1、 Reference numbers ISO 6731:2010(E) IDF 21:2010(E) ISO and IDF 2010INTERNATIONAL STANDARD ISO 6731 IDF 21 Second edition 2010-11-15 Milk, cream and evaporated milk Determination of total solids content (Reference method) Lait, crme et lait concentr non sucr Dtermination de la matire sche (Mthode de
2、rfrence) ISO 6731:2010(E) IDF 21:2010(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 licensed to and installed on the computer performin
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6、uding photocopying and microfilm, without permission in writing from either ISO or IDF at 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
7、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 reservedISO 6731:2010(E) IDF 21:2010(E) ISO and IDF 2010 All rights reserved iiiForeword ISO (the Internat
8、ional 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 committee has bee
9、n 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 electrotechnical stand
10、ardization. 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 member bodies for
11、 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 identifying any or all
12、 such patent rights. ISO 6731 IDF 21 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 second edition of ISO 6731 IDF 21 cancels and replaces the fi
13、rst edition (ISO 6731:1989), of which it constitutes a minor revision. ISO 6731:2010(E) IDF 21:2010(E) iv ISO and IDF 2010 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Comm
14、ittees 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 the technical work. IDF collaborates with ISO in the development of standard
15、 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 the National Committees for endorsement prior to publication as an Internationa
16、l 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 subject of patent rights. IDF shall not be held responsible for identifying a
17、ny or all such patent rights. ISO 6731 IDF 21 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 by IDF and ISO. All work was carried out by the former Joint ISO-IDF Actio
18、n Team on Water, now part of the Standing Committee on Analytical methods for composition. This edition of ISO 6731 IDF 21 cancels and replaces IDF 21B:1987. INTERNATIONAL STANDARD ISO 6731:2010(E) IDF 21:2010(E) ISO and IDF 2010 All rights reserved 1Milk, cream and evaporated milk Determination of
19、total solids content (Reference method) 1 Scope This International Standard specifies the reference method for the determination of the total solids content of milk, cream and evaporated milk. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 t
20、otal solids content mass fraction of substances remaining after completion of the heating process specified in this International Standard NOTE Total solids content is expressed as a percentage by mass. 3 Principle A test portion is predried on a boiling water bath and the remaining water subsequent
21、ly evaporated in a drying oven at a temperature of 102 C 2 C. 4 Apparatus and materials Unless otherwise stated, use only distilled or demineralized water or water of equivalent purity. Usual laboratory apparatus and in particular the following. 4.1 Analytical balance. 4.2 Desiccator, provided with
22、an efficient desiccant (e.g. freshly dried silica gel with a hygrometric indicator). 4.3 Boiling water bath, provided with openings of adjustable size. 4.4 Drying oven, ventilated, capable of being maintained thermostatically at 102 C 2 C throughout the total working space. 4.5 Flat-bottom dishes, o
23、f height 20 mm to 25 mm, diameter 50 mm to 75 mm, and made of appropriate material (e.g. stainless steel, nickel or aluminium), provided with well-fitting, readily removable lids. 4.6 Water baths. 4.6.1 Water bath, capable of being maintained at 35 C to 40 C. ISO 6731:2010(E) IDF 21:2010(E) 2 ISO an
24、d IDF 2010 All rights reserved4.6.2 Water bath, capable of being maintained at 40 C to 60 C. 4.7 Homogenizer (optional; see 7.1). 5 Sampling Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707 IDF 50 1 . It is important the l
25、aboratory receive a truly representative sample which has not been damaged or changed during transport or storage. 6 Preparation of the test sample 6.1 Milk Bring the sample to a temperature of 20 C to 25 C. Mix thoroughly to ensure a homogeneous distribution of the fat throughout the sample. Avoid
26、agitating so vigorously as to cause frothing of the milk or churning of the fat. If it is found difficult to disperse the cream layer, warm slowly to 35 C to 40 C on a water bath (4.6.1) with careful mixing and incorporate any cream adhering to the container. Cool the sample quickly to 20 C to 25 C.
