BS-5272-1975.pdf

BRITISH STANDARD BS 5272:1975 Method for Simultaneous routine determination of the water contents of a batch of dried milk samples UDC 637.143:543.812.2 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 This British Standard, having been approved by the Dairying Industry Standards Committee, was published under the authority of the Executive Board on 30 September 1975 © BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference DAFA/3 Draft for comment 74/53973 DC ISBN 0 580 08877 4 Co-operating organizations The Dairying Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government departments and organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Chemical SocietyNational Farmers Union Commonwealth Bureau of Dairy Science andNational Institute for Research in Dairying* TechnologyOffice of the High Commissioner for Australia* Dairy Trade Federation*Office of the High Commissioner for Department of Health and Social SecurityNew Zealand Process Plant Association* Department of Industry, Laboratory of theRoyal Association of British Dairy Farmers* Government Chemist*Royal Society of Health Institute of Food Science and TechnologyScottish Milk Marketing Board Milk Marketing Board*Scottish Milk Trade Federation Milk Marketing Board for Northern Ireland*Society of Chemical Industry Milking Machine Manufacturers AssociationSociety of Dairy Technology* Ministry of Agriculture, Fisheries and Food*United Kingdom Dairy Association* National Association of Creamery ProprietorsWest of Scotland Agricultural College and Wholesale Dairymen* Association of Condensed Milk ManufacturersIce Cream Federation Ltd. Association of British Manufacturers of MilkIntervention Board for Agricultural Produce PowderJoint Committee of the Milk Marketing Board Association of Butter Makers, Blenders andand the Dairy Trade Federation PackersLondon Provision Exchange Association of Public AnalystsMinistry of Agriculture, Government of British Food Manufacturing IndustriesNorthern Ireland Research AssociationSociety for Analytical Chemistry British Paper and Board Industry FederationUniversity of Reading Hannah Research InstituteCo-opted expert Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 © BSI 12-1999i Contents Page Co-operating organizationsInside front cover Forewordii 1Scope1 2References1 3Definition1 4Principle1 5Apparatus1 6Laboratory samples1 7Procedure1 8Expression of results2 9Test report2 Figure 1 Suitable dish and lid1 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 ii © BSI 12-1999 Foreword This British Standard has been prepared at the request of manufacturers of dried milk and of the Intervention Board for Agricultural Produce. The method described is not intended to supersede the reference method for moisture content described in BS 1743 “Methods for the chemical analysis of dried milk”, but has been prepared specifically to meet a current need for a routine method by which large numbers of samples may be reliably examined for water content. 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 from legal obligations. Summary of pages This document comprises a front cover, an inside 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, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 © BSI 12-19991 1 Scope This British Standard specifies a routine method for the determination of the water content of dried milk when single determinations are made on each of not more than 16 samples tested concurrently by the same operator. 2 References The titles of the British Standards referred to in this standard are listed on the inside back cover. 3 Definition For the purposes of this British Standard the following definition applies. water content the loss in mass obtained by the procedure described. Water content is expressed as a percentage by mass 4 Principle Weighed test portions are heated for 3 h in an oven under controlled conditions at 102.5 ± 0.5 °C. The losses in mass are determined. 5 Apparatus Use the following apparatus. 5.1 Analytical balance, capable of weighing to 0.1 mg. 5.2 Desiccators, 200 mm in diameter, of heat-resisting glass, plain type, or vacuum type with a tap. Before putting new desiccators into use, degrease the metal tray, remove any rubber sealing rings and grease the ground glass surfaces. Desiccators shall be recharged approximately 1 h before each series of determinations with approximately 200 g of self-indicating silica gel, of the size designation traded as “6 to 20 mesh”, previously dried overnight at 102.5 ± 0.5 °C. 5.3 Dishes, nickel or stainless steel, approximately 75 mm in diameter, approximately 20 mm deep, with flat, readily removable but close-fitting lids. Each dish and its lid should be die-stamped with an identifying number. Figure 1 illustrates a suitable dish and lid. 5.4 Thermometer, B110/Total, complying with the requirements of BS 593. 