1、BS ISO 6091:2010ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDDried milk Determination oftitratable acidity(Reference method)This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July2010 BSI
2、2010ISBN 978 0 580 70102 3Amendments/corrigenda issued since publicationDate CommentsBS ISO 6091:2010National forewordThis British Standard is the UK implementation of ISO 6091:2010. Itsupersedes BS 1743-7.1:1982 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCo
3、mmittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application. Compli
4、ance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 6091:2010Reference numbersISO 6091:2010(E)IDF 86:2010(E)ISO and IDF 2010INTERNATIONAL STANDARD ISO6091IDF86Second edition2010-06-01Dried milk Determination of titratable acidity (Reference method) Lait sec Dtermination
5、de lacidit titrable (Mthode de rfrence) BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are lice
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10、1030 Brussels Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2010 All rights reservedBS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) ISO
11、 and IDF 2010 All rights reserved iiiForeword 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
12、interested in a subject for which a technical 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 Electrotech
13、nical Commission (IEC) on all matters of electrotechnical 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 t
14、he technical committees are circulated to the 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 right
15、s. ISO shall not be held responsible for identifying any or all such patent rights. ISO 6091IDF 86 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This
16、 second edition of ISO 6091IDF 86 cancels and replaces the first edition (ISO 6091:1980), of which it constitutes a minor revision. BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) iv ISO and IDF 2010 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization re
17、presenting the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regional dairy associations having signed a formal agreement on cooperation with IDF. All members of IDF have the right to be represented on the IDF Standing Committees carrying out
18、 the technical work. IDF collaborates with ISO in the development of standard methods of analysis and sampling for milk and milk products. The main task of Standing Committees is to prepare International Standards. Draft International Standards adopted by the Standing Committees are circulated to th
19、e National Committees for endorsement prior to publication as an International Standard. Publication as an International Standard requires approval by at least 50% of IDF National Committees casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the s
20、ubject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 6091IDF 86 was prepared by the International Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly
21、 by IDF and ISO. All work was carried out by the former Joint ISO-IDF Action Team on Carbohydrate and lactate determination, now part of the Standing Committee on Analytical methods for composition. This edition of ISO 6091IDF 86 cancels and replaces IDF 86:1981, of which it constitutes a minor revi
22、sion. BS ISO 6091:2010INTERNATIONAL STANDARD ISO 6091:2010(E)IDF 86:2010(E) ISO and IDF 2010 All rights reserved 1Dried milk Determination of titratable acidity (Reference method) 1 Scope This International Standard specifies a reference method for the determination of the titratable acidity of all
23、types of dried milk. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1
24、736|IDF 9, Dried milk and dried milk products Determination of fat content Gravimetric method (Reference method) ISO 5537|IDF 26, Dried milk Determination of moisture content (Reference method) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1
25、titratable acidity of dried milk volume of 0,1 mol/l sodium hydroxide solution required to titrate a quantity of the reconstituted milk corresponding to 10 g of solids-not-fat to pH 8,40 NOTE Titratable acidity is expressed in millilitres. 4 Principle Milk is reconstituted by addition of water to a
26、test portion of dried milk corresponding accurately to 5 g of solids-not-fat. The reconstituted milk is titrated with 0,1 mol/l sodium hydroxide solution to pH 8,40. The number of millilitres used in the titration is multiplied by 2, in order to obtain the number of millilitres in terms of 10 g of s
27、olids-not-fat. The amount of sodium hydroxide solution required is a function of the amount of natural buffering substances present in the product, and of developed or added acid or alkaline substances. 5 Reagents and materials Unless otherwise stated, use only reagents of recognized analytical grad
