Radiation Pasteurization of Food

COUNCIL FORFOR AGRICULTURALAGRICULTURAL SCIENCE SCIENCE AND AND TECHNOLOGY—1 TECHNOLOGY

NUMBER 7 APRIL 1996

AUTHORS: DONALD W. THAYER (Cochair), U.S. De- partment of Agriculture, ARS, ERRC, Philadelphia,

Pennyslvania; EDWARD S. JOSEPHSON (Cochair), UMMARY cal Association, the Ameri- S Food Science and Nutrition Research Center, Uni- Radiation pasteuriza- can Dietetic Association, the tion of foods with low doses versity of Rhode Island, West Kingston; ARI Institute of Food Technolo- of gamma rays, X-rays, and BRYNJOLFSSON, Wayland, Massachusetts; GEORGE gists, and the health authori- electrons will effectively con- ties of approximately 40 G. GIDDINGS (Deceased), International Atomic En- trol foodborne pathogens on countries. beef, pork, lamb, and fish. As ergy Agency, Vienna, Austria; R EVIEWERS: JULIUS used here radiation pasteur- M. COON, M.D., Jenkinton, Pennsylvania; SANFORD INTRODUCTION ization means the destruction Although largely pre- A. MILLER, Graduate School of Biomedical Science, of pathogenic non-spore ventable, foodborne illness University of Texas Health Science Center of San forming foodborne bacteria remains a serious problem in and parasitic organisms, such Antonio; MORRIS E. POTTER, DVM, Centers for Dis- the United States. A report by as trichina. Radiation pasteur- ease Control and Prevention, Atlanta, Georgia; the Council for Agricultural ization therefore can protect Science and Technology has TANYA ROBERTS, U.S. Department of Agriculture, the public from diseases such estimated that foodborne dis- as salmonellosis, hemorrhag- Ecomonic Research Service; WALTER URBAIN, Sun eases caused by pathogenic ic diarrhea caused by Escher- City, Arizona bacteria such as Campylo- ichia coli O157:H7, and gas- bacter, Escherichia coli troenteritis from Vibrio vulnificus. Irradiation can extend O157:H7, Listeria monocytogenes, Salmonella, and Sta- the shelf lives of fruits and vegetables, and arthropod phylococcus aureus may cause as many as 9,000 deaths pests, e.g., insects and mites, can be sterilized or killed each year and 6.5 to 33 million cases of diarrheal dis- in a more environmentally friendly manner than is pos- ease in the United States. The annual economic losses sible with ozone depleting, highly toxic fumigants. associated with foodborne disease may be as large as $5 Moreover, long-term animal feeding studies have dem- billion to $6 billion. Recent outbreaks of disease caused onstrated that radiation pasteurized or sterilized foods by the ingestion of E. coli O157:H7 in hamburger, par- are safe and nutritious for humans. The process has been ticularly in the northwestern United States where there endorsed by by the U.S. Food and Drug Administration were more than 700 cases and four deaths from a single (FDA), the U.S. Department of Agriculture (USDA), the outbreak, have alarmed the public. Unfortunately, this U.S. Army, the World Health Organization (WHO), the organism may cause 8,000 to 20,000 cases of disease Codex Alimentarius Commission, the American Medi- annually in the United States. COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—2

