1、BRITISH STANDARD Foodstuffs Detection of irradiated food containing crystalline sugar by ESR spectroscopy The European Standard EN 13708:2001 has the status ofa British Standard ICs 67.050 BS EN 13708:2002 BS EN 13708:2002 Amd. No. National foreword Date Comments This British Standard is the officia
2、l English language version of EN 13708:2001. The UKparticipation in its preparation was entrusted to Technical Committee AW/-/3, Food analysis - Horizontal methods, which has the responsibility to: - - aid enquirers to understand the text; present to the responsible European committee any enquiries
3、on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. Cr oss-r e fer enc e s The B
4、ritish Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A Bri
5、tish Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. This British Standard. having - been prepared
6、under the direction of the Consumer Summary of pages This document comprises a front cover, an inside front cover, the EN title page, Products and Services Sector Policyand Strategycommittee, was published under the authoritv of the Standards pages 2 to 9 and a back cover. The BSI copyright date dis
7、played in this document indicates when the Policy and Strategy Committee on 14 January 2002 document was last issued. O BSI 14 January 2002 ISBN O 580 38397 O EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 13708 October 2001 ICs 67.050 English version Foodstuffs - Detection of irradiated food
8、containing crystalline sugar by ESR spectroscopy Produits alimentaires - Dtection par spectroscopie de Rsonance Paramagntique Eledronique daliments ioniss contenant des sucres cristalliss Lebensmittel - ESR-spektroskopischer Nachweis von bestrahlten Lebensmitteln, die kristallinen Zucker enthalten T
9、his European Standard was approved by CEN on 20 August 2001. CEN members are bound 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 refere
10、nces concerning such national standards may be obtained on application to the 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 translation under the responsibility of a CEN member into
11、its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain
12、, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG COMIT EUROPEN DE NORMALISATION Management Centre: rue de Stassart, 36 B-1050 Brussels O 2001 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national
13、 Members. Ref. No. EN 13708:2001 E EN 13708:2001 (E) Contents Foreword 2 1 Scope 3 2 Principle 3 3 Apparatus and equipment . 3 4 Procedure . 4 5 Eva1 uat io n .4 6 Limitations 5 7 Validation 6 8 Test report 7 Annex A (normative) Figures . 8 Bibliography 9 Foreword This European Standard has been pre
14、pared by Technical Committee CEN/TC 275 “Food analysis - Horizontal methods“, the secretariat of which is held by DIN. 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 April 2002, and conflicting n
15、atioi?al standards shall be withdrawn at the latest by April 2002. This European Standard was elaborated on the basis of a protocol developed following a concerted action supported by the Commission of European Union (XII C.). Experts and laboratories from E.U. and EFTA countries, contributed jointl
16、y to the development of this protocol. According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy
17、, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 2 EN 13708:2001 (E) 1 Scope This European Standard specifies a method for the detection of foods containing crystalline sugars which have been treated with ionizing radiation, by analysing the electron sp
18、in resonance (ESR) spectrum, also called electron paramagnetic resonance (EPR) spectrum, of the food, see I to 7. Interlaboratory studies have been successfully carried out on dried figs, dried mangoes, dried papayas and raisins I to 3. 2 Principle ESR spectroscopy detects paramagnetic centres (e.g.
