Decaffeination is the process of removing caffeine from tea leaves. One would assume that decaffeinated tea would not contain any caffeine; however, the decaf label only means that caffeine has been taken out of the tea leaves, not that it is completely caffeine-free. In fact, there are still trace amounts remaining after the decaffeination process, about 2.5% or 2 mg of caffeine per cup.
We drink tea for its great health benefits. Are the beneficial compounds still found in decaf tea? Let’s take a look at how decaffeinated tea is made.
To keep the beneficial compounds in the leaf such as cellulose, proteins, etc intact while extracting caffeine is a great challenge, considering that tea contains about 800 chemical compounds that contribute to the taste and nutrition of tea. Since tea is water-soluble, water is used in all types of decaffeination processes, with the help of some decaffeinating agents to speed up the process while maintaining some degree of taste.
In the US, there are only two decaffeinating methods that the FDA recognizes: ethyl acetate and supercritical CO2. Both methods use a solvent to extract the caffeine. Ethyl acetate can effectively remove caffeine from the leaf, but it also extracts EGCG (a type of catechin, the primary beneficial component of polyphenols in tea) and other antioxidants. This process also leaves a chemical residue on the tea leaves. Another method, which is more expensive, is to use supercritical carbon dioxide that is pumped into a chamber containing tea leaves, which allows the highly pressurized liquid gas to circulate to remove the caffeine. From there, the "caffeinated" CO2 is separated from the tea, the caffeine is then removed from the CO2, and the CO2 is then recirculated with the tea and the whole process is repeated until the desired amount of caffeine is removed.
So, do the beneficial compounds remain after the decaf process? Studies suggest that the ethyl acetate method removes about 82% of the polyphenols, while supercritical carbon dioxide decaffeination removes only 8%. Another advantage of the CO2 method is that it does not leave a chemical residue on the leaves like ethyl acetate does. Although the reduced amounts of beneficial catechins and other antioxidants is not desirable, if you have to drink decaffeinated tea, find as much information as you can as to which decaffeinating process is used when selecting your tea. You may be able to discover a better-tasting decaf tea while still benefiting from a healthier cup.