Effect of Voltage Gradient on Electrical Conductivity, Heating Rate and Energy Efficiency of Pineapple Juice during Ohmic Heating

Ohmic heating (OH) is an advanced electro-thermal technology that offers rapid and uniform volumetric heating by directly converting electrical energy into heat within conductive food matrices, with performance largely governed by the electrical conductivity (EC) of the product and the applied electric field strength. This study systematically investigated the electrical conductivity and heating rate behavior of pineapple juice under varying voltage gradients (10.35, 15.10, 20.21, and 25.25 V/cm) during OH at 50 Hz. Results demonstrated that EC increased linearly with temperature across all treatments, ranging from 0.45 S/m at 30°C to 0.88 S/m at 90°C, with higher voltage gradients marginally enhancing ion mobility and conductivity. Heating rates increased proportionally with voltage, rising from 0.8°C/s at 10.35 V/cm to 2.0°C/s at 25.25 V/cm, thereby reducing the time required to reach the target pasteurization temperature of 90°C by approximately 59% under the most intense field. Temperature–time profiles confirmed uniform heating with no significant thermal lag, validating OH’s volumetric advantage. Energy efficiency remained consistently high (>85%) across all voltage levels, with moderate gradients (15.10–20.21 V/cm) offering an optimal balance between rapid heating and energy utilization. These findings highlight the suitability of pineapple juice as an OH-compatible medium and underscore the critical role of voltage gradient in tuning process efficiency, providing a scientific basis for the industrial adoption of ohmic heating as an energy-conserving alternative to conventional thermal pasteurization.