Irradiation of foods must be approved by the U.S. Food and Drug Administration (FDA). Some applications also require U.S. Department of Agriculture (USDA) approval. USDA's Food Safety Inspection Service must approve both the process and the facility for irradiation of meat and poultry. USDA's Animal and Plant Health Inspection Service must approve irradiation for plant quarantine protection. FDA approval comes only after extensive testing demonstrates that the proposed dose of irradiation effectively eliminates the pathogen or insect of concern and does not generate toxic or carcinogenic chemicals in the food.
FDA has approved irradiation for several foodstuffs, including spices and herbs, potatoes, pork, poultry and other meats, fruits, and vegetables. It sets the maximum dose based on test results. The USDA may also set a minimum dose to assure effectiveness, for example, to assure the destruction of an insects on plants in quarantine control.
On this page:
- How does irradiation kill bacteria?
- How does irradiation affect the food itself?
- How is safety tested?
- Can irradiation make food radioactive?
- What are the alternatives to food irradiation?
- How do I know if food has been irradiated?
How does irradiation kill bacteria?
When ionizing radiation strikes bacteria and other microbes, its high energy breaks chemical bonds in molecules that are vital for cell growth and integrity. As a result, the microbes die, or can no longer multiply and cause illness or spoilage.
Breaking chemical bonds with radiation is known as radiolysis.
How does irradiation affect the food itself?
Ionizing radiation also breaks some of the chemical bonds within the food itself. The effects of chemical changes in foods are varied. Some are desirable, others are not.
Examples of some food changes are:
- changes in structure of certain foods too fragile to withstand the irradiation, for example, lettuce and other leafy vegetables turn mushy
- slowed ripening and maturation in certain fruits and vegetables lengthens shelf-life
- reduction or destruction of some nutrients, such as vitamins, reduces the nutritional value (the effect is comparable to losses in heat pasteurization)
- alteration of some flavor compounds
- formation of compounds that were not originally present requires the strict control of radiation levels
- generation of free radicals, some of which recombine with other ions.
These effects are the result of radiolysis. Whether the products of radiolysis in food are all innocent from a human health perspective is still debated. However, years of experience in food irradiation has not demonstrated any identifiable health problems.
How is safety tested?
Safety testing of irradiated foods has taken place since the early 1950's. Irradiated foods have been fed to several species of animals, some up to 40 generations. Additionally, irradiated foods have been evaluated chemically.
The Food and Drug Administration (FDA)must approve any use of irradiation on food and U.S. Department of Agriculture (USDA) Food Safety Inspection Service must approve the process and the facility if meat and poultry products are involved. USDA's Animal and Plant Health Inspection Service approves use of irradiation for plant quarantine protection.
Several foods have been approved in the U.S. The FDA sets the maximum dose permitted on food based on what was petitioned to assure safety. The USDA sets the minimum dose on some foods to assure the desired effects such as destruction of microorganisms or effect insect quarantine control.
Assessing the safety of irradiated foods has involved investigation in the following areas:
- radiation chemistry
- general toxicology/animal testing
- nutrition of irradiated foods
- microbiology of irradiated foods
Can irradiation make food radioactive?
No. Food does not come in contact with radioactive material during food irradiation, and cannot be contaminated this way. Radiation that is too energetic, however, can disrupt the energy balance in the nuclei of food atoms, making them unstable (radioactive). This is known as induced radioactivity.
Electron and x-ray beams can be energetic enough to induce radioactivity. To prevent induced radioactivity, FDA limits the energy of the radiation from these sources to less than 4 mega-electron volts. Radiation from cobalt-60 sources is not energetic enough to induce radioactivity.
What are the alternatives to food irradiation?
There are many traditional methods for preserving foods, such as drying, smoking, salt or sugar curing, and canning. These methods generally alter the flavor and chemical composition of the food. More modern methods, such as heat pasteurization and refrigeration or freezing, as well as freeze drying, are also common. Decisions about which method to use for individual foods and circumstances must weigh feasibility, effectiveness, and cost as well as the chemical changes each method causes in the food. The FDA emphasizes that no preservation method is a substitute for safe food handling procedures.
How do I know if food has been irradiated?
A distinctive logo, the Radura, on the labels of packaged or bulk food identifies irradiated food.
This page describes and illustrates the labeling of irradiated foods.