What is Food Irradiation

1. 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.

2. Irradiation….also known as: • Ionizing radiation • Surface pasteurization • Electronic pasteurization • E-beam sterilization/pasteurization

3. 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.

4. Electromagnetic Spectrum High Frequency Short Wavelengths Low Frequency Long Wavelengths

5. Sources of Ionizing irradiation • Gamma sources of irradiation • X-ray machines • Electron accelerators

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

7. Gamma () rays • Isotope 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 walls • completely penetrates product and packaging (pallets)

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

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

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

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

14. Approximate doses of radiation needed to kill various organisms

15. Typical irradiation D-values of pathogens D-value is equivalent to radiation dose required to reduce a bacterial population 90%

16. Typical irradiation D-values of pathogens D-value is equivalent to radiation dose required to reduce a bacterial population 90%

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

18. 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

19. 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)

20. Shelf life extension of fresh meat

21. 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.

22. Gamma () ray processing facility

23. Gamma () ray processing facility

24. Electron-beam Dosimeter

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

26. Technology Comparison

27. 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

28. 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

29. Web sites of interest • http://www.fsis.usda.gov/OA/topics/irrmenu.htm • http://www.acsh.org/publications/booklets/irradiated.pdf • http://www.ers.usda.gov/Topics/view.asp?T=102818 • http://www.fda.gov/opacom/catalog/irradbro.html • http://www.fsis.usda.gov/OA/topics/irrad-risk.htm