Buttermilk

Buttermilk does not contain butter as the name implies, but refers to the liquid remaining after churning. Traditionally, the liquid was strained and left to ferment, giving it a thicker texture and slightly sour taste. It was in fact much lower in fat than other milks. Commercial buttermilk is made by adding lactic acid bacteria to 1 percent or skim milk that is left to ferment at a low temperature for 12 to 14 hours. This is called cultured buttermilk and is sold salted or unsalted.