Interaction of apple polyphenols in a multi-compound system upon adsorption onto a food-grade resin

Adsorption of catechin, caffeic acid, chlorogenic acid, phloridzin and rutin from multi-compound model solutions onto Amberlite® XAD 16HP was studied in laboratory experiments. The adsorption conditions were adapted to those optimal for single compound binding, which were determined in previous studies. The following order of affinity towards the styrene–divinylbenzene copolymer was determined: caffeic acid < catechin < chlorogenic acid < phloridzin < rutin, and the data also reveal significant interactions of the phenolics upon adsorption from multi-compound solutions. The affinity order was successfully derived from differences in the consecutive phases of the adsorption kinetics of individual phenolic compounds. At the very beginning of adsorption polyphenol binding is characterized by processes, which may result in the formation of a subsurface surrounding the resin particles and which precede surface reactions, whereas the final phase is dominated by intraparticle diffusion processes. The results presented in this work contribute to a better understanding of the complexity of adsorption mechanisms and of the influence of adsorption conditions. Thus, detailed evaluation of such complex systems may contribute to optimize the selective recovery of plant secondary metabolites, e.g. by providing phloridzin-enriched extracts with promising health-promoting properties.