Research Magazine > ARCHIVE > Fall
93 > Article
Grilling the Suspect in Food-Related Illness
by Rosann Kent
The scenario mirrors a Stephen King horror flick: A germ hidden in the nation's
meat supply randomly kills unsuspecting diners, especially the young, sick
Who will intervene?
Michael Doyle already has. The food scientist's research on E. coli bacteria
has turned a lot of heads in the food industry, including giants like McDonalds,
and made them take a second look at how they cook their burgers.
The point is to destroy Escherichia coli, a bacterium which lives in the intestinal
tracts of cattle and can contaminate ground beef during slaughter. One strain
of E. coli, labeled O157:H7, claimed the lives of more than 300 people and
induced illness in thousands more last year, according to estimates by the
U.S. Department of Agriculture (USDA).
When three children died after eating hamburgers from a Jack-In-The-Box restaurant
in Washington state last year, Doyle was called into the case.
Working with USDA scientists, the UGA food science department head proved a
point he'd been making for years: Hamburger meat must be cooked to a temperature
of 155o Fahrenheit to kill the potentially lethal bacterium.
In the Jack-In-The-Box case, "the pathogen was present in populations
of less than 100 E. coli per gram in all samples tested," a very minute
amount, said Doyle, who also directs the Center for Food Safety and Quality
Enhancement at the UGA Experiment Station in Griffin, Ga.
But, he stressed, proper cooking would have prevented the food-borne illness.
"It turns out that the restaurant was cooking at or under the government-
recommended temperature of 140 degrees," he said.
After that incident, the U.S. Food and Drug Administration raised the recommended
cooking temperature to 155o F for restaurant-cooked hamburgers -- a benchmark
Doyle had suggested to colleagues three years ago.
Recently, the USDA recommended even higher cooking temperatures: 157o for restaurants
and 160o for the home.
Doyle has conducted several studies for McDonalds to find out how much time
and temperature is required to kill the organisms on their particular patties.
And he's also developed a new test that will enable food processors to detect
the presence of the O157:H7 strain in less than 24 hours. Previously, the test
took about a week.
Although Doyle continues to work on more tests to improve detection of E. coli
in raw meat -- another one is scheduled to be released within two years --
he points out the new tests are only an interim step in solving the problems
of food poisonings from meat.
"It's just not practical to test the huge number of meat samples necessary
to be reasonably sure the bacteria isn't present," he said.
So he also is exploring early detection methods to prevent cross- contamination
of pathogen-free meat at the slaughterhouse.
"The best solution is to identify the cattle that carry the E. coli 0157:H7
strain before they are slaughtered and then process meat from these cattle only
into fully cooked meat products," Doyle said.
He also is helping the USDA conduct a 15-state survey to determine how widespread
the 0157:H7 strain is in dairy cattle.
"Out of 12 herds that were previously identified as free of E. coli, five
were found to be E. coli positive," he said. "These results suggest
that this pathogen may be more prevalent in dairy herds than previously recognized."
Last spring, U.S. Secretary of Agriculture Mike Espy invited Doyle to submit
a proposal to develop a vaccine to protect cattle from carrying E. coli O157:H7.
"Preliminary research has identified a specific antigen that has potential
for vaccine development," Doyle said. The proposal was approved and studies
But in the meantime, Doyle said, consumers need to "assume raw ground
beef has E. coli O157:H7 and take precautions."
"You should always cook products with raw ground meat until the juice runs
clear," he said. "You also need to prevent cross contamination with
cold foods. And by all means, take hand washing seriously."
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