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Alex Chaihorsky
 
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"Mike Petro" > wrote in message
...
>
>>Common, Mike - 1.7 vs. 3.4% is statistically not a difference - although
>>it
>>appear to be "twice", but it is only with a 1.7 total percent!.

>
> 50% more is indeed a difference in my book. Twice as much of a little
> bit is still twice as much, just ask anyone who is susceptible to
> caffeine jitters.


Sorry, Mike, mathematics does not work this way. The 'twice" thing only
makes sense if the you first established that your standard variation is
significantly smaller. That can only be done on a number of measurements. If
they would have said that they measured several green puerhs of different
types and the caffeine content cluster around a certain number (plus/minus
standard deviation) and that cluster is significantly smaller or larger than
the cluster of black puerhs, then the numbers will make sense. Otherwise
they are senseless.

>
>
>>2. The extraction from green teas is slower and the obly way to really
>>measure teh caffeine content is to do multiple steeps until there is no
>>caffeine left in teas and calculate the sum.

>
> I agree that since the extraction method is not listed here, beyond
> the fact they used powdered leaf, that there is room for question. My
> assumption is that anyone with access to this type of equipment would
> know how to do a proper sampling, but that is only an assumption.
>
>


Mike, you know how I respect you, but thi sis very naive of you. You can
have access to LH at about $50/hour here in teh US or send the sample to the
lab from here to India for about $10/sample. The way they described their
experiment without multiple measurments, standard deviations and margins of
error (even political pollsters do that!) are self-evident.

>
>>3. Caffeine is highly soluble, you are absolutely right. But you also have
>>to take into consideration that to enter solution it has first be
>>extracted
>>from the dead cells of the tealeaf, and that takes time. And mechanical
>>properties of the tea play critical role in that delay. I very much doubt
>>that any significant portion of caffeine is extracted during short washing
>>period, because the leaves must first be saturated with water to expand
>>and
>>this take time. I actually think that with puerhs and green teas the
>>second
>>and the third steeps (especially the second) is the most caffeinated.

>
> Possibly, I would love to see a proper study on it though. I cant help
> but feel that hot water will dissolve a significant portion of the
> caffeine immediately, but yes the second steep may indeed still
> contain a considerable amount. However if you do 2 rinses, as is
> popular with black puer, then where do we stand?


OK, let me put it this way - for a "wash" to work, the water has to
penetrate the insides of the dried cells of the leaf. The best indicator of
that is that the bulk of the leaf is not floating on the sirface anymore. So
put your puerh in hot water and measure the time when the bulk of the leaf
will settle on the bottom. This is the shortest possible time for caffeine
to be dissolved. But it also has to get out into the external part of the
solution. If you help it by say, centrifuge, I am quite sure that you will
get rid of 90% of caffeine. However as you know for non-boken or large leaf
tea to settle on teh bottom takes a LONG time. No 30-40 sek or even 1-3 min
wash would even come close.
Sorry, pal.

I would recommend a different experimental approach for the goal of decafing
a tea (based on extraction kinetics) - put it in ice-cold water until the
tea leaves sink (caffeine has a very high solubility - much higher than
other tea components) and ice-cold (or just cold) water will extract it with
no problem. Then, drain and brew (taking into consideration that it is
soaked in cold water, so you may need hotter water or even pre-heat the
soaked tea)

>
> It is an old trick with black (aka red) tea that if you want to
> decaffeinate it substantially all you need to do is steep it for 30
> seconds and throw away the first infusion. The "washing tea" may not
> be long enough to saturate the leaf totally but it is bound to have an
> effect.


Exactly. See the above explanation and technique based on the "floating
time"

Sasha
>
> Mike Petro
> http://www.pu-erh.net
> remove the "filter" in my email address to reply