A study on electrical conductivity and performance evaluation of ohmic evaporation process of grape juice.

Examination of the Ohmic evaporation process in terms of electrical conductivity value and laws of thermodynamics is limited in the literature. In this study, the moisture content of the grape juice sample was concentrated from 5.75 kg water/kg Dry‐Matter (DM) to approximately 2 ± 0.3 kg water/kg DM by an ohmic evaporator. Evaporation process was applied in three different voltage gradients (16–24 V/cm) by Ohmic evaporator. The electrical conductivity value was found to be between 0.21 and 0.77 S/m during the heating process while it was between 0.77 and 1.01 S/m during the evaporation process. In addition, when evaluating this process concerning thermodynamic laws, it was stated that increasing voltage gradient had a positive effect on energy efficiency, exergy efficiency, and improvement potential values. To conclude, it was achieved that the ohmic heating‐assisted evaporation process could be used in the concentration of grape juice and an effective system with an average of 80% energy efficiency. Practical applications: As the ohmic heating process is known as a homogeneous, rapid, and efficient heating technique, its use in food applications is gradually increasing in recent years. Evaporation process is one of the preservation methods used especially in the fruit juice industry. An alternative evaporation method has been obtained by integrating the ohmic heating process into the evaporation process. It was determined that the voltage gradient used and foam formation were an effect on the electrical conductivity and performance analyses. It was determined that as the voltage gradient increased, the amount of water removed from the grape juice increased (kg/s) and the total processing time shortened. It is considered that this study may be a data source in the literature related to pilot and industrial‐scale production lines by determining electrical conductivity value during the evaporation of grape juice and investigating energy efficiencies. [ABSTRACT FROM AUTHOR]