Tea (rec.drink.tea) Discussion relating to tea, the world's second most consumed beverage (after water), made by infusing or boiling the leaves of the tea plant (C. sinensis or close relatives) in water.

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Old 17-03-2007, 10:23 AM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Hello all,

Greetings from a tea-lover in the oolong capital of the world, Taiwan!
Great group! I have a strange tea question. I wonder if any of you
might have the answer . . .

I regularly decaffeinate my tea after 7pm by simply discarding the
original 30 seconds of steeped tea water and re-steeping in fresh
water for another minute, two, or three, depending on the tea. This is
quite common here in Taiwan, where for most Oolongs we "wash" the
leaves and remove a bit of the caffeine, and then have three or four
more steepings. Anyone who wishes to avoid excess caffeine simply
abstains from the first round. The flavor of the tea certainly suffers
in the 30-second decaffeinating process, but at the end of the day I
always trade flavor for a good night's rest. Oolong flavor generally
stands up much better to the decaffeinating process than black or
green varieties. Anyway, not to get off track . . .

Up to 75% of the caffeine is eliminated by removing the first 30
seconds of steeped tea water. But what about the L-Theanine? Could I
also be removing the L-theanine (i.e. the de-stressing component of
the tea) and much of the heathful properties of the tea? I drink a lot
of green tea, so I'm concerned I'm missing out on its goodness by
decaffeinating.

If anyone knows the answer or could point me to a source, I would much
appreciate it! Thanks!

--Mark


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Old 17-03-2007, 04:52 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

After my original post, I went back through the archives and
discovered the decaf thread . . . Well, I'd still like to know about L-
theanine . . . thanks!

--Mark

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Old 17-03-2007, 06:20 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Well as I understand , white tea, green teas due to the fact that the
enzmes are fixed preventing further oxidation seems to yield higher
levels of thenanine than that of fully fermented black teas, so as far
as the oolongs go the less they are fermented the more theanine you
will get out of them. Regarding the release I dont know however for
interests sake I understand that tannin is released after about five
minutes of steeping, this may be that in some teas the longer they
steep the more bitter they become.
...Maurice


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Old 17-03-2007, 09:25 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

"mgford25" writes:

After my original post, I went back through the archives and
discovered the decaf thread . . . Well, I'd still like to know about L-
theanine . . . thanks!


I don't have any numbers to give you. The best I can do is to not
that theanine is a pretty small molecule, not greatly different in
size from caffeine, and all other things being equal, you'd expect it
to exit the leaf at a similar. Of course, some other things may
be unequal, like the chemical properties of the two molecules! I bet
DogMa could take a far better educated guess than I.

/Lew
---
Lew Perin /
http://www.panix.com/~perin/babelcarp.html
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Old 17-03-2007, 10:45 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Here I found this article on the web hope it helps
ref http://www.austinchronicle.com/gyrob...d=oid%3A208400


Tea and coffee both contain caffeine, a stimulant, but tea also has
tannin and theanine, which are calming. The presence of these chemical
compounds together in tea allows you to control its effect. When
boiling water is poured onto the tea leaves, in the first two minutes
all the caffeine is drawn out. At this point tea is most stimulating.
During the next few minutes, tannin and theanine are gradually brought
out of the tea leaves. After about five minutes this will tend to
cancel out the effects of the caffeine and will make a more relaxing,
calming tea. If you want only the calming effects from tea, discard
the liquid from the first two minutes of steeping and use only the
liquid from subsequent steeping, containing little caffeine and more
tannin and theanine



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Old 18-03-2007, 10:34 AM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Hey guys

To add to the discussion above:

1. The reason green tea and white contain more theanine is because
they tend to be made from young tender shoots. Oolong tea is made from
more mature leaves, which gives them a richer fragrance, but less
theanine.

2. Caffeine is quicker to dissolve in water compared to catechins or
theanine, that is why the first infusion is much richer than caffeine
compared to the other more beneficial chemicals. To answer your
question, later infusion still has the theanine and catechins, but
much less caffeine.

3. Theanine dissolves faster than the other tea tannins. Theanine it
not only calming, it is fresh and sweet tasting. Latter infusion
tastes bitter because there is less theanine in them. So as long as
your tea tastes nice, don't worry, the theanine is there.

The link below contains a discussion on tea chemistry based on
Graham's paper in 1992.

Green Tea Chemical Composition
http://www.amazing-green-tea.com/che...green-tea.html

4. For best type of decaffeinated green tea to drink, check out the
article below:

Decaffeinated Green Tea
http://www.amazing-green-tea.com/caf...green-tea.html

Talking about caffeine and catechins, I had 2.5 grams of dragonwell
yesterday and it keep me wide awake all day! I infuse it four times
and it was still going strong! This stuff is REAL powerful.

