Unfortunately, many consumers are unaware that utensils and
other surfaces at home can contribute to the spread of bacteria, said the
study’s lead author Marilyn Erickson, an associate professor in the College of
Agricultural and Environmental Sciences’ department of food science and
technology.
“Just knowing that utensils may lead to cross-contamination is
important,” Erickson said. “With that knowledge, consumers are then more likely
to make sure they wash them in between uses.”
Erickson has been researching produce for the past 10 years.
Her past work has mainly focused on the fate of bacteria on produce when it’s
introduced to plants in the field during farming.
In 2013, she was co-author on a study looking at the transfer
of norovirus and hepatitis A between produce and common kitchen
utensils—finding that cutting and grating increased the number of contaminated
produce items when that utensil had first been used to process a contaminated
item.
This study, published in Food Microbiology, is similar in that
it considers the influence that knives and graters have on the transfer of
pathogenic bacteria to and from produce items. She urges consumers to realize
that these germs can spread in their kitchens as well.
Researchers have known that poor hygiene and improper food
preparation practices in a consumer’s home can lead to foodborne illnesses, but
considering what practices in the kitchen are more likely to lead to
contamination has not been examined extensively.
“The FDA was interested in getting more accurate numbers as to
what level of cross-contamination could occur in the kitchen using standard
practices,” Erickson said.
In her recent study, Erickson contaminated many types of
fruits and vegetables in her lab—adding certain pathogens that often can be
found on these foods, such as salmonella and E. coli.
Using a knife, Erickson would cut into things like tomatoes or
cantaloupe and other types of produce to see how easily the bacteria could
spread when the knife was continuously used without being cleaned. Because they
“were looking at what would be the worst-case scenario,” she said, Erickson and
study co-authors did not wash between cutting these different produce items.
Researchers also grated produce, like carrots, to see how
easily the pathogens spread to graters. They found that both knives and graters
can cause additional cross-contamination in the kitchen and that the pathogens
were spread from produce to produce if they hadn’t washed the utensils.
“A lot of the broken up material and particles from the
contaminated produce remained on the graters,” said Erickson, who conducts her
research at the UGA Center for Food Safety in Griffin. “Then if you were to
shred another carrot or something else immediately after that, it gets
contaminated, too.”
The study also found that certain fruits and vegetables spread
pathogens to knives to different degrees.
“For items like tomatoes, we tended to have a higher
contamination of the knives than when we cut strawberries,” Erickson said. “We
don’t have a specific answer as to why there are differences between the
different produce groups. But we do know that once a pathogen gets on the food,
it’s difficult to remove.”
Knives and graters aren’t the only utensils in the kitchen
consumers should be worried about. Erickson has also helped study the role
brushes and peelers have on the transfer of dangerous kitchen bacteria.
In concurrent studies, Erickson found that scrubbing or
peeling produce items—like melons, carrots and celery—did not eliminate
contamination on the produce item but led to contamination of the brush or
peeler.
Even when placed under running water, the utensils still
became contaminated; however, the ability to cross-contaminate later produce
items depended on the brush type and the pathogenic agent.
These studies combined give researchers a better idea as to
how common cross-contamination is in the kitchen—even when just using standard
practices.
Erickson explained there is a small chance of buying fruits
and vegetables contaminated with bacteria, but the problem can occur—whether
the product is store-bought or locally grown.
Additional study co-authors were Qing Wang, a doctoral student
at the University of Delaware, and Jean Liao, a research professional; and
associate professors Jennifer Cannon and Ynes Ortega with UGA’s Center for Food
Safety.
The study, “Contamination of knives and graters by bacterial
foodborne pathogens during slicing and grating of produce,” is available athttp://www.sciencedirect.com/science/article/pii/S0740002015001306.
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