27、 If desired, a homogenizer may be used to assist the dispersion of the fat. NOTE Correct results cannot be expected if the sample contains separated liquid fat or separate visible irregularly shaped white particles adhering to the walls of the container. 6.2 Cream Warm the sample slowly to a tempera
28、ture of 35 C to 40 C on a water bath (4.6.1). Mix or stir the cream thoroughly but not so vigorously as to cause frothing or churning. Cool the sample quickly to 20 C to 25 C. In order to reduce the evaporation of water to a minimum during mixing, the container should be uncovered for as short a tim
29、e as possible. NOTE Correct results cannot be expected if adequate mixing of the sample is not achieved or if the sample shows any evidence of churning or any other signs of abnormality. 6.3 Evaporated milk Shake the container thoroughly with frequent inversion. Open this container and pour the milk
30、 slowly into another container made of glass or other suitable material, provided with an airtight lid, taking care to incorporate in the sample any fat or other constituents adhering to the walls of the original container. Stir vigorously and close the container. Heat the closed container in a wate
31、r bath (4.6.2) at 40 C to 60 C. Remove and shake the container vigorously every 15 min. After 2 h, remove the container and cool to 20 C to 25 C. Remove the lid and mix thoroughly by stirring the milk with a spoon or spatula. NOTE If the fat separates, correct results cannot be expected. ISO 6731:20
32、10(E) IDF 21:2010(E) ISO and IDF 2010 All rights reserved 37 Procedure 7.1 Preparation of the dish Heat a dish (4.5), with its lid alongside, in the oven (4.4) for at least 1 h. Place the lid on the dish and immediately transfer to the desiccator (4.2). Allow to cool to room temperature (at least 30
33、 min) and weigh to the nearest 0,1 mg. 7.2 Test portion Quickly weigh, to the nearest 0,1 mg, 1 g to 5 g of the prepared test sample (depending on the expected solids content) into the prepared dish (7.1). In the case of milk or cream, tilt the dish to spread the test portion evenly over the bottom
34、of the dish. In the case of evaporated milk, add 3 ml to 5 ml of water, tilt the dish to mix, and spread the test portion evenly over the bottom of the dish. 7.3 Determination 7.3.1 Place the dish without lid on the vigorously boiling water bath (4.3) in such a way that the bottom of the dish is max
35、imally exposed to and directly heated by the steam. Leave for 30 min. 7.3.2 Remove the dish from the water bath and then heat it, with its lid alongside, in the oven (4.4) for 2 h. Place the lid on the dish and immediately transfer to the desiccator (4.2). 7.3.3 Allow the dish to cool to room temper
36、ature (at least 30 min) and weigh to the nearest 0,1 mg. 7.3.4 Again heat the dish, with its lid alongside, in the oven but for only 1 h. Place the lid on the dish and immediately transfer to the desiccator. Allow to cool as in 7.3.3 and weigh to the nearest 0,1 mg. 7.3.5 Repeat the operations speci
37、fied in 7.3.4 until the difference in mass between two consecutive weighings does not exceed 1 mg. Record the lowest mass. 8 Expression of results 8.1 Method of calculation The total solids content, expressed as a percentage by mass, is equal to 20 10 100 mm mm where m 0is the mass, in grams, of the
38、 dish and lid (see 7.1); m 1is the mass, in grams, of the dish, lid and test portion (see 7.2); m 2is the mass, in grams, of the dish, lid and dried test portion (see 7.3.5). Round the value obtained to the nearest 0,01 % mass fraction. 8.2 Precision NOTE The values for repeatability and reproducibi
39、lity are expressed at the 95 % probability level and were derived from the results of an inter-laboratory test (see Reference 3) carried out in accordance with ISO 5725:1986 2 . ISO 6731:2010(E) IDF 21:2010(E) 4 ISO and IDF 2010 All rights reserved8.2.1 Repeatability The difference between two singl
40、e results found on identical test material by one analyst using the same apparatus within a short time interval will exceed the following values of total solids per 100 g of product on average not more than once in 20 cases in the normal and correct operation of the method: for milk 0,10 g for cream
41、 0,20 g for evaporated milk 0,30 g 8.2.2 Reproducibility The difference between two single and independent results found by two operators working in different laboratories on identical test material will exceed the following values of total solids per 100 g of product on average not more than once i
42、n 20 cases in the normal and correct operation of the method: for milk 0,20 g for cream 0,35 g for evaporated milk 0,50 g 9 Test report The test report shall contain at least the following information: a) all information necessary for the complete identification of the sample; b) the sampling method
43、 used, if known; c) the test method used, with reference to this International Standard (ISO 6731 IDF 21:2010); d) all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s); e) the
44、test result(s) obtained; f) if the repeatability has been checked, the final quoted result obtained. ISO 6731:2010(E) IDF 21:2010(E) ISO and IDF 2010 All rights reserved 5Bibliography 1 ISO 707|IDF 50, Milk and milk products Guidance on sampling 2 ISO 5725:1986, Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests 1)3 STEIGER, G., MARTENS, R. Bull. Int. Dairy Fed. 1986, (207) 1) Superseded. ISO 6731:2010(E) IDF 21:2010(E) ICS 67.100.10: 67.100.99 Price based on 5 pages ISO and IDF 2010 All rights reserved
