Inactivation of Listeria monocytogenes in ready-to-consume liquid infant milk treated with Ohmic Heating

Abstract

Ohmic heating is a promising alternative method to conventional heating for microbial inactivation. This study aimed to inactivate Listeria monocytogenes and assess some quality parameters in ready-to-consume liquid infant milk treated with different voltage gradients of ohmic heating. Different ohmic heating voltage gradients (5, 10, and 20V cm^-1) were applied to the samples inoculated with Listeria monocytogenes (ATCC 13932) for 5 minutes. The application of 20 V cm^-1 ohmic heating induced inactivation of Listeria monocytogenes at 4 minutes and resulted in approximately 5.34 log reduction; however, there was no significant reduction for the 5 and 10V cm^-1 groups. Moreover, 20V cm^-1 ohmic heating application did not cause any changes in pH, L*, and b* values. A significant decrease in a* value and an increase in hydroxymethylfurfural value was noted in this group.  In conclusion, the effectiveness of ohmic heating in pathogen inactivation depends on the applied electric field intensity and the application time. As a result, the ohmic heating conditions must be carefully determined for the infant milk to inactivate pathogens and ensure public health protection. The results of this study contain significant and beneficial data that can be disposed of the listeriosis risk associated with the consumption of infant milk in infants.