Most people are unable to tell the difference between decaf and espresso coffee in a blind taste test. This is particularly true if the coffee is brewed correctly.
There are a couple of methods for extracting the caffeine in coffee. One way is to rinse the coffee with hot water and then to rinse again with methylene chloride. It is a colorless and volatile liquid with a moderately sweet aroma that is widely used as a solvent. Perhaps not the best solution for decaffeinating coffee.
You might not be aware that coffee is already been processed with water on several occasions before it ends up in your cup. In fact, the coffee berry has been rinsed to remove the outer fruit covering when it is first picked. The water actually softens the fruit on the outer layer of the berry.
The green beans are then warmed with either hot water or steam. This opens the pores of the beans which starts the chemical removal of the caffeine in the bean. The beans are then washed again but this time with methylene chloride. It binds with the caffeine and then it is flushed away.
The beans are soaked for several hours in hot water that percolates caffeine into a bath. The addition of methylene chloride is followed after the removal of the beans from the hot water. This chemical bonds with the caffeine in the bean without flushing the flavor components and then they are re-soaked, where re-absorption of the flavor components is accomplished.
Another method for removing caffeine is called the Swiss Method. This is where the beans are soaked in hat water without using the chemical, methylene chloride. The caffeine in this case is removed through the use of activated charcoal which filters the water.
Activated charcoal is relatively pure carbon and is actually the transformed molecular structure of activated charcoal that provides a sizable surface area allowing other molecules to stick to the charcoal.
Unfortunately most manufactures prefer the first method as it is less expensive. However, there is a lot of debate around this issue since some people belief the method actually degrades the taste of the coffee beans.
It has been found that the dark and less acidic roasts actually contain less caffeine as a result of the roasting process.
For the issue regarding taste, the chemical differences are by and large inundated by individual preferences. It seems that a lot of people can easily detect the absence or presence of caffeine as a result of its intrinsically bitter taste. It is only a matter of taste as to whether or not caffeine makes coffee taste good or bad.