Date of Completion
Dennis D'Amico, Mary Anne Amalaradjou, Kumar Venkitanarayanan
Field of Study
Master of Science
Listeria monocytogenes is a bacterial pathogen that causes listeriosis, the third-leading cause of death related to foodborne illness. The anti-listerial efficacy of acidified calcium sulfate with lactic acid (ACSL), beta-resorcylic acid (BR), caprylic acid (CA), e-polylysine (EPL), hydrogen peroxide (HP), lauric arginate ethyl ester (LAE), and sodium caprylate (SC) was determined in Brain Heart Infusion broth, ultra-high-temperature pasteurized milk, and fresh cheese (Queso Fresco). Binary combinations of antimicrobials were tested to identify synergistic interactions, which can reduce usage rates. Overall, HP was the most efficacious treatment with concentrations of 40-50 ppm inhibiting L. monocytogenes in broth, 200 ppm resulting in undetectable counts in milk, and a 5% dip treatment resulting in /g of L. monocytogenes recovered from cheese. Thirteen synergistic combinations were identified in broth adjusted to either pH 7.4 or 5.5. Sodium caprylate was the most common antimicrobial identified among effective combinations. The combination of EPL + LAE was the most synergistic combination for the inactivation of L. monocytogenes in broth at pH 7.4, with an FBCI of 0.292. Effective concentrations of EPL and LAE increased approximately ten-fold in milk with inhibitory concentrations of 200 ppm and 800 ppm, respectively, whereas CA and SC produced inhibition at similar concentrations in both media. The antimicrobial pairing of ACSL+SC produced synergy against L. monocytogenes in QF. These results together identify antimicrobial treatments effective at reducing and/or inhibiting the growth of L. monocytogenes in varying conditions and serve as a basis for applications in food.
Kozak, Sarah, "Determining the Efficacy of Antimicrobials for the Inhibition and Inactivation of Listeria monocytogenes in Broth, Whole Milk, and Fresh Cheese." (2016). Master's Theses. 1039.