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 degrees 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 mu mol 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 mu mol of GAE/g of DM for the untreated samples. The difference between degrees Brix values for HVED-treated and untreated systems decreased with temperature increase (from 40 to 60 degrees C), but a large difference in the total amount of polyphenols was observed for HVED-treated and untreated systems. The activation energies were W, = 31.3 +/- 3.7 kJ/mol and W-PEF = 28.9 +/- 5.5 kJ/mol for untreated and PEF-treated systems, respectively.