Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Navam S. Hettiarachchy

Committee Member

Dan Davis

Second Committee Member

Luke Howard

Third Committee Member

Mahendran Mahadevan

Fourth Committee Member

Jackson Lay Jr.

Fifth Committee Member

Soo Hyoun Ahn

Keywords

Antimicrobial, Food Safety, Nanoparticles, Phenolics

Abstract

Food-borne illnesses are of major concern in the U.S. and worldwide. Salmonella,Listeria,E. coli O157:H7 continue to be some of the major foodborne pathogens. Recurring recalls due to these pathogens demand critical antimicrobial strategies to decontaminate the food through its procession from farm to fork. In our study, we combined the effectiveness of naturally occurring phenolic compounds individually, with/ without ethylenediamine tetraacetic acid (EDTA) and/or Nisin and nanoparticle delivery to improve the antimicrobial potential of the compounds against Listeria monocytogenes (L.m.), Salmonella Typhimurium (S.T.), and Escherichia coli O157:H7 (E.c.), in brain heart infusion broth (BHI) and chicken breast meat systems. Phenolic compounds commonly occurring in fruits, vegetables and tea, were studied for their effects on L.m., E.c.) and S.T. in brain heart infusion broth (BHI) and meat system. Incubated at 37°C for 72 h in BHI, gentistic, benzoic and vanillic acids inhibited L.m., E.c. and S.T. at 5000 μg/ml by 2.8 to 3.0 log CFU/ml, 2.8 to 3.0 log CFU/ml and 2.7 to 2.9 log CFU/ml respectively. Encapsulation of benzoic acid (1100 μg/ml) in polylactic-co-glycolic acid nanoparticles inhibited 6.5 log CFU/ml of L.m. and S.T., and 6.0 log CFU/ml of E.c. at 48 h. In raw and cooked chicken meat systems, nanoparticle delivery of benzoic acid was effective against S.T. and L.m. (1.0 and 1.6 log CFU/g reduction of S.T. and 1.1 and 3.2 log CFU/g reduction of L.m. compared to 1.2 log CFU/g without nanoparticles on the days 9 and 14 of storage respectively). Encapsulation of benzoic acid (1100 μg/ml) and EDTA (200 μg/ml) in polylactic-co-glycolic acid nanoparticles inhibited the growth by 6.6 log CFU/ml of L.m., 6.2 log CFU/ml of E.c., and 6.8 log CFU/ml of S.T., at 48 h in broth system. Treatment of phenolics with EDTA (200 µg/ml) enhanced inhibition of S.T. and E.c. (3.0-3.8 log CFU/ml reductions of each), compared to their direct use (2.7-3.0 log CFU/ml reductions) in chicken meat system. These findings demonstrate the efficacy of phenolics on pathogen reduction delivered by nanoparticles and their potential for commercial food safety applications.

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