BS ISO 11870-2009 Milk and milk products - Determination of fat content - General guidance on the use of butyrometric methods《牛奶和乳制品 脂肪含量的测定 乳脂计法使用的一般指南》.pdf

1、BS ISO11870:2009ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMilk and milk products Determination offat content Generalguidance on the use ofbutyrometric methodsThis British Standardwas published under theauthority of the StandardsPolicy and Stra

2、tegyCommittee on 31 October2009 BSI 2009ISBN 978 0 580 67128 9Amendments/corrigenda issued since publicationDate CommentsBS ISO 11870:2009National forewordThis British Standard is the UK implementation of ISO 11870:2009. Itsupersedes BS ISO 11870:2000 which is withdrawn.The UK participation in its p

3、reparation was entrusted to TechnicalCommittee 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 responsi

4、ble for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 11870:2009Reference numbersISO 11870:2009(E)IDF 152:2009(E)ISO and IDF 2009INTERNATIONAL STANDARD ISO11870IDF152Second edition2009-10-01Milk and milk products Determination of fat c

5、ontent General guidance on the use of butyrometric methods Lait et produits laitiers Dtermination de la teneur en matire grasse Lignes directrices gnrales pour lutilisation des mthodes butyromtriques BS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) PDF disclaimer This PDF file may contain embedded

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10、the respective address below. ISO copyright office International Dairy Federation Case postale 56 CH-1211 Geneva 20 Diamant Building Boulevard Auguste Reyers 80 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 info

11、fil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2009 All rights reservedBS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) ISO and IDF 2009 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of na

12、tional 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 committee has been established has the right to be represented on that committee. Intern

13、ational 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 electrotechnical standardization. International Standards are drafted in accordance with the

14、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 member bodies for voting. Publication as an International Standard requires approval by

15、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 identifying any or all such patent rights. ISO 11870IDF 152 was prepared by Technical Committ

16、ee 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 second edition of ISO 11870IDF 152 cancels and replaces the first edition (ISO 11870:2000), of which it constitutes a minor revisio

17、n. BS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) iv ISO and IDF 2009 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regiona

18、l 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 of analysis and sampling for milk and mi

19、lk products. The main task of Standing Committees is to prepare International Standards. 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 %

20、 of the IDF National Committees casting a vote. 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 11870IDF 152 was prepared by the International Da

21、iry Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. All work was carried out by the former Joint ISO-IDF Group of Experts (E301 Fat) which is now part of the Joint ISO-IDF Action Team on Fat o

22、f the Standing Committee on Main components in milk. This edition of ISO 11870IDF 152 cancels and replaces IDF 152A:1997, of which it constitutes a minor revision. BS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) ISO and IDF 2009 All rights reserved vIntroduction Reference methods for the determin

23、ation of fat in milk and milk products are time-consuming to apply and require some experience if reliable results are to be obtained. Butyrometric techniques, which are simpler to apply, make it possible to obtain fat contents for various milk products quickly. This is why they are used in a great

24、number of industrial laboratories as a fast method for routine checks. Two acid-butyrometric methods used in many countries to determine the fat content of milk (Gerber method) and of cheese (Van Gulik method) are the subject of International Standards. The apparatus has also been standardized. In a

25、ddition, there are other butyrometric methods and butyrometers which have been described or applied in various countries for other types of products (cream, milk powder, etc.). Whilst only one procedure exists as a reference method for a particular product type, this is not the case for butyrometric

26、 methods. Depending upon the country, different butyrometric methods may exist for one single type of product, presenting many problems for the harmonization of such procedures. Another problem relates to the applicability of such methods. Indeed, with evolving manufacturing technologies, the variet

27、y of milk products is such that it is not possible to determine a method which can be applied to all varieties of a single type of product (milk, cheese, cream, etc.). Tests have confirmed this and have shown that the butyrometric methods already standardized have been attributed fields of applicati

28、on which are far too wide-ranging. Thus this general guide has been prepared to be used in conjunction with existing International Standards. BS ISO 11870:2009BS ISO 11870:2009INTERNATIONAL STANDARD ISO 11870:2009(E)IDF 152:2009(E) ISO and IDF 2009 All rights reserved 1Milk and milk products Determi

29、nation of fat content General guidance on the use of butyrometric methods 1 Scope This International Standard gives guidance on: a) existing standardized methods (both reference and butyrometric) for the determination of fat in various milk products; b) the principles underlying any acid-butyrometri

30、c analysis and the main operating requirements; c) a validation procedure for a butyrometric method in relation to the relevant reference method. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition c

31、ited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2446IDF 226:2008, Milk Determination of fat content ISO 3433IDF 222, Cheese Determination of fat content Van Gulik method 3 Principle The principles of any butyrometric method

32、remain constant, independent of the product to be analysed. Protein is digested with sulfuric acid. The fat in the product is separated by centrifuging it in a butyrometer. The separation is enhanced by the addition of a small quantity of isoamyl alcohol. The butyrometer scale is then read directly

