Food Protection Trends - March/April 2023 - 128

HARVESTING EQUIPMENT
Current cleaning and sanitation practices
Routine cleaning and sanitizing of harvesting and field-packaging
or packing utensils, tools, and equipment (which typically
is conducted daily) are practiced by fresh produce harvesting
operations as an essential component of good agricultural
practices (36, 62, 80, 179). Studies investigating cleaning and
sanitizing techniques for various types of equipment used in
food processing and manufacturing facilities are plentiful in the
literature. However, publicly available evaluations of cleaning
and sanitizing methods and techniques for equipment used
to harvest and pack produce in the outdoor field setting are
limited. Most published information describing cleaning and
sanitizing methods for harvesting equipment comes from the
cooperative extension system operated through U.S. land grant
universities in partnership with federal, state, and local governments
(25, 76, 131, 143, 153). Many of these resources provide
valuable, practical information and guidance on choosing a
sanitizer product and appropriate product concentrations,
mixing and applying chemical sanitizers, verifying labeled or
selected doses, calibrating application equipment, and identifying
niches and difficult-to-access equipment areas that may
harbor pathogens.
Current routine cleaning and sanitizing practices for
harvesting equipment generally follow a four- or five-step
process and may occur in the cropped field itself or, in some
cases, on perimeter farm roads. Cleaning includes activities
such as removal of debris and residual cull product; application
of cleaning agents (e.g., detergents); brushing, scrubbing,
or wiping; and medium- to high-pressure spraying with
water multiple times (141). Solutions used during cleaning
activities may include detergents, surfactants, water conditioners,
and sanitizers or disinfectants (25, 131, 141, 143,
153). Routine cleaning activities typically focus on visible
and readily accessible surfaces that have direct contact with
product or are adjacent to product-contact surfaces (20).
Within the context of this review, adjacent areas on harvesting
equipment include many locations, especially on mobile
harvesting and field-packing equipment, that are in close
proximity, next to, or above food-contact surfaces during
actual harvest operations, during preoperational staging, or
during location-to-location movement. Examples include
support footings, ladders next to conveyors, and various
hoses and quick-connect couplers. During movement, staging
at fields, and daily harvest operations, these surfaces are
often sites of soil accumulation and may be very close to or
overhang food-contact surfaces. At the end of each harvest
pass within a field, the rough ground and rocking motion of
the harvest unit as it maneuvers may cause this soil and crop
residue to fall onto food-contact areas. On occasion, the forces
on the structure may also be strong enough to cause water
that is trapped in hollow spaces and may contain Listeria to
leak out and potentially contaminate these surfaces during a
daily operation.
128 Food Protection Trends March/April
Harvesting equipment cleaning is typically followed by
sanitizing of food-contact and adjacent non food-contact
surfaces, which may or may not be followed with a final
rinse. " To sanitize " is defined in the U.S. Code of Federal
Regulations (35) as " to adequately treat food-contact
surfaces by a process that is effective in destroying vegetative
cells of microorganisms of public health significance, and
in substantially reducing numbers of other undesirable
microorganisms, but without adversely affecting the product
or its safety for the consumer. " Following cleaning, harvesting
equipment is sanitized by spraying or wiping with chemical
sanitizers such as ammonium- or chlorine-based products.
Nonchemical methods such as UV light and thermal
techniques may also be used to sanitize equipment surfaces
(118, 141, 143) but are not typical for mechanized harvesting
and mobile field-packing equipment, including robotic
harvest aides.
In addition to harvesting in the outdoor environment,
cleaning and sanitizing of food-contact surfaces and adjacent
areas on harvesting equipment also play prominent roles in
food safety for produce grown in hoop or shade houses and
in controlled environment agriculture facilities. Following a
Salmonella Typhimurium outbreak at a controlled environment
agriculture operation in summer 2021, in their investigation
report the FDA (169) recommended improved
procedures for cleaning and sanitizing equipment. Research
conducted in shade-house produce production operations
investigated bacterial transfer from contaminated produce
crops to bins and clippers used in harvesting, and bacteria
were recovered from bins and clippers up to 8 days after
inoculation (127). Because of the indoor setting, controlled
environment agriculture systems do not have the benefit
of UV light exposure and may require enhanced vigilance
during cleaning and sanitation of harvesting equipment to
avoid contamination.
Pathogens posing a contamination risk to harvesting
equipment in the field
Numerous studies of human pathogens in various produce
growing regions have revealed their presence and, in some
instances, persistence in produce growing environments (1,
12, 38, 64, 66, 68, 154, 155, 163, 178, 190). In their review
of foodborne illness outbreaks occurring from 2010 through
2017, Carstens et al. (28) reported 228 outbreaks, 85 of
which were multistate outbreaks in which fresh produce
was the confirmed source of contamination. Pathogenic
bacteria involved in the multistate outbreaks attributed to
fresh produce consumption included Shiga toxin-producing
Escherichia coli (STEC), Salmonella, and L. monocytogenes
(28). Of these three pathogens, L. monocytogenes is of major
concern because of its ubiquitous presence and ability to
survive and grow in the agricultural environment under
conditions that are hostile to competing microorganisms
(i.e., low water activity, wide pH range, and low temp
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