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1、BRITISH STANDARD BS 6986-3: 1990 ISO 7513:1990 Analysis of instant tea Part 3: Method for determination of moisture content (loss in mass at 103 C) Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 This British Standard, having
2、been prepared under the direction of the Agriculture and Food Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 30 November 1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference AFC/8 Draft for
3、comment 89/52867 DC ISBN 0 580 19212 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Agriculture and Food Standards Policy Committee (AFC/-) to Technical Committee AFC/8, upon which the following bodies were represented: Campden Food a
4、nd Drink Research Association Department of Trade and Industry (Laboratory of the Government Chemist) Ministry of Agriculture, Fisheries and Food Natural Resources Institute Tea Producers Association United Kingdom Tea Association Amendments issued since publication Amd. No.DateComments Licensed Cop
5、y: sheffieldun sheffieldun, na, Wed Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 BSI 12-1999i Contents Page Committees responsibleInside front cover National forewordii Introduction1 1Scope1 2Normative reference1 3Principle1 4Apparatus1 5Sampling1 6Preparation of the tes
6、t sample1 7Procedure1 8Expression of results2 9Precision2 10Test report2 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 ii BSI 12-1999 National foreword This Part of BS 6986 has bee
7、n prepared under the direction of the Agriculture and Food Standards Policy Committee. It implements an agreement, to which the UK was a party, reached in Subcommittee 8, Tea, of Technical Committee TC 34, Agricultural food products, of the International Organization for Standardization (ISO). The U
8、K also provides the secretariat for the Subcommittee. This Part of BS 6986 is identical with ISO 7513:1990 “Instant tea in solid form Determination of moisture content (loss in mass at 103 C)”. This standard describes a method of test only and should not be referred to as a specification defining li
9、mits of purity. Reference to the standard should indicate that the method of test used is in accordance with BS 6986-3. 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
10、 a British Standard does not of itself confer immunity from legal obligations. Cross-reference International StandardCorresponding British Standard BS 6986 Analysis of instant tea ISO 7516:1984Part 1:1988 Methods of sampling (Identical) Summary of pages This document comprises a front cover, an insi
11、de front cover, pages i and ii, pages 1 and 2, 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. Licensed Copy: sheffieldun sheffieldun, na, Wed
12、 Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 BSI 12-19991 Introduction The loss in mass of instant tea in solid form when it is heated in air at a temperature near 100 C is conventionally designated the “moisture content”, the contribution to this loss in mass made by s
13、mall amounts of other volatile constituents being regarded as negligible for practical purposes. 1 Scope This International Standard specifies a method for the determination of the moisture content of instant tea in solid form as received (loss in mass at 103 C). 2 Normative reference The following
14、standard 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
15、to 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 7516:1984, Instant tea in solid form Sampling. 3 Principle Heating a test portion of the instant tea in an air
16、 oven at 103 C for 2 h and weighing of the dried test portion. NOTE 1The loss in mass will consist mostly of loss in water content and small amounts of non-water volatile substances that will vaporize under the test conditions used. NOTE 2A drying period of 2 h is used because this time interval giv
17、es results which agree best with those obtained using the Karl Fischer method of determining the moisture content of instant tea. 4 Apparatus Usual laboratory apparatus and, in particular, the following. 4.1 Oven, constant-temperature and fan-assisted, capable of being controlled at 103 C 2 C. 4.2 W
18、eighing bottle or dish, with a close-fitting lid, made of aluminium or glass, approximately 70 mm in diameter and 20 mm in height. 4.3 Desiccator, containing an efficient desiccant. 5 Sampling Sampling shall have been carried out in accordance with ISO 7516. NOTE 3The moisture content of samples is
19、likely to increase on exposure to the atmosphere. It is therefore important to carry out the determination as soon as possible after sampling. 6 Preparation of the test sample Thorougly mix the instant tea sample as received by shaking or inverting the sealed sample container. 7 Procedure 7.1 Prepar
20、ation of the weighing bottle or dish Remove the lid from the weighing bottle or dish (4.2) and heat both for 1 h in the oven (4.1) controlled at 103 C 2 C. Cool in the desiccator (4.3). After cooling to room temperature, fit the lid and weigh to the nearest 0,001 g. 7.2 Test portion Open the sample
21、container and immediately weigh, to the nearest 0,001 g, about 4 g of the prepared test sample (clause 6) into the prepared weighing bottle or dish (7.1), with the lid placed alongside. 7.3 Determination Heat the weighing bottle or dish and contents, with the lid removed and placed alongside, in the
22、 oven (4.1) at 103 C 2 C for 2 h. The oven door shall not be opened during the heating period. Remove from the oven and immediately replace the lid. Transfer to the desiccator (4.3), remove the lid (leaving the lid in the desiccator) and allow to cool in the closed desiccator for at least 30 min. Re
23、move from the desiccator, replace the lid and weigh to the nearest 0,001 g. Determine the mass of the dried test portion to the nearest 0,001 g. 7.4 Number of determinations Carry out two determinations on the same test sample. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:01 GMT+00:0
24、0 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 2 BSI 12-1999 8 Expression of results The moisture content or loss in mass at 103 C, expressed as a percentage by mass of the sample, is given by the formula where Take as the result the arithmetic mean of the two determinations, provided that the re
25、quirement for repeatability (see 9.1) is satisfied. 9 Precision 9.1 Repeatability For a moisture content within the range of 3 % (m/m) to 4 % (m/m), the difference between the values of two determinations, carried out in rapid succession (or simultaneously) by the same operator using the same appara
26、tus on the same test sample, shall not exceed 0,2 % (absolute value). 9.2 Reproducibility For a moisture content within the range of 3 % (m/m) to 4 % (m/m), the difference between the values of the final result obtained by two laboratories using this method for the analysis of the same laboratory sa
27、mple, shall not exceed 0,8 % (absolute value). 10 Test report The test report shall specify the method used and the result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may hav
28、e influenced the result. The test report shall include all information necessary for the complete identification of the sample. m0is the initial mass, in grams, of the test portion (7.2); m1is the mass, in grams, of the dried test portion (7.3). m0m1 m0 -100 Licensed Copy: sheffieldun sheffieldun, n
29、a, Wed Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3:1990 BSI 12-1999 Publication(s) referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-3: 1990 ISO 7513:1990 BSI 389 Chiswick Hig
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