Buttermilk refers to a number of dairy drinks. Originally, buttermilk was the liquid left behind after churning butter out of cream. It also refers to a range of fermented milk drinks, common in warm climates (for example, India, or the Southern USA) where fresh milk would otherwise sour quickly. Whether traditional or cultured, the tartness of buttermilk's due to the presence of acid in the milk. The increased acidity's primarily due to lactic acid, a by-product naturally produced by lactic a… (More on Buttermilk)