Semester of Graduation

Fall, 2024

Degree

Master of Science (MS)

Department

School of Nutrition and Food Sciences

Document Type

Thesis

Abstract

Biological Soil Amendments of Animal Origin (BSAAOs) provide essential nutrients for plants but are an ideal growth environment for foodborne pathogens. Silver nanoparticles (AgNPs) have become promising antimicrobial agents that could reduce the presence of food-borne pathogens on the surface of produce. This study evaluated the effect of using composted or raw manure soil amendments on the quality and safety of sweetpotatoes (variety Orleans), additionally the antimicrobial effectiveness of AgNPs was evaluated to reduce E. coli O157:H7 from the surface of sweetpotatoes. The field treatments included composted cow manure (CM), raw manure (RM), or no-BSAAO application (NB), with each treatment applied either through tilling or no-tilling. Soil samples were collected during weeks 1, 3, 5, 10, and 15. Prior to being harvested on weeks 17, and 18, plots were contaminated with Nalidixic acid-resistant (50 µg/mL) E. coli (6 Log CFU/mL) via irrigation. Sweetpotatoes with soil and without soil, were spot inoculated with 200 mL of GFP-tagged ampicillin-resistant E. coli O157:H7 (8 Log CFU/mL) and were washed with silver nanoparticles at concentrations (5, 10, 15 ppm) for 5 and 10 minutes. In RM plots, E. coli levels were higher after BSAAO application in week 1 (1.44 log CFU/g) and in week 3 (1.59 log CFU/g). Plots with RM no-till had the highest E. coli levels during weeks 1 (1.51 log CFU/g), 3 (1.59 log CFU/g), and 15 (1.42 log CFU/g). AgNPs at concentrations of 10 and 15 ppm were significantly (PE. coli O157:H7 levels (>1.73 Log CFU/cm2) on sweetpotatoes without soil compared to other concentrations. E. coli can persist in no-till RM treatments throughout the sweetpotato crop cycle. The Orleans sweetpotato variety produces high-yield marketable sweetpotatoes regardless of BSAAO applications. Silver nanoparticles were effective (AgNPs) in reducing E. coli O157:H7 on the surface of sweetpotatoes. The concentration of AgNPs and the presence of organic matter are key factors that significantly influence their antimicrobial effectiveness.

Date

10-29-2024

Committee Chair

Adhikari, Achyut

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Available for download on Friday, October 29, 2027

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