1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationDD ISO/TS 11869:2012Fermented milks Determination of titratableacidity PotentiometricmethodDD ISO/TS 11869:2012 DRAFT FOR DEVELOPMENTNational forewordThis Draft for Development i
2、s the UK implementation of ISO/TS11869:2012. It supersedes BS7142-5:1997 which is withdrawn.This publication is not to be regarded as a British Standard.It is being issued in the Draft for Development series of publicationsand is of a provisional nature. It should be applied on thisprovisional basis
3、, so that information and experience of its practicalapplication can be obtained.Comments arising from the use of this Draft for Developmentare requested so that UK experience can be reported to theinternational organization responsible for its conversion toan international standard. A review of thi
4、s publication willbe initiated not later than 3 years after its publication by theinternational organization so that a decision can be taken on itsstatus. Notification of the start of the review period will be made inan announcement in the appropriate issue of Update Standards.According to the repli
5、es received by the end of the review period,the responsible BSI Committee will decide whether to support theconversion into an international Standard, to extend the life of theTechnical Specification or to withdraw it. Comments should be sentto the Secretary of the responsible BSI Technical Committe
6、e at BritishStandards House, 389 Chiswick High Road, London W4 4AL.The UK participation in its preparation was entrusted to TechnicalCommittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can beobtained on request to its secretary.This publi
7、cation does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 75466 1ICS 67.100.99Compliance with a British Standard cannot confer immunity f
8、romlegal obligations.This Draft for Development was published under the authority ofthe Standards Policy and Strategy Committee on 29 February 2012.Amendments issued since publicationDate Text affectedDD ISO/TS 11869:2012Reference numbersISO/TS 11869:2012(E)IDF/RM 150:2012(E)ISO and IDF 2012TECHNICA
9、L SPECIFICATION ISO/TS11869IDF/RM150First edition2012-01-15Fermented milks Determination of titratable acidity Potentiometric method Laits ferments Dtermination de lacidit titrable Mthode potentiomtrique DD ISO/TS 11869:2012ISO/TS 11869:2012(E) IDF/RM 150:2012(E) COPYRIGHT PROTECTED DOCUMENT ISO and
10、 IDF 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respective address below. ISO
11、copyright office International Dairy Federation Case postale 56 CH-1211 Geneva 20 Silver Building Boulevard Auguste Reyers 70/B B-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 w
12、ww.fil-idf.org Published in Switzerland ii ISO and IDF 2012 All rights reservedDD ISO/TS 11869:2012ISO/TS 11869:2012(E) IDF/RM 150:2012(E) ISO and IDF 2012 All rights reserved iiiForeword The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies
13、(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 committee has been established has the right to be represented on that committee. International organizations, g
14、overnmental 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 electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/I
15、EC 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 member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the mem
16、ber bodies casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a technical committee may decide to publish other types of document: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in a
17、n ISO working group and is accepted for publication if it is approved by more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical committee and is accepted for publication if it is approve
18、d by 2/3 of the members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed agai
19、n after a further three years, at which time it must either be transformed into an International Standard or be withdrawn. 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 identifying any or al
20、l such patent rights. ISO/TS 11869|IDF/RM 150 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 first edition cancels and replaces ISO 11869:1997, w
21、hich has been technically revised. DD ISO/TS 11869:2012ISO/TS 11869:2012(E) IDF/RM 150:2012(E) iv ISO and IDF 2012 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committees i
22、n 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 the technical work. IDF collaborates with ISO in the development of standard methods
23、 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 the National Committees for endorsement prior to publication as an International Standa
24、rd. Publication as an International Standard requires approval by at least 50 % of IDF National Committees casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a Standing Committee may decide to publish an other type of normative documen
25、t which is called by IDF: Reviewed method. Such a method represents an agreement between the members of a Standing Committee and is accepted for publication if it is approved by at least 50 % of each National Committee representative present casting a vote. A Reviewed method is equal to an ISO/PAS o
26、r ISO/TS and will, therefore, also be published jointly under ISO conditions. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO/TS 11869|IDF/RM 150
27、 was prepared by the International Dairy Federation (IDF) and 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. All work was carried out by the Joint ISO-IDF Project Grou
28、p on Titratable acidity of the Standing Committee on Analytical methods for composition under the aegis of its project leader, Dr. J. Floor (ZA). This edition of ISO/TS 11869|IDF/RM 150 cancels and replaces IDF 150:1991, of which it constitutes a technical revision. DD ISO/TS 11869:2012TECHNICAL SPE
