El proceso de la irradiación.pdf

7/28/2019 El proceso de la irradiacin.pdf

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Radiation ProcessingBasics, Current and EmergingApplicationsAjit Singh and Harwant SinghResearch Chemistry Branch, AECL

andAHA Enterprises

Pinawa, MB, ROE 1LaCanada


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What is "USEFUL"(Beauty is in the Eye of the Beholder)

If funding can be found for developinga result into a product or process,preferably from industry, it is "USEFUL"


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Radiation ProcessingExposure of substrate to high energyradiation to give products that are

Safe Unique Useful Produced cost-effectively


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High Energy Radiation a-, p-, and y- radiation X-rays Neutrons Accelerated Electrons Accelerated Positive Ions


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Useful Effects ofHigh EnergyRadiationBased on

Physical effects Chemical effects Biological effects


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Examples Of PhysicalEffects Medical X-rays Radiography of materials Electron beam welding Electron beam heating in metallurgy Colour changes of gemstones Ion Implantation


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Examples OfChemical Effects Crosslinking of polyethylene Water purification Flue gas treatment Polymerization and grafting Curing of latex and rubber


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Examples OfBiological Effects Radiation sterilization of medical products Radiation pasteurization of foods Radiation sterilization of foods Prevention of sprouting of tubers

(potatoes and onions) Delayed ripening of fruits Sewage sludge irradiation


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Time Scale ofRadiolytic Events---, I I I I I I I I r -

10-18 10-15 10-12 10-9 10-6 10-3 1 103 106 109s- .-

........-IChemical processes I----IEnergy DepositionLIPhysical processes I

(

IBiochemical processes IBiological processes


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Desired ProductFormationSubstrate

Substrate Heat

Ions + Free RadicalsIProductI

concerte1 ReactionsorFree Radical Reactions

Irradiation, a cold method to produce ions andfree radicals


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Factors FavouringRadiation Processing Toxicity of traditionally used chemicals,e.g. ethylene oxide and chlorine Uniqueness of product, e.g. heat shrink items Quality of product, e.g. coatings Removal of low concentrations of organiccontaminants, e.g., in drinking water Safe pathogen control Overall cost savings


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Radiation ProcessingConstraints Public concern, particularly about isotopesources Capital cost of radiation sources

Inadequate knowledge of radiationtechnology amongst industrialists andindustriafworkers

Momentum of current technology


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Radiation ProcessingAn Interdisciplinary EndeavourInvolving

Chemistry Physics Biology Engineering Business aspects


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Radiation ProcessingCommercial and R&D Aspects Supply and demand, competition, market trends Support R&D: trouble-shooting, continuedoptimization of process New products/process R&D, as per business

plan


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Radiation ProcessingIn-House vs Service Centre

In-house requires sufficient supply of materialsfor efficient use of the irradiation facility Irradiation Service Centre requires good marketsurveys, assured supply of base load work, andpresence of potential customers within thetarget area


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Current 'Y - and ElectronApplications Coatings Heat shrink products InkslPrinting Silicone release films Roofing materials Wood products Grafting Sterilization Tires Immobilized enzymes Magnetic media Crosslinked PE Adhesives Immobilized Crosslinked films pharmaceuticals

And many moreWoods & Pikaev (1994)


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Electron Processing

H,eat-Shrinkable34%

Coatings120/0Rubber10%Other

6%Foam r - = - = = = : : : : : : ; ~ ~4%WireInsulation34%

-500 Accelerators Worldwide (Saunders,1988; now -1000) -150 'J. - Sources Woldwide for Medical Sterilization andFood Irradiation


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Potential Industrial Applications ofElectron- and "1- Sources

Sterilization of MedicalDisposables RadiationCrosslinking ofPolyethylene Products Sewage SludgeIrradiation Flue Gas Treatment

Immobilization of Enzymesand Pharmaceuticals Viscose Production Food Irradiation Advanced Composites Wood Plastics Composites Mechanical Pulping

See Bradley (1984), Singh and Silverman (1992), Woods andPikaev (1994)


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Further Requirments Entrepreneurs to invest (sterilization, food, PE) Improve properties of advanced composites Radiation effects on cellulose and wood Use ofQjirradiation (waste waters) in othersystems (pulp, pulp mill effluent) Training of industrial workers and industrialistsin radiation technology

Quantum leaps possible (viscose, advancedcomposites)


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Cost Effectiveness ofRadiation ProcessingDepends on

Uniqueness of the desired change Efficiency (chain length) of the radicalreactions Large volumes, use of high power electronaccelerators Use of the lowest energy electronsappropriatefor a process Combination treatment (synergistic effect)


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Food IrradiationSafety and WholesoDleness

of Irradiated FoodsAn Examination of the Scientific Evidence

andApplications


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Safety and Wholesomeness ofIrradiated Foods

The term "wholesome" means nutritious, clean, andotherwise fit for human consumption With regard to irradiated foods, considerations ofwholesomeness or safety for consumption involveaspects of radiological safety, toxicological safety,microbiological safety, and nutritional adequacy Confidence in safety and wholesomeness of irradiatedfood is central to consumer acceptance of such food Consumer acceptance is central to industry acceptance Therefore, when examining questions associated withsafety and wholesomeness of irradiated foods, onemust consider all of the above


