1、BS EN ISO5764:2009ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMilk Determinationof freezing point Thermistorcryoscope method(Reference method)(ISO 5764:2009)This British Standard was published under theauthority of the StandardsPolicy and Strate
2、gyCommittee on 31 July2009 BSI 2009ISBN 978 0 580 56764 3Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 5764:2009National forewordThis British Standard is the UK implementation of EN ISO 5764:2009. Itis identical to ISO 5764:2009. It supersedes BS EN ISO 5764:2002 whichis withd
3、rawn.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 be obtained onrequest to its secretary.This publication does not purport to include all the necessary provision
4、sof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 5764May 2009ICS 67.100.10 Supersedes EN ISO 5764:2002 English VersionMilk - Determination of freezin
5、g point - Thermistor cryoscopemethod (Reference method) (ISO 5764:2009)Lait - Dtermination du point de conglation - Mthode aucryoscope thermistance (Mthode de rfrence) (ISO5764:2009)Milch - Bestimmung des Gefrierpunktes - Thermistor-Kryoskop-Verfahren (Referenzverfahren) (ISO 5764:2009)This European
6、 Standard was approved by CEN on 13 April 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concernin
7、g such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own langu
8、age and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxem
9、bourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 2009 CEN All rights of
10、 exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 5764:2009: EBS EN ISO 5764:2009EN ISO 5764:2009 (E) 3 Foreword This document (EN ISO 5764:2009) has been prepared by Technical Committee ISO/TC 34 “Agricultural food products“ in collaboration with
11、Technical Committee CEN/TC 302 “Milk and milk products - Methods of sampling and analysis” the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2009, a
12、nd conflicting national standards shall be withdrawn at the latest by November 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. T
13、his document supersedes EN ISO 5764:2002. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany,
14、Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 5764:2009 has been approved by CEN as a EN ISO 5764:2009 without a
15、ny modification. BS EN ISO 5764:2009ISO 5764:2009(E) IDF 108:2009(E) ISO and IDF 2009 All rights reserved iiiContents Page Foreword iv Foreword. v 1 Scope 1 2 Normative references 1 3 Terms and definitions .1 4 Principle2 5 Reagents.2 6 Apparatus .3 7 Sampling.4 8 Calibration of the thermistor cryos
16、cope .4 9 Preparation of test sample5 9.1 Preparation .5 9.2 Sample condition.6 10 Procedure .6 10.1 Preliminary checks 6 10.2 Routine calibration check .6 10.3 Determination.6 11 Calculation and expression of results.7 11.1 Calculation7 11.2 Expression of results 7 12 Precision.7 12.1 Interlaborato
17、ry test 7 12.2 Repeatability.7 12.3 Reproducibility.7 13 Test report 8 Annex A (informative) Interlaboratory trial on bovine milk.9 Annex B (informative) Interlaboratory trial on raw ovine and caprine milk 11 Annex C (informative) Guidelines for the application of routine thermistor cryoscope method
18、s .13 Annex D (informative) Adjustment of the freezing point value used as the reference for genuine milk16 Bibliography 17 BS EN ISO 5764:2009ISO 5764:2009(E) IDF 108:2009(E) iv ISO and IDF 2009 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide fede
19、ration 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 been established has the right to be represented on that commi
20、ttee. 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 standardization. International Standards are drafted in accordan
21、ce 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 voting. Publication as an International Standard requires
22、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 such patent rights. International Standard ISO 5764IDF 108
23、 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 third edition of ISO 5764IDF 108 cancels and replaces the second edition (ISO 5764IDF 108:2002),
24、the scope of which has been technically revised. BS EN ISO 5764:2009ISO 5764:2009(E) IDF 108:2009(E) ISO and IDF 2009 All rights reserved vForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committ
25、ees 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 me
26、thods of analysis and sampling for milk and milk products. 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 % of the IDF National Committee
27、s 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. International Standard ISO 5764IDF 108 was prepared by Technical Committee ISO/TC 3
28、4, 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 IDF-ISO Action Team on Water, of the Standing Committee on Main components in milk, under the aegis of its pr
29、oject leader, Mrs. S. Orlandini (IT). This edition of ISO 5764IDF 108 cancels and replaces ISO 5764IDF 108:2002, the scope of which has been technically revised. BS EN ISO 5764:2009BS EN ISO 5764:2009INTERNATIONAL STANDARD ISO 5764:2009(E)IDF 108:2009(E) ISO and IDF 2009 All rights reserved 1Milk De
30、termination of freezing point Thermistor cryoscope method (Reference method) 1 Scope This International Standard specifies a reference method for the determination of the freezing point of raw bovine milk, heat-treated whole, reduced fat and skimmed bovine milk, as well as raw ovine and caprine milk
