Irradiating Dinner

Understanding Irradiation

Exposure of foods to X-rays and other forms of ionizing radiation kills the molds, bacteria, and insects that cause spoilage. It delays the ripening of fruits and berries, so extends shelf life. In addition, irradiation inhibits the sprouting of potatoes and other foods, which means that they stay fresh longer. Previously, heat and the use of chemicals (formaldehyde, alcohol, or various pesticides) were the major methods of sterilization, but each had its drawbacks. Heat sterilization entails cooking foods, so they are no longer fresh; chemicals that kill bacteria and other microorganisms often make foods inedible. Irradiation would seem to be an ideal means of sterilization, but the public has been slow to accept it.

Radioactive Foods?

Despite assurances that irradiation with X-rays or certain isotopes does not make foods radioactive, some consumer and environmental groups remain unconvinced. They worry that any radiation exposure poses a potential environmental hazard, even if the foods themselves are not made radioactive. They also fear the radiation may foster the development of dangerous mutant organisms or “unique radiolytic products.” The latter refer to compounds such as 2-alkylcyclobutanones, which form when animal fat is irradiated. Some studies have shown that such compounds can cause strand breaks in DNA, which raises the prospect of cancer.

An Intimate Look at Irradiation

The benefits of irradiation greatly outweigh the risks. There are roughly 50 million cases of food-borne illness in North America every year and a large number of these are caused by E. coli and salmonella, which could be controlled by irradiation. Foods such as wheat, flour, potatoes, and spices have been irradiated in many countries for decades without any link to harmful effects.

The government mandates that only certain forms of irradiation can be applied to foods to ensure that they don’t absorb the radioactive material. X-rays, which pass through an object without leaving behind radioactive material, and exposure to certain cobalt and cesium isotopes are all acceptable methods. These methods of cold sterilization allow most irradiated foods to retain their fresh appearance and taste. When meat, fish, and seafood are exposed to the high doses of radiation needed to destroy parasites, salmonella bacteria, and other organisms, however, the flesh of some meat may darken, and fish and seafood may become mushy. Irradiation can also oxidize the fats in whole grains, causing them to taste rancid.

Beneficial Effects

In general, irradiation preserves more nutrients—particularly niacin, riboflavin, thiamine, and other B-group vitamins—than other sterilization methods do. But very high radiation doses, such as those needed to sterilize meat, will destroy some of the fat-soluble vitamins A, E, and K. The effects of irradiation on vitamin C remain unknown; some studies show no loss of this nutrient, while others indicate major losses.

Food irradiation adds an extra measure of food safety for AIDS patients and others with lowered immunity; these people are cautioned not to eat uncooked fruits and vegetables and to make sure that all meat, fish, eggs, and other foods that may harbor disease-causing bacteria or parasites are cooked until well-done. Even after these precautions are taken, food-borne diseases are a major hazard for people with compromised immunity. High-dose irradiation can eliminate these dangers.