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.

 

Sources:

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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Honeybush – The Other South African Tisane

Honeybush is closely related to rooibos which also grows in South Africa

Honeybush, also known as Cyclopia, of South Africa

Rooibos is not the only tisane which calls South Africa home. While rooibos has captured the most attention, and been subject to at least two attempts to trademark the name, honeybush is a very close cousin. Honeybush is used as a base for a wide variety of products and can be used in cooking. It is also caffeine free making it popular in the afternoon. Although similar to rooibos in many ways, it is has a bit sweeter taste providing an equally delicious infusion.

Honeybush Production

There are many similarities between honeybush and rooibos. Not only are they both from South Africa but they both come from the Fynbos region. Specifically they come from the Western Cape, South Africa, around the Cederburg Mountains. The product is chopped into fine pieces and normally fermented before packaging and shipment. As a variation, green honeybush is produced without the fermentation step. Like rooibos it also comes from the legume family, though this family is quite large and includes 16,000 others.

Though there are many similarities, there is a large difference in cultivation.  Most honeybush is harvested from 20+ species of wild cyclopia bushes. About 70% is harvested by hand in remote regions of South Africa with about 30% coming from commercially planted bushes.  Global demand from the Germany, the US, and other locations is increasing however, so this plant is increasingly planted and harvested from commercial plantations.

History of Honeybush

South African castle built by the Dutch East India Company

Dutch East India Company – Castle of Good Hope

Like rooibos this tisane has its roots dating back hundreds of years to consumption by native bushman or Khoisan people. According to the Institute for Traditional Medicine, honeybush infusions have likely been around for hundreds of years. The Dutch “discovered” it while exploring the plants and animals around a fort near what is now Cape Town when it was a stopover for trade between Asia and the Netherlands. The purchase of the Cape Colony by the British and subsequent adoption of English helped further spread knowledge of honeybush and probably rooibos as well.

Honeybush Future

Production of honeybush has been rapidly increasing to meet growing international demand for this tisane. Not only does it make a great base for caffeine free tisane infusions but there is also potential for health benefits as well.  According to the South African Honeybush Tea Association (SAHTA) which formed in 1999, there is a substantial amount of research occurring around potential health benefits from anti-oxidants and other compounds. Its consumption may help prevent cancer or offer alternatives to hormone replacement therapy.  Much still needs to be done to validate these ideas as well as meet existing commercial demand. To satisfy these needs SAHTA also actively works to improve cultivation, biodiversity, and sustainability practices to increase production and ensure continued availability.

Honeybush tea infusions are often consumed straight, although they may also be consumed with milk and sugar. Honeybush blends well with a wide variety of ingredients including ginger, lemon myrtle, lemon grass, fennel, and even caramel pieces. Be sure to have a look at the recipes provided by SAHTA on its website for honeybush tea punch, tarts, and muffins.

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