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