Processing treatments enhance the adsorption characteristics of epigallocatechin-3-gallate onto apple pomace

The adsorption capacity of epigallocatechin-3-gallate (EGCG) onto freeze dried and extruded apple pomace ground into powder was compared to that of wet apple pomace. The isothermal adsorption studies were carried out over a range of concentrations (100-1000 mg/L) and temperatures (25 °C, 40 °C and 55 °C). Freeze drying or extrusion of apple pomace enhanced its capacity to adsorb EGCG. Analyses of thermodynamic parameters showed that adsorption of EGCG to freeze dried pomace powder was an exothermic process whereas that to extruded pomace powder was endothermic. This is due to the altered character of the binding sites for EGCG as a result of process-induced changes, which contributed to different underlying mechanisms of binding of EGCG to the processed apple pomace. This suggests that the adsorption mechanism was dependent on the processing treatment used. Our study highlights that by choosing the appropriate processing treatments, the adsorption of EGCG to apple pomace could be improved.