What dairy product is used to make Southern buttermilk biscuits?

Southern buttermilk biscuits are made with buttermilk. The ingredient gives the dough a lightly tangy flavor and helps create the tender, layered texture associated with this style of biscuit.

Modern cultured buttermilk is milk fermented with lactic-acid-producing bacteria. Its acidity reacts with baking soda or baking powder, producing carbon dioxide bubbles that help the biscuits rise. The liquid also adds moisture without requiring much kneading.

The name can cause confusion because traditional buttermilk was the thin liquid left after churning butter from cultured cream. Most buttermilk sold today is made by culturing fresh pasteurized milk, so it is thicker and more consistent for baking. Plain milk, cream, or yogurt may appear in other biscuit recipes, but they are not the canonical ingredient in this question.

Southern biscuits differ from many rolled breads because cooks generally try to handle the dough as little as possible. Overworking it can develop gluten and make the finished biscuits tough rather than soft and flaky.