Application of electrical treatments in alcoholic solvent for polyphenols extraction from grape seeds

Abstract

The polyphenols extraction from grape seeds was studied. In order to increase the polyphenols yield and the extraction kinetics, three different pre-treatments were applied on grape seeds: pulsed electric fields (PEF) (8–20 kV/cm, 0–20 ms), high-voltage electrical discharges (HVED) (10 kA/40 kV, 1 ms) and grinding (180 W, 40 s). These electrical treatments can damage cell membranes (PEF/HVED) and cell walls (HVED) thus accelerating the compounds extraction but have different effects on the product fragmentation. The diffusion was then performed after pre-treatment with a mixture of water and ethanol. The PEF efficiency was improved when the treatment was performed at 50 °C in the presence of ethanol. PEF-assisted diffusion was then compared to HVED-assisted diffusion and to diffusion of ground grape seeds. These two pre-treatments increased both the extraction kinetics and the maximum polyphenols yield. For both cases, the final polyphenols content was 9 g GAE/100 g DM after 15 min of extraction with grinding and after 60 min with HVED. When PEF were applied in a suspension containing ethanol, the maximum polyphenols yield was also reached after 60 min. The subsequent solid–liquid separation was faster with PEF as compared to ground and HVED-treatments.