Electrical Conductivity of Multicomponent Systems During Ohmic Heating

During ohmic heating, the heating rate of a product depends on its electrical conductivity, a temperature dependent property. The electrical conductivity of the individual components in a multicomponent food system was determined over the entire sterilization temperature range (25−140°C). The product selected was chicken chowmein, composed of chicken, celery, mushrooms, water chestnuts, bean sprouts, and chowmein-style sauce. A device was developed to measure electrical conductivities of the components over the required temperature range. Results showed that the sauce (2.1 S/m at 27°C to 10.8 S/m at 140°C) was much more conductive than the solid components, i.e., celery (0.1 S/m to 3.4 S/m), water chestnut (0.1 S/m to 2.8 S/m), mushrooms (0.2 S/m to 1.4 S/m), bean sprouts (0.2 S/m to 1.5 S/m) and chicken (0.6 S/m to 3.4 S/m). Variation in electrical conductivity was also observed between different samples of the same component.