Sorry to come in late on this topic, which is of considerable interest
to me both as an example of the gratuitous pseudo-scientific mysticism
that displaces so much that is truly useful in tea lore and tea
thinking, and of the way that advertisers casually sling BS that doesn't
help and often harms tea-drinkers.

Nigel wrote:
> This is wishful thinking and an oft repeated tea myth that could well
> do with laying.

Thanks for your post, Nigel.

> ... a peer reviewed scientific paper recording precise time related
> extraction of caffeine from tea using a modern detection technique
> (HPLC).

The only way to fly. Too bad they didn't take a few more low-time data
points, but it's enough to make the lesson clear, as you indicate.

> ... 5 minutes (69%), 10 minutes (92%) and 15 minutes (100%).

When plotted with the origin, these make a pretty typical-looking
extraction curve. I would draw an even stronger conclusion than Nigel
from the low-time interpolated data. Since the authors used powdered
tea, extraction kinetics only model part of what happens in normal use.
In particular, for the first several seconds of steeping, leaves are
imbibing water rapidly, and very little material is leaving the leaf. So
a real-life extraction curve is sigmoidal (S-shaped), with almost
nothing happening for a period of time that might approach 15 seconds
for some unbroken leaves.

> This is 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!

I'm just a chemist; Nigel's the tea-science guru here and I defer to
him. I suspect that we agree, though, that rinsing to remove caffeine
will only work at all on CTC-type fragments where much of that component
is in fast-dissolving dried juices outside the cellular structure. In
this case, desirable flavor and alleged healthful effects will depart as
fast as caffeine. With whole-leaf teas, the notion that caffeine can be
removed selectively makes little theoretical sense, and the present
result supports that.

Many years ago, I had the un-original idea of using ice-water to
extract caffeine while leaving everything else intact. It doesn't work,
since many important flavor components are about as soluble in cold
water as is caffeine. Amino acids and sugars are examples. What doesn't
come out so fast is astringent tannins, which is why some of us prefer
cooler brewing styles. I think it fair to say that there is at present
no practical way for the average home user to decaffeinate high-quality
tea. It certainly could be done, by all sorts of affinity sorption
techniques, perhaps embodied on a stick or straw. But I doubt that
anyone will spend the development money to achieve this unless a lot of
tea-drinkers present a collective marketing case to the biochemical and
foods companies that command this technology.

-DM