1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 1786 : 1997 The Eur
2、opean Standard EN 1786 : 1996 has the status of a British Standard ICS 67.040 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Foodstuffs Detection of irradiated food containing bone Method by ESR spectroscopyBS EN 1786 : 1997 This British Standard, having been prepared under t
3、he direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on 15 June 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference AW/-/3 Draft for comment 95/500044 DC ISBN 0
4、580 27442 X Amendments issued since publication Amd. No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Panel AW/-/3, Food analysis Horizontal methods, upon which the following bodies were represented: Associati
5、on of Public Analysts Food and Drink Federation Institute of Food Science and Technology Laboratory of the Government Chemist Ministry of Agriculture Fisheries and Food Royal Society of ChemistryBS EN 1786 : 1997 BSI 1997 i Contents Page Committees responsible Inside front cover National foreword ii
6、 Foreword 2 Text of EN 1786 3ii BSI 1997 BS EN 1786 : 1997 National foreword This British Standard has been prepared under the direction of Technical Panel AW/-/3 and is the English language version of EN 1786 : 1996 Foodstuffs Detection of irradiated food containing bone Method by ESR spectroscopy,
7、 published by the European Committee for Standardization (CEN). EN 1786 was produced as a result of international discussions in which the United Kingdom took an active part. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document
8、comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 10, an inside back cover and a back cover.CEN European Committee for Standardization Comite Europe en de Normalisation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brus
9、sels 1996 Copyright reserved to CEN members Ref. No. EN 1786 : 1996 E EUROPEAN STANDARD EN 1786 NORME EUROPE ENNE EUROPA ISCHE NORM December 1996 ICS 67.020 Descriptors: Foodtstuffs, irradiated foodstuffs, ionizing radiation, food analysis, detection of irradiation treatment, meat bones, fish bones,
10、 ESR-spectroscopy English version Foodstuffs Detection of irradiated food containing bone Method by ESR spectroscopy Produits alimentaires De tection daliments ionise s contenant des os ou des are tes Me thode par spectroscopie RPE Lebensmittel Nachweis von bestrahlten knochen- bzw. gra tenhaltigen
11、Lebensmitteln Verfahren mittels ESR-Spektroskopie This European Standard was approved by CEN on 1996-12-05. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterat
12、ion. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translat
13、ion under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy Luxembourg, N
14、etherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.Page 2 EN 1786 : 1996 BSI 1997 Foreword This European Standard has been prepared by CEN/TC 275, Food analysis Horizontal methods, of which the Secretariat is held by DIN. This European Standard was elaborated on the basis of
15、 a protocol developed following a concerted action of the Commission of European Union (XII C.5). Experts and laboratories from EU and EFTA countries contributed jointly to the development of this protocol. This European Standard shall be given the status of a national standard, either by publicatio
16、n of an identical text or by endorsement, at the latest by June 1997, and conflicting national standards shall be withdrawn at the latest by June 1997. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this Europ
17、ean Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword 2 1 Scope 3 2 Definition 3 3 Principle 3 4 Apparatus 3 5 Sampling plan 3 6 Procedur
18、e 3 7 Evaluation 4 8 Limitations 4 9 Validation 5 10 Test report 5 Annexes A (normative) Figures 6 B (informative) Further information on the applicability 7 C (informative) Bibliography 8Page 3 EN 1786 : 1996 BSI 1997 1) Suprasil is an example of a suitable product available commercially. This info
19、rmation is given for the convenience of users of this standard and does not constitute an endorsement by CEN of this product. 1 Scope This European Standard specifies a method for the detection of meat containing bone and fish containing bone, which have been treated with ionizing radiation, by anal
20、ysing the electron spin resonance (ESR) spectrum (also called the electron paramagnetic resonance (EPR) spectrum) of the bones, see 1 to 11. Inter-laboratory studies have been successfully carried out with beef bones, trout bones and chicken bones, see 12 to 18. Since the radiation-induced ESR signa
