Optimization of critical factors for thermal inactivation and control of Salmonella enteritidis in shell eggs

The overall objective of this study was to develop a pasteurization system and a rapid cooling system for shell eggs. The first specific objective was to develop a rapid and sensitive method for detection of Salmonella Enteritidis in eggs using iron supplementation. It was found in this study that iron supplementation significantly enhanced the growth of Salmonella Enteritidis. The optimum iron level for Salmonella Enteritidis growth in egg contents was between 0.2 and 2 mg of FeSO ₄ per g of egg contents. With iron supplementation, preenrichment was not necessary for isolation of Salmonella Enteritidis from eggs. The direct plating method detected a significantly higher percentage of Salmonella Enteritidis in raw egg contents supplemented with 0.5 mg of FeSO₄ per g of egg contents (90%) than in raw egg contents without iron supplementation (63.3%).; The second specific objective was to study the effect of rapid cooling on microcrack development on eggshell, eggshell strength, the penetration of Salmonella Enteritidis into egg contents, and the growth of Salmonella Enteritidis in egg contents. It was found that cooling produced microcrack on eggshells. However, the microcrack developed on the eggshells did not increase the penetration of Salmonella Enteritidis into egg contents and did not affect eggshell strength. Rapid cooling and subsequent storage of eggs at 6.6–7.2°C inhibited the growth of Salmonella Enteritidis in egg yolk and albumen. However, traditional cooling, and/or temperature abuse promoted the growth of Salmonella Enteritidis in yolk and albumen.; The third specific objective was to determine the effect of pasteurization on the destruction of Salmonella Enteritidis in eggs and on egg quality. Microwave pasteurization alone was not effective in the destruction of Salmonella Enteritidis in egg contents. Therefore, a two-stage pasteurization process was developed. Pasteurization of eggs in a microwave oven for 5 min at 58–63°C followed by heating in a water bath at 57°C for 35 min reduced Salmonella Enteritidis counts in egg contents by 5.7 logs. This process did not significantly affect Haugh units, Yolk index, and pH values, but significantly increased the Turbidity values and decreased the Whip Test values.