1、May 2011 Translation by DIN-Sprachendienst.English price group 11No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 67
2、.200.10!$o)“1760694www.din.deDDIN EN ISO 3656Animal and vegetable fats and oils Determination of ultraviolet absorbance expressed as specific UVextinction (ISO 3656:2011)English translation of DIN EN ISO 3656:2011-05Tierische und pflanzliche Fette und le Bestimmung der Ultraviolett-Absorption, ausge
3、drckt als spezifische UV-Extinktion(ISO 3656:2011)Englische bersetzung von DIN EN ISO 3656:2011-05Corps gras dorigines animale et vgtale Dtermination de labsorbance dans lultraviolet, exprime sous la forme dextinctionspcifique en lumire ultraviolette (ISO 3656:2011)Traduction anglaise de DIN EN ISO
4、3656:2011-05SupersedesDIN EN ISO 3656:2002-07www.beuth.deDocument comprises pagesIn case of doubt, the German-language original shall be considered authoritative.1604.11 DIN EN ISO 3656:2011-05 2 A comma is used as the decimal marker. National foreword This standard has been prepared by Technical Co
5、mmittee ISO/TC 34 “Food products” (Secretariat: AFNOR, France) in collaboration with Technical Committee CEN/TC 307 “Oilseeds, vegetable and animal fats and oils and their by-products Methods of sampling and analysis” (Secretariat: AFNOR, France). The responsible German bodies involved in its prepar
6、ation were the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee) and the Deutsche Gesell-schaft fr Fettwissenschaft DGF (German Fat Research Society), Joint Committee NA 057-05-05 AA Gemein-schaftsausschuss fr die Analytik von Fetten,
7、len, Fettprodukten, verwandten Stoffen und Rohstoffen. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO 661 DIN EN ISO 661 ISO 1042 DIN EN ISO 1042 ISO 5555 DIN EN ISO 5555 ISO 5725-1 DIN ISO 5725-1 ISO 5725-2 DIN ISO 5725-2 Amendments T
8、his standard differs from DIN EN ISO 3656:2002-07 as follows: a) an Introduction has been added; b) Clause 3 “Terms and definitions” has been added; c) Clause 4 “Principle” has been revised; d) a measurement range for the solvent cyclohexane has been specified (5.1); e) the upper limit of the wavele
9、ngth range for glassware used has been changed from 320 nm to 360 nm (Clause 6); f) requirements for an analytical balance have been included (6.2); g) requirements for the wavelength scale (6.3.2) and the absorbance scale (6.3.3) of the spectrometer have been revised; h) Clause 8 “Preparation of te
10、st sample” has been revised; i) Subclause 9.1 “Test portion and preparation of the test solution” has been revised; j) the equation for the calculation of the specific extinction has been modified (10.1); k) Subclause 10.2 “Variation of the specific extinction, K” has been added; l) requirements for
11、 repeatability (11.2) and reproducibility (11.3) have been revised; m) the interlaboratory test results of 1998 have been replaced by the results of an interlaboratory test carried out in 2009 (Annex A); DIN EN ISO 3656:2011-05 3 n) the former Annex ZA relating to normative references to internation
12、al publications has been deleted; o) the standard has been editorially revised. Previous editions DIN EN ISO 3656: 2002-07 National Annex NA (informative) Bibliography DIN EN ISO 661, Animal and vegetable fats and oils Preparation of test sample DIN EN ISO 1042, Laboratory glassware One-mark volumet
13、ric flasks DIN EN ISO 5555, Animal and vegetable fats and oils Sampling DIN ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions DIN ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic m
14、ethod for the determination of repeatability and reproducibility of a standard measurement method DIN EN ISO 3656:2011-05 4 This page is intentionally blank EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 3656 February 2011 ICS 67.200.10 Supersedes EN ISO 3656:2002English Version Animal and
15、 vegetable fats and oils - Determination of ultraviolet absorbance expressed as specific UV extinction (ISO 3656:2011) Corps gras dorigines animale et vgtale - Dtermination de labsorbance dans lultraviolet, exprime sous la forme dextinction spcifique en lumire ultraviolette (ISO 3656:2011) Tierische