5.5 Oven, capable of being maintained at 102.5 ± 0.5 °C and complying with the requirements of BS 2648. The oven shall be fitted with a fan and with the thermometer (5.4) so that the unshielded bulb is as near as possible to the centre of the working space and approximately 3 cm above the shelf on which the dishes will rest. The ventilation ports shall be fully open and the ventilation rate shall be not less than 800 litres/h. 6 Laboratory samples On receipt the sample containers should be approximately three-quarters full1) and should have their airtight lids securely fixed. Note and report any sample which does not comply with these requirements. Immediately before any part of a sample is withdrawn for water determination, thoroughly mix the whole sample by shaking and inverting the container. 7 Procedure 7.1 Check that the oven is maintaining a temperature of 102.5 ± 0.5 °C. Throughout the procedure keep to a minimum the time for which the oven door is open. Place 16 clean, empty dishes, standing on their corresponding lids, in the oven and leave them for at least 1 h. Figure 1 Suitable dish and lid 1) Samples taken as described in BS 809 will comply with this requirement. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 2 © BSI 12-1999 7.2 Transfer four dishes, standing on their upturned lids, to a desiccator. If a vacuum type desiccator is used, immediately replace its lid with the tap open, wait a few seconds and close the tap. If a plain desiccator is used, replace its lid leaving a small air gap and after a few seconds close the lid by a sliding motion. Similarly transfer the other dishes and lids, in sets of four, to other desiccators at intervals of 10 min. 7.3 Ensure that the balance pan is clean. Check the balance for level, zero and scale sensitivity. 7.4 30 min after the transfer of the first set of four dishes to the desiccator, slowly open then close the tap (if a vacuum type desiccator is used), carefully slide open the lid and transfer a dish, still standing on its upturned lid, to the balance pan. Immediately replace the desiccator lid. Weigh the dish with its lid to the nearest 0.1 mg. NOTEA useful aid to rapid weighing is a list of the approximate masses of the empty dishes with their lids. 7.5 Transfer approximately 1 g of a well mixed sample to the dish, cover with the lid and weigh rapidly to 0.1 mg. Replace the lid of the sample container whilst the balance is settling to its final position. Proceed similarly with the other dishes in the desiccator and three further samples, completing the four weighings within 10 min. Check the balance zero before each empty dish and lid is weighed. Continue similarly with the set of four dishes in each of the three other desiccators in turn, at intervals of 10 min. Remove the lid from each dish in turn, carefully tap the base to spread the dried milk evenly and stand the dish on its own lid. NOTEThe procedure described in 7.2 and 7.5 ensures that each set of four dishes cools in a desiccator for 30 min before the test portions are weighed out. 7.6 With the oven fan at rest place the 16 dishes, standing on their own lids, on the oven shelf immediately below the thermometer bulb. Switch the fan on and note the time at which the temperature again reaches 102.5 ± 0.5 °C. After 3 h, switch the oven fan off, transfer four dishes covered with their lids to a desiccator and immediately replace the lid, closing the desiccator as described in 7.2. Close the oven door and switch the fan on. Similarly remove the other three sets of four dishes at intervals of 5 min. 7.7 Again check the balance for level and zero. When the first set of four dishes has been in the desiccator for 30 min, slowly open then close the tap (if a vacuum type desiccator is used), carefully slide open the lid and momentarily remove the desiccator lid. Transfer the first covered dish to the balance and weigh the dish as quickly as possible to the nearest 0.1 mg. Proceed similarly with the three other dishes in the desiccator, following the same sequence as in 7.5. Check the balance zero between each weighing. Repeat the procedure with the three other sets of four dishes in turn, at intervals of 5 min. 8 Expression of results Calculate the water content for each sample as a percentage (m/m), using the following formula: where 9 Test report Include the following items in the test report for each sample: a) the result; b) the full identification; c) any abnormality noted in the sample, in particular, whether the sample container was overfilled or underfilled, or appeared not to be adequately sealed; d) reference to the method of test (i.e. BS 5272); e) date of testing. W is the water content; m1is the mass of the empty dish and lid (7.4); m2is the mass of the dish, lid and test portion (7.5); m3is the mass of the dish, lid and dried test portion (7.7). Express each result to the nearest 0.1 %. W100 m2m3() m2m1() - -= Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 © BSI 12-1999 Publications referred to This standard makes reference to the following British Standards: BS 593, Laboratory thermometers. BS 809, Methods for sampling milk and milk products. BS 2648, Performance requirements for electrically-heated laboratory drying ovens. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 14:53:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5272:1975 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 the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. 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