ISO 7513-1990 Instant tea in solid form determination of moisture content (loss in mass at 103C)《固体状速溶茶 水分含量(在103℃时质量损失)的测定》.pdf

1、INTERNATIONAL STANDARD IS0 7513 First edition 1990-10-01 Instant tea in solid form - Determination of moisture content (loss in mass at 103 “C) TM soluble sous forme solide - LGtermination de la teneur en eau (perte de masse ZI 103 “C) Reference number IS0 7513:1990(E) IS0 7513:1990(E) Foreword IS0

2、(the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical comm

3、ittee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electro

4、technical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an lnter- national Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 7513 was prepared

5、 by Technical Committee ISO/TC 34, AgriculturaI food products. 0 IS0 1990 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. inte

6、rnational Organization for Standardization Case Postaie 56 l CH-1211 Genkve 20 l Switzerland Printed in Switzerland ii IS0 7513:1990(E) 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”

7、, the contribution to this loss in mass made by small amounts of other volatile constituents being regarded as negligible for practical purposes. . . . III This page intentionally left blank - INTERNATIONAL STANDARD IS0 7513:1990(E) Instant tea in solid form - Determination of moisture content (loss

8、 in mass at 103 “C) 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). 4.1 Oven, constant-temperature and fan-assisted, capable of being controlled at 103 “C + 2 “C. - 4.2 Weighing bo

9、ttle or dish, with a close-fitting lid, made of aluminium or glass, approximately 70 mm in diameter and 20 mm in height. 2 Normative reference 4.3 Desiccator, containing an efficient desiccant. The following standard contains provisions which, through reference in this text, constitute provisions of

10、 this International Standard. At the time of publi- cation, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encour- aged to investigate the possibility of applying the most recent edition of the standard indic

11、ated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. 5 Sampling Sampling shall have been carried out in accordance with IS0 7516. NOTE 3 The moisture content of samples is likely to in- crease on exposure to the atmosphere. It is therefore im- portant t

12、o carry out the determination as soon as possible after sampling. IS0 7516:1984, Instant tea in solid form - Sanlpling. 6 Preparation of the test sample 3 Principle Thorougly mix the instant tea sample as received by shaking or inverting the sealed sample container. Heating a test portion of the ins

13、tant tea in an air oven at 103 OC for 2 h and weighing of the dried test portion. 7 Procedure NOTES 7.1 Preparation of the weighing bottle or dish 1 The loss in mass will consist mostly of loss in water content and small amounts of non-water volatile sub- stances that will vaporize under the test co

14、nditions used. 2 A drying period of 2 h is used because this time inter- val gives results which agree best with those obtained using the Karl Fischer method of determining the moisture content of instant tea. Remove the lid from the weighing bottle or dish (4.2) and heat both for 1 h in the oven (4

15、.1) controlled at 103 OC + 2 OC. Cool in the desiccator (4.3). After cooling to Tmrn temperature, fit the lid and weigh to the nearest 0,001 g. 7.2 Test portion 4 Apparatus Usual laboratory apparatus and, in particular, the following. Open the sample container and immediately weigh, to the nearest 0

16、,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. 1 IS0 7513:1990(E) 7.3 Determination Heat the weighing bottle or dish and contents, with the lid removed and placed alongside, in the oven (4.1) at 103 “C + 2 “C f

17、or 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. Remove from the desiccator,

18、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. Take as the result the arithmetic mean of the two determinations, provided that the requirement for repeatability (see 9.1) is satisfied. 9 Precision 9.1 Repeatability For a moistur

19、e 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 oper- ator using the same apparatus on the same test sample, shall not exceed 0,2 % (absolute value). 7.4 Number of determina

20、tions 9.2 Reproducibility Carry t out two determinations on the same test samp le. 8 Expression of results The moisture content or loss in mass at 103 “C, ex- pressed as a percentage by mass of the sample, is given by the formula 4r- m x 100 m, m, is the initial mass, in grams, of the test portion (

21、7.2); ml is the mass, in grams, of the dried test portion (7.3). 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 labora- tories using this method for the analysis of the same laboratory sample, shall not exceed

22、0,8 % (absolute value). 10 Test report The test report shall specify the method used and the result obtained. It shall also mention all operat- ing details not specified in this International Stan- dard, or regarded as optional, together with details of any incidents which may have influenced the re- sult. The test report shall include all information necess- ary for the complete identification of the sample. This page intentionally left blank IS0 7513:1990(E) UDC 663.958.8543.71 Descriptors: food products, tea, tests, determination of content, humidity. Price based on 2 pages