"Nigel" > wrote in message
...
> On Dec 8, 5:43 pm, "Bluesea" > wrote:
>
> > So, now I'm in the position of wondering if the myth about DIY
> > decaffeinating is a myth since apparently anybody can put up a webpage
with
> > the scientific basis for whatever's being touted.
> >
>
> 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
> of
> the tea will actually leave in place 91% of the original caffeine!

It's "up to 80%" and extrapolation doesn't work if caffeine is so highly
water-soluble that the rate of release decreases dramatically after 30
seconds. We need the actual measurements at the precise points of time.

> 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 34%
> 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.

Caffeine is water-soluble above 175 deg F. Since Spiro's using 80 deg C is
right at 176 degrees, I question if a higher temperature, such as the
boiling water recommended for the 30-second DIY decaffeinating steep,
releases more caffeine than was released at 176 F.

See, it would be easier to accept your Hicks and Spiro defenses if their
experiments were conducted using actual measurements at the time and
temperature points pertinent to the "myth" because the rate of release at
the different temperatures preclude the use of your extrapolations.


--
~~Bluesea~~
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