Preliminary Investigation of the Effect of Chemical Sanitizers and UV-C Light on Listeria monocytogenes Biofilm Survivability

The ability of Listeria monocytogenes to adapt under different environments and form biofilms is a challenge for food safety. Mature biofilms are difficult to disrupt. Chemical sanitizers combined with nonthermal technol-ogies might be an effective way to control L. monocytogenes biofilms. This study was conducted to investigate L. monocytogenes biofilm survival after treatments with chemical sanitizers and UV-C light alone or in combi-nation. A Centers for Diseases Control and Prevention biofilm reactor was used to grow 4-day-old multistrain L. monocytogenes biofilms on stainless steel. Biofilm survival was evaluated after 10 min of exposure to lactic acid (4%), peroxy acid (100 ppm), and quaternary ammonium (400 ppm) alone or in combination with 15 or 30 min of exposure to UV-C light (254 nm). The sequen-tial treatment effect was also evaluated. Reductions of 2.6 to 3.6 log CFU/cm2 were observed with chemical sanitizers, whereas a maximum of 1.8 log CFU/cm2 reduction was recorded after UV-C treatment. Combined treatments had an enhanced effect, and the sequence of antimicrobial treatments was significant for lactic acid and peroxy acid (P < 0.05). The results obtained in this research offer an initial understanding of the response of L. monocytogenes biofilm to chemical sanitizers and con-tribute to development of effective strategies to control this pathogen in the food processing environment.