Nigel writes:

On 11 Oct, 15:09, Lewis Perin wrote:
I just googled to try to see if
oxidation diminishes the level of theanine in tea, which could explain
what you perceive. I came up empty (not that this is conclusive!)

Oxidation - the pc term for fermentation in tea - does NOT affect the
theanine level. "Oxidation" as a process in tea is strictly the
enzyme catalysed oxidation of catechins to theaflavins mediated via
Polyphenol-oxidase or PPO. Theanine being an amino acid is unaffected
by PPO. Fermentation is however a whole lot more than just oxidation,
hence my preference for the former term, as it includes post oxidation
condensation and polymerization of theaflavins into many species of
thearubigins - none of which processes requires any oxygen - nor have
any affect on theanine level. There is potentially a slight reduction
in theanine level during firing (drying) due to Maillard reaction of
amino acids with sugars - but this should equally affect green teas.

I see your point about "oxidation". But the reason I habitually use
that word instead of "fermentation" is to reserve the latter for what
goes on in tea leaves when microbes get involved. That's become
important to me since I started to love Pu'er.

Thanks for introducing me to M. Maillard. I wonder if his reaction
has anything to do with the alchemy of roasting oolong?

Nigel at Teacraft (at present on vacation in Italy)

Well, bella bella, as the kid says in _Gregory's Girl_, but I hope you
brought your own tea leaves!

/Lew
---
Lew Perin /
http://www.panix.com/~perin/babelcarp.html

I thought theanine is a function of leaf age?

Green tea is made of younger tea shoots, which has higher theanine to
polyphenol ratio ...

This is part of the reason why young leaves are used to make white/
green/yellow tea, because there is less polyphenol to oxidise, and you
will never try to expose the theanine for extended period of time ....
they disappear quickly ...

Japanese green tea is fishy probably because they are steamed made
rather than pan roasted...

I am very curious about Gyokuro. I really wonder how much an authentic
Gyokuro would cost.

Any good recommendation of a reliable source?

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

juliantai writes:

[...theanine and polyphenols...]

Japanese green tea is fishy probably because they are steamed made
rather than pan roasted...

That can't be the reason, because not all Japanese steamed tea is
fishy (though some of it definitely is.)

/Lew
---
Lew Perin /
http://www.panix.com/~perin/babelcarp.html