Food Protection Trends - November/December 2024 - 401

of high-tech operations which include common activities
linked to the production of fruit, vegetable and herbs (FVHs)
(e.g., seeding, irrigation, harvesting). An increasing number
of CEA facilities also include processing and packaging
operations. Operations such as cutting, washing and packing,
which were usually performed in fresh-cut processing plants,
thus are now performed within the CEA facilities, in the
same room or adjoining rooms where the crops are grown
(37).
Hydroponics is the technique of growing plants using a
water-based nutrient solution and can include an aggregate
substrate or growing media such as vermiculite, coconut coir,
perlite or peat moss (46, 54, 56). Hydroponics differ from
traditional soil cultivation methods in that the water is the
primary nutrient carrier as opposed to soil; the structural
support is offered through the aforementioned substrate or
growing media instead of soil. The most common types of
FVH commodities cultivated under soilless practices are
tomatoes, peppers, lettuce, and other leafy greens, including
microgreens. Hydroponics include many different types of
cultivation systems such as deep-water culture hydroponics,
aeroponics, and aquaponics (71). Deep-water culture is
where seedlings are planted into floating rafts so that the
roots are immersed in deep, recirculating nutrient rich
" ponds. " In aeroponics, the roots of the plants are suspended
in the air, and water and nutrients are supplied to the plant
through a fine mist activated by a timer. Indoor aquaponic
systems combine plant production with fish cultivation, using
treated water from the fish tanks as a source of irrigation
water to grow plants (51). While hydroponics is inherently
different from soil-based methods, the overall primary inputs
for both methods, which are all relevant to food safety,
remain generally similar. These primary inputs include
plant seeds, water, nutrients/fertilizers, soil (for traditional
methods) and substrates (for soilless methods) (18). Other
food safety relevant factors in CEA production include
lighting, structural systems and climatic factors (e.g., oxygen,
humidity, and carbon dioxide levels) (18, 38).
Lighting systems involved in CEA cover a wide range.
Traditional methods utilize sunlight, as commonly seen in
greenhouses (10). On the other end of the spectrum are
vertical farms where layers of crops are stacked on top of
one another, each layer with its own set of lights (typically
light emitting diodes [LEDs]) on the bottom of the above
structure (23). This allows for precise dosing of lights, and
often very defined amounts of red, blue and white light are
utilized to increase plant production (42).
Finally, there can be numerous combinations between
light and cultivation systems, each combination affecting the
structure within the greenhouse/farm. Both hydroponics
and traditional soil-based cultivation can be applied into a
flat, one tier system using sunlight (36). Hydroponics can
also be applied into a multi-level vertical farm using synthetic
lights (23). It is unlikely that traditional soil methods will be
combined with vertical farming as the weight of the soil poses
a challenge for the structure to support. Two commonly seen
types of CEA facilities are high tech vertical hydroponic farms
utilizing LED lights and middle to low tech hydroponic horizontal
farms utilizing sunlight. The latter system, which includes
a hydroponic system, with several automated stages of the
whole process (e.g., transport of trays/beds from the seeding
room to the greenhouse and from the greenhouse to the harvest
area), is becoming increasingly popular (37). While this lower
tech version may not have full climatic control, it might reduce
the initial investment, making it attractive for firms (36).
The range of practices in which environmental factors
such as temperature, light, humidity, oxygen, and carbon
dioxide are controlled can often be tied with the maturity
of the data collection infrastructure. On one end of the
spectrum, some facilities have tight control with constant
measurements, allowing for precise changes to be made. On
the other end are greenhouses with no formal data collection.
In this instance, changes to the environment are based on
knowledge from a grower. This poises some facilities to be
more easily adapted to the use of AI technology than others,
based on their data collection infrastructure.
OVERVIEW OF CEA FOOD SAFETY CHALLENGES
CEA is often framed as reducing or even eliminating
traditional microbial food safety hazards due to the physical
protection of the crop from the environment (57), which is
expected to lead to a lower likelihood of the edible part of
the produce being in contact with wild animals and animal
feces (40). Supporting this, several authors have found lower
total bacterial counts and lower microbiota diversity in crops
grown in CEA systems compared to those grown in open
fields (32, 75). However, CEA clearly cannot produce products
with " zero risk " of causing microbial or other food safety
issues (78) and typical foodborne pathogens and perhaps
unknown or waterborne pathogens are still a possible issue.
Likely microbial food safety challenges in CEA include (i)
pathogen contamination of inputs (e.g., seeds, substrates),
(ii) pathogen contamination and persistence in water and
water associated infrastructure, (iii) pathogen contamination
and persistence in the overall facility infrastructure (e.g.,
conveyor belts, harvest equipment, trays/beds, floors), and
(iv) risk of pathogen transfer throughout the system; due to
the interconnectivity of hydroponics via water and general
lack of full system sanitation, there is the regulatory issue of
lot separation. Food safety risks in CEA are supported by a
salmonellosis outbreak in the US in 2021, which was linked
to CEA (specifically hydroponically) grown prepackaged salads
(14). While the outbreak strain was not recovered from
inside the facility (it was found in an " outdoor storm water
drainage pond beside the farm " (14), the investigation of this
outbreak did detect another Salmonella strain (serovar Liverpool)
in an indoor pond that was used to grow lettuce. This
illustrates that Salmonella represents a hazard that needs to be
November/December Food Protection Trends 401
Food Protection Trends - November/December 2024

Table of Contents for the Digital Edition of Food Protection Trends - November/December 2024
