Yes, you can make a buttermilk substitute using skim milk. Traditional buttermilk is the liquid remaining after churning butter from cream. The product most commonly sold commercially is cultured buttermilk, created by adding a bacteria culture to pasteurized milk. When a recipe calls for buttermilk, it is usually the acidity that is sought, and the homemade skim milk version successfully provides this acid. The resulting product is technically an acidified milk, not true cultured buttermilk, but it serves as a low-fat option when commercial buttermilk is unavailable.
The Homemade Skim Milk Buttermilk Method
To create this substitute, combine skim milk with an acid, initiating a chemical reaction that curds the milk proteins. To make one cup, place one tablespoon of acid into a liquid measuring cup. The two most common choices are fresh lemon juice or distilled white vinegar.
Next, pour the cold skim milk into the measuring cup until the liquid reaches the one-cup line, then gently stir the mixture. The acid causes the casein proteins in the milk to coagulate. Allow the mixture to sit undisturbed at room temperature for approximately five to ten minutes, allowing the milk to thicken slightly. The slightly curdled appearance indicates the substitute is ready to be used in your recipe.
How Skim Milk Buttermilk Performs in Baking
The primary function of buttermilk in baking is its acidity. When the acidic buttermilk is combined with a chemical leavening agent, such as baking soda, it triggers an acid-base reaction. This reaction releases carbon dioxide gas, providing a significant boost in leavening power for baked goods.
The acid also conditions the flour, which limits gluten development and results in a more tender crumb structure. The homemade skim milk version will be thinner than the cultured, store-bought buttermilk. Furthermore, the lack of milk fat in skim milk (less than 0.5%) means the final product will be leaner than recipes made with whole-milk buttermilk.
Fat is a natural tenderizer and flavor carrier, so the use of skim milk may result in a final baked item that is slightly less rich and potentially firmer or drier than one made with a full-fat dairy product. While the substitute works well for leavening, the flavor profile of the raw mixture is sharper and more acidic than commercially cultured buttermilk. However, this tanginess is usually neutralized during the baking process.