The energy loss is the sum of the heat required to heat up the test cell, the heat loss to the surroundings by natural convection, the heat loss for physical, chemical and electrochemical changes of juice, and the electrical energy which has not been converted into heat. The energy loss calculations for the experimental data were performed by using the method in Icier and Ilicali (2005b). The heat loss to the surroundings by natural convection was calculated from the following equation