Effect of bubbling nitrogen and pulsed flow on the antiradical activity of grape residues

The efficiency of liquid–solid extraction of phenols from natural products was enhanced by effect of coupling certain arrangements with the conventional extraction process (control). In fact, whilst 2.20 g phenols/100 g sample were obtained from grape byproducts using the control system, values of 2.69 and 3.21 g of phenol/100 g sample were attained when process was carried out by passing bubbling nitrogen through the packed bed or by using pulsed flow solvent, respectively. Likewise, values of antiradical activity (measured by DPPH) were at least twofold higher than those of the control.HPLC analysis confirmed a delay in oxidative polymerization of phenols when bubbling nitrogen was used. The latter avoids the formation of high polymerization degree species and allows one to obtain extracts with higher antiradical capacity. Catechin, epicatechin, gallic acid and quercetin were the main monomeric phenols identified in the grape extracts obtained.