New x-ray machines may kill food bacteria, prevent outbreaks
Source of Article: http://www.environmentalhealthnews.org/ehs/news/x-raying-food Zapping nuts, spinach, lettuce and other foods with x-rays could kill more
pathogens that cause nationwide disease outbreaks. Drawbacks remain, however.
By Jessica Knoblauch Environmental Health News February 24, 2009 Researchers are experimenting with x-ray technology to zap
dangerous bacteria that hide in foods
such as leafy greens, tomatoes, ground beef and, most recently, peanuts. A new x-ray machine being tested at As such methods improve, some food safety experts say irradiation is a
necessary step that could prevent many illnesses and deaths tied to E. coli
and salmonella. In August, the Food
and Drug Administration approved irradiation for iceberg lettuce and
spinach, which have been responsible for some of the worst outbreaks in
recent years. That approval is expected to open doors to more irradiated foods. “The question is, do we want to keep on working with
technologies that are 19th and 20th century technologies or do we make a decision
as a country to move into the 21st
century?” asks Suresh Pillai, director of the National
Center for Electron Beam Research at Texas
A&M University. About 76 million Americans are stricken with food-borne illness each year. In the
increasingly global food
economy, a single head of contaminated lettuce can spread across
state lines and contaminate many people. Peanut products contaminated with salmonella have sickened
more than 650 people in 44 states and killed at least nine since December.
And in 2006, spinach tainted with E. coli from one field in Irradiation, also known as cold pasteurization, kills
harmful bacteria by briefly exposing food
to ionizing radiation, or short energy wavelengths. Irradiation has already
been approved for use on many foods,
including spices, poultry, wheat flour and ground beef. FDA officials,
who have conducted irradiation safety evaluations for more than 40 years, say
they have "determined the process to be safe for use on a variety of foods." But there are many barriers to irradiating foods on a larger scale, particularly
fresh produce. Some experts say it’s not ready for mass production due to a
lack of major facilities. Also, irradiation is not permitted on certified
organic products. And much of the public is still uneasy about buying foods that carry an international symbol
for irradiation. “The recent FDA approval for irradiating spinach and
iceberg lettuce is misleading to the public because it’s not ready for
industrial use by any means,” says Will Daniels, who oversees food safety at organic leafy greens
producer Earthbound Farm. “There are some food
items currently irradiated, but by no means are these irradiation facilities
geared up to irradiate everybody’s fresh produce.” Salmonella and E. coli 0157:H7-- involved in many of the
recent outbreaks --are two of the pathogens targeted by the new technology at
MSU. The x-ray machine uses a higher dose of irradiation than
medical x-ray imaging, yet less than competing irradiation methods such as
gamma ray and electron beam. So far, the researchers have proved that x-rays
can kill bacterial pathogens on ground beef, leafy greens and nuts. “Our work to date has shown that x-ray technology is very
effective in killing the bacterial pathogens without causing undesirable
changes in product quality,” says Bradley Marks, a professor in the MSU Department of Biosystems and Agricultural Engineering. The MSU researchers are concentrating on x-ray irradiation
because most research to date has been almost exclusively conducted with
gamma ray or e-beam. According to the Centers for Disease Control and
Prevention, only four commercial x-ray irradiation units have been built
in the world since 1996. “Our overall goal is not to promote a particular
technology, but to give food
processors the best information available so that they can decide which
irradiation technology is best for their process,” Marks says. Currently, the MSU researchers are testing their
technology’s ability to kill pathogens in nuts such as walnuts or almonds,
with a possibility for future work on peanuts. Nuts, because of their high fat and oil content, tend to
become rancid after irradiation. “High fat/oil products naturally become
rancid over time. Irradiation could speed up that process,” Marks says,
adding, “I’m not saying that it will happen, but we just need to test for
that.” Patrick Archer, President of the American
Peanut Council, says irradiation has been tested on peanuts in the past,
but was “found unacceptable because it degraded the taste of the nut.” However, MSU’s preliminary tests
show no major quality problems such as rancidity, possibly due to the
different nature of x-ray irradiation, which is lower energy than other
methods. To determine the proper dosage, the researchers first
