1、Foodstuffs Detection of irradiated food containing cellulose by ESR spectroscopy English version of DIN EN 1787 DIN EN 1787 - EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 1787 March 2000 ICs 67.050 Supersedes EN 1787 : 1996. English version Foodstuffs Detection of irradiated food containing
2、cellulose by ESR spectroscopy Produits alimentaires - Dtection par spectroscopie RPE daliments ioniss contenant de la cellulose Lebensmittel - ESR-spektro- skopischer Nachweis von bestrahlten cellulosehaltigen Lebensmitteln This European Standard was approved by CEN on 2000-02-21. CEN members are bo
3、und to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national stand- ards may be obtained on application to the
4、 Central Secretariat or to any CEN member. The European Standards exist in three 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 Central Secretariat has the same status
5、 as the official versions. CEN members are the national standards bodies of Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom. CEN European Commit
6、tee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 2000. CEN - All rights of exploitation in any form and by any means reserved worldwide for CEN national members. Ref. No. EN 1787 : 2000 E Page 2 EN 1787 :
7、 2000 Contents Page Foreword 2 Scope 3 Normative references . 3 Principle 3 Apparatus and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Procedure . 3 Evaluation . 4 Limitations . 5 Validation . 5 Test report 6 Annex
8、A (normative) Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Annex B (informative) Further information on the applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Bibliography . 7 Forewo
9、rd This European Standard has been prepared by Technical Committee CEN/TC 275 “Food analysis - Horizontal methods“, the secretariat of which is held by DIN. This European Standard supersedes EN 1787:1996. This European Standard shall be given the status of a national standard, either by publication
10、of an identical text or by endorsement, at the latest by September 2000, and conflicting national standards shall be withdrawn at the latest by September 2000. According to the CEWCENELEC internal Regulations, the national standards organizations of the following countries are bound to implement thi
11、s European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Gemany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Noway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. This drat European Standard was elaborated on the basis of a protocol developed follo
12、wing a concerted action supported by the Commission of European Union (XII C.5). Experts and laboratories from E.U. and ERA countries, contributed jointly to the development of this protocol. Page 3 EN 1787 : 2000 1 scope This draft European Standard specifies a method for the detection of foods con
13、taining cellulose which have been treated with ionizing radiation, by analysing the electron spin resonance (ESR) spectrum, also called electron paramagnetic resonance (EPR) spectrum, of the food, see I to 13. Interlaboratory studies have been successfully carried out with pistachio nut shells, 14 t
14、o (181, paprika powder, 19 and 20 and fresh strawberries 21. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereaf
15、ter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN IS0 3696 Water for analytical labo
16、ratory use - Specification and test methods (IS0 3696:1987) 3 Principle ESR spectroscopy detects paramagnetic centres (e.g. radicals). They are either due to irradiation or to other compounds present. An intense extemal magnetic field produces a difference between the energy levels of the electron s
17、pins m, = + Yb and m, = -?h, leading to resonance absorption of an applied microwave beam in the spectrometer. ESR spectra are conventionally displayed as the first derivative of the absorption with respect to the applied magnetic field. The field and frequency values depend on the experimental arra
18、ngements (sample size and sample holder), while their ratio (Le. g value) is an intrinsic characteristic of the paramagnetic centre and its local coordination. For further information, see l to 13. Radiation treatment produces radicals which can be detected in solid and dry parts of the food. The in
19、tensity of the signal obtained increases with the concentration of the paramagnetic compounds and thus with the applied dose. 4 Apparatus and equipment Usual laboratory apparatus and, in particular, the following: 4.1 controller and signal-channel, rectangular or cylindrical cavity 4.2 4.3 4.4 4.5 E
