Most irradiated food tastes the same as non-irradiated.
Flavor changes depend on the type of food being irradiated, the irradiation dose, and the temperature during treatment.
Many fruits and vegetables are unchanged by low dose irradiation. Irradiation can substitute for insect quarantine treatments that damage fruit quality, so irradiated fruit may taste better. Dried fruit softens slightly and is easier to rehydrate.
Poultry, pork and other meats show little or no flavor change at the level of irradiation currently approved by the FDA. High dose irradiation needed to prepare food for astronauts is done while the meat is frozen to preserve flavor.
Milk and certain other dairy products develop off-flavors even at low treatment levels. No one has submitted a petition to the FDA to irraidate these products.