Pu-erh tea

„This process was first developed in 1972 by Menghai Tea Factory and Kunming Tea Factory] to imitate the flavor and colour of aged raw pu-erh, and was an adaptation of wet storage techniques being used by merchants to falsify the age of their teas. Mass production of ripened pu'er began in 1975. It can be consumed without further aging, though it can also be stored to "air out" some of the less savoury flavors and aromas acquired during fermentation.“

„Astringency
Astringency invariably accompanies bitterness. In some Puer the astringency is more pronounced, the bitterness slightly weaker. A benefit of astringency is that it can help promote salivation. If this is felt on the underside of the the tongue it is a further mark of good tea.“