1、BRITISH STANDARD BS ISO 5548:2004 Caseins and caseinates Determination of lactose content Photometric method ICS 67.100.99 BS ISO 5548:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 7 December 2004 BSI 7 December 2004 ISBN 0 580 44986 6
2、 National foreword This British Standard reproduces verbatim ISO 5548:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has the responsibility to: A list of organizations represented on
3、 this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Se
4、arch” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal
5、obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summ
6、ary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 6, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since pu
7、blication Amd. No. Date Comments Reference numbers ISO 5548:2004(E) IDF 106:2004(E) OSI DI dnaF 4002INTERNATIONAL STANDARD ISO 5548 IDF 106 Second edition 2004-12-01 Caseins and caseinates Determination of lactose content Photometric method Casines et casinates Dtermination de la teneur en lactose M
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13、 337 888 aFx0 947 22 14 + 974 aFx0 337 2 23 + 431 -Email copyrightisoo.rg -Emailni off-lidif.org We bwww.is.o gro We bwww.fil-idf.o gr Plbuisdehi n Switlrez dnaii ISO dnaID 4002 FA ll rihgtsser edevrBSISO5548:2004IS:8455 O4002(E) ID:601 F002(4)E I SO dna ID 4002 F All irhgts seredevr iiiContents For
14、eword iv 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle . 1 5 Reagents 2 6 Apparatus. 2 7 Sampling 3 8 Procedure. 3 8.1 Preparation of test sample. 3 8.2 Preparation of a blank solution . 3 8.3 Test portion . 3 8.4 Test solution 3 8.5 Determination 4 8.6 Preparation of c
15、alibration graph . 4 9 Calculation and expression of results 5 9.1 Calculation. 5 9.2 Expression of results 5 10 Precision 5 10.1 Repeatability 5 10.2 Reproducibility 5 11 Test report 5 Bibliography . 6 BSISO5548:2004IS:8455 O4002(E) ID:601 F002(4)E iv I SO dna ID 4002 F All irhgts seredevrForeword
16、ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical
17、committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of elect
18、rotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the
19、member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for ident
20、ifying any or all such patent rights. ISO 5548IDF 106 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and sepa
21、rately by AOAC International. This edition of ISO 5548IDF 106 cancels and replaces ISO 5548:1980, of which it constitutes a minor revision. Only editorial changes have been made. BSISO5548:2004IS:8455 O4002(E) ID:601 F002(4)E I SO dna ID 4002 F All irhgts seredevr vForeword IDF (the International Da
22、iry Federation) is a worldwide federation of the dairy sector with a National Committee in every member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the developmen
23、t of standard methods of analysis and sampling for milk and milk products. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires approval by at least 50 % of the Nation
24、al Committees casting a vote. ISO 5548IDF 106 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately b
25、y AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Group of Experts, Methods for caseins and caseinates (E36), under the aegis of its project leader, Mr J. Eisses (NL). This edition of ISO 5548IDF 106 cancels and replaces IDF 106:1982. Only editorial changes have been made. BSI
26、SO5548:2004blank 4002:8455OSISBNITERNATNOIAL STANDARD IS:8455 O4002(E) ID:601 F002(4)EI SO dna ID 4002 F All irhgts seredevr 1Caseins and caseinates Determination of lactose content Photometric method 1 Scope This International Standard specifies a photometric method for the determination of the con
27、tent of lactose and other soluble carbohydrates in caseins and caseinates containing less than 2,0 % of total soluble carbohydrates. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies.
28、 For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth 3 Terms and definitions For the purposes of this document, the following terms and definitions
29、 apply. 3.1 lactose content of caseins and caseinates content of total soluble carbohydrates, expressed as anhydrous lactose, determined by the procedure specified in this International Standard NOTE It is expressed as a mass fraction in percent. 4 Principle A test portion is dissolved a) in hot wat
30、er in the case of caseinates; b) in hot water with the addition of sodium hydrogen carbonate in the case of acid caseins; c) in hot water with the addition of pentasodium triphosphate in the case of rennet casein. The casein is precipitated with a solution of acetic acid and sodium acetate at pH 4,6
31、, then filtered to obtain a protein-free solution of the carbohydrates. Phenol solution and concentrated sulfuric acid are added to an aliquot portion of the filtrate, thus producing a colour which is proportional to the amount of carbohydrate present, which is measured photometrically at a waveleng
32、th of 490 nm. BSISO5548:2004IS:8455 O4002(E) ID:601 F002(4)E 2 I SO dna ID 4002 F All irhgts seredevr5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 5.1 Sodium hydrogen carbonate (NaHCO 3 ),
