When substituting regular milk for buttermilk in a recipe, what should be added to achieve similar acidity?

When substituting regular milk for buttermilk, adding lemon juice helps to create the acidity characteristic of buttermilk. Buttermilk is naturally acidic, which not only contributes to the flavor but also affects how baking recipes react with leavening agents, such as baking soda. The acidity from the lemon juice mimics the tangy taste and the chemical properties of buttermilk, allowing for the same leavening effects and flavor profile in the final product.

For example, when baking, the acid in buttermilk interacts with baking soda to produce carbon dioxide bubbles, which help the dough rise. By adding lemon juice to regular milk, you can replicate this acidity and achieve a similar texture and taste in your baked goods. Other options mentioned do not provide the same acidifying effect; salt does not increase acidity, cake flour has a different purpose in baking, and baking soda is already part of the leavening system and would not provide acidity on its own. Adding lemon juice is the correct solution to creating an appropriate substitute for buttermilk.