Biofilm formation by Salmonella Enteritidis in a simulated liquid egg processing environment and its sensitivity to chlorine and hot water treatment

- Denser biofilms were observed in PW and EW compared to those in WE and EY.
- Chlorine treatment failed to eradicate biofilms formed in egg media.
- Biofilm formed in EW was more chlorine tolerant than those in EY, WE, and PW.
- Organic materials of growth media greatly affected biofilm morphology.
- Hot water treatment was more effective in eliminating biofilms formed in egg media.

This study investigated the biofilm formation by three S. Enteritidis strains in a simulated liquid egg processing environment using 0.1% peptone water (PW) (control), 10% whole eggs (WE), 10% egg yolks (EY) and 10% egg whites (EW) as growth media, and evaluated the effectiveness of chlorine (200 ppm, 5 min) and hot water (71 °C, 30 s) treatments against S. Enteritidis biofilms. The results showed that S. Enteritidis formed significantly (P < 0.05) denser biofilms in PW and EW compared to those in WE and EY. However, biofilms formed in PW were less resistant to chlorine treatment than those formed in WE, EY, and EW, with average log reductions of 6.34, 2.28, 0.67 and 0.95 CFU/cm2, respectively. Microscopic observation showed that biofilm morphology was greatly affected by the growth medium, and the egg matrices might act as protective barriers, contributing to the greater chlorine resistance. All biofilms were very sensitive to hot water treatment, which reduced the cell populations by 4.30-7.08 log CFU/cm2. This study could advance our understanding towards the biofilm forming abilities of S. Enteritidis in liquid egg processing environments and the effectiveness of sanitation methods against S. Enteritidis biofilms, which may aid in the development of better sanitation strategies.