Joe--Here's another one of those articles for your morning cup o'broth HOME ú NEW SCIENTIST ú NS+
[Archive: 3 January 1998]
Out of the frying pan
By Andy Coghlan
astronauts eat it. So do people with weakened
immune systems. Food that has been doused with
radiation to kill bacteria has become de rigueur in
many areas of life. And soon, we could all be eating
it.
After years in the wilderness as a technology without
a purpose, food irradiation is finally gaining favour.
Last month, after a three-year review, the US Food
and Drug Administration approved it for use on red
meat. The FDA hopes that the move will calm
growing public hysteria over food safety and appease
a beleaguered food industry seeking to clean up its act
after a string of poisoning incidents.
In 1993, four American children died after eating
undercooked beefburgers that were contaminated
with the bacterium Escherichia coli O157. That was
followed by an outbreak of food safety scares
culminating last August in the recall of 11 million
kilograms of hamburger beef thought to be tainted
with the same bug--all of which severely dented
public confidence in food safety. Last year, in a
survey of 1000 supermarket shoppers by the US
Food Marketing Institute in Washington DC, 7 out of
10 cited food spoilage as the major threat to food
safety, and 6 out of 10 said they were willing to buy
irradiated produce.
Food irradiation is also back on the menu in Europe,
where worries about BSE and genetically engineered
plants have wrecked consumer confidence in food
production and food technology. Later this month, the
European Parliament will debate a brace of directives
aimed at creating EU-wide rules for food irradiation.
Both directives could be on the statute books by this
summer.
In Britain, cases of salmonella in eggs and chickens
have risen alarmingly (see this week's lead story).
Fears over food safety reached new heights a year
ago when more than 20 Scottish pensioners died after
eating meat contaminated with E. coli O157. Hugh
Pennington, the professor of microbiology at the
University of Aberdeen who headed the government's
inquiry into the outbreak, thinks that irradiation might
be a useful tool to reduce the growing incidence of E.
coli O157 in cattle. "Things are moving in the US on
irradiation, and it really has to be seriously
reconsidered and revisited [in Britain]," he says.
Yet despite its growing popularity, the technology still
faces opposition. Claims by consumer groups that
irradiated food is unsafe to eat and of inferior
nutritional quality first emerged in the early 1990s
("Irradiated food: too hot to handle?", 17 February
1990, p 28). These are still alive, as are concerns that
irradiated products would appear on supermarket
shelves unlabelled, with consumers and even health
officers unable to distinguish between normal and
irradiated food. And worst of all, say critics,
overreliance on irradiation would make farmers, food
processors and retailers complacent about food
hygiene. Lapses earlier in the food-processing chain
could be masked at the last stage by irradiation.
The technology has been heavily touted for years by
the nuclear industry, the WHO and the UN's Food
and Agriculture Organization. It works by passing
powerful X-rays, high-energy beams of electrons or
radiation from radioactive cobalt into food to kill
microorganisms and prolong shelf life. The higher the
dose, the more organisms it kills.
Food processing companies have to strike a balance
between killing organisms and damaging food. To kill
viruses, for example, the dose would have to be so
high that the food would be destroyed. But relatively
low doses--as low as 5 kilograys (60 kilosieverts)--can
kill almost all bacteria. Fritz Kaferstein, director of the
WHO's food safety programme and a long-standing
backer of irradiation, points out that in the recent
Scotland poisoning case, "if the beef had been
irradiated with as little as 5 kilograys, it would have
got rid of the E.coli O157 before it got to the shop".
The WHO originally limited the dose used in
irradiation to 10 kilograys, but last September, after
its experts had reviewed safety and nutrition data, it
declared doses of any magnitude to be safe. Raising
the limit means, for example, that lethal bacterial
spores such as those of Clostridium botulinum,
which cause botulism, can now be eliminated with
irradiation.
The WHO is confident that it has laid to rest fears
that irradiated food is unsafe to eat. There had been
worries that the high-energy radiation created
dangerously reactive agents called radicals. Almost
everyone now accepts that these "radiolytic" products
are virtually indistinguishable from the "thermolytic"
products created through orthodox cooking. Even
consumer groups agree that the risks are minimal.
"Absolute safety doesn't exist, but to be honest, I've
not seen any evidence of harm with this technology,"
says Kees de Winter, food officer for the Office of
European Consumer Organisations in Brussels. Lucy
Harris, health policy spokeswoman for Consumers
International, an organisation representing 240
consumer groups, says: "We would agree that the
technology, if used correctly, would not be
dangerous."
There is also wider acceptance that although
irradiation damages vitamins, the same thing happens
during cooking. Friedrich Diehl, a supporter of
irradiation who retired in 1993 as director of
Germany's Federal Research Centre for Nutrition in
Karlsruhe, says that opponents of irradiation
overstated vitamin losses because they focused on
what happened under extreme, experimental
conditions. "In fact, vitamin losses through irradiation
are generally much less than in cooking," says Diehl.
Most consumer groups accept this too.
Fears over the identification and labelling of irradiated
foods are also subsiding, for this is the area where
most technical progress has been made. Several tests
now exist to distinguish irradiated foods from
non-irradiated ones. The best results have been with
seeds, herbs, meat, fish and eggs. The Northern
Ireland Department of Agriculture in Belfast has
developed a fast, cheap test that changes colour when
it is in contact with irradiated chicken flesh. The test
contains antibodies that detect cyclobutanones,
substances uniquely created in irradiated fats through
the breakdown of lipids such as palmitic and stearic
acid. "It's a family of compounds that provide a
telltale fingerprint of irradiation that's absolutely
definitive," says Cecil McMurray, chief scientific
officer at the department and a pioneer of methods to
detect irradiation.
Among other tests are those that rely on electron spin
resonance, a method of detecting specific radicals that
lodge in bone or cellulose in irradiated fish and
chicken, and some fruits. Techniques based on
thermoluminescence, meanwhile, can reveal irradiated
seeds, herbs, spices, fruits, vegetables and shellfish.
These are routinely and harmlessly contaminated with
silicate minerals which, when irradiated, trap energy
that can be released as a flash of light by
thermoluminescence. Several other tests are also
under evaluation, and McMurray is confident that
labelling laws can be made to stick. "Anyone who
irradiates without disclosing it on the label could now
be caught," he says.
But opponents are still adamant that the use of
irradiation would undermine efforts to make farmers
and food processing companies clean up the entire
food production chain. "Applying technology to a
problem that is generated by the way foods are
produced is not attacking the real problem," says
Harris. Others, such as de Winter, accept that
irradiation can have a role in polishing up products
such as raw seafood or minced meat that still remain
contaminated even if state-of-the-art hygiene operates
throughout the food chain. "Our position is that it can
be used if there's no other method of solving a
problem, so it's the last resort," says de Winter.
Some, such as Tim Lang of the Food Policy Institute
at Thames Valley University in London, remain
implacably opposed. "I see irradiation as a
monumental irrelevancy to the main task of cleaning
up a contaminated food system," he says. "You
should solve a hygiene problem at source, not cover it
up later." |
