The Collaborative International Dictionary of English v.0.48:

pectic \pec"tic\ (p[e^]k"t[i^]k), a. [Gr. phkto`s curdled.]
   (Chem.)
   Of or pertaining to pectin; specifically, designating an acid
   obtained from ordinary vegetable jelly (pectin) as an
   amorphous substance, tough and horny when dry, but gelatinous
   when moist.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pectic
    adj 1: of or relating to or derived from pectin; "pectic acid"