September/October 2021 - 25

WWW.CENTERFORPRODUCESAFETY.ORG
CPS
What's your food safety nightmare?
What fresh produce
By Drew McDonald
Center for Produce
Safety
food-safety topics
keep industry leaders
awake at night?
Matt Miles, process
engineer with apple
grower/packer Allan
Bros., revealed one of
his nightmares during
a Center for Produce
Safety (CPS) Research
Symposium webinar on June 22:
" VBNCs. Even our negative (pathogen)
tests might not actually be negatives. "
Miles and other industry leaders joined
me to share how we've applied learnings
from CPS's produce-specific research to
our businesses' food safety programs.
He teed up a presentation during that
webinar by Spain's Ana Allende, Ph.D.
Her team studied whether exposure to
common industry wash water sanitizers
can cause pathogenic bacteria to become
" viable but nonculturable " (VBNC) -
alive but unable to grow, so they can't
be detected by culture tests, but can later
resuscitate to pose a food safety threat.
Sanitizers vs. VBNCs
" We know this is quite a controversial
topic, " Allende said. " We wanted to help
answer industry's questions. "
Allende explained that pathogens,
including Listeria monocytogenes and E.
coli, can become VBNC when stressed -
such as being exposed to sanitizers used
in fresh produce operations' wash water.
Her CPS-funded research shows that
common sanitizers, including sodium
hypochlorite, chlorine dioxide and
peroxyacetic acid, can stress pathogens
into a VBNC state. Further, Allende
found that VBNC pathogens can attach to
produce during washing. They can then
not only survive on produce in storage,
but in 20% of trials they recovered to
a viable, culturable state when stored
at even a chilly 7 degrees Celsius
(23 degrees Fahrenheit), presenting a
potential food safety concern.
" Is the antimicrobial effectiveness of
commercial sanitizers in produce wash
Environmental Stress
WATER DISINFECTANTS
Active
bacteria
Optimal
Conditions
Resuscitation
Viable
and low
metabolic
bacteria
Adverse
Conditions
to mitigate listeria once it is found in
produce packing and processing facilities.
Wiedmann's team first reviewed
Culture
Cell Death
water overestimated by conventional
plate-count tests? Under the conditions
we examined, the efficacy of some
sanitizers can be overestimated, "
Allende told attendees.
Specifically, for each of the sanitizers
tested, Allende found that whether
inoculated pathogens are inactivated,
or VBNCs are induced,
is directly
related to the dose level of the sanitizer,
and how long the sanitized water is in
contact with the pathogen-inoculated
fresh produce being washed.
For example, she found that pathogens
aren't completely inactivated and some
level of VBNC is induced at sodium
hypochlorite (chlorine) levels below
5 ppm; she noted a dose of 10-20 ppm
is needed to successfully kill pathogens.
Critically, no dose of peroxyacetic
acid tested - up to the U.S.-allowed
maximum of 80 ppm - completely
inactivates pathogens, and some level
of VBNC is induced.
" Are foodborne pathogens in a VBNC
state a safety concern? " she continued.
" Based on these results, that is a low
probability... More research is needed
to establish critical limits " for abusive
storage conditions, she added.
Mitigating listeria
Allende's research put a spotlight on
Martin Wiedmann's, Ph.D., report at
CPS's June 29 symposium webinar. While
to date research has largely focused
on preventing listeria contamination,
Wiedmann and his Cornell University
team studied cleaning and sanitizing
1,600-plus studies on listeria and
fresh produce. Armed with those
learnings, they then sought to identify
likely locations of both persistent and
persistently transient listeria in several
packinghouses, taking 1,000-plus swabs
at each. They also tested ways to mitigate
listeria on-site - using a computer model,
because introducing pathogens into real
environments is, as we all know, risky.
Wiedmann reported he was surprised
at some of the places where listeria was
persistent - including forklifts, forklift
stops, even stickers on equipment. Other
common areas included catch pans,
wax area equipment and junctures
where floors meet walls. He noted deep
cleaning alone is not sufficient.
" Breaking down equipment, and
identifying hard to reach areas, is more
important than just throwing different
types of sanitizers at the problem, " he said.
Allan Bros.' Miles stressed the value
he's taken away from the experiences of
and conversations around CPS research
events. To him, " having the ability to
attend a symposium and speak with
principal investigators are the most
important parts of being involved with
CPS, " even virtually.
My experience is that CPS-funded
researchers are indeed incredibly
responsive when industry contacts
them - just ask.
For more news from this year's
CPS Re sea r ch Sympos ium -
including webinar recordings, and
written key learnings - visit the
Events section of CPS's website at
www.centerforproducesafety.org.
Drew McDonald is senior vice president
of quality and food safety for Taylor Fresh
Foods, and the longtime chair of Center
for Produce Safety's Technical Committee.
This group of industry volunteers provide
the scrutiny and controls needed to ensure
that the research CPS funds is practical,
and translatable to the real world.
PRODUCE PROCESS ING
23
http://WWW.CENTERFORPRODUCESAFETY.ORG http://www.centerforproducesafety.org
September/October 2021

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