soured

(verb) go sour or spoil. Synonyms: sour, turn, ferment, work. Examples: "The milk has soured." "The wine worked." "The cream has turned--we have to throw it out."

(verb) make sour or more sour. Synonyms: sour, acidify, acidulate, acetify.

(adj) having turned bad. Synonyms: soured (vs. unsoured).