BS 1743-7 2-1982 Methods for analysis of dried milk and dried milk products Determination of the titratable acidity of dried milk Routine method《奶粉和奶粉制品分析方法 第7部分 奶粉可滴定酸度测定 第2节 常规法》.pdf

《BS 1743-7 2-1982 Methods for analysis of dried milk and dried milk products Determination of the titratable acidity of dried milk Routine method《奶粉和奶粉制品分析方法 第7部分 奶粉可滴定酸度测定 第2节 常规法》.pdf》由会员分享，可在线阅读，更多相关《BS 1743-7 2-1982 Methods for analysis of dried milk and dried milk products Determination of the titratable acidity of dried milk Routine method《奶粉和奶粉制品分析方法 第7部分 奶粉可滴定酸度测定 第2节 常规法》.pdf（8页珍藏版）》请在麦多课文档分享上搜索。

1、BRITISH STANDARD CONFIRMED APRIL 1993 BS 1743-7.2: 1982 ISO 6092:1980 Methods for Analysis of dried milk and dried milk products Part 7: Determination of the titratable acidity of dried milk Section 7.2 Routine method ISO title: Dried milk Determination of titratable acidity (Routine method) IMPORTA

2、NT NOTE. It is essential that this Part be read in conjunction with Part1 “General introduction, including preparation of laboratory samples”, published separately. UDC 637.143.074:664.97:543.241.5BS1743-7.2:1982 This British Standard, having been prepared under the directionof the Dairying Standard

3、s Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 29January 1982 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draftfor comment 77/52606 DC ISBN 0 580 12517 3 Amendments issued since publication Amd. No

4、. Date of issue CommentsBS1743-7.2:1982 BSI 08-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 References 1 3 Definition 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Sampling 1 8 Procedure 1 9 Expression of results 2 10 Comparison with the reference method 2 11 Test re

5、port 2 Publications referred to Inside back coverBS1743-7.2:1982 ii BSI 08-1999 National foreword This Part of BS 1743, which has been prepared under the direction of the Dairying Standards Committee, is identical with ISO 6092:1980 (including erratum published 1981-09-01) “Dried milk Determination

6、of titratable acidity (Routine method)”, prepared by ISO/TC 34, Agricultural food products, of the International Organization for Standardization (ISO). The method described in this International Standard has been developed jointly with the International Dairy Federation (IDF) and Association of Off

7、icial Analytical Chemists, USA (AOAC). The methods described in this Section 7.2 and in Section 7.1 of BS 1743 together constitute a revision of the method of determining titratable acidity of dried milk described in clause 8 of BS 1743:1968. The method given in BS1743:1968 is therefore superseded a

8、nd has been deleted from that standard. The routine method described in this Section differs from the method describedin BS 1743:1968 in that a) titration of reconstituted dried milk is with 0.1 mol/l sodium hydroxide solution to a phenolphthalein end-point using a cobalt sulphate reference colour s

9、olution (instead of with N/9 sodium hydroxide solution to a phenolphthalein end-point using a rosaniline acetate reference colour solution) and b) titratable acidity is expressed as millilitres of0.1 mol/l sodium hydroxide solution per 10 g of solids-not-fat (instead of grams of lactic acid per 100

10、g of dried milk. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn t

11、o the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Where the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. With

12、 reference to clause 7, the methods for sampling given in BS 809:1974 “Methods for sampling milk and milk products” which is related to ISO/R 707, may be employed. With reference to the note to 8.2, the fat content may be determined in accordance with the method given in BS 1743:1968 “Methods for th

13、e analysis of dried milk and dried milk products” which is related to ISO/R 1736. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself

14、 confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 6091:1980 BS 1743 Methods for analysis of dried milk and dried milk products Part 7 Determination of titratable acidity of dried milk Section 7.1:1982 Reference method (Identical) Summ

15、ary 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 may have had amendments incorporated. This will be indicated in the amendment table on the inside fro

16、nt cover.BS1743-7.2:1982 BSI 08-1999 1 1 Scope and field of application This International Standard specifies a routine method for the determination of the titratable acidity of all types of dried milk. 2 References ISO/R 707, Milk and milk products Sampling. ISO/R 1736, Dried milk Determination of

17、fat content (Reference method). ISO 6091, Dried milk Determination of titratable acidity (Reference method). 3 Definition titratable acidity of dried milk the number of millilitres of 0,1 mol/l sodium hydroxide solution required to neutralize, in the presence of phenolphthalein, a quantity of the re

18、constituted milk corresponding to 10 g of solids-not-fat, until the appearance of a pink coloration 4 Principle Preparation of reconstituted milk by addition of water to a test portion of dried milk corresponding accurately to 5 g of solids-not-fat. Titration with0,1mol/l sodium hydroxide solution u