Kind regards
Julian

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Old 19-03-2007, 05:23 AM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Tea Drinkers,
Thank you everyone for helping me! A very, very cordial group you have
here! I look forward to following the other discussions...

--Mark

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Old 12-04-2007, 11:47 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Lewis Perin wrote:
I don't have any numbers to give you. The best I can do is to not
that theanine is a pretty small molecule, not greatly different in
size from caffeine, and all other things being equal, you'd expect it
to exit the leaf at a similar. Of course, some other things may be
unequal, like the chemical properties of the two molecules! I bet
DogMa could take a far better educated guess than I.


Julian wrote:
2. Caffeine is quicker to dissolve in water compared to catechins or
theanine, that is why the first infusion is much richer than caffeine
compared to the other more beneficial chemicals.


I had a quick look in at-hand reference books, but couldn't find good
water-solubility data on both molecules. Perhaps someone with
library access would like to look.

Size matters, but it's not just the molecule itself. Effective
hydrodynamic radius for diffusion depends on the size of the hydration
sphere, which in turn depends on things like dipole moments in various
parts of the molecule, and how it wraps itself up - not a factor for
caffeine, but perhaps important for theanine. If I had to guess, I'd say
that they're probably similar enough in extraction rate that
time-slicing won't allow a useful separation. Perhaps Julian would be
kind enough to provide a research source for his assertion.

Re the reference
http://www.austinchronicle.com/gyrob...d=oid%3A208400
language like "... in the first two minutes all the caffeine is drawn
out. ... During the next few minutes, tannin and theanine are gradually
brought out of the tea leaves" is misleading. Things aren't drawn out;
they fall down a concentration gradient, and not all at once. They tend
to follow a slow induction - quasi-steady state - asymptotic decline
profile influenced by leaf hydration, remaining concentration and even
the local concentration of other ingredients. A mental image of stepwise
effects is not correct. (For an egregious example, see the recent
Illycafe piece in Scientific American, which was so misleading and
self-promoting that I canceled my decades-old subscription.) Until
someone bothers to do real lab work like the caffeine paper cited by
Nigel (unfortunately under conditions not perfectly relevant for most of
us here) on both molecules at once, it's all idle speculation.

-DM
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Old 14-04-2007, 12:00 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

Dear Dogma

You got me there. It is good to hear what a chemist has to say.

I think my assertion comes from two parts: caffeine dissolves in water
faster than catechins, and compared to the theanine, caffeine
solubility in water is more sensitive to temperature - i.e. caffeine
dissolves much faster in hot water.
Sadly, I have a quick scan through my materials and it is not
immediately obvious there is a good relevant study that compares water
solubility of caffeine and theanine.

Another factor is caffeine and theanine reactivity with other
compounds in hot water. There are suggestions that caffeine forms
compounds with tannins and theaflavin. It will be interesting to know
how much of caffeine reacts away and how that compare to theanine -
and in fact how the two interact.

What was interesting during my quick scan is that young leaf (tea
flush) contains more theanine and catechins than older leaves. With
the ratio of theanine (and probably caffeine) to catechins much higher
in younger leaves than older leaves.

Julian
http://www.amazing-green-tea.com

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Old 14-04-2007, 01:00 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

juliantai wrote:
I think my assertion comes from two parts: caffeine dissolves in water
faster than catechins, and compared to the theanine, caffeine
solubility in water is more sensitive to temperature - i.e. caffeine
dissolves much faster in hot water.


Unfortunately, it's even more complicated than that. Most references
will report equilibrium solubility, which for all materials in question
is far more than the amount of solute available. You're mainly talking
about dissolution kinetics. There again, the model is too simple. A pile
of caffeine powder dissolves in a little hot water with a few swirls.
But the actives in tea are buried in small leaf cells, behind various
membranes and tortuous passageways, all of which change in permeability
(in both directions) as the leaf hydrates; they may also be bound more
or less strongly by electrostatic and hydrophobic interactions, etc.
There's just no substitute for experiment. Too bad no-one with an HPLC
(a very common research tool) has bothered to do the definitive work -
or to report it. Who knows if Lipton and others have done all this work,
and found the results either useful in their business, or deleterious to
same, hence proprietary?

Another factor is caffeine and theanine reactivity with other
compounds in hot water. There are suggestions that caffeine forms
compounds with tannins and theaflavin. It will be interesting to know
how much of caffeine reacts away and how that compare to theanine -
and in fact how the two interact.


I don't think that that would affect physiological effects. Those are
weak associations - not "real" covalent chemistry - and probably pop
right apart in the stomach.

What was interesting during my quick scan is that young leaf (tea
flush) contains more theanine and catechins than older leaves. With
the ratio of theanine (and probably caffeine) to catechins much higher
in younger leaves than older leaves.