19、 radicals). They are either due to irradiation or to other compounds present. An intense external magnetic field produces a difference between the energy levels of the electron spins m, = + % and m, = - %, leading to resonance absorption of an applied microwave beam in the spectrometer. ESR spectra
20、are conventionally displayed as the first derivative of the absorption with respect to the applied magnetic field. The magnetic field and microwave frequency values depend on the experimental arrangements (sample size and sample holder), while their ratio (.e. g value) is an intrinsic characteristic
21、 of the paramagnetic centre and its local co-ordination. For further information, see I to 7. Radiation treatment produces radicals which can be detected in solid and dry parts of the food. The intensity of the signal obtained increases with the concentration of the paramagnetic compounds and thus w
22、ith the applied dose. 3 Apparatus and equipment Usual laboratory apparatus and, in particular, the following: 3.1 Commercially available X-Band ESR spectrometer including magnet, microwave bridge, console with field-controller and signal-channel, rectangular or cylindrical cavity 3.2 resonance (NMR)
23、 Gaussmeter), or any other built-in g-value measurement unit. G-value measurement unit including frequency counter, magnetic field probe (nuclear magnetic 3.3 ESR tubes, of internal diameter about 4,O mm (e.g. SuprasilBI) quartz tubes) 3.4 Balance, accurate to the nearest 1 mg (optional) 3.5 Laborat
24、ory vacuum oven, or freeze dryer 3.6 Scalpel 4 Procedure 4.1 Sample preparation Prepare suitable pieces (50 mg to 100 mg) of the fruit, e.g. using a scalpel. 1) Suprasil is an example of a suitable product available commercially. This information is only given for the convenience of users of this In
25、ternational Standard and does not constitute an endorsement by CEN of this product. 3 EN 13708:2001 (E) NOTE Various parts of the fruits can contain different quantities of crystalline sugars. It can be advantageous to take the test sample from the outer parts of the fruits. Transfer a test portion
26、directly into the ESR tube (3.3) and start the measurement. Difficulties in tuning the spectrometer cavity can be experienced if the sample is insufficiently dry. In this case either reduce the sample quantity or dry it further. Samples should be dried in a laboratory vacuum oven at approximately 40
27、 “C under reduced pressure or in a freeze-dryer. WARNING: Excessive heating can reduce the signal. 4.2 ESR Spectroscopy 4.2.1 Spectrometer settings Use a time constant and sweep rate appropriate for ESR signals with linewidths of 0,2 mT to 0,4 mT. For example, the following ESR spectrometer settings
28、 have been found to be satisfactory: Microwave radiation: Magnetic field: Signal channel: Gain: Tem perature: 9,78 GHz”, power 5 mW 348 mT centre field”, sweep width 10,O mT to 20,O mT; 50 kHz or 100 kHz modulation frequency, 0,15 mT to 0,4 mT modulation amplitude; 100 ms to 200 ms time constant3) s
29、weep rate 5 mT min-1 to 10 mT min-1 or accumulation of 3 to 5 spectra at greater sweep rate and shorter time constant; between IO4 and 106: ambient temperature. 4.2.2 Analysis of sample Analyse the sample prepared as described in 4.1 in an ESR tube (3.3). 5 Evaluation 5.1 Identification of irradiate
30、d samples 5.1 .I General Irradiated food containing crystalline sugar show typical multicomponent ESR spectra reflecting the presence of radiation-induced radicals in the sample. Dried fruits often contain sugar particles in crystalline form, and therefore the appearance of a typical multicomponent
31、ESR spectrum (see annex A) indicates radiation treatment. Due to different mono- and disaccharides and due to the changes in saccharide composition various ESR spectrum types can occur. Other irradiated sugar-containing foodstuffs reveal ESR spectra which have similar structures. Since the overall s
32、pectrum structure depends on the radical composition and on the crystallinity of the mono- and disaccharides present in the sample, variations in the spectrum characteristics occur. 2) These values are for the specified microwave frequency and magnetic field; if the frequency is higher (lower) the m
33、agnetic field strength will be higher (lower). 3) These values are for the specified sweep rate. 4 EN 13708:2001 (E) For monocrystalline samples the orientation within the ESR cavity can influence the relative intensities of the ESR lines and thus the spectral shape. However in the majority of dried
34、 fruit samples randomly oriented microcrystalline sugars produce a powder type spectrum. This produces broader lines and spectral shapes which are less sensitive to orientation. Typical characteristics are described in 5.1.2 and 5.1.3, and illustrated in figures A.2 and A.4. Where similar features a
