1、BRITISH STANDARD CONFIRMED OCTOBER 1997 BS 6986-2: 1988 ISO 6770:1982 Analysis of instant tea Part 2: Methods for determination of free-flow and compacted bulk densities ISO title: Instant tea Determination of free-flow and compacted bulk densities UDC 663.95:620.168.33BS6986-2:1988 This British Sta
2、ndard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes intoeffecton 31August1988 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference FAC/8 Draft for comm
3、ent 81/51653 DC ISBN 0 580 16724 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Food and Agriculture Standards Committee (FAC/-) to Technical Committee FAC/8, upon which the following bodies were represented: Department of Trade and I
4、ndustry (Laboratory of the Government Chemist) Ministry of Agriculture, Fisheries and Food Overseas Development Natural Resources Institute Paper Sack Development Association Ltd. Tea Producers Association United Kingdom Tea Association Amendments issued since publication Amd. No. Date of issue Comm
5、entsBS6986-2:1988 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 Reference 1 Section 1. Determination of free-flow bulk density 3 Definition 2 4 Principle 2 5 Apparatus 2 6 Sampling 2 7 Procedure 2 8 Ex
6、pression of results 2 9 Test report 2 Section 2. Determination of compacted bulk density 10 Definition 3 11 Principle 3 12 Apparatus 3 13 Sampling 3 14 Procedure 3 15 Expression of results 3 16 Test report 4 Figure 1 Apparatus for determining free-flow bulk density 5 Figure 2 Jogging volumeter 6 Pub
7、lication referred to Inside back coverBS6986-2:1988 ii BSI 12-1999 National foreword This Part of BS6986 has been prepared under the direction of the Food and Agriculture Standards Committee. It implements an agreement, to which the UK was a party, reached in Subcommittee8, Tea, of Technical Committ
8、ee34, Agricultural food products, of the International Organization for Standardization(ISO). The UK also provides the secretariat for the Subcommittee. This Part of BS6986 is identical with ISO6770:1982 “Instant tea Determination of free-flow and compacted bulk densities”. Terminology and conventio
9、ns. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. Wherever the words “Inter
10、national Standard” appear, referring to this standard, they should be read as “Part of BS6986”. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. The symbol “ml” has been used to denote millilitre. In B
11、ritish Standards it is current practice to use the symbol “mL”. 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 a British Standard does not of itself confer immunity f
12、rom legal obligations. Cross-reference International Standard Corresponding British Standard ISO 787-11:1981 BS 3483 Methods for testing pigments for paints Part B10:1982 Determination of tamped volume and apparent density after tamping (Identical) Summary of pages This document comprises a front co
13、ver, an inside front cover, pages i and ii, pages1 to 6, 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.BS6986-2:1988 BSI 12-1999 1 0 Introduc
14、tion A knowledge of the bulk density of instant tea is essential to trade in that commodity for it determines the volume occupied by a given mass and hence is an important factor in filling jars correctly for retail sale, and for controlling the mass of instant tea delivered from vending machines. B
15、ulk density is defined as the ratio of mass to volume. The volume of a given sample of instant tea varies according to its history of handling, due to compaction (reversible) and powder breakdown (irreversible) effects. Bulk densities can be expressed in two ways: free-flow (or uncompacted) density
16、and tapped (or compacted) density. Instant tea is fragile and subject to irreversible powder breakdown effects which may occur with repetitive determination of compacted bulk density. Because both densities (and in particular the compacted density) depend so critically on the methods used for handli
17、ng, it is particularly important that the methods adopted for their measurement be as simple and as little dependent on the human factor as possible. It is also important that any mechanical apparatus needed is standardized, cheap, and easily available throughout those parts of the world where insta
18、nt tea is produced or sold. 1 Scope and field of application This International Standard specifies two methods for the determination of the bulk density of instant tea: a) free-flow bulk density (section1); b) compacted bulk density (section2). 2 Reference ISO 787-11, General methods of test for pig
