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1、 Reference number ISO 8292-1:2008(E) ISO 2008 INTERNATIONAL STANDARD ISO 8292-1 First edition 2008-04-01 Animal and vegetable fats and oils Determination of solid fat content by pulsed NMR Part 1: Direct method Corps gras dorigines animale et vgtale Dtermination de la teneur en corps gras solides pa
2、r RMN pulse Partie 1: Mthode directe Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) PDF disc
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5、he file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROT
6、ECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs m
7、ember body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reserved Copyright International Organization for Standardization Pr
8、ovided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) ISO 2008 All rights reserved iii Contents Page Foreword iv 1 Scope 1 2 Normative references1 3 Terms and
9、 definitions .1 4 Symbols and abbreviated terms 2 5 Principle3 6 Apparatus .3 7 Sampling.5 8 Procedure .5 8.1 Measurement protocol and test sample5 8.2 Oven, water baths and temperature-controlled blocks .7 8.3 Determination of the conversion factor (where necessary)7 8.4 NMR spectrometer.8 8.5 Fill
10、ing the measurement tubes.8 8.6 Removing the thermal history8 8.7 Equilibrating at the initial temperature8 8.8 Crystallization and tempering 9 8.9 Measuring the SFC 9 8.10 Number of determinations10 8.11 Cleaning the measurement tubes10 9 Expression of results 10 10 Precision.11 10.1 Interlaborator
11、y test11 10.2 Repeatability.11 10.3 Reproducibility.11 11 Test report12 Annex A (informative) Results of interlaboratory tests.13 Annex B (informative) Theory of the direct method 23 Annex C (informative) Additional measurement protocols25 Bibliography27 Copyright International Organization for Stan
12、dardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) iv ISO 2008 All rights reserved Foreword ISO (the International Organization for Standardi
13、zation) 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 been established has the right to b
14、e 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 standardization. International Standa
15、rds 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 voting. Publication as an Inter
16、national 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 such patent rights. ISO 8292-1
17、was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11, Animal and vegetable fats and oils. This part of ISO 8292, together with ISO 8292-2, cancel and replace ISO 8292:1991. ISO 8292 consists of the following parts, under the general title Animal and vegetable fats and oil
18、s Determination of solid fat content by pulsed NMR: Part 1: Direct method Part 2: Indirect method Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitt
19、ed without license from IHS -,-,- INTERNATIONAL STANDARD ISO 8292-1:2008(E) ISO 2008 All rights reserved 1 Animal and vegetable fats and oils Determination of solid fat content by pulsed NMR Part 1: Direct method 1 Scope This part of ISO 8292 specifies a direct method for the determination of solid
20、fat content in animal and vegetable fats and oils (hereafter designated “fats”) using low-resolution pulsed nuclear magnetic resonance (NMR) spectrometry. Two alternative thermal pre-treatments are specified: one for general purpose fats not exhibiting pronounced polymorphism and which stabilize mai
21、nly in the -polymorph; and one for fats similar to cocoa butter which exhibit pronounced polymorphism and stabilize in the -polymorph. Additional thermal pre-treatments, which may be more suitable for specific purposes, are given in an informative annex. The direct method is easy to carry out and is
22、 reproducible, but is not as accurate as the indirect method due to the approximate method of calculation. NOTE An indirect method is specified in ISO 8292-2. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only
23、the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 661, Animal and vegetable fats and oils Preparation of test sample ISO 8292-2, Animal and vegetable fats and oils Determination of solid fat content by pulsed NMR
24、Part 2: Indirect method 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 solid fat content SFC ratio as a percentage of the number of protons in the solid phase to the number of protons in the solid and liquid phase at a specified temperature
25、NOTE SFC expressed on this basis is taken to be numerically equivalent to the percentage mass fraction of fat in the solid state. No correction is made for the different densities of protons in the solid and liquid phases, because this would require exact knowledge of the composition of the solid an
26、d liquid phases of the fat blends at each temperature. Regardless of any other systematic errors, this means that SFC values obtained by this method are about 0,5 % to 1,0 % higher than the true solid fat percentage mass fraction. Copyright International Organization for Standardization Provided by
27、IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) 2 ISO 2008 All rights reserved 3.2 liquid fat content percentage mass fraction of fat in the liquid state at a spe
28、cified temperature NOTE The liquid fat content is equal to 100 wSFC, where wSFC is the solid fat content. 3.3 tempering thermal treatment of the fat, after crystallization and prior to equilibration at the measurement temperature, which consists of holding the fat at a specified temperature for a sp
29、ecified time to transform the fat to a desired polymorph, and/or to ensure that a desired phase equilibrium has been achieved and/or to ensure that crystallization is complete 3.4 measurement temperature temperature at which the solid fat content is determined 3.5 repetition time interval between su
