Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2003
Publication Date: 7/12/2003
Citation: Juneja, V.K. 2003. Predictive model for the combined effect of temperature, sodium lactate, and sodium diacetate on the heat resistance of Listeria monocytogenes in beef. (Abstract). Institute of Food Technologists. 60C-17.
Technical Abstract: Listeria monocytogenes continues to be one of the most important foodborne psychrotrophic pathogens of public health significance and a major concern to the food industry and regulatory agencies. Sodium lactate (NaL) and sodium diacetate (SDA) are generally regarded as safe and are used in meat products as direct, natural ingredients. Thermal inactivation kinetics models to predict L. monocytogenes survival within a specific range of NaL and SDA levels, used as food formulation variables, have not been developed. Accordingly, the effects and interactions of heating temperature (60 - 73.9C), NaL (0.0 - 4.8%, w/w) and/or SDA (0.0 - 0.25%, w/w) on the heat resistance of a five strain - mixture of L. monocytogenes in 75% lean ground beef were examined. Thermal death times were determined in filtered stomacher bags using a circulating water bath. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order response surface regression for temperature, NaL and SDA levels. A mathematical model describing the combined effect of temperature, NaL and SDA levels on the thermal inactivation of L. monocytogenes was developed. The D-values at 60, 65, 71.1 and 73.9C for beef with no NaL or SDA present were 4.67, 0.72, 0.17 and 0.04 min, respectively. Addition of 4.8% NaL in beef increased heat resistance at all temperatures; the D-values ranged from 14.3 min at 60C to 0.13 min at 73.9C. Sodium diacetate interacted with NaL, thereby reducing the protective effect of NaL and rendering L. monocytogenes in beef less resistant to heat. The model can predict D-values for any combinations of temperature, NaL and SDA that are within the range of those tested and will be incorporated into the USDA-Pathogen Modeling Program. The model will have substantial practical importance to food processors of cooked meat, allowing them to vary their thermal treatment of ready-to-eat meat products in a safe manner.