Method for decaffeinating coffee with a supercritical fluid

A method of decaffeinating green coffee in an extraction system comprising:

• (a) Continuously feeding essentially caffeine-free supercritical carbon dioxide to the bottom portion of an extraction vessel containing moist green coffee beans for a period of time sufficient to transfer caffeine from the moist green coffee beans to the supercritical carbon dioxide, said transfer resulting in a caffeine concentration in the supercritical carbon dioxide which is at least 40% of the maximum obtainable caffeine concentration therein, said maximum obtainable caffeine concentration being defined by the caffeine partition coefficient for said supercritical carbon dixoide and;
• (b) withdrawing said supercritical carbon dioxide containing at least 40% of its maximum obtainable caffeine concentration from the top portion of the extraction vessel, said moistened green coffee beans in the extractor containing between 35% and 50% by weight moisture;
• (c) periodically discharging a portion of decaffeinated coffee beans from the bottom end of the extraction vessel and;
• (d) periodically charging a portion of moistened undecaffeinated green coffee beans to the top end of the extraction vessel;
• (e) contacting said caffeine laden supercritical carbon dioxide from step (b) countercurrently with an aqueous fluid in a substantially unobstructed absorber to transfer substantially all caffeine contained therein to the aqueous fluid with no appreciable transfer of non-caffeine solids to the aqueous fluid;
• (f) collecting the caffeine laden aqueous fluid and subjecting said caffeine laden fluid to reverse osmosis to recover a concentrated caffeine solution and an acidic aqueous permeate substantially free of caffeine and;
• (g) adding the acidic permeate to the extraction system to reduce the green bean extraction time and improve green been quality.