February 6, 2009
Why don't we irradiate all
Source of Article: http://www.sciam.com/article.cfm?id=food-irradiation-salmonella-ecoli
exists that destroys disease-causing bacteria in food. We use it more--and in
some cases, less--than you might think
By Jordan Lite
LURKING DANGER?: Irradiation is commonly used to preserve
certain foods and destroy insects and germs in others, but it may not work
well in all products--or on all pathogens.
The four-month-long, nationwide salmonella outbreak from peanut butter—coming on the heels
of other, widespread food-borne illnesses—raises the question: Why not
just zap all of our food with radiation to destroy contaminants?
The U.S. Food and Drug Administration (FDA) last summer okayed irradiation to
destroy pathogens in fresh iceberg lettuce and spinach in the wake of an Escherichia
coli (E. coli) outbreak traced to the latter in 2006. Since the
early 1980s, irradiation has also been approved for that same purpose in
meats as well as to both extend the shelf life of and kill insects in fruits,
veggies and spices.
But radiation isn't commonly used to treat most foodstuffs in the U.S. because
of cost, consumer wariness and the worries of some about its
long-term safety. Food & Water Watch (FWW), a Washington, D.C.–based
advocacy group, frowns on the process, which it says degrades the
nutritional value of foods and has the potential to mask but not remedy
unsanitary conditions at plants that led to it in the first place.
We asked Sam Beattie, a food safety extension specialist at Iowa State
University in Ames, to fill us in on the controversial
process and why it hasn't been used more often, especially in light of the
recent deadly outbreaks. There is an irradiation facility at the university,
but it's used only for studies and Beattie, a microbiologist, has no
affiliation with companies that make irradiation devices or zap their food.
[An edited transcript of the interview follows.]
What is food irradiation, and how does it work?
Irradiation is done by exposing food or bacterium to a dose of ionizing
radiation, which disrupts the DNA or protein of pathogenic bacteria
that make people ill.
When we talk about the sources for irradiation, we're looking at two major
ones: radioactive elements—like cobalt 60—and the electron beam, or e-beam. Cobalt 60 is an
isotope, or a traceable radioactive version of the element, that emits the
type of radiation called gamma rays, whereas the e-beam is an electron-based radiation source. We also are experimenting
now with x-rays, which are generated from an electron beam hitting a
piece of metal, as a potentially new technology for
The potential problems of the irradiation processes are fairly
limited. As cobalt decays, it becomes less effective, so you have to monitor
that. E-beams don't penetrate as deeply as cobalt, so you have to irradiate
less of a food at a time. And generating x-rays takes an extra step, so it
may not be as efficient as e-beam.
Cobalt 60 has historical precedence with food. It's been used for a long time
with meats, fruits and vegetables. It is a safe source: When it decays, it
becomes a stable, less radioactive element — in this case nickel, so
disposing of it is less of a problem than with isotopes used at, say, nuclear
plants. And there is no direct contact between the cobalt and the food or its
How long does it take to zap bugs in food?
It depends on the kind of radiation you're using. Cobalt 60 is a lower dose
rate, so it takes longer—a minutes type of exposure. E-beam is a more
intense, higher dose rate and we're looking at seconds.
Which foods is irradiation most used on?
Among fresh produce, the FDA has only approved irradiation to reduce
food-borne illness in leaf spinach and iceberg lettuce. We're not exactly sure why only
those two, because there's very little difference between cut greens when it
comes to whether or not they turn to mush under an e-beam at the approved
Irradiation is approved for other purposes on a whole
variety of foods—everything from strawberries and other fresh fruits to meats
and spices. On bananas or something like that coming into the country, it
would be used to knock out pests, or to control sprouting and ripening. With
meat, it's approved as pasteurization to kill illness-causing organisms such
as E. Coli or salmonella.
Across the world, there are many countries, including the Netherlands, Belgium,
France, South Africa, Japan
that allow irradiation. You can argue that for some countries,
having the ability to prevent spoilage is an important contributor to enhancing
food security. Spoilage takes a lot of product off the shelves or makes it
Does irradiation affect taste or nutritional quality?
There's no difference in taste. I have had irradiated spinach and it doesn't
taste any different.
Some nutrients are impacted. Among vitamins B, C, B6, B2, E and precursors
for vitamins A and K, the loss that we see is comparable with the loss from
other food processes that we might use (like thermal processing for canning
or pasteurization), if not less.
Some irradiated products, mainly meat, do develop an aroma—it's not a bad
thing. If you vacuum package a raw pork cut and then
irradiate it, it develops a unique aroma that dissipates as soon as you open
How much does irradiating food cut down on germs that make us sick?
What we're trying to affect is a 99.9999 percent, or 100,000-fold reduction
We irradiate for the pathogen that is most risky and most likely to be there.
We would not necessarily be irradiating meat to, say, kill Clostridium botulinum spores, because there's a fairly
low risk of them growing and creating the toxin that causes botulism, which
may result in paralysis and death. But we would adjust the dosage to kill E. coli O157,
which is more likely to be there and to grow if the product is not stored at
the right temperature. We can actually count how long and at what dosage it
takes to kill a particular number of microorganisms per minute. It might take
a lot higher dosage to knock out C. botulinum
(E. coli O157 can cause severe stomach cramps, bloody diarrhea and
Does irradiation work against viruses?
It doesn't work as well against viruses. We're not sure why. But in processed food, viruses
don't typically cause problems. Where we do see them is in food-service food.
There are an estimated 76 million cases of food-borne illness each year, and about half are caused by norovirus,
or Norwalk-like virus. (Norovirus
causes nausea, vomiting, diarrhea and some stomach cramping.) They come from
someone failing to wash their hands; fecal material there then can be
transferred into food.
Could radiation be used to kill salmonella in peanut butter?
Products high in fat may not be very amenable to radiation. When fats break
down they produce off-flavors.
The U.S. Department of Agriculture (USDA) now requires almonds to be pasteurized, because of salmonella
outbreaks in 2001 and 2004. That same type of regulation will probably happen
to peanuts also, and that would be a thermal process—roasting in dry heat or
immersion in oil at a level that would kill disease-causing organisms.
To what extent do we use irradiation in the U.S. now?
A significant number of spices that enter this country are irradiated, but
otherwise, it's not so common. The problem becomes one of public perception.
People are not aware of the benefits compared with the minimal risk
associated with it. Some groups adamantly oppose irradiation. It does cause
changes, but these groups believe it causes negative health changes to humans
and that hasn't been shown.
What kinds of changes does irradiation cause?
Anytime you break bonds in chemicals you're going to introduce changes in the
molecules. The important part is that the changes don't impart any
toxicological effects to the food, and irradiation does not appear to do
that. You can see unique by-products formed, but there's been no evidence
that these cause human illness at the levels that they are in the food. There
was some thought that 2-alkylcyclobutanone, a by-product derived from fatty
acid, could cause cell mutations that might lead to cancer.
The most recent science evidence suggests otherwise: It was extensively
tested and does not cause mutations.
Does radiation stay in the food?
No. The food is not radioactive by any means. In fact the food is probably
safe, if not safer, than before it was irradiated. It's an entirely safe
process with wide application that could reduce hunger in some countries
through reduction of spoilage, and can certainly reduce food-borne illness in