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Improving Safety of Shell Eggs and Egg Products by Addressing Critical Research Needs for Salmonella Enteritidis and Spp.


<OL> <LI> Development and validation of predictive models for growth of Salmonella Enteritidis in intact shell eggs and mathematical models for heat transfer in freshly laid eggs <LI> Development and validation of predictive microbiological models for destruction of Salmonella spp. in select egg products<LI> Application and validation of alternative, non-thermal technologies for pasteurizatio of egg white <LI> Education and outreach efforts for increasing knowledge on improving safety of egg and egg products and use of predictive models

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Non-Technical Summary: Salmonellosis is a major cause of foodborne illness in the United States and is estimated to cause 1.4 million Salmonella infections each year. While eggs are traditionally considered to be safe, research indicates that the eggs can be infected with Salmonella Enteritidis when the eggs are laid. Salmonella present in the egg yolk can grow to very high populations within a short period of time between the time the eggs are laid and the time they are cooled. Salmonella infections from egg and egg products can be minimized by cooling the eggs promptly after they are laid, during washing and distribution and by proper pasteurization of the egg products. The purpose of the project is to develop and integrate mathematical models for cooling of shell eggs during collection and dynamic microbial predictive models to describe growth of Salmonella Enteritidis in the egg yolk. This will allow processors to evaluate their cooling processes and design adequate cooling processes to prevent growth of Salmonella Enteritidis. Predictive models for destruction of Salmonella spp. in various egg products will be developed. Alternative non-thermal processing technologies such as pulsed electric fields and dense-phase carbon dioxide will be evaluated for use in egg processing to minimize quality changes in products due to heat during traditional pasteurization. The ultimate goal of the research and outreach program is to reduce the burden of foodborne illness due to Salmonella from egg and egg products. <P> Approach: Heat transfer models to describe cooling of shell eggs will be developed using computational fluid dynamics software packages to accurately estimate the temperature distribution of eggs using finite element modeling. Predictive models to describe the growth of Salmonella Enteritidis (SE) in shell eggs will be developed. These models will be able to evaluate growth of SE in shell eggs from the time the eggs are laid to the time they arrive at the processing facility. Primary and secondary microbiological models will be integrated to develop a dynamic microbial model to describe SE growth under constantly varying temperature conditions. The heat transfer and dynamic microbiological models will be integrated to evaluate growth of SE under industry conditions. Egg yolks will be inoculated with SE and growth of SE will be evaluated under constantly varying temperature conditions to simulate various industry practices. SE populations will be enumerated at various times and the models will be validated by comparing model predictions with observed data. Thermal destruction parameters for Salmonella spp. in egg white, egg yolk and liquid whole egg will be determined using five strains of Salmonella. Five strain Salmonella cocktail will be inoculated into each product individually and D- and Z-values will be determined and mathematical models to describe Salmonella destruction in specified egg products will be developed. The determined D- and Z- values will be used in validating industry procedures for pasteurization of egg products using equipment similar to what the industry uses. The developed mathematical models will be incorporated into the USDA-ARS Pathogen Modeling Program and a user interface will be created to assist users in evaluating/designing the pasteurization requirements for particular products. Most of egg and egg products are pasteurized using conventional thermal processing technologies. Pasteurization of sensitive products such as egg white may result in undesirable losses in functionality. Two non-thermal technologies, pulsed electric field (PEF) and dense-phase carbondioxide (d-CO2) that have been shown to be effective in destruction of Salmonella in other food products. Combinations of temperature, D-CO2 pressure and exposure times will be evaluated based on preliminary results. Destruction rates will be calculated, and mathematical models will be developed and evaluated. Preservation of egg white functional properties is critical to the adoption of any new technology for egg white and other egg products. Functional properties such as angel cake volume, foam volume and foam stability will be evaluated following standard methodologies. Treatment combinations optimized for Salmonella spp. destruction will be selected and the treated product evaluated for the functional properties using standard methodology. A revised edition of the International Egg Pasteurization Manual, along with fact sheets and other extension instruments will be developed. In addition, video and multimedia modules on Assuring Safety of Eggs and Egg Products will be developed and used to assist egg processors and enhance the outreach efforts.

Thippareddi, Harshavardhan
University of Nebraska - Lincoln
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