Second, as the food never comes into direct contact with the source, it is not possible for the food to become contaminated with the radioactive material. You cannot successfully freeze or can all types of food. Similarly, not all types of food can be treated with ionising radiation. For example, many dairy products treated with ionising radiation develop objectionable changes in flavour, odour and colour, even at low doses. Whole eggs are another product that may not be successfully treated.
Irradiation is ineffective against viruses.
Food irradiation is not a substitute for proper food handling and cannot enhance food that is deteriorated, contaminated or of inferior quality, or prevent contamination from improper handling after irradiation. Irradiation is an option as part of a total system to improve food hygiene throughout the food processing and handling chain. Irradiation of foods may help reduce the incidence of food borne disease. It could also help prevent insect pests entering or leaving the country on certain foodstuffs, and it would be an alternative to some chemical treatments of food. In many countries, including New Zealand, an increasing number of people are becoming sick from food borne diseases caused by micro-organisms like Campylobacter and Listeria .