The most common foodborne bacterial pathogens sae, and the protozoan parasite Toxoplasma gondii. Tri- that may be found on meat and poultry are Campylo- chinella spiralis localizes in the muscles of pigs and bacter jejuni, Escherichia coli O157:H7, Listeria mono- many wild animals and when ingested by humans can cytogenes, various Salmonella spp., and Staphylococcus cause trichinosis. Fortunately, this disease is rare in the aureus. The symptoms of campylobacteriosis caused by United States. Adult tapeworms may be several feet long C. jejuni generally are a mild diarrhea beginning 1 to 7 and occasionally infections may result from attachment days after ingestion of contaminated food and may last of Cysticercus bovis to the wall of the intestine. If the from 1 to 7 days. Infections larvae emerge within the in- from E. coli O157:H7 can testine, they may penetrate cause severe abdominal THE RADIATION PASTEURIZATION the wall; when that happens cramps and pain, bloody diar- the eyes, heart, liver, lungs, PROCESS FOR MANY FOODS HAS BEEN rhea, and occasional renal and brain may become infect- failure starting 3 to 7 days APPROVED OR ENDORSED BY THE ed. Other symptoms of infec- after ingestion of the contam- tion may be abdominal pain, MAJOR AND WORLD AGENCIES inated food, lasting days to U.S. nausea, weakness, weight weeks, and possibly resulting AND ASSOCIATIONS. loss, hunger pains, and ner- in death. Listeriosis caused by vousness. In 1993, T. gondii infection with L. monocytoge- caused 2,056 cases of food- nes is an acute infection of the brain with or without ac- borne illness in the United States at an estimated cost companying persistence of the organism in the blood. of $2.7 billion. In most otherwise healthy individuals, Symptoms appear suddenly and include fever, intense its associated disease usually is mild and self limiting. headache, nausea, and vomiting. The bloodborne form It can, however, cause diseases ranging from a rash to of the disease is an acute, mild illness with influenza like hepatitis in adults. Babies may be infected before birth symptoms, which in pregnant women usually results in by cross infection from the mother. These congenital infection of the fetus and miscarriage. Most foodborne infections sometimes lead to infections of the brain with cases of listeriosis occur among individuals with sup- death occurring in 5 to 10% of the cases. In those per- pressed immune systems. In these individuals the mor- sons whose immune systems are not functioning at nor- tality rate may reach 43%; overall it is 30%. Listeria mal levels, previously benign infections of Toxoplasma monocytogenes can multiply in foods stored at refriger- gondii may progress to encephalitis and other infections ation temperatures, so risk may increase during storage, of the central nervous system. despite proper refrigeration. Salmonellosis, caused by infection with any of over 2,500 different strains of Sal- THE ISSUE monella, is characterized by a mild to severe acute gas- Radiation pasteurization when used in conjunction troenteritis starting 6 to 72 hours after ingestion of con- with proper food processing and preparation techniques, taminated food and lasting for days to weeks, and greatly decreases the probability that foodborne patho- causing fever, pain, diarrhea, nausea, and vomiting. Sta- gens associated with meat, poultry, and other foods will phylococcus aureus can produce a heat-stable toxin in reach consumers. improperly stored food that, if ingested, will produce mild to severe symptoms of nausea, cramps, vomiting, SOURCES OF IONIZING RADIATION APPROVED diarrhea, and prostration in 2 to 7 hours lasting 1 to 2 FOR FOOD IRRADIATION days. The FDA has approved the following sources of Beef, pork, and other meats sometimes are con- ionizing radiation for the treatment of foods: gamma rays taminated by parasitic organisms that may cause disease produced by the natural decay of radioactive isotopes in humans when ingested. Among these are the parasit- of cobalt-60 or cesium-137, x-rays with a maximum ic nematode Trichinella spiralis, the bovine and pork energy of five million electron volts (MeV), and elec- tapeworms Cysticercus bovis and Cysticercus cellulo- trons with a maximum energy of 10 MeV. (The elec- COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—3

