Date of Graduation
12-2025
Document Type
Thesis
Degree Name
Master of Science in Food Science (MS)
Degree Level
Graduate
Department
Food Science
Advisor/Mentor
Acuff, Jennifer
Committee Member
Gibson, Kristen
Second Committee Member
Robinson, Samantha
Keywords
Dehydration; Escherichia coli; Freeze Drying; Listeria; Microgreens; Salmonella
Abstract
Microgreens are increasingly popular among consumers due to their high nutritional value. However, their limited shelf-life remains a significant challenge. To extend their usability, small-scale growers increasingly apply home preservation methods like warm air drying or freeze-drying. However, the effects of these methods on common foodborne pathogens are not well understood. Radish and alfalfa microgreens were inoculated with cocktails of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes 4b (ca. 8.0 log CFU/g). Treatments included dehydration in a commercial dehydrator, freeze-drying (-20°C, 24 h), and convective drying in an oven (60°C for 4 h), and convective drying in an oven (60°C for 1 h) with or without a 1.7% citric acid pretreatment (10 min dip). Microbial populations (log CFU/g) were measured immediately post-treatment; color readings were obtained through a spectrophotometer for pre- and post-treated microgreens to determine changes (ΔE). Results showed that oven drying and freeze-drying alone achieved minimal pathogen reduction (< 1 log on average), consistent with literature on low-moisture foods. In contrast, the citric acid + oven treatment produced substantial inactivation. Average pathogen reductions on radish microgreens were ~5.6 log CFU/g for E. coli O157:H7, ~5.4 log CFU/g for Salmonella enterica, and ~4.6 log CFU/g for L. monocytogenes. Corresponding reductions on alfalfa microgreens were ~4.4, ~4.8, and ~3.5 CFU/g, respectively However, these samples suffered significant quality loss (ΔE >40), whereas freeze-dried samples retained color (ΔE< 10). These findings suggest that freeze-drying preserves visual quality but does not ensure microbial safety, while acid-assisted drying substantially improves kill rates at the expense of noticeable color changes. Future work should optimize pretreatment formulations and explore hurdle approaches to safely extend microgreen shelf life.
Citation
Sananikone, T. S. (2025). Micro-greens, not Micro-yellows: Evaluating Dehydration-Based Preservation Techniques for Reducing Foodborne Pathogens and Quality Preservation on Microgreens. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6095
