Assessing the impact of egg sweating on Salmonella Enteritidis penetration into shell eggs

Authors: GRADL, JANET - Auburn University; CURTIS, PATRICIA - Auburn University; Jones, Deana; ANDERSON, KENNETH - North Carolina State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 2/23/2017
Citation: Gradl, J.A., Curtis, P.A., Jones, D.R., Anderson, K.E. 2017. Assessing the impact of egg sweating on Salmonella Enteritidis penetration into shell eggs. Poultry Science. 96:2393-2399.

Interpretive Summary: Egg sweating associated with holding, processing, distribution, and consumer handling has been a concern since the moisture on the shell surface can allow for bacteria on the shell surface (should they be present) to migrate through the shell. A study was conducted to determine the role egg sweating played on Salmonella Enteritidis contamination in inoculated and control eggs. Very low levels of Salmonella Enteritidis were enumerated the first week of storage after inoculation and sweating. The prevalence of Salmonella Enteritidis was determined via enrichment. The non-sweated, inoculated eggs had a significantly higher prevalence of Salmonella Enteritidis detected compared to sweated, inoculated eggs at weeks 1, 2, and 3 of storage. The results of the study show that under the sweating conditions utilized, Salmonella Enteritidis contamination of eggs was not increased due to egg sweating.

Technical Abstract: Salmonella Enteritidis (SE) prevalence in eggs is a major concern to the egg industry. Some research has shown that egg sweating can increase Salmonella penetration into egg contents when refrigerated eggs are moved to a warmer temperature. This occurs when eggs are tempered before wash, to minimize thermal cracks from occurring. The objective of the study was to assess the effect of egg sweating on S. Enteritidis penetration into shell eggs over a six week storage period at 4 °C. A 2x2 factorial of S. Enteritidis inoculation and egg sweating was utilized. Treatments included (SES) nalidixic acid (NA)-resistant S. Enteritidis inoculated and sweated, (SENS) NA-resistant S. Enteritidis inoculated and not sweated, (NSES) buffered peptone water (BPW) inoculated and sweated, and (NSENS) BPW inoculated and not sweated. Inoculated eggs were exposed to 108 S. Enteritidis. Eggs formed condensation for approximately 17 min in a 32 ° C incubator. Shell rinse, shell emulsion, and egg contents were sampled then enumerated and assessed for prevalence of S. Enteritidis over a 6 wk storage period at 4 °C. After wk 1, the shell rinse from the S. Enteritidis inoculated/non-sweated treatment had higher Salmonella counts (0.32 log10 CFU/mL) than the other three treatments, where no S. Enteritidis was enumerated. A significant week by treatment interaction was found for the shell rinse S. Enteritidis detection (P < 0.05). In subsequent wks, no S. Enteritidis counts from any treatment were obtained from the egg shell rinse, shell emulsion, or egg contents. The SENS treatment shell rinses had significantly higher S. Enteritidis prevalence than the sweated and inoculated treatment (SES) in wks 1 (100% vs. 34.3%), 2 (57.6% vs. 22.2%), and 3 (38.2% vs. 11.1%) (P < 0.05). In samples from wks 4, 5, and 6, there was no difference in S. Enteritidis prevalence between the SES and SENS treatment. Egg sweating did not increase S. Enteritidis penetration into the shell emulsion across treatment or week (P < 0.05). The decreasing trend of S. Enteritidis prevalence obtained over the six week period indicate that refrigeration is a very effective method to inhibit Salmonella growth. These results indicate that egg sweating occurring under common US egg handling practices is not harmful to egg safety.