Abstract
The aim of this study was to evaluate the ability of pulsed electric field (PEF) technology to improve the extractability and enhance the oil quality in an industrial olive oil extraction process. Using a PEF device on olive pastes significantly increased the extractability from 79.5% for the control, up to 85.5%. The PEF system did not modify the primary legal quality parameters or total concentrations of phenols, aldehydes, and esters. On the contrary, the non-thermal treatment slightly enhanced the dialdehydic forms of decarboxymethyl elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and tyrosol (p-HPEA-EDA), and decreased the total saturated and unsaturated C5 and C6 alcohols of the PEF EVOO (Extra Virgin Olive Oil) compared to the control test. This study confirmed that PEF technology can improve olive oil extraction and quality.
Highlights
The Pulsed electric field (PEF) treatment of olive paste delivered a significant reduction in pomace oil loss of about 40.5%. This confirmed the results reported in Puértolas and Martínez de Marañón [30], where a PEF treatment (2 kV/cm; 11.25 kJ/kg) was applied to Arroniz-variety olive paste
Regarding the evaluation of extractability, the PEF device has proved to be very efficient on olive pastes, and significantly increased the quantity of oil extracted compared to the control
From a plant engineering perspective, a PEF device used during experimental tests demonstrated easy assembly and implementation inside the mill without substantially modifying the basic layout
Summary
Pulsed electric field (PEF) technology is based on the application of high-intensity pulsed electric fields with durations of microseconds to milliseconds, and on the order of 10–80 kV/cm [1].Regarding the interaction between a PEF and organic matter, the dielectric rupture theory introduced in Zimmermann [2] known as electroporation, in which exposure of the cell membrane to an electric field causes an increase in transmembrane potential (TMP) leading to the formation of pores in weak areas of the membrane, is generally accepted.According to the intensity of the field strength, electroporation can be reversible or irreversible [3].Generally, 0.5–1.5 kV/cm is used for reversible electroporation, and 1.0–3.0 kV/cm is used for irreversible permeabilisation, while values above 15 kV/cm cause microbial inactivation [4].The main components of a PEF processing system are: (1) a high-voltage power generator, consisting of a high-voltage power supply, an energy storage capacitor bank, a charging-current-limiting resistor, and a switch to discharge energy from the capacitor; (2) a treatment chamber constituted of two electrodes separated by an insulator to confine the product to be treated; (3) a fluid-handling system (pumps, water tanks, pipes, and valves); and (4) a control system for monitoring the process [5].Based on the electrical circuit composed of power supplies, switches, resistors, capacitors, inductors, and the treatment chambers, which constitutes the pulse-forming network (PFN), it is possible to. According to the intensity of the field strength, electroporation can be reversible or irreversible [3]. The main components of a PEF processing system are: (1) a high-voltage power generator, consisting of a high-voltage power supply, an energy storage capacitor bank, a charging-current-limiting resistor, and a switch to discharge energy from the capacitor; (2) a treatment chamber constituted of two electrodes separated by an insulator to confine the product to be treated; (3) a fluid-handling system (pumps, water tanks, pipes, and valves); and (4) a control system for monitoring the process [5]. Based on the electrical circuit composed of power supplies, switches, resistors, capacitors, inductors, and the treatment chambers, which constitutes the pulse-forming network (PFN), it is possible to
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