Microgreen Pathogen Susceptibility Dependent on Plant Variety, Growing Media
The Problem
There are gaps in the knowledge of microgreen production.
Microgreens are immature seedlings of edible plants and are becoming popular in raw meals, like salads. Like other produce, microgreens can cause foodborne illness outbreaks, but little research has been done to evaluate the specific food safety risks of microgreen production.
Contaminations of salad greens are common, and the results can be deadly. A recent outbreak involved 18 illnesses, resulting in 16 hospitalizations and three deaths.
The Work
Kristen Gibson, professor of food safety and microbiology for the Arkansas Agricultural Experiment Station and director of the Center of Food Safety, and other researchers tested the potential for pathogen growth during a microgreen’s 10-day growing cycle.
The researchers tested the two most popular microgreen varieties based on data from a survey they conducted. They grew the two varieties on growing mats and on peat with vermiculite. Half of the alternative soil area was left without plants to also test virus persistence without the presence of microgreens.
To test the virus persistence on the edible tissue, the Tulane virus, a norovirus surrogate, was added to the soil alternatives on day zero. To test contamination closer to harvest, the researchers also inoculated the soil alternatives with Tulane virus on day seven.
The researchers tested virus persistence on the leaf surface through direct inoculation three days before harvest time.
Wenjun Deng, who received her Ph.D. in July 2021, participated in the research, using funds from a University of Arkansas Graduate-Professional Student Congress research grant to support the experiment.
Gina Misra, another researcher on this project who owns a microgreen operation in Delaware, introduced the idea to Gibson after realizing the gaps in knowledge about microgreen production.
Adam Baker, a post-doctoral fellow, helped conduct the research as well.
The Results
The Tulane virus was able to persist on the leaf surface and in the soil during the 10-day growing cycle.
In the soil alternatives, the virus count dropped from 10 million to 100,000 viruses per plant.
Virus persistence on the edible parts might be dependent on leaf structure. Pea shoots microgreens had 50,000 viruses per plant, and the sunflower microgreens had six viruses per plant.
The virus levels from the lab are not like those found in an actual production environment — contamination is normally at very low levels.
The Value
Human noroviruses are the No. 1 cause of foodborne illness in the United States and cause sickness in about 20 million people each year, according to an article on the Centers for Disease Control and Prevention. Food service workers infected with norovirus cause 70% of outbreaks from contaminated food.
Microgreen growers typically consist of smaller operations that might not have the resources to follow the testing standards of larger operations. It is not always feasible for some to regularly test for contamination.
With this new characterization of microgreen production, Gibson can begin to develop realistic food safety protocols for smaller operations in the hopes of reducing the possibility norovirus outbreaks originating from microgreens.
Gibson is also exploring sanitizing products for use on edible tissue and is considering testing other popular microgreen varieties and possibly other microorganisms. She wants to see how other viruses and bacteria interact with each other in the soil alternatives.
The Funding
This project was funded through a University of Arkansas Graduate-Professional Student Congress research grant.
About the Researcher
Kristen Gibson
Professor of Food Science
Director, Center for Food Safety
- B.S., Microbiology, University of Central Florida, Orlando
- Ph.D., Environ Engineering, John Hopkins University, Baltimore
Gibson’s research focuses on pathogen interaction within food systems, including handling and processing. She specializes in investigating human noroviruses and food safety related to fresh produce and retail outlets. Gibson has received many nationally competitive grants.
Wenjun Deng
Assistant Professor at Qingdao University in China
- B.S., Food Quality and Safety, Shannxi Normal University
- M.S., Food Safety, Wageningen University and Research
- Ph.D., Food Science, University of Arkansas
Deng is an assistant professor at Qingdao University in China. Her research is focused on food safety and pathogen transfer.
Adam Baker
Postdoctoral Researcher
- B.S., Biology, University of Arkansas – Fort Smith
- M.S., Food Science, University of Arkansas
- Ph.D., Food Science, University of Florida
Baker is a postdoctoral researcher at the University of Arkansas. His research focuses on pathogen survival and transmission in food systems.
Gina Misra
Affiliate Research Scientist at Blue Marble Space Institute of Science
Editor-in-chief of Sciworthy
- Associates degree, Biology, University of Central Florida
- B.S., Nutrition, Penn State University
- M.S., Cell and Molecular Biology, University of Arkansas
Misra is an affiliate research scientist at Blue Marble Space Institute of Science and editor-in-chief of Sciworthy. She owns a microgreen operation in Delaware. Her research focuses on transmission in food systems, food safety, and food safety and plant interactions in space.