Effect of pulsed electric fields on physical properties of apples and potatoes

The application of pulsed electric fields (PEF) in food processing is a novel technique that requires careful study. In addition, improved understanding of the effect of PEF parameters on both physical and qualitative attributes of agrifood products is a requirement for the application and control of this emerging technology. PEF parameters investigated were pulse widths of 100, 200, and 300 mus, with electric field strengths of 0.75 and 1.5 kV/cm. The amount of pulses used for apples was up to 60, whereas up to 120 pulses were used for potatoes. Initially, apple and potato slices were exposed to various combinations of PEF parameters in order to evaluate the change in their electrical conductivities as an indicator of the disruption of the cell membrane. Subsequently, the impact of PEF on color and texture attributes was studied. In the final set of experiments, PEF was applied as a pre-treatment in order to accelerate the diffusion of moisture in a convective air-drying process at 70°C.Results regarding the electrical conductivity and the changes in color revealed the similar effect of applying pulses with 100, 200 and 300 mus of duration. Increasing the number of pulses and/or the electric field strength resulted in increased electrical conductivity and discoloration rates of samples. PEF reduced the compressive strength of apple tissues between 21 to 47%. However, the compressive strength of potato tissues did not seem to be affected by the application of PEF. When PEF was applied as a pre-treatment, it caused an increase of up to 30% in the moisture diffusion coefficients of potatoes. In the case of apples, PEF pre-treated samples did not show any increase in drying rates