Effects of high-voltage electric field produced by an improved electrode system on freezing behaviors and selected properties of agarose gel

Abstract

This work aimed at evaluating the effects of high-voltage electric field (HVEF) produced by an improved electrode system on the freezing behaviors and selected properties of agarose gel. The freezing of the agarose gel was realized by a Peltier cooler coupled with an improved electrode system. The electrode system was integrated with a dielectric spacer having high permittivity to avoid partial discharges. Results showed that HVEF combined with a low freezing rate significantly reduced the supercooling degree, enhanced the average freezing rate in particular the nucleation rate, and higher internal electric field intensity showed a better microstructure with smaller ice crystals in frozen samples. Under the highest applied voltage of 9 kV (Ein = 1.09 E+05 V/m) tested in this study, a 100% supercooling release was achieved. Maximum reductions of 78.83%, 25.79% and 28.75% were observed for the nucleation time, tempering time and total freezing time, respectively, while the phase transition time was prolonged by 14.86% as compared with the control (p < 0.05). Some reinforcement was detected in the gel strength by increasing internal electric field intensity, but not significant enough to prevent the structural damage and syneresis caused by freezing and thawing. This study suggested that HVEF-assisted freezing was able to reduce the size of ice crystals formed in semi-solid model foods, and the integration of a dielectric spacer with high permittivity to the electrode could be used as a potential method to solve the electrical discharge problem.