“Cold” electroporation in potato tissue induced by pulsed electric field Original Research Article

This work compares PEF-induced effects in potato tissue at temperatures below and above ambient (T = 2–45 °C). The potato (Agata) was selected for investigation. The PEF treatment using electric field strength E = 200–800 V/cm and bipolar pulses of near-rectangular shape with pulse duration tp (=100 μs) was applied. The PEF experiments were done under non-isothermal conditions with temperature increase owing to the effect of ohmic heating. The linear temperature dependencies of electrical conductivity of potato tissue with different values of the electrical conductivity disintegration index, Z, were observed. However, the values of the conductivity temperature coefficient, α, at the reference temperature Tr = 25 °C were noticeably different for the intact (αi = 0.0255 ± 0.0003 °C−1) and completely damaged (αd = 0.031 ± 0.009 °C−1) potato tissues. This difference was explained by the impact of temperature on the structure of the damaged tissue. The non-isothermal PEF treatment was shown to be an effective tool for electroporation at low temperatures (below ambient). For initial temperature Ti = 2 °C, the most power saving was the PEF treatment at E = 200 V/cm (W ≈ 20–30 kJ/kg), and the PEF treatment at E = 400–800 V/cm required more power consumption (W ≈ 50–80 kJ/kg). The PEF treatment at the fixed value of E (=400 V/cm) showed that the total power consumptions (accounting for PEF treatment and thermal heating), required for high level of tissue disintegration, Z ≈ 0.9, were comparable for initial temperatures Ti = 2 °C (W ≈ 50–80 kJ/kg) and Ti = 20 °C (W ≈ 80 kJ/kg) and were noticeably higher for initial temperature Ti = 40 °C (W ≈ 150 kJ/kg).