Low-energy X-ray inactivation of Salmonella Enteritidis on shell eggs in mono-/co-culture biofilms with Pseudomonas fluorescens

This study investigated the bactericidal effect of low-energy X-ray on mono-culture biofilms of Salmonella Enteritidis and Pseudomonas fluorescens biofilm as well as co-culture biofilms of S. Enteritidis and P. fluorescens at the ratio of 1:1 and 1:100 (S. Enteritidis: P. fluorescens) on shell eggs. The results showed that the low-energy X-ray irradiation could effectively inactivate the mono-culture biofilm cells of S. Enteritidis and P. fluorescens with the t(R) values of 63.19 Gy and 66.53 Gy, respectively. The low-energy X-ray irradiation could also effectively inactivate co-culture biofilm cells with t R values of 80.03 Gy and 47.97 Gy for S. Enteritidis biofilm cells in the 1:1 and 1:100 ratios of co-culture, respectively, and 61.87 Gy and 30.16 Gy for P. fluorescens biofilm cells in the two ratios of co-co-culture, respectively. Apart from inactivating biofilm cells, extracellular polysaccharide (EPS) was markedly reduced at increasing dosage of irradiation. Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and texture profile analysis (TPA) results, egg white proteins and the puncture force of eggshell remained unchanged after the irradiation at up to 225 Gy. No 2-alkylcyclobutanones (2-ACBs) were detected in the irradiated eggs. These findings demonstrated that low-energy X-ray has potential as an effective method to inactivate the mono- and co-culture biofilms of S. Enteritidis and P. fluorescens on shell eggs.