tron volt [eV] is the amount of energy acquired by an ported before consumption. Most spices are dried in the electron when it is accelerated by one volt in a vacu- open air and become severely contaminated by air- and um.) X-rays are produced when high energy electrons soil-borne bacteria, fungi, and insects. Bacterial plate strike a thin metal film and are identical in their action counts of one to 100 million per gram of spice are not to gamma rays. The term ionizing means that this form unusual. Many commercial food processors therefore of radiation has sufficient energy to create positive and fumigate spices with methyl bromide to eliminate insects negative charges leading to the death of bacteria and or with ethylene oxide to eliminate bacteria and mold. other pathogens in food. Other forms of radiant energy Both methyl bromide and ethylene oxide are extremely include light, heat, microwave, and radio waves. toxic, and methyl bromide is potentially capable of depleting the atmospheric ozone layer. Ethylene oxide has SAFETY been banned in Europe because of safety and environ- While food is being irradiated it is never in con- mental concerns, and its use for the treatment of ground tact with any radioactive material, and the gamma rays, spice has been revoked in the United States. The U.S. x-rays, or electrons used to treat it cannot make it ra- Clean Air Act and the Montreal Protocol of the Vienna dioactive. Readers can relate Convention require that any this to personal experience substance listed as ozone de- from exposure to sunlight or MULTIGENERATION STUDIES WITH pleting be withdrawn from to being x-rayed. Although production and use by the ANIMALS HAVE DEMONSTRATED THAT excessive exposure to sun- year 2001. light and to x-rays can be INGESTION OF IRRADIATED FOODS IS In the United States, harmful, appropriate expo- spices, herbs, and dry vegeta- COMPLETELY SAFE AND THAT THE sure to radiation can be used ble seasonings currently are to kill rapidly growing cells NUTRITIVE VALUE REMAINS treated with ionizing radia- such as those in cancers. It is tion to eliminate both insects ESSENTIALLY UNALTERED. the rapidly growing cells of and bacteria. The FDA has insects or spoilage and patho- approved ionizing radiation genic bacteria that are killed when food is irradiated. doses not to exceed 30 kilogray (kGy) for microbial There is little effect on the food itself because its cells decontamination of dry or dehydrated herbs, spices, and are not multiplying. There are minor effects of radiation vegetable seasonings that are used in small amounts as on some very sensitive vitamins, e.g., B1 in pork. How- food ingredients for flavoring or aroma. (This is a very ever, it has been estimated that even if all of the pork in mild treatment as a radiation dose of 1 kGy [1,000 gray], the United States were to be irradiated, only 2.3% of which represents the absorption of only enough energy vitamin B1 in the diet of Americans would be lost. Also, to increase the temperature of the product by 0.43°F.) a small amount of ascorbic acid (vitamin C) in fruits is Food irradiation is replacing the use of ethylene oxide converted to another equally usable form of the vitamin. and methyl bromide and is less harmful to the spice than In fact, multigeneration studies with animals have dem- either heat or ethylene oxide, is more effective against onstrated that ingestion of irradiated foods is complete- bacteria than ethylene oxide, and does not leave chem- ly safe and that the nutritive value remains essentially ical residues on products. unaltered. FRUITS AND VEGETABLES SPICES, HERBS, AND DRY VEGETABLE Fruits and vegetables are being irradiated in the SEASONINGS United States to eliminate insects and spoilage organ- Even though herbs, spices, and vegetable season- isms and to prevent overripening and in the case of tu- ings are used in small amounts, they may introduce bac- bers and bulbs, sprouting. The use of ionizing radiation teria sufficient to cause spoilage or foodborne disease with a minimum dose of 0.3 kGy and a maximum dose organisms in food products that must be stored or trans- not exceeding 1 kGy has been approved by the FDA for COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—4

