Chyer Kim, Rana Alrefaei, Mariam Bushlaibi, Eunice Ndegwa, Paul Kaseloo, Crystal Wynn
Accurate prediction of the thermal destruction rate of foodborne pathogens is important for food processors to ensure proper food safety. When bacteria are subjected to thermal stress during storage, sublethal stresses and/or thermal acclimation may lead to differences in their subsequent tolerance to thermal treatment. The aim of the current study was to evaluate the thermal tolerance of O157:H7, , , and that are incubated during overnight growth in tryptic soy broth at four temperatures (15, 25, 35, and 45°C). Following incubation, the bacteria were subjected to thermal treatments at 55, 60, and 65°C. At the end of each treatment time, bacterial survival was quantified and further calculated for the thermal death decimal reduction time (value) and thermal destruction temperature (value) using a linear model for thermal treatment time (min) vs. microbial population (Log CFU/ml) and thermal treatment temperature (°C) vs. value, respectively, for each bacterium. Among the four bacterial species, generally had longer values and lower values than did other bacteria. Increasing patterns of and values in were obtained with the increment of incubation temperatures from 15 to 45°C. The values of (6.19°C), (6.73°C), (7.10°C), and (7.26°C) were the highest at 15, 25, 35, and 45°C, respectively. Although further research is needed to validate the findings on food matrix, findings in this study clearly affirm that adaptation of bacteria to certain stresses may reduce the effectiveness of preservation hurdles applied during later stages of food processing and storage.
