Gamma rays are similar to ultraviolet light or microwaves, but are of greater energy. Also, as the food never comes into contact with the source, the food cannot become contaminated with radioactive material.
Irradiated food does have limitations, though.
Not all irradiated food can be frozen or canned, and not all types of food can be irradiated, e.g., dairy products and whole eggs. A proposed new standard on the irradiation of foods has been released for public comment. If adopted, NZ retailers will be able to both import and sell irradiated foods, so long as they comply with the standard. It is thought that very little food coming into NZ would need to be irradiated. Submissions due by 26 March 1999.