Comparison of chlorine with an iodine-based compound on eggshell surface microbial populations in a commercial egg washer

Microbial contamination of egg shells is of great importance in the commercial production of table eggs. The objective of this project was to determine the effectiveness of an iodine-based disinfectant (IBD) on the microbial population of eggshell surfaces under simulated industry egg processing conditions with a commercial egg washer used as the delivery system for sanitizers. Recirculated egg washer water containing 3.69-5.81 log colony-forming units (CFU)/mL aerobic organisms and 2.02-2.47 g/L total dissolved solids (TDS) was obtained fi om a commercial egg processing facility and used to simulate conditions found in the commercial egg industry. Sanitizing treatments consisted of distilled deionized water (DDW), IBD, and chlorine (CL; 200 ppm). Enumeration of aerobic plate populations indicated that IBD and CL treatment significantly (p < 0.05) decreased microbial populations on the shell compared to DDW treatment when egg wash water TDS were lower (2.02 - 2.03 g/L) and wash water aerobic plate counts (APC) were higher (5.05 - 5.85 log CFU/mL). When egg wash water TDS was higher (2.47 g/L) and wash water APC were lower (3.69 log CFU/mL) sanitizers were not effective in reducing egg shell microbial populations. No difference in egg shell APC counts was detected between the IBD and CL. In a second trial, cycloheximide or tetracycline amendments were added to media to test the effectiveness of the treatments on either mold and fungi or bacteria alone. When wash water TDS were higher (2.44-2.46 g/L) the sanitizers were again less effective against bacteria compared to samples from lower TDS while fungal populations did not show any significant differences among the treatments. It was concluded from this study that the IBD is an effective sanitizer when used in conjunction with a commercial egg washer but potential efficacy is dependent on the level of TDS in the egg wash water.