33、for analysis of acid casein. 5.2 Pentasodium triphosphate (Na 5 P 3 O 10 ), for analysis of rennet casein. 5.3 Dilute hydrochloric or sulfuric acid, c(HCl) or c(1/2 H 2 SO 4 ) = 0,1 mol/l. 5.4 Dilute acetic acid, c(CH 3 CO 2 H) = 100 g/l. 5.5 Sodium acetate solution, c(CH 3 COONa) = 1 mol/l. 5.6 Phe
34、nol solution, 80 % (mass fraction). Heat a mixture of 8 g of phenol and 2 g of water until the mixture is homogeneous. 5.7 Sulfuric acid, concentrated, 20(H 2 SO 4 )= 1,84 g/ml. 5.8 Lactose standard solution, 20 (C 12 H 22 O 11 ) = 20 g/l. Weigh 2,105 g 0,001 g of lactose monohydrate, corresponding
35、to 2,00 g of anhydrous lactose, into a 100 ml volumetric flask. Dissolve in water, make up to the mark with water and mix well. Store the obtained standard solution at 0 C. 6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to the ne
36、arest 1 mg. 6.2 Conical flasks, of capacity 100 ml. 6.3 One-mark pipettes, of capacity 1 ml, 2 ml and 10 ml. 6.4 Micropipettes, of capacity 0,2 ml, with 0,001 ml divisions. 6.5 Graduated pipettes, of capacity 25 ml. 6.6 Test tubes, of capacity about 40 ml, with ground necks and fitted with ground gl
37、ass stoppers. 6.7 Automatic dispenser, capable of dispensing 5 ml of concentrated sulfuric acid within 1 s. 6.8 Water bath, capable of being maintained at 60 C to 70 C. 6.9 Photometer, suitable for making measurements at a wavelength of 490 nm, provided with cells of optical path length 1 cm to 2 cm
38、. 6.10 Mixer, suitable for mixing inside the test tubes (6.6), with a stirrer resistant to strong acid. 6.11 Grinding device, for grinding the laboratory sample, if necessary (see 8.1.4), without development of undue heat and without loss of moisture. A hammer-mill shall not be used. BSISO5548:2004I
39、S:8455 O4002(E) ID:601 F002(4)E I SO dna ID 4002 F All irhgts seredevr 36.12 Test sieve, of wire cloth, of diameter 200 mm, nominal size of aperture 500 m, with receiver, complying with ISO 3310-1. 6.13 Volumetric flasks, of capacity 100 ml. 6.14 Water bath, capable of being maintained at 20 C. 7 Sa
40、mpling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707 1 . 8 Procedure 8.1 Preparati
41、on of test sample 8.1.1 Thoroughly mix the laboratory sample by repeatedly shaking and inverting the container (if necessary after having transferred all of the laboratory sample to an airtight container of sufficient capacity to allow this operation to be carried out). 8.1.2 Transfer about 50 g of
42、the thoroughly mixed laboratory sample to the test sieve (6.12). 8.1.3 If the 50 g portion passes completely or almost completely through the sieve, use the sample prepared in 8.1.1 for the determination. 8.1.4 Otherwise, grind the 50 g portion, using the grinding device (6.11), until it passes thro
43、ugh the sieve. Immediately transfer all the sieved sample to an airtight container of sufficient capacity, and mix thoroughly by repeatedly shaking and inverting. During these operations, take precautions to avoid any change in the water content of the product. 8.1.5 After the test sample has been p
44、repared, carry out the determination (8.5) as soon as possible. 8.2 Preparation of a blank solution Prepare a blank solution containing 0,1 g 0,001 g of sodium hydrogen carbonate (5.1) or 0,1 g 0,001 g of pentasodium triphosphate (5.2), as appropriate, using the same apparatus, the same reagents in
45、the same amounts, and the same procedure as described in 8.4.2 to 8.5.1 inclusive, but omitting the test portion and omitting those operations in connection with the presence of a test portion. For the most accurate results, prepare the blank solution, the test solution and the lactose standard work
46、ing solutions for the calibration graph (see 8.6) simultaneously. 8.3 Test portion Weigh, to the nearest 1 mg, about 1 g of the test sample (8.1) into a conical flask (6.2). 8.4 Test solution 8.4.1 In the case of acid casein, add 0,1 g 0,001 g of the sodium hydrogen carbonate (5.1). In the case of r
47、ennet casein, add 0,1 g 0,001 g of the pentasodium triphosphate (5.2). BSISO5548:2004IS:8455 O4002(E) ID:601 F002(4)E 4 I SO dna ID 4002 F All irhgts seredevr8.4.2 Add 25 ml of water, place in the water bath (6.8), set at between 60 C and 70 C, and mix occasionally by shaking. 8.4.3 When the test po
48、rtion is completely dissolved (which generally takes 10 min to 15 min), cool the solution and add successively 15 ml of water, 8 ml of the dilute hydrochloric or sulfuric acid (5.3), and 1 ml of the dilute acetic acid (5.4). Stopper and mix the contents by shaking after each addition. 8.4.4 Leave fo
49、r 5 min and then add 1 ml of the sodium acetate solution (5.5). Mix by shaking. 8.4.5 Allow the casein precipitate to settle, then filter through a dry filter paper. Discard the first few millilitres of the filtrate. 8.5 Determination 8.5.1 Pipette 2 ml of the filtrate (8.4.5) into a test tube (6.6). Add 0,2 ml of the phenol solution (5.6) by means of a micropipette (6.4), and mix by shaking. Then add from the auto
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