Ultrasound assisted purification of polyphenols of apple skins by adsorption/desorption procedure.

The ultrasound (US) assisted purification of polyphenols of apple skins by adsorption/desorption on the poly-aromatic Amberlite adsorbent XAD-16 was studied. The adsorption steps were done at different temperatures (T = 25-40 °C) with application of US at different intensities (P = 0-400 W). The desorption steps were tested in aqueous ethanol solution at different concentrations of ethanol (Cet = 0-96%). The isotherm of polyphenol adsorption was well described using the Freundlich model. The data on adsorption kinetics and static isotherm evidenced the presence of adsorption on heterogeneous surface with broad distribution of adsorption times that can depend on content of polyphenols in the solutions and applied power of sonication. The studies of desorption revealed the optimum desorption efficiency of polyphenols at 50% concentration of ethanol. The desorption ratio was positively affected by the sonication during the adsorption step. The highest adsorption/desorption efficiency (recovery) was observed for polyphenols as compared with proteins and soluble matter content and it reached of ≈30.6% (0 W) and 68.9% (50 W) in absence and presence of sonication, respectively. The effects of high US power on the damage of XAD-16 were discussed. The obtained data evidenced on good perspective of application of adsorption/desorption procedure assisted by sonication for purification of polyphenols from apple skin extracts.