Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2006
Publication Date: 7/1/2006
Citation: Schultze, K., Linton, R., Cousin, M., Luchansky, J.B., Tamplin, M.L. 2006. A predictive model to describe the effects of temperature, sodium lactate and sodium diacetate on the inactivation of a serotype 4b strain of listeria monocytogenes in a frankfurter slurry. Journal of Food Protection. Vol.69.No.7.2006. pges. 1552-1560. Interpretive Summary: Listeria monocytogenes (LM) is responsible for causing approximately 2,500 cases of listeriosis and 500 deaths in the United States each year. According to risk assessment, the consumption of ready-to-eat (RTE) deli meats and non-heated frankfurters are associated with the highest risk of contracting listeriosis on a per serving and per annum basis. To control LM in RTE food products, post-processing heat pasteurization can be used to reduce or eliminate the pathogen from product surfaces, and/or acidulants can be added to the product formulations to prevent growth of any LM survivors over the shelf life of the product. The addition of lactate and diacetate salts to product formulations have been successful in controlling the growth of LM during product shelf-life; however, there is interest in studying the effects of these compounds on LM heat resistance, especially at post-processing pasteurization temperatures. The objectives of this study were to develop a predictive model based on the effects of temperature, sodium lactate and sodium diacetate on the inactivation of LM in a frankfurter system. Results showed that increased temperature or sodium diacetate levels increased LM death rate, whereas, increased levels of sodium lactate decreased heat resistance. As both temperature and sodium lactate increased, the death rate decreased. As temperature and sodium diacetate increased, however, the death rate increased. These data provide important information for reducing and minimizing contamination during post processing thermal treatments.
Technical Abstract: A modified Gompertz equation was used to model the effects of temperature (55, 60, 65 deg C), sodium lactate (0, 2.4, 4.8%) and sodium diacetate (0, 0.125, 0.25%) on inactivation of Listeria monocytogenes (LM) strain MFS 102 (LM; serotype 4b) in frankfurter slurry. The effects of these factors were determined on the shouldering region (A parameter), maximum death rate (B parameter), and tailing region (C parameter) of microbial inactivation curves. Increased temperature or sodium diacetate levels increased the death rate; whereas, increased levels of sodium lactate decreased the death rate. Complex two-way interactive effects were also observed. As both temperature and sodium lactate increased, the death rate decreased; as temperature and sodium diacetate increased, however, the death rate increased. The interaction between sodium lactate and sodium diacetate on the maximum death rate varied with temperature. Increases in both acidulants at temperatures above 56.7 deg C decreased the death rate; at temperatures below 56.7 deg C, increases in both acidulants increased the death rate. To test for significant differences between treatments, D-values were calculated and compared. Using this comparison, in general, sodium lactate increased heat resistance and sodium diacetate decreased heat resistance of LM. These data provide information relative to reducing and minimizing contamination during post processing thermal treatments.