Evaluation of an ohmic assisted vacuum evaporation process for orange juice pulp

An ohmic assisted vacuum evaporation (OAVE) processes was used to concentrate orange juice from 11.4% total soluble solid content (TSSC) to 42% TSSC by applying 13 V/cm constant voltage gradient at different temperatures. The evaporation temperatures were adjusted to 100 °C, 85 °C, 75 °C and 65 °C by setting absolute system pressures of 101.32 kPa, 58 kPa, 39 kPa and 25 kPa, respectively. The total time for the processes, including heating and evaporation, was 34, 40, 48, and 54 min for 100, 85, 75, and 65 °C, respectively. As the evaporation temperature increased, the applied energy required for phase change decreased while maximum current values increased from 0.6 A at 65 °C to 2.52 A at 100 °C. During any given run, the current value increased as the orange juice pulp heated up, but then decreased after it began to boil, leading to a reduction in the rate of heat generation. Increasing evaporation temperature has a positive effect on evaporation rates, energy efficiency, specific water removal ratio (SWRR), exergy efficiency, and Improvement Potential (IP) (p < 0.05). The reduced energy requirement with higher temperature is partially due to reduced work from the vacuum pump at the higher absolute pressure.