Biofilm Formation and Pressure-Based Pasteurization of Bacterial Spores and Foodborne Pathogens of Public Health Concern as Affected by Bacteriocin and Bactericidal Compounds

Pathogens of public health concern associated with food and agricultural commodities are global and national challenges. Based on epidemiological studies of the U.S. Centers for Disease Control and Prevention, in a typical every, 48 million people become sick from foodborne diseases, 128,000 are hospitalized, and 3,000 die. The first study of this dissertation utilized a six‐strain mixture of E. coli O157:H7 that were exposed to 0 to 9 minutes of hydrostatic pressure (400 MPa) and thymol for the experiments of the inoculated pathogen in a 10% beef homogenate. Pathogen counts were reduced to 0.67 ± 0.2 logs CFU/mL after 6 minutes of pressure treatment. Thymol and mild heat (40 °C) and pressure treatments after 3, 6, and 9 minutes reduced (p \u3c 0.05) the pathogen by 2.1, 2.5, and 3.1 logs CFU/mL, respectively. The second study of this dissertation is dedicated to controlling Listeria monocytogenes using mild heat with elevated hydrostatic pressure at 400 MPa and nisin under buffered conditions. A pathogen mixture was exposed to 0 to 9 minutes of treatments at 4 and 40 °C. This synergism with nisin faded away (p ≥ 0.05) as the treatment time for thermal, high-pressure, and thermal-assisted pressure processing increased and was efficacious (p \u3c 0.05) for treatments \u3c 3 minutes. The third study of this dissertation was designed to investigate biofilm formation by ten strains of Salmonella serovars for up to 21 days at 25 °C. Mature biofilms were then treated with carvacrol, quaternary ammonium, and water. Planktonic cells exhibited greater sensitivity to the tested antimicrobials compared to sessile cells of one-, two-, and three-week mature biofilms. The last study of this dissertation was designed to study the effects of elevated hydrostatic pressure for the inactivation of three indicator spore-forming bacteria. Elevated hydrostatic pressure at 650 MPa and 50 °C were applied for 0, 3, 7, and 11 minutes with and without nisin, lysozyme, lactic acid, and Citricidal™. We observed that a well-design pressure treatment synergized with mild heat and bacteriocin and bactericidal compounds could reduce up to \u3e 4 logs CFU/mL (i.e. \u3e 99.99%) of bacterial endospores