21、l is attributed to hydroxyapatite (see 7.1), which is the principal component of bones, it is expected that application of the method can be extended to all meat and fish species containing bones. These expectations are consistent with laboratory experience (see annex B). The detection limit depends
22、 on the state of mineralization of the bones, which is usually lower for small species (see clause 8). 2 Definition For the purposes of this standard, the following definition applies. ESR spectrum The signals obtained by the method described in this European Standard. They are either due to paramag
23、netic compounds formed by irradiation or to compounds originally present. 3 Principle ESR spectroscopy detects paramagnetic centres (e.g. radicals). An intense external magnetic field produces a difference between the energy levels of the electron spins m s =+and m s =2, leading to resonance absorpt
24、ion 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 arrangements (sample size and sample holder), while their rat
25、io (i.e. g value) is an intrinsic characteristic of the paramagnetic centre and its local coordination. For an identification of irradiated samples it may be helpful to measure the g values of the ESR signals. For further information, see 1 to 12. Radiation treatment produces radicals which can be q
26、uite stable in solid and dry components of food (e.g. bones), and can be detected. The intensity of signal obtained increases with the concentration of the paramagnetic compounds and thus with the applied dose. 4 Apparatus Usual laboratory apparatus and, in particular, the following. 4.1 Commerciall
27、y available X-band ESR spectrometer, including magnet, microwave bridge, console with field-controller and signal-channel, rectangular or cylindrical cavity. 4.2 g value measurement unit, including frequency counter, magnetic field probe (nuclear magnetic resonance (NMR) gaussmeter), or any other bu
28、ilt-in g value measurement unit. 4.3 ESR tubes, of internal diameter about 4,0 mm (e.g. Suprasil 1) quartz tubes). 4.4 Balance, accurate to the nearest 1 mg (optional). 4.5 Laboratory vacuum oven or freeze dryer. 5 Sampling plan (No specification yet.) 6 Procedure 6.1 Sample preparation Remove flesh
29、 as completely as possible from a bone sample, e.g. using a scalpel, to get the bone as clean as possible. If necessary, split the bone and remove the marrow. Then dry the bone in a freeze dryer for about 18 h, or for about 3 h at approximately 40 C, in a laboratory vacuum oven (4.5). Remove a suita
30、ble sample piece (about 100 mg, 3,0 mm to 3,5 mm thick and 5,0 mm to 10,0 mm long) for analysis from the dried bone. Place the sample in a standard ESR tube (4.3). NOTE. The samples may be measured in powdered form or as bone fragments. Storing samples in the frozen state will not adversely affect t
31、he detection of treatment with radiation.Page 4 EN 1786 : 1996 BSI 1997 2) These values are for the specified microwave frequency and magnetic field; if the frequency is higher (lower), the magnetic field strength has to be set higher (lower). 3) These values are for the specified magnetic sweep wid
32、th. 6.2 ESR spectroscopy 6.2.1 Spectrometer settings Use a time constant and sweep rate appropriate for an ESR signal with a peak to peak linewidth of approximately 0,4 mT. For example, the following ESR spectrometer settings have been found to be satisfactory: Microwave radiation: 9,5 GHz 2) , powe
33、r 5 mW to 12,5 mW; Magnetic field: 342 mT 2) centre field; sweep width 5 mT to 20 mT; Signal channel: 50 kHz or 100 kHz modulation frequency; 0,2 mT up to 0,4 mT modulation amplitude; 50 ms to 200 ms time constant 3) ; sweep rate 3) 2,5 mTmin 21 to 10 mTmin 21 or accumulation of 3 to 5 spectra at gr
34、eater sweep rate and shorter time constant; Gain: between about 1,03 10 5 and 1,03 10 6 ; Temperature: room temperature. 6.2.2 Analysis of sample Analyse the sample prepared as described in 6.1 in an ESR tube (4.3). Although the g value of the individual signals of the ESR spectrum does not need to
35、be determined in most cases, it can be used for positive identification of irradiated samples (see 7.2). 7 Evaluation 7.1 Assessment of the ESR spectra Irradiated samples are recognized by the appearance of a typical asymmetric signal having g values of 2,002 and 1,998 (see 7.2). This signal is attr
