Electrically Assisted Extraction of Soluble Matter from Chardonnay Grape Skins for Polyphenol Recovery

The objective of this study was to investigate the effects of pulsed electric field (PEF) and high-voltage electrical discharges (HVED) application on the efficiency of aqueous extraction of total soluble matter and polyphenols from grape skins (Vitis vinifera L.) at different temperatures within 20−60 °C. The highest level of polyphenol concentration C was reached after about 60 min of extraction for HVED treatment: C HVED = 21.4 ± 0.8 μmol of gallic acid equivalent (GAE)/g of dry matter (DM). Almost the same level of C was reached after 180 min of extraction for the PEF-treated skins. These levels exceeded the value C = 19.1 ± 0.5 μmol of GAE/g of DM for the untreated samples. The difference between °Brix values for HVED-treated and untreated systems decreased with temperature increase (from 40 to 60 °C), but a large difference in the total amount of polyphenols was observed for HVED-treated and untreated systems. The activation energies were W u = 31.3 ± 3.7 kJ/mol and W PEF = 28.9 ± 5.5 kJ/mol for untreated and PEF-treated systems, respectively.