Scale-up of high voltage electrical discharges for polyphenols extraction from grape pomace: Effect of the dynamic shock waves

This work aims at producing high dynamic shock waves by high voltage electrical discharges (HVED) in a water suspension in order to increase polyphenols extraction from grape pomace. Experiments at the laboratory (1 L) and pilot (35 L) scales were compared. The total specific energy input was varied up to 800 kJ/kg. The intensification of the extraction of total polyphenols was increased 7 times from grape pomace, seeds, skins and stems treated by HVED at both laboratory and pilot scales. However, higher treatment energies are required at the pilot scale to obtain equivalent polyphenols rates. The pressure of the shock wave generated during HVED was measured. When applying the same specific energy input per pulse (EBm = 0.53 kJ/kg) at both scales, the entire volume of both treatment chambers is treated by shock waves of similar pressures values (≥ 100 bars). Below this pressure value, the shock waves seem to have no effect on the polyphenols extraction.Industrial relevance: This paper presents relevant information for the design of generating electrical discharges treatment. The study also addresses a specific case of use of by-products and shows the effectiveness of such technology at the laboratory and pilot scale.

► Electrical discharges are applied on grape pomace at laboratory and pilot scales.
► The effects of the energy input and the dynamic shock waves are studied.
► There exists an optimal energy input for polyphenols extraction.
► The shock waves of about 100 bars have an effect on the product fragmentation.