Manipulation of growth conditions for microgreen production of leafy vegetables and herbs for improved nutritional quality and food safety

Commodities

• Vegetables: beets, broccoli, other
• Additional Plants: herbs

Practices

• Crop Production: greenhouses
• Production Systems: organic agriculture

Microgreens are a valuable specialty crop that farmers have
profited from in recent years as they have increased in
popularity. While being packed with high levels of nutrients and
bioactive compounds, there is concern that microgreens could
emerge as a susceptible product for contamination by foodborne
pathogens. Being young seedlings and a perishable product,
foodborne pathogens that may be present would rapidly multiple to
infectious levels due to the high level of exuded nutrients. The
risk is also indicated by the number of recalls for possible
contamination with the enteric pathogens Salmonella
enterica and Listeria monocytogenes. There is
an opportunity to mitigate this susceptibility by exploring the
interaction between elicitation of plant secondary metabolites in
microgreens via abiotic stress application and their impact on
microgreen quality and food safety. This study, therefore, will
examine the potential improvements to food quality, nutritional
content, and food safety in microgreens via abiotic elicitation
through cold and UV stress. The goal of this research project is
to provide a more nutritious, longer lasting, and safer product
that farmers can easily grow on a small scale.

The goal of this project is to investigate the efficacy of
regulated abiotic stress as an elicitor of plant secondary
metabolites on plants grown under controlled environments to
improve extranutritional properties, food safety and post-harvest
quality (shelf-life). Using sustainable approaches, I aim to
manipulate UV-exposure and apply cold stress to microgreens to
produce a more nutritious, safer and longer lasting product.
Microgreens nutritional quality declines rapidly post-harvest
which could be problematic from both a food safety and
extranutritional standpoint. Once microgreens are harvested, they
rapidly exude nutrient-rich fluid, wilt and can quickly decay,
potentially favouring enteric pathogen persistence (Turner et
al., 2020). This project will attempt to address these shortfalls
in microgreen production.

The objectives of this project are:

1. Improved nutrition and quality: Assess a)
   the effect of exposure to UV or cold stress on secondary
   metabolite accumulation in microgreens of leafy vegetables and
   herbs, and b) retention of nutritional quality
   post-harvest and packaging.

Utilizing controlled environments, I will expose seedlings to
abiotic factors such as cold temperature and UV irradiation to
improve microgreen phytochemical profiles and quality
post-harvest. Secondary metabolites which are typically
indicative of improved nutritional value such as total phenolics,
total flavonoids, carotenoids, chlorophyll, betalain alkaloids
(red beet-leaf group only) anthocyanins (red varieties non-leaf
beet group), glucosinolates (Brassica spp. only) and
vitamin C will be measured. Rate of decline of major
phytochemical groups will be measured over a one-week period
post-packaging.

2. Improved food safety: Evaluate the effect
   of phytochemical manipulation via abiotic stress application on
   foodborne pathogen association with microgreens.

Seeds of different microgreens will be inoculated with the
foodborne pathogens Salmonella, Listeria monocytogenes
and STEC, which will then be grown under conditions which shift
phytochemical levels. I will measure the persistence and transfer
of foodborne pathogens in the phyllosphere of microgreens at low
concentrations, over a period of 5 days post-harvest. Enteric
pathogens retrieved will be enumerated by spread plating or Most
Probably Number (MPN) method.

3. Integrated food safety and sustainability:
   Assess the food safety implications of various growth media
   for microgreen production.

The effect of substate type on the persistence of foodborne
pathogens will be evaluated. Inoculated seeds of microgreens will
be grown as outlined in objective 2 on either a) soil mix, b)
biodegradable Jute fibre, and c) non-biodegradable rockwool mats.
The level and persistence of foodborne pathogens remaining in the
substate will be evaluated for a period of 4 days.