Food irradiation
Food irradiation is a food preservation process and a quarantine measure. Food processors use it to destroy bacteria that cause food decomposition and food poisoning. Those bacteria include the parasites, moulds and yeasts that spoil food, and salmonella and campylobacter that cause illness.
Food can only be irradiated if there is no other safe method available. Any irradiated food must go through a strict safety assessment by Food Standards Australia New Zealand and, if approved, must be labelled as having been treated by radiation.
To date, in Australia and New Zealand, only herbs and spices, herbal teas and some tropical fruits have been approved to be irradiated.
Food irradiation is a food processing technology that exposes food to a source of ionising energy to purify it. Under the Food Standard covering the irradiation of food in Australia and New Zealand, this energy can be in the form of gamma rays from Cobalt 60, machine generated X-rays, or an electrically generated electron beam.
Food processors also use more traditional preservation methods to achieve the same effect, including drying, smoking, salting, curing, canning, freezing or pasteurisation. These processes keep food safe to eat by delaying the natural decomposition processes that result from bacterial action.
Processors use different preservation techniques with different types and forms of food. For example, they may use irradiation to treat herbs and spices in place of chemical treatments. Or they may use irradiation to destroy the unwanted pests that can accompany food when it is traded regionally or imported from other countries.
Irradiated food does not become radioactive. When the treatment stops, energy does not remain in the food. The gamma rays of radioactive Cobalt 60 do not have enough energy to make food radioactive. Also, the food does not come into contact with the energy source, so it cannot become contaminated by radioactive material.
All food preservation methods, such as canning and freezing, change the composition of the food in some way. Some change the taste, appearance, texture, and nutritional value of the food more than others do. When food is cooked or preserved in any way, its composition changes and new compounds form. Irradiation causes minimal changes to the chemical composition of the food, though many of the composition changes that do occur are similar to those formed when food is cooked or preserved in more traditional ways.
However, with irradiation, different doses have different effects. At low doses, irradiation lengthens the shelf life of fruits like strawberries by destroying moulds and inhibits sprouting in vegetables like potatoes. At higher doses, irradiation helps to kill the bacteria and pathogens that cause food poisoning.
More than 40 countries allow the use of irradiation for food safety reasons. Most of the frogs legs sold in France, for example, are irradiated. Most of the herbs and spices sold in South Africa have been irradiated, while in Thailand there is growing demand for irradiated Nham, a fermented pork sausage that is usually eaten raw.
The labelling requirements vary, however, from country to country. Some, like the European Union, require the labelling of any food that contains an irradiated ingredient, however small the percentage of that product. This is also the case in Australia and New Zealand. In the United States, labelling applies only where the whole food item is treated.
Facts Sheets:
Food irradiation - updated March 2003
Irradiation of tropical fruit - updated March 2003