BS EN 13751-2009 Foodstuffs - Detection of irradiated food using photostimulated luminescence《食品 用光致发光法探测辐照过的食品》.pdf

1、BS EN 13751:2009ICS 67.050NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDFoodstuffs Detectionof irradiated foodusing photostimulatedluminescenceThis British Standardwas published underthe authority of theStandards Policy andStrategy Committee on 30September 200

2、9 BSI 2009ISBN 978 0 580 65095 6Amendments/corrigenda issued since publicationDate CommentsBS EN 13751:2009National forewordThis British Standard is the UK implementation of EN 13751:2009. Itsupersedes BS EN 13751:2002 which is withdrawn.The UK participation in its preparation was entrusted to Techn

3、icalCommittee AW/-/3, Food analysis - Horizontal methods.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Complian

4、ce with a British Standard cannot confer immunityfrom legal obligations.BS EN 13751:2009EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 13751July 2009ICS 67.050 Supersedes EN 13751:2002 English VersionFoodstuffs - Detection of irradiated food using photostimulatedluminescenceProduits alimentaires

5、- Dtection daliments ioniss parluminescence photostimuleLebensmittel - 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 condi

6、tions for giving this EuropeanStandard the status of a national standard 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 o

7、fficial versions (English, French, German). A version in any other language 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

8、, Belgium, Bulgaria, 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 Kingdom.EUROPEAN COMMITTEE

9、FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE 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: EBS EN 13751:2009EN 13751:2009 (E) 2

10、 Contents Page Foreword 3 1 Scope 4 2 Terms and definitions .4 3 Principle 5 4 Reagents .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 BS EN 13751:2009EN 13751:2009 (E) 3 Foreword This document (EN

11、13751:2009) has been prepared 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 Janua

12、ry 2010, and conflicting national standards shall be withdrawn at the latest by 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

13、rights. This document supersedes EN 13751:2002. According to the CEN/CENELEC Internal 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, Ger

14、many, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 13751:2009EN 13751:2009 (E) 4 1 Scope This European Standard specifies a method for the d

15、etection of irradiated foods using photostimulated luminescence (PSL). The 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 confi

16、rm a positive screening result using calibrated PSL or another standardised (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 a

17、pplicable to a large variety of foods 2, 3, 4. 2 Terms and definitions For 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

18、energy by optical stimulation can result in a detectable luminescence signal. 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 inte

19、nsity recorded from the test sample following irradiation to a known dose, 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

20、PSL result PSL intensity below the lower threshold (less than T1) 2.7 intermediate 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) BS EN 13751:

21、2009EN 13751:2009 (E) 5 2.9 dark count photon count rate from the photomultiplier 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 intensi

22、ty measured from an empty sample chamber to ensure absence of contamination 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 fo

23、ods. These materials store energy in charge carriers trapped at structural, 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 spectr

24、a can be obtained from whole herb and spice samples and other foods using 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

25、is measured repeatedly. The methodology comprises screening (initial) 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 (

26、see 2.3) the signal levels are compared with two thresholds (see 2.5). 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

27、 signals, show that further investigations are necessary. The use of 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 d

28、efined radiation dose after the initial PSL measurement, and then re-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. BS EN 13751:2009EN 13751:2009 (E) 6 4 R

29、eagents 4.1 Aerosol silicone grease, e.g. Electrolube SC0200H1)4.2 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 instrumenta

30、l set-up, see 7.4. NOTE For the interlaboratory tests, the SURRC 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 calib

31、rated PSL. In the interlaboratory tests on shellfish and herbs, 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 14

32、C-Source (optional) 5.5 Laminar flow cabinet (optional) 5.6 Air 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

33、against light exposure. Store them in the dark. 1)Electrolube SC0200H 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 do

34、es not constitute an endorsement of CEN of these products. Equivalent products may be used if they can be shown to lead to equivalent results.BS EN 13751:2009EN 13751:2009 (E) 7 7 Procedure 7.1 General All dispensing and handling of samples should be carried out under subdued lighting whenever possi

35、ble. Samples are dispensed into disposable Petri-dishes and 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 b

36、ench for each sample. The Petri-dish should be covered with 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 a

37、liquots shall be dispensed and classification based on the 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

38、 layer, applied to a dish already sprayed with silicone grease (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

39、suitable for irradiation with 90Sr or other sources. If a gamma 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 mineral

40、s extracted by flushing with water (4.2). If enough sample 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 necess

41、ary to cut the shellfish to fit the Petri-dish. If the intestinal 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

42、 will fit in the Petri-dish. 7.3.4 Shellfish intestines Shellfish 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 sever

43、al samples of shellfish (recommended: 6 intestines per Petri-dish). 7.4 Instrumental Set-Up This section describes the set-up of the SURRC PPSL system, as an example. BS EN 13751:2009EN 13751:2009 (E) 8 The system is used in conjunction with a computer for setting individual measurement parameters (

44、cycle time, thresholds and data recording conditions) 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

45、quantitative measurements performed in conjunction with 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 inter

46、laboratory trial 1, the threshold settings of T1= 700 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 c

47、ounts/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 samples (

48、size of petri-dishes). It has been shown that e.g. pepper, nutmeg and clove are less sensitive to PSL. An empty chamber test (2.11) should be run to ensure that the chamber is free from contamination. This step should be repeated periodically, e.g. at least every 10 samples and also after samples wi

49、th positive results. An air duster (5.6) can be used to clean the sample chamber. 7.5 Screening Measurements Run the test samples and record the results over the specified measurement time. The results should be classified according to the pre-set thresholds 2.6 to 2.8. 7.6 Calibrated Measurements After screening, the sample should be covered to prevent loss of material or contamination, either with the lid of the Petri-dish or, in the case of planchets or shallow containers, some other suitable means. During handling, care should be t