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1、 Reference numbers ISO 21543:2006(E) IDF 201:2006(E) ISO and IDF 2006 INTERNATIONAL STANDARD ISO 21543 IDF 201 First edition 2006-09-01 Milk products Guidelines for the application of near infrared spectrometry Produits laitiers Lignes directrices pour lapplication de la spectromtrie dans le proche
2、infrarouge ISO 21543:2006(E) IDF 201:2006(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 perfo
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5、ating to it is found, please inform the ISO Central Secretariat at the address given below. ISO and IDF 2006 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 mi
6、crofilm, 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 2 733 98 88 Fax + 41 22 7
7、49 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 2006 All rights reserved ISO 21543:2006(E) IDF 201:2006(E) ISO and IDF 2006 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Terms a
8、nd definitions. 1 3 Principle. 1 4 Reagents 1 5 Apparatus 2 6 Calibration and initial validation . 2 6.1 Selection of calibration samples. 2 6.2 Reference analyses and NIR measurements. 3 6.3 Calibration . 3 6.4 Outliers in calibration. 4 6.5 Validation of calibration models . 5 6.6 Changes in measu
9、ring and instrument conditions. 6 6.7 Outlier detection . 6 7 Statistics for performance measurement. 6 7.1 Standard error of prediction (SEP) and bias 6 7.2 Root mean square error of prediction (RMSEP) 7 7.3 Root mean square error of cross validation (RMSECV). 7 8 Sampling 7 9 Procedure 8 9.1 Prepa
10、ration of test sample. 8 9.2 Measurement. 8 9.3 Evaluation of results. 8 10 Checking instrument stability . 9 10.1 Control sample 9 10.2 Instrument diagnostics 9 11 Running performance check of calibration 9 12 Precision and accuracy 10 12.1 Repeatability 10 12.2 Intralaboratory reproducibility 10 1
11、2.3 Accuracy 11 13 Test report . 11 Annex A (informative) Examples of SEP and RMSEP values 12 Annex B (informative) Examples of figures. 14 Bibliography. 22 -,-,- ISO 21543:2006(E) IDF 201:2006(E) iv ISO and IDF 2006 All rights reserved Foreword ISO (the International Organization for Standardizatio
12、n) 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 be rep
13、resented 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 Standards a
14、re 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 Internatio
15、nal 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 21543IDF 201
16、 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. ISO 21543:2006(E) IDF 201:2006(E) ISO and IDF 2006 All rights reserved v Foreword IDF (the Internation
17、al Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every 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 in the development of standard meth
18、ods 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 Committees
19、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 21543IDF 201 was prepared by the International Dairy Federation (IDF) and Technic
20、al 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 Joint ISO-IDF Action Team on Automated methods, of the Standing Committee on Quality assurance, statistics of analytical data and sampling, unde
21、r the aegis of its project leader, Mr L.K. Srensen (DK). -,-,- -,-,- INTERNATIONAL STANDARD ISO 21543:2006(E) IDF 201:2006(E) ISO and IDF 2006 All rights reserved 1 Milk products Guidelines for the application of near infrared spectrometry 1 Scope This International Standard provides guidance on use
22、 of near infrared spectrometry in the determination of the total solids, fat and protein contents in cheese, the moisture, fat, protein and lactose contents in dried milk, dried whey and dried butter milk, and the moisture, fat, non-fat solids and salt contents in butter. 2 Terms and definitions For
23、 the purposes of this document, the following terms and definitions apply. 2.1 near infrared instrument NIR instrument proprietary apparatus which, when used under the conditions defined in this International Standard, estimates the mass fractions of the substances specified in Clause 1 2.2 total so
24、lids, moisture, non-fat solids, fat, protein, lactose and salt contents mass fraction of substances determined using the method specified in this International Standard NOTE These contents are expressed as mass fractions in percent. 3 Principle The sample is pretreated to obtain a homogeneous test s
25、ample representing the chemical composition of the sample material. It is loaded into the sample holder of the NIR spectrometer. The absorbance at wavelengths in the near infrared region is measured and the spectral data are transformed to constituent concentrations by calibration models developed o
26、n representative samples from the population to be tested. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 4.1 Ethanol, or other appropriate solvent or detergent mixture, for cleaning re-usab
27、le sample cups. ISO 21543:2006(E) IDF 201:2006(E) 2 ISO and IDF 2006 All rights reserved 5 Apparatus 5.1 Near-infrared (NIR) instrument, based on diffuse reflectance or transmittance measurement in the whole near infrared wavelength region of 700 nm to 2 500 nm or segments of this or at selected wav
28、elengths. The optical operation principle may be dispersive (e.g. grating monochromators), interferometric or non- thermal (e.g. light-emitting diodes, laser diodes and lasers). The instrument should be provided with a diagnostic test system for testing photometric instrument noise, wavelength accur
29、acy and wavelength precision (for scanning spectrophotometers). The wavelength accuracy should be better than 0,5 nm and the repeatability standard deviation better than 0,02 nm. The instrument should be equipped with a sample holder, which allows measurement of a sufficiently large sample volume or
30、 surface to eliminate any significant influence of inhomogeneity derived from the chemical composition or physical properties of the test sample. The sample path length (sample thickness) in transmittance measurements should be optimized according to the manufacturers recommendations with respect to
31、 signal intensity for obtaining linearity and maximum signal/noise ratio. In reflectance measurements, a quartz window or other appropriate material to eliminate drying effects should preferably cover the interacting sample surface layer. The sample cup (cuvette) may be re-usable or made of disposab
32、le material. 5.2 Grinding or grating device, appropriate for preparing the sample (e.g. a food processor for semi-hard cheese). Changes in grinding or grating conditions may influence the NIR measurements. 6 Calibration and initial validation 6.1 Selection of calibration samples The instrument shoul
33、d be calibrated before being used. Because of the complex nature of near infrared spectral data, which are mainly overtones and combination bands of fundamental vibrations in the mid- infrared region, the instrument should be calibrated using a series of natural samples (often at least 120 samples).
