Radiation is a bad thing that we don’t want to be exposed to, or so the conventional wisdom goes. We’re most familiar with it in the context of industrial risks and the stories of nuclear disasters that threaten entire cities and contaminate local food chains. It’s certainly not something you’d want anywhere near your dinner, right?You might then be surprised to find that a great deal of research has been conducted into the process of food irradiation. It’s actually intended to ensure food is safer for human consumption, and has become widely used around the world.Drop It Like It’s HotFood irradiation might sound like a process from an old science fiction movie, but it has a very real and very useful purpose. It’s a reliable way to eliminate pathogens and extend shelf life, with only a few specific drawbacks. Despite being approved by health organizations worldwide and used commercially since the 1950s, it remains one of the most misunderstood technologies in our food system.The basic concept is simple—radiation can kill pathogens while leaving the food unharmed. Credit: IAEAThe fundamental concept behind food irradiation is simple. Food is exposed to ionizing radiation in controlled doses in order to disrupt the DNA of harmful microorganisms, parasites, and insects. The method is both useful in single serving contexts, such as individual meal rations, as well as in bulk contexts, such as shipping large quantities of wheat. Irradiation can outright kill bacteria in food that’s intended for human consumption, or leave pests unable to reproduce, ensuring a shipment of grain doesn’t carry harmful insects across national borders.It’s important to note that food irradiation doesn’t make the food itself radioactive. This process doesn’t make food radioactive any more than a chest X-ray makes your body radioactive, since the energy levels involved simply aren’t high enough. The radiation passes through the food, breaking the chemical bonds that make up the genetic material of unwanted organisms. It effectively sterilizes or kills them, ideally without significantly changing the food itself. It also can be used to reduce sprouting of some species like potatoes or onions, and also delay ripening of fruits post-harvest, thanks to its effect on microbes and enzymes that influence these processes.The concept of food irradiation dates back a long way, far beyond what we would typically call the nuclear age. At the dawn of the 20th century, there was some interest in using then-novel X-rays to deal with pests in food and aid with preservation. A handful of patents were issued, though these had little impact outside the academic realm.It was only in the years after World War II that things really kicked off in earnest, with the US Army in particular investing a great deal of money to investigate the potential benefits of food irradiation (also known as radurization). With the aid of modern, potent sources of radiation, studies were undertaken at laboratories at the Quartermaster Food and Container Institute, and later at the Natick R&D Command. Much early research focused on meats—specifically beef, poultry, and pork products. A technique was developed which involved cooking food, portioning it, and sealing it in vacuum packs. It would then be frozen and irradiated at a set minimum dose. This process was developed to the point that refrigeration became unnecessary in some cases, and avoided the need to use potentially harmful chemical preservatives in food. These were all highly desirable attributes which promised to improve military logistics.Food irradiation eventually spread beyond research and into the mainstream.The technology would eventually spread beyond military research. By the late 1950s, a German effort was irradiating spices at a commercial level. By 1985, the US Food and Drug Administration had approved irradiation of pork, which became a key target for radurization in order to deal with trichinosis parasites. In time, commercialized methods would be approved in a number of countries to control insects in fruits, vegetables, and bulk foods like legumes and grain, and to prevent sprouting during transport. NASA even began using irradiated foods for space missions in the 1970s, recognizing that traditional food preservation methods aren’t always practical when you’re orbiting Earth. This space-age application highlights one of irradiation’s key advantages—it works without chemicals and eliminates the need for ongoing refrigeration to avoid spoilage. That’s a huge benefit for space missions which can save a great deal of weight by not taking a fridge with them. It also helps astronauts avoid foodborne illnesses, which are incredibly impractical in the confines of a spaceship. Irradiated food has also been used in hospitals to protect immune-compromised patients from another potential source of infection.How It’s DoneA truck-mounted food irradiator, used in a demonstration tour around the United States in the late 1960s. Credit: US Department of EnergyThree main types of radiation are used commercially to treat food. Gamma rays from cobalt-60 or cesium-137 sources penetrate deeply into food, and it’s possible to use these isotopes to produce uniform and controlled doses of radiation. Cobalt-60 is more commonly used, as it is easier to obtain and can be used with less risks. Isotope sources can’t be switched “off,” so are stored in water pools when not in use to absorb their radiation output. Electron beams, generated by linear accelerators, offer precise control of dosage, but have limited penetration depth into food, limiting their use cases to specific foods. X-rays, produced when high-energy electrons strike a metal target, combine the benefits of both gamma rays and electron beams. They have excellent penetration and can be easily controlled by switching the X-ray source on and off. The choice depends on the specific application, with factors like food density, package size, and required dose uniformity all playing roles. Whatever method is used, there’s generally no real risk of food becoming irradiated. That’s because the X-rays, electron beams, and gamma rays used for irradiation are all below the energy levels that would be required to actually impact the nucleus of the atoms in the food. Instead, they’re only strong enough to break chemical bonds. It is thus important to ensure the irradiation process does not cause harmful changes in whatever material the food is stored in; much research has gone into finding safe materials that are compatible with the irradiation process. A chamber used for gamma ray food irradiation with cobalt-60. Credit: SwimmaajThe dosage levels used in food irradiation are carefully calibrated and measured in units in Grays (Gy) or more typically, kiloGrays (kGy). Low doses of 0.1 to 1 kGy can inhibit sprouting in potatoes and onions or delay ripening in fruits. Medium doses of 1 to 10 kGy eliminate insects and reduce pathogenic bacteria. High doses above 10 kGy can sterilize foods for long-term storage or for space-or hospital-based use, though these doses are not as widely used for commercial food products. By and large, irradiation does not have a major effect on a food’s taste, appearance, or texture. Studies have shown that irradiation can cause some minor changes to food’s nutritional content, as noted by the World Health Organization. However, while irradiation can highly degrade vitamins in a pure solution, in food items, losses are typically on the order of a few percent at most. The losses are often comparable to or less than those from traditional processing methods like canning or freezing. Changes to carbohydrates, proteins, and lipids are usually very limited. The US FDA, World Health Organization, and similar authorities in many countries have approved food irradiation in many contexts, with studies bearing out its overall safety. The Radura logo is used to mark foods that have been treated with irradiation. Credit: US FDAIn some extreme cases, though, irradiation can cause problems. In 2008, Orijen cat foods were recalled in Australia after the irradiated product was found to be causing illness in cats. This was not a result of any radioactive byproduct. Instead, the issue was that the high dose (>50 kGy) of radiation used had depleted vitamin A content in the food. Since pets are often fed a very limited diet, this led to nutrient deficiencies and the unfortunate deaths of a number of animals prior to being recalled.The regulatory landscape varies significantly worldwide, both in dose levels and in labelling. While the United States allows irradiation of various foods including spices, fruits, vegetables, grains, and meats, rules mandate that irradiated products are clearly identified. The distinctive radura symbol—a stylized flower in a circle—must appear alongside text stating “treated with radiation” or “treated by irradiation.” Some countries have embraced the technology more fully; others less so. EU countries primarily allow radiation treatments for herbs and spices only, while in Brazil, just about any food may be irradiated to whatever dose deemed necessary, though doses above 10 kGy should have a legitimate technological purpose.Overall, food irradiation is a a scary-sounding technology that actually makes food a lot safer. It’s not something we think about on the regular, but it has become an important part of the international food supply nonetheless. Where there are pests to prevent and pathogens to quash, irradiation can prove a useful tool to preserve the quality of food and protect those that eat it.