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

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Commodities

• Vegetables: beets, broccoli
• 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.