Ohmic heating: A post production technology applied to tomato puree

In this study, ohmic heating treatment was applied to different volume by volume concentrations (100, 90, 80, 70 and 60%) of tomato puree. The puree was ohmically heated from 30 to 70°C at four different voltage gradients of 8, 6, 4 and 2V/cm for different concentrations. Measurements had been made on electrical conductivity, ohmic heating rate, pH and TSS. The voltage gradient and concentration had significant effect on electrical conductivity of tomato puree. Electrical conductivity and ohmic heating rate increased linearly with temperature, concentration and voltage gradient. The pH and TSS were also noted before and after heating. The treatment had no significant effect on pH and TSS values. With respect to system performance coefficient, as the concentration of tomato puree decreased the efficiency of ohmic heating apparatus shifted towards higher voltage gradient in the prescribed voltage range.