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1、BRITISH STANDARD BS 6049-8: 1998 ISO 11286: 1997 Methods of test for tea Part 8: Classification of grades by particle size analysis ICS 67.140.10 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8:1998 This British Standard, having be
2、en 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 February 1998 BSI 04-1999 ISBN 0 580 29489 7 National foreword This British Standard reproduces verbatim ISO 11286:1997 and impleme
3、nts it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/8, Tea, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or propo
4、sals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them 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 intern
5、ational or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to inclu
6、de 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 confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages
7、i and ii, the ISO title page, page ii, pages 1 and 2 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. Amendments issued since publication Amd. No.DateComments Licen
8、sed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8:1998 BSI 04-1999i Contents Page National foreword Inside Front cover Foreword ii Introduction1 1Scope1 2Normative reference1 3Principle1 4Apparatus1 5Sampling1 6Procedure1 7Calculation1 8C
9、lassification1 9Test report2 Table 1 Grade designations2 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheff
10、ieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8:1998 ii BSI 04-1999 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Stand
11、ards is normally carried out through ISO technical committees. Each member body interested in a subject for which 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 ta
12、ke part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International
13、 Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 11286 was prepared by Technical Committee ISO/TC 34, Agricultural food products, Subcommittee SC 8, Tea. Descriptors: Agricultural products, plant products, tea, grades (quality), classificat
14、ion, size classification, grain size analysis, sieve analysis. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8:1998 BSI 04-19991 Introduction For many years the tea trade has used various systems for the grading nomenclature of tea
15、s according to the sieves used for sorting the teas. However, a designation given in one country does not always have the same meaning in another and it was considered by some countries, in particular tea-producing countries, that a single, international method of classifying tea grades according to
16、 their particle size distributions would facilitate international trade. The method given in this International Standard provides such a system to supplement the existing traditional systems. 1 Scope This International Standard specifies a method for the classification of grades of tea according to
17、an analysis of their particle size. NOTEThis method may not be suitable for blends of tea. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated w
18、as valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard given below. Members of IEC and ISO maintain registers of currently valid International St
19、andards. ISO 3310-1:1990, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. 3 Principle Separation of the tea into different size fractions using a series of sieves on a shaker, followed by weighing of the tea particles retained on each sieve and calculation of
20、the percentage by mass retained on each sieve. 4 Apparatus Usual laboratory apparatus and, in particular, the following. 4.1 Sieve shaker, capable of a vibration rate of 3 000 per min, a vibration stroke of up to 3 mm and a vibration angle of 30, with automatic timer1). 4.2 Test sieves, conforming t
21、o ISO 3310-1, of nominal diameter 200 mm and of nominal aperture sizes 2 mm, 1,4 mm, 1 mm, 710 m, 355 m, 250 m, 150 m and 75 m, together with a base pan (less than 75 m) and a clamp. 5 Sampling Sampling is not part of the method specified in this International Standard. A recommended sampling method
22、 is given in ISO 18392). It is important that the laboratory receive a sample which is truly representative and has not been damaged or changed during transport or storage. 6 Procedure NOTE 1If sufficient of the sample is available, it is recommended that the analysis be carried out in duplicate. 6.
23、1 Arrange the test sieves (4.2) in descending order of mesh size and fit them together. 6.2 Weigh 100 g 1 g of the laboratory sample into a 400 ml beaker. Transfer the tea quantitatively to the top sieve and fit the cover. 6.3 Place the sieves on to the sieve shaker (4.1) and secure them using the c
24、lamp provided. Set an automatic timer to 10 min and start the shaker. 6.4 When the shaker stops, remove the test sieves and carefully separate them. 6.5 Transfer quantitatively the tea that has been retained on each sieve into a series of beakers, previously weighed to the nearest 0,01 g, and weigh
25、to the nearest 0,01 g. NOTE 2It is recommended that an appropriate brush be used to aid the transfer of the tea from the test sieves to the beakers. 7 Calculation Determine the percentage of tea retained on each test sieve and note the mesh sizes of the test sieves on which the largest amount (the p
26、eak) and the second largest amounts of tea were retained. 8 Classification Classify the tea into one of the grades listed in Table 1 in accordance with the definitions given. 1) Endecotts Octagon 200 and Endecotts EFC Mark 1 are examples of suitable shakers available commercially. This information i
27、s given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of these products. 2) ISO 1839:1980, Tea Sampling. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8:1998 2 BSI 04-1999
28、 Table 1 Grade designations Each of the grades 1 to 6 in Table 1 may be divided into subgrades A, B and C, as follows: A: up to 2,0 % passing 355 4m B: more than 2,0 % passing 355 4m C: more than 5,0 % passing 355 4m. Each of the grades 7 to 10 in Table 1 may be divided into subgrades A, B and C, as
29、 follows. A: up to 2,0 % passing 250 4m B: more than 2,0 % passing 250 4m C: more than 5,0 % passing 250 4m. Each of the grades 11 to 15 in Table 1 may be divided into subgrades A, B and C, as follows. A: up to 2,0 % passing 150 4m B: more than 2,0 % and up to 5,0 % passing 150 4m C: more than 5,0 %
30、 passing 150 4m. 9 Test report The test report shall specify: the method in accordance with which sampling was carried out, if known; the method used; and the test result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, toge
31、ther with details of any incidents which may have influenced the result. The test report shall include all information necessary for the complete identification of the sample. GradeDefinition 1Peak in 2 mm 2Peak in 1,4 mm and second highest peak in 2 mm 3Peak in 1,4 mm and second highest peak in 1 m
32、m 4Peak in 1 mm and second highest peak in 1,4 mm 4.5Peak in 1 mm and second highest peak 2 mm 5Peak in 1 mm and second highest peak in 710 4m and number of sieves retaining 25 % = 1 6Peak in 1 mm and second highest peak in 710 4m and number of sieves retaining 25 % = 2 or more 7Peak in 710 4m and s
33、econd highest peak in 1 mm 8Peak in 710 4m and second highest peak in 355 4m 9Peak in 355 4m and second highest peak in 710 4m, and number of sieves retaining 25 % = 2 or more 9.5Peak in 355 4m and second highest peak in 1 mm 10Peak in 355 4m and second highest peak in 710 4m and number of sieves re
34、taining 25 % = 1 11Peak in 355 4m and second highest peak in 250 4m and number of sieves retaining means greater than; means less than. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 3blank Licensed Copy: sheffieldun sheffieldun, na, Wed De
35、c 06 13:37:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-8: 1998 ISO 11286: 1997 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at
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