Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2006
Publication Date: April 4, 2006
Citation: Jones, D.R., Musgrove, M.T., Caudill, A.B., Curtis, P.A. 2006. Frequency of salmonella, campylobacter, listeria, and enterobacteriaceae detection in commercially cool water washed shell eggs. Journal of Food Safety.26:264-274. Interpretive Summary: The reduction of shell egg temperature is of concern due to the role of temperature in Salmonella Enteritidis growth. In 1999, USDA instituted a requirement that all shell eggs be maintained in at least a 7.2C ambient environment post-processing. Researchers have determined that in this environment it takes the centermost egg of a 900 dozen egg pallet 5-6 days to reach an internal temperature of 7.2C. While rapid cooling technologies have been developed, the cost and adjustments to processing facilities lay-outs have made them impractical under current circumstances. This project was conducted to determine the effect of cool water washing on shell egg temperature and pathogen detection. Eggs were exposed to one of three wash water temperature schemes in 2 commercial operations. The study was conducted in both an inline (hen houses directly connected to the processing facility through a series of belts) and an offline (hens housed in a remote locations and eggs transported to the plant) facility. Eggshell surface temperature was lower for eggs washing in warm then cool or only cool wash water compared with the current requirement of only warm water. Salmonella was detected in 3 of 384 samples from the inline facility. The positive samples were associated with the two cool water washing schemes. Campylobacter was found in 2 of 384 samples from the inline facility (both in eggs washed only in cool water). Listeria was found in 3 wash water samples from the offline facility. No pathogens were detected in any of the 768 egg contents samples during the study. Washing eggs initially in warm water followed by cool water in the second washer has the potential of reducing egg temperature while maintaining surface microbiology at an acceptable level.
Technical Abstract: The control of Salmonella Enteritidis and other microorganisms is a concern for shell eggs. One method of controlling bacterial growth is reducing egg temperature below 7C as quickly as possible. The effect of cool water washing on shell egg temperature and pathogen detection was examined. The temperature schemes were run in two commercial processing plants (an inline and an offline facility) on three consecutive days each. Three temperature schemes utilized for the dual washer systems were: HH – 48.9C, 48.9C; HC – 48.9C, 23.9C; and CC – 23.9C, 23.9C. Shell temperature immediately post-processing was significantly different amongst the treatments for each plant and combined averages for the two plants. HH eggs always maintained the highest surface temperature (26.25C inline, 20.25C offline, and 23.25C combined, P < 0.05). The lowest temperatures were found in the CC eggs (21.25C inline, 17.25C offline, and 19.25C combined). When the temperatures were combined, there was no difference between HC and CC eggs. The frequency of Enterobacteriaceae detection in shell and membrane emulsions was greatest for CC eggs (P < 0.05 for inline and combined). There was no difference in Enterobacteriaceae detection for the offline facility. Salmonella was detected in 3 of 384 samples from the inline facility. The positive samples were found in shell emulsions from the HC (2) and CC (1) treatments. Two of 384 samples were positive (CC shell emulsions) for Campylobacter from the inline facility. Three wash water samples were positive for Listeria in the offline facility (1 – HC, 2 – CC). No pathogens were detected in egg contents during this study. The results of this study indicate that warm followed by cool water washing has the potential of decreasing egg temperature while maintaining surface microbiology at an acceptable level.