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Food irradiation is a promising food safety technology that can eliminate disease-causing microorganisms such as E. coli O157:H7, Campylobacter, and Salmonella from foods. The Food and Drug Administration (FDA) has approved irradiation of meat and poultry and allows its use for a variety of other foods, including fresh fruits and vegetables, and spices. The agency determined that the process is safe and effective in decreasing or eliminating harmful bacteria. Irradiation also reduces spoilage bacteria, insects and parasites, and in certain fruits and vegetables, it inhibits sprouting and delays ripening. The effects of irradiation on the food and on animals and people eating irradiated food have been studied extensively for more than 40 years. These studies show clearly that when irradiation is used as approved on foods:
Irradiation is a safe and effective technology that can prevent many food borne diseases, thereby increasing public health.
Food irradiation is “cold pasteurization”
The food irradiation process uses energy from the wavelength of 10 –10 to 10–12 meters on the electromagnetic spectrum, a frequency of 1018 to 1020 and energy levels up to 10 megaelectronvolts, or MEV. This amount of energy is so low that it has been called cold pasteurization. When we think of sterilization processes, we commonly think of milk pasteurization, which is a heat process. In heat pasteurization, the product is brought up to a temperature of over 161 F (72 C).
Don’t confuse ultra violet radiation and irradiated milk with food irradiation! They use different processes. All food products treated with ionizing radiation are clearly labeled with the radura, the international symbol indicating a food product has been irradiated. The symbol’s graphical details and colors vary between countries.
Food irradiation kills microbes, but does not affect food products
The food product does not change when treated with food irradiation. Heat sterilization processes damage both the food and the microbe. Cold sterilization selectively targets the microbe, or pathogen. This is a big advantage to the food industry and consumer. Eliminating the offending microbe while preventing any changes to the food composition is a huge benefit to the food industry and to the consumer.
There are three sources of the energy used in food irradiation: beta particles, gamma waves and x-rays. All three sources have the same effect on the pathogens. In the commercial setting, each has its advantages and disadvantages.
DID YOU KNOW?
- Radioisotopes are used to reduce post-harvest losses by suppressing sprouting.
- Radiation is used to preserve seeds and food products.
- Radioisotopes help researchers as they develop disease-resistant plants and animals.
- Radioisotope methods are used in hydrology to study and predict water supply.
- Radiation techniques in pest control reduce the use of toxic chemicals.
Common uses of food irradiation in the U.S.
In the USA, food irradiation is used as follows:
The United Nations Food and Agriculture Organization estimates that 25 percent of the world’s food supply is lost every year to pests and bacteria while people die of hunger. Hundreds of millions of people worldwide are affected by diseases caused by contaminated food. Irradiation using radioisotopes has proved effective in controlling pathogenic bacteria and parasites in food products such as meat, poultry, fruits and vegetables, and seafood and spices. The process is being utilized in many countries and its use is expanding globally.
No. Irradiation by gamma rays, X-rays and accelerated electrons under controlled conditions does not make food radioactive. Just as the airport luggage scanner doesn’t make your suitcase radioactive, this process is not capable of inducing radioactivity in any material, including food.
Special labels are required on irradiated foods, including the international symbol of irradiation, known as a “radura”, and a statement indicating that the food was treated with irradiation.
No. Neither irradiation nor any other food treatment can reverse the spoilage process and make bad food good. If food already looks, tastes or smells bad – signs of spoilage – before irradiation, it cannot be “saved” by any treatment including irradiation.
Presently over 40 countries have approved applications to irradiate approximately 40 different foods. These include such items as fruits, vegetables, spices, grains, seafood, meat and poultry. More than half a million tons of food is now irradiated throughout the world on a yearly basis. Although this amount represents only a fraction of the food consumed annually, it is constantly growing. This trend is due to three main factors:
1. Increasing concerns over food borne diseases
Food borne diseases pose a widespread threat to human health and they are an important cause of reduced economic productivity. Studies by the US Center for Disease Control in 1999 estimated that food borne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year. Economic losses associated with such food borne diseases are high-estimated between US $6.5 billion and $33 billion.
2. High food losses from infestation, contamination and spoilage.
The FAO has estimated that about 25% of all worldwide food production is lost after harvesting to insects, bacteria and spoilage. Economic losses due to insects and microbes have been estimated to fall between $5 and $17 billion yearly in the US alone. Food irradiation can help reduce these losses and can also reduce our dependence on chemical pesticides, some of which are extremely harmful to the environment (e.g. methyl bromide).
3. Growing international trade in food products.
As our economies become more global, food products must meet high standards of quality and quarantine in order to move across borders. Irradiation is an important tool in the fight to prevent the spread of deleterious insects and microorganisms.