19、sing phenolphthalein as indicator and cobalt(II) sulphate as reference colour solution. Multiplication of the number of millilitres used in the titration by the factor 2, in order to obtain the number of millilitres in terms of 10 g of solids-not-fat. The amount of sodium hydroxide solution required

20、 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 All reagents shall be of recognized analytical quality. Water shall be distilled or deionized water, freed from carbon dioxide by boiling for 10 min

21、before use. 5.1 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,1 0,000 2 mol/l. 1) 5.2 Reference colour solution Dissolve 3 g of cobalt(II) sulphate heptahydrate (CoSO 4 .7H 2 O) in water and make up to 100 ml. 5.3 Phenolphthalein solution Dissolve 2 g of phenolphthalein in 75 ml of 95

22、% (V/V) ethanol and add 20 ml of water. Add the sodium hydroxide solution (5.1) until 1 drop gives a faint pink coloration, and make up to 100 ml of water. 6 Apparatus 6.1 Analytical balance 6.2 Burette, graduated in 0,1 ml and with an accuracy of 0,05 ml. 6.3 Pipettes, of capacity 2 ml. 6.4 Measuri

23、ng cylinders, of capacity 50 ml. 6.5 Conical flasks, of capacity 100 or 150 ml, with ground necks and ground glass stoppers. 7 Sampling See ISO/R 707. 8 Procedure 8.1 Preparation of the test sample Transfer the sample to a clean, dry container (provided with an air-tight lid) of capacity about twice

24、 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 adsorption of water. 8.2 Test portion Wei

25、gh (500/a) 0,01 g of the test sample (8.1) into each of two conical flasks (6.5), a being the solids-not-fat content of the sample, expressed as a percentage to two decimal places. NOTEThe solids-not-fat content of the sample may be calculated by subtracting the fat content (determined in accordance

26、 with ISO/R 1736) and the moisture content 2)from100. 8.3 Determination 8.3.1 Prepare reconstituted milk by adding 50 ml ofwater at about 20 C to the test portion (8.2) andagitating vigorously. Allow to stand for about20min. 8.3.2 Add to one of the conical flasks 2 ml of the reference colour solutio

27、n (5.2) to obtain a colour standard, and mix by slight swirling. 1) Hitherto expressed as “0,1 0,000 2 N standard volumetric solution”. 2) A method for the determination of moisture content is specified in IDF Standard No. 26, Determination of the water content of dried milk, which is currently unde

28、r revision by a joint ISO/IDF/AOAC group of experts.BS1743-7.2:1982 2 BSI 08-1999 If a series of determinations on similar products isto be carried out, this colour standard may be used throughout. However it should be discarded after 2h. 8.3.3 Add 2 ml of the phenolphthalein solution (5.3) to the s

29、econd conical flask, and mix by slight swirling. 8.3.4 Titrate the contents of the second conical flask, while swirling, by adding the sodium hydroxide solution (5.1) from the burette (6.2) until a faint pink colour similar to that of the colour standard persists for about 5 s. The titration should

30、be completed within 45 s. Record the volume, in millilitres, of sodium hydroxide solution used, to the nearest 0,05 ml. 9 Expression of results 9.1 Method of calculation and formula The titratable acidity is equal to 2 V where V is the volume, in millilitres, of the sodium hydroxide solution (5.1) u

31、sed for titration (8.3.4). Express the result to one decimal place. 9.2 Repeatability The difference between the results of two determinations carried out simultaneously or in rapid succession by the same analyst shall not exceed 0,4 ml of 0,1 mol/l sodium hydroxide solution per 10 g of solids-not-f

32、at. 10 Comparison with the reference method Verify at intervals whether this routine method gives results in adequate agreement with those obtained using the reference method specified in ISO 6091. 11 Test report The test report shall show the method used and the result obtained. It shall also menti

33、on any operating conditions not specified in this International Standard, or regarded as optional, as well as any circumstances that may have influenced the result. The test report shall include all details required for the complete identification of the sample.BS1743-7.2:1982 BSI 08-1999 Publicatio

34、ns referred to See national foreword.BS 1743-7.2: 1982 ISO6092:1980 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 international level.

35、It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be gratefu

36、l if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called

37、PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001. In response to orders for international standa

38、rds, it is BSI policy to supply the BSI implementation of those that have been published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to

39、Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax:02089967048. Subscribing members of BSI are kept up to date with standards developments and receive substantial

40、discounts on the purchase price of standards. For details of these and other benefits contact Membership Administration. Tel:02089967002. Fax:02089967001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the internationalstandardiz

41、ation bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, photocopying, recording or otherwise without prior written permission from BSI. This does not preclude

42、 the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations. If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained. If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel:02089967070.