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Title: The Effects of Commercial Cool Water Washing of Shell Eggs on Haugh Unit, Vitelline Membrane Strength, Aerobic Microorganisms and Fungi

item CAUDILL, A. - Auburn University
item CURTIS, P. - Auburn University
item ANDERSON, K. - North Carolina State University
item KERTH, L. - Auburn University
item OYARAZABAL, O. - Auburn University
item Jones, Deana
item Musgrove, Michael

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2009
Publication Date: 1/1/2010
Citation: Caudill, A.B., Curtis, P.A., Anderson, K.E., Kerth, L.K., Oyarazabal, O., Jones, D.R., Musgrove, M.T. 2010. The effects of commercial cool water washing of shell eggs on Haugh Unit, vitelline membrane strength, aerobic microorganisms and fungi. Poultry Science. 89:160-168.

Interpretive Summary: All US retail shell eggs must be washed. Current state and federal standards require the wash water to be 32 C or 11 C warmer than the warmest egg entering the processing line. Shell egg wash water temperature is generally 46 – 49 C. Exposure to the warm water results in increased internal egg temperature which can allow for greater microbial growth should organisms be present. The current study was undertaken to exam the implications of commercially processing shell eggs in cool water on egg physical and microbial quality. Wash water temperature did not have a dramatic effect on internal egg quality or aerobic organisms and fungi. Within the constraints examined in this study, the commercial practice of cool water washing of shell eggs results in eggs exiting the processing line at a lower temperature which enhances the physical and microbial quality of the eggs.

Technical Abstract: Current egg washing practices utilize wash water temperatures averaging 49°C, and have been found to increase internal egg temperature by 6.7 to 7.8°C. These high temperatures create a more optimal environment for bacterial growth, including Salmonella Enteritidis (SE), if it is present. SE is the most common human pathogen associated with shell eggs and egg products. Its growth is inhibited at temperatures of 7.2°C and below. This study’s objective was to determine if commercially washing eggs in cool water would aid in quickly reducing internal egg temperature, preserving interior egg quality, slowing microbial growth. During three consecutive days, eggs were washed using four dual tank wash water temperature schemes (HH = 49°C, 49°C; HC = 49°C, 24°C; CC = 24°C, 24°C; CH = 24°C, 49°C) at two commercial processing facilities. A ten week storage study followed, in which vitelline membrane strength, Haugh unit, and aerobic microorganisms and fungi (yeasts and molds) were monitored weekly. As storage time progressed, average Haugh unit values declined 14.8%, the average force required to rupture the vitelline membrane decreased 20.6%, average numbers of bacteria present on shell surfaces decreased 11.3%, and bacteria present in egg contents increased 39.5% during storage. Wash water temperature did not significantly affect Haugh unit values, vitelline membrane strength, or the numbers of aerobic microorganisms and fungi within the shell matrices of processed eggs. Results of this study indicate that incorporating cool water into commercial shell egg processing, while maintaining a pH of 10 to 12, lowers post-processing egg temperatures and allows for more rapid cooling, without causing a decline in egg quality or increasing the presence of aerobic microorganisms and fungi for approximately five weeks post-