Experimental Study of the Ohmic Heating Process in Two-Phase Biosolid-Liquid Systems

Ohmic heating as a novel heating method in biological, food and pharmaceutical industries especially in sterilization process was known. In this research, the Ohmic heating and effective parameters influences experimentally investigated. For investigation the Ohmic heating behavior, Hydrocolloid solutions in Ohmic cell in some stage have been used. First, electrical conductivity of hydrocolloid solution with 4, 5.5 and 6.33% concentration was studied and determined that reported that temperature increasing resulted increasing the electrical conductivity linearity. With increasing the dispersed concentration, electrical conductivity increased. In order to study the effect of salinity on the electrical conductivity, sodium chloride (0.25-1% concentration) was added and results showed that addition of salts, increases efficiency the electrical conductivity. In order to study the effect of electrolyte content on temperature-time profile and heating rates citric acid was added. Addition of salt into the solution has efficient effect on the temperature-time profile, that in solution with 3.3% concentration and 1% salinity reached 70 °C just after 253 s that records shorter time for increasing the temperature from 20 to 80 oC and highest electrical conductivity. The effect of electrolyte (acid) on temperature-time profile in comparison with salt is not considerable. With measuring the solution temperature with thermocouples in the cell, uniformity of heating throughout the solutions was studied. From experimental result, it can be resulted that Ohmic heating rate dependent to electrical field distribution and heating uniformity is dependent to current concentration and system geometry.