Food irradiation is the process of exposing food to ionizing radiation in order to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration. Irradiation is a more general term of deliberate exposure of materials to radiation to achieve a technical goal (in this context 'ionizing radiation' is implied).
The genuine effect of processing food by ionizing radiation relates to damages to the DNA, the basic genetic information for life. Microorganisms can no longer proliferate and continue their malignant or pathogen activities. Spoilage-causing micro-organisms cannot continue their activities. Insects do not survive or become incapable of proliferation. Plants cannot continue the natural ripening or aging process.
Radiation processing uses highly penetrating x-rays or gamma radiation from sealed radiation sources or a stream of high-energy electrons, traveling at almost the speed of light, to bombard and kill bacteria in products sealed inside their final packaging. In this way the irradiated product remains sterile until the packaging is removed. X-rays, gamma radiation and electron beams sterilize products by exactly the same mechanism of ionization. The main difference between E-beams and radiation is in the depth of penetration.
Since electrons have both mass and charge the penetration depth is approximately ten times less than gamma and X-rays, e.g. 8 cm compared with 80 cm in typical use for radiation processing. This limits E-beam to the treatment of individual packages while gamma and x-rays can treat palletized product.