Reduction in microbial survival on food contact surfaces by a spray coated polymerized quaternary ammonium compound

Using polymerization and immobilization techniques, the loss of antimicrobial efficacy of a quaternary ammonium compound (QAC) was minimized by decreasing its solubility and crosslinking it to metal substrates. The survivability of Listeria innocua and Escherichia coli K12 inoculated to silane QAC coated metal surfaces was compared with uncoated metal surfaces at different treatment conditions for up to 6 months storage. Resilience of the coating material to repeated cleaning, up to 20 washing and rinsing cycles, was also investigated. No evidence of bacteria viability (>5 log reduction of colony-forming unit) was observed for L. innocua when they were inoculated onto coated surfaces stored for 3 months, whereas E. coli was reduced by 3 to 4-logs. For the viable L. innocua cells on the coated surfaces, >5 log reductions were achieved even after the coated surfaces were cleaned by 20 washing and rinsing cycles prior to the cells' inoculation. For the E. coli cells, ~ 2 log reductions were achieved after 5 cleaning cycles and <1 log reduction after 10 or more cleaning procedures. Overall, the results showed that the coating had antimicrobial activity against Gram-positive bacteria while it showed moderate activity to Gram-negative bacteria.