Pu-erh tea

„Bĭng: The tea cake itself. Tea cakes or other compressed pu'er can be made up of two or more grades of tea, typically with higher grade leaves on the outside of the cake and lower grades or broken leaves in the center. This is done to improve the appearance of the tea cake and improve its sale. Predicting the grade of tea used on the inside takes some effort and experience in selection. However, the area in and around the dimple of the tea cake can sometimes reveal the quality of the inner leaves.“

„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.“