I've just popped back to this thread, so forgive me if the subject has already been discussed.
I'm referring to tannins in tea. Tea is very rich in tannins, like tannic acid. As some of you may be aware, tannins cross-link proteins to create a rigid structure.
The relevance of this lies in the leather industry. They make leather from animal skins by 'tanning' them with cross-linking agents. What was a nice flexible, supple proteinaceous substance becomes stiff, tough, and leathery suitable for making into shoes, horse saddles and footballs.
So, should any of you avid tea takers become aware of a slight stiffening of the tongue, a barely perceptible change in the tone of your voice, think about leather and what could possibly be happening within you very own mouth.
I don't wish to scare anyone, but I feel you should be aware of these facts.
Cheers,
JaX
PS: Coffee anyone?