The ionizing radiation used to preserve food is which form?

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

Answer: (D)

Gamma rays are used to preserve food because they penetrate deeply and reliably destroy microorganisms, insects, and parasites without heating the food significantly or making it radioactive. They come from radioactive sources such as cobalt-60 or cesium-137, delivering a controlled dose that inactivates pests and pathogens while allowing the product to remain in its packaging. The irradiation does not transfer radioactivity to the food itself—the radioactivity stays in the source and diminishes over time. In contrast, alpha particles have very limited penetration and pose hazards if ingested; X rays require external, high-energy equipment and substantial shielding, making them less practical for bulk food irradiation. Cosmic rays occur naturally but are not controllable for industrial processing. Therefore, gamma rays are the preferred form for food irradiation.