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Can we just replace pasteurization with simple irradiation for most (if not all) foods? (For example, such as milk, to sterilize and preserve flavors)
Both pasteurisation and irradiation work by killing micro- (and macro-) organisms in food. The two processes are broadly similar and in both cases the objective is to reduce the number of bacteria or other microorganisms in the food rather than completely sterilise it. Due to this and other similarities food irradiation is sometimes called cold pasteurisation (for example in this paper).
Food sterilisation has some advantages over pasteurisation: for instance, it can be used on (most) solid foodstuffs, including fruits, vegetables, grain foods, spices and meats (such as chicken), while pasteurisation can only be used on liquids. However, irradiation cannot be used on dairy products or eggs as it results in changes in flavour and texture (source).
There are other reasons why irradiation is not used as widely as it might be. One is that some markets were already saturated with pasteurisation, which is an older technology. Another is that public acceptance of irradiation is lower, with (for example) concerns about safety of the products, although these are not rational concerns and Crawford and Ruff note that similar concerns affected acceptance of pasteurisation when it was introduced. This may also partially explain why irradiation is sometimes called cold pasteurisation, although by international agreement irradiated unprocessed food sold in stores (not in restaurants, or processed foods) is labelled with the Radura symbol anyway.
I also have a suspicion that the startup costs associated with food irradiation plants are relatively high, but couldn't find a reference for this yet.
Some further reading
Lester M.Crawford, Eric H.Ruff (1996) "A review of the safety of cold pasteurization through irradiation" Food Control Volume 7, Issue 2, April 1996, Pages 87-97
"Advantages and disadvantages of the use of irradiation for food preservation" Journal of Agricultural and Environmental Ethics March 1991, Volume 4, Issue 1, pp 14-30
"Food irradiation", Better Health programme, Victoria State Government website (accessed 2017-10-24)
Difference Between Pasteurization and Sterilization
The main difference between Pasteurization and Sterilization is that Pasteurization is the method of cooking food, particularly liquids, to heat at a particular temperature to stop the growth of microbes in the food, whereas sterilization is the method of killing all the microbes and bacteria from any item.
Pasteurization vs. Sterilization
In pasteurization, the shelf-life is shorter related to sterilized products, while in sterilization, the shelf life extended than pasteurization products. Pasteurization first established by Louis Pasteur, a French scientist in the nineteenth century. In contrast, sterilization was first developed by Nicolas Appert, who discovered that canned foods greatly help to eliminate foodborne diseases.
Pasteurization only helps to remove microbes from the food, so pasteurized should be kept in cool conditions, or if the food is out to the microbes required growth medium, then pasteurized food may get contaminated. On the other hand, sterilization removes all the types of microbes and their spores that may contaminate food. Pasteurization can fulfill with heat such as milk can be decontaminated into three different levels that are low-temp long time (LTLT), high-temp short time (HTST), and ultra-high temp (UHT). On the contrary, sterilization can fulfill many combinations of irradiation, chemicals, heat, high pressure, and filtration.
Pasteurization greatly used in food products and industries on the flip side, sterilization greatly used in medical surgeries, packaging industry, food industry, microbiology, etc. The widely used method for sterilization is autoclave in which time-temp combines with 121degree centigrade at 100 kph for almost 3 to 15 minutes for sterilization.
|Pasteurization is the method of killing all the pathogenic bacteria in food, mainly liquid.||Sterilization could consider as any method that eliminates all microbial life and its forms that are present in a volume of fluid, food, some packaging material, or in medical instruments.|
|Shelf-life is shorter related to sterilized products.||Shelf life is extended to pasteurization products.|
|First established by Louis Pasteur, a French scientist in the nineteenth century.||It was first developed by Nicolas Appert, who discovered that canned foods greatly help to eliminate foodborne diseases.|
|Destruction of Microorganisms|
|It only helps to remove microbes from the food, so pasteurized should be kept in cool conditions, or if the food is out to the microbes required growth medium, then pasteurized food may get contaminated.||Removes all the types of microbes and their spores that may contaminate food.|
|Forms of Pasteurization/Sterilization and Classification Based on Heat Treatment|
|It can be fulfilled with heat such as milk can be decontaminated into three different levels that are a low-temp long time (LTLT), high-temp short time (HTST), and ultra-high temp (UHT).||It can be fulfilled with many combinations of irradiation, chemicals, heat, high pressure, and filtration.|
|Greatly used in food products and industries.||They are greatly used in medical surgeries, packaging industry, food industry, microbiology, etc.|
What is Pasteurization?
Pasteurization is the method of killing all the pathogenic bacteria in food, mainly liquid, by the process of heating at a particular temperature for some time. For instance, the main example of pasteurized food is pasteurized milk, which is heated and boiled at high temperatures to remove all the harmful microbes present in the raw milk. This pasteurized milk is then packed into sterilized containers in many disease-free conditions like glass-bottled milk and tetra packaged milk.
Pasteurization was first established by Louis Pasteur, a French scientist in the nineteenth century. Pasteurized food is safe for human ingesting and to recover its shelf-life. In pasteurization, the shelf-life is shorter related to sterilized products.
Pasteurization is the main method to form long-life milk and juice, but pasteurized should be kept in cool conditions, or if the food is out to the microbes required growth medium, then pasteurized food may get contaminated. Three different levels of pasteurization are Low-Temp Long Time (LTLT), High-Temp Short Time (HTST), Ultra-High Temp (UHT).
What is Sterilization?
Sterilization is the process that could be considered as any method that eliminates all microbial life, it’s all spores, and its forms that are present in a volume of fluid, food, some packaging material, in medical instruments, and biological culture medium. Sterilization can be fulfilled with many combinations of irradiation, chemicals, heat, high pressure, and filtration.
Sterilization could be changed from sanitization, disinfection, and pasteurization. The widely used method for sterilization is autoclave in which time-temp combines with 121degree centigrade at 100 kph for almost 3 to 15 minutes for sterilization. Sterilization is greatly used in medical surgeries, packaging industry, food industry, microbiology, etc.
- Pasteurization is the heating of food, especially liquids, to cook at specific temperatures to control the development of germs in the food, whereas sterilization is known as the homicide of all the microorganisms and bacteria from any food product.
- The shelf-life is smaller in pasteurization in comparison to sanitized items, while the shelf life is prolonged in sterilization as compare to sanitization items.
- Louis Pasteur (a French scientist in the nineteenth century) was the first person who established the process of pasteurization, whereas Nicolas Appert first developed the process of sterilization.
- Pasteurized products should be saved in cool situations because pasteurization only assists in eliminating microorganisms from the food products on the other hand, sterilization removes all microbial reproductive structures that may infect food and also remove all the types of microbes.
- Pasteurization can be disinfected into three diverse stages that are ‘a low-temp long time (LTLT), high-temp short time (HTST), and ultra-high temp (UHT) on the contrary, sterilization can be achieved with various mixtures of irradiation, chemicals, heat, high pressure, and filtration.
- Pasteurization is mainly used in food items and industries on the flip side, sterilization is mainly used in medical surgeries, packaging industry, food industry, microbiology, etc.
The above discussion concludes that pasteurization is the method to stop the growth of microbes in the food by heating, whereas sterilization is the method of killing all the microbes and bacteria from any item.
Aimie Carlson is an English language enthusiast who loves writing and has a master degree in English literature. Follow her on Twitter at @AimieCarlson
What is Sterilization
Sterilization can be defined as any process that eliminates or destroy all forms of microorganisms and other biological agents (such as spores) present in a specified region, such as a food item, surface, a volume of fluid, packaging material, medication, instruments or in a biological culture media. Sterilization can be accomplished with one or combination of these food technologies such as heat, chemicals, irradiation, high pressure, and filtration. Sterilization is different from disinfection, sanitization, and pasteurization process in that sterilization eradicates, disables, or removes all forms of life and other biological agents.
Bill Defines Irradiated Meat as 'Pasteurized'
If a last-minute provision in the Senate farm bill becomes law, irradiated hamburger could become known by a more appealing name: pasteurized beef.
