Eradication Through Irradiation

  "Irradiation is the only technology, other than thorough cooking, that can destroy all harmful bacteria on raw foods," says Patrick Boyle, president and CEO of the American Meat Institute, Arlington, VA.

  "Irradiation will give us a good intervention strategy for controlling foodborne pathogens, such as E. coli 0157:H7, Salmonella species, Campylobacter and emerging pathogens, such as Salmonella DT104 on both poultry and red meats, preventing them from reaching the consumer or cross-contaminating other foods," says Donald Thayer, research leader for food safety, USDA Agricultural Research Service (ARS), Eastern Regional Research Center, Wyndmoor, PA. As many as 9,000 U.S. deaths annually are caused by foodborne bacteria, according to a news release from the Council for Agricultural Science and Technology, "yet scientifically proven safe, low doses of pasteurizing radiation can kill over 99% of most foodborne bacteria." E. coli 0157:H7 alone causes 8,000 to 20,000 cases of disease each year in the United States, according to the IFIC study. "Consumers embraced the food-safety benefits of irradiation," Thayer notes, "but not as a substitute for safe food production, processing and handling."

  FSIS is in the middle of HACCP rule-making for red meats and poultry, and irradiation will be incorporated into the program.

  "Irradiation can be applied as a terminal process," notes Peter Kunstadt, product manager, MDS Nordion, Inc., Kanata, Ontario, Canada. "In other words, irradiation can be applied after final packaging, so that re-contamination becomes a non-issue. This is something that the medical-sterilization industry has been taking advantage of for a long time." This is a very important consideration, especially for products like ground beef, but packaging materials also are one of irradiation's initial challenges.

  "Irradiation is a process that very slightly increases temperature," Kunstadt explains, "so it can be regarded as a cold process." The IFIC study notes that consumers identified with the description "cold pasteurized (irradiated) to eliminate harmful bacteria." As noted earlier, 1 kGy increases the temperature of the product by 0.43ºF. The maximum permitted for fresh meat is 4.5 kGy, so potential temperature increase is minor. "The products after the treatment have been minimally affected," Kunstadt notes, "so you can actually market a relatively fresh product."

  Irradiation also can lengthen shelf life, particularly in fruits and vegetables. These food items are currently being irradiated in the United States to eliminate insects and spoilage organisms, and also to prevent overripening or sprouting. FDA has approved an ionizing radiation dose of up to 1.0 kGy for growth and maturation inhibition of fresh foods, and for insect disinfestation. Potatoes and onions are irradiated to prevent sprouting, and the shelf life of some onions can be extended to three months. Irradiated mushrooms can be stored for three weeks without browning or cap separation, and strawberries can be refrigerated for three weeks without decay or shrinkage. Tomatoes can be harvested fully ripened. Fruits are "fresh-looking, they taste fresh, and they are organoleptically fresh," according to Kunstadt.

  Irradiation leaves no chemical residuals, which can be regarded as an advantage, but could lead to re-infestation of flours or grains. At the port of Odessa, Ukraine, as much as 400,000 tons of imported wheat per year have been irradiated with an electron beam to kill insects. This process was developed by the U.S. Army and ARS, and approved for use in the United States in 1963. Irradiation has strong potential to replace methyl bromide as a fumigant for fruits, grains and vegetables, and is currently used in the United States to eliminate insects and bacteria in spices, herbs and dry vegetable seasonings. The total spice currently irradiated is "less than or equal to 25%, but growing rapidly, replacing ethylene oxide as a fumigant," Thayer says.

  Facilities exist to handle a large amount of product: One plant currently processes about 40 million lbs. of spice per year alone, but shipping and handling could pose a problem. For larger, on-site facilities, "construction of new plants - isotopic or electron beam - there's lead time there," notes Thayer, "although one company has developed self-contained units (with cesium-137) to handle single pallet loads."

  Each radiation technology has its pros and cons, and the scale of production will probably determine which method is chosen. One choice would be to ship product to an existing facility for final processing. For large quantities of product, a cobalt-60 plant could work very well, but would require a large capital commitment. Cobalt-60 must be stored underwater when not in use. Stainless steel tubes containing cobalt pellets are removed from the water, and product is passed through the radiation field. This requires a maze of thick concrete walls, many safety precautions, proper training, and strict procedures. Electron beam and X-ray systems are currently being used for medical supplies, and require safety precautions and shielding when in use, but none when they are turned off. Electron beams have low penetrating power, but can deliver a radiation dose to a thin sample, such as hamburger patties, very rapidly. This also has been used to irradiate grain at the port of Odessa.

  A second major hurdle is packaging. There is a lack of FDA-approved polymers for irradiated meat. "That presents a problem: how to process meat in a way that the customer is used to seeing it in the grocery store with existing packaging approvals," Thayer says.

  "Somebody must petition FDA for clearance of new polymers," he says, "and there are no laminated materials currently approved." The meat, plastics, resins and retail industries recognize this as a serious problem. In the past few months, the American Meat Institute and the National Center for Food Safety and Technology have sponsored a series of meetings to identify key polymers, adhesives and additives, and to collaborate on a rapid solution to the problem. Existing data on each material must be assembled and supplemented, as required, to submit the necessary petitions to FDA.

  A third major hurdle is consumer education. Certain fears have been expressed by those seeking to block further use of irradiation. But food doesn't come in contact with radioactive material, and the food itself does not "become radioactive." Radiation has a minor effect on certain sensitive vitamins, such as B1 and vitamin C (ascorbic acid), but any effects are certainly within the range of effects caused by other food-processing forms. Flavor differences are relatively minor at the dosages permitted in the regulations.

  The IFIC study and other consumer studies have shown that consumers are willing to accept irradiated foods, and that consumer education will significantly increase acceptance levels.

  "Virtually all consumers felt that the mainstream media and consumer brochures from government and supermarkets were the best way to educate the public about food irradiation," according to an IFIC press release. "On government and health authorities, consumers wanted endorsements of food irradiation by figures like the U.S. Surgeon General."

  Food irradiation has been endorsed as a recognized technology for enhancing food safety by several organizations, including the U.S. Department of Health and Human Services, the U.S. Public Health Service, the U.S. Army, the National Association of State Departments of Agriculture, the American Medical Association, the Institute of Food Technologists, the U.N. Food and Agricultural Organization, the World Health Organization, and the Codex Alimentarius Commission.
  Recognition of irradiation as a food process is growing following the new approval for meats, and the support required to overcome the hurdles is mounting. This is a technology with a future.

U.S. Approvals for Irradiated Foods

  Source: Adapted from the Council for Agricultural Science
and Technology Issue Paper No. 7, April 1996