Title: Impact of chlorine, termperature and freezing shock on the growth behavior of Escherichia coli 0157:H7 on ready to eat meats Authors
Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 12, 2012
Publication Date: April 18, 2012
Citation: Sheen, S., Hwang, C., Juneja, V.K. 2012. Impact of chlorine, termperature and freezing shock on the growth behavior of Escherichia coli 0157:H7 on ready to eat meats. Food and Nutrition Sciences. DOI: 10.4236/fns.2012.34075. Interpretive Summary: Chlorine is the most commonly used chemical in sanitizing process equipment and utensils. Escherichia coli O157:H7 (Ec) may survive the treatment then contaminate food products. Storage temperature is another factor to significantly affect the microbial growth. This study demonstrated the impact of chlorine (0 – 50 ppm) and temperature (12– 24 deg C) on Ec growth and survival behavior on ready-to-eat meats. The higher chlorine concentration and lower temperature may significantly retard the Ec growth including longer lag time. Freezing shock was found almost no impact on the Ec growth. Models were developed to describe the Ec survival. These findings and models may enhance risk assessment for microbial safety as ready-to-eat meats.
Technical Abstract: Foodborne pathogens continue to pose a potential food safety hazard in ready-to-eat (RTE) meat. Chlorine is commonly used to sanitize processing equipment where Escherichia coli O157:H7 (Ec) may survive and contaminate food products. The objective of this study was to characterize the survival behavior of Ec with different stresses on RTE meats. A multi-strain cocktail of Ec was pre-treated with freezing shock for 15-20 h and/or chlorine (0, 25, and 50 ppm) for one hour, and then inoculated onto RTE meat surfaces to obtain about 3.0 log CFU/g. Samples were stored at three abuse temperatures (12, 18, and 24 deg C) and Ec was enumerated during the storage. The freezing shock impact was studied using the Ec cocktail stored in a freezer overnight followed by chlorine exposure for one hour. The lag phase and growth rate of Ec were estimated using DMFit (Combase, Baranyi’s model). Results indicated that Ec growth was suppressed by chlorine treatment. Freezing shock was found to have little impact in terms of lag time and growth rate. The lag phase of Ec after exposure to 0 ppm of chlorine (50.3 h) was shorter than that of Ec treated with 25 ppm (54.6 h) and 50 ppm (164.1 h) at 12 deg C. However, the lag phase decreased with an increase in temperature, e.g. at 25 ppm, lag times were 54.6, 51.1 and 48.9 h for 12, 18 and 24 deg C, respectively. Lag times increased with an increase in chlorine concentration. At 24 deg C, lag times were 15.8, 48.9, and 52.4 h for 0, 25, and 50 ppm, respectively. The growth rate increased with an increase in temperature for 0 and 25 ppm chlorine levels, but decreased at 50 ppm level. Growth rate and lag phase as a function of temperature and chlorine concentration can be described by polynomial models and modified Ratkowsky-type and Zwietering-type models. Results of this study will contribute to risk assessment of RTE meats.