How it works
Irradiation is the process of exposing a substance to ionizing radiation whose source is photons ( γ -rays, x rays), or high energy electrons. Gamma rays are produced by radioactive isotopes such as cobalt-60 and cesium-137. These isotopes have been approved for use in food because the γ -rays they produce have insufficient energy to induce radioactivity in foods. On the other hand electron beams are produced by electron accelerators, such as Van de Graff generators or linear accelerators. These machines are power limited, to assure that they cannot induce radioactivity in foods. Finally, x rays are produced by the collision of high energy electrons, produced by linear accelerators,
Irradiation destroys bacteria primarily by disrupting the DNA in individual cells. A second way is by passing a photon of energy very close to the DNA and forms a peroxide radical (from oxygen in the air) in the cell cytoplasm. The peroxide radical then oxidizes part of the DNA.

Purpose
Prevention of Foodborne Illness – irradiation can be used to effectively eliminate viruses and bacteria that cause foodborne illness, such as Salmonella and Escherichia coli (E. coli).
Preservation – irradiation can be used to destroy or inactivate organisms that cause spoilage and decomposition and extend the shelf life of foods.
Control of Insects – irradiation can be used to destroy insects in or on tropical fruits imported into the United States. Irradiation also decreases the need for other pest-control practices that may harm the fruit.
Delay of Sprouting and Ripening – irradiation can be used to inhibit sprouting (e.g., potatoes) and delay ripening of fruit to increase longevity.
Sterilization – irradiation can be used to sterilize foods, which can then be stored for years without refrigeration. Sterilized foods are useful in hospitals for patients with severely impaired immune systems, such as patients with AIDS or undergoing chemotherapy. Foods that are sterilized by irradiation are exposed to substantially higher levels of treatment than those approved for general use.
Concerns
Concerns about food irradiation fall into two categories: one relating to the technology and the second concerning to the