34、 The accuracy and robustness of calibration models are dependent on the strategies used for sample selection and calibration. Developed calibration models are only valid for samples covered by the domain of the calibration samples. The first step in calibration development is therefore to define the
35、 application (e.g. sample types and concentration ranges). When calibration samples are selected, care should be taken to ensure that all major factors affecting the accuracy of calibration are covered within the limits of the defined application area. These factors include the following: a) combina
36、tions and composition ranges of major and minor sample components: analytes (e.g. total solids, fat and protein) and non-analytes; b) seasonal, geographic and genetic effects on milk composition; c) processing techniques and conditions; d) ripening stages of cheeses; e) storage and storage condition
37、s. ISO 21543:2006(E) IDF 201:2006(E) ISO and IDF 2006 All rights reserved 3 The accuracy of calibration is influenced by the extent of variation in the sample material and the analyte concentration range. A moderate variation is usually easier to fit than a large variation. If the required accuracy
38、cannot be obtained by a single calibration, then the application area should be split up into static or dynamic sub-areas, each with an associated calibration, in order to fulfil the requirements. Dynamic sub-areas are used in locally weighted regression algorithms where calibration samples close in
39、 spectral space to the actual prediction sample are selected from a larger population to create a local calibration equation. It is generally preferable that the whole calibration range be covered in a uniform way, with samples from low to high concentrations of analytes. The sample spread should al
40、so be as uniform as possible with respect to the other variables, including those mentioned above. Furthermore, the samples should be collected and measured over a certain period of time to ensure inclusion of time-dependent effects. This design will improve the ruggedness and give a more even perfo
41、rmance of the calibration over the entire analyte concentration range. Multivariate methods 1, 2 may be used as a tool in the selection of samples to ensure a homogeneous calibration set covering all variation in spectroscopic data induced by chemical, biological and physical factors without duplica
42、tion of samples with similar information. In practice, a larger sample population is measured by NIR spectroscopy for collection of NIR data only. Then samples differing in spectral information are selected for reference analyses. Identification of differing samples may be obtained from inspection o
43、f score plots from principal component analysis (PCA) using, for example, the first three components. This may be less practical in the case of many samples. However, it is recommended always to perform a PCA and inspect score plots to obtain a visual overview of the sample set. More formal cluster
44、analyses may be obtained using techniques based on distance measurements 2. Further samples may be added over a period of time to this pool of selected samples using PCA space or distance measurement to identify differing samples. 6.2 Reference analyses and NIR measurements Internationally accepted
45、reference methods for the determination of analytes should be used. The reference method used for calibration should be in statistical control; i.e. the variability should consist of a constant system of random variations. To support assessment of outliers, it may be useful to perform replicate anal
46、yses in independent series (different analysts, different equipment, etc.). All major variations in NIR measuring conditions that may appear in practice should be built into the calibration model. An important factor is sample temperature. The sampling procedure used and the sample size measured by
47、NIR spectroscopy may be critical for the accuracy obtained 3. The test sample volume or surface interacting in measurements should be large enough to avoid sample inhomogeneity having a significant influence. Reflectance measurement at higher wavelengths normally requires a larger sample surface tha
48、n transmittance measurement at shorter wavelengths because the light penetration is much less. The optimal sample size should be determined from experiments where the prepared sample material (see 9.1) is measured repeatedly after repacking of the sample cup. Special care should be taken to avoid su
49、rface drying effects, particularly in reflectance measurements. The NIR measurements and reference analyses should preferably be performed on the same test sample in order to eliminate effects related to sampling uncertainty. The NIR measurements and the initiation of reference analyses should also be performed with a minimum time lag (preferably less than one day). It is good practice to randomi