii 1Scope1
11、 2Definition1 3Principle1 4Reagents1 5Apparatus2 6Sampling2 7Preparation of test sample2 8Procedure3 9Calculation and expression of results4 10Precision4 11Test report5 Annex A (normative) Good Laboratory Practice (GLP) rules for the performance of enzymatic analyses6 Annex B (informative) Statistic
12、al data derived from the results of interlaboratory tests8 Annex C (informative) Bibliography8 Table B.1 Results of interlaboratory tests8 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-7:1997 BSI 09-19
13、99iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for whi
14、ch a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all m
15、atters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 29
16、63 was prepared by Technical Committee ISO/TC 34, Agricultural food products, Subcommittee SC 5, Milk and milk products, in collaboration with the International Dairy Federation (IDF) and the AOAC INTERNATIONAL, and will also be published by these organizations. This second edition cancels and repla
17、ces the first edition (ISO 2963:1974), which has been technically revised. Annex A forms an integral part of this International Standard. Annex B and Annex C are for information only. Descriptors: Agricultural products, food products, dairy products, cheeses, processed cheese, chemical analysis, det
18、ermination of content, citric acid, enzymatic method, reference methods. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: London South Bank University, London South Bank University, Fri D
19、ec 08 13:29:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 770-7:1997 BSI 09-19991 1 Scope This International Standard specifies an enzymatic method for the determination of the citric acid content of cheese and processed cheese products. CAUTION Reliable results will only be obtained if the Good
20、Laboratory Practice (GLP) rules for enzymatic analyses are applied strictly. These GLP rules are given in Annex A. 2 Definition For the purposes of this International Standard, the following definition applies. 2.1 citric acid content mass fraction of substances, determined by the procedure specifie
21、d in this International Standard. It is expressed as a percentage by mass 3 Principle Treatment of an extract of the sample with the following enzymes and biochemical substances: citrate lyase (CL) to convert citric acid to oxaloacetate and acetate; malate dehydrogenase (MDH) and lactate dehydrogena
22、se (LDH) in the presence of reduced nicotinamide-adenine dinucleotide (NADH) to catalyse the reduction of oxaloacetate and its decarboxylation product, pyruvate, to L-malate and L-lactate, respectively, with subsequent conversion of NADH to this oxidized form (NAD+). Determination of the decrease in
23、 concentration of NADH by measurement of the absorbance of the test solution at 340 nm. The citric acid content is proportional to the decrease in NADH concentration. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and (glass-) distilled or demineralized wate
24、r or water of equivalent purity. Use double (glass-) distilled water for the preparation of the enzyme solutions. 4.1 Trichloroacetic acid solution Dissolve 200 g of trichloroacetic acid (CCl3COOH) in water, and dilute with water to 1 000 ml. Mix the solution. 4.2 Sodium hydroxide solution A, c(NaOH
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