Coffee is decaffeinated primarily through several methods: chemical solvent- based processes, the Swiss Water Process, and supercritical carbon dioxide (CO2) extraction.
Chemical Solvent-Based Methods
In these processes, green coffee beans are first steamed to open their pores. Then they are repeatedly washed or rinsed with chemical solvents like dichloromethane or ethyl acetate which bind to caffeine molecules and remove them. Afterward, the beans are steamed again to remove any solvent residues. This method removes most of the caffeine while preserving much of the bean's flavor.
Swiss Water Process
This is a solvent-free method that uses only water and carbon filtration. Green coffee beans are soaked in hot water to extract caffeine and flavor compounds. The caffeine-rich water is filtered through activated charcoal to remove caffeine but retain flavor compounds, which results in green coffee extract. New batches of beans are then soaked in this extract, allowing only caffeine to move into the water and be filtered out. This method is chemical- free and preserves flavor well, commonly used for organic coffee.
Supercritical CO2 Method
In this method, green beans are steamed, then placed in a high-pressure chamber where supercritical CO2 (carbon dioxide under high pressure and temperature) acts like both a gas and liquid to penetrate beans and selectively dissolve caffeine. The caffeine-laden CO2 is then separated, leaving decaffeinated beans with minimal flavor loss. The CO2 is recycled to repeat the process.
Summary
- Beans are decaffeinated while green (before roasting).
- Typical caffeine removal is around 97-99.9% depending on method.
- Common solvents: dichloromethane and ethyl acetate.
- Swiss Water Process uses water and carbon filters only.
- CO2 method uses supercritical carbon dioxide to extract caffeine.
Thus, decaffeination involves careful extraction of caffeine by either solvent washing, water filtration, or advanced CO2 techniques while preserving the beans' flavor.
