The food industry employs several methods to preserve food and food quality. Among these is irradiation. This process was developed by the US army after the second world war as the army researched new ways to preserve foods for troops beyond refrigeration. The word irradiation often concoct feelings of fear of nuclear energy. Many feel that it may cause foods to become radioactive, producing damaging health effects, however this fear is usually overblown. Irradiation is a form of radiation utilizing high energy electromagnetic waves. These may be gamma or X-rays, although gamma rays are more common. These rays are effective in food preservation due to their shorter wavelengths which are capable of causing “ionizing effects” resulting in damage to molecular structures in bacteria, fungus and insects.

Electromagnetic Spectrum (Source: https://www.miniphysics.com/electromagnetic-spectrum_25.html)

Effect of Radiation on Foods

Irradiation can sterilize foods, however sterilization is not often done since the high dosage levels required can cause unacceptable organoleptic changes. Therefore, foods that are irradiated may still contain a considerable number of microorganisms although much lower than untreated foods. With this in mind, precautions such as proper handling and cooking is still necessary to ensure food safety when the products are eaten. It’s important to note that radiation at the levels that are generally applied do not induce radioactivity in food. Radiolytic products (by-products of irradiation) are generally lost quickly, causing no adverse effect. However, there are still some concerns. For example, one European study showed that 2-alkylcyclobutanones was produced in ground beef, which acted as a tumor promoter in laboratory rats. Another concern is that nutritional value and sensory properties may be affected at high doses. For example, amino acids may be modified, causing changes to flavor. Carbohydrates such as pectins, starches and gums may be hydrolyzed, causing changes in texture. Lipids are generally oxidized to form hydroperoxides due to reaction with free radicals. This typically leads to unacceptable flavor and odor. Oxidation of myoglobin pigment in meats can lead to discoloration. Vitamin B content, particularly thiamin (B1) may be reduce slightly as it is the most sensitive of the B vitamins. In general however, irradiation at the dosage levels used to achieve technological effects in foods, does not produce any more adverse effect than is observed using traditional methods of preservation.

Labeling

Based on the Food Additives Amendment Act (1958), the process of irradiation is considered a food additive. Irradiated foods sold to stores are required to carry the statement “treated with radiation” or treated by radiation” and include the Radura symbol. Wholesale foods sold to processors are required to be labelled with the statement “Treated by irradiation, do not irradiate again”. Congress has mandated that the FDA cannot require the irradiation label statement to be larger than that required for ingredients. The FDA responded by requiring that irradiation labeling be “prominent and conspicuous” but have clarified that this does not mean that the print be larger than the usual type size. Foods approved for irradiation by the FDA is based on a petition process. In considering approval, the FDA evaluates technological safety, microbiological safety, and nutritional adequacy.

Benefits of Irradiation

  1. Improve microbial safety
  2. Eliminate need for fumigation with chemicals that could leave potentially harmful residues e.g. ethylene dibromide, ethylene dichloride, ethylene oxide, methyl bromide
  3. Little or no heating and therefore negligible effect on organoleptic properties

Concerns and Arguments

  1. Negative public perception on the use of nuclear technology in food
  2. Lack of long-term studies on the effects of radiolytic compounds and their potential to cause cancer and other illnesses
  3. Processors may have more incentive to use irradiation as a replacement for good agricultural practices and good manufacturing practices
  4. The process does not destroy toxins if the food is treated after the toxins are made
  5. The process is not very effective against viruses and prions (the infectious protein that causes mad cow disease)
  6. The process can create an occupational hazard in case of an accident considering that a typical dosage of 1.5 KGy is 150 times the dosage that is capable of killing an adult
Courtney Simons
Administrator
Courtney Simons is a food science professor. He holds a BS degree in food science and a PhD in cereal science from North Dakota State University.
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