ENHANCEMENT OF PRESSING OF SUGAR BEET CUTS BY COMBINED OHMIC HEATING AND PULSED ELECTRIC FIELD TREATMENT

Abstract

This article describes the influence of combined ohmic heating (OH) and pulsed electric field (PEF) treatment on the juice extraction from sugar beet cuts of different sizes. The experiments were carried out on a laboratory filter-press cell connected to OH and PEF-treatment systems. OH (60 V/cm, 50 Hz) was used to attain different temperatures (30–70C), which were maintained during a fixed time (10–30 min). It was followed by a PEF treatment (600 V/cm, 0.04 s). OH noticeably enhances the extraction kinetics even at a moderate temperature of 50C. With the increase of OH temperature to 60C, the juice yield obtained by pressing is comparable to the one obtained after PEF treatment. The results show that combining OH and PEF treatment leads to some synergetic effect, promoting 85–87% of juice extraction even from middle and coarse cuts. This effect might result from both the electropermeabilization of cell membranes and the thermal softening of tissues.