High voltage electrical discharge (HVED)
HVED is a green extraction technique and is based on the physical and
chemical process which occurs when energy directly in aqueous solution
through the plasma channel formed between electrodes that are immersed
in water, is interjected [98, 99]. HVED in liquids causes disrupts
cell tissues, resulting in the release of valuable plant compounds. This
extraction system can be divided into three different categories:
discontinuous, continuous and eddy currents systems. The basis of these
systems is similar: discharge due to high intensity spatial electric
field, cell destruction and increased mass transfer due to various
secondary phenomena and their differences were related to the structure
of the systems, especially the electrodes, and focus modes of the
spatial electric field. This is the process of dielectric decomposition
resulting from liquid ionization and occurs with high voltage (30-40 kV)
and intensity (approximately 10 kA) short pulse between two electrodes.
The process mechanism summarizes the following steps: Electric pulse
generation, Electrostatic discharge, formation Electric arc. Some of the
main advantages of HVED technology over conventional methods are: higher
extraction rate, reduced process time, higher mass transfer, reduced
process temperature and solvent consumption, reduced degradation of
compounds sensitive to heat and environmental impacts, saving energy and
etc. [100].
The main difference between PEF and HVED is the geometry and composition
of their electrodes. Figurec15 gives a description of HVED and PEF
extraction methods (figure 16) [78].