BUILDING BETTER MATERIALS: MULTIFUNCTIONAL POLYURETHANE COATINGS TO ELIMINATE BACTERIA IN FOOD PROCESSING ENVIRONMENTS
Bacterial contamination during food processing and production continues to be a major contributor to foodborne illness cases and microbial food spoilage. As additional regulatory guidance and efforts emerge for preventing microbial contamination of food, technologies for eliminating favorable growth conditions within processing and production facilities must also be considered. Areas with conditions most favorable for bacteria, e.g., dampness and consistent richness in organic matter, are optimal environments for bacteria to adhere to and create biofilms. Pathogenic and spoilage bacteria can persist as biofilms in non-food contact Zone 2/3 growth niches (e.g., drains) in food processing facilities. As both foodborne illnesses and microbial food spoilage persist, a need remains for new technologies to eliminate favorable growth environments. The goal of this work, therefore, is to develop a polymeric material that kills bacteria on contact reducing favorable surface conditions for bacteria and debris to adhere. Towards this goal, here we present the synthesis and characterization of polyurethane-co-perfluoropolyether (PU-c-PFPE), dihydroxy quaternary ammonium bromide (QAB), and dihydroxy quaternary ammonium bromide modified PU-c-PFPE (C16QAB + PFPE PU). PU modified with PFPE exhibited significant differences in advancing water contact angle (128.8° ± 5.2) and critical surface tension (12.54 mN m -1) compared to unmodified polyurethane (93.6° ± 3.6 and 17.19 mN m -1) indicating a change in surface hydrophobicity and lowered critical surface tension. Quaternary ammonium compounds (QACs) are antimicrobial compounds commonly used in sanitizers, however, in this work dihydroxy QAB was synthesized with two hydroxy end groups for facile polymerization. QABs with varying alkyl chain lengths (C8, C10, C12, C16, and C18) were synthesized with C16 and C18 possessing the lowest minimum inhibitory concentrations against pathogenic and spoilage bacteria (3 ppm for Gram + and 26 ppm for Gram -). Therefore, QAB with C16 was chosen for polymerization into PU-c-PFPE to form a low surface tension antimicrobial coating. C16QAB + PFPE PU exhibited a critical surface tension of 13.14 mN m-1 and inactivated Listeria monocytogenes below the limit of detection, delivering a >6 log reduction (> 99.9999%) and exhibited a >3 log reduction (>99.9%) for Salmonella enterica. The technologies presented herein are promising developments in methods to eliminate persistent bacteria and contamination in non-food contact Zones 2/3.