BS 6049-9-1999 Methods of test for tea - Determination of crude fibre content《茶叶的试验方法 粗纤维含量的测定》.pdf

1、STDOBSI BS b049-9-ENGL 1999 H Lb24bb9 0809373 q52 BRITISH STANDARD Methods of test for tea - Part 9: Determination of crude fibre content ICs 67.140.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS 6049-9: 1999 IS0 155981999 U- STD-BSI BS b049-9-ENGL 1779 1b24bbl 0809174

2、379 direction of the Consumer Amd.No. Products and Services Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 September 1999 O BSI 09-1999 BS 6049-9:1999 Date Comments National foreword This British Standard reproduces verbatim IS0 15598: 1999

3、 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AWB, Tea, which has the responsibility to: - aid enquirers to understand the text; - present to the responsible internationaUEuropean commitke any enquiries on the interpretat

4、ion, or proposals for change, and keep the UK interests hfOIllled; - monitor relaed intedonai 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 imple

5、ment international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “Intemational Standards Correspondence Index”, or by using the “Find” faciity of the BSI Standards Electronic Catalogue. A British Standard does not purport

6、 to include all the necemry 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,

7、 the IS0 title page, page ii, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when this document was last issued. ISBN O 580 32759 O INTERNATIONAL STANDARD IS0 15598 First edition 199906-01 Tea - Determination of crude fibre content Th - Dtermination de l

8、indice dinsoluble dit acellulosiqueu Reference number IS0 15598: 1999(E) STD-BSI BS bO47-7-ENGL 1937 m Lb24bb9 080727b LbL W BS 6049-9:1999 Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of prepar

9、ing International Standards is normally carried out through IS0 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 li

10、aison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft Internatio

11、nal 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 IS0 15598 was prepared by Technical Committee ISO/TC 34, Agricultu

12、ral food products, Subcommittee SC 8, Tea. Annex A of this Intemational Standard is for information only. STD.BSI BS h049-ENGL 1999 D 3b2qbb9 O809377 OTA BS 6049-9:1999 Tea - Determination of crude fibre content 1 scope This Intemational Standard specifies a method for the determination of crude fib

13、re content in tea. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However

14、 patties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IS0 and IEC

15、 maintain registers of currently valid International Standards. IS0 15731 980, Tea - Deteminafian of loss in mass at 103 “C. IS0 3696, Water for analytical laboratory use - Specification and test methods. 3 Term and definition For the purposes of this Intemational Standard, the following tem and def

16、inition apply. 3.1 crude fibre content the whole of the substances which are insoluble and combustible under the operating conditions specified in this Intemational Standard NOTE It is expressed as a mass fraction, in percent, of the product on a dry basis formerly expressed as % (dm). 4 Principle T

17、he suitably ground sample is successively treated with boiling sulfuric acid solution and sodium hydroxide solution. The residue is separated by filtration, washed, dried, weighed and then ashed. The loss in mass resulting from ashing is called the crude fibre content. 5 Reagents Use only reagents o

18、f recognized analytical grade. 5.1 Water, complying with grade 3 of IS0 3696. 5.2 Sutfuric acid stock solution, c(%H*S04) = 2,040 rt 0,040 moVI (corresponding to 100 g of sulfuric acid per litre of solution). 1 STDeBSI BS bOqS-S-ENGL 1999 1b24bb7 0807178 TI4 BS 6049-9:1999 Add 275 ml of concentrated

19、 sulfuric acid (p20 = 1,84 mi) to water, cool and dilute to 5 I. CAUTION -Wear gloves and face protection. 5.3 Sulfuric acid working solution, c(1hH$304) = 0,255 i 0,005 moIA (corresponding to 12,5 g of sulfuric acid per litre of solution). Dilute 125 ml of the sulfuric acid stock solution (5.2) to

20、1 I. 5.4 Sodium hydroxide stock solution, c(Na0H) = 2,504 I 0,040 moM (corresponding to 100 g of sodium hydroxide per litre of solution). Dissolve 500 g of sodium hydroxide in water, cool and dilute to 5 I. CAUTION - Wear gloves and face protection. 5.5 Sodium hydroxide working solution, c(Na0H) = 0

21、313 f 0,005 moVI (corresponding to 12.5 g of sodium hydroxide per litre of solution). Dilute 125 ml of the sodium hydroxide stock solution (5.4) to 1 I. 5.6 Octan-1-01, as antifoaming agent. 5.7 Hydrochloric acid, 1 % solution (volume fraction). Dilute 10 ml of concentrated hydrochloric acid (p20 =

