Colloidal Gas Aphrons separation to obtain polyphenol rich fractions from artichoke agro-industrial discards

Abstract

Artichoke agro-industrial discards have proved an excellent source of polyphenolic compounds with high antioxidant capacity. The aim of this study was to further separate these bioactive molecules from an ethanolic extract by using Colloidal Gas Aphrons (CGAs) generated from a cationic surfactant, Cetyl trimethylammonium bromide, CTAB (1mM) and a nonionic one, Tween 20 (10mM). Total proteins, total sugars, total phenolic content (TPC), antioxidant capacity (AOC) and polyphenolic profile were determined in the crude extracts and CGA fractions. Highest recovery was obtained with the nonionic Tween 20 at CGA to feed volumetric ratio 5 (RE%=64) whereas the cationic CTAB proved more efficient (RE%=58) at the highest ratio studied here (ratio 11). Antioxidant capacity followed the same trend as the recovery of polyphenols and highest enrichment in antioxidant activity for each of the surfactants (1.5 for Tween 20 and 1.4 for CTAB) was obtained at those conditions that led to maximum recovery. Highest selectivity was obtained with CTAB. Electrostatic interactions drove the separation with the cationic surfactant whereas with Tween 20 hydrophobic interactions were predominant. Polyphenolic profile of feed and CGAs fractions comprised mainly mono and dicaffeoylquinic acids and a small proportion of flavones. In most of the cases no enrichment of any particular polyphenol was found in CGAs samples. However, with Tween and at ratios 5 and 11 CGAs were enriched in dicaffeoylquinic acid. Future research should focus on assessing if the surfactant could also offer any advantage to the formulation of these polyphenols.