31、, by using a thermistor cryoscope. The freezing point can be used to estimate the proportion of extraneous water in milk. Calculation of the amount of extraneous water is subject to daily and seasonal variations, and is not within the scope of this International Standard. Results obtained from sampl
32、es with a titratable acidity exceeding 20 ml of 0,1 mol/l sodium hydroxide solution per 10 g of non-fat solids are not representative of the original milk. NOTE 1 Sterilization and vacuum pasteurization can affect the freezing point of milk (see Reference 5). NOTE 2 The method uses plateau-timed ins
33、truments. For routine measurements, other thermistor cryoscope methods, i.e. fixed time procedures, can be used. Guidelines for the application of other procedures are given in Annex C. NOTE 3 The limit value mentioned for the titratable acidity in Clause 1 and 9.2 applies to bovine milk. It is poss
34、ible that the limit values for ovine and caprine milk are higher. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced docum
35、ent (including any amendments) applies. ISO 3696, Water for analytical laboratory use Specification and test methods ISO 6091, Dried milk Determination of titratable acidity (Reference method) 1)3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1
36、 freezing point of milk temperature value obtained using the method specified in this International Standard NOTE The freezing point is expressed in millidegrees Celsius. 1) Equivalent to IDF 86. BS EN ISO 5764:2009ISO 5764:2009(E) IDF 108:2009(E) 2 ISO and IDF 2009 All rights reserved4 Principle A
37、test sample of milk is supercooled to an appropriate temperature. Crystallization is induced by means sufficient to cause an instantaneous release of heat with an accompanying warming of the sample to a temperature plateau. The plateau is reached when the temperature rise has not exceeded 0,5 mC ove
38、r the previous 20 s. The temperature thus attained corresponds to the freezing point of the test sample. The instrument is calibrated by adjusting it to give the correct readings for two sodium chloride standard solutions, using the same procedure as for test portions of milk. 5 Reagents During the
39、analysis, unless otherwise stated, use only reagents of recognized analytical grade. 5.1 Water, in accordance with ISO 3696 grade 2 or water of equivalent quality distilled from borosilicate glass apparatus. Boil the water and cool it to 20 C 2 C shortly before use. 5.2 Sodium chloride (NaCl), finel
40、y ground, dried in the electric furnace (6.7) at 300 C 25 C for 5 h or, alternatively, dried in the drying oven (6.8) at 130 C 2 C for at least 24 h, then cooled to room temperature in a desiccator (6.9). 5.3 Sodium chloride standard solutions. Preferably, make up the sodium chloride standard soluti
41、on on a gram per kilogram basis (see Table 1, leftmost column) by weighing the required amount of prepared dry sodium chloride (5.2) to the nearest 0,1 mg and dissolving it in 1 000 g 0,1 g of water (5.1). Store standard solutions at about 5 C in well-stoppered polyethylene bottles (6.10) of capacit
42、y not greater than 250 ml. Alternatively, weigh, to the nearest 0,1 mg, the appropriate amount (see Table 1, middle column) of prepared dry sodium chloride (5.2) in a weighing bottle (6.5). Dissolve in water (5.1) and transfer quantitatively to a 1 000 ml one-mark volumetric flask (6.6). Dilute to t
43、he 1 000 ml mark with water (5.1) at 20 C 2 C and mix. Table 1 Freezing point of sodium chloride standard solutions NaCl solution g/kg NaCl solution at 20 C g/l Freezing point mC 6,763 6,731 400,0 6,901 6,868 408,0 7,625 7,587 450,0 8,489 8,444 500,0 8,662 8,615 510,0 8,697 8,650 512,0 8,835 8,787 5
44、20,0 9,008 8,959 530,0 9,181 9,130 540,0 9,354 9,302 550,0 9,475 9,422 557,0 10,220 10,161 600,0 BS EN ISO 5764:2009ISO 5764:2009(E) IDF 108:2009(E) ISO and IDF 2009 All rights reserved 3Before using a standard solution, gently invert and rotate the bottle several times to mix its contents thoroughl
45、y. Do not agitate the standard solution violently at any time, as this can lead to incorporation of air. Pour samples of standard solutions from the bottles; never use pipettes for this purpose. Do not use standard solutions from bottles less than one-quarter full, or more than 2 months old, or cont
46、aining visible moulds. Only use unpreserved sodium chloride standard solutions for this reference method. For routine methods, sodium chloride standard solutions with a fungicidal or fungistatic agent may be used. For guidance, see Annex C. 6 Apparatus Usual laboratory apparatus and, in particular,
47、the following. 6.1 Cryoscope, consisting of a thermostatically controlled cooling device, a thermistor probe with associated circuit, a read-out device, a sample agitator and a crystallization device (see Figure 1). 6.1.1 Cooling device. Several types of thermostatically controlled cooling devices c
48、an be used, e.g.: a) immersion type: a cooling bath with a suitable buffer capacity; b) circulation type: a continuous stream of cooling liquid around the sample tube; c) cooling block type: a cooling block with a small amount of cooling liquid. After the initiation of freezing, keep the temperature
49、 of the cooling liquid around the sample tube constant at 7,0 C 0,5 C. NOTE A suitable cooling liquid is a 33 % (volume fraction) aqueous solution of propylene glycol. 6.1.2 Measuring device, associated circuitry and read-out device. The thermistor shall be of the glass probe type with diameter of 1,60 mm 0,4 mm and an electrical resistance of between 3 and 30 k at 0 C. The type and dimensions of the shank material (including a possible filler) shall not allow a heat transfer into the
