Buttermilk is the name given to the liquid that remains after the churning process that extracts butter from cream. As such, despite its name, it does not actually contain any butter. Buttermilk has a tarter taste than regular milk due to the increased amount of lactic acid present due to bacteria fermenting the natural sugars in the milk. In the industrial production of buttermilk, these bacteria are added, but it is easy to make a buttermilk substitute at home.
Things You'll Need
Place the white vinegar or lemon juice into a measuring jug.
Pour the milk into the same measuring jug until the mixture reaches the 1 cup marking.
Stir the mixture so that the vinegar or lemon juice is well distributed through the milk.
Allow the mixture to stand, unstirred, for five minutes.
Use the amount of buttermilk required by your recipe.
If you do not require a whole cup of buttermilk in your recipe, you can keep the remainder for up to a week in the fridge, as long as it is kept in an airtight container.
References and ResourcesAll Recipes: Common Ingredient Substitutions
Good Housekeeping: Buttermilk
New York Times: Got Buttermilk?