Doctor of Philosophy (PhD)


School of Nutrition and Food Sciences

Document Type



Escherichia coli O157:H7, Salmonella sp., and Listeria monocytogenes have been linked to foodborne outbreaks in produce. The most recent outbreaks in produce have been associated with irrigation water due to infiltration of well water or water run-off from contaminated sources. The Food Safety Modernization Act (FSMA) requires all irrigation water to be safe for use on produce, as a strategy to reduce foodborne illnesses. A surfactant modified zeolite (SMZ) filtration system could provide produce farmers with a sustainable low-cost system for high-quality and safe irrigation water. The objective of this study was to evaluate the effectiveness of hexadecyltrimethylammonium bromide (HDTMABr) to develop a SMZ filtration system capable of removing Escherichia coli O157:H7, Salmonella serotypes, and Listeria monocytogenes from irrigation water. A liter of inoculated water with Escherichia coli O157:H7, Salmonella typhimurium, or Listeria monocytogenes at counts of 6 log CFU/ml was filtrated through a 20g column of SMZ. The SMZ at concentration higher than 20% w/w of HDTMABr removed > 6 log CFU/ml of Escherichia coli O157:H7 and Listeria monocytogenes, and > 2 log Salmonella sp. The SMZ was tested in a strawberry field using a filtration system with regular sand and with the SMZ operating at 25 GPM. Two controls were used to prove the effectivity of the SMZ—a positive control of the pond water and a filter system with only regular sand. An Escherichia coli non-pathogenic surrogate was used to spike pond water, which naturally contains fecal material, to concentrations higher than 6 log CFU/ml. The SMZ filtration system had a removal capacity of more than 99.99% of the Escherichia coli in comparison to the two controls that did not remove these bacteria from the system. SMZ modified with HDTMABr could be a viable solution for farmers to comply with new FSMA regulations and provide a way to reduce foodborne outbreaks.



Committee Chair

Janes, Marlene