Drying of Potato Tissue Pretreated by Ohmic Heating

Abstract

The influence of the ohmic heating pretreatment on convective drying of potato tissue was investigated. The degree of material damage Z under the different modes of electrical treatment is studied and the electroporation phenomena is assumed to be the main reason of material disintegration. The relations between Z, electric field strength E, energy input W, and temperature of ohmic heating T are analyzed. Two different damage stages, short and long, are revealed in this study. It is shown that ohmic treatment at relatively low fields (E < 100 V/cm) results in incomplete damage of material, but allows to obtain material with high disintegration degree Z ≈ 0.7 at E > 70 V/cm. The electric field strength E and the total electric energy input W influence considerably the drying rate. The highest drying rates are always observed for more energy consuming freeze-thawed pretreatment, but the AC pretreatment seems to be promising for enhancing the air drying processes.

Keywords:

• Ohmic heating
• Potato
• Electrical conductivity
• Tissue disintegration
• Diffusion

ACKNOWLEDGEMENTS

The authors thank Dr. N.S. Pivovarova for her help with preparation of the manuscript.