Semester of Graduation

Summer 2018


Master of Science (MS)


The School of Nutrition and Food Sciences

Document Type



Rainfall and flooding have impacted the strawberry industry in Louisiana. Floodwater is an ideal medium for microbiological growth and may cause contamination of soil, agricultural water, and fresh produce with foodborne pathogens. This research aimed to evaluate the microbial safety and quality of strawberries after flooding. Three strains of generic Escherichia coli were used to establish a baseline population of approximately 106 CFU/L (high contamination) and 102 CFU/L (low contamination) in floodwater. Five raised beds were filled with water to simulate a flooding event. Simulated floodwater was mixed with cow manure and spiked with generic E. coli then applied to strawberry plants. Treatments included High Flooding High Contamination (HFHC), High Flooding Low Contamination (HFLC), Low Flooding High Contamination (LFHC) and Low Flooding Low Contamination (LFLC). One bed served as the control (C). Strawberry plants were flooded for 4 h and sampled at the time of harvest and during shelf life at 4°C for 48, 96, and 144 h. Soil samples were collected on site for one week. The population of foodborne pathogens and microbial indicators was evaluated. Strawberry quality (yeast and mold count, color, and texture) was also evaluated. Results indicated that the presence of E. coli O157:H7 and Listeria monocytogenes in strawberries, soil, and foliage was not detected. Additionally, generic E. coli was not detected (/g) in strawberry fruit or in foliage samples. In soil samples, generic E. coli was higher in HFHC samples (1.61 log CFU/g) compared to HFLC samples (1.09 log CFU/g) at harvest. However, generic E. coli was not detected after 96 h (/g) in soil samples. Significant levels of coliform were present in the strawberry fruit and soil at 0, 48, 96, and 144 h in all treatment beds. Yeast and mold were detected in all samples but with no clear trend throughout shelf life across all floodwater treatments. Moreover, results did not indicate clear correlation among flooding and contamination levels and color and texture change. This study provides local growers science-based information to understand potential effects of flooding on the microbial safety and quality of fresh produce.



Committee Chair

Xu, Wenqing



Included in

Food Science Commons