Comparative Effects of Ohmic and Conventional Heating for Inactivation of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium, and Listeria monocytogenes in Skim Milk and Cream

Abstract

Ohmic heating has proven advantages over conventional thermal processing and novel thermal alternative technologies. In this study, the effect of ohmic and conventional heating for pasteurizing skim milk and cream was examined. All treatment conditions for ohmic and conventional heating were identical except for composition of the heating chamber. In most cases, the reduction of three pathogens did not differ significantly between ohmic heating and conventional heating at fixed treatment temperatures and times. However, temperature can be increased more rapidly with ohmic than with conventional heating treatment, both in skim milk and in cream. Therefore, E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes were inactivated more effectively by ohmic heating treatment for the same treatment time intervals. Also, the time required for pathogen populations to decrease to below the detection limit was less for ohmic heating than conventional heating. Quality aspects (viscosity, pH, and color) of skim milk and cream suffered less degradation by ohmic than by conventional heating. Although there was little evidence of a nonthermal effect of ohmic heating, the results demonstrate significant advantages in the use of ohmic heating over conventional methods for pasteurizing skim milk and cream.