It's called hypogeusia - a diminished acuteness of the sense of taste. Related to this is dysgeusia - impaired or abnormal taste sensation. Although these conditions are caused by disease processes, temporary disturbances in taste can be caused by certain naturally occurring ingredients (by interfering with the normal functioning of taste receptors).
A less commonly used term is parageusia - the most familiar example of which is metallic taste from certain medications. Cacogeusia on the other hand is a hallucination or illusion of unpleasant taste, as seen in epilepsy.
Correction: Cacogeusia is now applied more generically to include real perception of bad taste. Example: the transient cacogeusia resulting from some varieties of pine nuts: http://www.sciencedirect.com/science/article/pii/S0266435612000101
The suggested term astringency is misleading. It is a generic term like numbness, not specific to taste in the mouth, strictly speaking not a sensation and certainly has no connotations of a numb sensation. You have astringent skin lotions for example.