Use of Pulsed Electric Field Pre-treatment to Accelerate Drying and Rehydration of Plant Foods

Pulsed electric field is a new non-thermal and environmentally friendly technology with diverse applications in food processing. Among the advantages of PEF are its low energy consumption, fast processing and less or no negative effect on the nutritional value of foods. The effect of Pulsed Electric Field (PEF) on the permeabilization of plant cells prior to hot air drying was investigated. Plant materials (grape, plum, and asparagus) were pre-treated using a Pulsed Electric Field at different pulse numbers and then dried in a hot air oven, vacuum dryer and fluidized bed dryer respectively. The texture measurement was carried out using a texture analyser (Stable Microsystem Analayser SMS, Haselmere, England). For drying of the sample was the following dryer equipment applied: A fluidized bed dryer (ATP, Berlin, Germany). Pulsed Electric Field treatment induced cell permeabilization of investigated plant material (grape, plum and asparagus). The degree of cell permeabilization (Zp) increased with increasing pulse number. An increase in Zp decreased the tissue hardness. Drying time for grapes, plums and asparagus was decreased drastically after PEF treatment at a field strength of 1kV/cm and 100 pulses. Up to 50 % and 25% shorter drying time was achieved after PEF pre-treatment for grapes and plum receptively. The PEF pre-treated grapes showed less browning after drying compared to the untreated dried sample. In addition, Pulsed Electric Field pre-treated grapes and plums showed a distinct higher rehydration rate compared to untreated samples. The results of this research highlight the advantage of Pulsed Electric Field pre-treatment for the acceleration of the drying rate of plant foods.