Which type of energy is NOT used for food irradiation?

Food irradiation is a process that uses specific types of energy to eliminate pathogens, enhance food safety, and extend shelf life. The energy types used for this process include electron beams, gamma rays, and sometimes X-rays, all of which effectively penetrate food to treat it without significantly raising its temperature.

Gamma rays, which come from cobalt-60 or cesium-137 isotopes, are commonly used in food irradiation because of their penetrating power and ability to kill bacteria and inactivate viruses effectively. Electron beams are high-energy streams of electrons that also effectively kill microorganisms and pests when applied to food. X-rays, while less common, can also be used for food irradiation due to their ability to penetrate food items and provide similar benefits.

Ultraviolet rays, on the other hand, are characterized by their shorter wavelength and limited penetrating ability. They primarily act as a surface treatment, effectively reducing microorganisms on the surface of food rather than processing it through and through. Because of this limitation, ultraviolet rays are not typically used for food irradiation, making it the correct answer in this scenario.