acidulate

v. make slightly acidic; embitter, make sour

Verb
1. make sour or more sour
(synonym) sour, acidify, acetify
(hypernym) change taste
(derivation) acid

v. acidulate, make slightly acidic, embitter

(v. t.)
To make sour or acid in a moderate degree; to sour somewhat.
  

To give a dish or liquid a slightly acidic, tart or piquant taste by adding some lemon juice, vinegar, or unripened fruit juice. Also, one can acidulate fresh cream by adding lemon juice to get sour cream.