Caffeine in Tea and the (false)myth of removing caffeine in a 30 seconds infusion (S: decaffeinate tea)

December 10, 2007 at 10:19 am | Posted in Black Tea, Tea and Health | 2 Comments

Following is a post by Nigel Melican, founder and Managing Director of Teacraft Ltd.
Post originally at rec.food.drink.tea, later expanded into an article on Cha Dao,

with his permission reproduced here:

As an antidote to the wishful thinking about the decaffeinating
effectiveness of a 30 second wash I proposed the data presented in
“Tea preparation and its influence on methylxanthine concentration” by
Monique Hicks, Peggy Hsieh and Leonard Bell which was published in
1996 in Food Research International. Vol 29, Nos 3-4, pp. 325-330.
Hicks et al measured the caffeine and theobromine (total
methylxanthine) content of six different teas (three bagged and three
loose leaf, including black, oolong and green types). They measured
caffeine extraction in boiling water at 5 minutes (69%), 10 minutes
(92%) and 15 minutes (100%). They replicated all their extractions
three times to eliminate error.
I extrapolated their data below 5 minutes which gave the following
caffeine extraction percentages (averaged over all their tea types and
formats; note while loose tea extracted marginally more slowly than
teabag tea it made only a couple of % points difference):

30 seconds……….9%
1 minute………….18%
2 minutes…………34%
3 minutes…………48%
4 minutes…………60%
5 minutes…………69%
10 minutes……….92%
15 minutes……….100%

This was very much at odds with the mythical “30 or 45 second hot
wash to remove 80% of the caffeine ” advice – as a 30 second initial wash
ofthe tea will actually leave in place 91% of the original caffeine!
Subsequent to that posting I rediscovered a paper by Professor Michael
Spiro whose group did some ground breaking physical chemistry on tea.
In “Tea and the rate of its infusion” Chemistry in New Zealand, 1981,
pp172-174, they disclose caffeine concentration diffusing into water
(4g loose leaf – it will have been CTC small fannings type – in 200 ml
water held at constant 80 deg C, and stirred with a magnetic
stirrer). First data point is at 90 seconds and shows 49% caffeine
removed from leaf (i.e. into water). Extrapolating from Spiro’s plot
gives:

30 seconds……….20%
1 minute………….33%
2 minutes…………64%
3 minutes…………76%
4 minutes…………85%
5 minutes…………88%
10 minutes……….99%
15 minutes……….100%

Thus while a 30 second “wash” under Spiro’s rather extreme laboratory
conditions (small leaf, loose in the “pot” rather than teabag, at
constant temperature and stirred vigorously) leached 20% caffeine
rather than just 9% under Hick’s more normal steeping, neither of
these findings anywhere near match the 80% decaffeination claims of
the wishful thinkers perpetuated as an Internet Myth.

Nigel at Teacraft

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

for the boys and girls without time to read and engulf the information (like me):

30 seconds does NOT REMOVE 80% of CAFFEINE in TEA.

good for me anyway i never followed that weird notion. i will continue with my
3 minutes, in fact i’ll continue to drink my teas following the test of tongue.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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2 Comments »

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  1. Damn, i was using the 3o second method for so long, and i was wodering why i suffered insomnia and irritablity

  2. One thing to keep in mind in the calculations is that noone brews their tea for 15 minutes, it would be undrinkable. For me, a more meaningful measure would be evaluating against the percentage that is typcially brewed in a cup of tea. For instance, I brew for 2.5 minutes, which by the two measures is either a ~40% extraction or a ~70% extraction. By this measure, prebrewing for 30 seconds followed by an additional 2.5 minutes of brew (3 minutes total) would be somewhere between a 19% and 26% reduction in caffeine versus my usual brew. Similarly, a 1 minute prebrew followed by 2.5 minutes of brew would be between a 33% and 41% caffeing reduction.

    Unfortunately, as the original data does not start until 90 seconds and 5 minutes, they don’t give us a really good measure of what is happening early on.

    In any case, a prebrew of 1 minute is a nice option if one wants to go half-caf.


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