36、ibuted to trapped radicals in hydroxyapatite produced by the action of ionizing radiation on the bone. A low intensity symmetrical signal having a g value of g symm. = 2,005 (see figure A.1) is sometimes present in the ESR spectra (e.g. in the case of bones containing marrow). Typical examples of ES
37、R spectra of unirradiated and irradiated bones (chicken thigh in this case) are shown in the figures A.1, A.2 and A.3. Note that the ESR spectra of bones irradiated at relatively low doses (less than 2 kGy to 3 kGy) frequently reveal a combination of the radiation-specific and the non-specific signa
38、l (see figure A.2). At doses less than 0,5 kGy, the non-specific signal may be stronger than the specific one. In contrast, the radiation-specific signal is frequently the only one observed (see figure A.3) in the case of high doses (more than 3 kGy). 7.2 Calculation of the g value Using the measure
39、d values obtained as described in 6.2.2, calculate the g value (g signal ) using equation 1: g signal = (1) 71,4883 n ESR B where n ESR is the microwave frequency, in gigahertz (GHz); B is the magnetic field (magnetic flux density), in millitesla (mT) (10 Gauss = 10 Gs = 1 mT). The procedure for cal
40、culating the g value of the signals from bone is to measure the frequency (e.g. frequency counter) and the field B (e.g. gaussmeter) at the positions of the arrows in figures A.1 to A.3. The following values are found in bones: g symm. = 2,005 0,001 (no proof of irradiation); g 1 = 2,002 0,001 (irra
41、diated); g 2 = 1,998 0,001 (irradiated). 8 Limitations Detection of irradiated bone samples is typically possible above a dose of approximately 0,5 kGy, covering the majority of commercial applications. Detection limits and stability are influenced by the degrees of mineralization and crystallinity
42、of hydroxyapatite in the sample. In general, the bones of larger animals and species are highly mineralized with low minimum detectable doses. However, variations within individual animals and species have been noted, see 19 to 21. In the case of meat bones, the results of this detection method are
43、not significantly influenced by heating of the sample (e.g. boiling in water). Detection of irradiation treatment is not significantly influenced by storage times of up to 12 months. For poorly mineralized fish bones it has been noted that non radiation-induced signals are strongly enhanced if the t
44、emperatures recommended for drying are exceeded (6.1), and this may interfere with the radiation specific signals.Page 5 EN 1786 : 1996 BSI 1997 Table 1. Inter-laboratory data Product No. of samples No. of false negatives 1) No. of false positives 2) Beef bone 84 0 0 Trout bone 84 5 3) 0 1) False ne
45、gatives are irradiated samples identified as unirradiated. 2) False positives are unirradiated samples identified as irradiated. 3) The five false negatives were due to misinterpretation of the spectra. Table 2. Inter-laboratory data Product No. of samples No. of false negatives 1) No. of false posi
46、tives 2) Chicken bone 108 0 0 Trout bone 108 0 2 3) 1) False negatives are irradiated samples identified as unirradiated. 2) False positives are unirradiated samples identified as irradiated. 3) The two false positives were due to misinterpretation of the spectra. 9 Validation This European Standard
47、 is based on inter-laboratory tests with meat bones and fish bones 12 to 18. In an inter-laboratory test carried out by the Community Bureau of Reference (BCR) 13, 16, 21 laboratories identified coded samples of beef bones and trout bones which were either unirradiated or irradiated to about 2 kGy,
48、4 kGy or 7 kGy (see table 1). In an inter-laboratory test carried out by the German Federal Health Office (Bundesgesundheitsamt, BGA) 17, 18 laboratories identified coded samples of chicken and trout bones which were either unirradiated or irradiated to about 2 kGy, 4 kGy or 6 kGy (see table 2). 10
49、Test report The test report shall contain at least the following: a) information for identification of the sample; b) a reference to this European Standard; c) the result; d) the date of sampling and sampling procedure (if known); e) the date of receipt; f) the date of test; g) any particular points observed in the course of the test; h) any operations not specified in the method or regarded as optional which might have affected the results.Page 6 EN 1786 : 1996 BSI 1997 Field: 350 mT 10 m