growth and maturation inhibition of fresh foods and for Some varieties of fruit are very sensitive to radiation and disinfestation of arthropod pests in food. In addition, the skin of the fruit is damaged. They therefore may be Japan and other countries that ban the use of chemical poorly suited for irradiation, whereas other varieties of sprout inhibitors, irradiate potatoes and onions to pre- the same fruit respond well. And, too, commodities tend vent sprouting. The shelf life of specialty, very perish- to be harvested over very short periods, a practice cre- able sweet varieties of onions can be extended to 3 ating huge volumes requiring rapid treatment. Very low months. Irradiation of tomatoes not only extends their doses of ionizing radiation can prevent the emergence shelf life but also allows them to be harvested when fully of adult insects and thereby meet treatment demands. ripe. Irradiated mushrooms have a 3-week shelf life Because irradiation leaves no residues, products must without browning or cap separation. Irradiation of straw- be protected from reinfestation after treatment and dur- berries extends their refrigerated shelf life to 3 weeks ing transport. without decay or shrinkage. Irradiated fruit and vegeta- Use of irradiation as a quarantine control measure bles now are available in some U.S. stores. requires approval by both state agencies and the USDA– So that insect pests such as the fruit fly are elim- Animal and Plant Health Inspection Service (APHIS). inated, fruit from Hawaii and Puerto Rico and from other If the product is to be exported, the importing country countries must be fumigated or treated by hot water dips must approve the quarantine process. Because the ap- before being imported into the continental United States. propriate radiation doses will cause sexual sterility of Even on the mainland, many fruits, grains, and vegeta- insect pests, but not necessarily kill them outright, reg- bles must be fumigated before being transported, stored, ulatory agencies are considering the type of regulations or processed. The primary fumigant used for fruit is needed to achieve quarantine security. Currently, the methyl bromide, which may be banned in 2001. Irradi- only applicable U.S. quarantine regulation is for the ir- ation can replace fumigation for some of these commod- radiation of fresh papaya fruit in Hawaii to prevent fruit ities. Most arthropod pests, e.g., fruit flies, codling fly importation to the mainland (Table 1). moths, mango and avocado seed weevils, scale insects, Several other fruits that are available in Hawaii, mealy bugs, and mites can be sterilized or killed by very but not on the mainland, have been imported and irra- low doses of radiation. Irradiation is a promising alter- diated for customer acceptance trials, with excellent native to methyl bromide as a quarantine treatment for results. The Agricultural Research Service (ARS), the codling moth on apples. APHIS, and the food industry are participating in these Just as with other disinfestation techniques, how- trials, and the federal agencies actively are considering ever, the food irradiation process must be optimized for regulations for implementation of radiation disinfesta- the particular variety of fruit and its stage of maturity. tion. This technology, which for some commodities may

Table 1. U.S. approvals (kilograys) for irradiated foods

Product Agency Date Dose (kGy) Purpose

Wheat, wheat flour FDA 1963 0.2–0.5 Insect disinfestation White potatoes FDA 1964 0.05–0.15 Sprout inhibition Spice and vegetable seasonings FDA 1983 max. 10 Microbial decontamination Pork FDA 1986 0.3–1.0 Trichina inactivation Fruits and vegetables FDA 1986 max.1.0 Insect and/or growth and maturation delay Papaya fruit USDA 1987 min. 0.150 Insect disinfestation Herbs, spice, and dry FDA 1986 max. 30 Insect disinfestation and/or vegetable seasonings microbial decontamination Dehydrated enzymes FDA 1986 max. 10 Microbial decontamination Animal and pet food FDA 1986 max. 25 Microbial decontamination Poultry FDA 1990 max. 3.0 Microbial decontamination USDA 1992 1.5–3.0 Microbial decontamination Red meat, nonfrozen FDA Pending max. 4.5 Microbial decontamination Red meat, frozen FDA Pending max. 7.0 Microbial decontamination COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—5

