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Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/2/2003 Publication Date: 5/10/2003 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. Journal of Food Protection. 66:804-811. Interpretive Summary: Listeria monocytogenes has become a pathogen of major concern for the food industry since documentation of its association with several outbreaks of foodborne illness. Undercooked meat and meat products are commonly implicated as transmission vehicles in these outbreaks. This emphasizes the need to better define and quantify the heat treatment given to these foods to provide an adequate degree of protection against survival of Listeria monocytogenes. We developed a mathematical model for predicting the destruction of this pathogen in beef. The model can be used to predict the time required at any temperature to kill a certain number of bacteria. This information will be of immediate use to consumers and to the food industry and regulatory agencies to aid in the development of guidelines to ensure safety of the food supply. Technical Abstract: The effects and interactions of heating temperature (60 - 73.9C), sodium lactate (NaL; 0.0 - 4.8%, w/w) and/or sodium diacetate SDA; 0.0 - 0.25%, w/w) on the heat resistance of a five-strain mixture of Listeria 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. The observed 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. A mathematical model describing the combined effect of temperature, NaL and SDA levels on the thermal inactivation of L. monocytogenes was developed. 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 predictive 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. |
