requires electrodes to be in good contact. this means that in practice the food should be liquid or have sufficient fluidity to allow both good contact with the electrodes and to pump the product through the heater
differences in the electrical conductivities of the liquid and solid components of multicomponent foods and variations in conductivity with increasing temperature, which can cause irregular and complex heating patterns and difficulties in predicting the heating characteristics
a lack of data on the critical factors that affect the rate of heating
a lact of accurate temperatue-monitoring techniques to profile heat distribution and locate cold-spots during the process