be the only suitable and environmentally safe replace- contamination. Radiation pasteurized products are nei- ment for methyl bromide fumigation, has the addition- ther sterile nor shelf-stable and must be properly refrig- al advantage of increasing shelf life by eliminating spoil- erated, cooked, and served. Irradiation serves as one of age organisms. the processor’s final quality control steps, assuring both the processor and the consumer of product safety. An- WHEAT AND FLOUR other important advantage of radiation pasteurization of As much as 400,000 tons per year of imported meat and poultry products is that cross contamination of wheat are irradiated with an electron beam to kill insects other products during meal preparation is prevented. Ir- at the port of Odessa, Ukraine. This process was devel- radiation is an effective addition to the overall control oped through U.S. Army/ARS research and approved for of extremely virulent pathogens, e.g., Escherichia coli use in the United States in O157:H7, in raw ground 1963 (Table 1). It has not IN THE UNITED STATES, SPICES, beef. been used in the United States It is unlikely that all because of the availability of HERBS, DRY VEGETABLE SEASONINGS, meat and poultry products fumigants and physical meth- AND FRUITS AND VEGETABLES ever will be irradiated; rath- ods for separating insects er, irradiated meat and poul- from grain. All these methods CURRENTLY ARE TREATED WITH try likely will be chosen by have advantages and disad- IONIZING RADIATION TO ELIMINATE customers who desire or re- vantages, but neither irradia- quire a greater degree of food tion nor physical methods INSECTS, BACTERIA, AND SPOILAGE safety, and by food service leave residuals to prevent re- ORGANISMS. establishments to protect chil- infestation. dren and other high risk consumers from foodborne BEEF, LAMB, PORK, AND POULTRY pathogens. The largest market for irradiated chicken cur- Relatively low doses of ionizing radiation can be rently is hospitals and nursing homes. Irradiated chick- used for radiation pasteurization treatments of meat or en has sold well, when offered, in retail markets. poultry to control parasites, fungi, and all but the most Research has demonstrated that the number of liv- resistant of foodborne pathogens and food spoilage bac- ing cells of most foodborne pathogens, including E. coli teria. To control Trichinella spiralis, both the FDA and O157:H7, can be significantly decreased, and in many the USDA, Food Safety and Inspection Service (FSIS) cases completely killed on meat or poultry, by treatment approved in 1986 the irradiation of fresh or previously with ionizing radiation (Table 2). Radiation doses re- frozen pork to a minimum dose of 0.3 kGy and a max- quired to decrease pathogen numbers by 90% in beef are imum dose not to exceed 1.0 kGy. Regulations permit- ting poultry irradiation to control foodborne pathogens were approved by the FDA in 1990 and by the FSIS in Table 2. Radiation dose (kilograys) required to reduce the 1992 (Table 1). The FDA established the maximum dose population of foodborne pathogens by 90% in beef as 3.0 kGy, and the FSIS established the minimum dose at 5°C as 1.5 kGy. The FDA is reviewing a petition to allow Pathogen Dose (kGy) radiation pasteurization of edible tissue of domesticat- ed mammalian human food sources, primarily beef, Bacillus cereus endospore 2.46 ± 0.31 Campylobacter jejuni 0.16 – 0.20 pork, sheep, and horse. Clostridium botulinum endospore 3.43 @ –30°C The potential for consumer infection by patho- Escherichia coli O157:H7 0.30 ± 0.02 gens is decreased greatly and shelf life is extended by Listeria monocytogenes 0.45 ± 0.03 Salmonella speciesa 0.70 ± 0.04 radiation pasteurization of meat and poultry. This ben- Staphylococcus aureus 0.46 ± 0.02 efit can be achieved only if the highest-quality products aSalmonella dublin, S. enteritidis, S. newport, S. senftenberg, are irradiated, preferably after packaging, to prevent re- and S. typhimurium. COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—6

