Ionizing radiation is widely used as treatment technique for food preservation. It involves among others reduction of microbial contamination, disinfestations, sprout inhibition and extension of shelf life of food. However, the commercialization of irradiated food requires the availability of reliable methods to identify irradiated foodstuffs. In this paper, we present results on the application to irradiated chicken of this method, based on the detection, in muscle and skin samples, of the peaks of ions 98 Da and 112 Da, in a ratio approximately 4:1, typical of radiation induced 2-dodecylcyclobutanones (2-DCB). Aim of the work was also to study the time stability of the measured parameters in samples irradiated at 3 and 5 kGy, and to verify the efficacy of the treatment from a microbiological point of view. Our results show that, one month after irradiation at 3 kGy, the method is suitable using the skin but not the muscle, while the measured parameters are detectable in both samples irradiated at 5 kGy. The microbial population was substantially reduced even at 3 kGy. © 2007 Elsevier Ltd. All rights reserved

AGOZZINO, Pasquale

AVELLONE, Giuseppe

BARTOLOTTA A

BRAI, Maria

CALDERARO, Elio Giuseppe

CARACAPPA S.

D'OCA, Maria Cristina

DI NOTO AM

FERRUGIA, Mirella

GIUFFRIDA SA

PARLATO, Aldo

TRANCHINA, Luigi

Archivio istituzionale della ricerca - Università di Palermo

ARTICLE IN PRESS0969-806X/$ - sdoi:10.1016/j.raCorrespondE-mail addrRadiation Physics and Chemistry 76 (2007) 1463–1465www.elsevier.com/locate/radphyschemGas chromatographic/mass spectrometric and microbiologicalanalyses on irradiated chickenA. Parlatoa, E. Calderaroa, A. Bartolottab,, M.C. D’Ocab, S.A. Giuffridab, M. Braic,L. Tranchinac, P. Agozzinod, G. Avelloned, M. Ferrugiad, A.M. Di Notoe, S. CaracappaeaDipartimento di Ingegneria Nucleare, Universita` di Palermo, Viale delle Scienze, Edificio 6, 90100 Palermo, ItalybDipartimento Farmacochimico, Tossicologico e Biologico, Universita´ di Palermo, via Archirafi 32, 90123 Palermo, ItalycDipartimento di Fisica e Tecnologie Relative, Universita` di Palermo, Viale delle Scienze, Edificio 18, 90100 Palermo, ItalydDipartimento di Chimica e Tecnologie Farmaceutiche, Universita` di Palermo, via Archirafi 32, 90123 Palermo, ItalyeIstituto Zooprofilattico Sperimentale della Sicilia ‘‘A.Mirri’’, Palermo, ItalyAbstractIonizing radiation is widely used as treatment technique for food preservation. It involves among others reduction of microbialcontamination, disinfestations, sprout inhibition and extension of shelf life of food. However, the commercialization of irradiated foodrequires the availability of reliable methods to identify irradiated foodstuffs. In this paper, we present results on the application toirradiated chicken of this method, based on the detection, in muscle and skin samples, of the peaks of ions 98 Da and 112 Da, in a ratioapproximately 4:1, typical of radiation induced 2-dodecylcyclobutanones (2-DCB). Aim of the work was also to study the time stabilityof the measured parameters in samples irradiated at 3 and 5 kGy, and to verify the efﬁcacy of the treatment from a microbiological pointof view. Our results show that, one month after irradiation at 3 kGy, the method is suitable using the skin but not the muscle, while themeasured parameters are detectable in both samples irradiated at 5 kGy. The microbial population was substantially reduced evenat 3 kGy.r 2007 Elsevier Ltd. All rights reserved.Keywords: Irradiated food; Gas chromatography; Radiation treatment1. IntroductionIn recent years the interest in food safety is grown moreand more, not only from the administration, the research-ers and the food industry side, but mainly from theconsumers point of view.The microbiological contamination represents a seriousproblem, and the strategies aimed to prevent and to reduceits risk are in continuous evolution. The irradiation of foodsagainst the microbiological risk surely is an innovativeapproach in comparison to the traditional methods aschemical fumigation.Radiation treatment is carried out with gamma orelectron beams, with energy and dose values that do notmodify nutritional properties of irradiated food, do notee front matter r 2007 Elsevier Ltd. All rights reserved.dphyschem.2007.02.052ing author. Tel.: +390916162323; fax: +39 0916169999.ess: antonio.bartolotta@unipa.it (A. Bartolotta).produce toxical effects and do not induce radioactivity infood itself (WHO, 