edulcorate: to sweeten or to free from harshness. It has also been adopted in the digital world to refer to the elimination of unnecessary or redundant data from a database. In chemistry, it can more specifically mean “to free from acids, salts, or other soluble substances by washing." Edulcorate and dulcet share the common etymological ancestor dulcis, meaning "sweet."
Here’s an actual use of the word from the Repertory of Patent Inventions, which Google Books says is from 1814: "...it is only necessary to add to the wine the vegetables and aroma’s [sic] that are deemed necessary to edulcorate it suitably, or to leave it dry..."
And a contrived use: "We had hoped that the electroshock therapy would edulcorate Rita’s personality, but after a week of treatements, she was as curmudgeonly as ever. And now she twitched all the time."