Which radiation is used to preserve food by ionizing energy?

• A. Cosmic rays
• B. Alpha rays
• C. X rays
• D. Gamma rays

Answer: (D)

Food irradiation uses ionizing radiation to damage the DNA and cellular machinery of microorganisms and pests, preventing them from growing and extending shelf life. Gamma rays are especially suited for this because they are highly penetrating and can pass through packaging and whole foods, delivering energy throughout the product. They come from radioactive sources like cobalt-60 and cesium-137, and crucially, irradiating food with gamma rays does not make the food radioactive. Alpha particles, by contrast, deposit energy over a very short distance and cannot penetrate packaging, so they aren’t used for this purpose. X rays can also ionize and be used in some facilities, but gamma rays have been the traditional, common method due to practical penetration and cost. Therefore, gamma rays are the radiation used to preserve food by ionizing energy.