Influence of pulsed electric field (PEF) pre-treatment on the convective drying kinetics of onions

This work discusses the effect of pulsed electric field (PEF) parameters on the convective drying process of fresh onions. First, the PEF treatment parameters and their influence on the cell disruption were investigated by applying various PEF settings (W = 0.2-20.0 kJ/kg, E = 0.36-1.07 kV/cm). The diffusion coefficient De was calculated and mathematic modeling was conducted. PEF was found to enhance the internal diffusion, but not necessarily to result in an increased drying rate. The shortest drying time at a drying temperature of 60 °C was achieved for onion samples treated at 4 kJ/kg and 1.07 kV/cm. Subsequent drying trials were performed at the pre-determined PEF settings and different drying temperatures resulting in a PEF related drying time reduction of 30.3%, 21.4% and 6.4% at 45 °C, 60 °C and 75 °C to reach a residual moisture (Mr) of 7%, respectively.