Effects of Zataria multiflora boiss essential oil, ultraviolet radiation and their combination on Listeria monocytogenes biofilm in a simulated industrial model

The objective of this study was to investigate the inhibitory effect of Zataria multiflora boiss essential oils (ZEOs), ultraviolet (UV) radiation and their combination against Listeria monocytogenes biofilm in a simulated industrial model (SIM). The effect of minimal inhibitory concentration (MIC) and sub-MIC concentration of ZEOs, different contact time of UV and their combination was evaluated in a SIM on 6-and 12-day-old L.monocytogenes biofilm. In a SIM, 0.3% ZEOs were adequate to completely eliminate 6- and 12-day-old biofilm grown on stainless steel coupons. The population of viable L.monocytogenes biofilm cells under a 15- to 45-min contact time of UV treatment declined significantly at 6- and 12-day-old biofilm. The combined effect of ZEO and UV showed antagonist effects. These findings indicated that in the single use, ZEO and UV revealed a suitable antilisteria biofilm activity, while combining them is not a promising method to remove listeria biofilms from stainless steel surfaces.