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Abstract The extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous‐flow extraction apparatus. Decaffeination rates were determined as a function of CO 2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with a flame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO 2 saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was influenced by both intraparticle diffusion in the water‐soaked beans and external mass transfer. A mathematical model based on a linear‐driving‐force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO 2 describes the time‐dependent process. The partition coefficient for caffeine distributed between water and supercritical CO 2 , the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure.
Peker et al. (Fri,) studied this question.