Tea Geek: Understanding CO2 Decaffeination

Caffeine Chemical Makeup - Decaffeination Doesn't Remove It All!

Chemical Makeup of Caffeine

Is decaffeinated tea something you drink regularly? Ever wonder how tea is decaffeinated? The process for decaffeinating tea is much like washing dishes in a sink, though with a few extra steps so you actually end up with clean dishes (tea) rather than dishes that have sat in swirling, dirty water (albeit with a bit of soap for good measure).

As you may know, there are several methods by which tea (and coffee for that matter) are decaffeinated. While coffee has the “swiss water method” in addition, tea is predominantly decaffeinated using one of two methods, the ethyl acetate or the CO2 method. While the ethyl acetate method is referred to as natural decaffeination, the chemical, an organic solvent technically, appears in many products including nail polish remover and cigarettes. Doesn’t exactly leave a great taste in your mouth to learn that, does it? This is one of the reasons why high quality tea companies like Dominion Tea, steer clear of “natural decaffeination”.

Given that we humans generally exhale carbon dioxide (CO2), its use in decaffeination is something that consumers find much more appealing than the alternatives. You may have heard the CO2 process referred to as a CO2 bath or as using supercritical CObut what is this really?

Tea Decaffeination with Supercritical CO2

Diagram of phases of CO2 - supercritical fluid is used in decaffeination.

Carbon Dioxide at various temperatures and pressures. (Public Domain)

In a nutshell supercritical CO2 is carbon dioxide held under very high pressure in a state where this gas actually becomes somewhat liquid (almost a thick fog). Remove the pressure and the liquid turns into a gas and evaporates. Nice, clean and simple. However, you wouldn’t to wash dishes in a sink and simply pull the plug, leaving the detergent and all the leftover food and grease to sit and dry back onto the dishes would you? So clearly this process has a couple extra steps…

The process for decaffeinating tea with supercritical COrequires some mechanism to separate the caffeine from the tea so it doesn’t remain after the CO2 is removed. There are several methods for doing this, all starting with tea in a closed container of CO2 at 3,700 to 5,000 pounds of pressure per square inch! After “bathing” the tea in supercritical CO2, various mechanisms are used to move the caffeine away from the tea before pressure is removed and the leftover COevaporates.

Incidentally, the leftover caffeine isn’t pitched. Instead, its sold to other companies which use it in soda, sports products, and even some foods.

Challenges with Supercritical CO2 Decaffeination

There are several challenges with this process of producing decaf tea, some technical, and some with the resulting product. The removal of caffeine tends also to remove other flavor compounds since carbon dioxide can’t perfectly target only caffeine. So the various methods seek to try to limit removal of other “good” compounds or add them back. Each of these processes add time and cost to the end product. Some are more energy, time, and labor intensive than others. However, all methods result in a cost per pound of decaf tea that is significantly higher than that of fully caffeinated tea.

Technical challenges aside, from a consumer perspective the decaf tea costs more to purchase, may have a flat or at least less flavor, and still has a low level of caffeine in it. Since it still has caffeine, even drinking decaf tea in the afternoon or evenings can leave some with jitters or trouble falling asleep.

Since the labor and cost of decaf tea is high, and comes with less flavor, companies typically only decaffeinate a select number of teas. In the case of Dominion Tea, this is why you won’t find a lot of decaffeinated tea options. We do have a couple (Earl Grey Decaf and Summer Peach Decaf), however we prefer to focus on great tasting fully caffeine free options with a rooibos or honeybush base or select herbal teas.



US Patent US4976979 A – Process for the decaffeination of tea, by Hubertus Klima, Erwin Schutz, Heinz-Rudiger Vollbrecht, https://google.com/patents/US4976979

US Patent US5288511 A – Supercritical carbon dioxide decaffeination of acidified coffee, by Peter T. Kazlas, Richard D. Novak, Raymond J. Robey, https://google.com/patents/US5288511

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