Rayfresh Foods in The News
Jan 19, 2009
A new irradiation process could give producers a way to fit irradiation machines directly into their packing lines.
Dec 29, 2008
Michigan State University researchers are helping a technology startup company improve the safety of leafy greens and other foods as more consumers seek to eat fresh and healthy.
Frequently Asked Questions
What is food irradiation?
Food irradiation is the treatment of foods by exposing them to ionizing radiation. For example, irradiation can kill harmful bacteria and other organisms in meat, poultry, and seafood, disinfest spices, extend shelf-life of fresh fruits and vegetables, and control sprouting of tubers and bulbs such as potatoes and onions. It is a safe process that has been approved by the U.S. Food and Drug Administration (FDA) and over 50 other national food control authorities for many types of foods. Irradiation may be referred to as a "cold pasteurization" process, as it does not significantly raise the temperature of the treated foods. As with other microbial inactivation processes, such as heat pasteurization, irradiation cannot reverse the spoilage of food. Thus, safe food handling and good manufacturing practices are required for irradiated food just as for other foods.
Why irradiate foods?
One reason is that the Centers for Disease Control and Prevention (CDC) estimate that some 5,000 deaths and 76 million illnesses a year in the U.S. occur due to foodborne illnesses-that toll could be substantially reduced by irradiation. Foods may be contaminated naturally during any stage of production or consumption (from farm to fork). The contamination may be in the form of microbes-including those that cause food spoilage or diseases in humans-as well as insect infestations that cause food spoilage and destruction. Some foods are seasonal and highly perishable, while others are not allowed to enter the United States because they may harbor pests and diseases that cause damage to local agriculture or illness in humans.
Irradiation, being a cold process, can be used to inactivate spoilage and disease-causing (pathogenic) bacteria in solid foods such as meat, poultry, seafood, and spices. It can also kill insect eggs and larvae in fresh fruits and vegetables without changing the foods' quality or sensory attributes. Its ability to inactivate pathogenic bacteria in frozen food is unique. Since irradiation is a cold pasteurization process, foods remain in the same state after irradiation as before, i.e. frozen foods stay frozen, raw foods remain raw, and volatile aromatic substances are retained.
The increasing awareness of foodborne disease outbreaks, as well as major food recalls to meet strict sanitary standards in the United States, has resulted in an increasing recognition and a wider use of irradiation as a sanitary treatment to destroy pathogenic bacteria such as Escherichia coli O157:H7 in ground beef. Its role as an insect control method to meet strict quarantine requirements in the U.S., especially for tropical fruits from Hawaii, is also growing. Irradiation has routinely been used to meet microbiological standards for spices and dried vegetable seasonings in the U.S. and many other countries in the past two decades.
What types of radiation energy are used for treating foods?
The radiation energy used to treat foods is called "ionizing radiation" because it produces ions--electrically charged particles. Ionizing radiation-including X-rays, gamma rays and beams of high-energy electrons produced by electron accelerators-has a higher energy than non-ionizing radiation such as visible light, television and radio-waves and microwaves.
Two types of radiation sources are commonly used for food treatment. The first is a tightly sealed metal container of radioactive elements-cobalt 60 or cesium 137-that produce gamma rays. The rays are directed onto the food being irradiated, but the food itself never comes into contact with the cobalt or cesium source.
The second type of radiation source is a machine that produces either X-rays or high-energy electrons. Because of the physical characteristics of these sources, no radioactivity can be induced in food thus treated, no matter how much energy (dose) is absorbed by the food or how long the food is irradiated.
What can irradiation do?
Irradiation has a number of uses in food processing, most of which improve the safety and quality or prolong the useful life of foods. Different doses of radiation are used for different purposes. Food-borne illnesses take a heavy toll on the economy and productivity of populations in most countries. In the United States, the Centers for Disease Control and Prevention (CDC) estimates that food-borne diseases cause approximately 76 million illnesses; 325,000 hospitalizations and 5,000 deaths each year or approx. 100 deaths per week. Such microorganisms as E.-coli O157:H7, Campylobacter, Salmonella, Listeria, Vibrio and Toxoplasma are responsible for 1,500 deaths annually. The most important public health benefit of food irradiation is its ability to destroy pathogenic (disease causing) organisms in food. Consumers are familiar with heat pasteurization of liquid foods like milk and juices, which effectively eliminates spoilage and pathogenic bacteria, inactivates spoilage enzymes, and extends shelf-life without significantly altering taste and nutritional value. Irradiation can perform the same protective functions for solid foods by decreasing significantly the number of microorganisms in foods without causing significant changes in their flavor and aroma. It is the only process that can do so effectively in raw and frozen foods. It is important to note that irradiation cannot make up for mishandling or unsanitary food processing practices. Irradiated foods must be properly packaged to prevent re-contamination, kept at proper temperatures, and handled with care during food preparation to avoid cross contamination from other (unirradiated) foods or unsanitary utensils. Improved food handling alone could reduce but not prevent contamination by pathogenic bacteria. Irradiation gives us an additional, complementary tool to ensure food safety.
