Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/13/2011
Publication Date: 3/1/2011
Citation: Gurtler, J., Marks, H.M., Jones, D.R., Bailey, R., Bauer, N.E. 2011. Thermal inactivation kinetics of heat-resistant Salmonella Enteritidis and Oranienberg in 10% salted liquid egg yolk. Journal of Food Protection. 74(6):882-892. Interpretive Summary: Salted liquid egg yolk is currently used in large quantities by the U.S. food industry as an ingredient in sauces, dressings and mayonnaise. The USDA Food Safety and Inspection Service (FSIS) requires that liquid egg yolk with 2 percent or more salt be thermally pasteurized at 63.3 degrees Celsius for 3.5 min to inactivate Salmonella. These conditions, however, may not be effective because of the different Salmonella strains and variations in liquid egg products and processing conditions that have arisen in the past 40 years. We tested the survival of heat resistant-Salmonella in 10% salted liquid egg yolk and developed a mathematical model describing the inactivation. This model indicates that salted liquid egg yolk now must be processed at 67.4 degrees C for 3.5 min in order to get at least 99.999 percent inactivation of Salmonella. These results may be used by liquid egg processors to ensure the safety of a popular product.
Technical Abstract: There is presently not sufficient data nor is there a suitable model for predicting thermal inactivation kinetics of Salmonella spp for many types of liquid egg products, including salted liquid egg yolk, for use in updating pasteurization guidelines, in part because of the different Salmonella strains and variations in liquid egg products and processing that have arisen in the past 40 years. The objectives of the present study were to determine the thermal inactivation kinetics and to create a general, thermal inactivation kinetics model that can be used for estimating log10 reductions of salmonellae in 10 percent salted liquid egg yolk for temperatures between 62.2 and 69 degrees C to be used by processors to help ensure adequate pasteurization. This was accomplished by studying the inactivation kinetics of a three-strain composite of heat-resistant Salmonella Enteritidis and Oranienberg inoculated into commercially-processed 10 percent salted liquid egg yolk. The survival curves were convex, with asymptotic D-values. From these curves, a general model was developed to predict log10 reductions for given times at specified temperatures. For example, at a temperature of 67.4 degrees C (153.1 degrees F) for 3.5 min, our model predicts a 5 log10 reduction would be obtained, whereas at the present required temperature of 63.33 degrees C (146 degrees F) for 3.5 min, our model predicts that a reduction of only 2.7 log10 would be achieved. The results of the study provide information that can be used by processors to aid in producing safe pasteurized egg yolk products and for satisfying pasteurization performance standards and developing industry guidance.