listed in Table 2. The parasitic nematode Trichinella Campylobacter, 99.999+% of E. coli O157:H7 (Figure spiralis, the bovine and pork tapeworms Cysticercus 1), 99.9+% of Salmonella (Figure 1), and 99.999+% of bovis and Cysticercus cellulosae, and the protozoan Staphylococcus cells would be killed. These results were parasite Toxoplasma gondii are all inactivated by ion- calculated assuming irradiation at a temperature of 41°F. izing radiation doses below 1.5 kGy. Escherichia coli Further, for Salmonella, a rather high resistance value O157:H7, Listeria monocytogenes, Salmonellae spp., of 0.70 kGy was used for Salmonella based on the radi- Staphylococcus aureus, and other foodborne bacterial ation resistance of a mixture of five Salmonella strains. pathogens can be eliminated or decreased significantly Some strains of Salmonella are much less radiation re- in number by treatment of meat or poultry with pasteur- sistant than this mixture and when present in foods such izing ionizing radiation doses above 1.5 kGy but below as eggs, which have higher water contents than meats 10 kGy (Table 2). do, will be even more sensitive to irradiation. Submis- The approved minimum ionizing radiation dose sion of a petition to the FDA and USDA to approve low for treatment of poultry is 1.5 kGy, and the maximum dose irradiation (0.6 to 1.5 kGy) to control Salmonella dose is 3.0 kGy. The FDA currently is considering a infections in fresh whole eggs in intact shells is pend- petition from industry for approval to irradiate nonfro- ing. zen red meats with a maximum dose of 4.5 kGy and In general, the radiation sensitivities of a bacteri- frozen red meats with a maximum dose of 7.0 kGy to al pathogen in meat and in poultry are not substantially control foodborne pathogens. Let us assume that a tar- different. Addition or removal of substantial amounts of get dose of 2.5 kGy might be chosen for the irradiation water or of salt, however, may alter the radiation sensi- of beef. Such a target will be set so that the minimum tivities of pathogens in processed meat or poultry. Ac- and maximum doses received by the product meet reg- tual number and percentage of cells that will be killed ulatory requirements. If the majority of the product re- by irradiation depend on various factors such as patho- ceived 2.5 kGy, then approximately 99.9999+% of gen, growth stage, absorbed radiation dose, irradiation- time temperature, oxygen presence, and water content. Resistance of bacterial pathogens is substantially greater 99.999999 at freezing temperatures; these effects, however, have 99.99999 been determined for most pathogens and are considered E. coli O157:H7 Salmonella 99.9999 in the selection of appropriate radiation doses. Bacteri- al pathogens differ considerably in their sensitivity to 99.999 ionizing radiation, and spore-forming bacteria and food- 99.99 TREATED BY borne viruses are substantially more resistant than are 99.9 purely vegetative forms of bacteria (Table 2).

Pathogens killed (%) 99 Spore-forming bacterial pathogens of the genera IRRADIATION TO ELIMINATE Bacillus and Clostridium are more sensitive to heat af- 90 FOODBORNE PATHOGENS ter irradiation even though the actual numbers may be 0 affected only slightly by pasteurization doses of radia- 01 2 3 Radiation dose (kGy) tion. The few nonspore-forming bacteria that may survive irradiation are injured severely and become much Figure 1. The percentage of Escherichia coli O157:H7 or Sal- monella contaminating meat or poultry by treat- more sensitive to heat. They are, therefore, very unlikely ment with ionizing radiation doses of 0 to 3 ki- to survive cooking. lograys (kGy) at a temperature of 41°F. The symbol at the lower right of the figure is the radura symbol FISH AND SHELLFISH that has been adopted internationally as a label for Fish and shellfish are significant sources of food- irradiated food. In addition, the U.S. Food and Drug borne pathogens. And irradiation has been demonstrat- Administration requires that the label include the words “treated with radiation” or “treated by irradi- ed to control Salmonella, Shigella, Staphylococcus au- ation” and “keep refrigerated” or “keep frozen.” reus, enteropathogenic Escherichia coli, Vibrio COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—7