The process involves exposing the food, either packaged or in bulk, to carefully controlled amounts of ionizing radiation for a specific time to achieve certain desirable objectives. When microbes present in the food are irradiated, the energy from the radiation breaks the bonds in the DNA molecules, causing defects in the genetic instructions. Unless this damage can be repaired, the organism will die or will be unable to reproduce. It matters if the food is frozen or fresh, because it takes larger radiation dose to kill microbes in frozen foods. The effectiveness of the process depends also on the organism’s sensitivity to irradiation, on the rate at which it can repair damaged DNA, and especially on the amount of DNA in the target organism:
If the food still has living cells, they will be damaged or killed just as microbes are. This is a useful effect: it can be used to prolong the shelf life of fruits and vegetables because it inhibits sprouting and delays ripening.
Yes, the foods are not changed in nutritional value and they don’t become dangerous as a result of irradiation. At irradiation levels approved for use on foods, levels of the vitamin thiamine are slightly reduced, but not enough to result in vitamin deficiency. There are no other significant changes in the amino acid, fatty acid, or vitamin content of food. In fact, the changes induced by irradiation are so minimal that it is not easy to determine whether or not a food has been irradiated. A big advantage of irradiated food, is that it is a cold process: the food is still essentially “raw”, because it hasn’t undergone any thermal process.
A variety of foods have been approved for irradiation in the United States, for several different purposes. For meats, separate approval is required both from the FDA and the USDA. However, irradiated foods are not widely available yet. Some stores have sold irradiated fruits and vegetables since the early 1990s. Irradiated poultry is available in some grocery stores—mostly small, independent markets— and on menus of a few restaurants. On the other hand, most spices sold wholesale in this country are irradiated, which eliminates the need for chemical fumigation to control pests. American astronauts have eaten irradiated foods in space since the early 1970s. Patients with weakened immune systems are sometimes fed irradiated foods to reduce the chance of a life-threatening infection. In addition, irradiation is widely used to sterilize a variety of medical and household products, such as joint implants, band-aids, baby pacifiers, cosmetic ingredients, wine and bottle corks, and food packaging materials.
No. Irradiation is equivalent to pasteurization for solid foods, but it is not the same as sterilization. Food irradiation can be an important tool in the war against illness and death from food borne diseases. It is not a substitute for comprehensive food safety programs throughout the food distribution system. Nor is food irradiation a substitute for good food-handling practices in the home: irradiated foods need to be stored, handled and cooked in the same way as non-irradiated foods.
Yes, any food processing method will add cost. Canning, freezing, pasteurization, refrigeration, fumigation, and irradiation will add cost to the food. These treatments will also bring benefits to consumers in terms of availability and quantity, storage life, convenience, and improved hygiene of the food. The increase in price for irradiated fruits and vegetables is estimated at 2 to 3 cents per pound. Irradiated poultry and meat products are expected to cost 3 to 5 cents a pound more than non-irradiated meat. The price is likely to decline as irradiated foods become more widely available.
The effectiveness of the treatment in eliminating pathogens will be regulated as a food safety process, by either the USDA or the FDA, often in concert with State authorities, just as is the case now for milk pasteurization or retort canning. The safety of operations of irradiation facilities is regulated separately. This requires extensive worker training, supervision, and regulatory oversight. Facilities using radioactive sources are regulated by the Nuclear Regulatory Commission (NRC). To be licensed, the facility must have been designed with multiple fail-safe measures, and must establish extensive and well documented safety procedures, and worker training. The safe transport of the radioactive sources is regulated by the Department of Transportation.
No. It is impossible for a “meltdown” to occur in a gamma irradiator or for the radiation source to explode. The source of radiation used at irradiators cannot start a fission chain reaction, and it does not emit neutrons that could activate materials. The walls of the irradiation cell through which the food passes, the machinery inside the cell, and the product being processed cannot become radioactive. No radioactivity is released into the environment.
No. The food irradiation facilities themselves do not become radioactive, and do not create radioactive waste. Cobalt 60 is manufactured in a commercial nuclear reactor, by exposing non-radioactive cobalt to intense radiation in the reactor core. The cobalt sources used in irradiation facilities decay by 50% in five years, and therefore require periodic replacement. The sources are removed from the irradiator when the radioactivity falls to a low level, usually between 6% and 12% of the initial level (this takes 16 to 21 years for cobalt-60). The small radioactive cobalt “pencils” are shipped back to the original nuclear reactor, where they can be reactivated for further use. The shipment occurs in special hardened steel canisters that have been designed and tested to survive crashes without breaking. Cobalt is a solid metal, and even if somehow something should break, it will not spread through the environment. Cobalt 60 may also be disposed of as a radioactive waste. Given its relatively short half life (5 years) and its stable metallic form, the material is not considered to be a problematic waste.
Center for Nuclear Science and Technology Information of the American Nuclear Society
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