1、BRITISH STANDARD BS 1743-19: 1985 Methods for Analysis of dried milk and dried milk products Part 19: Determination of scorched particles content IMPORTANT NOTE. It is essential that this Part be read in conjunction with Part1 “Generalintroduction, including preparation of laboratory samples” publis
2、hed separately. UDC 637.143:664.97:543.82BS 1743-19:1985 This British Standard, having been prepared under the directionof the Dairying Standards Committee, was published under the authority ofthe Board of BSI and comesintoeffect on 28 February1985 BSI08-1999 The following BSI references relate to t
3、he work on this standard: Committee reference DAC/3 Draft for comment 84/52541 DC ISBN 0 580 14370 8 Foreword This Part of BS1743, which has been prepared under the direction of the Dairying Standards Committee, describes a method for the determination of scorched particles in milk powders. The meth
4、od is based on ISO5739:1983, published by the International Organization for Standardization (ISO), which has been implemented asBS6248-9:1984. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct appl
5、ication. 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 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) a
6、nd may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS 1743-19:1985 BSI 08-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagen
7、ts 1 5 Apparatus 1 6 Sampling 1 7 Preparation of the test sample 1 8 Procedure 1 9 Expression of results 2 10 Test report 2 Appendix A Testing of filtering discs 3 Appendix B Preparation of scorched particle standard discs 4 Publications referred to Inside back coverii blankBS1743-19:1985 BSI 08-199
8、9 1 1 Scope This Part of BS1743 describes a method for the determination of the scorched particles content of spray dried and roller dried, skim, whole milk and buttermilk powders. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For t
9、he purposes of this Part of BS1743, the following definition applies. scorched particles content of milk powders the amount of coloured residue in a weighed sample of product, which is insoluble in water or solutions of sodium hexametaphosphate, sodium citrate or tetrasodium ethylenediaminetetra-ace
10、tate (EDTA), as determined and classified by the procedure specified in this British Standard 3 Principle A test portion of the product is dissolved in water, or in hot solutions of sodium hexametaphosphate, sodium citrate or tetrasodium ethylenediaminetetra-acetate (EDTA). The resulting solution is
11、 filtered through a filtering disc and visual comparison is made of the dried disc with scorched particle standard discs. Spray dried products may be tested satisfactorily after dissolution in water. Roller dried skim milk and whole milk powders may be tested after dissolution in sodium hexametaphos
12、phate solution or sodium citrate solution and buttermilk powder after dissolution in EDTA solution. 4 Reagents 4.1 General. During the analysis use only reagents of recognized analytical grade. The water used in the preparation of the reagent solutions and in the determination shall be distilled wat
13、er or water of at least equivalent purity, complying with BS3978 and filtered before use. 4.2 Sodium citrate, 10% solution. Dissolve100g of sodium citrate in water and make up to1000mL. Filter through a cotton disc before use. 4.3 Sodium hexametaphosphate, 2% solution. Dissolve20g of sodium hexameta
14、phosphate in water and make up to1000mL. Filter cold through a cotton disc before use. 4.4 Tetrasodium ethylenediaminetetra-acetate (EDTA), 10% solution. Dissolve100g of EDTA,tetrasodium salt, dihydrate (C 10H 12N 2Na 4 O 8 .2H 2 O) in water and make up to1000mL. Filter cold through a cotton disc be
15、foreuse. 4.5 Defoaming agent, e.g. diglycol laurate, octan-2-ol or silicone emulsion. 5 Apparatus Usual laboratory equipment and the following. 5.1 Balance, of approximately 500 g capacity and accurate to 0.1 g. 5.2 Blender or mixer NOTEBlenders manufactured by Waring, Atomix or Kenwood have been fo
16、und to be suitable. 5.3 Filtering discs, of cotton lintine, diameter32mm, suitable for use in the filtering device (5.4). The cotton lintine shall be of approximately135g/m 2No.1 filter cotton fibres. The discs shall be tested in accordance with the method described inAppendix A and shall meet the r
17、equirements specified therein. 5.4 Filtering device, aspirator or pressure type, with a filtering area of diameter28.6mm. 5.5 Scorched particle standard discs, indicating increasing scorched particles content by the classification letters A, B, C, and D respectively. NOTE 1Prints of these standard d
18、iscs are available from the United States Department of Agriculture, Agriculture Marketing Service, Dairy Division, Washington DC20250, USA. Attention is drawn to the fact that, for illustrative purposes only, a black and white reproduction of these standard discs is reproduced in BS6248-9. NOTE 2A
19、method for the preparation of these standard discs, if required, is described inAppendix B. 6 Sampling Samples shall be taken in accordance with BS809 and BS1743-1. 7 Preparation of the test sample Thoroughly mix the laboratory sample (seeBS1743-1) by repeatedly shaking and inverting the container.