It is all interesting. From my perspective, Anyone who's not living
fully organic/macrobiotic, exercising regularly and otherwise living a
healthful life should forget all those alleged tea health benefits and
focus on known, powerful influences. Caffeine certainly has real
sensible effects, and theanine might, but most of the chemical
discussion here seems to me more like self-hypnosis than meaningful
control of self-medication.

-DM


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Old 16-04-2007, 03:22 PM posted to rec.food.drink.tea
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Default Japanese Green Tea and L-theanine

In article ,
DogMa wrote:
Lewis Perin wrote:
I don't have any numbers to give you. The best I can do is to not
that theanine is a pretty small molecule, not greatly different in
size from caffeine, and all other things being equal, you'd expect it
to exit the leaf at a similar. Of course, some other things may be
unequal, like the chemical properties of the two molecules! I bet
DogMa could take a far better educated guess than I.


Julian wrote:
2. Caffeine is quicker to dissolve in water compared to catechins or
theanine, that is why the first infusion is much richer than caffeine
compared to the other more beneficial chemicals.


I had a quick look in at-hand reference books, but couldn't find good
water-solubility data on both molecules. Perhaps someone with
library access would like to look.


Catechin is pretty soluble... it just disappears when it hits the
surface. It's still used as a photographic developer and it's one of
the fastest to mix up (unlike developing agents which need to be dissolved
in an alcohol and then added to the water in order to speed the process up).

But, I happen to have a Merck Index in my office and it says that
"Aqueous solutions of caffeine salts disassociate quickly" and that
solubility is one gram to 46 ml water. It also notes that "solubility
in water is increased by alkali benzoates, cinnamates, citrates or
salicylates."

As opposed to catechin which it says is "slightly soluble in cold water,
soluble in hot water."

Tannic acid, by the way, takes 0.35 ml water to dissolve a gram. So it
can be concentrated a lot more than the caffeine though of course this
says nothing about the rate of dissolving.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Old 27-04-2007, 08:25 PM
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Default

Quote:

Too bad no-one with an HPLC (a very common research tool) has bothered to do the definitive work - or to report it. Who knows if Lipton and others have done all this work, and found the results either useful in their business, or deleterious to same, hence proprietary?

Having worked previously in a laboratory setting, and being on good terms with the lab, I would have access to an HPLC machine. The downfall to running an experiment like this would be the hours it would take, and thus the cost of running these tests, only to determine what I believe to be true: there are too many variances between teas, growing seasons, ect. for this information to be of much use. It is important to keep in mind also, that each individual will have different reactions to the combination of caffeine and L-theanine. An avid tea drinking habit has led me to the conclusion that the combination of these two chemicals has quite a different physiological effect than each on their own (ie the difference between the effect of comsuming an espresso vs. tea). The effects of the combination of these chemicals affects me differently on a day to day basis, and probably has something to do with my hydration levels, and interaction with chemicals already in my body.

I think a more useful study would be to measure the physiological effects of these two chemicals on the human body, rather than the amount that is extracted with brewing. When it comes down to it we want to know the amount of each in the brew, because we want to know what it will do to us! Or because we want to control the effects, as mentioned above, trying to eliminate caffeine, but not theanine. Why not just enjoy it as it is? If you want to drink something that won't keep you up all night, there are many herbal teas that are naturally caffeine free. Or wait until the next day, when you can drink the first infusion early in the day. I guess it is human to try to control nature, when it is really nature that controls us!

The hours and cost of a physiological effects study will be astronomical, I am sure. Too much for pursuit by any tea or beverage company, even with the tout of Lipton. By the way, commercial tea in tea bags definitely do not seem to have the same effect as fresh, loose tea, indicating to me a much lower content of active caffeine and theanine. The only feasible way to go about this, would be to get a research company interested in the topic. Any takers?

On a separate note: it is possible to give yourself an overdose of caffeine. It's not fun!!! I have done this once and caution anybody to use care when consuming anything that contains this chemical. Some people seem immune to the effects of caffeine while others, like me, are ultra-sensitive. Also, studies done recently are showing certain pharmaceuticals cause the body to decrease ability to eliminate caffeine. This causes caffeine to "build-up" in the body, and produce a very scary overdose effect. Some of these are in birth control, taken by millions of women. Please see this website, for possible drug interactions with green tea/caffeine:

Possible Interactions with: Green Tea
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Old 10-06-2007, 01:26 PM posted to rec.food.drink.tea
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Default Time and temperature in re-roasting

Long post - if you respond please trim most of it.

This topic comes up from time to time. I've only had one old oolong
that had been re-cooked annually. Rich color, interesting taste, very
little aroma. Good, but not nearly as appealing to me as a high-ferment,
relatively high-roast Anxi oolong. I might have liked it better had each
treatment been a bit lighter. Most descriptions I've heard of this
process indicate that it's about aging, with the re-roast necessary to
prevent staling. I suspect, though, that it would better be seen as
multiple re-roastings with "hold" periods in between. Might be an
analogy with the seasonal rotation alleged to help mature great old Puerh.

I've re-roasted a number of oolongs (and, less often, sheng Puerh and
other teas) when they grew stale or just started boring. Works for
bread, after all. These most notably include some very expensive
"special" dan cong and other oolongs from a famous West Coast dealer,
all of which were disappointingly pallid and distinctly stale on arrival.

I've re-roasted these and others in a few ways, including:

- microwaving, in an open dish with or w/o a cup of water to protect the
magnetron;

- stirring in a small frying pan over a moderately hot electric stove
(wok over flame would be better, but no gas here);

- in the tray of a toaster-oven; and

- in an ash shovel right in the flames of a wood stove.

The first one has had a mild but noticeable and distinctly positive
effect, perhaps surprising given the limited peak temperature. (Once the
water's all gone, energy absorption drops right off.)

Frying pan and toaster-oven were about the same in just a few tries;
stove-top frying gives much better access for turning and frequent
visual/smell inspection.

Limited experiments with right-over-the-fire gave the best results,
possibly because of the slight wood-smoke addition.

Some people use specialized vessels, heat sources, techniques, etc. From
the chemistry perspective, method follows the desired effect. (-Though
the history of science is punctuated by discoveries based on available
equipment and techniques, rather than any special intention.) So I'd
like to float the question: what parameters seems to work best for
restoring old/stale teas, perhaps of different kinds; and for creating
substantially new flavor profiles?

To a chemist, this is an interesting question. Allow me to introduce the
notion of reciprocity: if some temperature for some time produces some
effect, what greater temperature for what lesser time (or vice versa)
will produce the same effect? Or can it even do so? Serious
photographers know about photochemical reciprocity failure in films. And
serious tea-drinkers know that while steeping time and temperature can
be traded off to achieve a given nominal brew strength from a given pot
of leaf, the resulting complex flavor profile will change dramatically.
(Think overnight refrigerator brewing vs. gong-fu.)

Superficially, heat has four kinds of effects: it helps to split stuff,
join stuff, change stuff, and drive stuff off.

Fragmentation usually accelerates very rapidly with temperature due to a
high positive entropy of activation (for those who care and didn't know).

Joining small bits into bigger bits often has a negative entropy of
activation, and does not accelerate as much with temperature. (Chemical
change rarely slows down overall with heat; something else happens
instead.) Relevant example: the Maillard reactions, responsible for so
much of cooking's best effects, happen when amino acids and sugars react
on heating. Or autoxidation, where atmospheric oxygen reacts (most
typically) with olefins, producing species that are already funky and
rapidly decompose into things with very different flavor/odor. This is
probably a key staling cause - and sometimes a chain reaction that can
run away, as when oily rags self-combust.

"Change" covers a multitude of effects, from cis-trans isomerization
(hence "trans fats") and other thermal rearrangements to internal
condensations and many, many more.

What gets driven off, beyond water, is anything of low-to-moderate
molecular weight, including many taste and almost all aroma components.
I'm guessing that the only reason multiply roasted oolongs have any
smell at all beyond char is that some desirable elements are generated
freshly in each cycle.

That was either more or less than you needed to know. My over-arching
point is that the chemical kinetics of something with as many
simultaneous and interlinked processes occurring simultaneously as
tea roasting is not only immensely complex, but almost by definition
non-linear, hence difficult to analyze. Why experience usually beats
theory... At the same time, I'd like to offer a close and a remote
analogy. Fine coffee is roasted at temperatures above the autoignition
point, with split-minute timing and consequences of error ranging from
unpalatability to conflagration. Since the process is so fast, there
would be (at least on the boutique scale) little consequence to dropping
the oven setting a few degrees and adding a few relaxing minutes to the
cycle. But reciprocity fails, and (unlike with roast beef and chili)
long, slow cooking doesn't work very well.

Further in the same direction is the chemical technique of flash
pyrolysis. One can run fragile little molecules through a quartz tube
under inert atmosphere or vacuum at at 2000 degrees F, cracking or
rearranging them into reasonable yields of even more fragile molecules.
It works because contact times are about a millisecond, and the effluent
is collected fresh on a cold finger full of liquid nitrogen. There are
even faster transient-heating techniques.

Slow-roast is easy. Faster methods, like wok-frying, are in common
use in the tea industry and reputed to be done by seasoned experts. I'm
wondering how far the fast-heat approach has been pushed, and what
beneficial results might be found. I plan to test a few more variables,
though perhaps not until autumn. Anyone else care to report experience
in this area?

-DM


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