Identification of Enterobacteriaceae in Foods with the AutoMicrobic System

A comparison of seven microbiological sampling procedures for hard-cooked eggs

Seven microbiological sampling methods for hard-cooked eggs were evaluated and compared. Fresh eggs within 24 h of oviposition were cooked at 98 C for 22 min in water and then cooled in 31 C water. Eggs were dipped for 10 min in a physiological saline solution (.85% saline) 10 C cooler than the eggs and containing known numbers of bacteria. Eggs were then stored for 4 days at 6 C and sampled using one of seven rinse or blend procedures on whole eggs, shell, shelled egg contents, or shelled egg contents plus shell. Highest recoveries were made from the peeled egg plus shell rinse, shell rinse, whole egg blend, and shell blend. Lowest recoveries were found with the whole egg rinse, the peeled egg rinse, and the peeled egg blend. These results indicate that significant numbers of organisms are associated with the inner and outer shell surfaces as well as the egg contents surface (albumen). Satisfactory recoveries can be made with the peeled egg plus shell rinse or the whole egg blend. Whole egg rinsing of hard-cooked eggs does not appear to be satisfactory.