Food Protection Trends - November/December 2021 - 556

Packinghouses (i.e., a facility that washes, sorts, culls,
grades, and/ or packages produce but does not perform any
processing steps) (15, 17, 27, 33, 35) and food processing
facilities (5, 16, 19, 22, 25, 32), in general have been shown
to often harbor Listeria. Listeria can be brought into the
packing environment on produce or produce bins (via the
preharvest environment), with employees serving as fomites,
via forklifts or other transportation vehicles, among other
routes (16, 17, 28, 30, 31, 39, 40). Once Listeria has been
transferred into a packinghouse, it can contaminate different
pieces of equipment and the packinghouse structure itself
(e.g., floors, walls, or drains). A lack of Listeria control in a
packinghouse can be identified through environmental sampling
when the same sites within a packinghouse are repeatedly
positive. Through further subtyping (e.g., using pulsed
field gel electrophoresis or whole genome sequencing) of
the Listeria present in " repeat positive " sites, two scenarios
can be identified: (i) " persistent Listeria " and (ii) " persistent
transient Listeria. " " Persistent Listeria " refers to the Listeria
not removed from the packing environment (e.g., through
cleaning and sanitation, facilitated by proper sanitary design
of equipment), allowing it to survive and replicate over time
and facilitating its spread in the packing environment as
well as possible contamination of finished product (16). On
the other hand, " persistent transient Listeria " describes the
scenario when the same sites within the packing environment
are continuously positive but not necessarily with the same
subtype of Listeria (e.g., due to continuous re-introduction of
Listeria from the same sources) (4). Direct traceback of product
contamination to persistent transient Listeria populations
is more difficult compared to persistent Listeria populations
because of the larger number of subtypes present. However,
similar to persistent Listeria, persistent transient Listeria can
still lead to product contamination and subsequent recalls
and illnesses. There is a third scenario referred to as " transient
Listeria, " which refers to the Listeria that enters the processing
environment but is eliminated through routine cleaning
and sanitation activities.
To avoid recalls and outbreaks it is necessary to identify sites
of persistent Listeria and persistent transient Listeria within
the packing environment and to subsequently implement
corrective actions that eliminate contamination. However,
only performing superficial " corrective " actions (e.g., re-cleaning
and sanitation) may not truly eliminate contamination,
leading to recurrence of contamination linked to the same root
cause (e.g., an introduction vector that was not addressed).
Therefore, identifying the root cause of the contamination or
persistent Listeria in the packing environment is essential (36).
As such, this study aimed to develop, implement, and test a
protocol for performing root cause analysis (RCA) to identify
interventions to eliminate Listeria. While the study reported
here used an apple packinghouse as a model system, the RCA
protocol and procedures will be broadly applicable to different
produce and food processing operations.
556 Food Protection Trends November/December
MATERIALS AND METHODS
Packinghouse characteristics and study design
An apple packinghouse in the northeastern U.S. was
investigated in this case study to evaluate a root cause analysis
(RCA) procedure for reducing or eliminating Listeria in
produce operations. The packinghouse is approx. 25,000 ft2
(approx. 2,300 m2
), has a single packing line, and runs from
September to May each year. The packinghouse is regulated
under the U.S. FDA rule for preventive controls for human
food (1), as >50% of apples they pack come from growers not
under their management; the packinghouse is not located on
a primary production farm (2). The packinghouse performed
daily dry cleaning (i.e., removal of leaves and debris from
the equipment and floor) and performed full " wet " cleaning
and sanitation weekly. The same employees who worked
on the line during production also performed cleaning and
sanitation activities.
Initial data on Listeria detection in the same packinghouse
investigated in the case study reported here was reported by
Sullivan and Wiedmann (33), who designated this facility as
" packinghouse A. " This previously reported data was utilized
in the current study (i) as proof of Listeria presence in the
packinghouse, (ii) for the identification of sampling sites with
a higher likelihood of being positive for Listeria, and (iii) as
evidence in the RCA. In addition to this previously collected
data, sample collection was also performed as part of the
current study to test the effectiveness of the interventions.
In the current study, root cause analysis was performed
to help identify interventions for reducing or eliminating
persistent Listeria in the packing environment. To test the
effectiveness of selected interventions, sampling of the
packinghouse environment was performed before and after
intervention implementation (see Fig. 1 for a timeline of
sampling and intervention implementation).
Root cause analysis and intervention implementation
RCA was performed using a fishbone diagram and the " 5
why's procedure, " utilizing the procedure recently described
by Belias and Wiedmann (4). RCA was performed in a 1.5 h
meeting with the packinghouse manager, the quality assurance
manager, the maintenance manager, and two members
from the Cornell team (i.e., the RCA team) on October
25th, 2019. Briefly, a pre-constructed fishbone diagram was
utilized as a brainstorming tool in the RCA (Fig. 2); this
fishbone diagram was adapted from Belias and Wiedmann
(4) and modified to be specific to produce operations (i.e.,
packinghouse and processing facilities). There are 7 major
bones in the fishbone diagram that represent high-level
categories that can lead to Listeria problems: (i) company
practices/ food safety culture, (ii) personnel, (iii) facilities,
(iv) cleaning and sanitation, (v) produce introduction, (vi)
packinghouse equipment, and (vii) produce processing
equipment. The apples were not further processed, so the
major bone " vii: produce processing equipment " was deemed
Food Protection Trends - November/December 2021

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