Senator Tom Harkin, the Iowa Democrat who heads the Senate Agriculture Committee, said today that he had inserted the provision in an effort to ''more clearly define pasteurization,'' the process by which disease-producing bacteria have long been destroyed in some foods through heating.
The Harkin change would define irradiation as a kind of pasteurization. It has been sought for several years by the growing irradiated-food industry, which argues that irradiation is a 'ɼold pasteurization'' and deserves to be referred to as such.
But neither the Food and Drug Administration nor the Agriculture Department has yet to agree that meat treated by radiation, a process approved by the government two years ago, should qualify as pasteurized. Food safety advocates argue that the legislative provision is an effort to avoid F.D.A. regulatory procedures that would ordinarily be needed in order to define irradiation as a form of pasteurization for labeling purposes. Both the industry and Mr. Harkin deny any such end run.
Mr. Harkin's home state is also home, in Sioux City, to the main plant of the SureBeam Corporation, the No. 1 irradiator of ground beef sold in the United States. He inserted the provision almost three weeks ago, on the last day of Senate debate on the farm bill. The provision was later discovered by the public-interest lobby Public Citizen.
In another late change, Mr. Harkin also inserted a clause that would forbid the agriculture secretary to keep irradiated food out of the school lunch program or any other federal nutrition program.
Only the Senate version of the bill includes those provisions. The legislation is now in a House-Senate conference, and it is uncertain whether the clauses will survive.
The two sides in the food safety debate agree that when consumers see ''irradiation'' on a label, they often view it as a warning that the product has undergone a potentially dangerous process.
Irradiation is something the consumer associates with ''wartime and bombs and bad things,'' said Diane Toops, food and trend editor of Food Processing, a trade magazine that views irradiation favorably. And since Sept. 11, the process has become associated with anthrax as well, because irradiation is now used to kill germs in the postal system.
While Mr. Harkin played down the effect of his last-minute changes, consumer advocates said the provision on irradiation's definition could allow irradiated food to be labeled ''pasteurized'' without F.D.A. action. Under current regulations, the label on irradiated meat must instead state that it has been ''treated by irradiation'' and must be marked with the symbol for irradiation, called a radura.
''It would be terrible, just horrible, misleading the public about what industry is doing to its food,'' said Joan Claybrook, president of Public Citizen.
Wil Williams, spokesman for the SureBeam Corporation, said that Senator Harkin was simply 'ɼoming up with one standard definition'' and that SureBeam had no intention of skirting the regulatory process.
''Irradiation is pasteurization -- partial sterilization to eliminate pathogens,'' Mr. Williams said. 'ɺll the farm bill does is come up with a standard everyone can use.''
Since irradiation was approved by the government two years ago, he said, it has been used to remove germs from millions of pounds of beef.
A spokesman for Agriculture Secretary Ann M. Veneman had no comment on the Harkin provisions.
Some Pros and Cons of Food Irradiation
Is irradiation safe? Proponents insist it is opponents argue it is not. Here is a summary of the positions of proponents and opponents on safety and other issues related to irradiation.
Unique Radiolytic Products
Irradiated foods contain certain compounds that are formed when the food is subjected to high-energy ionizing radiation, such as gamma rays or X-rays. The FDA has estimated that the concentration of radiolytic products formed in food treated at a dose of 1 kilogray is on the order of 3 parts per million.
Any food undergoes changes when it is treated, whether that treatment involves boiling, baking, or irradiating. Ac cording to information prepared by the Atomic Industrial Forum (a group that favors nuclear energy), one study of radiolytic prod ucts in highly irradiated meat “concluded that there are actually no such things as unique radiolytic products (or URPs).” 1
The American Dietetic Association posi tion paper on irradiated foods states: [F]ree radicals and other compounds produced dur ing irradiation are identical to those formed during cooking, steaming, roasting, pasteurization, freezing, and other forms of food preparation… All reliable scientific evidence, based on animal feeding tests and consump tion by human volunteers, indicates that these products pose no unique risk to human beings.” 2
One study in India concluded that there was greatly increased incidence of polyploidy, or chromosomal damage, in a group of children fed irradiated wheat as compared to a control group. Supporters of irradiation, however, challenge this study’s results as non-reproducible.
Such scientific studies that have been done to date do not support the safety of food irradiation, critics say. In fact, the FDA’s own statement on irradiation acknowledges that “current state-of-the-art toxicity tests are not sensitive enough to detect the potential toxicity of URPs at low levels.” 3 Of the 441 studies that had been done on the subject at the time of the FDA’s review, all but five were judged by the review team to be “inadequate to evaluate the safety of irradiated food.” 4 Of those five, the New Jersey School of Medicine Department of Preventive Medicine and Community Health determined two “to be methodologically flawed, either by poor statistical analysis or because negative data were disregarded. One of the two also suggested that irradiated food could have adverse effects on older animals. In a third FDA-cited study, animals fed a diet of irradiated food experi enced weight loss and miscarriage.” 5
Richard Piccioni, Ph.D., senior staff scien tist at Accord Research and Educational As sociates, Inc., has noted: “Without toxico logical testing at exaggerated doses, the carcinogenic risk to large human populations ingesting any additive or residue is impossible to assess.” Contrary to proponents’ claims that URPs, if they exist, are safe, Piccioni writes: “the available scientific literature pro vides evidence to make a strong presumption of carcinogenicity in some if not all irradiated foods.” 6
Public Citizen’s Health Research Group noted that the FDA’s review of scientific literature did not include one carried out under auspices of the USDA: “This study, which was actually 12 different studies, examined the effect of feeding irradiated chicken to several animal species. One of these 12 studies found that fruit flies fed irradiated chicken had a statistically significant dose-related increase in the rate of death of their offspring compared with flies who were not fed irradiated chicken.”
Another study cited by Public Citizen found that “mice fed irradiated chicken had a greater incidence of kidney disease than mice fed unirradiated chicken.” 7 Other published studies cited by Public Citizen found kidney damage and testicular damage in rats fed irradiated chicken.
Irradiation has been shown to reduce the vitamin content of food.
The International Consultative Group on Food Irradiation says, “Just as vitamins vary in their sensitivity to heat, so do they vary in their sensitivity to radiation…. Vitamins A, F, C, K, and B-1 (thiamine) in foods are relatively sensitive to radiation, while some other B vitamins such as riboflavin, niacin, and vitamin D are much more stable.” 8
The American Dietetic Association says, “The relative sensitivity of different vitamins to irradiation depends on the food source, and the combination of irradiation and cook ing is not considered to produce losses of notable concern.” In any case, steps can be taken to minimize nutritional losses in the irradiation process, including “irradiating food in an oxygen-free environment or in a frozen state.” 9 (Neither of these proffered mitigating techniques has been put into rou tine practice at any irradiation facility in the world.)
Still, there are some who insist irradiation has no impact or, indeed, may have a positive one on the nutritional content of food. The most extreme statement of this view is made by the Atomic Industrial Forum: “In virtually all cases, food preserved with radiation is nutritionally equal or superior to those preserved by other comparable means. Proteins and essen tial amino acids are not destroyed and, in some cases, more vitamins are retained.” 10
“Irradiation … reduces levels of essential nutrients in food, especially vitamins A, C, F, and the B complex. Cooking irradi ated food reduces these levels still further. The industry reluctantly admits this but suggests that the problem could be taken care of by vitamin supplements!” write Michael Colby, director of Food & Water, Inc., a non-profit organization established to protect food safety, and Samuel S. Epstein, a professor of occupational and environmental medicine at the University of Illinois Medical Center Chicago.” 12
The extent of nutritional loss varies with the type of food and the radiation dose, writes Susan Meeker-Lowry. “Generally, the more complex the food, the less it suffers. Still, a 20 percent to 80 percent loss is not uncommon.”
Treatment by irradiation does not visibly harm the fruit, as, say, treat ment by hot-water does.
