1、November 2009DEUTSCHE NORM English price group 10No part of this standard 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 67.050!$ZaC“1556232ww
2、w.din.deDDIN EN 13751Foodstuffs Detection of irradiated food using photostimulated luminescenceEnglish version of DIN EN 13751:2009-11Lebensmittel Nachweis von bestrahlten Lebensmitteln mit Photostimulierter LumineszenzEnglische Fassung DIN EN 13751:2009-11SupersedesDIN EN 13751:2002-12www.beuth.deD
3、ocument comprises pages14DIN EN 13751:2009-11 National foreword This standard has been prepared by Technical Committee CEN/TC 275 “Food analysis Horizontal methods” (Secretariat: DIN, Germany). Preliminary work was done by Working Group WG 8 “Irradiated Foodstuffs”. The responsible German body invol
4、ved in its preparation was the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Technical Committee NA 057-01-02 AA Bestrahlte Lebensmittel. The treatment of foods with ionising radiation is only permissible in accordance with the fr
5、amework Directive “1999/2/EC of the European Parliament and of the Council of 22 February 1999 on the approximation of the laws of the Member States concerning foods and food ingredients treated with ionising radiation”. This standard has the purpose to detect irradiation of food. Amendments This st
6、andard differs from DIN EN 13751:2002-12 as follows: a) This standard contains the information in clause 9 that when judging the result of the analysis, the analyst should consider that the sample might have been subject to optical bleaching prior to arrival in the laboratory. Previous editions DIN
7、EN 13751: 2002-12 2 EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 13751July 2009ICS 67.050 Supersedes EN 13751:2002 English VersionFoodstuffs - Detection of irradiated food using photostimulatedluminescenceProduits alimentaires - Dtection daliments ioniss parluminescence photostimuleLebensmittel
8、 - Nachweis von bestrahlten Lebensmitteln mitPhotostimulierter LumineszenzThis European Standard was approved by CEN on 19 June 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national stan
9、dard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other l
10、anguage made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finla
11、nd,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE
12、 FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13751:2009: EEN 13751:2009 (E) 2 Contents Page Foreword 3 1 Scope 4 2 Terms and definitions .4 3 Principle 5 4 Reage
13、nts .6 5 Apparatus .6 6 Sampling technique .6 7 Procedure .7 8 Evaluation .8 9 Limitations . 10 10 Validation . 10 11 Test report . 11 Bibliography . 12 DIN EN 13751:2009-11 EN 13751:2009 (E) 3 Foreword This document (EN 13751:2009) has been prepared by Technical Committee CEN/TC 275 “Food analysis
14、- 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 January 2010, and conflicting national standards shall be withdrawn at the latest by
15、 January 2010. 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 13751:2002. According to the CEN/CENELEC In
16、ternal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg,
17、Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. DIN EN 13751:2009-11 EN 13751:2009 (E) 4 1 Scope This European Standard specifies a method for the detection of irradiated foods using photostimulated luminescence (PSL). The
18、 technique described here comprises an initial measurement of PSL intensity which may be used for screening purposes, and a calibration method to determine the PSL sensitivity to assist classification. It is necessary to confirm a positive screening result using calibrated PSL or another standardise
19、d (e.g. EN 1784 to EN 1788) or validated method. The method has been successfully tested in interlaboratory trials using shellfish and herbs, spices and seasonings 1. From other studies it may be concluded that the method is applicable to a large variety of foods 2, 3, 4. 2 Terms and definitions For
20、 the purposes of this document, the following terms and definitions apply. 2.1 photostimulated luminescence PSL radiation specific phenomenon resulting from energy stored by trapped charge carriers NOTE Release of this stored energy by optical stimulation can result in a detectable luminescence sign
21、al. 2.2 PSL intensity amount of light detected during photostimulation, in photon count rate 2.3 screening PSL initial PSL PSL intensity recorded from the sample as received or following preparation 2.4 calibrated PSL PSL intensity recorded from the test sample following irradiation to a known dose,
