When substituting buttermilk for whole milk in pastries, what adjustment should be made?

When substituting buttermilk for whole milk in pastries, one important adjustment to make is to increase the baking soda. Buttermilk is an acidic ingredient, while whole milk is neutral. The acidity of buttermilk can react with baking soda to produce carbon dioxide, which helps the pastry rise. This reaction contributes to a lighter and fluffier texture in baked goods.

If buttermilk is used instead of whole milk, the addition of more baking soda is necessary to compensate for its acidity, ensuring that the desired leavening effect occurs. This adjustment helps to maintain the balance of leavening agents in the recipe, ultimately resulting in a better final product.