1987).Irradiation with doses lower than 10 kGy (WHO, 1999)is widely used as treatment technique for food preserva-tion. It allows to drastically reduce the microbial contam-ination, to disinfect from insects, to prevent sprouting; areduction of food spoilage and an extension of the shelf lifeof food can be also achieved. However, the commercializa-tion of irradiated food requires the availability of reliablemethods to identify irradiated foodstuffs. The EuropeanCommunity has validated standard biological, physicaland chemical methods, each one speciﬁc for some foodtypology; among them, the gas chromatography/massspectrometry is recommended for the detection of irra-diated food containing fat.The main goal of the research discussed in this paper wasto investigate the application of the identiﬁcation method(EN 1785, 1996) based on gas chromatography and massARTICLE IN PRESSA. Parlato et al. / Radiation Physics and Chemistry 76 (2007) 1463–14651464spectrometry (GC/MS) in irradiated chicken. In particularwe have studied if the irradiation treatment was detectablewithin the typical shelf life of the chicken, and in whichpart of it (skin or muscle), as a function of dose and storageconditions. Moreover, the effect of ionizing radiation onthe microbiological population was investigated.2. Materials and methodsAmong the 2-alkylcyclobutanones produced in irra-diated meat, we have chosen to analyze the 2-dodecylcy-clobutanone (2-DCB), which is formed from palmitic acidduring irradiation.Table 1The table shows the results of the bacteriological examination on thechicken samples before ð1 30 gÞ and after ð1 30 gÞ the radiationtreatment at 3 kGyBacteriological test Unirradiated (cfu/g) Irradiated (cfu/g)CMT 2:7 108 1:1 105Coliforms 1:2 102 o1 101E. coli 8:0 101 o1 101Staphylococci coagulase-positive o10 101 o10 101Enterococcus spp. 1:4 103 6:0 101Clostridia s.r. o1 101 o1 101Salmonella spp. Not detectable Not detectable2.1. Fat extraction and purification of extracts obtainedChickens were purchased at local stores, packed inaluminium boxes, and stored at ð024Þ C. For each analysis(carried out on two different chickens), the lipids wereextracted from a sample of 20 g composed by muscle (15 g)and skin (5 g) of chicken, that is approximately the naturalcomposition of chicken meat, with an average fat contentbetween 1% and 4%; for comparison purposes, sample ofmuscle alone or skin alone were investigated. Each samplewas homogenized and mixed with 20 g of anhydroussodium sulfate. Each lipid fraction, 200mg each, waspuriﬁed by solid phase extraction on a column Florisilsdeactivated. The hexane extracts, expecting to contain2-DCB, was concentrated to a volume of 5ml at the temp-erature of 40 C using a rotary vacuum evaporator, andfurther concentrated to complete dryness by nitrogen, andresuspended with n-hexane. A standard 2-DCB solutionwas prepared by solving 2-DCB in n-hexane to a ﬁnalconcentration of 0:5mg=ml.Fig. 1. Chromatograms obtained for the detection of 2-dodecylcyclobu-tanone (selected ions monitoring of the ions 98 and 112Da) in a sample ofchicken irradiated at 5 kGy (up), and in a solution containing the standard2-DCB (down).2.2. Separation and identification of 2-DCBThe GC/MS analysis was carried out on Varian Saturn3-Ion Trap System spectrometer. The used capillarycolumn was a J&W DB 5MS. The following conditionswere applied: helium was used as the carrier gas at ﬂow rateof about 1ml/min, the transfer line and ion traptemperature was 180 C; the injector temperature was ﬁxedat 250 C; the column temperature program was: 1min at55 C followed by a ramp rate of 15 C=min up to 300 Cheld for 10min. The ion trap mass spectrometer para-meters were: electron ionization mode, ionizing energy70 eV, mass range 30–200Da and the scan frequency was4 scans/s; injected volume 1mL. The collected data wereprocessed with dedicated software of the instrument. Forthe identiﬁcation of 2-DCB we have followed the protocolEN 1785 [3]. In order to improve sensitivity, the selectedions monitoring (SIM) mode was also used, recording ionswith 98 and 112m/z, with a Hewlett–Packard GC/MSsystem.2.3. IrradiationAliquots of 100 g of chicken, constituted by muscle andskin, have been irradiated at 3 and 5 kGy, with a 60Copanoramic irradiator IGS-3. The dose values were calcu-lated using irradiation time and the dose rate (2.00 kGy/h)measured with the Fricke dosimetry.2.4. Microbiological analysesThe following microbiological analyses were conductedon one sample of chicken before and one after irradiation(storage temperature 024 C), according to internationalprotocols: total aerobic microbial enumeration at 30 C,enumeration of coliforms and E. coli, enumeration ofcoagulase-positive Staphylococci, Enterococcus spp. on bileaesculin agar, sulphite-reducing Clostridia, detection ofSalmonella spp.ARTICLE IN PRESSFig. 