20、lectric blender 4.6 Filter paper 4.7 Scalpel 4.8 Commercially available X-Band ESR spectrometer including magnet, microwave bridge, console with field- ESR tubes, of internal diameter about 4,O mm (e.g. SuprasiKB) quartz tubes) Balance, accurate to the nearest 1 mg (optional) Laboratory vacuum oven,
21、 or freeze dryer Water of at least grade 3 according to EN IS0 3696 5 Procedure 5.1 Sample preparation 5.1.1 Shells and stones Remove pieces of suitable size (about 50 mg to 100 mg, 3,O mm to 35 mm in diameter) from the shells or stones of the food, e.g. using a scalpel. Drying (e. g. in a freeze-dr
22、yer or at approximately 40 “C in a laboratory vacuum oven (4.4) is usually not necessary in the case of nutshells but recommended for pips and kernels of fruits. I) Suprasit is an example of a product available commercially. This information is given for the convenience of users of this standard and
23、 does not constitute an endorsement of CEN of this product. Page 4 EN 1787 : 2000 5.1.2 Spices Use about 150 mg to 200 mg of the spice sample. Drying (e. g. in a freeze-dryer or at approximately 40 OC in a laboratory vacuum oven (4.4) is usually not necescary. 5.1 -3 Strawberries Strawberry samples
24、should be measured immediately after receipt. Otherwise store the samples at approximately - 18 OC until analysis. For ESR measurement about 200 rng of seeds (achenes) of strawberries are needed. These can be gained usually from about 80 g of strawberries. For separation of the small seeds from the
25、main fruit body either peel off the skin (recommendation: in frozen state) or use the whole fruit (without stalks and leaves). Homogenize the strawbemes in an electric blender (4.5). Add 500 ml of water to the fruit pulp and stir thoroughly. Allow the seeds to settle and decant most of the water tog
26、ether with the floating fruit pulp. Repeat this procedure once or twice to remove any remaining fruit pulp. Place the seeds on filter paper to remove adhering water. Dry the seeds in a freeze dryer or at approximately 40 OC in a laboratory vacuum oven (4.4) e.g. for 2 h. Do not grind the seeds since
27、 grinding will diminish the signal to noise ratio and can cause a change of the shape of the ESR spectrum. Storing samples in the frozen state will not adversely affect the detection of treatment with radiation. 5.2 ESR Spectroscopy 5.2.1 Spectrometer settings Use a time constant and sweep rate appr
28、opriate for an ESR signal with a peak to peak linewidth of approximately 0,8 mT. For example, the following ESR spectrometer settings have been found to be satisfactory: Microwave radiation: 9,78 GH3), power 0,4 mW (for pistachio nuts), to 0,8 mW (for paprika powder and straw- ber rie) Magnetic fiel
29、d: 348 mT centre field ), sweep width 20,O mT; Signal channel: 50 kHz or 100 kHz modulation frequency, 0,4 mT to 1 ,O mT modulation amplitude; 100 ms to 200 ms time constant4) sweep rate 5 mT min“ to 10 mT min- or accumulation of 3 to 5 spectra at greater sweep rate and shorter time constant; betwee
30、n approximately lo4 and lo6; Gain: Temperature: ambient temperature. 5.2.2 Analysis of sample Analyse the sample prepared as described in 5.1 in an ESR tube (4.2). 6 Evaluation A single signal C (see figure A.l and A.3) is observed in the ESR spectra of all food containing cellulose, including unirr
31、adiated samples. In the case of irradiated samples, the intensity of this signal is usually much greater and, in addition, a pair of lines occurs to the left (at lower field) and right (at higher field) of the central signal. This pair of lines is due to cellulose radicals formed by the ionizing rad
32、iation. The spacing of this radiation-induced signal pair is about 6,O mT and is symptomatic of radiation treatment having taken place (see figure A.2 and A.4). In some types of food, broad lines of low intensity due to paramagnetic Mn2+ ions are observed in addition to the signals mentioned. Howeve
33、r their position in the magnetic field is different, and the spacing between two manganese lines being about 9,0 mT (coupling constant) differs from the spacing of the irradiation specific signals. ) These values are for the specified microwave frequency and magnetic field; if the frequency is highe
34、r (lower) the magnetic field strength will be higher (lower). ) If saturation is suspected, the microwave power should be reduced, see lo ) These values are for the specified sweep rate. Page 5 EN 1787 : 2000 Product Pistachio shells 7 Limitations Detection limits and stability are influenced by the
