Purpose: A study was conducted to set forth a mathematical model for determining the thermal destruction of three heat-resistant strains of Salmonella in liquid egg yolk to effect a 7-log reduction of the bacterium.
Methods: Commercial liquid egg yolk was inoculated with the three most heat resistant strains of those tested in our laboratory, which included S. Enteritidis Pt8, strains C405 and C398 as well as S. Oranienburg DD2229. The glass capillary tube method was used to test thermal resistance of salmonellae at temperatures of 58, 60, 62, 64 and 66°C. Total solids, percent fat and apparent viscosity of the liquid egg yolk were assessed.
Results: The logistic 3P model was selected out of sixteen models tested based on R2 values. Results indicated that D-values for these five temperatures (viz. 58, 60, 62, 64, and 66°C) were 4.96, 1.65, 0.65, 0.23, and 0.05 min, respectively, which is greater than that reported in the literature. Based on these results, a 5-log destruction of salmonellae would require 8.25 min at 60°C and a 7-log inactivation would necessitate 11.55 min. A calculator was developed, that allows the user to set up the pasteurization regimens with a temperature and time to achieve any desired level of Salmonella inactivation between the temperatures of 58 and 66°C and its corresponding uncertainty expressed by a 95% confidence interval.
Significance: These data may assist processors and regulators in designing pasteurization regimens suitable for the production of safe pasteurized liquid egg yolk, used in many ready-to-eat foods.