Attachment and removal of biofilm of Salmonella enterica subsp. enterica serovar Typhimurium 53647 embedded in liquid whole egg on stainless steel, silicone, and nylon

Biofilms are an ongoing safety risk in the egg industry; different points of the processing lines can harbor the growth of pathogens. This work aimed to study the attachment, biofilm formation, and removal of Salmonella enterica subsp. enterica serovar Typhimurium 53647 inoculated in liquid whole egg (LWE, 10 3 cfu/ml) on stainless steel, silicone, and nylon. Cells were allowed to grow and attach at 37⁰C for 1 to 48 h (static conditions). Biofilm removal and sanitization were conducted with sodium hypochlorite (200 ppm) and peracetic acid (PAA, 200 ppm). The use of ficin (6.25 U/ml) was studied before applying PAA at lower concentrations (90 and 120 ppm). Contact time for all PAA treatments was 1-, 5- and 10-min. Scanning Electron Microscopy (SEM) was used to observe the biofilm formation. Results showed quick microbial growth and biofilm formation after 24 h (> 7 log). Nylon presented the highest cell attachment after 48 h. SEM showed a thick biofilm with cells embedded in the egg matrix. Chorine removed and sanitized better stainless steel after 1 min (p < 0.05), but all surfaces were Salmonella- free after 5 min; similar results were observed for PAA after 10 min. The enzymatic pre-treatment with ficin opened the egg biofilm matrix and reduced the contact time with the sanitizer. A two-step sanitization process (enzymatic treatment and organic acids) represents a viable option for the removal of egg biofilms and inactivation of Salmonella Typhimurium and can be used in the egg industry. • Salmonella created a strong biofilm in liquid egg after 24 hours • Stainless steel, silicone and nylon presented good surface for biofilm formation • The use of chlorine and peracetic acid (200 ppm) inactivated the biofilm cells • Ficin used as a pre-treatment was able to open the egg biofilm • Ficin and PAA (120 ppm) removed the biofilm, and sanitized the surface