Application of pulsed electric field prior to vacuum drying: Effect on drying time and quality of apple tissue

Abstract

The study aimed to determine the influence of a pulsed electric field (PEF) treatment on vacuum drying (VD) of apples and their selected quality parameters. The apples were treated with a PEF at 1 kV cm-1(with a variable amount of the specific energy input: 1, 3.5, and 6 kJ kg-1) before VD at 4 kPa (with a variable drying temperature: 40°C, 55°C, and 70°C). The drying time, microstructure, retention of total phenolics (TPC) as well as the antioxidant activity of the obtained dried materials were studied. As a result of opening the cell structure of the apple tissues, the PEF significantly (P < 0.05) reduced the drying time - depending on the used process parameters - by 6-22%. Moreover, an increase in the drying temperature also shortened the drying time. The electroporation led to obtaining porous materials after drying, and with the higher amount of specific energy during the PEF pre-treatment that was applied, a higher porosity was observed in the dried apples. After the PEF-assisted VD, a significant (P < 0.05) decrease in the TPC (by 12-40%) and antioxidant activity (by 23-81%) were observed.