Kinetic modelling of total phenolic compounds from Ilex paraguariensis (St. Hil.) leaves: Conventional and ultrasound assisted extraction

Abstract

In this paper, we compared ultrasound-assisted extraction (UAE) and conventional extraction by agitation (AE) for total phenolic compounds (TPC) extraction from yerba mate leaves (Ilex paraguariensis St. Hil). Water and 50% aqueous ethanol solution were used as solvent and the effect of solvent-to-solid ratio, particle size, stirring speed (AE) and ultrasound power amplitude (UAE) was examined. Two kinetic models (i.e. Peleg model and swelling / diffusion model) have been introduced to describe the kinetics of TPC extraction. The experimental data were adequately fitted by swelling/diffusion model (R2>0.98; EP<10%; RMSE<0.24) that considers two mechanisms coupled at different rates. The initial extraction rate increased at a higher volume of solvent (10 ml/g), smaller particle size (0.297 mm) higher ultrasound power amplitude (100%) and the use of 50% aqueous ethanol solution. Maximum equilibrium TPC concentration was observed with the synergic effect of 50% aqueous ethanol solution and the higher power amplitude (15,0 g GAE/100 g dm). This work would provide more information on the extraction mechanisms that occur in the microstructure of yerba mate leaves for the industrial production of TPC.