Comparison of Conventional Heating and Ohmic Heating Sheep Milk Processing: Impact on Listeria monocytogenes, Escherichia coli O157:H7 and Aflatoxin M1

This study aimed to assess the impact of conventional heat processing (CH) at isothermal conditions (55, 60, 65, 70 or 73 °C) and ohmic heating processing (OH) at distinct electric field strength (3.33; 5.83; 8.33 V/cm) on L. monocytogenes and E. coli O157:H7 inactivation and aflatoxin M1 decontamination in sheep milk. The superior efficiency of OH over CH on bacteria inactivation was likely due to electroporation (OH × CH, p < 0.05). For example, OH treatments caused 7 log 10 CFU/mL reduction of E. coli O157:H7 after 30 min at 55 °C, while CH caused less than 5 log 10 CFU/mL reduction. Also, OH caused a 6 log 10 CFU/mL reduction of L. monocytogenes when conducted at 65 °C for 4.5 min, while CH caused a 5 log 10 CFU/mL reduction. L. monocytogenes was more resistant to heat and electrical current than E. coli O157:H7. CH and OH did not impact the aflatoxin concentration initially inoculated in sheep milk. Thus, this study showed the application of OH in different times/temperatures that could help the dairy industry develop protocols to enhance food safety, reducing processing time and energy consumption of sheep milk.