The Linear Accelerator Facility at ISU

Irradiation kills organisms that cause foodborne illness. As in the heat pasteurization of milk, the irradiation process greatly reduces but does not eliminate all bacteria. Irradiated poultry, for example, still requires refrigeration, but would be safe longer than untreated poultry. The energy source is either gamma rays (produced by a radioactive element such as cobalt) or electrons (produced by electricity).

Electron radiation breaks up the bacteria's DNA, making it impossible for the bacteria to reproduce or continue living. ISU's linear accelerator facilityuses electrons.

The Accelerator

Accelerators work on the same principle as a television tube. Instead of being widely dispersed and hitting a phosphorescent screen at low energy levels, the electrons are concentrated and accelerated to 99 percent of the speed of light. This produces rapid reactions on the molecules within the product. The Electron Beam Linear Accelerator machine generates and accelerates electrons to energies of 5, 7.5, or 10 MeV with beam power of up to 10kW.

A stainless steel plate may be placed under the scanning horn to convert the electrons to X-rays at an energy level of 5 MeV to allow very thick penetration at low doses; however, this increases irradiation time considerably.

The Irradiation Process

A cart system moves the products to be irradiated under the electron beam at a predetermined speed to obtain the desired dosage. Multiple carts move products in and out of the irradiation area continuously with throughput up to 500 pounds per hour. Maximum product dimensions are 24 inches wide and 36 inches long. Product thickness depends on density and electron energy. For example, 3.5 inches is the maximum thickness for meat. Using X-rays increases thickness to several feet for various products.

The Meat Laboratory

The meat laboratory, attached to the Linear Accelerator Facility, has complete slaughter, cutting and processing operations with refrigeration and frozen storage. An analytical laboratory may conduct chemical, sensory, microbiological and physical analyses on the irradiated product.

In addition to meat, the irradiation process can be conducted on a wide variety of fresh vegetables, fruits, and spices, as well as some nonfood industrial products.

Learn more about the Iowa State University Linear Accelerator Facility.

• Article History
• Publish Date: 7/16/2003