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Access Type
WSU Access
Date of Award
January 2023
Degree Type
Thesis
Degree Name
M.S.
Department
Nutrition and Food Science
First Advisor
Yifan Zhang
Abstract
Understanding growth kinetics of pathogenic foodborne bacteria is important to prevent foodborne illness. This study focuses on the behaviors of Salmonella typhimurium, Salmonella enteritidis and Listeria monocytogenous on freshly chopped tomatoes, cucumbers, and romaine lettuce. Bacteria were grown in Tryptic Soy Broth for 24 hours, followed by serial dilution before inoculation on freshly chopped vegetables. One hundred microliters of diluted bacteria suspension were inoculated onto 5 grams of each vegetable sample. Samples were then stored in clean Ziploc bags at room temperature to emulate leaving prepackaged salads on countertops or kitchen tables. Bacteria concentration was determined using the plate-count technique. After 0-, 2-, 4-, and 24-hour time intervals for each bacterium and vegetable sample. The concentration of Listeria monocytogenous decreased by 0.28 log after 24-hours on romaine lettuce (p = <0.01) Also, the population of Salmonella enteritidis on tomatoes dropped to zero after 24-hours at room temperature (p = 0.029). The remaining bacteria-sample combinations showed increasing microbial growth (p = <0.01) after 24-hours. The data suggests that chopped vegetables alone do not contribute to preventing foodborne pathogens from proliferating at room temperature. Additional food safety measures such as refrigeration, cleaning, and heating are needed to control microbial populations on food.
Recommended Citation
Alasadi, Mohamad, "Growth Kinetics Of Salmonella Spp. And Listeria Monocytogenes On Freshly Chopped Vegetables" (2023). Wayne State University Theses. 909.
https://digitalcommons.wayne.edu/oa_theses/909