The ohmic and conventional heating methods in concentration of sour cherry juice: Quality and engineering factors

Abstract

In the present study, ohmic and conventional heating methods were applied to concentrate sour cherry juice. The heating rate of ohmic method increased ten-fold compared with conventional heating. The temperature gradient showed a 1.5 °C difference between the temperatures of the medium in the vicinity of the two electrodes. The electrical conductivity of sour cherry juice at voltage levels of 30–50 V ranged from 0.70 to 2.52 S/m. The higher values belonged to the end of the process and lower voltages. Acidity measurement showed no significant difference among the applied voltages in ohmic heating with the exception of 35 V. The effect of conventional heating on the color change of sour cherry juice was more than that of ohmic heating. • In sour cherry concentration by ohmic heating, a different temperature profile was detected near two electrodes. • The electrical conductivity had an increasing trend with moisture content at low applied voltage even near boiling point. • In terms of processing time and color changes (ΔE), higher voltages of ohmic heating can be recommended. • There were no significant differences among voltages of ohmic heating in terms of color parameters of “b” and “L”, and ΔE.