A reader wrote to Ask Yahoo! wondering How is coffee decaffeinated? The answer is very interesting.
Ask Yahoo: For most coffee beans, it begins with a nice, long soak. This submersion draws the caffeine from its beans, leaving us with a bushel of decaffeinated java seeds ready to be roasted, brewed, and slurped down.
But hold that cup of joe. This tastes like sludge!
The caffeine isn’t the only thing lured from the beans during their decaffeinating bath. The coffee’s flavor also seizes that moment to beat a hasty escape. So brewers need to coax the coffee’s good taste back. We’ll lay out the three primary methods of maintaining taste while separating a bean from its caffeine…
In one practice, the beans’ post-soak water is mixed with a solvent that separates the caffeine from the liquid. Alternatively, the caffeinated water can be forced through activated charcoal or carbon filters, which also separates the caffeine from the solution. After either method, the coffee beans are re-submerged in the now-totally-caffeine-free watery extract where (hopefully) they reabsorb their flavor.
Another method that immerses the beans in one heck of a strong steam bath, and then dunks them in carbon dioxide. The CO2 scares the caffeine away, but keeps the beans’ taste intact.
So, how successful are these processes? To be called “decaffeinated,” caffeine levels must remain below 2.5 percent.