1、BRITISH STANDARD BS 1741-1: 1987 Methods for Chemical analysis of liquid milk and cream Part 1: General introduction including preparation of samples UDC 637.12 + 637.148.074:543BS1741-1:1987 This British Standard, having been prepared under the direction of the Dairying Standards Committee, was pub
2、lished under the authority of the Board of BSI and comes into effect on 30June1987 BSI 06-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 86/52564 DC ISBN 0 580 15960 4 Committees responsible for this British Standard The preparation
3、 of this British Standard 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 A
4、ssociation of Public Analysts of Scotland Creamery Proprietors Association Dairy Trade Federation Department of Trade Part 2: Determination of the total solids content of liquid milk and cream (will implement ISO6731, which is in preparation) 1) ; Part 3: Determination of fat content of liquid milk
5、(implements ISO 1211-1984); Part 4: Determination of fat content of cream (implements ISO 2450-1985); Part 5: Determination of the nitrogen content of liquid milk 1) ; Section 5.1: Reference method; Section 5.2: Routine method; Part 6: Determination of casein nitrogen in liquid milk 1) ; Section 6.1
6、: Reference method; Section 6.2: Routine method; Part 7: Determination of lactose content of liquid milk 1) ; Section 7.1: Reference method; Section 7.2: Routine method; Part 8: Determination of chloride content of liquid milk 1) ; Part 9: Determination of ash from liquid milk 1) ; Part 10: Determin
7、ation of titratable acidity of liquid milk and cream 1) ; Part 11: Detection of detergent and/or disinfectant residues in liquid milk 1) . A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct applicati
8、on. 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, pages1and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and
9、 may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In preparation.BS1741-1:1987 BSI 06-1999 1 1 Scope This Part of BS 1741 gives a general introduction to the methods of analysis of liquid milk and cream and gives general instructions o
10、n sampling and preparation of samples. This Part should be read in conjunction with each of the methods described in other Parts. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Determinations supplementary to those given in BS1741 Reference sho
11、uld be made to the following methods in respect of determinations supplementary to those given in BS1741. 3 Sampling Carry out the sampling in accordance with the methods described in BS809 for liquid milk and cream, as appropriate. 4 Preparation of sample 4.1 Liquid milk Mix the sample of milk thor
12、oughly but gently by repeated inversion of the container, so that the cream layer is completely dispersed without churning of the fat. If there is difficulty in dispersing the cream layer, warm the sample to between30C and40C and mix to disperse the cream. If this is done, cool the sample to room te
13、mperature after mixing; at this stage the physical condition should be satisfactory. Invert the container three or four times immediately before taking an aliquot portion of the milk sample for the determination. 4.2 Cream The preparation of the sample depends upon its physical condition. If the cre
14、am is thin enough at room temperature to pour easily, mix by repeated inversion of the container; if it is too thick to mix by this method, stir gently, being careful to incorporate the top and bottom layers into the whole. It may not be possible to mix by gently stirring if the cream is very thick,
15、 if the fat is partially separated, or if on stirring the cream becomes thick or the fat separates. In these circumstances, warm the sample to between30C and40C, and while it is cooling to room temperature, shake the container gently or stir the contents at intervals. Keep the container covered as m
16、uch as possible to avoid loss of moisture by evaporation. Mix the cream immediately before taking an aliquot portion of the sample for the determination. NOTEIf the sample shows any abnormality, this should be recorded. If satisfactory mixing cannot be achieved, the sample should not be tested. 5 Re
17、agents Unless otherwise stated, use reagents which are of recognized reagent grade and, wherever the use of water is required, use distilled or demineralized water complying with BS3978. 6 Rounding of numbers In carrying out the methods described in the various Parts of BS1741, use the method of rou
18、nding numbers specified in BS1957. NOTEFor example, if95.14,95.15 and95.16 are to be rounded to the nearest0.1, the rounded numbers are95.1,95.2, and95.2 respectively, i.e.where5 occurs in the second decimal place, the rounding is to the nearest even number in the first decimal place. 7 Test reports
19、 Include the following in the test reports: a) the result of each test carried out, expressed in accordance with the clause headed “Expression of results” in the appropriate Part of BS1741; b) a full reference to the method of test e.g.“Part5: Section5.1” (Reference method) of BS1741; c) a note of a
20、ny special factor that may have affected the result; d) details of the sample identity. For determination of fat (Gerber method) : BS 696-1 and BS 696-2 For density of liquid milk using a hydrometer : BS 734-1 and BS 734-2 and BS 734C For determination of freezing-point depression of liquid milk : B
21、S 3095-1, BS 3095-2 and BS 3095-3 For determination of dirt in liquid milk : BS 4938-1 and BS 4938-2 and BS 4938-2P For determination of copper content : BS 6394-1 For determination of iron content : BS 6394-2 For determination of lead content : BS 6394-3 a a In preparation.2 blankBS1741-1:1987 BSI
22、06-1999 Publications referred to BS 696, Specification for Gerber method for the determination of fat in milk and milk products. BS 696-1, Apparatus. BS 696-2, Methods. BS 734, Measurement of the density of milk using a hydrometer. BS 734-1, Specification for hydrometers for use in milk. BS 734-2, M
23、ethods. BS 734C, Percentage of total solids and non-fatty solids in milk corresponding to given fat content and observed density fat content range26 per cent (with fat in the liquid state). BS 809, Methods for sampling of milk and milk products. BS 1957, Presentation of numerical values (fineness of
24、 expression; rounding of numbers). BS 3095, Methods for determination of the freezing-point depression of milk. BS 3095-1, Hortvet method and thermistor cryoscope method. BS 3095-2, Recommendations for the interpretation of the freezing-point depression of herd milk. BS 3095-3, Storage of samples. B
25、S 3978, Specification for water for laboratory use. BS 4938, Dirt content of milk. BS 4938-1, Method for the determination of dirt content (reference method). BS 4938-2, Method for the determination of visible dirt content (rapid method). BS 4938-2P, Photographic standards for the method for the det
26、ermination of visible dirt content of milk (rapid method). BS 6394, Trace elements in milk and milk products. BS 6394-1, Method for the determination of copper content (reference method). BS 6394-2, Method for the determination of iron content (reference method). BS 6394-3, Method for the determinat
27、ion of lead content (reference method) 2) . 2) In preparation.BS 1741-1: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the internation
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