1、BRITISH STANDARD BS1742-4: 1991 Methods for Chemical analysis of condensed milks Part4: Determination of ash from condensed milksBS1742-4:1991 This British Standard, having been prepared under the directionof the Agriculture andFood Standards Policy Committee, was published underthe authority of the
2、 Standards Board and comes into effect on 28June1991 BSI10-1999 The following BSI references relate to the work on this standard: Committee reference AFC/3 Draft for comment89/51962 DC ISBN 0 580 19652 6 Committees responsible for this British Standard The preparation of this British Standard was en
3、trusted by the Agriculture and Food Standards Policy Committee (AFC/-) to Technical Committee AFC/3, upon which the following bodies were represented: Association of British Preserved Milk Manufacturers Association of Public Analysts of Scotland Creamery Proprietors Association Department of Trade a
4、nd Industry (Laboratory of the Government Chemist) Intervention Board for Agricultural Produce Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Milk Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Royal Association of Br
5、itish Dairy Farmers Royal Society of Chemistry Society of Chemical Industry Society of Dairy Technology Amendments issued since publication Amd. No. Date CommentsBS1742-4:1991 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 R
6、eagent 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 1 9 Precision 2 10 Test report 2 Publication(s) referred to Inside back coverBS1742-4:1991 ii BSI 10-1999 Foreword This Part of BS1742 has been prepared under the direction of the Agriculture and Food Standards Policy Committe
7、e. It is a revision of the method described in clause6 of BS1742:1951, which is deleted by amendment. NOTEThis Part should be read in conjunction with Part1 “General introduction, including preparation of samples”, published separately. A British Standard does not purport to include all the necessar
8、y 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, pagesi andii, pages1 and2
9、, 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.BS1742-4:1991 BSI 10-1999 1 1 Scope This Part of BS1742 describes a method for the determinat
10、ion of the ash from condensed 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 BS1742, the following definition applies. ash from condensed milk the quantity of ash as determined under the conditi
11、ons specified in this Part of BS1742 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 Distilled water, complying with grade3 of BS3978. 5 Apparatus Ordinary laboratory apparatus together with the fol
12、lowing. 5.1 Dish, of diameter80mm to95mm, and depth25mm to35mm, of silica or porcelain, or125mL beaker made from heat-resisting glass. 5.2 Muffle furnace, capable of being controlled at525 25 C. 5.3 Desiccator, containing an efficient desiccant. 5.4 Boiling water bath or hot plate, capable of being
13、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 condensed milk to be tested using, where appropriate, the procedure described in BS1742-1. 7 Procedure 7.1 Number
14、of determinations Carry out duplicate determinations using two test portions taken from the same test sample. 7.2 Preparation of the dish Heat the dish or beaker(5.1) for1h in the muffle furnace(5.2) controlled at525 25 C. Cool in the desiccator(5.3) for at least1h. After cooling, weigh to the neare
15、st0.0001g. 7.3 Test portion Transfer about5g of the test sample (see clause6) into the prepared dish and weigh to the nearest0.0001g. 7.4 Determination Carefully evaporate the condensed milk to dryness using, for example, the boiling water bath or hot plate(5.4) or a low bunsen flame. Char the resid
16、ue, avoiding incandescence, by using, for example, the infra-red lamp or hot plate(5.5), until smoke is no longer driven off. The test sample may swell considerably during the charring process and it is necessary to keep it under observation, and to remove the dish or beaker from the heat source if
17、the test sample shows evidence of impending swelling over the sides. Transfer the dish or beaker to the muffle furnace, controlled at525 25 C, until the ash is grey or white. Remove from the furnace and allow to cool. Moisten the ash with a few drops of water(4.1), evaporate to dryness as described
18、above and then heat for1h in the muffle 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 or beaker to cool in the desiccator and weigh. Heat the dish or beaker again in the fur
19、nace 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 percentage by mass, using the following expression: where m 0is the
20、mass of the dish or beaker (in g); m 1is the mass of the dish or beaker and the test portion (in g); m 2is the mass of the dish or beaker and the ash (in g). m 2 m 0 m 1 m 0 -100 BS1742-4:1991 2 BSI 10-1999 Take as the result the arithmetic mean of the results of two determinations, provided that th
21、e requirement for repeatability (see9.1) is satisfied. Express the result to two decimal places. 9 Precision NOTEThe precision data were obtained from a collaborative study undertaken in1991 involving nine laboratories and two sweetened and two unsweetened condensed milks. 9.1 Repeatability The diff
22、erence between the values obtained from two determinations carried out simultaneously or in rapid succession by the same analyst using the same apparatus should not exceed0.10% (m/m). 9.2 Reproducibility The difference between the results obtained on samples of the same test material by two differen
23、t analysts in different laboratories (where each result is the mean of two values that comply with the repeatability requirement) should not exceed0.17% (m/m). 10 Test report The test report shall be in accordance BS1742-1.BS1742-4:1991 BSI 10-1999 Publication(s) referred to BS1742, Methods for chem
24、ical analysis of condensed milk. BS1742-1, General introduction, including preparation of test samples. BS3978, Specification for water for laboratory use. BS1742-4: 1991 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for prep
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