22、 after initial PSL measurement 2.5 thresholds values of PSL intensity used for classification. In screening mode, two thresholds, a lower threshold (T1) and an upper threshold (T2) are used to classify the sample 2.6 negative PSL result PSL intensity below the lower threshold (less than T1) 2.7 inte
23、rmediate PSL result PSL intensity between the upper and the lower threshold (greater than or equal to T1, less than or equal to T2) 2.8 positive PSL result PSL intensity above the upper threshold (greater than T2) DIN EN 13751:2009-11 EN 13751:2009 (E) 5 2.9 dark count photon count rate from the pho
24、tomultiplier with an empty chamber in the absence of stimulation 2.10 light count photon count rate with a reference light source (e.g. 14C loaded scintillant, or equivalent) in the sample chamber 2.11 empty chamber run PSL intensity measured from an empty sample chamber to ensure absence of contami
25、nation of the chamber 3 Principle 3.1 General Mineral debris, typically silicates or bioinorganic materials such as calcite which originate from shells or exoskeletons, or hydroxyapatite from bones or teeth, can be found on most foods. These materials store energy in charge carriers trapped at struc
26、tural, interstitial or impurity sites, when exposed to ionising radiation. Excitation spectroscopy has shown that optical stimulation of minerals releases charge carriers 5, 6, 7. It has subsequently been shown that the same spectra can be obtained from whole herb and spice samples and other foods u
27、sing photostimulation 2, 8, 9. PSL measurements do not destroy the sample, therefore whole samples, or other mixtures of organic and inorganic material, can be measured repeatedly. PSL signals, however, decrease if the same sample is measured repeatedly. The methodology comprises screening (initial)
28、 PSL measurements to establish the status of the sample (see 2.3) and an optional second measurement following a calibration radiation dose to determine the PSL sensitivity of the sample (see 2.4). 3.2 Screening PSL For screening (see 2.3) the signal levels are compared with two thresholds (see 2.5)
29、. The majority of irradiated samples produce a strong signal above the upper threshold level. Signals below the lower threshold suggest that the sample has not been irradiated. Signal levels between the two thresholds, intermediate signals, show that further investigations are necessary. The use of
30、thresholds produces an effective screening method which can also be backed up by calibration, by TL as described in EN 1788 or another validated method, e.g. 3, 4, 8. 3.3 Calibrated PSL For calibration, the sample is exposed to a defined radiation dose after the initial PSL measurement, and then re-
31、measured. Irradiated samples show only a small increase in PSL after this radiation exposure, whereas unirradiated samples usually show a substantial increase in PSL signal after irradiation. DIN EN 13751:2009-11 EN 13751:2009 (E) 6 4 Reagents 4.1 Aerosol silicone grease, e.g. Electrolube SC0200H1)4
32、.2 Water, deionized 5 Apparatus 5.1 PSL system, e.g. SURRC PPSL Irradiated food screening system1)10, 11, 12, 13, comprising sample chamber, stimulation source, pulsed stimulation and synchronised photon counting system. For instrumental set-up, see 7.4. NOTE For the interlaboratory tests, the SURRC
33、 PPSL system has been used. 5.2 Disposable Petri-dishes NOTE For the interlaboratory tests, 5 cm Petri-dishes have been used. 5.3 Radiation source, capable of irradiating samples with a defined radiation dose before measurement of calibrated PSL. In the interlaboratory tests on shellfish and herbs,
34、spices and their mixtures 1, sources delivering 60Co-rays have been employed at a fixed radiation dose of 1 kGy. Alternative sources may be used providing they have been found satisfactory. NOTE Other fixed doses can be suitable. 5.4 14C-Source (optional) 5.5 Laminar flow cabinet (optional) 5.6 Air
35、duster (optional) 6 Sampling technique Whenever possible, the sample is taken from a light-protected position in the food consignment, since the PSL intensity decreases on exposure to light. Before analysis, samples should be protected against light exposure. Store them in the dark. 1)Electrolube SC
