and Enterohemorrhagic Serogroups O45, O121, O145 in Wheat Flour: Effects of Long-Term Storage and Thermal Treatments.

and enterohemorrhagic (EHEC) are of serious concern in wheat flour and its related products but little is known on their survival and thermal death kinetics. This study was undertaken to determine their long-term viability and thermal inactivation kinetics in flour. Inoculation was performed using mixtures of EHEC serogroups O45, O121, O145 and followed by storage at room temperature (23°C) or 35°C (for ). Plate counting on tryptic soy agar (TSA) and enrichment were used to assess long-term survival. For thermal studies, wheat flour samples were heated at 55, 60, 65, and 70°C and cell counts of EHEC and were determined by plating. The δ-values were calculated using the Weibull model. At room temperature, EHEC serovars and were quantifiable for 84 and 112 days, and were detectable for the duration of the experiment after 168 and 365 days, respectively. The δ-values were 2.0, 5.54, and 9.3 days, for EHEC O121, O45, and O145, respectively, and 9.7 days for . However, the only significant difference among all values was the δ-value for and serogroup O121 ( ≤ 0.05). At 35°C, counts declined to unquantifiable levels after a week and were not detected upon enrichment after 98 days. Heat treatment of inoculated wheat flour at 55, 60, 65, and 70°C resulted in δ-value ranges of 20.0-42.9, 4.9-10.0, 2.4-3.2, and 0.2-1.6 min, respectively, for EHEC. The δ-values for at those temperatures were 152.2, 40.8, 17.9, and 17.4 min, respectively. The δ-values obtained for at each temperature were significantly longer than for EHEC ( ≤ 0.05). Weibull model was a good fit to describe the thermal death kinetics of and EHEC O45, O121 and O145 in wheat flour. -EHEC and can survive for extended periods of time in wheat flour.-Long-term storage inactivation curves of EHEC and were similar.-EHEC was more sensitive to heat than -Weibull model was a good fit to describe thermal death kinetics of EHEC and -Flour storage at 35°C may be a feasible method for microbial reduction.