Comparison of eggshell surface microbial populations for in-line and off-line commercial egg processing facilities

The objective of this project was to evaluate the aerobic plate counts (APC) of eggshells at in-line and off-line egg processing facilities at selected sites, throughout the processing procedure. Samples were collected from four sites in the processing plant and five time periods during the daily processing shift. Site 1 was from the conveyor system before the eggs passed through the washing system. Site 2 was after detergent wash but before sanitizer application. Site 3 was immediately after sanitizer treatment. Site 4 was immediately before packaging. Samples were collected from the sites at five equally spaced intervals beginning 15 min after the processing shift began and ending 15 min before the processing shift ended. At each sampling time, eggs were aseptically collected from each site and placed into sterile plastic bags containing 50 mL of PBS that was serially diluted immediately. The dilutions were plated on APC agar within 8 h of collection and were incubated at 37 C for 48 h. APC counts of in-line and off-line eggs were compared within time periods across sites. As the processing shift progressed, off-line APC counts were significantly higher than in-line counts at Site 1. At Site 2, off-line APC counts were significantly higher than in-line counts for Periods 2 through 5. At Site 3, off-line APC counts were significantly higher than in-line counts for Periods 2 through 5. Site 4 off-line counts were significantly higher than in-line counts at all time periods.