Powdered buttermilk can be used in place of liquid buttermilk in any recipe that calls for buttermilk. The powdered version of buttermilk has a longer shelf life than fresh buttermilk, so a cook can store it in his or her refrigerator without worrying about it spoiling. It is a pasteurized and dried version of milk. Although powdered buttermilk can be used in recipes with little or no taste difference, it usually doesn't taste quite right if a person decides to reconstitute it with water and drink it on its own.
A cook can use powdered buttermilk in a recipe that simply calls for buttermilk by trading the buttermilk for water and adding a quarter of a cup (57 g) of buttermilk powder for every cup (237 ml) of water. For example, if the recipe calls for half a cup (125 ml) of buttermilk, a cook can use half a cup (125 ml) of water and 2 tablespoons (28 g) of powdered buttermilk. Using powdered instead of liquid buttermilk does not change the consistency or texture of the baked good or noticeably affect the taste.
Powdered buttermilk is produced in factories by pasteurizing buttermilk then evaporating the liquid from the milk. The evaporation process concentrates the buttermilk. After the liquid is evaporated, the remaining buttermilk is dried into a powder form using either a roller or a spray drier.
Although powdered buttermilk should be stored in a refrigerator after it has been opened, to give it the longest shelf life, it usually is sold in paper tubs in the baked goods aisle of a grocery store. A person usually will find it near the regular powdered milk and the evaporated and condensed milks. It usually is sold in 12-ounce (340-g) or 1-pound (454-g) packages. In some cases, a person might be able to find it in the bulk section of a grocery store, allowing him or her to purchase only as much powder as is needed.
Liquid buttermilk was traditionally the liquid left after butter was made. Modern liquid buttermilk usually is cultured skim milk, meaning that it has bacteria added to it to provide flavor and thickness. Usually, powdered buttermilks are not cultured but are made in the traditional way, then dried. In that way, buttermilk powder might be more authentic than liquid buttermilk that is available in stores.