Abdullatif Tay, Rico Suhalim, Erdogan Ceylan
This study investigated the thermal inactivation kinetics of three pathogens, Salmonella, Escherichia coli, Listeria monocytogenes, and a surrogate microorganism Enterococcus faecium during oil frying of potato pellets at varying moisture contents of 5.4, 10.0, 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 exhibited superior thermal resistance compared to both E. coli and L. monocytogenes. At 14.4% moisture content, Salmonella D-values were determined to be 1.93, 0.85, and 0.45 min at 88 ,92 , and 96 °C, respectively. When moisture content was reduced to 5.4%, Salmonella displayed increased thermal resistance, with D-values of 2.38, 1.2, and 0.72 min at 89, 92, and 98 °C. Notably, E. faecium emerged as the most heat-resistant microorganism among all tested species, exhibiting D-values of 1.06, 0.65, and 0.31 min at 98, 103, and 108 °C in 5.4% moisture samples. Comparative analysis revealed that E. faecium demonstrated 1.6-fold greater heat resistance than Salmonella at 5.4% moisture, and 2.8- to 5.4-fold greater resistance at 14.4% moisture across 90-110 °C. 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 and Salmonella, respectively, after 6 seconds 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 as a suitable surrogate organism for in-plant validation studies of fried, low-moisture products such as potato pellets.