22、 1,19 g/ml) to 1 I. CAUTION - Wear gloves and face protection. 5.8 Ethanol, of minimum pur 95 % (volume fraction). 5.9 Acetone. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Laboratory mill, of hammer or centrifugal type, fitted with a 1 mm screen. 6.2 Conical flasks,

23、 of 1 i capacity, with plain neck (or ground glass neck if reflux condensers are to be used). 6.3 Dispenser, capable of dispensing 200 ml of hot liquid. 6.4 Heating unit, equipped for heating a bank of 1 I conical flasks. 6.5 Cold-finger condensers, to fit into the necks of 1 I conical flasks (or re

24、flux condensers if apparatus with ground glass joints is being used). 6.6 Buchner flasks, with rubber adaptors and fitted with Hartley funnels for 123 cm diameter filter paper, plus adaptor funnels for 70 ml sintered-glass crucibles. 6.7 Sintered-glass crucibles, of porosity No. 1 or P 160 (pore siz

25、e 100 pm to 160 pm), of 40 mm plate diameter and 70 mi capacity. 6.8 Oven, fan-assisted, capable of maintaining a temperature of 103 OC f 2 “C. 2 STD.BS1 BS bOY7-7-ENGL 3779 = Lb24bb7 0809379 770 BS 6049-9:1999 6.9 Mutfie furnace, capable of maintaining a temperature of 550 OC f 10 OC. 6.10 esiccato

26、r, containing an efficient desiccant. 6.11 Filter papers, of 12,5 cm diameter, hardened, ashless grade, with a porosity of 20 vm to 25 vm. NOTE Whatman No. 5411) have been found to be suitable. 7 Sampling It is important that the laboratory receive a sample which is truly representative and has not

27、been damaged or changed during transport and storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in IS0 1839. 8 Preparation of test sample Using the mill (6.1), grind the sample to pass through the 1 mm screen. 9 Procedure NOTE

28、 accordance with 9.1 to 9.3 under repeatability conditions. If it is required to check whether the repeatability limit (11.2) is met, carry out two single deteminations in 9.1 Determination of dry matter content Calculate the dry matter content (w) from the moisture content (loss in mass at 103 OC)

29、determined on a portion of the test sample (clause 8) in accordance with IC0 1573. 9.2 Test portion Weigh, to the nearest 0,001 g, 2 g to 3 g of the test sample (clause 8) into a 1 I conical flask (6.2). Record the mass (mo). 9.3 Determination 9.3.1 Using the dispenser (6.3), add to the sample 200 m

30、l of the sulfuric acid working solution (5.3), measured at room temperature and brought to boiling. CAUTION - lake care to avoid splashing the boiling acid. Wear gloves and face protection. 9.3.2 Add two or three drops of the antifoaming agent (5.6), insert the condenser (6.5) into the neck of the f

31、lask, and heat using the heating unit (6.4) to boiling within 2 min. Continue boiling gently for 30 min, rotating the flask occasionally to mix the contents and to remove particles of the sample adhering to the sides. The times given are critical. 9.3.3 Prepare a Buchner flask (6.6) with a Hartley f

32、unnel with a wet filter paper (6.11). 9.3.4 At the end of the boiling period, pour the acid digest into a shallow layer of hot water contained in the funnel under gentle suction. Filtration should be completed within 1 O min. If it is not, repeat the determination using a smaller mass of sample. 1)

33、Whatman No. 541 is an example of a suitable product available commercially. This information is given for the convenience of users of this International Standard and does not constitute an endorsement by IS0 of this product. 3 STD-BSI BS bOi7-7-ENGL L777 lb24bb7 0807180 b72 D BS 6049-9:1999 9.3.5 Ri

34、nse out the flask with two portions of approximately 50ml of boiling water, and pour through the filter funnel. 9.3.6 Using the dispenser (6.3), wash the insoluble matter from the filter paper into the original 1 I conical flask using 200 ml of the working sodium hydroxide solution (5.5), measured a

35、t room temperature and brought to boiling. CAUTION -Take care to avoid splashing the boiling alkali. Wear gloves and face protection. 9.3.7 Add two or three drops of the antifoaming agent (5.6) and boil for 30 min using the same procedure as with the acid treatment (see 9.3.2). The times given are c