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Why Food Irradiation?1. Pathogen Control

Salmonella (chicken) Enteropathogenic E. coli (0157 : H7,Hamburger)2. Substitute for Toxic Fumigants (for Quarantine) Methyl Bromide Ethylene Oxide3. Shelf-life Extension Fruits/Vegetables Meats Fish/Sea Food


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Foodborne Disease is Serious Business Foodborne Disease can Cause Serious Illness and Death Morbidity: diarrhea, fever, kidney failure, birth

defects Mortality: generally the very young and the very old Significant Costs to National Economies Health care costs

Loss of productivity Loss estimates are in bil lions of dollars annuallyfor North America


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Technical Basis for Food Irradiation The beneficial effects of irradiation are due todifferential sensitivities of different biologicalspecies, to inactivation by irradiation Free radicals (OH, H and e-aq) formed from waterpresent in foods are responsible for most of theradiation effects observed in foods The most crucial target of the free radicals is DNA(or the genome) which results in inactivation(killing) of the microbes/insects

It does not significantly affect the nutritive valueof the food


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Basis for Beneficial Effect of Irradiation0 - - -

s:::o.--::::s10..-n(I )Ceft. Background per annum100 ---joIoIlI--..,..-..,..-..,..-..,.....-,...-o-,.- . .-.,.....-..,. ..~

10-1 100 101 10 2 10 3 10 4 10 5 10 6 10 7 10 8

Dose (Gy) These differential senstivities of different functionalentities to inactivation are the basis of beneficialeffects of irradiation


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Achievable Technical Benefits Pathogen control Spoilage microorganism control Insect disinfestation Delay of ripening or maturation Sprout inhibition

Lead to IIConsumer and Social Benefits I

Safer foods Better quality Less spoilage (shelf-life extension) Overall economic gain


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Technology for Food Irradiation Involves the exposure of a food to ionizing radiation

for the purpose of achieving desired technical benefitGamma RaysElectronsX-rays

Food Pathogen concern Limited shelf-life

- - ~ II Processed Food II Improved shelf-life Pathogeneliminated/reduced


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Commercial Irradiation of Spices andVegetable Seasonings in Different Countries

1993991989o 1987

5/1/ / oKor

~ I / / oMex1/ r/ 1/5 V 1/ 1/

oSAf1/ oFra1# I/. ~ oCano v

1/ ~ o Neto USAv / 1// o BelV / Vf9 IV/ oHun1/ / ,f ~ /J ~ 1/ . ,

:E-

2

.--

-n52t-~ o- . - 1- ...--:: (1)~ : Eo s:: 1o

Since 1992, the number of countries irradiatingspices and seasonings has grown enormously


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Countries Irradiating FoodlIngredientsCommerciall CRO

25

20enQ).-10-.. . 15c:~oo 105o

GBR g ~ ~Mt :V

CAN CAN MEXMI::A MEX MEXCUB CUB CUB CUB CUB.aRC:: INS INS INS INS INSARG ARG ARG ARG ARGFIN FIN FIN FIN FIN FIN FIN- DEN DEN DEN DEN DEN DEN DENISR ISR ISR ISR ISR ISR ISR

RR.aTHA THA THA THA THA THA THABRA BRA BRA BRA BRA BRA BRA- RCK RCK RCK RCK RCK RCK RCK RCKCPR CPR CPR CPR CPR CPR CPR CPRYUG YUG YUG YUG YUG YUG YUG YUGUSA USA USA USA USA USA USA USAIR A IR A IRA IRA IR A IRA IRA IR A- CHI CHI CHI CHI CHI CHI CHI CHIFRA FRA FRA FRA FRA FRA FRA FRAHUN HUN HUN HUN HUN HUN HUN HUNNCR NCR NCR NCR NCR NCR NCR NCRRUS RUS RUS RUS RUS RUS RUS RUS- SAF SAF SAF SAF SAF SAF SAF SAFBEL BEL BEL BEL BEL BEL BEL BELNET NET NET NET NET NET NET NETJPN JPN JPN JPN JPN JPN JPN JPN- I

1985 86 87 88 89 90 91 92Year


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List of Foods Cleared fo r Irradiation in Thailand (1986)Product Purpose Clearance Dose (kGy)Potatoes, onions & Sprout inhibition Unconditional 0.15garlicDates Disinfestation Unconditional 1Mangoes, papayas Disinfestation and Unconditional 1delay of ripeningWheat, rice, pulses Disinfestation Unconditional 1Cocoa Beans Disinfestation Unconditional 1Fish and fishery Disinfestation Unconditional 1productsFish and fishery Reduce microbial load Unconditional 2.2productsStrawberries Shelf-life extension Unconditional 3Nham Decontamination Unconditional 4Mooyor Decontamination Unconditional 5Sausage Decontamination Unconditional 5Frozen shrimps Decontamination Unconditional 5Cocoa beans Reduce microbial load Unconditional 5Chicken Decontamination and Unconditional 7shelf-life extensionSpices & condiments, Insect d isinfestation Unconditional 10

dehydratedOnions and onion Decontamination Unconditional 10owder

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