What are the effects on microorganisms in foods?
Different types and species of microorganisms have different sensitivities to irradiation. Spoilage and disease-causing (pathogenic) bacteria of different species, the major causes of food spoilage and many common food-borne diseases, are generally sensitive to irradiation and can be inactivated by low and medium doses of radiation between 1 and 7 kGy. Bacterial spores are more resistant and require higher doses (above 10 kGy) for inactivation. As with any sub-sterilization process, special care must be taken when irradiating food using low and medium doses to kill off spoilage and pathogenic bacteria, to avoid growth and toxin production by spores of Clostridium botulinum bacteria (which causes botulism poisoning) that may be in some foods, and which can survive the treatment. Yeasts and molds, which can spoil some food, are slightly more resistant to irradiation than are bacteria and require a dose of at least 3 kGy to inactivate them. Since viruses are highly resistant to radiation and require a dose of between 20 to 50 kGy to inactivate them, irradiation would not be a suitable means of dealing with viral contamination of foods.
There is a misconception that food irradiation produces harmful mutant strains of pathogenic microorganisms that might flourish in the absence of the bacteria killed by irradiation. Results of research carried out to examine this potential risk have been reassuring. Irradiation of food at doses required to inactivate spoilage and disease-causing bacteria results in major damage to their chromosomes(and DNA)-damage that is beyond repair. Thus, any surviving pathogenic bacteria in irradiated food are significantly injured and they are unable to reproduce. The food, on the other hand, that might be contaminated is not alive and thus is not damaged by irradiation.
Is irradiation the same thing as cooking in a microwave oven?
No. Irradiation involves the treatment of food with ionizing radiation to achieve desired effects, e.g., killing pathogens, extending shelf-life, controlling sprouting, replacing chemical fumigation, etc., without significantly increasing the temperature of food. Thus it is a non-thermal process. In contrast, microwave ovens expose foods to a non-ionizing radiation that generates heat by increasing the molecular motion of the water molecules in moist foods, thus cooking them.
Does irradiation make food radioactive?
No. Irradiation does not make food radioactive. The types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. Food undergoing irradiation does not become any more radioactive than luggage passing through an airport X-ray scanner or teeth that have been X-rayed. It should be noted that everything in our environment, including food, contains natural trace amounts of radioactivity (background level). Irradiation of food at any dose will not result in an increased radioactivity beyond that of the background environment.
Does irradiation generate radioactive wastes?
No. The process simply involves exposing food to a source of radiation. It does not create any new radioactive material. When the strength (activity) of radioactive sources such as cobalt or cesium falls below economical usage levels, the sources are returned in a licensed shipping container to the suppliers, who have the option of either reactivating them or storing them in a regulated place. Basically, the same procedures are followed when an irradiation plant closes down. The radiation sources can be acquired by another user or returned to the supplier, the machinery dismantled, and the building used for other purposes. When a machine source such as electron beam or X-ray generators, which use electricity as their power sources, is used for irradiating food, neither radioactivity nor radioactive materials is involved.
Are irradiated foods safe to eat?
Yes. The safety of food irradiation has been thoroughly studied and comprehensively evaluated for over 50 years, both in the United States and elsewhere. No food technology has ever been as extensively studied and evaluated with respect to safety as has food irradiation. The studies involved many animal feeding tests including multigeneration tests in animals, e.g., rats, mice, dogs and monkeys, to determine if any changes in growth, blood chemistry, histopathology or reproduction occurred that might be attributable to consumption of different types of irradiated foods as part of their daily diets. Data from these studies were systematically evaluated by panels of experts that included toxicologists, nutritionists, microbiologists, radiation chemists and radiobiologists, convened repeatedly by the Food and Agricultural Organization of the United Nations (FAO), International Atomic Energy Agency (IAEA) and World Health Organization (WHO) in 1964, 1969, 1976, 1980 and 1997, as data became available. In 1980, the Joint FAO/IAEA/WHO Expert Committee on the Wholesomeness of Irradiated Food (JECFI) concluded that ?Irradiation of any food commodity up to an overall average dose of 10 kGy introduces no toxicological hazard; hence, toxicological testing of food so treated is no longer required.? The JECFI also stated that irradiation of food up to a dose of 10 kGy introduces no special microbiological or nutritional problems.
