E-Beam Technology Enters the Food Irradiation Market
When the FDA granted approval for irradiation of meat last December, it described the process as one that subjects "food products to radiation from radioactive or machine sources." The process - dubbed "cold pasteurization" by the food industry - requires either low doses of gamma rays released by cobalt-60 or cesium-137 (radioactive source), or streams of high-energy electrons from an accelerator (machine source).
APA, Inc., a Nebraska-based engineering, architectural and consulting firm, has spent more than three years studying electron beam radiation's applicability in the food processing industry. In July 1996 the company formed a strategic agreement with Titan Scan Systems, a California company that builds integrated electron beam systems for sterilizing disposable medical products. With their combined capabilities, the two companies are now offering meat processors integrated electron beam systems that include strategic planning, facility design, shielding design, dosimetry systems development, operator training, regulatory compliance and safety compliance.
The Technology
Electron beam processing utilizes high-energy electrons as its sterilizing agent. Electrons are accelerated to near the speed of light by means of a linear accelerator. The resulting energies range normally from 3 to 10 million electron volts. The FDA approved electron sources for food irradiation at a maximum energy of 10 MeV. The electron volt [eV] is the amount of energy acquired by an electron when it is accelerated by one volt in a vacuum.
As electrons are scanned through product, they interact with packaging and product materials, creating a variety of secondary particles. These secondary particles break the DNA chain of microorganisms on and within the package, rendering the microorganisms incapable of reproduction.
The primary components required for electron beam processing are an electron beam accelerator and scanning horn, a biological shield to enclose the radiation treatment area, a product handling system to move the product through the electron beam, an air exhaust system to remove ozone, a cooling water system to remove heat from the accelerator during operation, reliable electrical power conditioning system, a safety interlock system to prevent workers from entering the radiation treatment area, and process monitoring equipment to ensure that the product has received the proper dose within regulatory limits.
Food irradiation systems would be based on the same design principle as seen here in a medical product sanitation facility.
Titan's linear accelerator system for direct electron treatment of food products is based on standard Varian components, which are used throughout the medical industry for diagnostic x-ray equipment and therapeutic particle accelerators.
The electron beam irradiation machines cost between $2 and $4 million apiece, including operating and capital costs, said Spencer Stevens, president of APA. Based on a study his company did involving a large meat packer with 2 separate 15 kW units, the cost of electricity would be about $400,000 a year. Stevens estimates that meatpackers' final cost to irradiate meat breaks down to about 1.5 to 2 cents a pound.
University Research
Electron beam irradiation of beef has been studied at the Iowa State University Meats Laboratory for more than ten years. The University's irradiation system uses a linear accelerator that generates and accelerates electrons to energies of 5, 7.5, or 10 MeV with beam power of up to 10kW. This produces rapid reactions on the molecules within the product, ridding the meat of microbial pathogens and other contaminates. According the Dennis Olson, the Iowa State professor of animal science, food science and human nutrition who first proposed installing the irradiation operation, "If a company wants to be sure not to have a [pathogen] problem before the meat leaves the plant, you have two choices. You either cook it, or you irradiate it." Olson believes the biggest benefit of irradiation is that packaged products can be kept contaminant-free until opened in a restaurant or at home, reducing opportunities for contamination of the meat.
Hamburger Patty Processing
Electron beam treatment is well suited for treating single, thin layers of product on a continuous basis. One food processing system that could readily accommodate this technology is hamburger patty production.
For most large hamburger processing facilities, beef trimmings are blended, fed into patty formers, stamped out onto a transport conveyor, and finally flash frozen and packaged. APA's preliminary design efforts have concluded that the optimum location for an electron beam system would be after freezing. New vacuum packaging systems for hamburger patties allow treatment of packaged products and simplify product handling. Because of the very thin product configuration, utilizing two-sided treatment with lower energy accelerators reduces shielding requirements and minimizes the system footprint. This would allow integration of the linear accelerator system into existing processing facilities without significant processing line modification or equipment relocation.
Poultry Processing
Case-ready poultry products such as boneless chicken breasts are also well suited for electron beam processing. Design concepts for poultry processing include utilization of the packaging material as a conveyance medium through the irradiation treatment area in order to simplify the product handling system and shielding design, and serpentine product flow paths as a method to shield product handling penetration into the radiation treatment area. These systems are being developed to handle a wide variety of poultry product configurations to support the batch type processing of specialty poultry products.
Advantages/Disadvantages
According to APA, electron beam technology is especially practical because the radiation dose can be delivered to the product very rapidly. And compared to cobalt-60, which emits gamma rays in all directions, electron-beam systems focus the electrons as a beam directly on the product being treated. Hence, greater processing flow rates and more uniform dose distributions can be achieved and critical product temperature limitations can be maintained.
In terms of safety, electron beam technology provides irradiation without employing radioisotopes. When the switch is "off", electrons are no longer produced, eliminating the source of irradiation. And without radioisotopes, no toxic or radioactive wastes are generated.
Electron-beam systems can be optimized for treatment of a specific product in case-ready packages. Variations in electron energy, machine power, conveyor belt speed, one- or two-sided treatment allow designs to be integrated into a production line for a wide range of products.
One disadvantage is that electron beams have very low penetration ability and cannot be used for irradiation of thick materials.
Who's Going First?
With FDA approval complete and USDA approval of the rules expected this summer, there is nothing to stop large-scale use of irradiation in meat processing. And yet, as of this moment, no one has taken the leap.
Back in July 1996, in answer to a question pertaining to food safety, Mr. Philip Fletcher, chairman and CEO of ConAgra said, "One of the ways that we obviously could attack the problem of either E. coli or salmonella is with the use of irradiation. However, the American consumer simply will not accept irradiation at this point. That's an education (gap) we must somehow fill as we go forward, because it's really sad to have a technology that can ensure that a food has absolutely no bacterial contamination and are unable to use it because of its lack of acceptance."
Whether the "gap" is any closer to being filled remains to be seen. But sooner or later, some company will have to test the water of consumer readiness. For a company like APA, the hope is for sooner.
By Pam Ahlberg
For more information:
APA, Inc., 9300 Underwood Ave., Suite 400, Omaha, NE 68114. Tel: 402-390-9300; Fax: 402-390-2005.
The Titan Corp., 3033 Science Park Rd., San Diego, CA 92121. Tel: (619) 552-9500; Fax: (619) 552-9645.
Linear Accelerator Facility, Iowa State University, 194 Meat Laboratory, Ames, IA 50011. Tel: (515) 294-5310; Fax: (515) 294-6328.