Charles Arthur, Science Editor, looks at a technology that is slowly growing in popularity.
Last week the US Food and Drug Administration, the bugbear of much of the food industry in America, announced that it had approved the use of irradiation for beef, lamb and pork products to control food-borne disease.
The news was greeted with some quiet relief among US food manufacturers. For them, it's been a tough summer, in which consumer confidence has been, if not battered, then wavering, following outbreaks of infection with the E coli 0157 bacterium in a number of locations. Four people died, 200 were hospitalised and 55 suffered kidney problems. In all, 25 million pounds of hamburger meat were declared infected and recalled. Irradiation can kill E coli 0157. Hardly surprising that the food companies were keen to see it introduced for meats.
The FDA's decision follows a three-year study: it decided that irradiation is safe for consumers, and doesn't lower the nutritional quality of treated products.
In fact the technique is already widely used in the US to control insects and disease in fruit, vegetables, grains and spices. "Irradiation of meat could prove to be another important tool to protect consumers from food- borne disease," said Michael Friedman, deputy FDA commissioner. "The process has been shown to be safe and to ... reduce bacterial contamination." Significantly, though, it has no effect on viruses, another form of food-borne disease.
The FDA's decision was important in that it goes beyond what is currently allowed in the UK, where one company - Isotron, based in Swindon - has been licensed since June 1991 to carry out irradiation of various spices and vegetables.
Significantly, the 1991 legislation allowed fruit, vegetables, bulbs, roots and tubers, cereal grains, spices, poultry, fish, shellfish and condiments to be irradiated - but not beef and lamb.
The irradiation process itself is straightforward enough. The idea that radiation might be used to kill bacteria and other micro-organisms in food was first seriously proposed in the Thirties, but the technology for producing radiation was too expensive and specialised for it to be used other than in experiments.
Now, it's commercial. There are currently about 170 irradiation plants world-wide, using cobalt-60 - a radioactive substance with a half-life of about five years which emits beta particles and gamma rays. In the plants the source is kept in a water-filled pit inside a room with thick concrete walls, which absorb any residual radiation.
Racks of the food to be irradiated are placed around the top of the pit and the source is raised out of the water for a set time. Usually, the racks move around it on a simple rail track to irradiate them evenly.
Nowadays, irradiation plants are completely automated and computer-controlled, allowing time and dose levels to be closely controlled and ensuring that nobody is exposed to the radiation.
That's the mechanics. The effect is to kill most of the insects and pests that infest grain, and to destroy bacteria that might be breeding there.
However, it is not perfect by any means. Getting the dose even slightly wrong can make the difference between salmonella-free eggs, and salmonella- free eggs that taste awful and have an unpleasant texture to the tongue.
And, unfortunately, irradiation is not the answer either to those seeking a solution to the BSE crisis which rises, zombie-like, to ravage the British beef industry every few months or so - last week's announcement of the coming ban of "beef on the bone" being a case in point.
The trouble is, the best science available suggests that BSE is transmitted not by bacteria or viruses, but by misshapen proteins - "prions". Irradiation cannot destroy those proteins without being intense enough to destroy every other protein in the meat as well, destroying its consistency and leaving an apparently rotten mass.
Yet for all that, irradiation does clearly have its benefits. It can kill insects and pests that infest foods such as grains, herbs and spices without (apparently) affecting them; it can kill (or at least substantially reduce the level of) dangerous micro-organisms in foods, such as salmonella, listeria and campylobacter. It can slow down ripening, enabling foods to be stored for longer. And, significantly, it can completely sterilise a food, so that patients with compromised immune systems - for example, in hospital - can eat it safely. Consumers are also told when food has been irradiated, by an appropriately lurid diagram.
But it's not all one-way traffic in favour of irradiation. The process is relatively expensive; and it can reduce levels of vitamin E by up to 25 per cent, and vitamin C by 5-10 per cent. More important, it generally kills only about 90 per cent of micro-organisms; the food still has be treated with care. And, as noted, it has no effect on viruses.
Why isn't irradiation used more widely? World-wide, 38 countries have passed laws allowing its use, though only 25 of them have licensed any companies to perform it. Yet the United Nations Food and Agriculture Organisation (FAO) and the World Health Organisation (WHO) are keen supporters of this modern technology as a means for helping to feed countries where food supply is always a problem - the developing world.
The FAO argues that irradiation would, or could, reduce storage losses by killing pests and micro-organisms, increasing general supplies of food. The WHO is even keener, seeing irradiation as an effective means of reducing food-borne disease.
Yet consumer interest groups and those trying to reduce poverty in the Third World see these as technological fixes for problems that require something much more straightforward.
If storage losses are the main worry, they argue, it would be cheaper - and more effective in the long term - to build better storage houses to prevent rodents and other pests gnawing their way in, than to use an expensive, dangerous technology to win a temporary victory over these eternal opponents.
Similarly, health worries involving various bugs seem to be misplaced. "Many parts of the food chain have become completely contaminated with organisms such as salmonella, and the cost of decontaminating the whole process would be enormous," comments Consumers International, a London- based food consumer group.
Instead, they suggest that irradiation is a daft way of trying to get rid of an organism which is anyway endemic "in the farm environment, feed stocks and in the housings and transport systems". Again, it's a high- tech fix for a problem which - in the case of E coli and other bacteria - has a comparatively simple, low-tech solution: high-temperature cooking, and ensuring that potentially contaminated surfaces or objects (such as cooked meats and raw vegetables) don't come into contact.
So apart from the UN agencies, who likes the idea of food irradiation? The suspects turn out to have the profit motive at heart. The nuclear industry has a strong commercial interest in promoting peaceful applications for new products, such as food irradiation. And for the food manufacturers and retailers, longer shelf lives mean less wastage and shorter delivery times. Exotic foods can be ferried around the world without fear that they will rot on the way. Certainly, in the case of the Thai nahm sausage, which consists of raw pork, and various seafoods, irradiation is the only way to make sure that they're safe to eat.
Yet at the end of the day, such uses are for the delight of well-paid Western palates, rather than the people in the developing world who are struggling against natural foes such as drought and floods. It's like a micro-wave oven - useless unless you have some electricity and a particular sort of food to put into it. While irradiation may be a solution that the FDA in the US, and the Ministry of Agriculture, Fisheries and Food (Maff) are happy to approve, it won't feed the world any time soon - it will just add more choices to our part of it.Reuse content