Published on February 27, 2014
SOME OF THE THINGS YOU NEED TO KNOW ABOUT RADIATION STERILIZATION in microbial growth control and food preservation ARRIZA, 2014
What is Radiation? Radiation is energy that comes from a source and travels or penetrate through some material or through space.
Types of Radiation Ionizing radiation is uses short wavelength. It is composed of particles that individually carry enough kinetic energy to liberate an electron from an atom or molecule, ionizing it. The types of ionizing radiation potentially available for the preservation of foods include alpha and beta particles, and gamma rays and x rays. (1)
Types of Radiation Non-ionizing radiation uses longer wavelength carries less energy to produce charged ions. Nonionizing radiation loses the ability to penetrate substances, and can only be used for sterilizing surfaces. Most commonly used non-ionizing radiation include infrared and ultraviolet radiation. (2)
Radiant Energy Spectrum
Radiant Energy Spectrum
Ionizing Radiation Direct action occurs when alpha particles, beta particles or x-rays create ions which physically break one or both of the sugar phosphate backbones or break the base pairs of the DNA. This interaction may result in the cells failing to reproduce or cause ‘direct’ interference with a critical cellular system.
Ionizing Radiation Indirect action occurs when alpha particles, beta particles or x-rays creates free radicals. Free radicals are molecules that are highly reactive due to the presence of unpaired electrons on the molecule. Usually interacts with H2O in the cell. This interaction forms hydrogen (H+)and hydroxyl (OH-) ions
e- OHHO0 H+ H0
Direct vs. Indirect Action
Non-ionizing Radiation Ultraviolet radiation is commonly used. It damages the DNA by causing covalent bond formation between adjacent thymines on the same strand, forming a thymine dimer. DNA repair mechanisms are known in both prokaryotic and eukaryotic cells .If the damage is severe enough, the cell cannot repair the damage and will die.
Food Irradiation Food irradiation is the application of radiation, in the form of ionizing energy, to foods. The result is similar to conventional pasteurization and is often called "cold pasteurization”. The food irradiation process uses three types of ionizing radiation sources: •cobalt-60 gamma sources •electron beam generators •x-ray accelerators
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