Source : Webster's Revised Unabridged Dictionary (1913)

Acidulate \A*cid"u*late\, v. t. [imp. & p. p. {Acidulated}; p.
   pr. & vb. n. {Acidulating}.] [Cf. F. aciduler. See
   {Acidulous}.]
   To make sour or acid in a moderate degree; to sour somewhat.
   --Arbuthnot.

Source : WordNet®

acidulated
     adj : made slightly acid