High intensity ultrasound assisted decaffeination process of coffee beans in aqueous medium.

The purpose of this study was to determine the influence of ultrasound intensity, pulse and temperature on extraction of caffeine, from Arabica coffee beans using water as solvent, and ultrasound frequency of 24 kHz. A central composite design was used, using ultrasound intensity (31.5-105 W cm-2), pulse (0.30-1) and extraction temperature of the extraction (30-60 °C) as independent factor. The caffeine recovery and caffeine diffusion coefficient were response variables. The ultrasound intensity and extraction temperature significantly influenced the caffeine recovery rate and the diffusion coefficient of caffeine. Activation energy of 48.95 kJ mol-1 for the caffeine diffusion coefficient in ultrasound assisted extraction was observed. The best results were obtained at 68.25-105 W cm-2 ultrasound intensity and 60 °C temperature, corresponding to caffeine recovery of 58.4-69.4% and diffusion coefficient of 8.92-10.57 × 10-11 m2 s-1. The pulse effect was not significant in the range of the studied variables.