1、 Reference numbers ISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005INTERNATIONAL STANDARD ISO 13580 IDF 151 First edition 2005-05-01 Yogurt Determination of total solids content (Reference method) Yaourt Dtermination de la teneur totale en matires solides (Mthode de rfrence) ISO 13580:2005(E) IDF
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6、iting 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 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-m
7、ail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2005 All rights reservedISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005 All rights reserved iiiContents Page Foreword iv 1 Scope 1 2 Normative references. 1 3 Terms and definiti
8、ons. 1 4 Principle. 1 5 Reagents 1 6 Apparatus. 2 7 Sampling 2 8 Preparation of test sample. 2 8.1 Natural yogurt and flavoured, sweetened yogurt 2 8.2 Fruit yogurt 2 9 Procedure. 3 9.1 Preparation of the dish. 3 9.2 Test portion. 3 9.3 Determination of total solids content . 3 9.4 Determination of
9、lactic acid content . 3 10 Calculation and expression of results 4 10.1 Calculation. 4 10.2 Expression of results 4 11 Precision 4 11.1 Interlaboratory test. 4 11.2 Repeatability 4 11.3 Reproducibility 4 12 Test report 5 Annex A (informative) Interlaboratory test. 6 Bibliography . 7 ISO 13580:2005(E
10、) IDF 151:2005(E) iv ISO and IDF 2005 All rights reservedForeword 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 committee
11、s. 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, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the Inter
12、national Electrotechnical 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 St
13、andards 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 member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the sub
14、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 13580 IDF 151 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC
15、International. It is being published jointly by ISO and IDF and separately by AOAC International. ISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005 All rights reserved vForeword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every
16、 member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard methods of analysis and sampling for milk and milk products. Draft International S
17、tandards 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 % of the National Committees casting a vote. Attention is drawn to the possibility that some of the elements of
18、 this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 13580 IDF 151 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF)
19、, in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Action Team on Water, of the Standing Committee Main components of milk, under the aegis of its project leader, Mrs M. Nic
20、olas (FR). This edition of ISO 13580 IDF 151 cancels and replaces the first edition of IDF 151:1991. INTERNATIONAL STANDARD ISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005 All rights reserved 1Yogurt Determination of total solids content (Reference method) 1 Scope This International Standard spec
21、ifies a reference method for the determination of the total solids content of plain, flavoured, sweetened and fruit yogurts. 2 Normative references The following referenced document is indispensable for the application of this document. For dated references, only the edition cited applies. For undat
22、ed references, the latest edition of the referenced document (including any amendments) applies. ISO 11869, Yogurt Determination of titratable acidity Potentiometric method1)3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 total solids content
23、 mass fraction of substances remaining after completion of the heating process specified in this International Standard NOTE The total solids content is expressed as a percentage by mass. 4 Principle Water from a test portion is evaporated in the presence of zinc oxide in a drying oven at 102 C 2 C.
24、 The lactic acid content is determined in order to compensate for the loss of water produced by neutralization. 5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled water or demineralized water or water of equivalent purity. 5.1 Zinc oxide, at least
25、99 % pure. 1) Equivalent to IDF 150. ISO 13580:2005(E) IDF 151:2005(E) 2 ISO and IDF 2005 All rights reserved6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. 6.2 Desiccator, contai
26、ning an effective desiccant (e.g. freshly dried silica gel with hygrometric indicator). 6.3 Drying oven, well ventilated, capable of being maintained at 102 C 2 C throughout the working space. 6.4 Flat-bottom dishes, of height 20 mm to 25 mm, of diameter 50 mm to 75 mm, made of appropriate material
27、(e.g. stainless steel, nickel or aluminium), provided with well-fitting, readily removable lids. 6.5 Boiling water bath or steam bath. 6.6 Short stirring rods, made of glass, flattened at one end and of suitable size to fit into the dish (6.4). 6.7 Homogenizer, for homogenizing fruit yogurt (see 8.2
28、). 6.8 Spoon or spatula. 7 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707
29、IDF 50. Store the sample in such a way that deterioration and change in composition are prevented. 8 Preparation of test sample 8.1 Natural yogurt and flavoured, sweetened yogurt Bring the sample to a temperature of between 20 C and 25 C. Mix the sample carefully by means of a spoon or spatula, usin
30、g a rotary motion which passes from the lower layers to the surface layers of the sample so as to displace and mix them well. 8.2 Fruit yogurt Bring the sample to a temperature of between 20 C and 25 C. Homogenize it using an appropriate device, in order to facilitate the grinding and dispersion of
