Date of Award

Fall 12-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Food Science

First Advisor

Rosalee Hellberg, Ph.D.

Second Advisor

Lillian Senger, Ph.D.

Third Advisor

Anuradha Prakash, Ph.D.

Abstract

Foodborne pathogens, including Escherichia coli, Salmonella enterica, and Listeria monocytogenes, are major causes of gastrointestinal disease globally. The Contamination Sanitization Inspection and Disinfection (CSI-D) device is a new handheld fluorescence-based imaging system designed to disinfect food contact surfaces contaminated with microorganisms using ultraviolet-C (UVC) illumination. This study aimed to determine the optimal parameters for the disinfection of foodborne bacteria using the CSI-D device. The following bacterial strains were tested: generic E. coli; enterohemorrhagic E. coli (EHEC) O157:H7; enterotoxigenic E. coli (ETEC) O78:H11; S. enterica serotypes Enteritidis, Newport, Typhimurium, and Javiana; and L. monocytogenes serotypes 1/2a, 1/2b, and 4b. Each bacterial strain was spread-plated on non-selective agar and exposed to high-intensity (10 mW/cm2) or low-intensity (5 mW/cm2) UVC for 1 s, 3 s, or 5 s or were not exposed to UVC (control). The plates were then incubated overnight at 37℃ and the resulting colonies were counted. Three trials for each bacterial strain were conducted on separate days. The average of the trials showed that exposure time of 3-5 s at either intensity (high: 10 mW/cm2 or low: 5 mW/cm2) resulted in effective and consistent inhibition of E. col, S. enterica, and L. monocytogenes growth. The minimum reduction at 3 s and 5 s exposure for both intensities was 99.95-100% for E. coli, 98.36-100% for S. enterica, and 99.24-100% for L. monocytogenes. The 1 s exposure time resulted in lower efficiency in reducing bacterial growth, with survival rates of 0.48-6.95% for E. coli, 0.29-17.40% for S. enterica, and 1.95-31.8% for L. monocytogenes. The results of this study show that, in pure culture conditions, exposure to UVC with the CSI-D device for at least 3 s is required to achieve 98-100% reduction of E. coli, S. enterica, and L. monocytogenes.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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