Caffeine vs. Decaf
Caffeine itself has a slightly bitter flavour. Our perception of strength mostly comes from the degree of roast (the darker, the stronger) and the ratio of coffee to water used during the brewing process. This ratio is what creates the actual strength of the coffee.
Caffeine content varies between species of coffee trees. Arabica coffee beans contain about 1.5% caffeine by weight in their green form, while Robusta beans contain about 2% caffeine by weight.
The roasting process alters the amount of caffeine in coffee very little. Caffeine is readily water-soluble at temperatures above 170° F, so it is quickly released into the finished beverage during brewing.
The Decaffeination Process
There are two main methods of decaffeination, water processed and solvent processed. In order to make the caffeine easier to remove, all decaffeination methods start by increasing the moisture content of the green beans.
By way of osmosis, caffeine is stripped from the green beans by soaking them in hot water and a caffeine-free green coffee extract. The process may be repeated several times without affecting the flavour or other compounds in the beans.
Solvents used for decaffeination include ethyl acetate, methylene chloride and carbon dioxide. Generally, beans come directly in contact with decaffeinating agents after being softened by steam. The solvent combines with the caffeine and the beans are steamed again to remove the solvent mixture.
All decaffeination methods must remove 97-99% of the caffeine present in order for the coffee to be sold as decaffeinated. Depending on which of the above methods are used and how they’re used, the loss of flavour and aroma in the brewed beverage will vary.