31、the fruit. Transfer the test sample to an airtight container until the analysis, which should be carried out as soon as possible after homogenization. If delay cannot be avoided, take all necessary precautions to prevent deterioration of the sample and to avoid condensation of moisture on the intern
32、al surface of the sample container. ISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005 All rights reserved 39 Procedure 9.1 Preparation of the dish Heat an open dish (6.4) containing approximately 2 g of zinc oxide (5.1), together with its lid and a stirring rod (6.6) placed on top of the lid, in th
33、e drying oven (6.3) set at 102 C for at least 1 h. Place the lid with the stirring rod on top on the dish and immediately transfer it to the desiccator (6.2). Allow it to cool to room temperature for at least 45 min. Weigh the dish, with the lid and rod, to the nearest 1 mg. 9.2 Test portion Move th
34、e zinc oxide to one side of the prepared dish (9.1) by tilting. Place on the clear space approximately 1 g of the prepared sample (Clause 8). Replace the lid on the dish with the stirring rod on top. Weigh the dish, with the stirring rod on top, to the nearest 1 mg. 9.3 Determination of total solids
35、 content 9.3.1 Add 5 ml of water to the test portion in the dish (9.2). Using the stirring rod, thoroughly mix the diluted test portion and the zinc oxide. Spread the mixture evenly over the bottom of the dish. Leave the stirring rod with the flattened end used for mixing resting in the mixture and
36、the other end resting on the rim of the dish. 9.3.2 Heat the dish on the boiling water bath or steam bath (6.5), ensuring that the maximum possible area of the dish is exposed to the steam. Continue the heating process for approximately 30 min, with frequent mixing of the contents of the dish during
37、 the early drying stage, so as to obtain maximum liquid evaporation. 9.3.3 Remove the dish from the water bath or steam bath and wipe its base to remove any water. Leave the stirring rod in the dish and then place it, together with the lid by its side, in the drying oven (6.3) set at 102 C for 3 h.
38、Then cover the dish with its lid and immediately transfer to the desiccator (6.2). 9.3.4 Allow the dish and contents to cool in the desiccator to the temperature of the weighing room for at least 45 min. Weigh the dish and contents to the nearest 1 mg. 9.3.5 Again, heat the dish and its contents, to
39、gether with its lid, for a further 1 h, as described in 9.3.3. Cover the dish with its lid and immediately transfer it to the desiccator (6.2). Allow to cool as in 9.3.4. Weigh the dish and its lid, to the nearest 1 mg. 9.3.6 Repeat this heating and weighing procedure (9.3.5) until the mass of the d
40、ish with its lid decreases by 1,0 mg or less, or increases between two successive weighings. Take the lowest mass recorded for the calculation. 9.4 Determination of lactic acid content In order to compensate for the water loss as a result of neutralizing the yogurt by means of zinc oxide, determine,
41、 in accordance with ISO 11869, the titratable acidity of the test sample (expressed as grams of lactic acid per 100 g of product). ISO 13580:2005(E) IDF 151:2005(E) 4 ISO and IDF 2005 All rights reserved10 Calculation and expression of results 10.1 Calculation Calculate the total solids content of t
42、he test sample, w, expressed as a percentage by mass, by using the following equation: 20 10 () 100 (0,1 ) () mm wa mm = + where m 0is the mass of the dish (including zinc oxide), lid and stirring rod (9.1), in grams; m 1is the mass of the dish (including zinc oxide), lid, stirring rod and test port
43、ion (9.2), in grams; m 2is the mass of the dish, lid, stirring rod and dried test portion (including zinc oxide) (9.3.6), in grams; a is the titratable acidity obtained in 9.4, expressed as grams of lactic acid per 100 g of product; 0,1 is the correction value to compensate for the loss of water as
44、a result of neutralizing the acidity of yogurt with zinc oxide (9.3.1). 10.2 Expression of results Report the test result to two decimal places. 11 Precision 11.1 Interlaboratory test Details of an interlaboratory test on the precision of the method are summarized in Annex A. The values derived from
45、 this interlaboratory test may not be applicable to concentration ranges and matrices other than those given. 11.2 Repeatability The absolute difference between two independent single test results, obtained with the same method on identical test material in the same laboratory by the same operator u
46、sing the same equipment within a short interval of time, will in not more than 5 % of cases be greater than 0,28 %. 11.3 Reproducibility The absolute difference between two single test results, obtained with the same method on identical test material in different laboratories by different operators
47、using different equipment, will in not more than 5 % of cases be greater than 0,45 %. ISO 13580:2005(E) IDF 151:2005(E) ISO and IDF 2005 All rights reserved 512 Test report The test report shall specify: a) all information necessary for the complete identification of the sample; b) the sampling meth
48、od used, if known; c) the test method used with reference to this International Standard; 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 results; e) the test results obtained an
49、d, if the repeatability has been checked, the final quoted result obtained. ISO 13580:2005(E) IDF 151:2005(E) 6 ISO and IDF 2005 All rights reservedAnnex A (informative) Interlaboratory test An international collaborative test (see Reference 4) involving eight laboratories was carried out on eight yogurts. The Swiss Dairy Research Institute organized the test. The results obtained were subjected to statistical analysis in accordance with ISO 5725-1 and ISO 5725-2 to give the precision data shown in Tabl
