Effects of Electrode Type and Voltage Gradient on Grape Juice Concentration by Ohmic Heating Method

Nowadays, energy efficient systems are needed for concentrated juice production. Ohmic heating is one of these systems. In this study, the effect of ohmic heating technique on parameters such as: types of electrode (stainless steel, aluminum and brass), voltage gradient (10, 14, 18 and 22 V/cm), electrical conductivity, heating rate, pH and energy consumption of grape juice samples in the temperature range of 26-90℃ was investigated. The results showed that the effect of voltage gradient was statistically significant on the electrical conductivity, ohmic heating time, heating rate, pH, energy consumption and system performance coefficient (SPC) (p < 0.05). The best efficiency (85.09%) was observed for stainless steel electrodes and 22V/cm voltage gradient. By increasing the voltage gradient in all three electrodes (stainless steel, aluminum and brass), the heating time and energy consumption decreased, but the performance of the system increased. As the voltage gradient increased, time, pH and specific energy consumption decreased. The increase in concentration of grape juice was significantly increased electrical conductivity. The effect of electrodes on the heating rate of grape juice concentrated was not statistically different.