19、ments and extenders Part11: Determination of tamped volume and apparent density after tamping. BS6986-2:1988 2 BSI 12-1999 Section 1. Determination of free-flow bulk density 3 Definition free-flow bulk density (of instant tea) the ratio of the mass of instant tea to the volume it occupies after it h
20、as been tipped freely into a container under specified conditions it is expressed in grams per millilitre(g/ml) 4 Principle Pouring a sample from a specified funnel into a specified receptacle of known volume, and weighing the contents of the receptacle. 5 Apparatus 5.1 Balance, capable of weighing
21、to the nearest0,1g. 5.2 Apparatus for determination of free-flow bulk density, having the dimensions shown inFigure 1, and consisting of: 5.2.1 Firmly mounted funnel, fitted with a slide. 5.2.2 Removable, spoutless measuring receptacle The capacity to the brim shall be known to the nearest millilitr
22、e. NOTEThose parts of the apparatus which may come into contact with the sample shall be made of stainless steel. 5.3 Spatula, approximately120mm 20mm, or other suitable scraper. 6 Sampling 6.1 Carefully take three test samples from the top, middle and bottom of the bulk sample and store them in rig
23、id containers. Samples shall never be kept in plastic bags where they are vulnerable to compression. 6.2 Turn the jars carefully to check for lumps. The samples shall not be worked, since this can alter their characteristics. 7 Procedure 7.1 Weigh the measuring receptacle(5.2.2) to the nearest0,1g.
24、With the slide closed, pour into the funnel(5.2.1) a quantity of one of the samples of instant tea such that it is greater than that needed to fill the measuring receptacle. Fully open the slide of the funnel so that the contents discharge into the measuring receptacle in6to12s. NOTEIf the sample do
25、es not flow freely, keep the outlet clear by inserting a rod of diameter3 to4mm into the opening. When the receptacle is overflowing, close the slide of the funnel and level off the surplus powder using a single stroke with the spatula or other suitable scraper(5.3). Avoid accidental tapping or vibr
26、ation of the filled measuring receptacle. Remove the measuring receptacle from below the funnel and weigh it and its contents to the nearest0,1g. Subtract the mass of the measuring receptacle to obtain the mass of sample it contains. 7.2 Carry out two separate determinations, in rapid succession, on
27、 duplicate portions of the same test sample and repeat these determinations on the other two test samples(6.1). 8 Expression of results 8.1 Method of calculation and formula The free-flow bulk density, expressed in grams per millilitre, is equal to where m is the mass, in grams, of sample contained
28、by the measuring receptacle(see7.1); V is the capacity, in millilitres, to the brim, of the measuring receptacle. Take as the result the arithmetic mean of the values obtained in the two separate determinations(7.2) on each test sample, provided that the requirement for repeatability (see8.2) is sat
29、isfied. Record separately the result obtained for each of the three test samples taken from the bulk sample. 8.2 Repeatability The difference between the values obtained in the two separate determinations(7.2), carried out in rapid succession by the same operator on the same test sample, shall not e
30、xceed2% of the mean. 9 Test report The test report shall show the method used and the results obtained. It shall also mention any operating details not specified in this International Standard or regarded as optional, as well as any circumstances that may have influenced the result. It shall note, i
31、n particular, any lumps observed in the samples. The test report shall include all the information necessary for the complete identification of the bulk sample. m V -BS6986-2:1988 BSI 12-1999 3 Section 2. Determination of compacted bulk density 10 Definition compacted bulk density (of instant tea) t
32、he ratio of the mass of instant tea to the volume it occupies after it has been subjected to a number of taps (usually100) under specified conditions it is expressed in grams per millilitre (g/ml) 11 Principle Determination of the volume of a given mass of instant tea after a fixed number of taps (u