Fruits that have been irradiated look better and have a longer shelf life than untreated fruits or fruits that are treated by other means. Irradiation “will extend shelf life for most foods at competitive costs.” 13 An article in Food Technology claims irradiation “extends shelf life of the fruit by delaying maturation… and inhibiting mold growth on the fruit.” 14
Claims of increased shelf life are not proven for Hawaiian produce. Lyle Wong of the state Department of Agriculture, one of irradiation’s chief proponents, has said: “I’m not sure if irradiation as a commodity treatment will give rise to a better product.” 15 Irradiation can cause fruit to become scalded and unsuitable for marketing. Indeed, the state Department of Agriculture has paid to cover the $700 cost of irradiating a shipment in 1995 where the fruit was of such poor quality that the wholesaler would not accept it.” 16
The chief – and, so far, only- reason cited for supporting construction of an irradiation facility in Hawai’i is to increase the volume of fruit exported to the mainland United States.
Exports having a potential value of as much as $300 million a year are being lost to Hawai’i because of the U.S. Department of Agriculture’s fruit-fly quarantine on shipments of Hawai’i produce to the U.S. main land. With the USDA ready to approve a generic irradiation dose for all fruits that are host to fruit flies, the way is clear to tapping this market.
In addition, test marketing of Hawaiian fruit irradiated in Chicago has been hugely successful, showing widespread consumer acceptance of irradiated fruit.
Even the state Department of Agriculture has acknowledged that the “$300 million figure for exports is subject to debate.” 17 No economic analysis has been pro duced to support this or any other figure.
In any event, irradiation is not the only way to exploit markets abroad. The same kind of heat treatment that makes exports of papaya acceptable in mainland markets will soon be available to lychee. Growers of carambola can have access mainland markets through use of a cold treatment approved by the USDA. Canadian markets are another potential outlet for untreated or unirradiated fruit, since Canada has no quarantine against fruit flies similar to that which exists on the mainland.
State officials have themselves expressed concern that widespread irradiation of Hawaiian fruit might allow growers in tropical countries to avail themselves of the same technology, thus eliminating any edge that irradiation might provide to Hawaiian fruit (especially considering the additional ship ment costs of sending fruit from Hawai’i as opposed to Mexico or the Caribbean). “The establishment of post-harvest treatment protocols and irradiation will allow the shipment of Hawai’i fruits and vegetables, but other countries will eventually ask to have those treatment protocols allowed for their fruits and vegetables.”
Finally, it is not clear that there will be strong markets for irradiated produce. Food & Water, a mainland organization, has organized customer protests to stores carrying irradiated fruit, resulting in at least one supermarket chain refusing to stock irradiated Hawaiian produce anymore.
The drawbacks of an irradiation facility may be outweighed by the benefits.
The economic boon that irradiation will provide in Hawai’i more that overcomes any perceived drawbacks. One University of Hawai’i professor of Food Science and Human Nutrition has written, “The issue here, of course, is risk versus benefit. The risks are related to the dangers to the environ ment and the workers … as well as to the dangers of the irradiated foods to the con sumers. The benefits are the economic gains to Hawai’i’s agriculture from the national marketing of Hawai’i-grown exotic fruits…
“There are always risks when handling, storing, or using radioactive materials. How ever, there can also be great risks in handling dynamite, gasoline, or even fire. Yet how many of us daily drive in cars (potential bombs), cook over gas flames or campfires, or light cigarettes with matches (all potential torches)?” 19
With no analysis of economic benefits having been made public and defended, any discussion of the economic boon of an irradiator is premature, to say the least.
Moreover, in the discussion of risks versus benefits, it is important to bear in mind that people who may not benefit at all will bear at least part of the risk imposed by an irradiation facility. The few employees who may work at an irradiation facility may be willing to tolerate the radiation exposure in return for a wage, but in so doing, they will incrementally increase their own risks of cancer. 20 In addition, they will increase the risk that their offspring will be born with genetic damage. These eventualities entail public costs. No matter how safe the developers of any irradiation facility claim it to be, there is no question but that its very presence does impose an incremental risk to the public at large.
Here is what John Gofman, M.D., Ph.D., has to say on the subject. (Gofman is profes sor emeritus of medical physics at the University of California, Berkeley, and one of the leading experts on the health effects of radiation). “First, it is scientifically reasonable that the dose-effect relationship between radia tion and cancer is linear, and that there is no threshold dose… Second, it is a violation of the most fundamental human rights to impose risks (deaths) upon individuals without their consent. Human rights should not be sacrificed to the pursuit of a healthy economy, affluence, progress, science or any other goal. The whole ‘benefits versus risk’ doctrine is a profound violation of human rights.” 21
Finally, there is the matter of risk avoidance altogether. “No risk is acceptable if it is avoidable…. However, when people are merely doing a risk assessment, this principle cannot come into play.” 22 In the case of a fruit irradia tion facility, any “cost-benefit” or “risk-benefit” assessment must include a discussion of ways to avoid the risk altogether, including alternative treatment methods and the prospect of developing a value-added processed food industry (which has the benefit of increasing the number of jobs).
Both the state government and the government of Hawai’i County are proposing to spend public money on construction of a fruit irradiation facility.
The spending of public money on a project that will directly benefit private growers, and only indirectly benefit the public, is just part of government’s role. The government has a responsibility to see that the economy prospers.
If irradiation is a proven technology (as proponents claim) and the market for irradiated fruit is solid (as proponents claim), there should be no impediment to the private sector raising the capital needed for an irradiation facility, either by putting up the money themselves, by attracting equity investors, or by borrowing the funds. Indeed, this is what capitalism is all about.
In any event, the fruit industry has already received substantial government assistance. The state and federal governments have spent millions of dollars on research into pest control, disease, and other types of quarantine treatments for Hawai’i products. At some point, the subsidies should end.
Irradiating food requires the use of a high-powered source for the ionizing radiation, which is usually Cobalt-60.
The technology that has been developed for using cobalt-60 as a source for gamma radiation is well established and safe. The American Dietetic Association, for example, states: “Strict regulations govern the transportation and handling of radioactive material. Irradiation facilities are constructed to withstand earthquakes and other natural disasters without endangering the community or workers. Radioactive material is transported in canisters tested to withstand colli sions, fires, and pressure. Worker safety is protected by a multifaceted protection sys tem within the plant.”
The history of accidents at irradiation facilities belies claims of their safety. Among the examples of contamination from irradiators is one right here in Hawai’i. In 1967, at a demonstration irradiator at Fort Armstrong, O’ahu, a shipment of cobalt-60 “pencils” corroded through their container, resulting in the leak of radiation from the shipping cask into the water storage pool.
Other examples of unsafe practices at irradiators include incidents at the Isomedix facility in New Jersey, which was determined by the Nuclear Regulatory Commission to have flushed radioactively contaminated water into city sewers in 1974. Another New Jersey irradiator, Radiation Technology, Inc., lost its NRC license in 1986 for repeated worker safety violations. “RTI was cited 32 times for various violations, including throwing radioactive garbage out with the regular trash. The most serious violation was bypassing a safety device to prevent people from entering the irradiation chamber during op eration, resulting in a worker receiving a near lethal dose of radiation.” All these accidents occurred at irradiation facilities using Cobalt 60.
The state of Hawai’i has signed an agreement that gives it right of first refusal to purchase the seventh unit to be built of a new cesium-137-sourced irradiator.
There are many advantages to using cesium-137 as a source of ionizing radiation. Cesium-137 is abundant as a byproduct of the nuclear weapons manufacturing industry. In contrast to cobalt-60’s half life of about five years, cesium-137 has a half life of more than 30 years, meaning the radioactive source does not need to be replenished as often as a cobalt-60 source. While the storage of cesium salt capsules in cooling pools of water can pose environmental problems, the cesium irradiator considered by the state will not keep cesium in water at all.
Cesium-137 is one of the most dangerous radioactive by-products of nuclear weapons production. Because cesium chloride is water-soluble, when it enters the body, it is distributed to all the cells of the body, creating what is called a whole-body dose. 23
As to claims that no radiation can escape thick containment structures, the history of nuclear materials is rife with examples that it regularly does just that. A 1988 accident at Radiation Sterilizers, Inc., in Decatur, Geor gia, brought a halt to the use of Cesium-137 in irradiation facilities. That occurred when “supposedly ‘fail-proof’ cesium-137 capsules leaked into the water storage pool. Officials found ‘extensive’ radiation contamination throughout the facility. In addition, inspec tions of plant workers’ homes and cars found that radioactivity had been transported outside the facility.” Clean-up costs exceeded $47 million. 24
Constant bombardment by high-radiation energy, such as would occur in a cesium-137 irradiator, eventually causes the strength of surrounding metal to diminish and the metal to become embrittled. This has occurred in many nuclear reactors vessels and in casks storing high-level nuclear waste (and cesium-137 is classified as a high-level nuclear waste). 25
Cesium-137 is stored in capsules that are 21 inches long, 2.6 inches in diameter, and which weigh 20 pounds apiece. A 16-ton stainless steel cask carried on a custom-made trailer bed was needed to transport just 16 cesium capsules when the Department of Energy recalled cesium capsules from a Colorado irradiator in 1994. 26
One of the unresolved issues in any discussion of industry based on nuclear sources is waste. There is no permanent re pository for high level waste in the United States.
Cobalt-60 is not radioactive waste, they say, nor does it generate any. It is deliberately manufactured (by a Canadian firm, Nordion) for use in gamma irradiators, including those used in hospitals as well as private industry. “Radioactive waste does not accumulate at irradiation facilities because no radioactivity is produced…. At gamma irra diators, radionuclide sources, typically co balt-60 or more rarely cesium-137, are used as the sources of radiation energy. These ele ments decay over time to non-radioactive nickel and non-radioactive barium, respectively. The sources are removed from the irradiator when the radioactivity falls to a low level, usually between 6 percent and 12 per cent of the initial level (this takes 16 to 21 years for cobalt-60). The elements are then re turned in a shipping container to the supplier who has the option of reactivating them in a nuclear reactor or storing them. Canada has calculated that all the cobalt-60 it supplied for use in 1988 (about 100 million curies) would require a storage space of about 1.25 cubic meters, roughly equivalent to the space occupied by a small desk.” 27
The use of cesium-137 won’t create radioactive waste. It will actually reduce it, since cesium-137, which is now considered a waste, would be converted into a useful commodity. Here is what one investor in the Gray-Star company, which is proposing to build ce sium-137 irradiators, says: “They [Gray-Star] are proposing to ‘privatize’ all of the cesium at Hanford and Savannah River [two of the U.S. Department of Energy nuclear facilities] as a start. One of several scenarios is that the government (DOE) pay them, or their associ ated manufacturer, an appropriate sum of money to take title to the cesium, and remove it from government sites. In effect, this would remove the material from the government’s ‘ledger’ and eventually eliminate the cost and risk of maintaining the isotopes…. Ultimately, the title will be transferred to licensed users within the food industry much in the same way that cobalt-60 is now transferred in normal commerce.” 28
Since the production of cobalt -60 does require the use of nuclear reactors, one cannot truthfully say that its production does not generate radioactive waste. All reactors generate high level nuclear waste, for which no safe, long term solution has been found. Cobalt-60 fabrication plants are, in fact, even worse than normal nuclear reactors, being legally permitted to release 20 times more radiation than a commercial reactor. 29
In any case, irradiation facilities using co balt-60 do produce radioactive waste. The cooling water in which the cobalt-60 is stored becomes radioactive, as do the containment vessels. These must be handled as radioactive wastes.
As to the statement, that all the cobalt-60 produced in a year could fit in a volume the size of a desk, in theory it might be true in practice, it isn’t. The total volume required for safe storage of a volume of cobalt-60 the size of a desk is, in reality, many thousands of times that. 30
Both cobalt-60 and cesium-137 are highly radioactive for many years. Even when the radioactivity of cobalt-60 has decayed to the point it can no longer generate the high doses of gamma rays needed to irradiate fruit to the USDA-required levels, it still emits radiation at levels too high for humans to be exposed to safely – and will continue to do so for decades.
Cesium-137, with a half-life of 30 years, takes hundreds of years to decay to background levels of radiation. In addition, not only does the use of cesium-137 generate radioactive waste, it is radioactive waste to start with, being produced only as a result of nuclear fission, such as occurs in an atomic explosion or a nuclear reactor.
Proposals such as that of Gray-Star to turn this waste into a private commodity support the arguments of critics who have long main tained that irradiation is part of a plan by the government to reduce its radioactive-waste management costs. DOE’s reason for pro moting nuclear byproducts was made clear at hearings held in 1983 before the House Armed Services Committee: … “the utilization of these radioactive materials simply reduces our waste-handling problem… We get some of these very hot elements like cesium and strontium out of the waste.” The DOE was particularly keen on developing technology to reproduce spent nuclear reactor fuel in order to recover the cesium-137 (and plutonium, although this wasn’t loudly discussed) and it actively promoted the development of food irradiation using cesium-137 for years. According to the DOE in 1983, “The strategy being pursued … is designed to transfer feder ally developed cesium-137 irradiation tech nology to the commercial sector as rapidly and successfully as possible.” 31
The accident in Decatur, Georgia, led the DOE to recall all the cesium-137 capsules it had “leased” out and for the irradiation in dustry as a whole to go with cobalt-60 instead of cesium-137. Now that nearly a decade has passed, the DOE – and industry – seem to be attempting to resurrect the idea of cesium 137 as a source for gamma irradiators.
X-rays can be generated by linear accelerators or other machine source.
The use of a linear accelerator or other X-ray generator avoids the problems associated with use of a radioactive isotope.
To generate X-rays at sufficient strength to meet USDA quarantine requirements, any linear accelerator or other genera tor would almost certainly place a substantial burden on the Big Island’s power supply. This, in turn, might require development of additional energy resources, possibly including geothermal. 32 Linear accelerators are rarely used in irradiation facilities, in any event. Without a more detailed proposal for use of an accelerator for treatment of Hawaiian fruit, a pro- and con- discussion is not meaningful.
Gamma rays and X-rays are used to diagnose and treat health problems. They come from the same types of sources that would be used in a food irradiator.
Since X-rays are used on people, what’s the problem with using X-rays on fruit? This was a point that irradiation’s proponents made often during a town-hall type meeting on irradiation held in Hilo on January 16.
The strength of a radioactive source or electron beam used in an irradiation facility is many millions times greater than that used in medical equipment. The dose that a papaya receives (about 300 Grays, or 30,000 cads, in the process used at Isomedix in Chicago) is one million times the dose that a person would typically receive in a chest X- ray.
For purposes of comparison, the LD 50 dose for humans – that is, the dose sufficient to kill half of an exposed population- is 600 rads. In other words, the radiation that just one papaya must receive is many times that which can kill a person.
Jane Says: There's No Fallout From Irradiation
Irradiation involves subjecting certain foods (primarily spices, some fruits, and a limited amount of meats) to intense doses of ionizing radiation in the form of gamma rays, X-rays, or electron beams before sending them to market. Considered a food-safety intervention since 1963, when it was approved to control insects in wheat and flour, irradiation kills or deactivates harmful bacteria, including E. coli O157:H7, Salmonella, Campylobacter, Listeria, Clostridium, and Vibrio, thus reducing the threat of food-borne illnesses. According to the Centers for Disease Control and Prevention, these bugs cause approximately 3,000 deaths and 128,000 hospitalizations of Americans each year. Heat obviously does the same sort of thing, which is why milk, for instance, is pasteurized. But many pathogens are more difficult to kill than the ones pasteurization was designed for, and higher temperatures would affect flavor and texture adversely.
Irradiated foods must be stored, handled, and cooked in the same way as nonirradiated foods, but they have a longer shelf life because the process destroys molds and bacteria that cause spoilage and also slows down ripening or sprouting in plants. The Food and Agriculture Organization of the United Nations has estimated that about 25 percent of all worldwide food production is lost after harvesting to insects, bacteria, and spoilage.
The irradiation of food has been approved in 37 countries for more than 40 products. The largest marketers of irradiated food are Belgium, France, and the Netherlands, but overall, irradiated foods make up a small portion of the food supply. According to Food Safety News, in the United States about one-third of imported spices formerly fumigated with chemicals are irradiated that amount could increase after the October 2013 release of the FDA’s draft risk assessment on the levels of pathogens and other unsavory contaminants found in 12 percent of spices imported to the U.S. Anyone who has traveled to India, for instance, or the Middle East, and seen the age-old ways in which spices are harvested, dried, and stored will not be surprised by this news. My gut reaction was “only 12 percent?”
Jane Says: Everything You Know About Microwaves Is Wrong
Some imported fruits are irradiated as well to kill or sterilize any “hitchhiker” live pests, such as the mango seed weevil and certain fruit fly species, that may be problematic, if not potentially devastating, for American agriculture. The USDA’s Animal and Plant Health Inspection Service has approved the use of irradiation as a quarantine treatment for mangoes from India lychees, longans, rambutans, pineapples, mangoes, and mangosteens from Thailand dragon fruit from Vietnam and guavas from Mexico. In the U.S., Hawaii, a pioneer in the technology, exports irradiated sweet potatoes, papayas and other tropical fruits, and fresh herbs such as curry leaf and basil to the mainland.
So how does irradiation affect the “sensory quality”—that’s flavor and texture to you and me—of tropical fruits? Those that have been given a post-harvest hot-vapor treatment, after all, are dispiriting, with a cooked flavor and texture, and I presumed the same would be true for irradiated specimens. “It depends entirely on the type of fruit,” explained David Karp, a renowned fruit authority who also keeps a sharp eye on the California farmers market scene. “As far as mangoes go, certain cultivars are highly susceptible, and others aren’t. In some, the flavor improves.” Karp is a strong believer in eating seasonal foods that are as fresh as possible, but he’s no absolutist. “Irradiation provides access to both growers, who wish to export, and consumers, who wish to eat those foods,” he said.
A Band-Aid Solution to an Intractable Problem?
One objection to making food irradiation more common in the United States—especially in light of USDA shutdowns like the one at a Central Valley slaughterhouse earlier this week—is the perfectly reasonable concern that the food industry will rely on irradiation as a last-ditch measure to protect consumers from illness instead of preventing contamination with stringent husbandry and sanitation protocols in the first place. While irradiation works beautifully on bacteria, it doesn’t affect viruses and prions, the infectious agents believed to cause bovine spongiform encephalopathy (aka BSE, or mad cow disease). NYU public health authority (and queen of the sound bite) Marion Nestle calls it a “late stage techno-fix.”
E. coli 0157:H7 is a case in point: Outbreaks have been caused by contaminated foods such as bean sprouts, spinach, and other leafy greens, cantaloupe, and most famously, ground beef. How does this happen? A 2011 report from the American Academy of Microbiology cuts to the chase: “It all starts with poop,” it reads. “Because E. coli lives in the gut, transmission of E. coli from one organism to another is predominantly from feces to mouth. The source of E. coli in almost all food and water contamination events can be traced back to exposure to fecal matter at some point in the food chain whether it is on the farm, at the processing plant, in transportation, during retail, at the restaurant, or even during preparation in our homes.”
Confirmation: When It Comes to Food Safety, You’re Right to Be Paranoid
Ground beef is especially worrisome: The act of grinding distributes surface bacteria throughout the product, which is why it’s important to cook it thoroughly. I think I can speak for us all when I say I don’t want to eat fecal matter in my ground beef, irradiated or not. (Still, do I forgo a great burger every so often? Not no, but hell no. That said, I grind the meat myself.)
Interest is also growing in the possible irradiation of fresh leafy greens and other produce. Although organic foods cannot be irradiated, the Organic Center, a good clearinghouse for the science behind organic food and farming, published a fascinating Critical Issue Report on irradiation for fresh produce in 2007.
Speaking of Band-Aids, among the many other uses of irradiation is the sterilization, for more than 50 years, of health care products, from those adhesive strips to ear swabs, syringes, and surgical implants.
Health Effects of Irradiation
Another concern among consumers is about the relative safety or healthfulness of irradiated food. Below are some commonly asked questions, along with answers drawn from the scientific community, including the World Health Organization, which published this detailed technical report in 1999.
Does irradiation turn food radioactive?
No. To quote Extoxnet, a collaboration among extension toxicologists from the University of California, Davis Cornell University Oregon State University University of Idaho and Michigan State University, “the food itself never contacts a radioactive substance, and the ionizing radiation used is not strong enough to disintegrate the nucleus of even one atom of a food molecule.” The folks at the University of Wisconsin Food Irradiation Education Group have a great analogy: “Just as the airport scanner doesn’t make your suitcase radioactive, this process is not capable of inducing radioactivity in any material, including food.”
Does irradiation cause chemical changes in food?
Yes. “That is how it kills bacteria,” writes nuclear chemist and science writer Robert L. Wolke in What Einstein Told His Cook. “But while the changes in the bacteria’s DNA are lethal to them, the amount of chemical change in the food itself is minuscule at the radiation intensities used. Cooking causes chemical changes too, of course.”
Does irradiation kill nutrients as well as harmful microorganisms?
Yes. The same is also true of cooking and food preservation methods such as pasteurization, which took many years to gain public acceptance, and canning. The nutrients lost will vary, depending on the food source and the vitamins in question. According to the Organic Center report, “irradiation of citrus fruits and juices has been shown to oxidize a portion of the ascorbic acid (Vitamin C) but. since the oxidized and the nonoxidized forms of the molecule are both biologically active, the nutritional impacts of this effect are likely to be minimal. Three varieties of irradiated lettuce contained higher levels of antioxidants and phenols (desirable nutrients) than controls i.e., irradiation in this case improved the nutritional quality of the food.” If you eat a balanced diet, and one that’s not limited solely to irradiated foods, then I wouldn’t worry.
When food is irradiated, doesn’t it form dangerous or carcinogenic compounds?
According to a 2011 paper published in the European Food Safety Authority Journal, “the main reported radiolytic products [new compounds] are certain hydrocarbons and 2-alkylcyclobutanones [2-ACBs] produced from the major fatty acids in food, and some cholesterol oxides and furans. Most of these substances are also formed in food that has been subjected to other processing treatments and are thus not exclusively formed by irradiation. Furthermore, the quantities in which they occur in irradiated food are not significantly higher than those being formed in heat treatments.”
The Organic Center report mentions a few radiolytic products specifically, including formaldehyde and furan, which is formed in irradiated high-carbohydrate foods, and, as it turns out, in a variety of cooked foods, including baked bread and roasted coffee: “Furan causes cancer in rodents fed high doses, and its presence in foods, even at low levels, automatically triggers regulatory concerns. Awareness that furan was produced in irradiated foods led FDA and industry scientists to test similar nonirradiated foods for furan they found that cooking also produces furan in many foods, generally at higher levels than are found in irradiated foods.”
How can you tell what foods are irradiated?
The FDA requires that both the international Radura logo and the words “treated with irradiation” or “treated by irradiation” appear on packaged foods, bulk containers of unpackaged foods, placards at the point of purchase (for fresh produce), and invoices for irradiated ingredients and products sold to food processors. Foods that contain irradiated ingredients (such as the spices in sausages or packaged foods) do not have to be labeled, and restaurants don’t have to disclose the use of irradiated ingredients.
What about radioactive waste disposal?
We are all mindful of the enormous quantity of radioactive waste generated during the reprocessing of nuclear reactor fuels, but as Wolke explains in What Einstein Told His Cook, “a food irradiator. is as different from a nuclear reactor as a flashlight battery is from an electric generating plant. Radioactive materials are indeed being used, but there is no waste build-up from their use.”
History of food irradiation
As noted in Table 18.1, the benefits of ionizing radiation have been known since 1905. In addition to its potential to reducetheincidenceoffoodbornediseases,food irradiation can be used to eliminate pests such as the screw worm fly, which preys on cattle, the Mediterranean fruit fly, and the tsetse fly, by the release of sterile insects. Worries about nuclear weapons, combinedwithanantiprogressideology, began to hinder food irradiation research afterthe war. Althoughthere wasatthat time an adequate supply of gamma rays, the high-energy, short-wavelength rays given off by radionuclides, the antitechnology factionconvincedtheCongressto control the development of nuclear technology for treating foods.
In 1958, when the Food, Drug, and Cosmetic Act was passed by the U.S. Congress, there were many unanswered questions. Would irradiated food be made radioactive? What would be the effect of this additional radioactivity above that of the background on human health? Would irradiation of food produce new toxic products such as carcinogens? Would the process produce products with excessive loss of nutrients or changes in food taste, odor, color, or texture? In the killing of pathogens, would new microbiological problems evolve? Also, what would be the adverse effects, if any, on the environment should there be accidents? What sources of radiation (gamma) and what doses would be suitable for irradiation?
Successful lobbying by well-known public figures in the movie and entertainment circles convinced the Congress to keep food irradiation under tight control, i.e., treating ionizing radiation as a "food additive." This part of the 1958 law, known as the Delaney Clause, assured that no irradiated food could be approved for consumption without a lengthy drawn-out procedure, thereby singling out and stigmatizing foods so treated by requiring a long period for research and petition writing to the FDA and the U.S. Department of Agriculture (USDA) and then many months or years for evaluation.
After 1961-1962, the U. S. Department of Army's food radiation research and development program made it the top priority to try to sort out the diverse claims, either pro or con, about irradiated foods. The U.S. Army Medical Services completed studies for testing in rats, mice, and beagle dogs, using 21 foods representing all major food classes in the diets of U.S. people. In June 1965 in a hearing by the Joint Committee on Atomic Energy, the army surgeon general submitted a statement that all foods irradiated at sterilizing doses up to 5.6 Mrad (56 kGy) using cobalt-60, or electrons at energies below 10 MeV, were wholesome, i.e., safe to eat and nutritionally adequate.
Nutritional assessments showed that the irradiation process was no more destructive to nutrients than other processes then being used commercially. It was also demonstrated that there were no toxic products formed in quantities that would be hazardous to the health and well-being of consumers.
The microbiological standard for irradiation-sterilized foods was to use a radiation dose sufficient to reduce a theoretical population of spores of Clostridium botulinum. This standard, recommended by the National Academy of Sciences and the National Research Council Advisory Committee to the army's program on food irradiation, was adopted. In the ensuing years, there was no record of any problem with possible C. botulinum survivors, although this has continued to be one of the antinuclear arguments against food irradiation.
Thousands of irradiated components of meals have been served to volunteers. In every respect, the tested irradiated foods have passed with soaring results. Irradiated foods have been eaten by astronauts on the moon flights and on many other space missions, by immunocompromised patients, and by military personnel in several parts of the world.
Every conceivable possibility for harm has been carefully considered — none has been found. Nor have any chemicals formed that are unique to food irradiation. In the meantime, irradiated foods have been approved by the health authorities in 40 countries.
Between 1964 and 1997, the World Health Organization (WHO), in concert with the Food and Agricultural Organization (FAO) and the International Atomic Energy Agency (IAEA), held a series of meetings of experts from many countries to assess the quality and safety of foods. In a meeting in September 1997, they recommended the approval of irradiated foods without restrictions at all doses, up to the highest dose compatible with organoleptic properties. At each meeting, the internationally recognized health authorities have concluded that all irradiated foods are safe to eat without the need for further toxicological testing, at doses as high as those allowing an acceptable taste.
In view of the foregoing, food scientists believe that the FDA and the USDA should follow the WHO/FAO/IAEA recommendation that food irradiation is a process. Scientists have thought for three decades that the legal fiction designating ionizing radiation as a food additive, instead of a food process, unjustly penalized food irradiation and helped delay its implementation for more than 30 years. On the other hand, during these years, the additive designation has stimulated those working in the field to perform at the highest level of good science, thus convincing the scientific community worldwide that food irradiation has an important role to play in combating hunger and disease.
In totality, scientists have reached their objective in documenting that food irradiation is a safe and beneficial process. Now scientists need to educate government officials, as well as health workers, food processors, marketers, and the public, on the safety and advantages of food irradiation.
With approximately 9000 people dying annually from food poisoning in the U.S., and an estimated 30,000,000 cases of food infection each year, there is little doubt that the time has come to use food irradiation more widely for the benefit of human health. Ironically, in applying ionizing radiation to protect public health against foodborne pathogenic bacteria, public health officers currently face the same arguments that were voiced against pasteurization at the beginning of the century and later against canned and frozen foods. In the history of pasteurization, many voiced disbeliefs of pasteurization's benefits for sanitation, nutrition, physical and bacteriological quality, consumer health and safety, and economics. Loss of hair, skin tone, and general well-being, as well as potency, was also claimed. These mistaken beliefs are cited currently against the irradiation of food.
Food irradiation is now recognized as another method of preserving food and ensuring its wholesomeness by sterilization or cold pasteurization, and has wide application worldwide. If it had been in place in the U.S., recent foodborne disease outbreaks caused by E. coli O157:H7, which are found in food-producing animals, would not have occurred. There have been tens of thousands of Salmonella, Campy-lobacter, Yersinia, Listeria, and Escherichia coli foodborne disease outbreaks related to poultry and meat, the totals exceeding millions of human illnesses, over the last 40 years since the Delaney Clause established the travesty that gamma rays were a food additive.
We may never know how many thousands of deaths and illnesses could have been prevented if public health authorities had implemented food irradiation and educated the public about its benefits. The morbidity and medical expense of meat-and poultryborne diseases can be prevented, just as milkborne disease can be prevented by pasteurization. All the bacteria cited previously can be present in unpas-teurized milk, even though the U.S. Public Health Service Grade A standards require that milk be free of disease-causing organisms. Imagine the public outcry if governments allowed the marketing of unpasteurized milk in which Salmonella or E.
coli virulent strains were found or soft cheese or Mexican-style cheese in which Listeria wasfound.
In 1984, Margaret Heckler, Secretary ofHealth,endorsedfoodirradiation,after lengthy studies had proven its safety. If public health officers had spoken out then for the irradiation of foods that are known to carry pathogenic bacteria, events such as the E. coli O157:H7 outbreaks from undercookedhamburger(3deathsandmore than 400 cases of illness) that occurred inthenorthwestU.S. inJanuary 1993 could have been prevented. Even today, no national or state local health authority speaks in favor of requiring pasteurization by irradiation of hamburger meat patties, of which some tens of millions are consumeddaily. Thesameattitudeandapathyexist in Europe, where Listeria-contaminated pork meat and other food caused the death of 63 persons in France, as reported in 1993. Since then, Listeria has become a serious public health problem in the U.S.
What is irradiation? Irradiation is definedasexposuretoradiation(rays). Radius is taken from Latin, meaning ray. The radiationusedinthefoodirradiationprocess comes either from radioactive isotopes of cobalt or cesium or from devices that produce controlled amounts of x-rays, gammarays,orhigh-energyelectrons. The process exposes food to radiation but does not and cannot make the food radioactive. Gamma rays and x-rays emit waves of highfrequenciesandhighenergies.These waves produce enough energy to strip electrons from atoms, leaving ions (particles charged with electrical charge), or ionizingradiation.Ionizingradiationistheenergy that exists in the form of waves and is definedbyits wavelength. Asthe wavelength of energy gets shorter, the energy of the waveincreases. Theelectromagneticspectrum (Figure 18.1) identifies the kinds of energy that exist and how they are used. Visible light, radio and television waves, and microwaves are examples of nonionizing radiation. They cause molecules to move, but they cannot structurally change the atoms in the molecules. The energy is measured by frequency (Hz), which is the number of times per second that the wave completes its cycle in an electromagnetic field.
Simple cooking involves the absorption of infrared radiation or heat by the food. Early on, it was found that shortwave radiation could melt things such as a chocolate
INFRARED < ULTRAVIOLET "HARD" X-RAYS
MICROWAVES E "SOFT" X-RAYS GAMMA RAYSr
106 107 108 109 1010 10" 1012 1013 1014 1015 1016 10" 1018 10IM 102 _I_I_I_I_I_I_I_I_I_I_I—
,12 HA13 HA14 m15 HA18 H A20
(electron volts) 10-9 iQ-8 !Q-7 iQ-6 iQ-5 10-4 10-3 10-2 10-1 1 101 102 103 104 105 106
Frequency bar. Shortwave radiation led to the inventionofmicrowaves.In themicrowave,radio waves, with shorter wavelengths and higherfrequenciesthanthoseusedforcommu-nication, cause water and other polar molecules within food to vibrate. Vibration can be up to 2.5 billion times/sec, which is enoughvibrationtocauseheatbyfriction. Both cooking by heat and microwave are examplesoftheuseofnonionizingradiation.
High frequencies constitute ionizing radiation. Theradiationpassesthroughthe food without generating intense heat, disruptingcellularprocessessuchassprouting, ripening, or growth of microbes, parasites,andinsects.Ionizingradiationhashigh energy — high enough to change atoms by knocking an electron from them to form an ion, but not high enough to split atomsandcause exposedobjectstobecome radioactive. Therefore, the sources of radiationallowedforfoodprocessing(cobalt-60, cesium-137, accelerated electrons, and x-rays) cannot make food radioactive. Food irradiation makes use of high frequenciesconstitutingionizingradiation.In contrast, during a nuclear meltdown, incrediblyhighlevelsof ionizingradiationare emitted, because of which not only is the growth of microorganisms disrupted but the food itself can become radioactive. Thus,thedifferenceis amatterofmagnitude, owing to which people can enjoy the benefitsofionizingradiationwithno worries about radioactive contamination.
Foods are processed in facilities designedforthatpurpose. Figure 18.2 shows the floor plan for a gamma irradiation facility. It consists of three areas. The outer area where food is received for processing and stored before and after processing is like any other food warehouse. If frozen or perishable foods are processed in the facility, it must have appropriate refrigeration facilities. No other requirements are unique to the area. The second area is the conveyor or other system used to transport the food to be processed. Food to be processed is loaded onto the conveyor and carried to the irradiation source, where it absorbs the energy needed to accomplish the desired effect. The third, the inner area, is the processing room. In this room, the source is stored until needed to process the food. In the case of gamma sources, a pool of water is used to store the source when it is not used to prevent radiation from escaping. When the source is raised into the room, concrete walls provide a shield to prevent the escape of radiation into the storage area. In the case of irradiation generated by a machine, the same shielding is used to prevent escape of radiation, but no other shielding is needed because no radiation is generated when the machine is turned off.
Processing facilities are safe for the employees who work there and for the surrounding environment. Facilities using gamma sources must be licensed by the U.S. Nuclear Regulatory Commission or an equivalent state agency to assure that they can be operated safely. All facilities must meet requirements of the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) to assure that workers and the environment will not be adversely affected in any way. In addition, when gamma sources are moved to or from the facilities, they are carried in special containers that have been proven safe for the purpose by the U.S. Department of Transportation. In more than four decades of transporting gamma sources in North America, there has never been an accident that has resulted in the escape of radioactive materials into the environment. Also, no radioactive waste is generated by irradiation all spent sources are returned to the firm that supplied them for storage or further processing.
FIGURE 18.2 Facility used to irradiate foods.
During the process of food irradiation, ions are formed. The ions can cause chemical changes within the food, e.g., splitting of water molecules, which may recombine to form hydrogen peroxide. Such products may react with food to lower nutritional value or produce undesirable by-products. Food irradiation is a cold process, i.e., it achieves its effect with little rise in the temperature of the food. There is little, if any, change in the physical appearance of irradiated foods, because they do not undergo the changes in texture or color as do foods preserved by heat pasteurization, canning, or freezing. Food remains close to its original state. However, problems that have occurred include some off-flavors in meat and excess tissue-softening, which has been documented in fresh peaches and nectarines.
effectiveness of irradiation
Currently, there are three dose levels of food irradiation, based on their applications. Low-dose applications, using less than 0.1 kGy, are effective against sprouting of infesting insects. Doses of 0.2 to 1 kGy kill infesting insects. Low-dose irradiation delays ripening and extends the shelf life of fruits, e.g., strawberries, bananas, mangoes, papayas, guavas, cherries, tomatoes, and avocados. Pasteurizing doses
(radurized) of 1 to 3 kGy kill populations of microbes, and are effective against Salmonella, Campylobacteria, and parasitic liver flukes. Such doses destroy pathogenic microorganisms that might be present in milk and delay spoilage by significantly reducing the number of microbes responsible for spoilage. In Europe, irradiated milk has been used for years and is very popular because before opening it can be stored safely at room temperature. Sterilizing doses (reappertization) of 25 to 50 kGy decrease the number of nonsporing pathogenic organisms.
Early trails of irradiated foods resulted in undesirable changes both in taste and texture. Dairy products (cheeses) proved not to be good candidates for irradiation. There were also changes in aroma and texture of citrus crops.
Although the United States food supply is generally considered one of the safest in the world, foodborne illnesses remain a concern. Each year, millions of Americans become ill and as many as 5000 die from foodborne infections. The United States Department of Agriculture estimates that medical treatment and productivity losses associated with foodborne illnesses cost as much as $37 billion annually. Irradiation, which involves exposing food briefly to radiant energy, can reduce or eliminate microorganisms that contaminate food or cause spoilage. So far, only limited quantities of irradiated foods—spices, herbs, dry vegetable seasonings, and some fresh fruits, vegetables, and poultry—have been available in the United States. Major purchasers are health care and food service establishments. The World Health Organization reviewed 500 studies and concluded that food irradiation poses no toxicological, microbiological, or nutritional problems. In more than 40 years, there have been no accidents in North America involving transport of the types of radioactive isotopes used for irradiation.
Pasteurization or sterilization of food by irradiation is a technology useful for all classes of food, especially meat and poultry. The international unit for the dose of radiation absorbed is the gray (Gy), which is equal to 100 rads or 10,000 ergs per gram. A kilogray is equal to 1000 Gy. In general, doses <10 kGy are pasteurization doses, and doses >10 kGy are sterilization doses. The World Health Organization, the Food and Agricultural Organization, the International Atomic Energy Agency, and many countries worldwide have endorsed food irradiation so that people can have better and safer food. Astronauts have used irradiated sterilized food since the earliest space exploration.
What is food irradiation? Food is subjected to a specific dose of ionizing radiation from a radioactive isotope of cobalt or from devices that produce electrons or x-rays. This process does not make the food radioactive. Irradiation causes a variety of changes in living cells. How can one treatment do so many different things? High doses kill the cells by fragmenting the DNA, thus killing contaminating microorganisms or insects. Lower doses alter biochemical reactions, such as those involved in fruit ripening or spoilage, and interfere with cell division, which is necessary for the reproduction of parasites.
Foodborne illness is one of the largest preventable public health problems in the United States. Studies by the US Centers for Disease Control and Prevention show that foodborne diseases, such as those caused by Listeria, Salmonella, Campylobacter, Vibrios, and Trichinella species, Escherichia coli, and tapeworms and other parasites, claim thousands of lives annually and cause millions of cases of diarrheal disease and complications. Economic losses associated with foodborne diseases are estimated at several billion dollars by the US Department of Agriculture [ 1]. The enormous tragedy is that many of these deaths, illnesses, and expenses were and are preventable with the application of current knowledge and proven technology—namely, irradiation. However, diseases of human origin can still contaminate food after irradiation or pasteurization, and therefore the hygienic handling of food is important.
At the same time and parallel with research on the irradiation of food came the irradiation of medical supplies, which came into use in the 1960s in the United States. Today, some 80% of all disposable medical items, as well as many other products, are sterilized in this way. In addition, hundreds of household items in daily use are irradiated to ensure sterilization. Further, some products, such as lumber, wooden flooring, and fiberglass wires, are irradiated to extend and increase durability and functionality.