33、with or without correction. 4 Methods for the determination of fat content Methods for the determination of fat content are based upon acid-butyrometric and reference gravimetric methods. The Gerber method is specified in ISO 2446IDF 226 and the Van Gulik method in ISO 3433IDF 222. Existing butyrome

34、tric and reference methods for most dairy products are listed in Table A.1. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled water or demineralized water or water of equivalent purity. BS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) 2 ISO and

35、IDF 2009 All rights reserved5.1 Sulfuric acid, pure, colourless or pale amber and containing no impurities. 5.2 Isoamyl alcohol. A volume fraction of at least 99 % of the isoamyl alcohol shall consist of the primary alcohols 3-methylbutan-1-ol and 2-methylbutan-1-ol, the only permissible major impur

36、ities being 2-methylpropan-1-ol and butan-1-ol. It shall be free from secondary pentanols, 2-methylbutan-2-ol, furan-2-al (furfural, furan-2-carboxaldehyde, 2-furaldehyde), gasoline (petrol), and derivatives of benzene. Not more than a trace of water shall be present. 6 Apparatus Usual laboratory eq

37、uipment and, in particular, the following. 6.1 Butyrometer and stopper, suitable for the method used. 6.2 Dispensers, for acid and alcohol, to deliver the requisite volumes precisely and with sufficient repeatability. 6.3 Centrifuge, to accommodate a butyrometer, provided with a speed indicator whic

38、h indicates the rotational frequency with a maximum tolerance of 70 r/min, preferably of the vertical-loading type rather than the horizontal-loading type. The centrifuge should be capable of maintaining the temperature of the butyrometer contents at between 30 C and 50 C after centrifuging. The use

39、 of a heated centrifuge is permitted provided that the results obtained agree with the reference method. When loaded, the centrifuge should be capable of producing, within 2 min, a relative centrifugal acceleration of 350g 50g at the outer end of the butyrometer stopper. This acceleration is produce

40、d by centrifuges with an effective radius (horizontal distance between the centre of the centrifuge spindle and the outer end of the butyrometer stopper) as given in Table 1, operated at the speed indicated. Table 1 Centrifuge accelerations Effective radius mm Revolutions per minute 70 r/min 240 1 1

41、40 245 1 130 250 1 120 255 1 110 260 1 100 265 1 090 270 1 080 275 1 070 300 1 020 325 980 BS ISO 11870:2009ISO 11870:2009(E) IDF 152:2009(E) ISO and IDF 2009 All rights reserved 3The relative centrifugal acceleration produced in a centrifuge, , is given by: = 1,12 rn2 106where r is the effective ho

42、rizontal radius, in millimetres; n is the rotational frequency, in number of revolutions per minute. 6.4 Pipette or analytical balance, precise enough to ensure accurate distribution when preparing the test sample. 6.5 Water bath, thermostatically controlled, capable of maintaining the whole apparat

43、us at the desired uniform temperature, and offering sufficient depth for the butyrometers to be supported in a vertical position with their scale graduations completely immersed. 7 Sampling Sampling is not part of the method specified in this International Standard. A recommended sampling method is

44、given in ISO 707IDF 502. A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. 8 Preparation of test sample For each product to be analysed, refer to the relevant reference method. 9 Procedure Accurately and quickly,

45、take a test portion from a homogeneous sample. Prepare the test portion by dissolving the protein by shaking, and record the type of shaking (vertical or horizontal, frequency and amplitude, etc.). Centrifuge for a specified time with a specified centrifugal force. Take readings rapidly, immediately

46、 on removal from the water bath. If the fat cools, its volume decreases and the results obtained are incorrect. If readings are being taken by hand, hold the butyrometer vertically with the point of reading at eye level. During this process, hold the stopper absolutely still. If the fat is turbid or

47、 dark in colour, or if there is white or black material at the bottom of the fat column, the value for fat content is not reliable. If phase separation is not clear-cut, centrifuging twice would produce too high a result. In such cases, repeat the analysis. 10 Care of butyrometers After the reading

48、has been taken, invert the butyrometers, stoppers upwards, on a rack. In approximately 30 min, the fat from the bulb and the graduation tube rise upward under the stopper. As the butyrometers are still hot, remove the stoppers carefully, holding the open end close to the bottom of a sink. BS ISO 118

49、70:2009ISO 11870:2009(E) IDF 152:2009(E) 4 ISO and IDF 2009 All rights reservedWash the emptied butyrometers, which are still hot, without using a bottle brush, by shaking them vigorously with an appropriate detergent. Plunge the butyrometers into water containing a detergent, then fill and empty them several times and shake them vigorously, paying special attention to the small bulb. Rinse the butyrometers three times with hot water (i.e. three separate amounts, vigorously shaking and emptyin