Influence of Pulsed Electroplasmolysis on the Porous Structure of Apple Tissue

The major interest in pulsed electric field (PEF) treatment of biological tissues is derived from its non-thermal applications in inducing increased cell permeability. This application has important implications in extraction and dehydration processes. Experimental investigation of the influence of PEF treatment on morphological changes in apple tissue during PEF plasmolysis is reported. Cylindrical McIntosh apple slices of about 57 mm by 15 mm dimension were placed in a laboratory treatment cell and exposed to electric field strength of 1000 V cm−1, pulse duration of 300 μs, pulse frequency of 1 Hz, and number of pulses of 60. Density, porosity and pore size distribution of dried samples were measured using a mercury porosimeter. The investigation revealed significant (at the 5% level) increase in apple tissue porosity from 63% for the control samples to 69% after electric field treatment. Sizes of the induced pores were mostly smaller than the average sizes of pores in the untreated samples. The sizes of the PEF-induced pores were comparable with the tissue cell wall thickness. The results show that electroplasmolysis affects not only plasmalemma membranes but also cell wall integrity of samples.