What is Food Irradiation Food irradiation is a process in which food products are exposed to a controlled amount of radiant energy to increase the safety of the food and to extend shelf life of the food Like pasteurization of milk and pressure cooking of canned foods, treating food with ionizing radiation can kill bacteria and parasites that would otherwise cause foodborne disease.

Irradiation….also known as: Ionizing radiationIonizing radiation Surface pasteurizationSurface pasteurization Electronic pasteurizationElectronic pasteurization E-beam sterilization/pasteurizationE-beam sterilization/pasteurization

Ionizing radiation When radiation strikes other material, it transfers energy. This can cause heating, as with microwave cooking, or if there is enough energy, it can knock electrons out of the material bombarded, breaking the molecular structure-thus leaving ions (free radicals) hence the name ionizing radiation.

Electromagnetic Spectrum Low Frequency Long Wavelengths High Frequency Short Wavelengths

Sources of Ionizing irradiation Gamma sources of irradiationGamma sources of irradiation X-ray machinesX-ray machines Electron acceleratorsElectron accelerators

Gamma (  ) rays energy comes from decay of radioactive isotopesenergy comes from decay of radioactive isotopes –Cobalt-60 (half life of 5.3 years) Produced by neutron bombardmentProduced by neutron bombardment –Cesium-137 (half life of 30 years) By-product of spent nuclear fuelBy-product of spent nuclear fuel

Gamma (  ) rays Isotope is contained and stored in pool of water and raised when produce is to be exposed to  - raysIsotope is contained and stored in pool of water and raised when produce is to be exposed to  - rays facility is concrete chamber with 6-12’ thick wallsfacility is concrete chamber with 6-12’ thick walls completely penetrates product and packaging (pallets)completely penetrates product and packaging (pallets)

Electron-beam electricity is power source-switch on and offelectricity is power source-switch on and off uses stream of high-energy electrons accelerated at near the speed of lightuses stream of high-energy electrons accelerated at near the speed of light electrons are showered on the productelectrons are showered on the product facilities are shielded with concrete or steel wallsfacilities are shielded with concrete or steel walls penetrates approximately 2-3” of product and packagingpenetrates approximately 2-3” of product and packaging ideal for thin ground beef pattiesideal for thin ground beef patties

How ionizing radiation works Electrons disrupt the DNA chain either destroying or preventing reproduction of the organism

Factors affecting irradiation effectiveness against microorganisms in foods Growth phase of microorganismGrowth phase of microorganism Type of food (lean vs fat)Type of food (lean vs fat) Moisture content (water level)Moisture content (water level) Temperature of food (frozen vs heated)Temperature of food (frozen vs heated) Presence of oxygen (aerobic vs anaerobic)Presence of oxygen (aerobic vs anaerobic)

Irradiation Dosage Dose - amount of energy transferredDose - amount of energy transferred –rad - old unit –gray (Gy) - new unit –1 kGy = 100,000 rad 1 chest X-ray =.01 rad1 chest X-ray =.01 rad natural background = 0.1 rad/yearnatural background = 0.1 rad/year

Approximate doses of radiation needed to kill various organisms OrganismsDose (kGy) Higher animals0.005 to 0.1 Insects0.01 to 1 Non-spore forming bacteria0.5 to 10 Bacterial spores10 to 50 Viruses10 to 200

Typical irradiation D-values of pathogens kGy OrganismFresh (refrigerated)Frozen Camplobacter jejuni0.08 – – 0.32 E. Coli O157:H70.24 – – 0.44 Staphlococcus aureus0.26 – – 0.45 Salmonella spp.0.30 – – 1.30 Listeria monocytogenes0.27 – – 1.30 D-value is equivalent to radiation dose required to reduce a bacterial population 90%

Typical irradiation D-values of pathogens kGy OrganismFresh (refrigerated) Clostridium botulinum spores 1.00 – 3.60 Toxoplasma0.40 – 0.70 Trichinella spiralis0.30 – 0.60 D-value is equivalent to radiation dose required to reduce a bacterial population 90%

Destruction of microorganisms Irradiation kGy dose 1 D value Contains 10 microorganisms 1 microorganism survives Irradiation kGy dose 2 D value Contains 10 microorganisms 1 microorganism survives/ 10 steaks

Pasteurization To reduce microorganisms but not to sterilize the product Purpose is to destroy pathogenic microorganisms to make food safe This is normally 5 to 7 D values

Effect of irradiation on shelf life of fresh meats Spoilage organisms, especially pseudomonads, are susceptible to low dose irradiation Spoilage of low dose irradiated meats may be due to yeast, LAB, or Moraxella spp. (increased lag time)

Shelf life extension of fresh meat Meat product Dose kGry Untreated shelf life (days) Irradiated shelf life (days) Beef cuts Ground beef Pork loins34190 Ground pork1812

How does irradiation food processing operation work? Food is packed in containers and moved by conveyer belt into a shielded room. Food is exposed briefly to a radiant-energy source. (The amount of energy depends on the food.) Food is left virtually unchanged, but the number of harmful bacteria, parasites and fungi is reduced and may be eliminated.

Gamma (  ) ray processing facility

Electron-beam Dosimeter

Levels of Food Irradiation Radurization (low) < 1 kGyRadurization (low) < 1 kGy –vegetable sprouting, fruit ripening, insect sterilization Radicidation (medium) 1-10 kGyRadicidation (medium) 1-10 kGy –kills most pathogens and many food spoilage organisms, kills insects and parasites – Rappertization (high) > 10kGyRappertization (high) > 10kGy –can sterilize by killing all bacteria and viruses

Technology Comparison Electron Beam Cobalt-60 Technology Technology Focused beam of electrons (10 MeV energy) Photons created from decay of radioactive material AdvantagesSafe ON/OFF Cost efficient In-Line capability Compact systems High dose rate = reduced oxidation Increased ability to penetrate dense material Process pallet load DisadvantageReduced ability to penetrate dense material (3 ½ in. of highly dense product – approx. 8 meat patties high) Cannot be turned OFF – always emitting gamma radiation Requires source disposal and replenishment Low dose rate = increased oxidation Consumer perception

Meat Irradiation December 23, 1999 Federal Register Effective date – February 22, 2000 Ionizing radiation approved for use –Cobalt-60, Cesium-137, X-ray machines, Electron accelerators Dosage –4.5 kGy if refrigerated –7.0 kGy if frozen

Safety and efficacy of food irradiation The following statements are in the Federal Register (12/23/1999) The safety and efficacy of food irradiation, as demonstrated by numerous experiments and studies, is widely accepted by Federal regulatory agencies and national and international food and public health organizations FDA examined numerous studies on the chemical effects of radiation, the impact of radiation on nutrient content of foods, potential toxicity concerns and effects on microorganisms in or on irradiated products. FDA concluded that irradiation is safe in reducing disease-causing microbes in or on meat food products and it does not compromise the nutritional quality of treated products. The World Health Organization, Food and Agriculture Organization, American Medical Association and American Dietetic Association endorse food irradiation

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