36、0200H and Scottish Universities Research and Reactor Center Pulsed Photostimulated Luminescence (SURRC PPSL) are examples of products available commercially. This information is given for the convenience of users of this standard and does not constitute an endorsement of CEN of these products. Equiv
37、alent products may be used if they can be shown to lead to equivalent results.DIN EN 13751:2009-11 EN 13751:2009 (E) 7 7 Procedure 7.1 General All dispensing and handling of samples should be carried out under subdued lighting whenever possible. Samples are dispensed into disposable Petri-dishes and
38、 introduced to the system. Samples should be handled with care to avoid cross-contamination during dispensing. It is recommended that samples are dispensed individually, under a laminar flow cabinet (5.5), and fresh tissue is placed on the bench for each sample. The Petri-dish should be covered with
39、 a lid to reduce the possibility of contamination. 7.2 Preparation of herb, spice and seasoning samples Samples are dispensed into clean Petri-dishes, in duplicate. If these test samples lead to inconsistent classifications, a further four aliquots shall be dispensed and classification based on the
40、highest two results. Some samples can require a minimum of preparation; e.g. vanilla pods may need to be cut to fit the dish and wrappings should be removed. Samples can either be dispensed in a thick layer within the Petri-dish or in a thin layer, applied to a dish already sprayed with silicone gre
41、ase (4.1) to fix the sample. Thicker layer samples are less likely to be affected by bleaching; subsurface minerals can be exposed by gentle agitation. NOTE Thin layer samples can also be dispensed into planchets or other shallow containers suitable for irradiation with 90Sr or other sources. If a g
42、amma source is used for calibration either dispensing method is suitable. 7.3 Preparation of shellfish 7.3.1 General PSL analysis can be conducted using whole samples including shell, shelled whole samples and dissected intestines or minerals extracted by flushing with water (4.2). If enough sample
43、material is available, it is recommended that samples be divided into at least six portions, i.e. six Petri-dishes. 7.3.2 Whole samples Whole samples including shell can be placed as received in the Petri-dish. In some cases it can be necessary to cut the shellfish to fit the Petri-dish. If the inte
44、stinal tract is visible, it is preferable to place this uppermost. 7.3.3 Shelled whole samples Shelled whole samples can be placed whole in the Petri-dish, again with the intestinal tract facing upwards, using as many individual shellfish as will fit in the Petri-dish. 7.3.4 Shellfish intestines She
45、llfish intestines can be found as a thin dark tube on the convex side of prawns or shrimps, and in the interiors of molluscs. Using a scalpel, slice the flesh open and with tweezers remove the intestinal tract. Repeat this technique on several samples of shellfish (recommended: 6 intestines per Petr
46、i-dish). 7.4 Instrumental Set-Up This section describes the set-up of the SURRC PPSL system, as an example. DIN EN 13751:2009-11 EN 13751:2009 (E) 8 The system is used in conjunction with a computer for setting individual measurement parameters (cycle time, thresholds and data recording conditions)
47、for recording quantitative photon counts. NOTE 1 The system can be used in a stand-alone mode, with simple push button controls, for preliminary measurements. However, the validated procedures which are the subject of this standard apply only to quantitative measurements performed in conjunction wit
48、h a computer. The instrumental set-up procedure includes checks on dark count (2.9) and light count (2.10), establishing measurement parameters and checks on irradiated and unirradiated standard materials. For herbs and spices tested in the interlaboratory trial 1, the threshold settings of T1= 700
49、counts/60 s and T2= 5 000 counts/60 s have been shown to be satisfactory. These thresholds refer to the use of 5 cm Petri-dishes. For shellfish tested in the interlaboratory trial 1, the threshold settings of T1= 1 000 counts/60 s and T2= 4 000 counts/60 s have been shown to be satisfactory. NOTE 2 The threshold levels are based on results of interlaboratory tests and further experience. They might need to be adjusted in dependence of the PSL sensitivity of the samples, the sensitivity of the instrument and the surface area of the
