Kinetics Model Comparison for the Inactivation ofSalmonellaSerotypes Enteritidis and Oranienburg in 10% Salted Liquid Whole Egg

Abstract

The goal of this study was to determine the inactivation kinetics of Salmonella in commercial 10% salted liquid whole egg (LWE) to assist the U.S. Department of Agriculture in writing new liquid egg pasteurization guidelines. Current data are not sufficient for predicting thermal inactivation kinetics of Salmonella spp. for use in updating pasteurization guidelines for many types of liquid egg products, including salted LWE (SLWE). This is, in part, due to variations in Salmonella strains and changes in the processing of liquid egg products that have arisen in the past 40 years. Pasteurization guidelines are currently being reevaluated in light of recent risk assessments. Heat-resistant Salmonella serovars Enteritidis and Oranienburg were composited and mixed into 10% SLWE, resulting in final populations of approximately 5.7-7.8 log colony-forming units (CFU)/mL. Inoculated egg was injected into glass capillary tubes, flame-sealed, and heated in a water bath at 60, 62.2, 63.3, 64.3, or 66°C. Contents were surface-plated and incubated at 37°C for 24 h. Survival curves were not log-linear (log levels versus time), but decreased rapidly, and after initial periods became linear. Asymptotic decimal reduction values at each temperature were calculated from survivor curves with a minimum inactivation of 5.0 log CFU/mL. The asymptotic thermal D-values for SLWE were 3.47, 2.23, 1.79, 1.46, and 1.04 min at 60, 62.2, 63.3, 64.3, or 66°C, respectively. The calculated thermal z-value was 11.5°C. A model that predicts lethality for given times and temperatures that was developed predicted that the current pasteurization requirements for 10% SLWE (i.e., 63.3°C for 3.5 min, or 62.2°C for 6.2 min) are not sufficient to inactivate 7 log CFU/mL of Salmonella and only achieve approximately 4 log CFU/mL inactivation. This model will assist egg-products manufacturers and regulatory agencies in designing pasteurization processes to ensure product safety.