Irradiation refers to the exposure of a substance to radiation from a variety different sources. Radiation can be ionizing or non-ionizing, referring to either purposeful versus natural sources of radiation, respectively. Some examples of ionizing radiationinclude electronics, visible and infrared light, microwaves, and electromagnetic waves (e.g., radio waves, power, and electronic receivers). Irradiation is used for several purposes, with food sterilization (using X-rays or gamma rays) and medical imaging (using a radioactive dye for diagnostic imaging) being some of the most popular applications of ionizing radiation. Food irradiation does not involvecontact with the product exposed to radiation, and does not result in radioactive products.
Food irradiation (the application of ionizing radiation to food) is a technology that improves the safety and extends the shelf life of foods by reducing or eliminating microorganisms and insects. Like pasteurizing milk and canning fruits and vegetables, irradiation can make food safer for the consumer. The Food and Drug Administration (FDA) is responsible for regulating the sources of radiation that are used to irradiate food. The FDA approves a source of radiation for use on foods only after it has determined that irradiating the food is safe. Agrilearner
Irradiation can serve many purposes.
Prevention of Foodborne Illness – to effectively eliminate organisms that cause foodborne illness, such asSalmonella and Escherichia coli (E. coli).Preservation – to destroy or inactivate organisms that cause spoilage and decomposition and extend the shelf life of foods.Control of Insects – to destroy insects in or on tropical fruits imported into the United States. Irradiation also decreases the need for other pest-control practices that may harm the fruit.Delay of Sprouting and Ripening – to inhibit sprouting (e.g., potatoes) and delay ripening of fruit to increase longevity.Sterilization – irradiation can be used to sterilize foods, which can then be stored for years without refrigeration. Sterilized foods are useful in hospitals for patients with severely impaired immune systems, such as patients with AIDS or undergoing chemotherapy. Foods that are sterilized by irradiation are exposed to substantially higher levels of treatment than those approved for general use.
Irradiation for Agricultural Applications
There are three types of ionizing radiation that can potentially be used in food irradiation: electron beams (machine generated), X-rays – (machine generated), andgamma rays (occur naturally from radioactive decay of Cesium 137 or Cobalt 60).
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, andbacteria) 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.
Another form of food irradiation is electron radiation, which involves the use of electron streams traveling close to the speed of light induced by radio waves or other electronic sources. However, while this method is safer compared to the use of X-rays and gamma radiation, electrons do not penetrate the food products as deeply and cannot be applied to an entire food pallet, which can be achieved with gamma radiation.
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