Science of Irradiation of meat辐照肉品科学

WhatisFoodIrradiationFoodirradiationisaprocessinwhichfoodproductsareexposedtoacontrolledamountofradiantenergytoincreasethesafetyofthefoodandtoextendshelflifeofthefoodLikepasteurizationofmilkandpressurecookingofcannedfoods,treatingfoodwithionizingradiationcankillbacteriaandparasitesthatwouldotherwisecausefoodbornedisease.Irradiation….alsoknownas:IonizingradiationSurfacepasteurizationElectronicpasteurizationE-beamsterilization/pasteurization

IonizingradiationWhenradiationstrikesothermaterial,ittransfersenergy.Thiscancauseheating,aswithmicrowavecooking,orifthereisenoughenergy,itcanknockelectronsoutofthematerialbombarded,breakingthemolecularstructure-thusleavingions(freeradicals)hencethenameionizingradiation.ElectromagneticSpectrum

LowFrequencyLongWavelengthsHighFrequencyShortWavelengthsSourcesofIonizingirradiationGammasourcesofirradiationX-raymachinesElectronacceleratorsGamma(

)raysenergycomesfromdecayofradioactiveisotopesCobalt-60(halflifeof5.3years)ProducedbyneutronbombardmentCesium-137(halflifeof30years)By-productofspentnuclearfuelGamma(

)raysIsotopeiscontainedandstoredinpoolofwaterandraisedwhenproduceistobeexposedto

-raysfacilityisconcretechamberwith6-12’thickwallscompletelypenetratesproductandpackaging(pallets)Electron-beam

electricityispowersource-switchonandoffusesstreamofhigh-energyelectronsacceleratedatnearthespeedoflightelectronsareshoweredontheproductfacilitiesareshieldedwithconcreteorsteelwallspenetratesapproximately2-3〞ofproductandpackagingidealforthingroundbeefpattiesHowionizingradiationworksElectronsdisrupttheDNAchaineitherdestroyingorpreventingreproductionoftheorganismFactorsaffectingirradiationeffectivenessagainstmicroorganismsinfoodsGrowthphaseofmicroorganismTypeoffood(leanvsfat)Moisturecontent(waterlevel)Temperatureoffood(frozenvsheated)Presenceofoxygen(aerobicvsanaerobic)

IrradiationDosageDose-amountofenergytransferredrad-oldunitgray(Gy)-newunit1kGy=100,000rad

1chestX-ray=.01radnaturalbackground=0.1rad/year

ApproximatedosesofradiationneededtokillvariousorganismsOrganismsDose(kGy)Higheranimals0.005to0.1Insects0.01to1Non-sporeformingbacteria0.5to10Bacterialspores10to50Viruses10to200Typicalirradiation

D-valuesofpathogenskGyOrganismFresh(refrigerated)FrozenCamplobacterjejuni0.08–0.200.21–0.32E.ColiO157:H70.24–0.270.31–0.44Staphlococcusaureus0.26–0.600.30–0.45Salmonellaspp.0.30–0.800.40–1.30Listeriamonocytogenes0.27–1.000.52–1.30D-valueisequivalenttoradiationdoserequiredtoreduceabacterialpopulation90%Typicalirradiation

D-valuesofpathogenskGyOrganismFresh(refrigerated)Clostridiumbotulinumspores1.00–3.60Toxoplasma0.40–0.70Trichinellaspiralis0.30–0.60D-valueisequivalenttoradiationdoserequiredtoreduceabacterialpopulation90%DestructionofmicroorganismsIrradiationkGydose1DvalueContains10microorganisms1microorganismsurvivesIrradiationkGydose2DvalueContains10microorganisms1microorganismsurvives/10steaksPasteurizationToreducemicroorganismsbutnottosterilizetheproductPurposeistodestroypathogenicmicroorganismstomakefoodsafeThisisnormally5to7DvaluesEffectofirradiationonshelflifeoffreshmeatsSpoilageorganisms,especiallypseudomonads,aresusceptibletolowdoseirradiationSpoilageoflowdoseirradiatedmeatsmaybeduetoyeast,LAB,orMoraxellaspp.(increasedlagtime)ShelflifeextensionoffreshmeatMeatproductDosekGryUntreatedshelflife(days)Irradiatedshelflife(days)Beefcuts214-2170Groundbeef1.58-1026-28Porkloins34190Groundpork1812Howdoesirradiation

foodprocessingoperationwork?Foodispackedincontainersandmovedbyconveyerbeltintoashieldedroom.Foodisexposedbrieflytoaradiant-energysource.

(Theamountofenergydependsonthefood.)Foodisleftvirtuallyunchanged,butthenumberofharmfulbacteria,parasitesandfungiisreducedandmaybeeliminated.Gamma(

)ray

processingfacilityGamma(

)ray

processingfacility

Electron-beam

DosimeterLevelsofFoodIrradiation

Radurization(low)<1kGyvegetablesprouting,fruitripening,insectsterilizationRadicidation(medium)1-10kGykillsmostpathogensandmanyfoodspoilageorganisms,killsinsectsandparasites

Rappertization(high)>10kGycansterilizebykillingallbacteriaandvirusesTechnologyComparisonElectronBeamCobalt-60TechnologyFocusedbeamofelectrons(10MeVenergy)PhotonscreatedfromdecayofradioactivematerialAdvantagesSafeON/OFFCostefficientIn-LinecapabilityCompactsystemsHighdoserate=reducedoxidationIncreasedabilitytopenetratedensematerialProcesspalletloadDisadvantageReducedabilitytopenetratedensematerial(3½in.ofhighlydenseproduct–approx.8meatpattieshigh)CannotbeturnedOFF–alwaysemittinggammaradiationRequiressourcedisposalandreplenishmentLowdoserate=increasedoxidationConsumerperceptionMeatIrradiationDecember23,1999FederalRegisterEffectivedate–February22,2000IonizingradiationapprovedforuseCobalt-60,Cesium-137,X-raymachines,ElectronacceleratorsDosage4.5kGyifrefrigerated7.0kGyiffrozenSafetyandefficacyof

foodirradiationThefollowingstatementsareintheFederalRegister(12/23/1999)Thesafetyandefficacyoffoodirradiation,asdemonstratedbynumerousexperimentsandstudies,iswidelyacceptedbyFederalregul