Buttermilk originally was produced as a by-product of butter churning. After the fat molecules in cream separate and amass to form butter the liquid remaining is buttermilk. Buttermilk can also be produced through adding a culture to pasteurized milk.
Homemade buttermilk from scratch is made by the same process as yogurt, requiring a starter culture. The fermentation of the milk by a starter bacteria is how buttermilk is formed, turning the milk sugar into lactic acid.
Using Buttermilk as a Starter
Add 8 ounces buttermilk to a one-quart Mason jar. Add 4-cups fresh whole milk. Close the lid and shake to mix. Let it sit until it has clabbered (thickened or curdled)-generally twenty-four hours. If after two days it hasn’t clabbered, the starter likely wasn’t active.
Using Milk as a Starter
If you don’t already have an active culture from buttermilk, you can make your own. For this to work you will need to use fresh raw milk, which means it has not been pasteurized. Be aware that the FDA warns that raw milk can pose a serious health risk.
Let 1-cup fresh raw milk sit at room temperature for several days until it clabbers. Use ¼ cup of this newly clabbered milk and add a cup of fresh milk. Let it sit until it clabbers. Continue this procedure until the mixture reliably clabbers in twenty-four hours. Once it does, this mixture can be used confidently as a starter for larger batches.
A Word on Starter Cultures
In order for buttermilk to work as a bacterial starter, it must contain active cultures. The fresher the buttermilk is, the more active the culture will be. If you are in doubt, add more culture to your milk.
Though the acidity in buttermilk provides it with a longer refrigerator shelf life as compared to whole milk, don’t use it as a starter if it is older than three-four weeks old.
If you have started a recipe and realized that it calls for buttermilk that you don’t have, you can use a few ingredients in a pinch. The following buttermilk substitutions will produce one-cup.
- 1-cup plain yogurt
- 1-cup sour cream
- 1-cup milk plus 1 ½ tsp. cream of tartar
- 1-cup water plus ¼ cup powdered buttermilk
- 1-c milk plus 1 tbsp. white or cider vinegar (allow to ferment for 5-10 minutes)
- 1-cup milk plus 1 tbsp. lemon juice (allow to ferment for 5-10 minutes)