The most common approaches to decaffeinating coffee involve chemical solvents, typically ethyl acetate or methylene chloride. In the direct method, coffee beans are first steamed and then repeatedly rinsed with the solvent to extract the caffeine. In contrast, the indirect method keeps the chemical away from the beans themselves. Instead, the beans are soaked in water to draw out the caffeine, and the solvent is used to remove caffeine from this water. The flavor-rich water is then returned to the beans, allowing them to reabsorb many of their oils and taste compounds. In both approaches, any residual solvents are either rinsed or evaporated during processing, and further eliminated during roasting, leaving only trace amounts considered safe for consumption.
Another technique, the Swiss Water Process, relies entirely on water and carbon filtration. Beans are soaked in hot water to extract caffeine along with flavorful compounds. The first batch of beans is discarded, but the water, now rich in flavor and called “green coffee extract,” is filtered through carbon to remove only the caffeine molecules. This decaffeinated extract is then used to treat a new batch of beans, effectively removing caffeine without chemicals and preserving much of the original flavor. This method is widely used for organic coffee.
Finally, the supercritical carbon dioxide method utilizes CO2 under high pressure and temperature, allowing it to behave simultaneously as a gas and a liquid. After beans are soaked in water to expand their cell structures and facilitate caffeine extraction, they are exposed to supercritical CO2 for several hours. The CO2 absorbs the caffeine, which is then separated and removed. This technique preserves the beans’ carbohydrates and proteins, resulting in minimal flavor loss during decaffeination.
