"Lewis Perin" > wrote:
> Thanks! That was instructive and interesting, but I should've made
> clear what I was hoping for: for a given tea, some kind of formula for
> caffeine extraction in 2 independent variables (temp and time.) The
> particularity of the individual type of tea would be represented, I
> suppose, by some constant (factors?)

Right with you, bro. I've just never seen a comprehensive chart, table or
algorithm of the type you describe. Would be nice to have, for sure. It may
be that the leaf-processing and other variables I mentioned, or yet others,
make generalization impossible.

An earlier post to this NG or Teamail mentioned a "bell curve" for
extraction of various substances. Actually, it's much more complicated than
that. Whatever leaf is used, dissolution of surface exudates will be almost
instantaneous; hence the rapid coloring from EBT. For leaf contents, inward
diffusion of water and outward of solubles are highly non-linear, described
by complex partial differential equations, because degree of hydration
influences rate of further hydration. Then, over time, materials of lower
solubility and those buried deeper in plant tissue will elute at an
exponentially declining rate. So for any given material of interest, there
may be a surge in solution rate, a dip, a slower rise, and a gradual
fall-off. Every infusion will differ not only in total strength, but also in
balance. There's plenty of published work on efficient extraction of
valuable chemicals from plant matter, but that's usually a question of how
close they can get to total extraction, how quickly and how cheaply.

Sorry there's no simple answer, AFAIK. One almost-fact is that since the
alkaloids are relatively soluble in even warmish water, most of the
accessible theophylline and caffeine are probably out in a few seconds. I've
fooled around with completely hydrating leaves in cold water before that
first steep, and it seems to remove most of the caffeine (based on the
observation that I don't get my usual tea jitters) with nil loss of flavor
or color.

> Hmm, are you hoping for even more confusion as to the meaning of
> "white tea" than there already is out there?!

Absolutely. After all, as one of my profs used to say at every possible
occasion, erudition is not incontrovertibly predicated on obfuscation by
nugatory sesquipedalianism.

> Gyokuro is shaded for at least part of its life; I don't suppose that
> qualifies, does it?

Might well. My impression is that shade treatment of gyokuro is as much
about lightening the colour as anything. But I'm a philistine with limited
taste discrimination, so wouldn't know. I've never had a completely
etiolated tea, e.g. where branches were put in black plastic as soon as
leaves emerged. Seen this done for visual effect on greenhouse plants, and
it might make a very different taste. Who knows a plantation owner who'll
give it a try?

-DM