buttermilk or plain

Buttermilk is the tangy liquid byproduct traditionally left behind after churning butter from cream, though modern cultured buttermilk is produced by fermenting milk with lactic acid bacteria. Traditional buttermilk, still produced in some artisanal settings, is thin, watery, and slightly acidic with minimal fat content. Contemporary cultured buttermilk, now the standard in most commercial production, is made by introducing Lactococcus lactis and other lactic acid bacteria to regular milk, resulting in a thicker consistency and distinctly sour flavor. The acidity (pH 4.5–4.8) and probiotic cultures define its character and functionality in cooking. Buttermilk contains approximately 0.5–1% fat in traditional versions and 0.5–2% in cultured varieties.

Buttermilk is primarily used as a leavening agent and tenderizer in baking, where its acidity reacts with baking soda to create lift in pancakes, biscuits, cakes, and quick breads. In savory cooking, it features prominently in marinades for fried chicken and other proteins, where the acid and enzymes help tenderize meat while imparting subtle tang. It is also used in salad dressings, particularly ranch-style dressings, and in batters for frying. In Southern and Irish cuisines, buttermilk pancakes and soda bread are classic applications. The acidic nature makes it particularly valuable in recipes where chemical leavening is needed without yeast fermentation.