16、 und pflanzliche Fette und le - Bestimmung der Ultraviolett-Absorption, ausgedrckt als spezifische UV-Extinktion (ISO 3656:2011) This European Standard was approved by CEN on 22 January 2011. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for
17、 giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three
18、 official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodi
19、es of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kin
20、gdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 3656:2011: ECo
21、ntents Page Foreword3 Introduction .4 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 4 Principle5 5 Reagents.5 6 Apparatus .6 7 Sampling.6 8 Preparation of test sample6 9 Procedure .7 9.1 Test portion and preparation of the test solution 7 9.2 Determination.7 10 Expression of results
22、7 10.1 Specific extinction (extinction coefficients) at a specific wavelength.7 10.2 Variation of the specific extinction, .8 11 Precision.8 11.1 Interlaboratory test 8 11.2 Repeatability.8 11.3 Reproducibility.8 12 Test report 8 Annex A (informative) Results of interlaboratory test.9 Bibliography 1
23、2 DIN EN ISO 3656:2011-05 EN ISO 3656:2011 (E) 2 Foreword This document (EN ISO 3656:2011) has been prepared by Technical Committee ISO/TC 34 “Food products” in collaboration with Technical Committee CEN/TC 307 “Oilseeds, vegetable and animal fats and oils and their by-products Methods of sampling a
24、nd analysis” the secretariat of which is held by AFNOR. 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 August 2011, and conflicting national standards shall be withdrawn at the latest by August 2
25、011. 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. This document supersedes EN ISO 3656:2002. According to the CEN/CENELEC Internal
26、Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg
27、, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 3656:2011 has been approved by CEN as a EN ISO 3656:2011 without any modification. DIN EN ISO 3656:2011-05 EN ISO 3656:2011 (E) 3 Introdu
28、ction This International Standard describes a method for the determination of the absorbance of light in the ultraviolet (UV) spectrum by fats and oils. Changes in absorption in the UV region are used as quality, purity, and authenticity criteria for fats and oils. Refining causes the formation of c
29、onjugated dienes and trienes and increased values of K232and K268, which then indicate the presence of refined oils. The oxidation of linoleic and linolenic acids results in the formation of hydroperoxides in which the double bonds become conjugated. Furthermore, the formation of either carbon-carbo
30、n bonds or carbon-oxygen bonds (,-unsaturated carbonyl compounds) as secondary autoxidation products are observed. These compounds all lead to an increase of the absorption in the region between 225 nm and 325 nm. The third edition of this International Standard allowed the determination of the UV a
31、bsorbance at 232 nm and 268 nm using three different solvents (isooctane, cyclohexane or n-hexane). However, it is known that the solvents themselves have an effect on the UV absorbance between 260 nm and 276 nm in vegetable oils. Recent investigations have shown that the measurement of K268and K270
32、for the same oil in isooctane or in cyclohexane give significantly different results. In isooctane, the maxima appear at 267 nm to 268 nm whereas in cyclohexane, the maxima appear at 268 nm to 269 nm. In the IOC standards for the determination of the ultraviolet absorbance of (virgin) olive oils, th
33、e specified wavelengths are 232 nm and 270 nm. Taking into account the above, the fourth edition of this International Standard specifies measurement at 268 nm when isooctane is used and measurement at 270 nm when cyclohexane is used. Moreover, the variation of the specific extinction, , for olive o
34、ils has been introduced. Precision data from a new collaborative trial have also been taken into consideration for this revision. DIN EN ISO 3656:2011-05 EN ISO 3656:2011 (E) 4 1 Scope This International Standard specifies a method for the determination of the absorbance at ultraviolet wavelengths o
35、f animal and vegetable fats and oils. 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 document (including any amendment