35、 crystalline cellulose content and the moisture content of the samples. Positive identification of the cellulose radicals is evidence of irradiation but the absence of this signal does not constitute evidence that the sample is unirradiated. Detection of irradiated pistachio nuts has been validated
36、for doses of 2 kGy and above and stability is not expected to present limitations for detection of irradiation for at least one year after treatment. Detection of irradiated paprika powder has been validated for doses of 5 kGy and above. Stability of cellulose radicals in paprika powder is largely d
37、ependent on storage conditions, (especially humidity), and may be shorter than the shelf- life of the products. Detection of irradiated fresh strawberries has been validated for doses of 13 kGy and above. Detection of irradiated bemes has been analysed for doses of 0,5 kGy and above. Detection is ty
38、pically limited to about the first 3 weeks after treatment. Stability of cellulose radicals in berries depends on storage conditions and may be shorter than the shelf-life of the products. No of samples No of false negatives) No of false positives2) 84 15 2 Product No of samples Pistachio shells 68
39、No of false negatives) No of false positives2) O 1 Product No of samples Paprika powder 160 In an interiaboratory test carried out by the German Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) 21, 23 laboratories identified coded samples of fresh strawberries whic
40、h were either unirradiated or irradiated to about 1.5 kGy or 3 kGy (see table 4). No of false negatives) No of false positives2) O 1 Page 6 EN 1787 : 2000 No of No of false No of false No of inconclusive samples negatives ) positives ) results Product Strawberries 184 7 O 2 I) - ) False negatives ar
41、e irradiated samples identified as unirradiated. False positives are unirradiated samples identified as irradiated. Table 4 - Interiaboratory data 9 lest report The test report shall contain at least the following: information necessary for identification of the sample; a reference to this European
42、Standard; the result; date of sampling and sampling procedure (if known); date of receipt; date of test; any particular points observed in the course of the test; any operations not specified in the method or regarded as optional which might have affected the results. Annex A (normative) Figures h 6
43、.05 nil I Figure A.1- ESR spectrum of an unirradiated Figure A.2- ESR spectrum of a pistachio nut shell, irradiated with 4,O kGy, with irradiation specific line pair of the cellulose radical, spacing 6,05 mT I 0,05 mT (C) = unspecific central ESR-signal pistachio nut shell (C) = unspecific central E
44、SR-signal Page 7 EN 1787 : 2000 Figure A.3- ESR spectrum of seeds from unirradiated strawberries (C) = unspecific central ESR-signal Figure A.4- ESR spectrum of seeds from strawberries, irrad- iated with 3,5 kGy, with irradiation specific line pair of the cellulose radical, spacing 6,05 mT f 0,05 mT
45、, (C) = unspecific central ESR-signal Annex B (informative) Further information on the applicablllty Laboratory experience has been gained to support the application of this method to the following sample types: Raspberries, blueberries (chilled or frozen), french prunes, coconuts, almonds and walnu
46、ts. A list of tested food has been published Z. Bibliography Desrosiers, M.F. and McLaughlin, W.: Examination of gamma-irradiated fruits and vegetables by electron spin resonance spectroscopy. Radiat. Phys. Chem., 1989, 34, 895-898. Goodman,B.A., McPhail, D.B. and Duthie, D.M.L.: Electron spin reson
47、ance spectroscopy of some irradiated Helle, N. and Bgl, K.W.: Methods for identifying irradiated food. Food Tech., 1990, 4, 24-39. Raffi, J. and Agnel, J-P.: Identification par RPE daliments ioniss. Ann. Falsi. Exper. Chim. Toxi., Pans, 1989, Raffi, J., Agnel, J-P., Buscariet, L. and Martin, C.: ESR
48、 identification of irradiated strawberries. J. Chem. Soc. Farad. Trans. I, 1988, 84, 3359-3362. Raffi, J. and Agnel, J-P.: ESR identification of irradiated fruits. Radiat. Phys. Chem.,1989, 34, 891 -894. Raffi, J., Agnel, J-P. and Ahmad, S.H.: Electron spin resonance identification of irradiated dat
49、es. Food Tech.,l991, 314, 26-30. Untersuchung von LebensrnitteIn: Nachweis von bestrahlten cellulosehaltigen Lebensmitteln, Verfahren mittels ESR-Spektroskopie (L 00.00-42), Nachweis einer Strahlenbehandlung (ionisierende Strahlen) von Nssen (L 23.05-l), von Erdbeeren (L 29.00-5) und von cellulosehaltigen Gewrzen (L 53.00-4) durch Messung des ESR (Elektronen-Spin-Resonanz)-Spektrums : In: Amtliche Sammlung von Untersuchungsveriahren nach 9 35 LMBG: Verfahren zur Probenahme und Untersuchung von Lebensmitteln, Tabakzerzeugnissen, kosmetische
