Buttermilk is the milky liquid remaining after cream has been churned to make butter. Sweet natural buttermilk comes from fresh cream that has been chilled and churned. Sour natural buttermilk comes from cream ripened (soured) by adding lactic-acid-producing bacteria, called a starter. Natural buttermilk does not keep well as a fresh beverage. But sweet natural buttermilk is sometimes dried into a powder and used commercially in cooking, baking, and making ice cream.
Cultured buttermilk is made by adding a starter to pasteurized skim milk and allowing it to sour until it curdles. Cultured buttermilk is a popular beverage. It should be kept chilled in a closed container because the beverage absorbs mold, yeast, and bacteria if exposed to air.
Most kinds of buttermilk have about the same food value as milk. However, buttermilk contains less fat and fat-soluble vitamins than milk does.
See also Butter ; Lactic acid ; Milk .
