Food is irradiated for many reasons including reducing the risk of food-borne illnesses, extending shelf-life, controlling insects and invasive pests, sterilization, and delaying or stopping the sprouting or ripening of food. Just like pasteurizing milk or canning food, irradiating food makes it safer for the consumer.
Radiation kills disease-causing organisms such as Salmonella and Escherichia coli and microorganisms that cause food spoilage and decomposition. Using radiation also kills insects that may be inadvertently introduced into countries, eliminating the need for pesticides or other pest control measures that may be harmful. Potatoes are irradiated to prevent them sprouting and irradiating fruits delays ripening. Both treatments increase the shelf life of the foods. Higher levels of radiation sterilize food so it can be stored for years without refrigeration.
How the Process Works
Food is irradiated using gamma rays, X-rays, and electron beams. Depending on how deep the radiation penetrates, entire palettes of food can be irradiated at once or just a single layer at a time.
Gamma rays come from the elements cobalt and cesium and penetrate farther into substances than electron beams. In addition to their use on food, gamma rays are used to in cancer treatment and to sterilize medical and dental equipment.
X-rays are usually equated with the medical industry, but they are also effective for irradiating food. A stream of high-energy electrons is reflected off a metallic substance like tungsten or tantalum and directed so they pass through the food. The penetration of X-rays is similar to gamma rays, but X-rays require more energy, yet they are easier to control and can be applied more uniformly.
To irradiate food using an electron beam, a stream of electrons is accelerated until it is traveling close to the speed of light and directed at the food. The electrons kill microorganisms by damaging and causing breaks in the DNA and RNA.
In food processing, irradiation is measured in units called grays (Gy). A kilogray (kGy) is equal to 103 grays. Low doses up to 1.00 kGy are used for inhibiting sprouting of potatoes and delaying fruit ripening. To delay the spoilage of meat, reducing the risk of disease-causing microorganisms in meat, and sanitizing spices, medium doses ranging from 1.00 kGy to 10 kGy are used. Finally, high doses of up to 70 kGy sterilize meat.
Is Irradiated Food Safe to Eat?
Irradiating food does not make it radioactive, change the quality of the food, or noticeably alter its taste, appearance, or texture. The US Food and Drug Administration (FDA), US Centers for Disease Control and Prevention (CDC), US Department of Agriculture (USDA), and the World Health Organization (WHO) have determined that irradiated food is safe. Hundreds of animal feeding studies have been conducted since the 1950s and this information has helped these agencies make their decision to endorse food irradiation.
Food Irradiation Laws in the US and EU
Over 500,000 metric tons of food are irradiated each year in over 60 countries around the world. The regulations for irradiating and which foods are allowed to be irradiated vary greatly. For example, Brazil allows irradiation of all foods at any dose while Germany and Austria only allow irradiated dried spices, herbs, and seasonings at a specific dose.
In the United States, irradiation is considered a food additive, not a process, and there are specific requirements for disclosing it on food packaging. Along with the statement “Treated with radiation” or “Treated by irradiation,” foods must display the Radura symbol on the package (see image below). If an irradiated ingredient is used in another product, it must be disclosed in the ingredients but the Radura symbol is not required. In addition, restaurants in the US are not required to disclose the use of irradiated ingredients to their customers.
Food in the European Union (EU) is regulated as a single market, meaning there are few trade barriers and some regulations cover all the countries. Irradiated food falls into this category, so any irradiated food can be marketed anywhere in the EU, even if countries have banned it on their own. EU law says that before a food can be added to the list of approved radiated foods, it must undergo toxicology testing. Also, irradiated foods can be imported into the EU providing the irradiating facility has been inspected and approved by the European Community (EC).
The image above is the Radura international symbol for irradiation. The US FDA requires all irradiated foods to bear the symbol.
References
- Consumers – Food Irradiation: What You Need to Know. (n.d.). [WebContent]. Retrieved May 3, 2018, from https://www.fda.gov/food/resourcesforyou/consumers/ucm261680.htm
- Food irradiation. (2018, April 28). In Wikipedia. Retrieved from https://en.wikipedia.org/w/index.php?title=Food_irradiation&oldid=838713415