36、s) applies. ISO 661, Animal and vegetable fats and oils Preparation of test sample 3 Terms and definitions NOTE The usual policy of ISO/TC 34/SC 11 of using symbols specified in International Standard 800005is not followed in this International Standard. The symbols are those used, for example, in C
37、ommission Regulation (EEC) No 2568/916. For the purposes of this document, the following terms and definitions apply. 3.1 specific extinction (K232 K268 K270) absorbance of 1 g sample, dissolved in 100 ml isooctane or cyclohexane, measured in a 10 mm cell at the specific wavelengths 232 nm, 268 nm,
38、and 270 nm 4 Principle A sample is dissolved in isooctane or cyclohexane and the absorbance is measured spectrophotometrically in a specified ultraviolet wavelength range. The specific absorbance at 232 nm and 268 nm in isooctane or 232 nm and 270 nm in cyclohexane for a concentration of 1 g per 100
39、 ml in a 10 mm cell is calculated. 5 Reagents WARNING Attention is drawn to the regulations which specify the handling of hazardous substances. Technical, organizational and personal safety measures shall be followed. During the analysis, unless otherwise stated, use only reagents of recognized anal
40、ytical grade and distilled or demineralized water or water of equivalent purity. 5.1 Solvent: isooctane (2,2,4-trimethylpentane) for the measurement at 232 nm and 268 nm or cyclohexane for the measurement at 232 nm and 270 nm, having an absorbance less than 0,12 at 232 nm and less than 0,05 at 250 n
41、m against water, measured in a 10 mm cell. DIN EN ISO 3656:2011-05 EN ISO 3656:2011 (E) 5 6 Apparatus The glassware used for the determination shall be thoroughly cleaned and rinsed with the solvent (5.1) before use so that it is free from impurities having an absorbance within the wavelength range
42、of 220 nm to 360 nm. Usual laboratory apparatus and, in particular, the following. 6.1 One-mark volumetric flasks, capacity 25 ml, ISO 10421class A. 6.2 Analytical balance, capable of being read to the nearest 0,000 1 g. 6.3 Spectrometer, with quartz cells of pathlength 10 mm, suitable for measureme
43、nts at ultraviolet wavelengths (220 nm to 360 nm). 6.3.1 General. Before use it is recommended that the wavelength and absorbance scales of the spectrometer be checked as specified in 6.3.2 and 6.3.3. 6.3.2 Wavelength scale. Check this using a reference material consisting of an optical glass filter
44、 containing holmium oxide which has distinct absorption bands. The reference material is designed for the verification and calibration of the wavelength scales of visible and ultraviolet spectrophotometers having nominal spectral bandwidths of 5 nm or less. The holmium glass filter is measured in th
45、e absorbance mode against an air blank, over the wavelength range 640 nm to 240 nm. For each spectral bandwidth (0,10, 0,25, 0,50, 1,00, 1,50, 2,00, and 3,00), a baseline correction is performed with an empty cell holder. The wavelengths of the spectral bandwidth are listed in the certificate of the
46、 reference material1). 6.3.3 Absorbance scale. This may be checked using a reference material consisting of four solutions of potassium dichromate in perchloric acid sealed in far UV quartz cells to measure the linearity and photometric accuracy reference in the UV. The potassium dichromate filled c
47、ells (40 mg/ml, 60 mg/ml, 80 mg/ml and 100 mg/ml) are measured against a perchloric acid blank (see Reference 7). The net absorbance values are listed in the certificate of the reference material1). 7 Sampling Sampling is not part of the method specified in this International Standard. A recommended
48、 sampling method is given in ISO 55552. It is important the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage. 8 Preparation of test sample Prepare the test sample in accordance with ISO 661. Ensure that the test sample is perfectly ho
49、mogeneous and contains no suspended impurities. Filter oils which are liquid at ambient temperature through paper at a temperature of approximately 30 C. Homogenize and filter hard fats at a temperature of not more than 10 C above their melting point. 1) Suitable holmium filters and potassium dichromate-sealed cells are available commercially, e.g. from Starna Scientific (). This information is given for the convenience of users of this document and does not constitute an endorseme
