BS-6049-3-1994 ISO-9768-1994.pdf
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1、BRITISH STANDARD BS 6049-3: 1994 ISO 9768:1994 Incorporating Amendment No. 1 Methods of test for Tea Part 3: Determination of water extract Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:02:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-3:1994 This British Standard, having been pre
2、pared 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 December 1994 BSI 05-1999 First published December 1980 Second edition November 1990 Third edition December 1994 The following BSI refere
3、nces relate to the work on this standard: Committee reference AW/8 Draft for comment 92/56272 DC ISBN 0 580 23531 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Consumer Products and Services Sector Board to Technical Committee AW/8,
4、upon which the following bodies were represented: Campden Food and Drink Research Association Ministry of Agriculture, Fisheries and Food Natural Resources Institute Tea Trade Technical Committee United Kingdom Tea Association Amendments issued since publication Amd. No.DateComments 10193October 199
5、8Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:02:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-3:1994 BSI 05-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative reference1 3Definition1 4Princip
6、le1 5Apparatus1 6Sampling1 7Preparation of test sample1 8Procedure1 9Calculation2 10Precision2 11Test report2 Annex A (informative) Statistical results of interlaboratory tests on tea3 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:02:09 GMT+00:00 2006,
7、 Uncontrolled Copy, (c) BSI BS 6049-3:1994 ii BSI 05-1999 National foreword This Part of BS 6049 has been prepared under the direction of the Consumer Products and Services Sector Board. It supersedes the 1990 edition of BS 6049-3, which is withdrawn, and implements an agreement, to which the UK was
8、 a party, reached in Subcommittee 8, Tea, of Technical Committee TC 34, Agricultural food products, of the International Organization for Standardization (ISO). The UK also provides the secretariat for the Subcommittee. This Part of BS 6049 is identical with ISO 9768:1994 Tea Determination of water
9、extract. The principal difference between this Part of BS 6049 and the 1990 edition is that provision has been made for grinding very large leaf teas before the determination. The details of statistical results of interlaboratory tests given in Annex A are supplied for information only. Cross-refere
10、nces This standard describes a method of test only and should not be referred to as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance with BS 6049-3. A British Standard does not purport to include all the necessary prov
11、isions 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. International standardCorresponding British Standard ISO 1573:1980BS 6049 Methods of test for tea Part 2:1981
12、Determination of loss in mass at 103 C (Identical) ISO 1839:1980BS 5987:1980 Methods for sampling tea (Identical) ISO 5725:1986BS 5497 Precision of test methods Part 1:1987 Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests (Identica
13、l) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, 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 in
14、side front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:02:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 9768:1994(E) BSI 05-19991 1 Scope This International Standard specifies a method for the determination of the water extract from tea. 2 Normative reference The following s
15、tandard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged t
16、o investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 1573:1980, Tea Determination of loss in mass at 103 C. 3 Definition For the purposes of this International Stan
17、dard, the following definition applies. 3.1 water extract the soluble matter extracted from a test portion by boiling water, under the conditions specified in this International Standard, expressed as a percentage by mass on a dry basis 4 Principle Extraction of soluble matter from a test portion of
18、 the product by means of water boiling under reflux. Filtration, washing, drying and weighing of the hotwater-insoluble residue. Calculation of the water extract. 5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Oven, constant-temperature and fan-assisted, capable of bei
19、ng operated at 103 C 2 C. 5.2 Crucible, made of sintered borosilicate glass, of porosity grade P160 (pore size index 100 4m to 160 4m), 40 mm in diameter and of 70 ml capacity. 5.3 Desiccator, containing an efficient desiccant. 5.4 Flask, of 500 ml capacity, fitted with a reflux condenser. 5.5 Filte
20、r flask, of 1 litre capacity, for vacuum filtration. 5.6 Test sieves, of nominal aperture size 1,4 mm and 3 mm. 5.7 Analytical balance, capable of weighing to an accuracy of 0,001 g. 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damage
21、d or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 1839.1) 7 Preparation of test sample Use a test sample of known dry matter content, determined using the method specified in ISO 1573.
22、Teas of which 60 % or more is retained on a 1,4 mm sieve shall be ground to pass a 3 mm sieve prior to analysis. 8 Procedure NOTE 1If it is required to check whether the repeatability requirement is met, carry out two determinations on the same test sample. 8.1 Preparation of the crucible Heat the c
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