June 2021 - 20

FOOD SAFETY ON THE FARM
CPS continues to fund research into listeria
By Stephen Kloosterman
Associate Editor
Unless one counts Korean-grown
Enoki mushrooms, the U.S. Centers for
Disease Control has not tied fruits or
vegetables to a major outbreak of listeria
infections since 2016.
And yet, the pathogen is deadly enough
to merit further study by the produce
industry. While salmonella and E. coli
foodborne illness have higher numbers of
outbreaks and individual cases, Cornell
University professor Martin Wiedmann
said the number of deaths due to listeria is
the same or higher.
" If you have an outbreak or even a case,
it's much more likely that people die, and it
tends to be even more severe than E. coli.
Ninety percent of people with listeria end
up in the hospital, and 15-20% of people
die, " Wiedmann said. " So, it's very, very
severe - what makes it worse is, some of
these severe cases are actually abortions in
pregnant women. "
Wiedmann, a specialist in food
science, will present at the Center for
Produce Safety's (CPS) virtual research
symposium this summer. CPS in 2020 had
funded Wiedmann's research evaluating
prioritizing different interventions for
produce processing plants. It also recently
funded a study looking at the effectiveness
of listeria's resistance to hand sanitizer
by Xiangyu Deng of the University of
Georgia.
Uncanny survival
Of concern to the produce industry is
listeria's " uncanny " ability to live in food
processing facilities for long periods of
time - as much as 10-15 years, Wiedmann
said. Listeria can live in the difficult-toclean
areas of machinery or cracks of
Cornell University professor Martin Wiedmann studies the impact of listeria on food
safety. Photo: Cornell University
the processing plant floor, infecting only
a small percentage of the total product.
But with modern DNA profiling of the
bacteria, the CDC is able to match several
cases occurring over a long period of time,
and it then would initiate an investigation
with interviews. Eventually, in such an
investigation, CDC would visit a business
conducting what's known in the industry
as a " swab-a-thon " - taking dozens of
samples around the processing plant to
look for pathogens.
Wiedmann distinguishes between the
public health risk and the business risk.
" If (the Food and Drug Administration)
or your customer finds listeria on your
product, your apples, that's a recall, and
then that brings all the negative business
consequences, " he said.
Different approaches
Companies use a variety of different
approaches to mitigate risk. Some have
staff or a third-party stage their own swaba-thons
to check if procedures work.
" That's a very valuable strategy, "
Wiedmann said. " Once a year, bring in
someone independent to almost be fake
FDA in terms of taking samples like FDA
works, so you're prepared and you know
where your weaknesses are. "
While sanitizers are part of food safety,
Wiedmann said it's possible to overspend
on sanitizer products, especially if they
aren't reaching cracks or inside machinery
where the bacteria may be living.
" You're spending your money on
biofilm-busting technology, when you
really should take that money and spend it
on redesigning your equipment, or hiring
another person on your sanitation shift,
so you can take apart that equipment so
you can reach the spots where the sanitizer
doesn't reach it, " he said. " Sometimes
cleaning equipment doesn't work.
Sometimes you have to come up with
something else. ... I think in terms of
sanitary equipment design we can learn a
lot from the meatpacking industry. "
Wiedmann advocates that processing
facilities develop programs and train
staff to conduct " root cause analysis " to
determine where listeria is coming from
or hiding out, and then prioritize which of
those root causes to first address.
Case studies
One outbreak of listeriosis in 2014
was linked to commercially produced,
prepackaged caramel apples.
" In general, apples are acidic enough,
and just don't support growth of listeria, "
he said. " What had happened with
caramel apples is, (when) you stick this
wooden stick into the core, you essentially
created an environment that allowed the
listeria to grow. "
For listeria on a food item to reach
a level of toxicity causing death or an
abortion, it usually has to grow for some
time, Wiedmann said.
" For listeria to cause an issue, it needs to
be on the food, but then it needs to grow
on the food, " he said. " It needs to grow to
high enough numbers so there is a risk of
making someone sick. This whole idea of
grow/not grow is very clear if you look at
the types of foods that cause issues. ... All
these things are stored at refrigeration-level
temperatures long enough that listeria can
grow. "
For his research funded by CPS,
Wiedmann and co-principal investigator
Renata Ivanek, also of Cornell, dove into
some 1,656 documents looking for what
sorts of listeria-fighting interventions or
strategies worked best. After narrowing
the group down to 264, the team further
screened them to identify about 32
of the most relevant strategies. They
then validated some interventions
they identified with four cooperating
packinghouse facilities.
Wiedmann's presentation at the CPS'
virtual research symposium this summer
will contain a lot of real-world examples.
" I'm a scientist, and it's all about the
science, right? But, sometimes the stories
you can tell about individual facilities -
obviously anonymously - what issues you
find can help people to see their facilities in
a different light. " FGN
Blueberry Plants Directly From the Grower
➢ State of Michigan Certified
" Virus-tested " Blueberries
➢ 20+ Varieties of Highbush
There is a Berkeley Pump to fit your growing needs:
irrigation, packing shed or green house.
Call us for a FREE product catalog
website: www.springbrooksupply.com
e-mail: sbs@springbrooksupply.com
20 | FruitGrowersNews.com
877-396-1956 toll free
11291 Lakewood Blvd.,
Holland, MI 49424
➢ 8+ Low to Half-highbush
Varieties USDA Zones 3-4
➢ Cranberry Plants Also
Catalog Available on Our
Website
76241 14th Ave South Haven, MI
269-637-3915
sales@degrandchamps.com
www.degrandchamps.com
http://www.springbrooksupply.com http://www.degrandchamps.com http://www.FruitGrowersNews.com
June 2021

Table of Contents for the Digital Edition of June 2021
