Inactivation of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, and Enterococcus faecium NRRL B-2354 in Oil-Fried Potato Pellets.

This study investigated the thermal inactivation kinetics of three pathogens, Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes, and a surrogate microorganism, Enterococcus faecium NRRL B-2354, during oil frying of potato pellets at varying moisture contents of 5.4, 10.6, and 14.4%. Thermal treatments were conducted across temperatures ranging from 80 to 108 °C to establish comparative heat resistance profiles. Experimental results demonstrated that Salmonella enterica exhibited superior thermal resistance compared to both E. coli O157:H7 and L. monocytogenes. At 14.4% moisture content, Salmonella enterica D-values were determined to be 1.05, 0.47, and 0.24 min at 80, 85, and 90 °C, respectively. When moisture content was reduced to 5.4%, Salmonella enterica displayed increased thermal resistance, with D-values of 2.38, 1.20, and 0.72 min at 89, 92, and 98 °C. Notably, E. faecium NRRL B-2354 was the most heat-resistant microorganism, exhibiting D-values of 1.06, 0.65, and 0.31 min at 98, 103, and 108 °C in 5.4% moisture samples. E. faecium NRRL B-2354 demonstrated at least 1.6-fold greater heat resistance than Salmonella enterica at all moisture and temperature conditions. Verification testing at 129 °C with 10.6% moisture content resulted in population reductions of 4.73 and 5.6 log CFU/g for E. faecium NRRL B-2354 and Salmonella enterica, respectively, after 6 s of treatment. These findings provide a scientific foundation for validation protocols in similar fried, low-moisture food products and substantiate the potential application of E. faecium NRRL B-2354 as a suitable surrogate organism for in-plant validation studies of oil-fried, low-moisture products such as potato pellets.