Caffeine in White, green, oolong, red, pu

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Brent D
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Wed Jan 29, 2020 4:05 pm

What are the caffeine levels of different types of teas?

Somewhere along the way, I got it in my head that the oxidation process made the caffeine levels in tea deteriorate. Perhaps I made this up? I googled it today, and found a lot of differing "studies".
Most stated that black (oxidized/ non-fermented) teas have more than green. The idea is that oxidation reduces leaf mass, but the caffeine level stays, so you are in effect concentrating the caffeine.
Now perhaps A green tea has more caffeine in the leaves, but being brewed at a lower temp makes the extraction level lower?
Where would puerh fall into this? Id imagine that time would deteriorate caffeine levels.
I have always felt that matcha is at the highest level, being that you are actually consuming the plant leaves.

This is all about discussion. The effects of caffeine on myself are negligible. I am not trying to compare to coffee, This about tea against tea and how processing effects levels.
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pedant
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Wed Jan 29, 2020 6:58 pm

my impression is that caffeine is not really degraded by processing, but you lose caffeine to sublimation during roasting.
is that really true? idk. someone, please hit the literature for us! :lol:
Brent D wrote:
Wed Jan 29, 2020 4:05 pm
The idea is that oxidation reduces leaf mass, but the caffeine level stays, so you are in effect concentrating the caffeine.
this idea is new to me. where does the mass go? you're not just talking about moisture loss or something, are you?
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Brent D
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Thu Jan 30, 2020 11:42 am

Ive never heard of it either. Im not exactly sure. Thats why I posted. Oxidation is by definition the atom or molecule losing electrons, so I suppose loss of mass does make sense, but there is a corresponding reduction, so mass should be conserved?
I wouldnt think that an oxidized tea has a lower internal moisture level than a roasted oolong.
Perhaps these studies classified a roasted oolong as a black tea though.
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Tillerman
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Thu Jan 30, 2020 9:51 pm

@Brent D & @debunix, Caffeine does not degrade in processing or in aging. You are correct Brent, in noting that in black tea the caffeine per weight of tea goes up because the mass of the processed leaf goes down. However, the large molecule polyphenols produced in black tea production bind to the caffeine making it unavailable for absorption into the the body. In general, the young buds and/or leaves used to make green tea contain far higher caffeine levels than the lower, older leaves used in the production of black and oolong tea and yes, the lower water temperature level used with green tea extracts less caffeine per cup (if you drink many cups of green tea, however, be prepared for a caffeine high!) Pu'er essentially is green tea and the levels of caffeine will depend upon the size, age and harvest date of the leaves. The only way really to know how much caffeine and given tea is delivering to the body is by lab analysis. There are no general rules that generally apply (except that with matcha you are ingesting the whole leaf so you are getting a good dose of caffeine.)
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Brent D
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Fri Jan 31, 2020 8:30 am

Thats some good info!
Makes sense as well. multiple cups of black/red tea have no effect on me, but if I get a little overzealous with a green or young sheng, I feel it.
So perhaps these tests were done on raw leaf rather than a finished brew.
Is this just knowledge you have amassed over time or do you have a source you can cite?
faj
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Fri Jan 31, 2020 10:29 am

Here is a link to results from a study that was made by the Camellia Sinensis teashop in collaboration with a lab.

https://camellia-sinensis.com/en/analysis-of-caffeine

Unfortunately, they do not specify if they infused all teas at the same temperature or not, and if they used the same dosage. However, they used 500ml as the water volume, so I suspect this is using 5g of leaf, as this is their typical recommendation for western-style infusion. Hopefully they used the right water temperature for each tea, as they state conditions were chosen to reproduce what the drinker would get at home.

It is obvious that green teas take most of the top spots, and not by a small margin. Exceptions are mostly roasted teas (hojicha) or those containing stems. There are weird exceptions, like a gyokuro way down the list. But generally speaking, green teas have much more caffeine than blacks or oolongs. The black tea that tested highest is a Darjeeling, which is not surprising. They tested only two white teas : one was middle-of-the-pack, and the other one was way down.
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Tillerman
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Fri Jan 31, 2020 11:13 am

faj wrote:
Fri Jan 31, 2020 10:29 am
There are weird exceptions, like a gyokuro way down the list.
@faj, actually to see gyokuro down the list is not a surprise. As you know, gyokuro is grown in shade for several weeks prior to harvest. Under these conditions, the plant produces less caffeine and more theanine. This is one of the reasons that good gyokuro can taste sweet and has a rich umami character.

@Brent D most of what I wrote is stuff I've picked up over the years. That said, there is a very good new book that briefly touches on the caffeine issue. Virginia Utermohlen Lovelace Tea: A Nerd's Eye View (don't be put off by the title; this is a serious, must read, study on the composition and flavor of tea.) The Ultracrepadarian is reviewing the book in a blog due out tomorrow.
faj
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Fri Jan 31, 2020 11:20 am

Tillerman wrote:
Fri Jan 31, 2020 11:13 am
faj, actually to see gyokuro down the list is not a surprise.
Well, then, the surprise is the gyokuro that sits at the very top of the list!
faj
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Fri Jan 31, 2020 11:33 am

Tillerman wrote:
Fri Jan 31, 2020 11:13 am
faj, actually to see gyokuro down the list is not a surprise.
The websites I am finding through a quick Internet search seem to state gyokuro has higher caffeine content due to the growth under shade.

It seems like both my sources and my data seem to be split on that subject! :D
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debunix
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Sat Feb 01, 2020 12:22 pm

But gyokuro is usually infused at cool temps, which would decrease caffeine extraction.

As I infuse it, however, I'm pretty sure I get a lot of the caffeine out of the leaf, because I do a series of infusions at increasing temps until I get to that last sweetwater infusion when the leaf is really done.
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leth
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Sat Feb 01, 2020 2:12 pm

I can't cite anything as I haven't really kept any of this info for references in any of my normal places it seems. But I seem to recall reading that it had less to do with processing and more to do with the various environmental differences for the plant itself, such as soil and location and what not. Also I have some memory of it being more related to which part of the plant you took, and that buds are higher in caffeine than bigger leaves further in. But as I said, I can't back any of this up. It isn't really that important to me. While I am a bit sensitive to caffeine and worry a bit about when and how much coffee I have if I ever taste one (I don regularly drink coffee but once in a blue moon I do it because the situation is right), I really don't ever think much about caffeine in tea, it is not a problem with "clean" teas.

And if anyone has good reference to anything about this. I'm interested as I found that I haven't really recorded any good once to use as citations if needed and thus would appreciate filling that gap in my technological index register of various scientific ramblings.
oeroe
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Sun Feb 02, 2020 1:41 am

Here's a one reference (barely) available online with citations.
I haven't really followed up on the research myself, but this has seemed like a good source.

http://uutos.sange.fi/wp-content/upload ... ffeine.pdf
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