Effect of Voltage Gradient and Temperature on Electrical Conductivity of Grape (Vitis vinifera L.) Juice during Ohmic Heating

Abstract

Ohmic heating is an alternative fast heating technique of foods. It is important to determine electrical conductivity in order to decide on the applicability of ohmic heating technology for specific food products. In this study, grape juice was heated at different voltage gradients 10, 20, 30 and 40 V cm-1 holding at different temperature 55, 65 75 and 85 oC using a laboratory scale static ohmic heating system. The effect of voltage gradient and temperature on electrical conductivity of grape juice was investigated. Electrical conductivity of grape juice samples was 0.25-0.81 S m-1 at 10-40 V cm-1 and 30-85 °C. The voltage gradient and temperature were statistically significant on the electrical conductivity for grape juice (p<0.05). As the voltage gradient was increased, electrical conductivity increased. The electrical conductivity of the sample linearly increased with temperature rise. The maximum EC of grape juice was found to be 0.81 S m-1 at 30 V cm-1 at 85 °C. Bubbling was observed at higher voltage gradients (40 V cm-1) at higher temperature, especially above 75 oC.