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Document Type

Campus-Only Access for Five (5) Years

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Food Science

Year Degree Awarded

2015

Month Degree Awarded

February

First Advisor

Julie M. Goddard

Second Advisor

Lynne A. McLandsborough

Third Advisor

Micha Peleg

Fourth Advisor

Vincent Rotello

Subject Categories

Food Microbiology | Food Processing | Food Science | Nanoscience and Nanotechnology | Polymer Science

Abstract

Cross contamination during food processing represents a risk for public health and financial burden. Surface modification of food contact materials to render them antimicrobial can be effective against such risk. The objective of the present work was to develop antimicrobial coatings with the potential to be applied in a variety of food contact materials. The polymer coatings developed became antimicrobial by incorporation of a type of chlorinated compounds called N-halamines, capable of regenerating their antimicrobial activity.

Two layer-by-layer (LbL) assembly surface modification procedures were followed. In the first procedure, bilayers of branched polyethyleneimine (PEI) and poly(acrylic acid) (PAA) were applied onto stainless steel and polyethylene (PE). As the number of bilayers increased, so did the number of N-halamines the coatings were able to harbor. Increasing the number of bilayers also translated into greater antimicrobial efficacy against Listeria monocytogenes. The maximum level of inactivation was > 99.999%, comparable to the equivalent concentration of free chlorine. Inactivation kinetics was also studied. Coatings exhibited a sigmoidal behavior with a slower biocidal effect as compared to free chlorine. The PEI-PAA coating was also challenged against multiple rechlorinations and washing under different levels of pH and exhibited stability and ability to be regenerated.

The preparation of the PEI-PAA coating was time consuming and required expensive crosslinkers. As an alternative method for N-halamine surface modification, two bilayers of PEI and styrene maleic anhydride copolymer (SMA) were coated onto polypropylene (PP). The coating exhibited intrinsic antimicrobial properties against L. monocytogenes due to its cationic nature, able to achieve ~ 3 logarithmic cycles in reduction as prepared, and > 99.999% when chlorinated. No carbodiimide crosslinkers were needed. In addition, the coating didn't result in a significant change in surface energy (P > 0.05). The coating was also challenged against multiple rechlorinations, showing reusability.

The results suggest that the surface modification methods studied possess the potential to be applied on a variety of materials used in food processing to avoid microbial contamination. Future research will focus on developing N-halamine antimicrobial coatings with improved stability and more efficient preparation, and in the development of new antimicrobial N-halamine materials.

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