The slow acceptance of irradiation of food, compared with its rapid acceptance and wide use in treating medical products and commercial goods, is a consequence of the revised Food and Drug Act of 1957, in which irradiation was defined as a food additive instead of a process. Accordingly, subsequent US Food and Drug Administration regulations required extensive testing to ensure the safety of food irradiation. Recently, the US General Accounting Office report to the Congress reviewed the process, and its report [ 1] (which can guide interested readers to the extensive literature—some 6000 articles) supports food irradiation, adding to the endorsements of the world scientific community.
It is unfortunate that so many objections to irradiation have arisen in the past 50 years they are reminiscent of the innumerable objections that public health authorities have previously faced regarding other services to protect the public, such as chlorination and fluoridation of water, pasteurization, and even vaccination. In contrast to their efforts on behalf of these previous innovations, public health officers did not strongly support food irradiation, even though the American Medical Association, the American Council on Science and Health, the American Veterinary Medical Association, the Council for Agricultural Science, the National Food Processors Association, the American Meat Institute, and universities with food science departments all were early supporters. Fortunately, the leaders of the US Public Health Service supported food irradiation. In 1992, James Mason, MD, then the Assistant Secretary of Health, stated in a Public Health Service Reports editorial conclusion that “The bottom line on food irradiation is that the nation deserves to have—and should claim—the health benefit this technology will surely provide. We don't know how great that benefit will be—but we do know it will be significant” [ 2]. Two years later, Philip R. Lee, MD, the Assistant Secretary of Health and Director of the US Public Health Service, stated:
It is the US Public Health Service's responsibility to use what we know to protect and improve the health of the public. Each modern food-processing advance—pasteurization, canning, freezing—produced criticism. Food irradiation is no different. It is up to leaders in the health professions to dispel the myths.
The technology of food irradiation has languished too long already. Perhaps our nation has become dangerously complacent about the importance of public health measures. The current health care debate offers us both a mandate and an opportunity to increase the understanding in the importance of public health for ensuring personal health. If this message is lost, our efforts to advance and protect the nation's health will not succeed. [ 3]
In 1999, Michael Osterholm, of the Minnesota Health Department, organized a symposium to promote food irradiation to public health officials and food industry officers. In 2000, the first irradiated hamburger patties became available in Minnesota and the upper Midwest and were widely accepted and are now available nationwide. In addition, the Florida Health Department has taken a leadership role in promoting the acceptance of irradiated meat, poultry, and other products, such as fruit and vegetables, for the young and old, especially those in nursing homes and hospices.
Milk pasteurization was a new public health practice in 1900, a process important in the control of childhood diseases and in improving nutrition. This technology cannot be applied to many common food sources of infection, including meat, poultry, fish, vegetables, and fruit. The development and application of irradiation in 2000 offers a low-cost solution to an age-old health problem. Indeed, on the basis of scientific evidence, food irradiation is an effective means of controlling foodborne pathogens and enhancing food safety. However, although irradiation is approved for use on most food items, the lag in consumer acceptance has precluded the extension of this technology to a broader spectrum of food items.
Since the advent of antibiotics some 50 years ago, there has been increasing concern regarding their use in food production. Antibiotics are used in the treatment and prevention of animal diseases, and some are used to promote growth. Some of the gram-negative bacteria—Salmonella, Campylobacter, and coliforms—have developed resistance to antibiotics they are frequently identified as the cause of human diseases that do not respond to antibiotic therapy. However, irradiation of meat and poultry that might be contaminated with bacteria resistant to antibiotics effectively inactivates these pathogens, just as it does other contaminants. In this regard, irradiation is effective in protecting the public health.
As stated previously, the objections to pasteurization, canning and freezing, water chlorination and fluoridation, and vaccination, as well as misinformation and misconceptions regarding the safety of food irradiation, have fueled consumer skepticism. To paraphrase Pogo, “We have met the enemy, and the enemy is us.” There is an urgent need for health practitioners to speak out on the benefits of irradiation to ensure food safety for all of us in the 21st century.
In the absence of oxygen, radiolysis of lipids leads to cleavage of the interatomic bonds in the fat molecules, producing compounds such as carbon dioxide, alkanes, alkenes, and aldehydes. In addition, lipids are highly vulnerable to oxidation by free radicals, a process that yields peroxides, carbonyl compounds, alcohols, and lactones. The consequent rancidity, resulting from the irradiation of high-fat foods, is highly destructive to their sensory quality. To minimize such harmful effects, fatty foods must be vacuum-packaged and held at subfreezing temperatures during irradiation.
Proteins are not significantly degraded at the low doses of radiation employed in the food industry. For this reason irradiation does not inactivate enzymes involved in food spoilage, as most enzymes survive doses of up to 10 kilograys. On the other hand, the large carbohydrate molecules that provide structure to foods are depolymerized (broken down) by irradiation. This depolymerization reduces the gelling power of the long chains of structural carbohydrates. However, in most foods some protection against these deleterious effects is provided by other food constituents. Vitamins A, E, and B1 (thiamine) are also sensitive to irradiation. The nutritional losses of a food product are high if air is not excluded during irradiation.
Examples of Food Irradiation
Ionizing radiation is commonly used to irradiate food products in order to sterilize foods for the protection of consumers against various pathogens found in meat and vegetables, or to delay the germination of various plants. Food irradiation is often termed “cold pasteurization” because it does not heat foods like traditional pasteurization. During the irradiation process, entire food pallets will be subjected to the predetermined dose. The dose is monitored by a densitometer, which ensures that the food products are exposed to the correct dose as determined by defined regulations. Each country has regulations concerning the dose of irradiation that can be applied to foods. The specific radiation dose is categorized as either high, medium, or low doses. Some examples are as follows:
- High: Dosage higher than 10 kGy. Meat products (e.g., poultry) is commonly sterilized with a high dose of radiation.
- Medium: Dosage between 1 and 10 kGy. The purpose is generally to eliminate micro-organisms from food products to prevent spoilage and the spread of pests.
- Low: Dosage lower than 1 kGy. Low doses are typically used to delay germination and ripening of plants.
Irradiation for Agricultural Applications
Irradiation techniques are widely applied in agriculture to introduce genetic variation in plants, as well as delay plant germination and sprouting. Moreover, irradiation is also applied to crops as a form of insect control. In agriculture, X-rays, gamma rays, UV light, and heavy-ion beams are the most common forms of irradiation used. The irradiation of food products is highly regulated, with the dose tightly controlled. Any chemicals generated via the irradiation process have been deemed non-toxic and comparable to those present following other sterilization methods. In agriculture, the prevention of spoilage is largely achieved through pest control (e.g., insects, viruses, and bacteria) by eliminating pathogens using a safe dose of radiation. In addition to pest control, irradiation also decreases the function of enzymes that promote spoilage and ripening following the harvest of crops. Since the spoilage of food products is reduced by irradiation, both transport time and shelf life can be extended.
The most common form of food irradiation is gamma radiation. Gamma rays are emitted from the decay of radioactive material. For safety purposes, the radioactive material is placed into a storage container surrounded by water or shielded to prevent food products and workers from exposure to the radioactive material. The most common source of gamma radiation for food products is cobalt-60 (see below). Gamma radiation is the most preferred type of food irradiation because the rays fully penetrate the food pallet and it is relatively inexpensive compared to some of the other forms of radiation (e.g., X-rays and electron radiation).
Food irradiation with the use of X-rays involves the collision of X-rays with food products. The advantage of X-ray irradiation is that the use of radioactive materials is not required and it provides greater dose uniformity compared to gamma radiation. Moreover, since X-rays are generated electronically, the devices can be turned off when not in use, which decreases the associated safety concerns for the workers. However, X-ray radiation is not used to the same extent for food irradiation purposes as gamma rays because it is more expensive.
1. A concern associated with electron irradiation of food products would be:
A. Exposure to radioactive material
B. Adequate penetration of the food products
C. The generation of toxic chemicals
D. Exposure to X-ray radiation
2. Which of the following is NOT a primary purpose of food irradiation:
B. Delay food ripening
C. Enhance food taste
D. Delay plant spouting