Purpose: This study was conducted to investigate the growth and survival of Salmonella Enteritidis in liquid egg whites.
Methods: Pasteurized liquid egg white samples were inoculated with a five-strain cocktail of Salmonella Enteritidis and incubated under dynamically changing temperature conditions between 2 and 37°C to observe the growth and survival of the bacterium. Two differential equations were used in combination with the Huang square-root secondary model to describe the growth and survival of Salmonella Enteritidis. A one-step dynamic analysis method was used to determine the kinetic parameters using least squares optimization by minimizing the sum of squared residuals.
Results: No lag phase was observed in the growth curves. The growth and survival of Salmonella Enteritidis was accurately analyzed using the one-step dynamic analysis method. The estimated minimum growth temperature (Tmin) of the bacterium was 7.76°C, matching well with the general characteristics of Salmonella Enteritidis. At temperatures below Tmin, the bacterial would die of at 0.136 log CFU/g per day per °C. For model development, the root mean square error (RMSE) was only 0.43 log CFU/g. About 70% of the residual errors were within 0.5 log CFU/g of observations. For validation, about 69% of the residual errors were within 0.5 log CFU/g of observations.
Significance: This study demonstrated that the one-step dynamic analysis is an effective method for investigating the growth and survival kinetics of foodborne pathogens. The results obtained from this study can be used to predict the growth of Salmonella Enteritidis in liquid egg whites and to conduct risk assessment of this pathogen.