Irradiation can be used to kill the bacteria that cause food poisoning. It can also delay fruit ripening, help stop vegetables such as potatoes and onions from sprouting and delay other deterioration.
It is a process that produces a similar effect to pasteurisation, cooking or other forms of heat treatment, but irradiation only raises the temperature of food by a few degrees and so there is less impact on taste, look and texture. The irradiation of spices, for example, does not change their flavour or aroma.
It is used in many parts of the world because it is an effective way of killing bacteria.
How does it work?Beams of radiation pass into food and transfer energy. Bacteria absorb some of this energy and are killed.
However, most energy is absorbed by the food itself and it causes the formation of short-lived molecules known as free radicals, which also kill micro-organisms, such as bacteria, and also interact with other food molecules. Free radicals are also formed in food by other processing techniques, including cooking, chopping and grinding.
Irradiated food is not the same as radioactive food. Radioactivity is present naturally in our environment, including the food that we eat. Food irradiation does not add to the natural radioactivity in food. Irradiating food does not make it radioactive – just as food that has been heated in a microwave oven does not give out microwaves.
Is it safe?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.
All food preservation techniques cause chemical changes in food – that is how they work. The changes caused by food irradiation are similar, although less, than those caused by other preservation techniques, such as cooking, canning and pasteurisation.
What foods are irradiated in the UK?Current national regulations allow for the irradiation of seven categories of food: fruit, vegetables, cereals, bulbs and tubers, spices and condiments, fish and shellfish, and poultry. However, only one UK licence, for the irradiation of a number of herbs and spices, has so far been granted.
How do I know if a food has been irradiated?There is no noticeable difference to the smell, taste or appearance of food that has been irradiated.
However, all foods, or ingredients of foods listed on the label, that have been irradiated, must be labelled as 'irradiated' or 'treated with ionising radiation'. When irradiated food is not pre-packed and is sold to be eaten immediately (for example, in restaurants) it must be marked or labelled on a menu, notice or ticket so you can see it when deciding what to eat.
If the restaurant is using irradiated dried herbs and spices for seasoning there may instead be a general indication on a menu, notice, ticket or label that food sold there may contain those types of ingredients.
For several food types, including meat, herbs and spices, there are tests that can show if food has been irradiated. These are used in surveys by the Food Standards Agency to make sure that the rules on irradiation are not being broken.