Supercritical carbon dioxide extraction of caffeine from Guarana

A single-pass system was designed to study extraction of caffeine from wet guarana seeds using supercritical carbon dioxide. Extraction was studied as a function of pressure and temperature to determine caffeine solubility at equilibrium conditions between 136.1 and 272.2 atm and temperatures of 35, 45, and 55 degrees C. Solubility of caffeine into supercritical CO2 was affected directly by CO2 density. Caffeine solubility was modeled by using thermodynamic relationships and the Peng-Robinson equation of state on a water-free basis. Effective diffusion coefficients of caffeine in ground guarana seeds were determined by conducting long-term extraction experiments.