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 Nuclear Science and Technology
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Food : Benefits / Effects

The effects of irradiation on food, and on animals and people eating irradiated food, have been studied extensively for more than 40 years.  These studies show clearly that when irradiation is used as approved on foods, it benefits food producers, manufacturers and consumers, because:
  1. Disease-causing microorganisms are reduced or eliminated -- It can kill many insects and pests that infest foods like grains, herbs, and spices.  It can kill or substantially reduce the level of dangerous micro-organisms in foods such as salmonella, listeria, and campylobacter.  It can delay or stop normal ripening and decay processes so that foods can be stored longer.  It can completely sterilize a food, making it fit to eat for vulnerable patients in hospitals.

  2. The nutritional value is essentially unchanged -- Macro-nutrients, such as protein, carbohydrates, and fat, are relatively stable to radiation doses of up to 10 kiloGrays.  Micro-nutrients, especially vitamins, may be sensitive to any food processing method, including irradiation (e.g. vitamin E levels can be reduced by 25% after irradiation and vitamin C by 5-10%).  Under optimal conditions, vitamin losses in foods irradiated at doses up to 1 kiloGray are considered to be insignificant.  At higher doses the change in nutritional value caused by irradiation depends on a number of factors.  They include the specific vitamin, the radiation dose to which the food has been exposed, the type of food, the packaging, and the processing conditions, such as temperature during irradiation and storage time.  Most of these factors are also true for other food preservation technologies.&nspb; For example measurement of vitamin C content in three varieties of apples kept in cold storage for up to 1 year showed decreases of between 40% to 70%, depending on the variety of apple.  Just as vitamins vary in their sensitivity to heat, so do they vary in their sensitivity to radiation.

  3. No harmful chemical changes -- In general, the irradiation process produces very little chemical change in food.  None of the changes known to occur have been found to be harmful or dangerous.  Some of the chemical changes produce so-called "radiolytic" products.  These products have proven to be familiar ones, such as glucose, formic acid, acetaldehyde, and carbon dioxide, which are naturally present in foods or are formed by heat processing.  The safety of these radiolytic products has been examined very critically, and even though there is some controversy over whether these products are unique and if so whether they are dangerous, no evidence of their harmfulness has been found.  The FDA has estimated that the total amount of undetected radiolytic products that might be formed when food is irradiated at a dose of 1 kiloGray would be less than 3 milligrams per kilogram of food -- or less than 3 parts per million.

  4. The appearance of the food is unchanged -- The level of energy used for food irradiation affects only live organisms such as bacteria, insects, and protozoa that may be present.  Because harvested meat is no longer "living", there is very little effect on the meat's appearance, taste, or nutritive value.

  5. The food does not become radioactive -- Irradiation under controlled conditions does not make food radioactive.  The irradiation process involves passing the food through a radiation field at a set speed to control the amount of energy or dose absorbed by the food.  The food itself never comes into direct contact with the radiation source.  Even when foods are exposed to very high doses of radiation from these sources, the maximum level of induced radioactivity would be just 1/1000 (one thousandth) of a becquerel per kilogram of food.  This is 200,000 times smaller than the level of radioactivity naturally present in food, because everything in our environment, including food, already contains trace amounts (about 150 to 200 becquerels) of natural radioactivity.

However, this does not mean that food irradiation is the "ultimate solution" for all food problems.  There are some limitations:
  1. It can be used only on a limited range of foods -- Fresh fruits (papaya, citrus, apples, strawberries, lychee, rambutan, cherimoya, tomatoes); spices and dried vegetables; frog legs; onions and garlic; chicken; fermented pork sausages; dried fish; and red meat.  The limitation on foods that can be irradiated is a political, not a technical issue, and depends on approval for different organizations.

  2. It is still a relatively expensive technology -- Broken down, irradiation costs range from US $10 to $15 per ton for a low-dose application, up to US $100 to $250 per ton for a high-dose application.  These costs are competitive with alternative treatments such as canning, freezing, pasteurization, refrigeration, and fumigation.  In some cases, irradiation can be considerably less expensive.  For disinfestation of fruit in Thailand and the United States, for example, it has been estimated that the cost of irradiation would be only 10%-20% of the cost of vapor-heat treatment.  The cost to build a commercial food irradiation plant is in the range of US $4 million to $10 million, depending on its size, processing capacity (respectively 15 to 250 + million pounds per year throughput capacity), and other factors.

  3. Radiation doses at the levels recommended will not kill all micro-organisms -- Typically 90% may be destroyed; this means that the food still has be treated with care, otherwise the remaining organisms will reproduce rapidly.