Food Irradiation

Latest assesments estimate that every year there are 76 million cases of foodborne illness in the USA alone. As many as 5,000 of these result in death. Children, unborn babies and  the elderly are at greatest risk.

What is Food Irradiation?

Food irradiation describes the process of using ionising radiation to kill harmful micro-organisms responsible for food borne illness and to reduce food spoilage from sprouting and mildew development. Radiation can also be used to eradicate quarantine pests from bulk export crops, such as fruit fly in tropical fruits. The radiation used can be gamma, x-ray or a stream of electrons travelling at almost the speed of light, an electron beam (E-beam). These are all sources of high energy and act in exactly the same way to destroy bacteria by ionisation. The purpose of food irradiation is not to sterilize the product but to reduce the number of harmful micro-organisms (reduce the bio-burden) to a level that is no longer a threat to the consumer. This is the principle of pasteurization applied to milk using heat (infrared radiation) as the energy source. As a result, treatment of food with non-thermal radiation is sometimes referred to as "Cold Pasteurization" or "Electronic Pasteurization", when E-beam is used as the energy source.

What are the benefits of Food Irradiation?

Radiation is highly penetrating. Food can be treated in its final packaging to ensure that it is free from harmful bacterial when it leaves the producer. This is a valuable insurance for both the producer and the consumer. In this way the likelihood of cross contamination of raw foods such as salads and fruit from high risk foods such as chicken, shellfish and ground beef during preparation in the home is reduced and the likelihood of food borne illness diminished.

Unlike chemical fumigation, radiation does not leave any chemical residues on the product and changes in the chemical composition of irradiated food are so small that using even the most sensitive instrumentation they are almost immeasurable.

The most common chemical fumigant, methyl bromide, attacks the ozone layer. Radiation is an environmentally cleaner process with much lower health risks for the operator.

Unlike thermal methods radiation has only a small impact on the taste, appearance and nutritional value of fresh fruits and vegetables. Even at doses far in excess of those needed to achieve the objective, radiation causes less than 10% vitamin loss in fresh fruits and vegetables and no loss in proteins, fats, carbohydrates or minerals in meats.

Is it safe?

Gamma irradiation is probably the most exhaustively researched food processing method ever proposed. In the scientific and medical professions it has gained global regulatory acceptance as one of the safest and most effective known methods of food pasteurisation.

Is it an excuse to allow food production standards to fall?

Irradiation is an expensive process. To keep costs low the product should be as clean as possible. The higher the product bio-burden the higher is the cost of irradiation and the greater is the detrimental impact on the sensory qualities of the food, colour, taste and smell. Irradiation will not clean-up toxins that develop as a result of well established bacterial contamination. This food will never be fit to eat. In this way irradiation is a self-limiting process. It should be used as a critical control in hazard analysis critical control point (HACCP) procedures and regarded as a belt and braces approach in the processing of high risk foods like chicken, ground beef, shellfish, blood products, unpasteurised cheeses and ready-to-eat-meats.

What foods are currently irradiated?

Not just any food product can be irradiated and sold. The US Department of Agriculture (USDA) and the Food and Drug Administration (FDA) in the USA, and the Health and Consumer Protection Directorate of the European Commission in Europe have to approve the product for irradiation at specific maximum and minimum doses. The irradiation facility used to treat the food must apply for a licence. In the UK there are currently seven categories of food approved for treatment by radiation but only one irradiation plant is licensed to treat food, specifically spices. France, Belgium and Holland irradiate a wider range of food products including mechanically de-boned chicken, shell fish, frogs legs, blood products, unpasteurised cheese and egg products. However, growth in the use of irradiation in the UK and Europe is static. In the USA the use of irradiation is growing. It is used to combat E-coli in hamburger meat and salmonella in chicken and as a quarantine treatment against fruit fly in tropical fruits (papaya and mangos) imported from Hawaii.

How do we know when a product has been irradiated?

Coloured labels that are sensitive to radiation change colour after irradiation are sometimes used as visual indicators. A strictly regulated process of dosimetry is used to measure the exact dose of radiation absorbed by the product. This is achieved by the use of radiation monitors that are irradiated with the product and measured against a national calibration standard to prove the appropriate dose has been delivered before the product may be released for use. Proof of treatment is traceable and archived for up to seven years after the product has been released. Irradiated food products are legally required to show the internationally recognised radura alongside a statement "Treated with Radiation". The regulations governing the labelling of food that contains small quantities of irradiated ingredients such as seasonings varies from country to country.