buttermilk -or-

Buttermilk is the liquid byproduct remaining after butter is churned from cream, though most commercial buttermilk today is cultured milk produced by adding lactic acid bacteria (typically Lactococcus lactis) to pasteurized low-fat or skim milk. Traditionally, buttermilk was slightly sour and carried some residual butterfat; modern cultured buttermilk is tangy, acidic (pH around 4.5), and contains minimal fat. The fermentation process gives it a distinctive tart flavor and thicker consistency than regular milk, with a white to pale yellow appearance.

Buttermilk varies regionally: in some parts of Europe and South Asia, it refers to the thin, watery liquid from traditional butter-making, while contemporary commercial buttermilk is a controlled fermented product with consistent acidity and texture.

Buttermilk serves as a leavening agent and flavor component in baking, where its acidity reacts with baking soda to produce carbon dioxide and create tender, fluffy baked goods such as biscuits, pancakes, waffles, and cakes. Its tangy flavor enhances salad dressings, marinades, and sauces, particularly in Southern and Southern Asian cuisines. In marinating, the acidity tenderizes meat proteins while adding subtle flavor. Buttermilk is also consumed as a beverage, particularly in South Asian, Middle Eastern, and Scandinavian cuisines, often seasoned with spices, herbs, or salt. Its acidity makes it useful for curdling in cheese-making and for tempering in various preparations.