Enhancement of the solid-liquid extraction of sucrose from sugar beet (Beta vulgaris) by pulsed electric fields

A systematic study of the impact of pulsed electric fields (PEF) parameters (1–7 kV/cm, 5–40 pulses, specific energy of 0.006–0.19 kJ/kg per pulse, pulse frequency of 1–10 Hz, pulse width of 2–5 μs, square and exponential decay pulses) on the kinetics of the sucrose extraction from sugar beet at different temperatures (20–70 °C) has been carried out in this investigation. The efficiency of the solid-liquid extraction was independent of the frequency, as well as of the pulse width, and the pulse shape at 7 kV/cm, and it was influenced by the electric field strength applied and by the temperature of the extracting medium. Sucrose yield increased with both field strength, time of extraction, and temperature. The effect of the field strength was higher the lower the temperature. The application of 20 pulses at 7 kV/cm (3.9 kJ/kg) increased the maximum yield by 7 and 1.6 times, compared to non-PEF-treated samples, at 20 and 40 °C, respectively. A mathematical expression was generated, which enabled to evaluate the influence of the electric field strength (from 0 to 7 kV/cm) and temperature (from 20 to 70 °C) on the sucrose extraction efficiency and the extracting time in a solid-liquid PEF-assisted sucrose extraction process. Based on this equation, for 80%-sucrose extraction in 60 min, the temperature could be reduced from 70 °C to 40 °C, when 20 pulses of 7 kV/cm were applied.