30、ccessive pulses 3.6 dead time time during which the instrument receiver is unable to record the decay signal NOTE Dead time is usually less than 10 s after the pulse. 3.7 measurement protocol complete description of the solid fat content determination specifying application, instrumental conditions,
31、 method, tempering, and whether measurements are in series or in parallel NOTE Measurement protocols are listed in Table 1 and Annex C. 4 Symbols and abbreviated terms f conversion (extrapolation) factor to correct the NMR signal observed at 11 s to that at time zero np number of pulses S1 magnetiza
32、tion decay signal measured at about 11 s S2 magnetization decay signal measured at about 70 s SFC solid fat content SL magnetization decay signal corresponding to the liquid phase SS magnetization decay signal corresponding to the solid phase SS+L magnetization decay signals corresponding to both so
33、lid plus liquid phases trep repetition time wSFC,i “true” SFC (measured in accordance with ISO 8292-2) wSFC,T SFC at measurement temperature, T Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 02:
34、19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) ISO 2008 All rights reserved 3 5 Principle The sample is tempered to a stable state at a specific temperature and then heated to, and stabilized at, the measurement temperature. Unless otherwise specif
35、ied, measurement temperatures can be any or all of: 0 C; 5 C; 10 C; 15 C; 20 C; 25 C; 27,5 C; 30 C; 32,5 C; 35 C; 37,5 C; 40 C; 45 C; 50 C; 55 C; 60 C. After electromagnetic equilibration in the static magnetic field of the NMR spectrometer and application of a 90 radio frequency pulse, the magnetiz
36、ation decay signals from the protons in the solid and liquid phases are recorded at about 11 s and about 70 s (or at times recommended by the spectrometer manufacturer, see 6.1). SFC is then calculated. Measurements may be made in series or in parallel. One tube is filled from each test sample when
37、making measurements in series. After tempering as required and holding at 0 C, the measurement tube is moved to the first measurement temperature, held for the specified time, the SFC measured, and then moved to the second measurement temperature, and so on. Thus, only one tube is required for all t
38、est samples, regardless of how many measurement temperatures are used. However, the SFC recorded at a given measurement temperature depends on the preceding measurement temperatures and times. As many measurement tubes are filled from each test sample as there are measurement temperatures when makin
39、g measurements in parallel. After tempering as required and holding at 0 C, each measurement tube is moved more or less simultaneously to each required measurement temperature and held for the specified time before measuring the SFC. Although more tubes are required for measurement in parallel than
40、with that in series, each wSFC,T determination is independent of other determinations. Additionally, the total time for the measurements is significantly shortened. EXAMPLE For a holding time of 90 min at 0 C and holding times of 60 min at measurement temperatures of 10 C, 20 C, 30 C, and 40 C, the
41、series measurement would take 5,5 h, whereas the parallel measurement would take 2,5 h. 6 Apparatus 6.1 Pulsed nuclear magnetic resonance spectrometer, low resolution The NMR spectrometer shall have: a) a magnet with a sufficiently uniform field to ensure that the half-life of the magnetization of a
42、 reference sample of liquid fat is longer than 1 000 s; b) a measurement dead time plus pulse width of less than 10 s; c) an automatic measuring device which operates as soon as the measurement tubes (6.2.1) are inserted; d) an adjustable measurement repetition time; e) a 10 mm measurement cell/prob
43、e for measurement tubes which is temperature controlled at 40 C. For exact magnetization decay signal times, refer to spectrometer manufacturers instructions; these are normally at about 11 s and about 70 s and should not need to be altered by the user. For preference, the instrument should be equip
44、ped with a computer which automatically takes the required measurements, performs the required calculations and presents the results directly on the computer screen or other display. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Boeing Co/59
45、10770001 Not for Resale, 07/25/2008 02:19:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 8292-1:2008(E) 4 ISO 2008 All rights reserved 6.2 Tubes 6.2.1 Measurement tubes, of glass with plastic caps, with outer diameter (10 0,25) mm, wall thickness (0,9 0,25) mm, and
46、length at least 150 mm, or as specified by the NMR spectrometer manufacturer. 6.2.2 Calibration tubes, of known instrument response to calibrate the spectrometer and to check the direct method. NOTE Plastic-in-oil calibration materials with known responses, giving an f factor in the range 1,4 to 1,4
47、5 appropriate for the instrument and for use with the non-stabilizing direct and other protocols (see Table 1 and Annex C) are supplied by the instrument manufacturer in standard measurement tubes. Materials giving SFC mass fractions of 0 %, about 30 % and about 70 % are suitable. These values are i
48、ndependent of temperature. The calibration tubes need re-calibration at intervals as specified by the supplier.1) 6.3 Temperature-maintenance equipment 6.3.1 General In principle, temperature-controlled blocks (6.3.3) have advantages over water baths (6.3.2) because the tubes can never come into contact with water. In practice, as with aluminium blocks in water baths, the tubes can take a significant time to come to the set temperature. Heat transfer can be improved