35、re observed the sample can be identified as irradiated. 5.1.2 Irradiated dried mangoes and dried papayas An ESR spectrum shown in figure A.2 and having the following characteristics is significant for irradiated dried mangoes and dried papayas: overall spectrum width: 7,4 mT to 7,8 mT g-value (centr
36、e of spectrum): 2,0035 f 0,0010 5.1.3 Irradiated dried figs and raisins An ESR spectrum shown in figure A.4 and having the following characteristics is significant for irradiated dried figs and raisins: overall spectrum width: g-value (centre of spectrum): 8,7 mT to 9,l mT 2,0035 f 0,0010 5.1.4 Unir
37、radiated samples Unirradiated samples of dried mangoes, dried papayas, dried figs and raisins show no ESR spectrum at all or a broad singlet as shown in figures A.l and A.3 with a g-value of 2,0040 f 0,0010. 5.2 G-value measurement For the characterisation of the ESR spectrum, especially as regards
38、the identification of irradiated samples, it is helpful to measure the g-values of the ESR-signals. A g-value of a signal, gsignal, is calculated using equation (1): - 7 1,448. vESR B gsignal - where: is the microwave frequency, in gigahertz (GHz); B is the magnetic flux density (magnetic field sett
39、ing of the spectrometer), in millitesla (mT) (IO Gauss = 10 G = 1 mT). The procedure for calculating the g-value of the ESR spectrum of dried fruits is to position the field in the centre of the ESR spectrum (CF in figures A.l to A.4) and to measure the frequency v (e.g. frequency counter) and the f
40、ield B (e.g. gaussmeter) at this point. 6 Limitations While the general formation processes of radiation-induced radicals are known, identification of the specific radicals responsible for individual signals has not yet been achieved. Nevertheless, the association between radiation treatment and the
41、 signals illustrated in clause 5 and figures A.2 and A.4 has been demonstrated in a number of studies I to 7. Multicomponent ESR spectra prove prior irradiation but the absence of the specific spectrum does not constitute evidence that the sample is unirradiated. Different mono- or disaccharides may
42、 dominate in the sample producing 5 EN 13708:2001 (E) Product Raisins Dried papayas different ESR spectra after irradiation. Moreover, if no sugar crystals are present in the sample, irradiation will not produce specific ESR signals. No of samples No of false negativesa No of false positivesb 126 7“
43、 1 126 2d O Detection of irradiated dried figs, dried mangoes, dried papayas and raisins has been validated. The lower limit of detection mainly depends on the crystallinity of the sugar in the sample. Detection of irradiation treatment is not significantly influenced by storage of at least several
44、months. Product Dried mangoes Dried figs The applicability of this method depends on the presence of sufficient quantities of crystalline sugar in the sample at all stages of handling between irradiation and testing. Confirmation of sensitivity to radiation can be achieved, where necessary, by irrad
45、iating a portion of the sample and re-testing. It is important that dried fruits have not been re-hydrated prior to testing. No of samples No of false negativesa 184 O O 184 2 O No of false positivesb 7 Validation This European Standard is based on two interlaboratory tests, one with dried papayas a
46、nd raisins, I, 2, and one with dried mangoes and dried figs 3. In an interlaboratory test carried out by the Community Bureau of Reference (BCR) I, 2, 21 laboratories identified coded samples of dried papayas and raisins which were either unirradiated or irradiated to about 0,5 kGy, 1 kGy, 2 kGy, 4
47、kGy or 7 kGy (see Table 1). Table 1 - Interlaboratory data a False negatives are irradiated samples identified as unirradiated. False positives are unirradiated samples identified as irradiated. Obtained from the 19 samples irradiated at 0,5 kGy. Obtained from the 21 samples irradiated at 0,5 kGy b
48、d In another interlaboratory test carried out by the German Federal Institute for Health Protection and Veterinary Medicine (BgVV) 3, 17 laboratories identified coded samples of dried mangoes and dried figs which were either unirradiated or irradiated to about 1 kGy, 3 kGy or 5 kGy (see Table 2) Tab
49、le 2 - Interlaboratory data EN 13708:2001 (E) information necessary for identification of the sample; a reference to this European Standard; date of sampling and sampling procedure (if known); date of receipt; date of test; the result; 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. 7 EN 13708:2001 (E) Annex A ( no rm a t ive) Fig u res Ct 5mT Figure A.l - Typical ESR spectrum of unirradiated dried mangoes 5rnT Figure A.2 - Typical ESR sp
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