inject food with bacteria. The
contaminated food is then put in a
prototype machine that’s about the size of three home refrigerators hooked
together. After the food is
irradiated, the researchers count any surviving bacteria and look for
physical changes in the food
product. “Our preliminary results have shown that x-ray technology
is at least as effective at killing bacteria as e-beam or gamma ray, and in
some cases it might be more effective,” Marks says. A major advantage is that its low energy
requires less protective shielding which means the equipment is more
compact and can be installed right in the processing plants. Other
irradiation methods have to be located in specialty facilities. One downside, however, is that the x-ray can only process
small quantities of food at a time,
such as five-pound bags of lettuce. “You have to treat the product in single
servings,” Marks says. Other technologies can irradiate food by the pallet. Rayfresh Foods Inc., a technology start-up
company that provided MSU with an x-ray prototype machine, is looking to ramp
it up to a commercial scale. Recently, the company landed its first contract
to build an x-ray machine to treat ground beef for Omaha Steaks. “We feel very strongly that if we’re going to sell ground
beef, it’s going to be irradiated because that’s the highest level of food safety that we can provide to our
customers,” says Beth Weiss, public relations director at Omaha Steaks. The steak company has been irradiating its ground beef
since 2000, but currently the meat has to be sent on a five-day road trip to Chris Schoch, the vice president
of sales at Rayfresh, said the third-party testing
MSU performs helps establish credibility for the technology. Schoch said irradiation is ideal for high-risk products
such as ready-to-eat foods like
bagged lettuce and raw nuts because there is currently no other kill step
that’s as effective at wiping out bacteria. Rayfresh has proven the x-ray
process can cut pathogens like E. coli and salmonella from 100,000 microbes
per product sample to one. “We have had success with complete sterilization,”
says Schoch. But irradiation is no silver bullet. Instead, many said it should serve merely as an
additional step to complement other food
safety practices. “If you irradiate a product but then expose that product to
other contamination risks, then irradiating the product was a waste of your
time,” Marks says. For example, irradiation probably would not have been able
to prevent the recent salmonella outbreak in peanuts, where poor sanitary
conditions and employee negligence were the culprits. The public is still unsure about irradiated foods, despite the fact that some food products like spices have been
irradiated since the 1900s. No radioactive substances remain in irradiated foods. Irradiation is a type of energy
that disappears when the energy source is removed. However, the public’s uneasiness could change as more foodborne
illness outbreaks occur. “After a foodborne illness outbreak, if
people hear irradiation will increase safety, the majority are interested in
trying irradiated food,” says Dr.
Christine Bruhn, director of the Center for Consumer Research at the Bruhn said health authorities need to take a more active
role in advising the public that they can choose irradiated ground beef,
poultry, spinach and lettuce and that supermarkets should offer them at
reasonable prices. The Organic Consumers Association disagrees, claiming
that irradiated foods only appear
fresh and contain fewer vitamins than non-treated foods. Many food
processors believe that irradiation is not the only answer to eliminating
pathogens. Organic producers such as Earthbound Farm are not allowed
to use irradiation under the National Organics Program standards. Earthbound Farm, which packaged the spinach
responsible for the 2006 E. coli outbreak, has since put in place the
industry’s most aggressive testing and safety program. Included is a process
of triple-washing foods with a
chlorine rinse and pathogen-testing at every step of production. In 2008,
0.14% of the leafy greens that arrived at Earthbound Farm’s plant tested
positive for salmonella or E. coli and was destroyed. Many leafy greens producers have signed onto a The peanut outbreak has also renewed interested in
revamping what food safety experts
believe to be an outdated food
safety system. Agriculture Secretary Tom Vilsack
said he supports merging the nation's food-safety
system, which is currently divided into the US Department of Agriculture and
the FDA, into one agency. Meanwhile, some food
safety experts maintain that any tool demonstrated to be safe and effective
should be available to protect the public from harmful bacteria. Said Bruhn,
“The goal is to protect the public while permitting the consumption of
healthful tasty foods.” |
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