cholerae, V. parahaemolyticus, V. vulnificus, and hep- foods that can be stored for extended periods of time at atitis A virus, which all have been associated with fish room temperature without spoilage. The shelf-stable and shellfish. Vibrio vulnificus may cause gastroenteri- product is excellent for use by immunocompromised tis or septicemia, which has a mortality rate exceeding patients, campers, yachters, astronauts, and military per- 50%. This pathogen is associated primarily with the in- sonnel. Apollo 17 astronauts ate radiation sterilized ham gestion of contaminated raw oysters. on the moon. Radiation-sterilized, shelf-stable beef steak Frequent oyster contamination led the FDA in and smoked turkey are being consumed by astronauts, 1985 to advise against consumption of raw or under- and with permission of the FDA, U.S. hospitals have cooked seafood by people with hepatic disorders; this used such products. Radiation sterilized meals and meal warning has affected the U.S. shellfish industry adverse- components are marketed commercially in South Afri- ly. Recent data have shown that ionizing radiation dos- ca and are used by the South African military forces. The es of only 1 kGy are adequate to eliminate Vibrio vulnifi- South African process is very similar to that developed cus in oysters. When combined with a traditional by the U.S. Army Natick Research and Development depuration, or controlled purification, treatment, radi- Center. The only sterile, shelf-stable meat and poultry ation doses of 2 kGy were demonstrated in 1991 to de- products available commercially in the United States are crease significantly the number of hepatitis A virus in canned (thermally processed) products. clams and oysters. Radiation sterilization allows preparation of meat Although irradiation’s ability to control foodborne and poultry products with flavor and texture character- pathogens in fish is well established, there is a concern istics different from those of thermally processed prod- that marine fish might be con- ucts. The techniques used to taminated with Clostridium RADIATION PASTEURIZATION WHEN prepare sterile food by irradi- botulinum type E, which can ation differ greatly from those grow at refrigeration temper- USED IN CONJUNCTION WITH PROPER used in radiation pasteuriza- atures as low as 38°F. As FOOD PROCESSING AND PREPARATION tion. In sterilization, the radi- mentioned, C. botulinum is ation dose must ensure elim- relatively resistant to radia- TECHNIQUES, GREATLY DECREASES THE ination of the most resistant tion and will not be affected PROBABILITY THAT FOODBORNE bacterial pathogen, Clostrid- significantly by pasteuriza- ium botulinum. Because this tion doses; if contaminated ir- PATHOGENS ASSOCIATED WITH MEAT, is a very large dose—approx- radiated fish are sealed in POULTRY, AND OTHER FOODS WILL imately 42 to 71 kGy depend- oxygen impermeable packaging on the product, it must be es, C. botulinum type E may REACH CONSUMERS. delivered to a vacuum pack- thrive because of decreased aged and deeply frozen prod- competition from other bacteria. The product then would uct to avoid flavor change and nutrient loss. The dose become toxic without the usual signs of spoilage. This selected is twelve times that required to kill 90% of the seems an unlikely event, however, considering the rar- endospores of C. botulinum. If the product is intended ity of C. botulinum type E and the availability of oxy- to be shelf stable then it must be cooked, that is blanched, gen-permeable packaging materials. before irradiation to inactivate the meat’s natural enzymes. If this is not done, the product will spoil through STERILE PRODUCTS biochemical, enzymatic action. Prior cooking improves Two types of food products require sterilization the flavor of radiation sterilized meat and poultry. rather than radiation pasteurization. The first is commer- Excellent radiation sterilized, shelf-stable mixed cially sterile foods, which require irradiation while fro- vegetable and meat products are available on the South zen, must be stored frozen, and are intended for con- African retail market. Several radiation sterilized, shelf- sumption by the severely immunocompromised patient. stable foods used are well accepted by the South Afri- The second is both sterile and shelf-stable foods, or can military forces in the field. COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—8

PRODUCT ACCEPTANCE the water when materials are to be irradiated, and the An unfortunate misconception is that the Ameri- food is passed through the radiation field. A maze con- can public will not accept irradiated food. Both attitude structed of thick concrete walls, numerous safety inter- studies and market tests have demonstrated the contrary, lock systems, strict operating procedures, and proper i.e., when the consumer is training protect workers from provided accurate informa- radiation. A typical commer- RECENT MARKET STUDIES HAVE tion about products and a cial irradiation plant design is choice between irradiated and INDICATED THAT INFORMED shown in Figure 2. nonirradiated food. In fact, Electron-beam and x- CONSUMERS ARE WILLING TO PAY A recent studies have indicated ray generating systems also that informed consumers are PREMIUM FOR can be used for food irradia- willing to pay a premium for tion. Several such plants in irradiated poultry and pork. the United States are used primarily for the sterilization of TECHNOLOGY medical supplies. These systems also must provide sig- Technologies and types of equipment required to nificant amounts of shielding during operation, but re- irradiate food are identical to those used to sterilize med- quire none when turned off. Electron-beams, however, ical supplies. (See Table 3 for examples of medical items have very low penetration ability and cannot be used for and consumer goods currently sterilized by irradiation.) irradiation of thick materials. An electron-beam system Many commercial irradiation plants exist in the United is used commercially in France to irradiate minced States, and they have established an excellent safety chicken meat. Within an aseptic packaging system, low- record. Commercial plants using cobalt-60 as the source power E-beam systems may be suitable to treat such of radiation store it underwater when it is not in use. items as single patties of hamburger. This technology Cobalt pellets are encapsulated twice in stainless steel may be practical because the radiation dose can be de- tubes arranged in racks. These racks are withdrawn from livered to the product very rapidly. A new type of self-

