|Marks, Harry - USDA-FSIS|
Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2005
Publication Date: March 1, 2006
Citation: Juneja, V.K., Marks, H.M. 2006. Growth kinetics of salmonella spp. pre-and-post-thermal treatment. International Journal of Food Microbiology. 109:54-59. Interpretive Summary: Microbial Risk assessments (MRA) are used by USDA-Food Safety Inspection Service in establishing performance standards or guidelines that, if followed, are assumed to provide a safe product. An important step in the exposure assessment analysis component of the MRA is the determination of the likelihood of cells surviving a lethality treatment and then (re)growing to high levels that might cause illness, if consumed. We have modeled this latter possibility by assessing the growth kinetics of Salmonella both before and after thermal treatment. For the temperatures studied (25 and 37C), the results indicated that lag phase duration of the pathogen after thermal treatment increased by 5 h. The information will be of immediate use to the food industry and regulatory agencies to aid in the development of guidelines on how the foods are processed, and will ensure safety of the food supply.
Technical Abstract: This paper reports estimated growth kinetic parameters for stationary phase Salmonella cells, pre and post- thermal inactivation treatment. Cells were grown in brain-heart infusion broth at 25ºC or 37ºC and then destruction of the cells was quantified at 55ºC using a submerged coil heating apparatus. The surviving cells (about 2 log10 cfu/ml) were subsequently grown at 25ºC or 37ºC. The results indicated that lag phase duration times for the post-treated cells increased by about 6 hours and 4 hours, respectively, or by an average of 5 h, versus the pre-treated cells. Also, results were inconsistent regarding observed differences for the estimated exponential growth rates between pre- and post-treated cells. Additional studies are needed to characterize the effect of thermal treatment on the exponential growth rate kinetics.