British Prime Minister William Gladstone (1809-1898) is often quoted for his endearing description of tea:

“If you are cold, tea will warm you; If you are too heated, it will cool you; If you are depressed, it will cheer you; If you are excited, it will calm you.” 

These welcome but antagonistic effects are provided by two physiologically active components of tea – caffeine and theanine. In this Newsletter we consider caffeine and decaffeination. Next time we will look at the effects of theanine. 

Caffeine – it can be no coincidence that the world’s most enduringly popular beverages tea, coffee, cocoa, maté (and Coca Cola) all contain caffeine or its closely related methylxanthine cousins. The bitter tasting physiologically active compound caffeine occurs at around 3-4% w/w in good quality African teas but at about two thirds of this level in China teas, both green and black. White teas, being made from the tender-most tips where caffeine is naturally concentrated are, despite many vendors’ claims, some of the highest caffeine containing teas available. Tea’s refreshing effects on body and mind have been recognised for millennia, though this was only traced to its caffeine component in the nineteenth century. Lung Tung accurately describes tea’s effect thus:

“The first bowl sleekly moistened throat and lips, The second banished all my loneliness The third expelled the dullness from my mind, Sharpening inspiration gained from all the books I’ve read The fourth brought forth light perspiration, Dispersing a lifetime’s troubles through my pores”

Lu Tung, Chinese Poet, On Drinking Tea (around 780 AD)

At normal levels of intake – compare with Lu Tung’s description – caffeine has positive affects on mood (happiness and contentedness), on mental clarity and on wakefulness. Its negative effects (particularly at higher intakes) can include anxiety, raised blood pressure, sweating, and trembling.

Caffeine contributes to the overall taste experience of tea, and has an incompletely understood interaction with the natural polyphenols causing ‘creaming down’ of infusions as they cool. This complexing and consequent slower release into the bloodstream may be the reason for the more gentle effects on the body of tea derived caffeine compared with coffee or cola derived caffeine.

Decaffeination. Some nervous and light- sleeping consumers prefer to drink their tea and coffee free from the physiologically active caffeine component. Tea has only relatively recently been commercially decaffeinated but methods for decaffeination of coffee have existed since the early 1900s utilising the selective solubility of organic solvents for caffeine while leaving behind the soluble solids required for colour and taste. Chloroform was once a favourite solvent and is a very effective extraction method – but its use is now banned. Four decaffeination methods are currently used by the tea industry:

Ethyl acetate – ethyl acetate occurs naturally (though at very low levels) in green leaf so it can be considered a natural method as any residue left is indistinguishable from that found in normal tea, though it will be present at a higher level. Ethyl acetate can be hazardous during processing as it is highly inflammable (flash point -4°C). As a caffeine solvent it is not as selective as other methods and removes some colour and flavour as well, thus drinking quality is compromised. However, it is still an accepted method for decaffeination throughout the world.

Methylene dichloride – an organic solvent that is very selective for caffeine but has production problems for factory personnel as, if not correctly controlled, it can cause faintness, headache, skin irritation and eventually unconsciousness. It has been associated with causing cancer in mice – but at levels equivalent to a human drinking 12-24 million cups of decaffeinated coffee a day! However, as methylene dichloride is also used as paint stripper, there is some consumer resistance to it. Used as a decaffeinating agent for black tea (in consuming countries) and better still on fermenting leaf during primary production (in Malawi and Zimbabwe) it can produce a very good quality decaffeinated product. Its use is banned in decaffeinating tea for import into USA, though perversely they allow it for coffee decaffeinating.

Supercritical carbon dioxide – under extreme high pressure – more than 500 atmospheres – CO2 gas acts as a liquid solvent and is quite selective for caffeine. There are no chemical residues and the process, using only CO2 and water is thus completely “natural”. It is accepted for decaffeination throughout the world. The drawback to the method is the huge capital investment and running cost of a high pressure plant.

Water method – decaffeination by water extraction followed by add back of dissolved solids has been successfully employed in coffee decaffeination (the Swiss Water Method) – where use of water is seen as the most natural method. Attempts (in India) to copy this method for tea has so far failed to produce even a medium quality product.

At More Tea we have yet to find a decaffeinated tea that matches our quality expectations – until we find one we shall continue to supply our Camellia teas as 100% naturally caffeinated – but for caffeine sensitive customers we have a wonderful range of herbal teas and tisanes all guaranteed to be entirely caffeine free – except Maté of course.

For example try Red Rooibos (TR01), Green Rooibos (TR02) or Honeybush (TH02).