The Collaborative International Dictionary of English v.0.48:

Piquancy \Pi"quan*cy\, n. [See Piquant.]
   The quality or state of being piquant.
   [1913 Webster]

WordNet (r) 3.0 (2006):

piquancy
    n 1: a tart spicy quality [syn: nip, piquance, piquancy,
         piquantness, tang, tanginess, zest]
    2: the quality of being agreeably stimulating or mentally
       exciting [syn: piquancy, piquance, piquantness]