36、ritical. 9.3.8 Using boiling water, transfer all the insoluble matter into the sintered glass crucible (6.7) fitted to the Buchner flask by means of an adaptor, applying gentle suction. 9.3.9 Wash the residue successively with approximately 50 ml portions of boiling water, the hydrochloric acid solu

37、tion (5.6) and boiling water again. Finally, wash the residue twice with the ethanol (5.7) and then three times with the acetone (5.8). 9.3.10 Heat the crucible and residue in the oven (6.8) maintained at 103 OC for 2 h. Allow to cool in the desiccator (6.10) and weigh to the nearest 0.001 g: Return

38、 the crucible to the oven and heat again for 1 h. Cool in the desiccator and weigh. Repeat these operations until the difference between successive weighings does not exceed 0,001 g. NOTE It is an acceptable alternative, and it may be more convenient, to heat the crucible and residue overnight. Reco

39、rd the mass (mi). 9.3.11 Place the crucible and residue in the muffle furnace (6.9) maintained at 550 OC for at least 1 h. Allow to cool in the desiccator (6.10) and weigh to the nearest 0,001 g. Record the mass (mp). 10 Calculation The crude fibre content, w, expressed as mass fraction, in percent,

40、 of the sample on a dry basis, is given by the formula: 1 O0 m0 WD w=- mi-m2 XlOOX- where mg is the mass, in grams, of the test portion; mt is the mass, in grams, of the crucible and residue ater drying (9.3.10); m2 is the mass, in grams, of the crucible and residue after heating in the furnace (9.3

41、1 1); WD is the dry matter content, expressed as a mass fraction, in percent, of the test sample (9.1). 11 Precision 1 1.1 Interlaboratory test Details of the interlaboratory test to determine the precision of the method are summarized in annex A. The values derived from this interlaboratory test m

42、ay not be applicable to concentration ranges and matrices other than those given. 4 11.2 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment w

43、ithin a short interval of time, will in not more than 5 % of cases be greater than the repeatability (r) values given in Table A.l. 11.3 Reproducibility The absolute difference beween two single test results, obtained using the same method on identical test material in different laboratories with di

44、fferent operators using different equipment, will in not more than 5 % of cases be greater than the reproducibility (R) values given in Table A.1. 12 Test report The test report shall specify: - all information necessary for the complete identification of the sample; - the sampling method used, if k

45、nown; - the test method used, with reference to this Intemational Standard; - all operating details not specified in this Intemational Standard, or regarded as optional, together with details of any incidents which may have influenced the test result); - the test resul(s) obtained, or, if the repeat

46、ability has been checked, the final quoted result obtained. 5 STDOBSI ES h097-7-ENGL 1757 Lb24bb7 0807182 4b5 BS 6049-9:1999 Number of participating laboratories Number of accepted test results Annex A (informative) 11 11 11 11 Results of interlaboratory test Repeatability standard deviation, s, Rep

47、eatability coefficient of variation, 70 An interlaboratory test, carried out in 1994 under the auspices of the International Organization for Standardization, gave the statistical results (evaluated in accordance with IS0 5725 *) ) shown in Table A.l. Table A.1 - Repeatability and reproducibility va

48、lues 0,4338 0,234 1 1,50 2.42 I I Black tea 0,94 0,599 9 Sample identification 1112 1864 0,430 5 Repeatability limit, r (2,8 x S,) Reproducibility standard deviation, sR Mean crude fibre content, %, dry matter I 28,a I 9,67 1,214 6 0,655 5 1,103 2 0,674 6 Reproducibility coefficient of variation, %

49、Reproducibility limit, R (2,8 x sR) 3,85 6,98 3.089 O 1,888 8 3 11 11 18,95 0,272 0 1,44 0,763 0 1,235 4 3,459 1 415 11 I 11 11 I 11 2) IS0 57251986 (now withdrawn) was used to obtain the precision data. 6 STD-BSI BS bO99-9-ENGL 1997 lb24bb9 0809183 3TL BS 6049-9:1999 Bibliography l IS0 1839:1980, Tea - Sampling. 2 IS0 5725:1986, Precision of test methods - Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. 7 STD*BSI BS b099-9-ENGL BS 6049-9: 1999 IS0 15598:1999 BSI 389 Chiswick High Road London w4 4AL