Buttermilk is a fermented dairy drink that is made by adding lactic acid bacteria to milk, causing it to ferment and thicken. Traditionally, buttermilk was the liquid that remained after butter was churned from cream. However, modern-day buttermilk is usually made by adding cultures to pasteurized milk.
Buttermilk is tangy and slightly acidic in taste, and is often used as an ingredient in baking, as well as in marinades and dressings. It is a common ingredient in Southern cuisine, where it is used to make biscuits, cornbread, and fried chicken.
Buttermilk is also a good source of calcium, potassium, and vitamin B12, and is lower in fat than whole milk. Low-fat and non-fat versions of buttermilk are also available for those who are watching their fat intake.