Food irradiation

March 2003

What is food irradiation?

Food irradiation exposes certain types of food to a source of ionising energy. Under the standard covering the irradiation of food in Australia and New Zealand, this energy can be in the form of Cobalt 60 sourced gamma rays, machine generated X-rays, or an electrically generated electron beam.

Electron beam and X-ray technologies allow the energy source to be switched on and off and do not use radioactive material. Gamma rays are generated from the radioactive source Cobalt 60.

Does irradiated food become radioactive?

No. When the treatment stops, energy does not remain in the food. Where a radioactive Cobalt 60 source is used, the gamma rays 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.

Why is food irradiated?

Food is irradiated to destroy micro-organisms that cause food decomposition and food poisoning. Those micro-organisms may include moulds and yeasts that spoil food, and those that cause illness (e.g. Salmonella). Irradiation can also be used to destroy the unwanted pests that can accompany food when it is traded regionally or imported from other countries.

Different doses of irradiation have different effects. At low doses, irradiation lengthens the shelf life of fruits like strawberries by destroying mould, inhibiting sprouting in vegetables like potatoes, or reducing or killing unwanted pests as part of a quarantine requirement. At higher doses, irradiation helps to kill the bacteria and pathogens that cause food poisoning.

What happens when food is irradiated?

Food irradiation has the potential to change the composition of the food in some way. This may lead to a change in the taste, appearance, texture, composition and nutritional value of the food. Irradiation, like other techniques (heating, micro-waving, freezing and canning) can break some of the larger molecules into smaller ones (fragments). Each of the three major macronutrients in food (carbohydrates, proteins and fats) gives rise to different types of products.  

 Research has shown that, in the case of irradiation, the change in the chemical composition of the food is minimal. Many of the resulting compounds are the same as those formed when food is cooked or preserved in more traditional ways. These products have been chemically analysed and generally consist of common chemicals produced either in the biochemical pathways of the human body or from other treatment processes such as heating.

The possible exceptions to this are compounds known as 2-alkylcyclobutanones, in particular, 2-dodecyclobutanone (2-DCB), which, although not yet proven to be a unique product, is produced following irradiation of fat-containing food. There is currently ongoing research to identify and characterise these products further.

Can irradiation be used to improve food that is already spoiled or of second-grade quality?

No  Irradiation does not improve the quality of spoiled food and irradiation should not take the place of good hygienic practices and good manufacturing practices (GMP), which would normally prevent the growth of pathogenic strains of bacteria, eg Clostridium botulinum.

Is food irradiation approved in Australia and New Zealand as a technique that can be used on all foods?

No  Australia and New Zealand have strict standards in place that require a pre-market assessment of any foods proposal to irradiate foods. Standard 1.5.3 - Food Irradiation requires an application to be made to Food Standards Australia New Zealand (FSANZ) and for FSANZ to conduct a risk assessment which normally includes two rounds of public consultation. The FSANZ Board makes a decision on the outcome of the application.

What does FSANZ consider when assessing an application to irradiate food?

FSANZ undertakes a detailed assessment of any application for permission to irradiate food to ensure the following:

• to determine whether the food is safe for consumers and that there is no significant reductions in nutritional value following irradiation - that is, the food is wholesome;
  
  
• that a technological need exists to irradiate food and that the technique actually works;
  
  
• that irradiation is not used as a measure to manage poor hygiene management;
  
  
• that irradiated food is labelled so that consumers may make an informed choice; and that
  
  
• there is consistency with other international standards.

What irradiated foods are currently approved in Australia and New Zealand?

Approval was granted in September 2001 for the use of irradiation on herbs, spices and herbal infusions for control of microbes and for reduction of pests of quarantine concern.  

  In March 2003 the Food Standards Code was changed to allow the irradiation of the tropical fruits breadfruit, carambola, custard apple, litchi, longan, mango, mangosteen, papaya and rambutan as a pest disinfestation measure for critical quarantine pests such as the fruit fly. The permission is for irradiation to a maximum of 1 kilogray from machine-sourced electron beams or x-rays, employing Good Manufacturing/Irradiation Practices. Irradiated tropical fruits require mandatory labelling to give consumers an informed choice when buying these fruits.  

The application of irradiation for this purpose must be in accordance with the requirements of quarantine authorities in Australia and New Zealand.

Further information

Standard 1.5.2 - Food Irradiation can be accessed on the FSANZ website at www.foodstandards.gov.au.