29、CIFICATION ISO/TS 11869:2012(E)IDF/RM 150:2012(E) ISO and IDF 2012 All rights reserved 1Fermented milks Determination of titratable acidity Potentiometric method 1 Scope This Technical Specification specifies a potentiometric method for the determination of the titratable acidity of natural yoghurt,
30、 flavoured yoghurt, fruit yoghurt, drinking yoghurt, fresh cheese with or without fruit, buttermilk with or without fruit, and other fermented milk products. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 titratable acidity of fermented milk
31、s amount in millilitres of a 0,1 mol/l sodium hydroxide solution required to titrate 10 g of product to pH 8,30 0,01 NOTE The titratable acidity is expressed in millimoles per 100 g. 3 Principle A test portion is suspended in water. The suspension is titrated potentiometrically against sodium hydrox
32、ide solution c(NaOH) 0,1 mol/l to pH 8,30 0,01. The titratable acidity is calculated. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and only distilled or deionized water, freed from carbon dioxide by boiling for 10 min before use. 4.1 Sodium hydroxide, stan
33、dard volumetric solution, c(NaOH) 0,1 mol/l 0,002 mol/l, carbonate free. Protect this solution against absorption of carbon dioxide (CO2) either by connecting a washing bottle with 10 % sodium hydroxide solution to the burette which itself contains the sodium hydroxide solution or by connecting a sm
34、all tube with fresh sodium hydroxide or calcium oxide to the end of the burette to obtain a closed system. NOTE CO2is either bound in the washing bottle or in the tube to protect the solution in the burette against absorption which would influence the concentration. DD ISO/TS 11869:2012ISO/TS 11869:
35、2012(E) IDF/RM 150:2012(E) 2 ISO and IDF 2012 All rights reserved5 Apparatus Usual laboratory equipment and, in particular, the following. 5.1 Analytical balance, capable of being read to the nearest 0,01 g. 5.2 pH meter, correctly calibrated in the range pH 7 to 10 following normal laboratory pH-ca
36、libration procedures. 5.3 Spoon or spatula. 5.4 Homogenizer, e.g. a macerator Ultra-Turrax1)or equivalent. 5.5 Burette, of capacity 25 ml or 50 ml, graduated at least at every 0,05 ml, ISO 3851, class A. Alternatively, an automatic burette, ISO 8655-34, fulfilling the same requirements may be used.
37、NOTE Instead of carrying out a manual titration, it is also possible to use an automatic titrator. 5.6 Water bath, capable of maintaining a temperature of 38 C 1 C. 6 Sampling Sampling is not part of the method specified in this Technical Specification. A recommended sampling method is given in ISO
38、707|IDF 502. It is important the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage. 7 Preparation of test sample 7.1 Natural yoghurt, flavoured yoghurt, drinking yoghurt and other fermented milks Bring the sample to a temperature of 22
39、 C 2 C. Mix the sample carefully by means of a spoon or spatula (5.3) or homogenizer (5.4), using a rotary motion which passes from the lower layers to the surface layers of the sample so as to displace and mix them well. 7.2 Fruit yoghurt and other fermented milk products with added fruit Bring the
40、 sample to a temperature of 22 C 2 C. Homogenize it using an appropriate device (5.4), in order to facilitate the grinding and dispersion of the fruit. If fat separation is observed in the sample, raise the temperature of the sample in the water bath (5.6) to 38 C 1 C for a better homogenization. Th
41、ereafter, cool the sample again to a temperature of 22 C 2 C. 1) Ultra-Turrax is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO or IDF of this product. DD ISO/TS 11869:2012
42、ISO/TS 11869:2012(E) IDF/RM 150:2012(E) ISO and IDF 2012 All rights reserved 38 Procedure 8.1 Test portion Weigh, in a 50 ml beaker, approximately 10 g of prepared test sample (Clause 7), to the nearest 0,01 g. Add approximately 10 ml of water and mix. 8.2 Determination 8.2.1 Insert the electrode of
43、 the pH meter (5.2) into the suspension (8.1). 8.2.2 Use the sodium hydroxide solution (4.1), while stirring, to titrate the contents of the beaker until the pH remains stable at 8,30 0,01 for 4 s to 5 s. If an automatic titrator is used, it shall provide for such a stop delay time as well. Record t
44、he volume, in millilitres, of sodium hydroxide solution used, at least to the nearest 0,05 ml. 9 Calculation and expression of results 9.1 Calculation Calculate the titratable acidity, I, in millimoles of sodium hydroxide per 100 g, using the following equation: 10VIm where V is the volume, in milli
45、litres, of the sodium hydroxide solution (4.1) used for the titration (8.2.2); m is the mass, in grams, of the test portion (8.1). NOTE For the expression of results in grams of lactic acid per 100 g of product, see Annex A. 9.2 Expression of test results Express the test results to two decimal plac
46、es. 10 Precision 10.1 Interlaboratory test The method has been tested on various fermented milk products in six different laboratories. Each laboratory obtained the products locally. See Reference 5. A summary of the results is given in Annex B. The value for repeatability derived from this interlab
47、oratory study was calculated in accordance with ISO 5725-13. 10.2 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval
48、of time, will in not more than 5 % of cases be greater than 0,20 mmol/100 g. DD ISO/TS 11869:2012ISO/TS 11869:2012(E) IDF/RM 150:2012(E) 4 ISO and IDF 2012 All rights reserved11 Test report The test report shall contain at least the following information: a) all information necessary for the complet
49、e identification of the sample; b) the sampling method used, if known; c) the method used, with reference to this Technical Specification (ISO/TS 11869|IDF/RM 150:2012); d) all operating details not specified in this Technical Specification, or regarded as optional, together with details of any incidents which may have influenced the test result(s); e) the test result(s) obtained; f) if the repeatability has been checked, the final quoted result obtained. DD ISO/TS 11869:2012ISO/TS
