This is a direct contact method of decaffeination. In this direct contact method, green beans are first softened by steam, to bring caffeine to the beans' surface. It penetrates the beans to extract the caffeine. The supercritical carbon dioxide is then drawn off, leaving the beans 97 percent free of caffeine. The solvent residue remaining on the beans dissipates as a gas when the beans return to room temperature.
Different coffees contain varying levels of caffeine, mainly depending on their botanical variety.
An arabica coffee, such as Colombian Supremo, has approximately half the caffeine content of a robusta coffee, such as a coffee from Cote d'lvoire. Depending on the type of bean, brewing method, and amount of coffee used, a five- ounce cup of non decaffeinated coffee will contain from 70 to 155 milligrams of caffeine. A coffee must have at least 97 percent of Its caffeine removed to qualify as decaffeinated in the United States. Each five-ounce cup of decaffeinated coffee, therefore, contains less than 5 milligrams of caffeine. Decaffeinated coffees tend to cost more than their non decaffeinated counterparts because of the additional labor, equipment and material expenses required for caffeine removal.