BS 5272-1975 Method for simultaneous routine determination of the water contents of a batch of dried milk samples《成批奶粉试样水含量的同步程序测定方法》.pdf

1、BRITISH STANDARD BS 5272:1975 Method for Simultaneous routine determination of the water contents of a batch of dried milk samples UDC 637.143:543.812.2BS5272:1975 This British Standard, having been approved by the DairyingIndustry Standards Committee, was published underthe authority of the Executi

2、ve Board on 30September1975 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 wa

3、s 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 wit

4、h the preparation of this British Standard: Chemical Society National Farmers Union Commonwealth Bureau of Dairy Science and National Institute for Research in Dairying* Technology Office of the High Commissioner for Australia* Dairy Trade Federation* Office of the High Commissioner for Department o

5、f Health and Social Security New Zealand Process Plant Association* Department of Industry, Laboratory of the Royal Association of British Dairy Farmers* Government Chemist* Royal Society of Health Institute of Food Science and Technology Scottish Milk Marketing Board Milk Marketing Board* Scottish

6、Milk Trade Federation Milk Marketing Board for Northern Ireland* Society of Chemical Industry Milking Machine Manufacturers Association Society of Dairy Technology* Ministry of Agriculture, Fisheries and Food* United Kingdom Dairy Association* National Association of Creamery Proprietors West of Sco

7、tland Agricultural College and Wholesale Dairymen* Association of Condensed Milk Manufacturers Ice Cream Federation Ltd. Association of British Manufacturers of Milk Intervention Board for Agricultural Produce Powder Joint Committee of the Milk Marketing Board Association of Butter Makers, Blenders

8、and and the Dairy Trade Federation Packers London Provision Exchange Association of Public Analysts Ministry of Agriculture, Government of British Food Manufacturing Industries Northern Ireland Research Association Society for Analytical Chemistry British Paper and Board Industry Federation Universi

9、ty of Reading Hannah Research Institute Co-opted expert Amendments issued since publication Amd. No. Date of issue CommentsBS5272:1975 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definition 1 4 Principle 1 5 Apparatus 1 6 Laborator

10、y samples 1 7 Procedure 1 8 Expression of results 2 9 Test report 2 Figure 1 Suitable dish and lid 1 Publications referred to Inside back coverBS5272:1975 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 A

11、gricultural Produce. The method described is not intended to supersede the reference method for moisture content described in BS1743 “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

12、 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.

13、Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 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 insid

14、e front cover.BS5272:1975 BSI 12-1999 1 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 than16samples tested concurrently by the same operator. 2 References The titles of the Bri

15、tish 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

16、 Weighed test portions are heated for3h in an oven under controlled conditions at102.5 0.5 C. The losses in mass are determined. 5 Apparatus Use the following apparatus. 5.1 Analytical balance, capable of weighing to0.1mg. 5.2 Desiccators, 200mm in diameter, of heat-resisting glass, plain type, or v

17、acuum 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 approximately1h before each series of determinations with approximately200g of self-indicating silica gel, of

18、the size designation traded as “6to20mesh”, previously dried overnight at102.5 0.5 C. 5.3 Dishes, nickel or stainless steel, approximately75mm in diameter, approximately20mm deep, with flat, readily removable but close-fitting lids. Each dish and its lid should be die-stamped with an identifying num

19、ber. Figure 1 illustrates a suitable dish and lid. 5.4 Thermometer, B110/Total, complying with the requirements of BS593. 5.5 Oven, capable of being maintained at102.5 0.5 C and complying with the requirements of BS2648. The oven shall be fitted with a fan and with the thermometer (5.4) so that the

20、unshielded bulb is as near as possible to the centre of the working space and approximately3cm above the shelf on which the dishes will rest. The ventilation ports shall be fully open and the ventilation rate shall be not less than800litres/h. 6 Laboratory samples On receipt the sample containers sh

21、ould be approximately three-quarters full 1)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 inver

22、ting the container. 7 Procedure 7.1 Check that the oven is maintaining a temperature of102.5 0.5 C. Throughout the procedure keep to a minimum the time for which the oven door is open. Place16clean, empty dishes, standing on their corresponding lids, in the oven and leave them for at least1h. Figure

23、 1 Suitable dish and lid 1) Samples taken as described in BS809will comply with this requirement.BS5272:1975 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 second

24、s 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 of10min. 7.3 Ensure that the balance pan is clean. C

25、heck 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

26、balance pan. Immediately replace the desiccator lid. Weigh the dish with its lid to the nearest0.1mg. NOTEA useful aid to rapid weighing is a list of the approximate masses of the empty dishes with their lids. 7.5 Transfer approximately1g of a well mixed sample to the dish, cover with the lid and we

27、igh rapidly to0.1mg. 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 within10min. Check the balance zero before each empty dish and lid is

28、weighed. Continue similarly with the set of four dishes in each of the three other desiccators in turn, at intervals of10min. 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 in7.2 and7.5 ensu

29、res that each set of four dishes cools in a desiccator for30min before the test portions are weighed out. 7.6 With the oven fan at rest place the16dishes, 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 temperatur

30、e again reaches102.5 0.5 C. After3h, 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 in7.2. Close the oven door and switch the fan on. Similarly remove the other three sets of four dishes at in

31、tervals of5min. 7.7 Again check the balance for level and zero. When the first set of four dishes has been in the desiccator for30min, 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 cove

32、red dish to the balance and weigh the dish as quickly as possible to the nearest0.1mg. Proceed similarly with the three other dishes in the desiccator, following the same sequence as in7.5. Check the balance zero between each weighing. Repeat the procedure with the three other sets of four dishes in

33、 turn, at intervals of5min. 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

34、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.BS5272); e) date of testing. W is the water content; m 1 is the mass of the empty dish and lid(7.4); m 2 is the mass of the dish,

35、 lid and test portion(7.5); m 3 is the mass of the dish, lid and dried test portion (7.7). Express each result to the nearest0.1%. W 100 m 2 m 3 () m 2 m 1 () - =BS5272:1975 BSI 12-1999 Publications referred to This standard makes reference to the following British Standards: BS 593, Laboratory ther

36、mometers. BS 809, Methods for sampling milk and milk products. BS 2648, Performance requirements for electrically-heated laboratory drying ovens. BS 5272:1975 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing Britis

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