Investigations since 1981 have continued to support the JECFI?s conclusions about the safety of food irradiation. These investigations included a small human feeding trial in China in which 21 male and 22 female volunteers consumed 62 to 71% of their total caloric intake as irradiated foods for 15 weeks. Since 1980, there has been no credible scientific evidence, either from human feeding studies or from consumption of several types of irradiated foods available in commercial quantities in several countries that indicate such foods pose a toxic hazard. In 1997, FAO, IAEA and WHO convened a Joint Study Group to evaluate data on wholesomeness studies of food irradiated with doses above 10 kGy. Based on scientific evidence supporting the safety of food irradiated with any dose, above or below 10 kGy, the Joint Study Group concluded that food irradiated with any dose to achieve technical objectives is safe and nutritionally adequate. No upper dose limit therefore needs to be imposed as long as food is irradiated based on prevailing good manufacturing practices. The safety of irradiated foods is also supported by data on extensive experience with laboratory animal diets that had been sterilized by irradiation. Over the past few decades, millions of laboratory animals including rats, mice and other species have been bred and reared exclusively on radiation-sterilized diets. Several generations of these animals were fed diets irradiated with doses ranging from 25 to 50 kGy. The studies took place in laboratories in several countries-Austria, Australia, Canada, France, Germany, Japan, Switzerland, the UK and the USA. No transmittable genetic defects-teratogenic or oncogenic-have been observed that could be attributed to the consumption of irradiated diets.
Would food irradiation facilities endanger local communities?
No. Irradiation facilities are safe for local communities. A food irradiation plant wouldnot endanger a community. It would be no different from the approximately 40 medical-products irradiation sterilization plants and the more than 1,000 hospital radiation-therapy units using cobalt-60 as radiation sources, as well as the hundreds of industrial electron irradiation facilities used for different purposes, now operating in the United States. None of these facilities has been found to pose a danger to the surrounding community. To be sure, a food irradiation facility must be designed, constructed and operated properly, as well as duly licensed by national or state authorities. This does not represent a new challenge, since the necessary safety precautions are well understood. They have long been applied in the design, construction and maintenance of similar types of irradiation facilities used for other purposes over the past 50 years.
Could there be a "meltdown" in a food irradiation facility?
No. It is impossible for a "meltdown" to occur in a food irradiation plant or for a radiation source to explode. The radioisotopic sources approved for food irradiation, i.e., cobalt-60 and cesium-137, cannot produce the neutrons that can make materials radioactive, so no ?nuclear chain reaction? can occur at such an irradiation facility. Food irradiation plants contain shielded chambers within which the foods are exposed to a source of ionizing radiation. The radiation sources used in food irradiation cannot overheat, explode, leak or release radioactivity into the environment.
Would workers in a food irradiation plant be exposed to hazardous radiation?
No. Irradiation facilities, including those used for food irradiation, are designed with several levels of safety redundancy to detect equipment malfunction and to protect personnel from accidental radiation exposure. All irradiation facilities must be licensed by national or state authorities to ensure their safety for the workers as well as for the environment. Regulations in all countries require such facilities to be inspected periodically to ensure compliance with the terms of the operating licenses. As a result of long experience in designing and operating similar types of irradiation facilities, the necessary precautions for worker safety in a food irradiation plant are well understood. In the U.S., the Occupational Safety and Health Administration (OSHA) is responsible for regulating worker protection from all sources of ionizing radiation. Food irradiation plants that use cobalt or cesium as their radiation source must be licensed by the NRC or an appropriate state agency. The NRC is responsible for the safety of workers in facilities it has licensed. Plants in the United States that use machine-generated radiation are under the jurisdiction of state agencies, which have established appropriate performance standards to ensure worker safety.
Is irradiating food a means of using radioactive wastes?
No. Spent fuel from nuclear reactors (radioactive waste) is not used in any food or industrial irradiation facilities. Of the four possible radiation sources for use in food irradiation, only one?cesium?is a byproduct of nuclear fission. It is of limited commercial availability and is not used in any industrial irradiation facility. Cobalt-60, the most commonly used radioactive source for industrial radiation processing-including food irradiation-has to be manufactured specifically for this purpose; hence it is not a "nuclear waste" product. Cobalt-60 is produced by activating cobalt-59, a non-radioactive metal, in a nuclear reactor to absorb neutrons and change its characteristics to cobalt-60, which is radioactive and generates gamma rays. Canada is the largest producer of cobalt-60, representing about 75% of world production. The remaining producers are in France, Argentina, Russia, China and India. Cobalt-60 suppliers can in principle reactivate used cobalt-60 sources, if required, thus effectively recycling them. Food irradiation does not use radioactive wastes. Electrically generated electron beam and X-ray machines have been designed and used for irradiating food in the United States, especially for ensuring microbiological safety of ground beef and meeting the quarantine requirements for tropical fruits. When such machines, which use electricity as power sources, are used for irradiating food, there is neither radioactivity nor radioactive materials involved.
How can we be sure that foods are properly irradiated?
The effectiveness of a specific application of irradiation on food must be verified by the FDA and USDA. When these agencies approve specific applications of food irradiation, they require that food be irradiated in facilities licensed for this purpose. These facilities also must use correct radiation doses as required by law, according to good manufacturing practices (GMPs) and as part of an overall HACCP plan. These guidelines emphasize that, as with all food technologies, effective quality control systems need to be established and closely monitored at critical control points at the irradiation facility. In all cases, only food of high quality should be accepted for irradiation. As with other technologies, irradiation cannot be used as a substitute for poor hygienic practices or to reverse spoilage.