Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 2005
Publication Date: October 1, 2005
Citation: Jones, D.R., Musgrove, M.T. 2005. Correlation of eggshell strength and salmonella enteritidis contamination of commercial shell eggs. Journal of Food Protection. 68(4):2035-2038 Interpretive Summary: The poultry industry is constantly working to improve genetic selection so as to enhance production efficiency, meet consumer demand and to produce a better quality product. There are many factors that directly or indirectly affect products of this selection process. For laying hens, eggshell quality is one of these traits. The current research was conducted to determine if there is a correlation between eggshell strength and Salmonella Enteritidis (SE) growth on the shell surface and in the egg contents. A nalidixic acid resistant strain of SE was used to inoculate shell eggs. Shell strength was monitored via objective methods. The results found that there are only weak correlations between eggshell strength and the ability of SE to grow on the shell surface or in the egg contents. Therefore, while shell strength is an important factor for product quality, it is not a major contributor or deterrent for SE growth.
Technical Abstract: Shell quality has been identified as a heritable trait which can be manipulated by genetic selection. Previous research has concluded that many methods of determining shell quality are highly variable in their results. With the development of newer, finite measuring technologies, shell strength can now be assessed in a consistent, objective fashion. A research project was conducted to determine what role shell strength might play in external Salmonella Enteritidis contamination of egg contents. Visibly clean eggs were collected from an in-line shell egg processing facility at the accumulator. Eggs were dipped in a concentrated inoculum of nalidixic acid resistant SE. After storage, eggs were assessed for shell strength along with external and internal SE contamination. In the first study, there was a significant difference (P < 0.05) in shell strength amongst the three replicates. There was also a difference (P < 0.01) in external SE contamination levels between the controls and inoculated eggs. No differences between treatments were found for shell strength or contents SE contamination. In the second study, there were no replicate differences for any of the monitored factors. When rinsate and content samples were enriched, 100 % of the rinsates were positive for SE. No content samples had shown SE during direct plating, but 3-5 % of the samples from each replicate were positive after enrichment. Correlation analysis of the results from each study found only weak correlations between shell strength and eggshell surface and contents SE contamination. The results of this research suggest that shell strength does not play a major role in SE contamination.