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].