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Moodispaw Thesis 4.22.22 Final.pdf (8.47 MB)

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Establishing Science-based Strategies for Prevention and Mitigation of Human Pathogens in Leafy Greens Grown in Nutrient Film Technique (NFT) Hydroponic Systems

Moodispaw, Margaret Rose
http://orcid.org/0000-0003-3371-2015
http://rave.ohiolink.edu/etdc/view?acc_num=osu1650622577802721

Abstract Details

2022, Master of Science, Ohio State University, Human Ecology: Human Nutrition.
Hydroponic vegetable production is increasing globally, specifically leafy greens. There are few science-based recommendations to ensure food safety of hydroponic lettuce. There is limited evidence for establishing water management strategies and no validated sanitation protocols to ensure elimination of human pathogens. The first objective was to determine the survival of Listeria monocytogenes and Salmonella Typhimurium in nutrient film technique (NFT) systems during the lifecycle of lettuce under sporadic and extreme contamination events. The second objective was to determine effectiveness of sanitizers to mitigate Salmonella Typhimurium on contaminated hydroponic surfaces. Nutrient film technique systems were inoculated with L. monocytogenes or Salmonella Typhimurium simulating sporadic (~1x104 CFU/mL) and extreme (~1x107 CFU/mL) contamination conditions. Nutrient solution, rockwool, roots, and leaves were collected at seven time points during the lettuce lifecycle for pathogen detection and enumeration. To determine sanitizer effectiveness, commercial hydroponic surfaces (ABS plastic embedded with UV inhibitors, food grade ultraviolet (UV) stabilized polyvinyl chloride (PVC), and PVC) were inoculated with Salmonella Typhimurium (~1x104 CFU/mL) and treated with common greenhouse sanitizers. After treatment, surface swabs were collected from the edges and corners, and the pathogen was enumerated. Both pathogens persisted in NFT systems throughout the growth cycle. Listeria monocytogenes and Salmonella Typhimurium concentrations were consistently high in rockwool/root (0.94±1.15 Log CFU/g – 4.35±1.23 Log CFU/g; 0.88±1.27 Log CFU/g – 6.58±0.40 Log CFU/g) samples compared to nutrient solution (0.05±0.18 Log CFU/mL – 5.71±0.23 Log CFU/mL). Both pathogens were detectable on lettuce leaves throughout the growth cycle. The sanitizers Zerotol (rate/contact time; 5%/10min), SaniDate12.0 (200ppm/5min), Virkon (1%/10min), KleenGrow (2%/10min), and GreenShield (5%/10min) eliminated Salmonella Typhimurium (100% reduction) from all surfaces. SaniDate12.0 (100ppm/5min) eliminated the pathogen from ABS plastic embedded with UV inhibitors (water reservoir) and food grade UV stabilized PVC (channel top/bottom). Salmonella Typhimurium was recovered from PVC (2.91±0.30 Log/cm2). Sodium hypochlorite (100ppm/200ppm/10min) and aqueous chlorine dioxide (10ppm/50ppm/10min) achieved limited reduction (72.07-97.55%). Sodium hypochlorite and aqueous chlorine dioxide were statistically identical to the water control. Chlorine was least effective on food grade UV stabilized PVC, which commonly contacts edible portions of crops. We demonstrated that pathogens from nutrient solution can readily cross-contaminate leafy greens in NFT systems (10-100%). L. monocytogenes and Salmonella Typhimurium survive in NFT systems throughout the lettuce growth cycle, highlighting risks from foodborne disease. Both pathogens persist in highest amounts in root-rockwool matrix, posing additional risks for consumers of living lettuce. Enhanced irrigation water quality standards are necessary to prevent foodborne illnesses. Salmonella Typhimurium can be eliminated from commercial hydroponic surfaces using Zerotol (5%), Virkon (1%), KleenGrow (2%), GreenShield (5%), and SaniDate 12.0 (200ppm) when applied for label recommended contact times. Virkon, KleenGrow, and GreenShield are not approved for food use. Although all sanitizers achieved at least a 3 Log reduction in pathogens, sodium hypochlorite (100ppm, 200ppm), aqueous chlorine dioxide (10ppm, 50ppm), SaniDate 12.0 (100ppm) were not effective in eliminating Salmonella Typhimurium from materials. Ineffectiveness of chlorine-based sanitizers in ridding surfaces of pathogens is concerning due to widespread use in industry. These findings are critical in the development of food safety guidelines for hydroponic growers.
Sanja Ilic (Advisor)
Melanie Lewis Ivey (Committee Member)
Ouliana Ziouzenkova (Committee Member)
145 p.
Agriculture; Biology; Microbiology; Nutrition; Plant Pathology; Sanitation
Food safety; hydroponics; hydroponic production; nutrient film technique (NFT); leafy greens; contamination; nutrient solution; surface sanitation; human pathogens; foodborne illness; Salmonella Typhimurium; Listeria monocytogenes

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Citations

  • Moodispaw, M. R. (2022). Establishing Science-based Strategies for Prevention and Mitigation of Human Pathogens in Leafy Greens Grown in Nutrient Film Technique (NFT) Hydroponic Systems [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650622577802721

    APA Style (7th edition)

  • Moodispaw, Margaret. Establishing Science-based Strategies for Prevention and Mitigation of Human Pathogens in Leafy Greens Grown in Nutrient Film Technique (NFT) Hydroponic Systems . 2022. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1650622577802721.

    MLA Style (8th edition)

  • Moodispaw, Margaret. "Establishing Science-based Strategies for Prevention and Mitigation of Human Pathogens in Leafy Greens Grown in Nutrient Film Technique (NFT) Hydroponic Systems ." Master's thesis, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650622577802721

    Chicago Manual of Style (17th edition)

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