20、If necessary, transfer the laboratory sample to an airtight container of sufficient capacity to allow this operation to be carried out. 8 Procedure 8.1 Spray dried milk products Measure 250 mL of water (4.1) into the jar of the blender (5.2). Start the blender and add25g of dried skim milk or dried
21、buttermilk or32.5g of dried whole milk. Add approximately0.5mL of defoaming agent (4.5) and mix for60s in the blender. Filter the entire solution through a filtering disc (5.3), using an aspirator or pressure type filtering device (5.4).BS 1743-19:1985 2 BSI 08-1999 Rinse the blender jar and filteri
22、ng device with approximately50mL of water and pass through the filtering disc also. If the reconstituted sample has been allowed to stand before filtering, stir vigorously just before pouring it into the filtering device. Do not allow samples to stand uncovered. Remove the filtering disc and allow i
23、t to dry, or dry it at30 C to40 C, in a dust-free atmosphere. 8.2 Roller dried whole milk and dried skim milk (sodium hexametaphosphate method) Measure 250 mL of the2% sodium hexametaphosphate solution (4.3), heated to80 C, into the jar of a blender (5.2). Turn on the blender and add17g of a well-mi
24、xed sample of dried skim milk or22g of dried whole milk. Add approximately0.5mL of defoaming agent (4.5) and mix for30s in the blender. Filter immediately through a filtering disc (5.3), using an aspirator or pressure type filtering device (5.4). Rinse the blender jar with about25mL of water and pas
25、s this through the filtering disc also. Allow the disc to dry, or dry it at30 C to40 C, in a dust-free atmosphere. 8.3 Roller dried whole milk and dried skim milk (sodium citrate method) Measure 200 mL of hot (80 C to90 C)10% sodium citrate solution (4.2) into the jar of a blender (5.2). Turn on the
26、 blender and add17g of a well-mixed sample of dried skim milk or22g of dried whole milk. Add approximately0.5mL of defoaming agent(4.5) and mix for30s in the blender. Filter the entire solution through a filtering disc (5.3), using an aspirator or pressure type filtering device(5.4). Rinse the blend
27、er jar and filtering device with hot water and pass this through the filtering disc also. Allow the filtering disc to dry, or dry it at30 C to40 C, in a dust-free atmosphere. 8.4 Roller dried buttermilk Place approximately 300 mL of a hot (80 C to100 C)10% solution of tetra sodium salt of ethylenedi
28、aminetetra-acetic acid (4.4) into the jar of the blender (5.2). Turn on the blender and add17g of dried buttermilk. Add approximately0.5mL of defoaming agent (4.5). Mix for8s to10s. Add additional hot solution of the dispersing agent EDTA (4.4) to the blender until the volume of sample solution is a
29、pproximately500mL. Agitate the sample solution for an additional45s and filter immediately through a filtering disc (5.3), using an aspirator or pressure type filtering device (5.4). Rinse the blender jar with hot water, and pass all rinsings through the filtering disc. Allow the filtering disc to d
30、ry, or dry it at30 C to40 C, in a dust-free atmosphere. 9 Expression of results 9.1 Evaluation The test disc shall be compared with the scorched particles standard discs (5.5), viewed from directly above in uniform indirect light, and the appropriate classification letter shall be assigned to the te
31、st disc. A test disc falling between two standard discs shall be assigned the classification letter corresponding to the higher scorched particles content. 9.2 Repeatability If duplicate determinations are carried out, both test discs shall indicate the same classification. Otherwise, repeat the det
32、ermination in duplicate. 10 Test report The test report shall show the method used and the result obtained and shall record any extraneous matter observed. It shall also mention all operating conditions not specified in this British Standard, or regarded as optional, as well as any circumstances tha
33、t may have influenced the result. The test report shall include all the details required for the complete identification of the sample.BS1743-19:1985 BSI 08-1999 3 Appendix A Testing of filtering discs (Derived from Standard Methods for the Examination of Dairy Products,14th Edition1978 and11th Edit
34、ion1960, American Public Health Association) A.1 Materials A.1.1 Wetting agent, 1% solution. Use an aerosol solution or any other suitable wetting agent. A.1.2 Gum solution. Add0.75g of carob bean or other suitable gum to100mL of water, while stirring in a blender. Remove air bubbles by treating the
35、 solution under vacuum or by heating. Boil, cool, and then add2mL of40% formaldehyde solution (this causes separation of insoluble vegetable fragments and permits the use of clear supernatant solution). To facilitate dispersion in water in the absence of a blender, suspend0.75g of carob bean in a fe
36、wmL of ethanol in a100mL volumetric flask. Dilute to the mark with water and mix thoroughly. Then proceed as described above. A.1.3 Sucrose solution. Dissolve750g of sucrose in750mL of water. A.1.4 Fine sediment mixture, 0.2g/Ldispersion. Prepare the mixture from oven dried (at100 C) ground cow manu
37、re, garden soil and charcoal. Sieve the materials separately and collect the fractions passing through a sieve of aperture size1064m diameter203.2mm (8in) and retained on a sieve of aperture size754m, proceeding as follows. Place not more than100g of cow manure or soil, and not more than50g of charc
38、oal, on the sieve of aperture size1064m nested over the sieve of aperture size754m. Cover, and position the receiver. Shake the nest of sieves by hand, at a rate of about120 strokes per minute, for5min. In maximum batches of about20g, resieve the fractions retained on the754m sieve as above for5min.
