Pathogenic and spoilage bacteria can persist as biofilms in Zone 2/3 growth niches (e.g. drains) in food processing facilities which are outside of routine cleaning and sanitization. As both foodborne illnesses and microbial food spoilage continue to be issues, a need remains for new technologies to eliminate favorable growth environments. Here I present my research on the synthesis, characterization and efficacy of non-fouling (NF) and antimicrobial polyurethane (PU) coatings for use in non-food contact environments. Dihydroxy quaternary ammonium bromides, N,N-bis(2-hydroxyethyl)-N-methyl-N-R-1-ammonium bromides (R= -octan {C8QBR}, -decan {C10QBR}, -dodecan {C12QBR}, -hexadecan {C16QBR}, -octadecan {C18QBR}) were synthesized via the reaction of N-methyldiethanolamine and alkyl bromides of varying alkyl chain length. To enhance bactericidal effects of the final PU, minimum inhibitory concentrations (MIC) for each quaternary ammonium bromide were determined against Listeria monocytogenes and Salmonella enterica. C16QBR and C18QBR displayed total inhibitory effects against L. monocytogenes at 2.7ppm. C16QBR showed inhibitory effects against S. enterica at 21.3ppm. Quat sanitizers in the food industry use between 200-400ppm active quaternary. NF PU containing 1-3 wt% perfluoropolyether (PFPE) and NF and antimicrobial PU containing 3% PFPE and derivatized C16QBR were synthesized by step-growth polymerization. Coatings were characterized by ATR-FTIR, GPC, XPS, NMR, and DSC. Dynamic water contact angle demonstrated increasing hydrophobicity with the inclusion of 3% PFPE compared to the control PU (117.2° ± 1.2 versus 87.4° ± 3.8). The PFPE block reduced surface free energy compared to control PU and stainless steel (21.01mN/m, 15.09mN/m, and 0.70mN/m) . Coating performance in preventing microbial adhesion was demonstrated using Psuedomonas poae, a biofilm forming dairy spoilage organism, L. monocytogenes and Salmonella spp.. P. poae biofilms (72 hr) were established using a CDC biofilm reactor, enumerated, and imaged by SEM. Incorporation of the NF block improved the removal of established biofilms. L. monocytogenes and Salmonella spp. were used to determine the bactericidal efficacy of coatings. Antimicrobial coatings showed bactericidal effects against all test organisms. Developing antimicrobial and NF coatings using PU chemistry enhances the translatability, enhancing cleanability and reducing cross-contamination caused illness, product spoilage and waste.

Non-fouling and antimicrobial polyurethane coatings to prevent cross-contamination in food processing facilities

ACS Spring 2022

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