2. Mass spectrum of the peak corresponding at the retention time of 2-DCB extracted from a sample of chicken irradiated at 5 kGy (up), and thecorresponding spectrum of the 2-DCB standard (down).A. Parlato et al. / Radiation Physics and Chemistry 76 (2007) 1463–1465 14653. Results and discussionThe results of the bacteriological examination on thechicken sample after the radiation treatment at 3 kGy(Table 1) emphasize strong reduction of the contaminatingmicrobiological ﬂora; the residual microbial ﬂora concen-tration is attributable to the dose used in this preliminaryexperiment, relatively low. It is important to mention,however, that the radiation treatment is not allowed to beused to improve originally spoiled food.As for the GC/MS analysis, it was preliminary carriedout on the 2-DCB standard to evaluate its retention time,that was found to be at 13.5min; the corresponding massspectrum showed peaks of ions 98 and 112Da in the ratio4:1, approximately. Moreover, the extract ions chromato-gram of unirradiated samples of muscle and skin of chickendid not show any speciﬁc signal at the retention timeattended for 2-DCB.On the other hand, the 2-DCB, expected from chickenlipids after irradiation, was clearly detected, at expectedretention time 13.5min (Fig. 1); in the corresponding massspectrum both ions 98 and 112Da in the ratio 4:1 werepresent (Fig. 2).Comparable results were obtained with the sample ofmuscle alone (without skin) irradiated at 3 or 5 kGy. Theseresults show that the extraction and analysis procedure setup by us allow to correctly discriminate samples ofirradiated chicken from unirradiated ones, at least soonafter irradiation treatment.To verify its applicability as identiﬁcation method evenon chicken samples stored after irradiation, the GC/MSanalysis was carried out also on the following samples(storage temperature between 20 and 0 C):Sample a: skin irradiated at 3 kGy and stored for 30 days;Sample b: muscle irradiated at 3 kGy and stored for 30days;Sample c: muscle irradiated at 5 kGy and stored for 40days.In the sample a (skin without muscle), the presence of the2-DCB could be clearly detected and conﬁrmed by massspectrum; in sample b (muscle without skin) irradiated andstored as sample a, the 2-DCB was instead almostundetectable. This result indicates the importance of thepresence of the skin in the sample to be analyzed, becausethe skin contains a high concentration of palmitic acid,precursor of 2-DCB. Finally, the 2-DCB was detectable inthe muscle alone (sample c) at the higher dose of 5 kGyafter 40 days storage.4. ConclusionThe main conclusion of this preliminary work is that theGC/MS technique, recommended by the European Stan-dard 1785 as identiﬁcation method of irradiated foodcontaining fat (EN 1785, 1996), can be successfully appliedon chicken irradiated at 3 kGy, soon after irradiation (skinor muscle). After a storage time of 30 days, the identiﬁca-tion is still achievable provided that the investigation iscarried out on the skin, whereas on samples without skinthe technique is applicable only at higher doses.AcknowledgmentsThis work was partially supported by the Universita` diPalermo and by the Istituto Zooproﬁlattico Sperimentaledella Sicilia.ReferencesEN 1785, 1996. Foodstuffs-detection of irradiated food containing fat-gaschromatographic/mass spectrometric analysis of 2-alkylcyclobuta-nones. European Committee for Standardization, Brussels, Belgium.WHO (World Health Organization), 1987. International Consultive groupon food irradiation (ICGFI). Task Force Meeting on the Use ofIrradiation to Ensure Hygienic Quality of Food, 14–18 July, Vienna,Austria, WHO, Geneva, 1987 (WHO/EHE/FOS/87.2).WHO, 1999. High-dose irradiation: wholesomeness of food irradiatedwith doses above 10 kGy. WHO Technical Report Series No. 890,WHO, Geneva, 1999.

Gas chromatographic/mass spectrometric and microbiological analyses on irradiated chicken

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Gas chromatographic/mass spectrometric and microbiological analyses on irradiated chicken

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