39、 Use the fractions retained from this second sieving operation and mix them uniformly in the following proportions: Place 2 g of this mixture in a100mL one-mark volumetric flask and moisten with5mL of the wetting agent (A.1.1). Add46mL of gum solution(A.1.2), bring the liquid level just into theneck
40、 of the flask by adding the sucrose solution(A.1.3), and allow to stand for at least30min. Add a few drops of ethanol, dilute tothe mark with the sucrose solution, and mix thoroughly. Pour the solution into a250mL beaker or screw-cap bottle and, allowing minimal incorporation of air, stir with a sma
41、ll mechanical stirrer at a frequency of rotation of200min 1to300min 1until the sediment is uniformly distributed as observed under bright reflected light. Position the blade of the stirrer so that fine particles do not accumulate in small eddies at the bottom of the beaker. While stirring, transfer
42、a10mL portion (corresponding to200mg of fine sediment mixture), by means of a graduated pipette (outlet of diameter3mm), to a volumetric flask and make up to1000mL with water. A.2 Apparatus Usual laboratory equipment and the following. A.2.1 Balance, accurate to0.0001g. A.2.2 Desiccator, provided wi
43、th an efficient desiccant. A.2.3 Oven, capable of being controlled at100 C. A.2.4 Filtering device (see 5.4). A.2.5 Filtering discs (see 5.3). A.2.6 Filter papers, of diameter70mm or90 mm, high quality and medium grade. A.3 Procedure A.3.1 Wash a filter paper (A.2.6), placed in a Buchner funnel with
44、 about200mL of water, dry it to constant mass at100 C, cool in a covered dish in a desiccator and weigh. A.3.2 Filter60mL of the fine sediment mixture(A.1.4), corresponding to12mg of sediment, after thoroughly mixing and stirring, through a filtering disc (A.2.5) mounted in the filtering device (A.2
45、.4), using a clean flask to collect the filtrate. Transfer the filtrate to a beaker. Rinse the flask three times with water and add the rinsings to the contents of the beaker. A.3.3 Refilter the filtrate through the washed, dried and weighed filter paper (see A.3.1) placed in a Buchner funnel. Rinse
46、 the beaker and paper thoroughly with water.Then dry the paper to constant mass at100 C (seeA.3.1). A.3.4 Test at least two more discs. A.4 Evaluation The average mass of sediment per disc passing through three or more discs should not exceed2.8mg. A standard disc prepared from a fine sediment mixtu
47、re should not appear to have sediment buried beneath the surface. cow manure 66% garden soil 28% charcoal 6%BS 1743-19:1985 4 BSI 08-1999 Appendix B Preparation of scorched particle standard discs (Derived from the US Code of Federal Regulations,7 CFR58.2676) B.1 Materials B.1.1 Sucrose solution. Di
48、ssolve750g of sucrose in750mL of water. NOTEFilter before use. B.1.2 Charcoal mixture, 1g/L dispersion. Prepare a charcoal mixture having the following composition (at least1g is required): Transfer1g of this mixture to a1000mL one-mark volumetric flask, dilute to the mark with the sucrose solution
49、(B.1.1) and mix thoroughly. B.1.3 Spray-process, non-fat dry milk solids B.1.4 Reconstituted, non-fat dry milk solids. Dissolve50g of non-fat dry milk solids (B.1.3) in500mL of water. NOTEFilter before use. B.2 Apparatus Usual laboratory equipment and the following. B.2.1 Balance, accurate to0.0001g. B.2.2 Petri dish B.2.3 Desiccator, provided with an efficient desiccant. B.2.4 Volumetric flasks, of capacities200mL and1000mL. B.2.5 Oven, capable of being controlled at119 C. B.2.6 Filtering device (see 5.4). B.2.7 Filtering discs (see 5.3). B.3 Procedure B.3.
