The term 'make sour' can be expressed in a variety of ways. Acetify (7 letters) means to make something sour by adding vinegar or acetic acid. TURN (4 letters) is a verb meaning to change the direction, course, or character of something. ACERBATE (8 letters) means to make something sour or bitter. Acidify (7 letters) means to make something sour or acidic. EMBITTER (8 letters) means to make something sour or bitter. All of these terms refer to making something sour or bitter in some way.