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item Juneja, Vijay

Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2004
Publication Date: 6/1/2005
Citation: Juneja, V.K., Marks, H.M. 2005. Heat resistance kinetics variation among various isolates of escherichia coli. Innovative Food Science and EmergingTechnologies. 6:155-161.

Interpretive Summary: A study was conducted to investigate the effects of different serotypes of E. coli on their destruction by heat in beef gravy. It is hypothesized that the ability of a bacterial cell to resist destruction by heat varies with bacterial strains. A new mathematical model was developed to predict relative heat destruction of various strains. Serotype-specific lethalities for 1 million cells at 60C is expected to range between 6 - 12 min. 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 an investigation of serotype-specific differences in heat resistance kinetics of clinical and food isolates of Escherichia coli. Heat resistance kinetics for 5 serotypes of E. coli at 60 °C were estimated in beef gravy using a submerged coil heating apparatus. The observed survival curves were sigmoidal and there were significant differences (p = 0.05) of the survival curves among the serotypes. Consequently, a model was developed that accounted for the sigmoidal shape of the survival curves and the serotype effects. Specifically, variance components for serotypes and replicates within serotypes were estimated using mixed effect nonlinear modeling. If it is assumed that the studied serotypes represent a random sample from a population of E. coli strains or serotypes, then, from the derived estimates, probability intervals of the expected lethality for random selected serotypes can be computed. For example, expected serotype-specific lethalities at 60 °C for 10 min are estimated to range between 5 and 9 log10 with 95% probability. On the other hand, to obtain a 6-log10 lethality, the expected minutes range, with 95% probability, from 6 to 12 min. The results from this study show that serotypes of E. coli display a wide range of heat resistance with nonlinear survival curves.