(From USDA's Food Irradiation Overview)
Food irradiation is the controlled process of treating foods with ionizing radiation. Ionizing radiation is a part of the electromagnetic energy spectrum that also includes radio and television waves, microwaves, infrared radiation, visible light, and ultraviolet radiation. Ionizing radiation has a shorter wavelength and consequently higher energy than other radiation in the spectrum. That energy is great enough to break chemical bonds in molecules and result in chemical changes in foods and in pests that contaminate food. When a sufficient number of critical bonds are broken in pests or bacteria, those organisms are killed. Breaking bonds in molecules of fresh foods can inhibit sprouting and other mechanisms that are associated with ripening.
Click here for an explanation of the process
Prepared Summer 1997 by Bernadene Magnuson, Ph.D.
University of Idaho, Dept. of Food Science and Toxicology - EXTOXNET FAQ Team.