I noticed a weird quality in a couple of teas I've had recently. There seems to be a very noticeable black pepper aftertaste that is kind of unpleasant and remains on the tongue for several minutes. I've noticed it with both a Vietnamese green (Che Xanh) and a green puerh in my collection, and they were both teas that have been sitting around for close to a year in paper bags. Can't remember if I noticed this pepper taste when they were new; could it be caused by poor aging?
Other than being a bit dry, there's not noticeable damage to the leaves and no visible mold or other contaminants.