Last updated on 26 April 2012
Irradiation can be used to kill bacteria that cause food poisoning, such as salmonella, campylobacter and E.coli. It can also delay fruit ripening and help stop vegetables such as potatoes and onions from sprouting.
Food irradiation is a processing technique that exposes food to electron beams, X-rays or gamma rays. The process produces a similar effect to pasteurisation, cooking or other forms of heat treatment, but with less effect on look and texture. Irradiated food has been exposed to radioactivity but does not become radioactive itself.
Food absorbs energy when it is exposed to ionising radiation. The amount of energy absorbed is called 'absorbed dose', which is measured in units called grays (Gy) or kilograys (kGy), where 1kGy = 1,000Gy. The energy absorbed by the food causes the formation of short-lived molecules known as free radicals, which kill bacteria that cause food poisoning. They can also delay fruit ripening and help stop vegetables, such as potatoes and onions, from sprouting.
Decades of research worldwide have shown that irradiation of food is a safe and effective way to kill bacteria in foods and extend its shelf life. Food irradiation has been examined thoroughly by joint committees of the World Health Organization (WHO), the United Nations Food and Agriculture Organization (FAO), by the European Community Scientific Committee for Food, the United States Food and Drug Administration and by a House of Lords committee. In 2011, the European Food Safety Authority reviewed the evidence and reasserted the opinion that food irradiation is safe.
All food preservation techniques cause chemical changes in food – that is how they work. The changes caused by food irradiation (for example the production of free radicals) are similar in nature and extent to those caused by other preservation techniques, such as cooking, canning and pasteurisation. There may be some vitamin loss but this would occur with any other preservation technique or even just long-term storage. There is no evidence that any of the changes caused by food irradiation pose a risk to the health of consumers.
The law covering food irradiation states that irradiation can only be used where it is of benefit to the consumer. A company that wants to irradiate a food product, has to be able to show that the benefits of irradiation (for example reducing the risk of foodborne illness) outweigh any negative aspects (for example the loss of some vitamins). This will vary between different foods and means that the use of food irradiation is more suitable to some foods than others.
The European Commission has agreed a list of irradiated foods that can be freely traded across the European Union (EU). The list is not complete and at present it has only one food group: dried aromatic herbs, spices and vegetable seasonings. Until this list is complete, EU member states may continue to allow the irradiation of additional categories of foods.
In the UK there are seven categories of food which may be irradiated. For each category of food the 'maximum overall average dose' that can be used is specified in units of kilograys (kGy):
- fruit, 2kGy
- vegetables, 1kGy
- cereals, 1kGy
- bulbs and tubers, 0.2kGy
- dried aromatic herbs, spices and vegetable seasonings, 10kGy
- fish and shellfish, 3kGy
- poultry, 7kGy
These categories of food can also be irradiated and used as ingredients in other food products.
Certain foods that have been irradiated may be imported into the UK, as long as they comply with certain rules. The Food Irradiation (England) Regulations 2009 set out the requirements for producing, importing and selling irradiated food in the UK. The food must come from an approved facility and must have the correct documentation to accompany it. There is also parallel legislation in Wales, Northern Ireland and Scotland.
See the link below for more information about the importation of irradiated foods.
The Food Irradiation Regulations allow for four methods of irradiation which are as follows:
- gamma rays from the radionuclide cobolt-60
- gamma rays from the radionuclide caesium-137
- X-rays generated from machine sources operated at or below an energy level of 5MeV
- electrons generated from machine sources operated at or below an energy level of 10MeV
Foods are irradiated in authorised irradiation facilities which must be regulated and subjected to strict safety inspections.
There is currently one licensed food irradiation facility in the UK. There are more than 20 facilities in other European Union (EU) member states and ten outside the EU (three in South Africa and India, two in Thailand and one each in Turkey and Switzerland). Only facilities approved by the EU can import these foods to the UK.
All foods which have been irradiated must be labelled as 'irradiated' or 'treated with ionising radiation'. Where an irradiated food is used as an ingredient in another food, the words 'irradiated' or 'treated with ionising radiation' should appear next to the ingredient in the list of ingredients.
When irradiated food is not pre-packed these same words shall appear together with the name of the product on a display or notice above or besides the container in which the products are placed.
There are 10 European Committee for Standardisation (CEN) standard tests validated for the detection of different irradiated foods, including herbs and spices, poultry and meat containing bone and products containing fats.
Local authority trading standards officers carry out checks to ensure any mislabelled products are discovered. These results are provided to the European Commission and the results published in annual reports.
Yes, it is. X-ray scanners used at airports for baggage control operate at very much lower energy and give rise to radiation levels very much lower than radiation sources used in food irradiation facilities. The radiation doses used to process food can be as high as 10,000 gray, whilst X-ray scanners operate at less than 0.5 gray. It is very difficult, if not impossible, to detect changes to food once it has been through an X-ray scanner.
In fact many of these X-ray machines (at airports for example) operate at such a low dose that they don't affect photographic film.
If you are storing or transporting irradiated food for the purpose of sale, then you must ensure that the correct documentation accompanies the food up until the point it is sold to the ultimate consumer or caterer. This should include information about how and where the food was irradiated, which will be supplied by the irradiation facility.