Document Type

Open Access Thesis

Embargo Period

5-15-2017

Degree Program

Food Science

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2017

Month Degree Awarded

September

Advisor Name

Lynne A. McLandsborough

Co-advisor Name

Eric A. Decker

Third Advisor Name

Julie M. Goddard

Abstract

The iron chelating molecule, ethylenediaminetetraacetic acid (EDTA) is used in food applications for the preservation of oxidation prone ingredients. Research has suggested that EDTA is also capable of enhancing the antimicrobial effectiveness of various compounds including naturally-derived antimicrobials. With consumer demand for cleaner food labels, there remains an opportunity to introduce new chelating technology to replace synthetically-derived EDTA. Through photographting and chemical conversion, hydroxamic acid ligands were covalently bound to polypropylene films resulting in polypropylene-graft-poly(hydroxamic acid) (PP-g-PHA). The resulting films demonstrated an ability to chelate 64 nmol/cm2 from an iron saturated environment or 163 nmol/cm2 of magnesium and 139 nmol/cm2 of calcium from bacterial growth media. A surface pKa of 8.97 suggested that film ligands should remain protonated under acidic and neutral pH conditions. When combined with lysozyme, PP-g-PHA films were able to reduce inhibitory concentration of lysozyme for Listeria monocytogenes by half. When tested against Bacillus cereus, Pseudomonas fluorescens, and E. coli O157:H7; PP-g-PHA films were unable to inhibit growth and showed little enhancement of lysozyme. EDTA controls revealed that similar levels of soluble chelator were more effective than immobilized chelators. EDTA results also suggested that a chelating film with a higher affinity for iron (through coordination or ligand stability) may be able to control B. cereus growth. Both EDTA and PP-g-PHA caused P. fluorescens to produce siderophores (pyoerdines), suggesting that each treatment resulted in a low-iron growth environment. These findings suggest that surface bound chelating technology can affect the growth of L. monocytogenes and enhance the effectiveness of lysozyme. With improved surface chemistry (a higher binding constant with iron), this technology has the potential to influence the growth of other pathogens and spoilage microorganisms.

First Advisor

Lynne A. McLandsborough

Second Advisor

Eric A. Decker

Third Advisor

Julie M. Goddard

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