Table 3. Examples of items currently sterilized with ionizing radiation

Medical/Pharmaceutical Products

Airways and tubes Intravenous administration sets Alcohol wipes Liquid detergents Bandages Lubrication gels Blood Operating room towels Contact lenses Petri dishes Cotton balls Prostheses (arterial, vascular, orthopedic) Dental anchors, burrs, and sponges Surgical gloves Drug products Surgical drapes and gowns Drug mixing/dispensing systems Sutures Enzymes Syringes and needles Eye droppers and ointments Thermometers/covers Fetal probes Tongue depressors Instruments Topical ointments

Consumer Products

Adhesive bandages Disposable nurser bottles Animal vaccines Food packaging Baby bottle nipples Pacifiers and teething rings Contact lens cleaning solutions Pet food Cosmetics Rawhide dog toys Dairy and juice containers Tampons COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—9

contained irradiator designed to use cesium-137 and suit- Nations Food and Agricultural Organization, the WHO, able for use by small and medium-sized food process- and the Codex Alimentarius Commission support the use ing plants is being developed. The term self-contained of the technology for preservation of wholesomeness of indicates that the radiation source is never exposed. In food. addition, both commercial and research organizations are actively developing electron-beam and x-ray gen- REFERENCES eration equipment that may be suitable for food process- Ama, A. A., M. K. Hamdy, and R. T. Toledo. 1994. Effects of heating, ing plants. Design and operation of food irradiators are pH and thermoradiation on inactivation of Vibrio vulnificus. Food Microbiol. 11:215–227. regulated strictly by state and federal agencies. American Dietetic Association. 1996. Position of the American Die- tetic Association: Food irradiation. J. Am. Dietetic Assoc. ENDORSEMENTS 96(1):69–72. Bruhn, C. M. 1995. Consumer attitudes and market response to irradi- The FDA has approved the irradiation of pork, ated food. J. Food Prot. 58:175–181. poultry, fruits, vegetables, spices, dry vegetable season- Clavero, M. R. S., J. D. Monk, L. R. Beuchat, M. P. Doyle, and R. E. ings, wheat, and wheat flour for general use, and shelf- Brakett. 1994. Inactivation of Escherichia coli O157:H7, salmo- stable steak and smoked turkey for use by astronauts. nellae, and Campylobacter jejuni in raw ground beef by gamma irradiation. Appl. Environ. Microbiol. 60:2069–2075. The USDA has approved regulations for irradiation of Council for Agricultural Science and Technology. 1986. Ionizing En- pork, poultry, and papaya fruit. The U.S. Department of ergy in Food Processing and Pest Control: I. Wholesomeness of Health and Human Services, the U.S. Public Health Food Treated with Ionizing Energy. Report No. 109. Council for Service, the U.S. Army, the National Association of Agricultural Science and Technology, Ames, Iowa. 50 pp. Council for Agricultural Science and Technology. 1989. Ionizing En- State Departments of Agriculture, the American Medi- ergy in Food Processing and Pest Control: II. Applications. Re- cal Association, the American Dietetic Association, and port No. 115. Council for Agricultural Science and Technology. the Institute of Food Technologists have endorsed irra- Ames, Iowa. 98 pp. Council for Agricultural Science and Technology. 1995. Foodborne diation technology to enhance food safety. The United

Radiation shield

Conveyor system Unloading processed product

Irradiation room Control console Storage Loading pool Radiation source

Figure 2. A typical cobalt-60 commercial irradiation facility. Several other designs are used commercially. Illustration courtesy of Nordion International, Inc., Kanata, Ontario, Canada. COUNCIL FOR AGRICULTURAL SCIENCE AND TECHNOLOGY—10

AMERICAN ACADEMY OF VETERINARY AND COMPARATIVE TOXICOLOGY ■

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