STERILIZATION AND PRESERVATION BY IONIZING IRRADIATION

1. STERILIZATION AND PRESERVATION BY IONIZING IRRADIATION I MADE S. UTAMA JURUSAN KETEKNIKAN PERTANIAN FAKULTAS TEKNOLOGI PERTANIAN UNIVERSITAS UDAYANA

2. INTRODUCTION • Research directed toward the use of radiation for the preservation of foods begun in 1945. • Massacusetts Institute of Technology, The United States Army, Quartermaster corps, The Federal Research Center for Food Preservation (Germany), Michigan State University. • Radiation is not a widely used preservation method. • FDA; Food and Drug Law classifies radiation as a food additive. Therefore, this has demanded an animal testing program for establishing safety of process. • The two commercial application: preservation of food and sterilization of medical products.

3. INTRODUCTION • It has limited success in the past decade due to off-flavor and the requirement for sufficient toxicology testing. • 1989, 36 countries approved the marketing of irradiation foods. • The use of irradiation on medical products is increasing; economic and reliable sterilizing agent. • Irradiation is a lethal agent against microorganisms.

4. Comparison of radiation sensitivity of different organisms STERILIZATION OF MICROORGANISMS LETHAL TO INSECTS SPROUTING INHIBITED LETHAL TO HUMANS NO ACUTE EFFECTS Dose (rad) 1 10 102 103 104 105 106 107

5. DESCRIPTION OF RADIATION ENERGY • Radiation can be clasified in two groups: 1) electromagnetic and 2) particle radiation. Electromagnetic radiation: • Various types of ionizing radiation in the electromagnetic spectrum produce bacterial effects by transfering the energy of photon into characteristic ionizations in or near a biological target. • In addition to creating pairs of positive and negative electron, ion can also produce free radicals and activated moleculs, without any appreciable rise in temperature (“cold sterilization”) • Suggested irradiation: microwave, ultraviolet gamma, x rays, and electrons.

6. DESCRIPTION OF RADIATION ENERGY Electromagnetic radiation: • The lethal action of microwave is due to a thermal effect. • X radiation and Gamma radiation; identical in nature but have different origins. Particle Radiation: • The particles ussualy considered of importance in radiation biology are alpha and beta neutron, meson, positron and neutrino. • The currently applicable particles to sterilization is Beta particle or electron. • Alpha particles have limited penetrating ability • Neutrons: is unacceptable since induces radioactivity • Mesons and protons are produced only by expensive, high energy machines.

7. LETHAL EFFECTS OF IRRADIATION ON MICROORGANISMS Intercellular effects • Lesion caused by the direct action of ionizing irradiation on a target molecules are the result of energy being transferred within the target molecule itself • Indirect action due to diffusion of radicals produced in the adjacent volume. • Indirect effects, in a sense, are still with in an organism, but inactive the organism by diffusion to, and by reacting with, a sensitive target site. • An environmental effect caused by radicals and other radiation-produced compounds form extracellularly and still can be lethal to a cell. • Some of this compuds, hydrogen and organic peroxides dan radicals --------postirradiation effects.

8. LETHAL EFFECTS OF IRRADIATION ON MICROORGANISMS Intercellular effects • Ionizing radiations can cause a wide variety of physical and biochemical effects in microorganisms. • The primary cellular target that governs the lost of viability is the DNA molecule of the cell related to the chromosome volume. • The larger volume, the more sensitive the biologic unit was to ionizing radiation.

9. LETHAL EFFECTS OF IRRADIATION ON MICROORGANISMS Environmental effects • One may consider those lethal effects that originate in the menstruum as a type of indirect effect. • The influence of the menstruum can be altered by: 1) using dried preparations in order to restrict the moisture content only to that closely associated with the cell, 2) freezing the menstruum and cells to minimize the migration of free radicals, 3) varying the temperature during irradiation and 4) varying the concentration of the solute or organic material under consideration.

10. LETHAL EFFECTS OF IRRADIATION ON MICROORGANISMS • To decrease or eliminate the microbial population from a surface or within a material by ionizing radiation involves additional considerations. • The microbial contaminants will consist of mixed microflora, distributed in a manner characteristic of the material. • Microorganisms growing as a dense mass in restricted area, or diffuse when dispersed in aliquid, will be destroyed at different rates. • The physiological state of the organism will vary, and the composition of the menstruum surrounding the microorganism may also vary from that of an inert substance to a plant and animal tissue of high complexity.

11. APPLICATION OF IONIZING RADIATION FOR DESTRUCTION OF MICROORGANISMS Two approaches: • Partial or selective destruction (radiation pasteurization) • Complete destruction (radiation sterilization) Radiation Sterilization of food • If the intent is to produce a sterile food product, certain conditions must be met. • For maximal shelf life stability, not only microorganisms but tissue enzymes should be inactivated • The food should be capable of possessing a long storage life without needing refrigeration. • Enzyme require a higher irradiation dosage for inactivation than microorganisms; therefore, a sub sterilization thermal treatment may be required to supplement radiation. • The radiation tolerance of a material should be considered. • The material will act as a shield, will also dter the extent of the penetration of beta and alpha rays.

12. APPLICATION OF IONIZING RADIATION FOR DESTRUCTION OF MICROORGANISMS Radiation Pasteurization of food • the dose employed are considerably lower for pasteurization. • Less off-flavor development • The most numerous organisms decreased, and the spoilage pattern, it is expected, altered and inhibited.

13. APPLICATION OF IONIZING RADIATION FOR DESTRUCTION OF MICROORGANISMS Radiation Pasteurization of food • Radiopasteurization can be extend the shelf life of a variety of fresh food products if certain factors are considered. • the initial number of microorganisms must be reasonably low. • the irradiated product should be maintained at a refrigeration temperature as low as possible. • the packaging must be the proper type • recontamination after irradiation must be minimal • the dosage should be low enough to preserve the characteristic odor and flavor of the fresh product, Note: it must be realized that not all foods, e.g. vegetables and dairy products can tolerate radiation energy without undergoing significant changes in such aspects as flavor and texture.

14. CHEMICAL EFFECTS OF IONIZING RADIATIONS • Capable initiating a vast array of chemical changes; gaseous, liquid and solid system • Ionizing radiation split or “radiolyze “ water. Since many biological systems as well as most foods are aqueous systems, this effect on water is of key importance. • Excited water (H2O)* • Free radicals OH* and H* • Ionized water molecules (H2O)+ • Hydrated electron e-aq

15. CHEMICAL EFFECTS OF IONIZING RADIATIONS • The species then react among themselves or with other components of the system. In pure water and in the presence of air they produce in particular the following: • Hydrogen gas: H2 • Hydrogen peroxide: H2O2 • Water: H2O • Hydronium ion H3O+ • Hydroxyde ion OH-