1、BRITISH STANDARD BS 1741-9: 1988 Methods for Chemical analysis of liquid milk and cream Part9: Determination of ash from liquid milk UDC 637.12+637.148.074:543BS1741-9:1988 This British Standard, havingbeen prepared under thedirection of the Dairying Standards Committee, was published under the auth
2、ority ofthe Board of BSI and comes intoeffect on 29February1988 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 86/52565 DC ISBN 0 580 16391 1 Committees responsible for this British Standard The preparation of this British St
3、andard was entrusted by the Dairying Standards Committee (DAC/-) to Technical Committee DAC/3, upon which the following bodies were represented: AFRC Institute of Food Research, Reading Laboratory Association of British Preserved Milk Manufacturers Association of Public Analysts Association of Publi
4、c Analysts of Scotland Creamery Proprietors Association Dairy Trade Federation Department of Trade and Industry (Laboratory of the Government Chemist) Ice Cream Alliance Limited Intervention Board for Agricultural Produce Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Mil
5、k Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Royal Association of British Dairy Farmers Royal Society of Chemistry Society of Chemical Industry Society of Dairy Technology Amendments issued since publication Amd. No. Date of issue CommentsBS
6、1741-9:1988 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagent 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 1 9 Precision 1 10 Test report 2 Publications referred to Inside back coverBS1741-9:1988 i
7、i BSI 10-1999 Foreword This Part of BS1741 has been prepared under the direction of the Dairying Standards Committee. It is a revision of the method described in clause11 of BS1741:1963, which is deleted by amendment. NOTEThis Part should be read in conjunction with Part1 “General introduction inclu
8、ding preparation of samples”, published separately. 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 ob
9、ligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and2, 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 t
10、he inside front cover.BS1741-9:1988 BSI 10-1999 1 1 Scope This Part of BS1741 describes a method for the determination of the ash from liquid milk. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this Part of BS174
11、1, the following definition applies. ash from liquid milk the quantity of ash as determined under the conditions specified in this Part of BS1741 and expressed as a percentage by mass of the sample 3 Principle The organic matter is destroyed by heating at525 25 C to constant mass. 4 Reagent 4.1 Dist
12、illed water, complying with grade3 of BS3978. 5 Apparatus Ordinary laboratory apparatus together with the following. 5.1 Dish, of diameter50mm to60mm, of silica, platinum or other material unaffected by the conditions of the test. 5.2 Muffle furnace, capable of being controlled at525 25 C. 5.3 Desic
13、cator, containing an efficient desiccant. 5.4 Water bath or hot plate, capable of being controlled at about100 C. 5.5 Infra-red lamp or hot plate, capable of operating at about300 C. 5.6 Balance, capable of weighing to0.0001g. 6 Sampling Take a representative sample of the liquid milk to be tested u
14、sing, where appropriate, the procedures described in BS1741-1. 7 Procedure 7.1 Number of determinations Carry out duplicate determinations on two test portions taken from the same test sample. 7.2 Preparation of the dish Heat the dish(5.1) for1h in the furnace(5.2) controlled at525 25 C. Cool in the
15、 desiccator(5.3) for at least1h. After cooling, weigh to the nearest0.001g. 7.3 Test portion Transfer about10mL of the test sample (seeclause6) into the prepared dish, and weigh to the nearest0.001g. 7.4 Determination Carefully evaporate the milk to dryness using for example the hot-plate or boiling
16、 water bath(5.4) on a low bunsen flame. Char the residue, avoiding incandescence, by using for example the infra-red lamp or hot-plate(5.5), until smoke is no longer given off. Transfer the dish to the furnace(5.2), controlled at525 25 C, until the ash is grey. Remove from the furnace and allow to c
17、ool. Moisten the ash with a few drops of water(4.1), evaporate to dryness as described above and then heat for1h in the furnace controlled at525 25 C. (If necessary, repeat the moistening, evaporation and heating until the ash is white and visibly free from carbon particles.) Allow the dish to cool
18、in the desiccator and weigh. Heat the dish again in the furnace for30min, cool and weigh. Repeat these operations, if necessary, until the difference between two successive weighings does not exceed0.001g. 8 Expression of results Calculate the ash yielded by the test sample, expressed as a percentag
19、e by mass, using the following expression: Take as the result the arithmetic mean of the results of two determinations, provided that the requirement for repeatability (see9.1) is satisfied. Express the result correct to two decimal places. 9 Precision NOTEThe precision data were obtained from a col
20、laborative study undertaken in1986 and involving twelve laboratories and three milks (skimmed, semi-skimmed and full fat). 9.1 Repeatability The difference between the values obtained from two determinations carried out simultaneously or in rapid succession by the same analyst using the same apparat
21、us shall not exceed0.03%(m/m). where m 0 is the mass of the dish (ing); m 1 is the mass of the dish and the test portion (ing); m 2 is the mass of the dish and the ash (ing). m 2 m 0 m 1 m 0 -100 BS1741-9:1988 2 BSI 10-1999 9.2 Reproducibility The difference between the results obtained on samples o
22、f the same test material by two different analysts in different laboratories (where each result is the mean of two values that comply with the repeatability requirement) should not exceed0.07%(m/m). 10 Test report The test report shall be in accordance with BS1741-1.BS1741-9:1988 BSI 10-1999 Publica
23、tions referred to BS1741, Methods for chemical analysis of liquid milk and cream. BS1741-1, General introduction including preparation of samples. BS3978, Specification for water for laboratory use. BS 1741-9: 1988 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the in
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