33、sually100) in a jogging volumeter. 12 Apparatus 12.1 Balance, capable of weighing to the nearest0,1g. 12.2 Powder funnel, of stainless steel or other suitable material. 12.3 Jogging volumeter, as described in ISO787-11 (see alsoFigure 2), comprising: 12.3.1 Graduated measuring cylinder, made of glas
34、s, of capacity250ml, having a mass of220 40g, and graduated at every2ml. NOTEIf convenient, a measuring cylinder of different mass may be used provided that the total mass of the cylinder and holder(12.3.2) is670 45g. 12.3.2 Holder, for the measuring cylinder(12.3.1), with a shaft, and of mass450 5g
35、. 12.3.3 Cam, which lifts the shaft pestle and measuring cylinder once per revolution and has a frequency of rotation of250 15min 1 . 12.3.4 Anvil, on which the raised shaft falls from a height of3 0,1mm. 12.3.5 Revolution counter, to count the number of revolutions of the cam. 12.3.6 Sleeve, to gui
36、de the shaft, constructed of a suitable material to give minimum friction. NOTEThe apparatus should be so constructed that, without undue free play, the friction between the shaft and the sleeve is as low as possible without the use of a lubricant. 13 Sampling 13.1 Carefully take three test samples
37、from the top, middle and bottom of the bulk sample and store them in rigid containers. Samples shall never be kept in plastic bags where they are vulnerable to compression. 13.2 Turn the jars carefully to check for lumps. The samples shall not be worked, since this can alter their characteristics. 1
38、4 Procedure 14.1 Set the jogging volumeter(12.3) to give100taps and weigh the measuring cylinder(12.3.1) to the nearest0,1g. By means of the powder funnel(12.2) 1) , transfer about150ml of one of the samples to the cylinder. Weigh the cylinder and its contents, and subtract the mass of the cylinder
39、to obtain the mass of sample it contains. Fit the cylinder to the jogging volumeter with the holder(12.3.2). Allow the volumeter to tap100times. Read the volume of the powder on the cylinder graduations to the nearest2ml. 14.2 Carry out two separate determinations, in rapid succession, on duplicate
40、portions of the same test sample and repeat these determinations on the other two test samples(13.1). 14.3 In cases where there are doubts about powder fragility, the volume may be determined after a number of50tap sequences to establish whether there is a limiting minimum volume, or whether the vol
41、ume diminishes continuously. In the latter case, record all the volumes measured. By agreement between the interested parties, the compacted bulk density may be recorded as that derived from the volume after the first100taps. 15 Expression of results 15.1 Method of calculation and formula The compac
42、ted bulk density, expressed in grams per millilitre, is equal to where m is the mass, in grams, of sample in the measuring cylinder; V is the volume, in millilitres, occupied by the sample after compaction. Take as the result the arithmetic mean of the values obtained in the two separate determinati
43、ons(14.2) on each test sample, provided that the requirement for repeatability(see15.2) is satisfied. Record separately the result obtained for each of the three test samples taken from the bulk sample. 15.2 Repeatability The difference between the values obtained in the two separate determinations(
44、14.2), carried out in rapid succession by the same operator on the same test sample, shall not exceed2% of the mean. 1) It is possible that filling the cylinder through a powder funnel may influence the results; some experimentalists maintain that the powder should be poured directly from the sample
45、 jar into the cylinder. m V -BS6986-2:1988 4 BSI 12-1999 16 Test report The test report shall show the method used and the results obtained. It shall also mention any operating details not specified in this International Standard or regarded as optional, as well as any circumstances that may have in
46、fluenced the result. It shall note, in particular, any lumps observed in the samples. The test report shall include all the information necessary for the complete identification of the bulk sample.BS6986-2:1988 BSI 12-1999 5 Figure 1 Apparatus for determining free-flow bulk densityBS6986-2:1988 6 BS
47、I 12-1999 Figure 2 Jogging volumeterBS6986-2:1988 BSI 12-1999 Publication referred to See national foreword.BS 6986-2: 1988 ISO 6770:1982 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presen
48、ts the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to
49、 improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications
