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!
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!
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
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.
Here I found this article on the web hope it helps ref
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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
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.
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.
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
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For best type of decaffeinated green tea to drink, check out the article below:
Decaffeinated Green Tea
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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.
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
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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.
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.
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?
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.
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.
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.
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:
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