28、e and distilled or demineralized water or water of equivalent purity, freed from carbon dioxide by boiling for 10 min before use. BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) 2 ISO and IDF 2010 All rights reserved5.1 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,1 mol/l 0,000 2 mol/
29、l, carbonate free. Protect this solution against absorption of carbon dioxide. 5.2 Nitrogen. 6 Apparatus Usual laboratory equipment and in particular the following. 6.1 Analytical balance. 6.2 pH-meter, with slope control, accurate to 0,01 pH unit, with a glass measuring electrode and a suitable ref
30、erence electrode, calibrated using two buffer solutions of approximately pH 7 and pH 9, respectively, known to within 0,01 pH unit. 6.3 Magnetic stirrer. 6.4 Burette, graduated in 0,1 ml and with an accuracy of 0,05 ml, ISO 3851class A. 6.5 Measuring cylinder, capacity 50 ml, ISO 47883class A. 6.6 C
31、onical flask, capacity 100 ml or 150 ml, with a ground neck and ground-glass stopper. The neck shall be sufficiently wide to accommodate the two electrodes, the burette tip and the nitrogen line. 7 Sampling Sampling is not part of the method specified in this International Standard. A recommended sa
32、mpling method is given in ISO 707|IDF 502. It is important that the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage. 8 Preparation of test sample Transfer the sample to a clean, dry container (provided with an airtight lid) that has
33、a capacity of about twice the volume of the sample. Close the container immediately and thoroughly mix the contents by repeatedly shaking and inverting the container. During these operations, exposure of the sample to the atmosphere should be avoided as far as possible to minimize absorption of wate
34、r. 9 Procedure 9.1 Test portion Weigh (500/w) 0,01 g of the test sample (see Clause 8) into the conical flask (6.6), w being the solids-not-fat content of the sample, expressed as a percentage mass fraction. The solids-not-fat content of the sample may be calculated by subtracting the fat content, d
35、etermined in accordance with ISO 1736|IDF 9, and the moisture content, determined in accordance with ISO 5537|IDF 26, from 100. BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) ISO and IDF 2010 All rights reserved 39.2 Determination 9.2.1 Reconstitute milk by adding 50 ml of water at about 20 C to th
36、e test portion (see 9.1) and agitating vigorously. Allow to stand for about 20 min. 9.2.2 Titrate the contents of the conical flask by adding the sodium hydroxide solution (5.1) from the burette (6.4) until the pH-meter (6.2) measurement persists at pH 8,40 for about 5 s. During the titration, the s
37、olution should be agitated using the magnetic stirrer (6.3), and absorption of carbon dioxide from the air should be avoided by flushing the conical flask with nitrogen (5.2). The titration should be completed within 1 min. Record the volume, in millilitres, of sodium hydroxide solution used, to the
38、 nearest 0,05 ml. 10 Calculation The titratable acidity, Vta, is given by the equation Vta= 2V where V is the volume, in millilitres, of the sodium hydroxide solution (5.1) used for the titration (see 9.2.2). Express the result to one decimal place. 11 Repeatability The difference between the result
39、s of two determinations carried out simultaneously or in rapid succession by the same analyst will not exceed 0,4 ml of 0,1 mol/l sodium hydroxide solution per 10 g of solids-not-fat. 12 Test report The test report shall contain at least the following information: a) all the information necessary fo
40、r the complete identification of the sample; b) the sampling method used, if known; c) the test method used, including a reference to this International Standard (ISO 6091|IDF 86:2010); d) any operating conditions not specified in this International Standard, or regarded as optional, as well as deta
41、ils of any incidents that may have influenced the result(s); e) the test result(s) obtained; f) if the repeatability has been checked, the final quoted result obtained. BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) 4 ISO and IDF 2010 All rights reservedBibliography 1 ISO 385, Laboratory glassware
42、Burettes 2 ISO 707|IDF 50, Milk and milk products Guidance on sampling 3 ISO 4788, Laboratory glassware Graduated measuring cylinders BS ISO 6091:2010BS ISO 6091:2010ISO 6091:2010(E) IDF 86:2010(E) ICS 67.100.10 Price based on 4 pages ISO and IDF 2010 All rights reserved BS ISO 6091:2010This page ha
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