Extraction of caffeine from guaraná seed with supercritical carbon dioxide

A single-pass supercritical fluid extraction system was designed to study caffeine solubility in the fluid. Caffeine was extracted from guaraná seeds with supercritical carbon dioxide in the system. Extraction was conducted as a function of pressure and temperature to determine caffeine solubility at equilibrium conditions at 136.1-272.2 atm and 308, 318, and 328 K. The solution of caffeine into supercritical carbon dioxide was directly affected by carbon dioxide density. Caffeine solubility was modelled by using thermodynamic relationships and Peng-Robinson equation of state. Effective diffusion coefficients of caffeine were determined by conducting long-term extraction experiments on ground guaraná seeds.