There are three methods.
To extract caffeine, organic solvents, compressed carbon dioxide, or hot water are used. In the latter case, not only caffeine but also aromatic components are extracted from the beans into the solution.
The water is purified of caffeine, after which a new batch of beans is soaked in it. Since the water is already saturated with aromatic substances, it extracts only caffeine from the new batch of beans, without affecting other components.
